Knee Arthroplasty (updated)

Question 1

Describe the 4th generation cementing technique

Answer 1

1. Vacuum mixing cement (reduces porosity, increases fatigue strength)
2. Medullary plug/cement restrictor (limits the cement column)
3. Clean dry bone (increases cement interdigitation)
4. Retrograde insertion of cement (reduces blood lamination)
5. Cement pressurization (increases cement interdigitation)
6. Prosthesis centralizers (even cement mantle)

Question 2

overall patient satisfaction following TKA

Answer 2

4 out of 5 patients are satisfied overall

Question 3

predictors of patient satisfaction and dissatisfaction after TKA

Answer 3

most commonly reported predictors of satisfaction include
* higher overall postop function
* greater improvement in funciton from pre-op to post-op levels
* decreased pain
* fulfillment of expectations

most commonly reported predictors of dissatisfaction
* persistent pain after surgery
* anxiety, depression, poorer mental health as measured by clinical diagnosis or pre-op questionnaires

Question 4

how long does a knee replacement last

Answer 4

82% of TKAs and 70% of UKA last 25 years in paients with OA

Question 5

what are the common measurements in TKA planning

Answer 5

1. Mechanical axis of the limb
   * Line from the centre of the femoral head to the centre of the ankle joint
2. Anatomical axis of the femur
   * Line that bisects the femur medullary canal
3. Mechanical axis of the femur
   * Line from the centre of the femoral head to the intersection of the anatomical axis and the intercondylar notch
4. Distal femoral cut angle

• 5-7 degrees of valgus
• Difference between the mechanical and anatomical axis

5. Anatomical axis of the tibia
   * Line that bisects the tibia medullary canal
6. Mechanical axis of the tibia
   * Line from the centre of the proximal tibia to the centre of the ankle
7. Proximal tibial cut angle

• 0 degrees of varus/valgus
• 90 degrees to the mechanical axis of the tibia

8. Normal tibial slope = 10+/-3 degrees
9. Normal tibia plateau relative to the mechanical axis = 87° of varus (MPTA)
10. Normal distal femur relative to the anatomical axis = 81° of valgus (aLDFA)
11. Normal distal femur relative to the mechanical axis = 87° of valgus (mLDFA)
12. Posterior condylar axis

• Line connecting the apex of the posterior aspect of the medial and lateral femoral condyles with the knee in flexion
• 3 degrees internally rotated relative to the transepicondylar axis

13. Whitesides line
    * Line extending from the deepest point of the femoral trochlea to the centre of the intercondylar notch
14. Transepicondylar axis
    * *Line extending between the medial and lateral epicondyles
15. Q angle

• Angle formed between a line drawn from the ASIS to the centre of the patella and a line from the centre of the patella to the tibial tubercle
• Females = 18, males = 14

16.Tibiofemoral angle

• Angle formed between the anatomical axis of the femur and tibia
• Normal = ~6 degrees

17. hip knee angle
    * angle formed by the mechanical femoral axis and mechanical tibial axis

Question 6

What are the technical goals in TKA?

Answer 6

1. Restore neutral mechanical alignment of limb
2. Restore joint line
3. Balance ligaments
4. Well tracking patella

Question 7

definition of constitutional varus alignment knee

Answer 7

constitutional varus = varus knee alignment that persists at skeletal maturity
* varus - hip knee angkle measuring 3 degrees or more
* present in 32% of males and 17% of females

Question 8

What is the difference between mechanical alignment and kinematic alignment?

Answer 8

1.Mechanical alignment

• A. Avoids tibia cut in anatomical varus (3°)
• B. Tibia cut is perpendicular to the mechanical axis (90° to the anatomical axis)
• C. Femoral cut is perpendicular to the mechanical axis (4-6° valgus to the anatomical axis)

2.Kinematic alignment

• A. AKA: Anatomic alignment, constitutional alignment
• B. Compared to mechanical alignment
  
  • Femoral cuts are in 2-4° more valgus
  • Tibial cuts are in 2-4° more varus

Question 9

What is the difference between measured resection vs. gap balancing?

Answer 9

1.Measured resection

• A. Relies on transepicondylar axis, Whitesides line, posterior condylar axis
• B. Utilizes anterior or posterior referencing guides
  
  • Anterior referencing avoids notching but can lead to overresection of posterior condyles increasing the flexion gap
  • Posterior referencing can lead to anterior notching
• C. Disadvantage = variable femoral anatomy
  
  • E.g. hypoplastic lateral femoral condyle

2.Gap balancing

• A. Relies on a precise tibial cut 90° to the mechanical axis
  
  • The gaps are then balanced by removing osteophytes and tension is held with distraction devices
  • Femoral cuts are made parallel to the tibial cut in flexion and extension

Question 10

Pros/Cons/contraindications of cruiciate retaining knee

Answer 10

• Cruciate retaining (CR)
  
  • PROS
    
    • Bone conserving
    • More consistent joint line restoration (small flexion gap)
    • More proprioceptive feedback with PCL
    • improved kinematics
    • less stress at bone-cement interface
  • CONS
    
    • Harder to balance in severe deformities
    • Tight PCL in flexion causes PE wear
    • Late rupture/stretch of PCL leading to instability
    • Sliding PE wear due to paradoxical forward sliding
    • CONTRAINDICATIONS
      
      • pcl insufficency
      • PL instability (corner injury) - results in excessive PCL strain
      • significant coronal deformity
      • inflammatory arthritis
      • extensor mechanism deficiency
      • severe fixed flesion contracture (>20)
      • past hx of trauma or surgery (difficult soft tissue balancing)
      • excessive preop tibial slope

Question 11

key surgical pearls of performing CR TKA

Answer 11

• avoid over resection of the distal femur (CR is tighter in flexion compared to PS)
• avoid iatrogenic PCL injury with saw blade
• opt for a smaller femoral component (avoids excessive PCL tension)
• ensure adequate tibial slope (reduces PCL tension and facilitates flexion)
  
  • small adjusements in tibial slope more efficiently fine-tunes the flexion gap compared to PS TKA

Question 12

types and pros/cons/indications of cruciate sacrificing knee

Answer 12

• Cruciate sacrificing
  • Posterior stabilized = polyethylene post and cam
    
    • Indications:
      
      • PCL deficient knee, patellectomy, inflammatory arthritis
  • PROS
    
    • Easier to balance soft tissues
    • better knee flexion (compare to CR)
    • more predictable kinematics and rollback
  • CONS
    
    • Femoral cam jump
    • Patella clunk syndrome
    • Tibial post wear and breakage
    • Not bone conserving (intercondylar notch punch removes more bone)
    • Larger flexion gap (leads to elevation of joint line due to larger distal femoral resection)
  • oAnterior stabilized = extended anterior PE lip

Question 13

what is the effect on the flexion gap when PCL is resected

Answer 13

flexion gap increases (3mm)

Question 14

pros/cons for constrained knee

Answer 14

2. Constrained

• Constrained non-hinged (high tibial post) [aka. varus valgus constrained, condylar constrained]
  
  • CONS
    
    • Increased polyethylene wear
    • Higher rate of aseptic loosening (greater forces through implant-bone interface)
    • not bone conserving
    • risk of post fracture or failure
  • PROS
    
    • Substitutes for MCL or LCL deficiency

Question 15

indications and disavantages of hinged knee

Answer 15

3. Most constrained

• Hinged with rotating tibial platform
  
  • Indications [CORR 2010 May; 468(5): 1248–1253]
    
    • Global ligamentous instability
    • Severe deformity (with associated soft tissue releases)
    • Severe bone loss (with loss of ligamentous attachments)
    • Gross flexion extension imbalances/mismatch
    • Hyperextension instability (eg. polio)
    • Limb salvage surgery in oncology
    • Comminuted or nonunited distal femur fracture in elderly
    • Ankylosis with instability following releases
  • disadvantages
    
    • not bone conserving
    • risk of aseptic looosening (greater forces thorugh implant-bone interface)

Question 16

What are the advantages/disadvantages of using a subvastus approach to the knee?

Answer 16

1. Advantages

• earlier return of straight leg raise (1.7 days)
• lower VAS pain scores on POD 1 (0.8 pt difference)
• improved ROM at POD 7 (7°)
• less lateral release required
• reduced periop blood loss

2. disadvantages
   * longer total operative time (10 min)
   * longer tourniquet time
   *
3. notes
   * no functional difference at 6 wks or one year
   * no difference in adverse events

Question 17

what are the advantagaes and disadvantages of midvastus approach compared to medial parapatellar approach

Answer 17

1. advantages
   * lower VAS pain scores at POD 14 (butt no difference at POD3, week 6, month 3 or month 6)
   * improved ROM at POD 14
2. disadvantages
   * longer total operative time
3. notes
   * no functional difference at 6 wks, 3/6 month or 1 year
   * no difference in lateral retinacular release, blood loss, straight leg raise hospital stay and postop complications

Question 18

what are the relative contraindications of subvastus/midvastus approaches

Answer 18

obesity, preop stiffness, previous HTO, revision TKA, extremely muscular quads, patella baja

Question 19

advantages and disadvantages of uncemented TKA implants

Answer 19

advantages
- shorter OR time
* no time required for cement prep, implantation and curing
* may reduce risk of infection
- bone prserving
- easier to revise
- no risk of third body wear from retained cement

disadvantages
- technically demainding (precise bone cuts)
- risk of early migration of tibial components
- more expensive

Question 20

advantages and disadvantages of cemented TKA implants

Answer 20

1. advantages
   - stable upon implantation
   - less technically demainding
   - allows for antibiotic delivery
   - less costly
   - adjustements in gap balancing can be made
2. disadvantages
   - longer OR time
   - potential third body wear from retained cement

Question 21

What is the consequence of a flexion contracture post-TKA?

[JBJS(B) 2012;94-B, Supple A:112–15]

Answer 21

1. Increased energy expenditure as a result of quadriceps activity to prevent knee buckling
2. Relative LLD
   * Shortens stride length, increases contralateral knee forces, alters trunk alignment

Question 22

What is the intraop management of flexion contractures in TKA?

[JBJS(B) 2012;94-B, Supple A:112–15]

Answer 22

1. Remove posterior osteophytes
2. Release posterior capsule (off femur and tibia)
3. Additional distal femoral resection
   * Generally, take an additional 2mm for flexion contractures >10°
4. Decrease tibial slope
5. Avoid implanting components in flexion
6. PS knee preferred
7. PCL recession in CR knees
   * Release from posterior tibia, medial femoral condyle or V-shaped osteotomy of the posterior tibia
8. Release medial and lateral gastrocnemius
9. Post operative splinting, CPM, shoe lift on contralateral side (forces extension), exercises, close followup

Question 23

What are causes of patellar maltracking in TKA?

[JAAOS 2016;24: 220-230]

Answer 23

1. Internally rotated femoral component
2. Medialized femoral component
3. Internally rotated tibial component
4. Medialized tibial component
5. Lateralized patellar button
6. Valgus deformity (must restore neutral mechanical axis)
   * I.e. >7° valgus positioning of the femoral component
7. Overstuffing patellofemoral joint
   * I.e. Increased net patella thickness (increases tension on lateral retinaculum thereby increasing lateral patellar pull)
8. Asymmetric patellar resection

Question 24

What are the intraop treatment options for patellar maltracking in TKA?

Answer 24

1. Take down tourniqette to confirm maltracking

• “No thumb” test – patella should track with its medial edge in contact with the medial femoral component with the medial capsule open throughout the range without the surgeon keeping it in position
• “Kissing rule” – in maximal flexion the medial surface of the patella should make contact with the medial condyle of the femoral component

2. Lateral release
3. Medial plication
4. Tibial tubercle osteotomy
5. Quadsplasty
6. Component revision

Question 25

What is the technique for performing a lateral release of the patella?

Answer 25

1. Option 1 [Clin Orthop Relat Res (2012) 470:2854–2863]

• Progress to the next step only if needed
• Step 3 sacrifices the superior lateral geniculate artery
• STEPS:
  
  • Step 1 - Release of distal part
    
    • Release of the lateral retinaculum starting from the midlevel of the patella, progressing distally to the upper tibial border
  • Step 2 - Partial release of proximal part
    
    • Release of the lateral retinaculum starting from midlevel of the patella, progressing proximally up to the proximal border of the patella;
    • The lateral superior genicular artery is preserved
  • Step 3 - Complete release of proximal part
    
    • Further release of the retinaculum from the superior border of the patella, progressing proximally, lateral to the vastus lateralis, for approximately 2 to 4 cm
    • This includes release of the superior geniculate artery
      2. Option 2 [The Journal of Arthroplasty Vol. 24 No. 5 2009]
• Progress to the next stage only if needed
• Release of the lateral patellofemoral ligament from within the joint
• Outside staged retinacular release preserving the deep capsulosynovial layer
• STEPS:
  
  • Stage 1 - Release of the LPFL from the deep aspect
  • Stage 2 - Release of the lateral retinaculum starts 25 mm proximal to the patella, down to the level of the superior border of the patella, and 20 mm lateral to it
  • Stage 3 - Release of the lateral retinaculum down to the level of the midpatella
  • Stage 4 - Release of the lateral retinaculum down to the distal pole of the patella
  • Stage 5 - Lateral release from the inferior border of the patella to the level of the knee joint line
  • Stage 6 - Lateral release down to the level of the Gerdy tubercle

Question 26

How do you assess patellar height?

Answer 26

1. Blumensaat’s line
   * Should extend to the inferior pole of the patella in 30 degrees of flexion
2. Insall-Salvati Method/Ratio/Index

• Ratio of the length of patellar tendon to the length of the patella (ideally in 30 degrees of knee flexion)
• Normal = 0.8-1.2
• Patella baja = <0.8
• Patella alta = >1.2

3. Caton Deschamps method

• Defined by the ratio between the articular facet length of the patella and the distance between the inferior articular facet of the patella and the anterior corner of the superior tibial epiphysis
• Normal = 0.6-1.3

4. Blackburne-Peel method

• Ratio between a line drawn from the inferior articular facet of the patella to a horizontal parallel to the tibial plateau and the patellar articular facet length
• Normal = 0.8-1.0

Question 27

clinical consequence of patella baja

Answer 27

• patella is in constant contact with the trochlea from flexion to extension (in contrast to the normal patella which does not engage trochlea in full extension)
• results in anterior knee pain, decreased ROM, extensor lag

Question 28

What is the treatment of patella baja in TKA?

Answer 28

1. Lower joint line
   * Resect more tibia, resect less distal femur (or augment)
2. Place patella poly superiorly and trim distal patellar pole
3. Tibial tubercle osteotomy moving it cephalad
4. Patellectomy

Question 29

What are causes of patella baja?

Answer 29

congenital
aquired
- previous surgery: HTO, TTO, ACLR, knee arthroscopy, retrograde femoral nail, arthroplasty (raising joint line in TKA)
- Trauma (scarring)

Question 30

mechanism by which patella baja develops

Answer 30

1. permanent shortening of patellar tendon secondary to inflammatory, ischemic or traumatic events assocaited with quad weakness, inhibition or immobilization allowing progressive decent of the patella
2. joint line elevation associated with TKA and opening wedge HTO
3. acute patella baja can result from patella fracture or quad tendon injury

Question 31

what is pseudopatella baja and how to differentiate from true patella baja

Answer 31

1. true patella baja - patellar tendon length shorter than normal
   * both modified insall salvati ratio and blackburne peel ratio will be anormally low
2. pseudopatella baja - narrowing of the distance between the distal pole of the patella and the articular surface of the tibia without shortening of the patella tendon
   * insall-salvati ratio will be normal, blackburne peel ratio will be low
   * occurs secondary to joint line elevation in TKA by 3 means
   
   • elevating femoral joint line (excessive distal femoral cut, and consequently posterior femoral cut to acheive equal balance)
   • elevating tibial joint line (under-resecting the tibial cut and replacing it with the tibial baseplate and isnert that is thicker than the resected bone )
   • excessive soft-tissue release necessitating elevation of the tibiofemoral joint line to provide stability

Question 32

what treatment options have been described to address true batella baja and pseudopatella baja following TKA

Answer 32

1. patellar tendon z-plasty lengthening - only indicated in true patella baja
2. proximalizing TTO
3. anterior tibial poly burring - allows the patella to sit in anterior recess, prevening impingement of the patella
4. reivsion of patellar componsent from inferior to superior position
5. revision TKA to distalize joint line
   
   • may require distal and posterior femoral augments and downsizing tibia (thinner poly or more tibial resection)
   • only indicated in pseudopatella baja

Question 33

A valgus knee is generally defined as a tibiofemoral angle greater than what?

Answer 33

Tibiofemoral angle >10 degrees

Question 34

Which approach is most commonly used in a valgus TKA?

Answer 34

• Medial parapatellar approach is sufficient in most cases
• Lateral parapatellar approach is described:
  
  • Pros:
    
    • Direct access to lateral structures
    • No disruption of medial patella blood supply
  • Cons:
    
    • Limits access to central and medial structures
    • Lack of soft tissue for closure

Question 35

classification of valgus knee

Answer 35

Ranawat classification
- type I <10°, minimal coronal plane valgus with medial soft tissue stretching
- type II 10-20° fixed coronal deformity greater than 10° with attenuated medial soft tissues
- type III >20° severe bony deformity with incompoetent medial soft tissues and a previous osteotomy

mullaji and shetty classification
type I - correctible valgus deformity with no fixed deformit and an intact mcl
type II - fixed valgus deformity, intact MCL
type III - valgus and hyperextension deformity with intact MCL
type IV - valgus and fixed flesion deformity with intact MCL
type V - severe valgus deformity with an incompotent MCL
type VI - valgus secondary to extra-artic deformity

Question 36

What are 3 factors to consider in valgus TKA and ways to address them?

Answer 36

1. Contracted lateral soft tissue structures

• Structures that may require release:
  
  • Lateral osteophytes (may bowstring lateral structures)
  • Posterolateral capsule and arcuate ligament (extends from fibula head to posterolateral capsule)
  • Iliotibial band [release mainly affects extension gap]
  • Popliteus tendon [release mainly affects flexion gap]
  • LCL
  • Lateral head of gastrocnemius
  • Biceps femoris tendon (rare to release)
  • PCL if tight laterally in flexion
• Typically sufficient release is achieved with release of posterolateral capsule and ‘pie-crusting’ of lateral structures
• More severe deformities may require release of LCL and popliteus from lateral epicondyle and lateral head of gastroc from femoral insertion

2. Lax medial structures
   * Tightening medial structures is usually achieved by ‘filling up’ the medial side (requires thicker poly) and release of lateral structures
   * Occasionally the MCL is tightened by MCL advancement, MCL division and imbrication or recessing the origin of the MCL with a bone block
3. Lateral bone loss
   * Hypoplastic or deficient lateral femoral condyle may require augments - will have a tendency to cause femoral component IR if using posterior referencing
   * Lateral tibial bone loss can be addressed by increasing the cement mantle or resecting more tibia to allow rim contact

Question 37

What are 3 factors to consider in a varus knee and how to correct them?

Answer 37

1. Contracted medial soft tissue structures

• Structures that may require release
  
  • Osteophytes (cause bowstringing of medial soft tissue)
  • Capsule
  • Superficial MCL
    
    • Release of anterior fibres mainly affects flexion gap
    • Release of posterior fibres mainly affects extension gap
  • Posterior oblique ligament fibres of MCL
    
    • Release affects mainly extension gap
  • Semimembranosus
    
    • Release affects mainly extension gap
  • Pes anserinus
    
    • Release affects mainly extension gap
  • PCL
    
    • Release affects mainly the flexion gap
• Consider resection bone from the medial aspect of the medial tibial plateau and lateralizing the tibial component

2. Lax lateral structures
   * Tightening lateral structures is usually achieved by ‘filling up’ the lateral side (requires thicker poly) and release of medial structures
   * Occasionally the LCL is tightened by LCL advancement
3. Medial bone loss
   * Consider augments, cement, allogaft bone/synthetic

Question 38

what is a reduction osteotomy and when should it be used

Answer 38

1. reduction osteotomy - removal of posteromedial tibial bony flare which removes the tenting effect on the medial soft tissue structures thereby addressing the contracted medial structures
2. technique
   - place a tibial tray so that it is flush with the lateral tibial plateau leaving posteromedial bone uncovered
   - measure the amount of bone uncovered to determine the amount of resection
   - in general, 2mm resection = 1° of resection - especially trrue for deformities <15°

• should not be performed if the deformity is correctable
• should preced soft tissue releases

Question 39

what are the indications and contraindications for patellofemoral arthroplasty

Answer 39

1. indications
   
   • isolated PF OA
   • severe symptoms affectins ADLs that are nonresponsive to nonop management
2. contraindications
   
   • TF arthritis
   • uncorrected PF malalignment or instability
   • TF malalignment inflammatory arthritis
   • BMI >30
   • fixed flexion contracture >10
   • patella baja

Question 40

who is the ideal candidate for PF arthroplasty

Answer 40

nonobse patient younger than 65 years of age wit isolated noninflammatory PF arthritis and severe symptoms unresponsive to nonop management

Question 41

advantages of a patellofemoral arthroplasty compared to TKA

Answer 41

1. improved knee kinematics
2. improved proprioception
3. reduce blood loss
4. shorter operative times
5. faster rehab
6. better ROM
7. less pain

Question 42

how does PF revision to TKA compare to primary TKa and revision TKA

Answer 42

clinical outcomes comparable to primary TKA and superior to revision TKA

Question 43

what are causes of PF arthroplasty failure

Answer 43

OA progression (38%), pain (16%), aseptic loosening (15%), and patellar maltracking (14%)

Question 44

What are the indications for high tibial osteotomy?

Answer 44

1. Pain located primarily on the medial aspect of the knee
2. Medial compartment OA (less than 4mm of medial joint space on standing radiograph)
3. Varus knee deformity
4. Young patient undergoing articular cartilage restoration or medial meniscus transplant

Question 45

What are the contraindications for HTO?

Answer 45

1. Less than 90 degrees of flexion
2. Flexion contracture >10-15 degrees
3. Severe medial compartment articular damage (Ahlback grade III or higher)
4. Patellofemoral OA (symptomatic)
5. Lateral compartment OA
6. Prior lateral meniscectomy
7. Inflammatory arthritis
8. Ligament instability (especially varus thrust gait)
9. Lateral tibial subluxation >1 cm
10. Obesity (relative)
11. Smoking (relative)
12. Age >65 (relative)

Question 46

What are the complications of HTO?

[JAAOS 2011;19:590-599]

Answer 46

1. Undercorrection/overcorrection
2. Loss of correction
3. Patella baja
4. Nonunion/malunion
5. Peroneal nerve palsy
6. Compartment syndrome
7. Infection
8. DVT/PE

Question 47

What are the advantages and disadvantages of closing wedge HTOs?

[Knee Surg 2017;30:409–420] [Sports Med Arthrosc Rev 2013;21:38–46)]

Answer 47

Advantages

• Inherently stable
• Less nonunion
• No bone graft required
• May allow earlier WB

Disadvantages

• Requires fibular osteotomy or proximal tib-fib joint disruption
• Risk of common peroneal nerve injury
• Loss of bone stock
• Less predictable in achieving desired correction (no gradual correction)
• Change in offset of the upper tibial metaphysis may affect future TKA

Question 48

What are the advantages and disadvantages of opening wedge HTOs?

[Knee Surg 2017;30:409–420] [Sports Med Arthrosc Rev 2013;21:38–46)]

Answer 48

Advantages

• Avoids fibular osteotomy
• Less risk to common peroneal nerve
• Allows for gradual correction
• Allows for correction of tibial slope
• May be easier to convert to TKA
• Bone preserving
• Can perform combined ACL recon without need for additional incisions

Disadvantages
* Inherently unstable
* Loss of correction
* Risk of nonunion/malunion
* Risk of fracture of the lateral tibial plateau or cortex
* Requires bone graft

Question 49

What is the normal medial proximal tibial angle?

[Rockwood and Green 8th ed. 2015]

Answer 49

87 (ie. 3 of varus)

Question 50

When is an increase or decrease in tibial slope desirable in HTO?

[JAAOS 2011;19:590-599]

Answer 50

1. Increased tibial slope = PCL deficiency
2. Decreased tibial slope = ACL deficiency

Question 51

Where is the lateral hinge located for the osteotomy (HTO)?

[JAAOS 2011;19:590-599]

Answer 51

1cm distal to the joint line and 1cm medial to the lateral cortex

Question 52

Describe the preoperative planning and determination of correction in HTO?

[JAAOS 2011;19:590-599]

Answer 52

1. 62.5% = Fujisawa point (considered the optimal location for the mechanical axis)
   * Corrects to 3-5 degrees valgus
2. Line from center of femoral head and line from center of the ankle pass through Fujisawa point
3. angle of correction = angle formed betweeen 2 lines
4. proposed osteotomy line = extends form 4cm distal to medial joint line to tip of fibula laterally
5. predicted medial osteotomy opening - determined by transferring the proposed osteotomy line to the intersection of the lines oat fujisawa point and measuring the distance between the 2 lines at the end of the osteotomy line

• Line a-b = proposed osteotomy from 4cm distal to joint line medial and to tip of fibula laterally
• Alpha = angle of correction
• b1-c = gap in mm for correction

Question 53

What are the technical challenges of TKA after HTO?

[AAOS comprehensive review 2, 2014]

Answer 53

1. Previous incisions
2. Hardware
3. Patella baja (difficult exposure)
4. Tibial abnormalities (metaphyseal offset after closing wedge osteotomy)

Question 54

What is the normal distal femoral valgus angle?

[JAAOS 2018;26:313-324]

Answer 54

7-9° valgus

Question 55

What are the indications for a varus producing distal femoral osteotomy?

[Arthroscopy Techniques 2016: 5(6); e1357-e1366]

Answer 55

1. Genu valgus alignment
2. Isolated lateral compartment OA
3. Chondral or osteochondral lesions of the lateral compartment
4. Meniscal deficiency of the lateral compartment
5. Cartilage repair/restoration of the lateral compartment
6. Chronic MCL or cruciate instability
7. Refractory patellar instability

Question 56

What are the contraindications for a varus producing DFO?

[Arthroscopy Techniques 2016: 5(6); e1357-e1366] [JAAOS 2018;26:313-324]

Answer 56

1. Inflammatory OA
2. Medial or patellofemoral OA
3. Flexion contracture >15°
4. Flexion <90°
5. Deformity >15°
6. Tibial subluxation
7. Gross knee instability
8. Severe lateral compartment bone loss
9. Nicotine use (relative)
10. Obesity (relative)
11. Age >50 (relative)
12. History of septic arthritis (relative)
13. Inability to comply with postoperative instructions

Question 57

In general, what is the cause of the valgus knee deformity in OA?

[Arthroscopy Techniques 2016: 5(6); e1357-e1366][JAAOS 2018;26:313-324]

Answer 57

1. Hypoplastic lateral femoral condyle
   
   • Femoral osteotomy avoids an oblique joint line (which would occur if the valgus was addressed through a HTO)
2. Valgus secondary to proximal tibia deformity (less common)
   
   • Eg. tibial fracture malunion
   • Consider proximal tibia varus osteotomy
3. mcl deficiency
   
   • deficent medial structures in setting of normal bony anatomy
   • consider soft tissue procedure

Question 58

what are the radiographic measurements that should be assessed when planning a DFVO

Answer 58

1. mechanical axis of the limb
   
   • valgus knee represented by a line passing lateral to the center of the knee
2. angle formed between the mechanical axis of the femur and mechanical axis of the itbia
   
   • 5° is the smallest practical angle for consdieration of DFVO
3. lateral distal femoral angle
   
   • angle created by the mechanical axis of the femur and a line drawn transversely acrosss the articular surface of the lateral femoral condyles
   • typical value is between 85-90° (avg 87)
   • angle <85 represents a hypoplastic lateral femoral condyle = femur as the location of the deformity
4. medial proximal tibial angle
   
   • angle created by the mechanical axis of the tibia and horizontal line across the medial and latearl tibial plateaus
   • typical value is between 85-90° (avg 87)
   • angle >90° = tibia as the locaiton of the deformity (contraindication for DFVO)

Question 59

What are the advantages and disadvantages of a DFVO over arthroplasty in younger patients?

[JAAOS 2018;26:313-324]

Answer 59

Advantages

• Native joint preservation
• Unrestricted high impact activity after union
• Possible delay of future arthroplasty

Disadvantages

• Longer rehabilitation
• Early WB restrictions
• More variation in pain relief
• Conversion to TKA more technically challenging

Question 60

What are the advantages of a medial closing wedge vs. a lateral opening wedge DFO?

[Arthroscopy Techniques 2016: 5(6); e1357-e1366] [JAAOS 2018;26:313-324]

Answer 60

1. Medial closing wedge

• Direct bone contact leads to increased stability
• Reliable bone healing
• No bone graft
• Less hardware irritation

2. Lateral opening wedge

• More precise adjustment of correction
• Single osteotomy
• Familiar lateral approach
• Access to the lateral compartment for concomitant procedures

Question 61

What are the indications for a medial closing wedge over a lateral opening wedge osteotomy?

[JAAOS 2018;26:313-324]

Answer 61

1. Angle of correction >17.5°
2. Operated limb exhibits a limb length discrepancy
3. Earlier WB desired
4. Risk factors for delayed union (eg. smoking, neuropathy, poor bone quality, obesity)

Question 62

What should a patient be counselled on prior to osteotomy for unicompartmental OA?

[Sports Med Arthrosc Rev 2013;21:38–46)]

Answer 62

1. Some degree of continued pain
   * The pain is accepted in exchange for higher activity levels and avoidance of prosthetic implant failure
2. Conversion to arthroplasty in the future is not a failure but rather an anticipated event

• Survival rates are ~95% at 5 years, 80% at 10 years and 55% at 15 years
• Outcomes of TKA after osteotomy are equivalent

3. Cosmetic changes to limb alignment

Question 63

How is the correction angle calculated for a DFO?

[Arthroscopy Techniques 2016: 5(6); e1357-e1366]

Answer 63

1. Goal is a neutral mechanical axis (mechanical axis passes through or just medial to the center of the knee)

• Lateral compartment OA consider correction 62.5% of the way to the medial compartment
• Other indications are typically through the center of the knee

2. Correction angle = angle formed between the mechanical axis of the femur (center of head of femur and selected point) and mechanical axis of tibia (center of the talus and selected point)
3. Confirm the deformity is femoral based

• Calculate the medial-proximal tibial angle (average = 87)
  
  • Should be normal if DFO planned
• Calculate the lateral-distal femoral angle (average = 87)
  
  • Should be decreased if DFO planned

Question 64

What is the postoperative management following DFVO?

[JAAOS 2018;26:313-324]

Answer 64

1. 6 weeks nonWB (allow ROM)
2. 6-12 weeks graduated WB
3. 12 weeks start low impact/light duties
4. 6 months resume high impact/full duties

Question 65

What are the complications of a DFVO?

[JAAOS 2018;26:313-324]

Answer 65

1. Distal femoral fracture
2. Nonunion/malunion
3. Neurovascular injury
4. Infection
5. Thromboembolic event
6. Stiffness
7. Painful hardware

Question 66

what are the categories of instability following TKA

Answer 66

1. extension (varus/valgus)
2. flexion
3. midflexion
4. genu recurvatum
5. global

Question 67

what are the likely causes of instability when it occurs early (weeks to months) comapred to late?

Answer 67

1. early onset - gap imbalance, component malalignment, iatrogenic ligament injury, patellar tendon rupture or patellar fracture
2. late onset - poly wear, ligament attrition

Question 68

solution table for unbalanced knee
1. loose in flexion/loose in extension
2. loose in flexion/ balanced in extension
3. loose in flexion/ tight in extension
4. balanced in flexion/loose in extension
5. balanced in flexion/tight in extension
6. tight in flexion/loose in extension
7. tight in flexion/balanced in extension
8. tight in flexion/tight in extension

Answer 68

Question 69

what is the cause of extension instability

Answer 69

1. symmetric - extension gap larger than flexion gap
   
   • excessive distal femoral resection
2. asymmetric
   
   • failure to correct the coronal plane alignment resulting in ligamentous asymmetry
     * overtime ligamentous attenuation or frank rupture occurs on the convex side of the deformity
   • traumatic ligamentous injury

Question 70

what is the treatment of extension instability

Answer 70

SYMMETRIC
* distal femoral augmentation to lower joint line and balance gaps

ASYMMETRIC
* correct the deformity and coronoal plane alignment
* may require release of contracted structures on concave side
* varus-valgus contrained liner may be required

Question 71

what is the definition of flexion instability

Answer 71

1. flexion gap that is larger or more lax than the extension gap
2. results in increased stress on surrounding structures (collateral ligaments, quadriceps, extensor mechanism, hamstrings)

Question 72

what is the cause of flexion instability

Answer 72

1. inability to balance the flexion and extension gaps at primary arthroplasty
2. gradual laxity of the posterior capsule or PCL in cruciate-retaining knees

Question 73

what are the technical factors that can lead to flexion instability

Answer 73

1. too little distal femoral resection in a preexistin flexion contracture
2. overly aggressive posterior condylar resection with undersized femoral implants
3. excessive posterior tibial slope
4. over release of the PCL in the CR knee

Question 74

what are the symptoms associated with flexion instability

Answer 74

1. sense of distrust and sense of knee wanting to shift or slide (Classically, when rising from seated, position or navigating stairs)
2. knee often never felt right from time of index surgery
3. flexion contractures can develop - knee assumes a flexed posture secondary to quadriceps weakness/fatigue and a tight posterior capsule (from preop flexion contracture)
4. diffuse periretinacular tenderness
5. recurrent low-grade effusions

Question 75

what are physical examination features of flexion instability

Answer 75

1. current benchmark for dx is the tibial translation test
   
   • examiner subjectively grades anterior tibial translation with the knee at 90° flexion when the quad relaxed and foot free (open chain)
   • instability graded as <5mm, 5-10mm, >10mm
2. posterior sag sign
   * tibia translates posteriorly when the knee is flexed to 90° and the heel is supported on the table to relex the quad
3. active knee flexion
   * patient is seated at the end of the examination table with the kene bent over the edge and the quad is relaxed. if flexion isntability is present, the larger flexion space will cause the tibia to descend and bring the poly out of contact with the posterior condyles. when the patient is asked to actively extend, the physician will note the tibia pull up to articulate with the femur upon initiation of quad contraction, and only after this contact is reestablished, will the tibia extend
4. effusions
5. pain to palpation of the pes anserine and hamstring tendons

Question 76

what is the workup of flexion instability

Answer 76

1. serum esr/crp
2. consider aspiration
3. radiographs - evaluate the lateral radiograph to calculate the slope of the tibial tray and psoterior femoral condylar offset

Question 77

intraop, what is an acceptable amount of flexion instability

Answer 77

1. <5mm anterior tibial translation with the patella reduced and knee at 90° of flexion

Question 78

what are the recommended sequential steps in evaluatin flexion instability during revision TKA

Answer 78

1. remove existing implants
2. ensure retangular and extension gaps
   
   • use tibia as a reference
   • gaps can be assessed with trial blocks or tensioning devide
3. check tibial slope
   
   • if excessive tibial slope = recut tibia and trial gaps - if still loose in flexion proceed to next step
4. increase posterior femoral offset
   
   • achieved with a femoral implant with a larger AP diamater (upsize)
   • may require posterior condyle metal augments if gap between implant and bone
   • if flexion instability persists proceed to next step
5. resect more distal femur
   
   • requires larger poly during trialing
   • if flexion instability persists proceed to next step
6. constained prosthesis
   
   • hinged prosthesis may be required when flexion space is so large that equalization to the extension space is impossible

Question 79

what are the oucomes of revision surgery for flexion instability

Answer 79

patient outcomes after revision TKA for flexion instabilirty show the least amount of imporvement when compared with revisions for other TKA failure etiologies

Question 80

what is the definition of midflexion instability

Answer 80

rotation instability between 30-90 flexion
poorly understood and difficult to differentiate from flexion instability

Question 81

what are thought to be causes of midflexion instability

Answer 81

1. elevation of the joint line
2. femoral component sagittal plane design
3. anterior MCL attenuation

Question 82

what is the casue of genu recurvatum

Answer 82

often associated with polio, RA, charcot arthropathy
in polio the quad weakness and ankle equinus leads to ambulation with the knee locked in hyperextension

Question 83

what is the management of genu recurvatum in TKA

Answer 83

1. bracing
2. ps implants with long stems, varus-valgus constrained liners
3. rotating hing can be used but risk of failure due to hyperextension force

Question 84

what is the definition of global instability

Answer 84

multidirectional instability and may be associated with recurvatum

Question 85

what is the management of global instability

Answer 85

revision to varus/valgus constrained liner or hinger TKA as a salvage

Question 86

What is the definition of supracondylar periprosthetic (TKA) fracture?

Answer 86

Within 15cm of the joint line or, in the case of a stemmed component, within 5 cm of the proximal end of the implant.

Question 87

What are classification systems of supracondylar periprosthetic (TKA) fractures?

Answer 87

1. Rorabeck and Taylor

• Type I – undisplaced fracture, prosthesis intact
• Type II – displaced fracture, prosthesis intact
• Type III – displaced or undisplaced fracture, prosthesis is loose or failing

2. Su classification

• Type I – fracture proximal to the femoral component
• Type II – fracture originates at the proximal end of the femoral component and extends proximally
• Type III – fracture line is distal to the upper edge of the component’s anterior flange

Question 88

What are the management options for supracondylar periprosthetic (TKA) fractures?

Answer 88

1. Nonoperative
2. Plates and screws
3. Fixed-angle devices

• Dynamic condylar screw
• Blade plate
• Locking plates*

4. Intramedullary nails

• Supracondylar nail*
• Antegrade nail
• Retrograde nail

5. Revision arthroplasty*

Question 89

What is the management of TKA periprosthetic fractures based on Su classification?

Answer 89

1. Type I – antegrade or retrograde IM nail
2. Type II – fixed angle device or retrograde supracondylar nail
3. Type III – fixed angle device or revision arthroplasty

Question 90

What is the incidence of periprosthetic (TKA) tibia fractures?

[JAAOS 2018;26:e167-e172]

Answer 90

0.4 - 1.7%

Question 91

What radiographic finding should make you think of a periprosthetic (TKA) tibia fracture?

[JAAOS 2018;26:e167-e172]

Answer 91

Proximal tibia varus (associated with Felix type I and II)

Question 92

What test should be ordered to evaluate for (TKA) implant stability if unclear on radiographs?

[JAAOS 2018;26:e167-e172]

Answer 92

CT scan

Question 93

In what cases should an infectious workup be performed (in context of TKA periprosthetic fracture)?

[JAAOS 2018;26:e167-e172]

Answer 93

1. History of PJI
2. Imaging findings that are concerning for infection
3. Severe fracture pattern that is inconsistent with mechanism

Question 94

What is the Classification system for TKA periprosthetic fractures of the tibia?

[Revision Total Hip and Knee Arthroplasty 2012, Berry et al]

Answer 94

Mayo Clinic classification of periprosthetic tibial fractures (aka Felix classification)

• Four types
  
  • Type I - fractures involve the tibia plateau and extend into the metaphysis (usually medial plateau and involve the tibial baseplate/bone interface)
  • Type II - fractures involve the meta-diaphyseal area and extend to the tibial stem/bone interface
  • Type III - fractures occur distal to the tibial stem
  • Type IV - tibial tubercle fractures
• Three subcategories
  
  • A - well fixed tibial component
  • B - loose tibial component
  • C - intraoperative fracture

Question 95

What are risk factors for periprosthetic (TKA) fracture of the tibia?

[Revision Total Hip and Knee Arthroplasty 2012, Berry et al]

Answer 95

1. Varus malalignment
2. Rotational malposition
3. Knee instability
4. Loose components
5. Keeled tibial components
6. Trauma
7. Proximal tibia osteolysis
8. Poor bone quality

Question 96

What are the general considerations for management of periprosthetic tibial plateau fractures?

[JAAOS 2018;26:e167-e172]

Answer 96

1. Consider nonoperative treatment if:

• Stable component
• Well aligned tibial component
• Well aligned mechanical tibial axis

2. Consider operative treatment if:

• Major fracture displacement or angulation
• Unstable component
• Altered tibial component alignment

3. Construct options

• Component stable = locking plates (IM nail in select cases)
• Component unstable = revision TKA with long stemmed tibial component
• Substantial bone loss or comminution = megaprosthesis (rare)

Question 97

What is the management of proximal tibia periprosthetic fractures?

[Revision Total Hip and Knee Arthroplasty 2012, Berry et al]

Answer 97

1. Nonoperative

• Consider for all types with stable component
• Consider in those with unstable component when fracture healing is desired prior to revision

2. Operative

• Type IA - nonoperative or ORIF
• Type IB - tibia revision with diaphyseal-fitting stem +/- cement/bone graft/augments to fix defects
• Type IC - fixation with cancellous screw prior to prosthesis insertion OR use a stemmed tibial component
• • Type IIA - nonoperative or ORIF
• Type IIB - tibia revision with diaphyseal-fitting stem +/- ORIF +/- bone graft OR tumor prosthesis
• Type IIC - tibia revision with diaphyseal-fitting stem
• • Type IIIA - nonoperative OR ORIF (locking plate)
• .Type IIIB - rare, consider delayed revision after fracture heals
• • Type IV - ORIF with screw or wire if displaced OR nonoperative if nondisplaced

Question 98

what definitions exist for stiffness after TKA

Answer 98

1. arc of motion <45°
2. lacking >=10 or more terminal extension
3. less than 80 to 110 of maximum flexion
4. less motion than preop
5. patient dissatisafaction with their arc of motion

Question 99

What are the clinical features of arthrofibrosis after TKA?

[The Journal of Arthroplasty 32 (2017) 2604e2611]

Answer 99

1. Loss of ROM due to stiffness (no consensus on degree of ROM loss to define arthrofibrosis)
2. Pain with palpation
3. Swollen/inflamed knee

Question 100

what is the prevalence of stifffness after TKA

Answer 100

1.3-5.8%

Question 101

how can stiffness by graded based on ROM

Answer 101

1. range of flexion 90-1000 for mild, 70-89 for moderate and <70 for severe
2. extension deficit 5-10 for mild, 11-20 for moderate and >20 for severe

Question 102

what are the causes of postop stiffness following TKA

Answer 102

1. preop
   
   • poor preop ROM
   • african american
   • females
   • younger age
   • nicotine use
   • previous knee surgery
   • contralateral TKA stiffness
2. intraop
   
   • flexion-extension gap imbalance
   • oversized components
   • malrotation of components
   • inadquate removal of posterior osteophytes, meniscal remnants, synovial soft tissue
   • failure to restore posterior condylar offset
   • overstuffing PF joint (inadequate patella resection or anteriorization of femoral component
   • anterior overhand of the tibial component
   • joint line elevation
   3. postoperative
      
      • poor physio compliance
      • poor pain control
      • postop hemarthrosis

Question 103

what must be ruled out prior to dx of postop TKA stiffness as arthrofibrosis

Answer 103

infection and mechanical factors

Question 104

What are the functional deficits of loss of knee ROM?

[The Journal of Arthroplasty 32 (2017) 2604e2611]

Answer 104

1. Flexion required

• ~70° for typical gait
• 80-90° for stair ascent and descent
• 125° for squatting to pick object up from floor

2. Extension

• 5° loss of extension causes limp
• 15° flexion contracture results in 22% more extensor mechanism demand

Question 105

What is the management of arthrofibrosis post TKA?

[The Journal of Arthroplasty 32 (2017) 2604e2611]

Answer 105

1. Aggressive physiotherapy
   * NSAIDs and RICE, stretching, bracing, PROM/AROM, quads strengthening
2. <3 months and no improvement with nonop (as early as 6 weeks)

• MUA
  
  • Technique:
    • GA, muscle relaxation, hip flexion to 90°, progressive flexion, hold 30 seconds at new max
  • .Complications:
    • Fracture, wound dehiscence, patellar tendon avulsion, quads strain or rupture, hemarthrosis, HO, pulmonary embolism
      3. >3 months and no improvement with nonop or failed MUA
• First line = Arthroscopic debridement
  
  • Technique:
    
    • Release of adhesions in suprapatellar pouch, gutters and intercondylar notch
• Second line = Open debridement
  
  • Performed after failure of arthroscopic debridement
  • Complications – damage to prosthesis, hemarthrosis, extensor mechanism disruption, fracture, infection, neurovascular injury
• Third line = revision TKA
  
  • Technique:
    
    • Partial or complete replacement
  • Considered if potential mechanisms identified including – improper component sizing, rotation, alignment or soft tissue balance

Question 106

What is the expected improvement in knee ROM following MUA?

Answer 106

Increased flexion range of motion 30-42° and overall knee range of motion 31-47°

Question 107

What is the mechanism of osteolysis in TKA?

[JAAOS 2015;23:173-180]

Answer 107

Polyethylene wear debris results in macrophage activation following phagocytosis leading to osteoclast activation and resultant bone resorption

• Main inflammatory factors resulting in osteoclast activation include TNF-α, IL-1, IL-6, IL-8, RANKL [Instr Course Lect. 2013; 62: 201–206.]

Question 108

What are the modes of polyethylene wear in TKA?

[JAAOS 2015;23:173-180]

Answer 108

1. Adhesive
2. Abrasive
3. Fatigue

***Also:

Mode 1: Articulation between intended surfaces

• Femoral head and acetabular cup
• Most common mode of failure in a well-functioning prosthesis

Mode 2: Articulation of primary bearing surface and a material that was never intended to be a bearing surface

• Femoral head and metal backing (an acetabular lining that has worn though to its metal backing)

Mode 3: Articulation between intended surfaces but in the presence of third body particles

• PMMA, bone, metal debris, corrosion wear (metal on metal)

Mode 4: Articulation between 2 non-bearing secondary surfaces.

• Backside wear is an example–back of poyethylene insert on its metal backing

Mnemonic:

Mode 1 – primary to primary

Mode 2 – 2 diff surfaces

Mode 3 – 3^rd body

Mode 4 – backside (last) (or 2² – 2 x secondary)

Question 109

What polyethylene particle size leads to the greatest stimulation of macrocytic activation?

[JAAOS 2015;23:173-180]

Answer 109

0.2 - 7µm

Question 110

What factors increase the risk for osteolysis development post TKA?

[JAAOS 2015;23:173-180]

Answer 110

1. Patient factors

• Young, active
• Obese

2. Surgical technique

• Component malposition (eg. varus)
• Poor balance

3. Material factors

• Sterilization method
  
  • Gamma radiation in air increased risk compared to ethylene oxide or gamma radiation in inert gas
• Non-highly crosslinked polyethylene
• Backside wear
  
  • Micromotion between the poly and tibial tray
    
    • Increased with nonpolished tibial trays, poor locking mechanism
• Thinner poly
• Noncemented baseplates supplemented with tibial screws
• Metal backed patellar components

Question 111

What are the features of osteolytic lesions post TKA?

[JAAOS 2015;23:173-180]

Answer 111

1. Typically focal, well-marginated
2. Often with cortical thinning or perforation
3. Arise at margin of synovial cavity extending along bone-implant interface
4. Tibial lesions are usually under the tibial tray and extend along the stem
5. Femoral lesions occur adjacent to the femoral component (more common in posterior condyles), extend for a variable distance proximally

Question 112

What is the recommended monitoring for osteolytic lesions post TKA?

[JAAOS 2015;23:173-180]

Answer 112

Routine followup annually for first 3 years then every 2 years thereafter

• Incidental osteolysis noted
  
  • Obtain oblique radiograph (better visualizes the posterior condyles)
  • Continue close observation if asymptomatic, nonprogressive lesions, stable components
• Symptomatic osteolysis/progressive osteolysis/component failure
  
  • Obtain CT scan (determine size, location)
  • Plan for surgery
    
    • Tibial osteolytic lesions
      
      • Poly exchange and impaction bone grafting
        
        • Consider if lesion is small (<2cm), component stable and well aligned
      • Tibial revision
        
        • Consider diaphyseal stem fixation, augments, screw in cement, porous metal sleeves
    • Femoral osteolytic lesions
      
      • Femoral revision
        
        • Consider stemmed implant, distal or posterior augments, increased constraint if collaterals compromised

Question 113

What are the causes of bone loss in TKA?

[JAAOS 2017;25348-357]

Answer 113

• Stress shielding
• Osteolysis
• Osteonecrosis
• Infection
• Implant loosening

Question 114

What is the classification for bone loss in TKA?

[J Am Acad Orthop Surg 2011;19: 311-318] [Revision Total Hip and Knee Arthroplasty 2012, Berry et al] [JAAOS 2017;25:348-357] -

Answer 114

Anderson Orthopaedic Research Institute (AORI) Classification of Bone Defects

1. Type 1 - intact metaphyseal bone

• Good cancellous bone at or near a normal joint line level
• Minor bone defects that do not compromise the stability of the component

2. Type 2 - damaged metaphyseal bone

• Loss of cancellous bone that requires cement fill, augments, or small bone grafts to restore a reasonable joint line
• Subclassifiead
  
  • Type 2A - defect involves one femoral or tibial condyle
  • Type 2B - defect involves both condyles
• Type 2 femur – bone loss is distal to the epicondyles
• Type 2 tibia – bone loss extends as low as, but not below, the tip of the proximal fibula
  3. Type 3 - deficient metaphyseal segment
• Deficient bone that compromises a major portion of either condyle or plateau
• These defects usually require a large structural allograft, a rotating hinged component or custom components

Question 115

In revision TKA what landmarks can be used to restore the joint line?

[JAAOS 2017;25:348-357]

Answer 115

1. Lateral epicondyle = 25mm proximal
2. Medial epicondyle = 30mm proximal
3. Adductor tubercle = 40-45mm proximal
4. Inferior patellar pole = 10mm proximal
5. Meniscal scar
6. Tip of fibula = 15mm distal

Question 116

what is a described technique for determining the joitn line level based on preop radiographs

Answer 116

1. transepicondylar axis width (TEAW) ratio
   
   • TEAW = defined as the distance connecting the upper edge of the medial epicondylar sulcus and the most prominent edge of the lateral epicondyle on an AP radiograph
   • medial joint line (distance as measure from the medial epicondyle sulcus) = 0.4 x TEAW
   • lateral joint line (distance as measure from the most promiment edge of the lareal epicondyle ) = 0.3 x TEAW
2. helpful if the original radiographs before primary TKA are not available or if the contralateral knee also has been replaced

Question 117

when the degree of bone loss most accurately determined for revision TKA

Answer 117

intraop after component removal

radiographs and Ct often underestimate

Question 118

what are the zones of fixation in revision

Answer 118

1. the distal femur and proximal tibia may each be divided into 3 anatomical zones in which fixation can be achieved
   
   • zone 1 - joint surface or epiphysis
   • zone 2 - metaphysis
   • zone 3 - diaphysis
2. stable fixation can be achieved if fixation can be achieved in 2 out of 3 zones

Question 119

by what means can fixation be achieved in each zone

Answer 119

zone 1 - cement, metal augment or bone graft
zone 2 - cones, sleeves, cement or bone graft
zone 3 - cemented or press-fit stems

Question 120

In revision TKA what implants should be considered?

[JAAOS 2017;25:348-357]

Answer 120

1. Posterior stabilized
   * Indication – intact collateral, no varus/valgus instability
2. Unlinked constrained (varus/valgus constrained liner)
   * Indication – mild to moderate varus/valgus instability
   * Functions to limit rotation, M-L translation, varus/valgus angulation
3. Rotating hinge
   * Indicated for patients with bone loss and compromised collateral ligaments, compromised extensor mechanism or severe flexion-extension mismatch
4. Modular segmental (megaprosthesis)

Question 121

What other implant options should be considered to deal with bone loss in revision TKA?

[JAAOS 2017;25:348-357]

Answer 121

1. Stems
   * Bypass deficient metaphyseal bone and engage the diaphysis
   * Can be cemented, cementless, or hybrid
2. Cement
   * Indication = <5mm defect affecting <50% of bone surface area
   * advantage - simple, fills defect readily
3. Cement and screw
   * Indication = 5-10mm defect, contained ur uncontained defects
   * advantage- reliable, reproducible,easily performed, inexpensive
4. bone autograft or allograft
   
   • indication - moderate sized contained defects in young patients
   • technique involves impaction grafting suth that graft can support load early with eventual incorporation and remodeling
5. Impaction grafting
   * Advantage
   
   • Restores bone stock
   • Cost effective
   • good initial support
     * Disadvantage
   • Technically difficult
   • Risk of intraop fracture
   • Disease transmission
   • Infection
   • Graft resorption
     * Can use in contained and uncontained defects (with mesh)
     * Impact graft with trial stem in place then cement final stem
6. Bulk structural allograft
   * Advantages – good initial support, restores bone stock
   * Disadvantage – prolonged surgical time, nonunion, delayed union, disease transmission, infection, graft resorption
   * Femoral head allograft is commonly used (tibia is prepared with acetabular reamer) graft is prepared to be 2mm larger than defect and devoid of sclerotic bone, it is then press fit into place +/- augmented with screw fixation
7. Metal augments
   * Indication
   
   • Uncontained defects 5-10mm
   • ≥40% of bone-implant interface unsupported
   • Periphery of defect involves ≥25% of cortex
     * Advantages
   • Immediate support
   • Short surgical time
   • No resorption
     * Disadvantages
   • Expense
   • No bone restoration
   • Requires additional bone resection
   • Limitation in size and shape
8. Metaphyseal cones and sleeves
   * Advantages
   
   • Fills large defects
   • Immediate structural support
     * Disadvantages
   • Expense
   • No bone restoration
   • Requires additional bone resection
   • Difficult removal if revision required
   • intra-opeartive fracture risk
     * The primary difference between trabecular metal cones and metaphyseal sleeves is that the interface of the sleeve with the implant is created via a Morse tapered junction rather than with cement
   • cone technique - inolves preparation of defect with broach or burr, cone is press fit into defect, implant is then cemented to cone (thherefore insertion of cone is independent of implant)
   • sleeve technique - involves preparation of the diaphysis with sequential reaming, followed by broaching of the metaphysis for accepting the sleeve
9. megaprosthesis
   
   • indication - selected elderly patients with severe bone loss, articular deformities and extreme ligamentous instability

Question 122

based on the AORI classification what are the options to manage bone loss during revision TKA

Answer 122

AORI type I - small/cotained defects
* cement, cement with screws, boen autograft or allograft

AORI type 2A/2B - small/uncontained defects
* modular metal augments

AORI type 3 - large/uncontained defects
* structural allograft
* cones or sleeves
* megaprosthesis

Question 123

What are the advantages and disadvantages of uncemented vs. cemented stems in revision TKA?

Answer 123

1. Cemented
   * Advantages
   
   • Can be shorter (do not need to engage diaphysis)
   • Allow delivery of antibiotics
   • Ideal for osteoporotic bone/capacious canals/ipsilateral THA

• Disadvantages
  
  • Difficult removal

2. Uncemented
   * Advantages
   
   • Obtain correct limb alignment
     * Disadvantages
   • Require offset options
   • Long stems required to engage diaphysis
   • Risk of iatrogenic fracture
   • End-of-stem pain

Question 124

What is the approach to femoral bone loss in revision TKA?

[JAAOS 2017;25:348-357]

Answer 124

1. Assess integrity of collateral ligaments
   * If compromised = manage with increased constraint (rotating hinge or megaprosthesis)
2. Estimate the amount of distal bone loss based on references to the epicondyles or adductor tubercle
   * Distal defects <10mm = manage with cement (with/without screws), morcelized graft, or metal augments
   * Distal defects >10mm = manage with tantalum cone, metaphyseal sleeve, or bulk structural allograft

Question 125

What is the approach to tibial bone loss in revision TKA?

[JAAOS 2017;25:348-357]

Answer 125

1. Assess integrity of the tibial tuberosity
   * If compromised = manage with increased constraint (rotating hinge or megaprosthesis)
2. Estimate the amount of proximal bone loss based on references to the fibular head
   * Proximal defects <10mm = manage with cement (with/without screws), impaction grafting or metal augments
   * Proximal defects >10mm = manage with tantalumn cone, metaphyseal sleeve, or bulk structural allograft

Question 126

What are the principles of revision TKA? [JAAOS 2017;25:348-357]

Answer 126

1. Rebuild the tibial platform
   * Make a fresh cut perpendicular to the mechanical axis of the tibia
2. Reestablish the flexion gap
   * Restore posterior condylar offset or posteriorize the femoral component with an offset stem
   * Ensure a rectangular flexion gap with proper external rotation of implant
3. Reestablish the extension gap
   * Distal femoral implant should be at native joint line (use above references)

Question 127

what are the causes of extra-articular deformity

Answer 127

2. post traumatic malunion
3. metabolic bone disease (OI, paget, blount, hereditary hypophosphatemia, hyperparathyroidism
4. congenital abnormalities
5. previous osteotomies
6. tumors

Question 128

What are the options to address extra-articular deformity in planned TKA?

[Orthopedics 2007; 30(5): 373]

Answer 128

1. Asymmetrical intra-articular resection and soft tissue balancing
2. Corrective osteotomy prior to TKA or at time of TKA

Question 129

When is correction of an extra-articular deformity by intra-articular resection indicated in context of TKA?

[Orthopedics 2007; 30(5): 373][JAAOS 2016;24:220-230]

Answer 129

1. Indicated if the line perpendicular to the mechanical axis of the femur at the femoral condyle does not pass through the insertions of the collateral ligaments. (B)
2. Indicated if the line drawn from the medullary canal of the tibia distal to the angular deformity passed within the tibial condyle (C)
3. In general, an intra-articular compensatory correction can be achieved if the deformity is far from the joint and limited to <20° in the coronal plane on the femoral side and <30° on the tibial side.

Question 130

why are intra-articular corrections of femoral sided deformities less well tolerated than tibial deformities in the coronal plane

Answer 130

corrective cut of the distal femur will change the balance of the knee only in extension whereas a corrective cut on the tibial side will change the balance of the knee equally in flexion and extension

Question 131

When is correction of an extra-articular deformity by corrective osteotomy indicated?

[Orthopedics 2007; 30(5): 373]

Answer 131

1. Indicated if the collateral ligament or patellar attachment will be jeopardized by bone resection or if large asymmetric soft-tissue gaps will be created that will present difficulties for soft-tissue balancing
2. Indicated if the line drawn from the medullary canal of the tibia distal to the angular deformity passes outside the tibial condyle

Question 132

What is the impact of the location of the extra-articular deformity in context of TKA?

[JAAOS 2016;24:220-230]

Answer 132

The closer the deformity is to the joint the greater the impact on knee alignment

• For example, if the apex of a femoral or tibial deformity is located at a distance from the joint that corresponds to 25% of the length of the bone, the effect of the deformity will be twice that of a deformity located at a distance corresponding to 50% of the length of the bone.

Question 133

when is correction of a sagittal plane extra-articular deofrmity correctable by an intra-articular resection

Answer 133

1. intraarticular correction with TKA is feasible if a procurvatum deformity is less than 10° or a recurvatum deformity less than 20 °
   
   • recurvatum is better tolerated as risk of anterior femoral notching is less with intra-articular correction

Question 134

what is correction of a sagittal plane extra-articular deformity b a corrective osteotomy prior to TKA indicated

Answer 134

generally when greater than 20° recurvatum or procurvatum is present

Question 135

What are the management options of a fracture nonunion prior to TKA?

[Orthopedics 2007; 30(5): 373]

Answer 135

1. Perform ORIF of the fracture, along with a standard arthroplasty
2. Use a long-stem TKA to fix the fracture, similar to the technique used with osteotomy
3. Use a custom metaphyseal replacement prosthesis if the fracture is adjacent to the joint and severely comminuted

Question 136

What are the risk factors for extensor mechanism disruption after TKA?

[JAAOS 2015;23:95-106]

Answer 136

1. Multiply operated knee
2. Systemic conditions (RA, renal disease, DM)
3. Obesity
4. Iatrogenic injury during TKA
5. Malposition and instability

Question 137

What are risk factors for quadriceps rupture post TKA?

[JAAOS 2015;23:95-106]

Answer 137

1. Aggressive patella resection compromising insertion of quads
2. Superior lateral genicular artery disruption

Question 138

What are risk factors for patella fracture after TKA?

[JAAOS 2015;23:95-106] [JBJS 2014;96:e47(1-9)]

Answer 138

1. Overresection of the patella (<12mm)
2. Implant malalignment
3. Disruption of patella blood supply (lateral release)
4. Large central patellar peg
5. Metal-backed uncemented patellar component

Question 139

What are risk factor for patellar tendon rupture?

[JAAOS 2015;23:95-106]

Answer 139

1. Systemic disease
2. Stiff knee (revision surgery, previous HTO or tibial tubercle transfer)

Question 140

What are the layers of the quadriceps tendon?

[JAAOS 2015;23:95-106]

Answer 140

Trilaminar structure

• Superficial – rectus femoris (pass over the patella and become continuous with the patellar tendon)
• Middle – vastus medialis and lateralis
• Deep – vastus intermedius

Question 141

What are management options for a deficient extensor mechanism after TKA?

[JAAOS 2015;23:95-106]

Answer 141

1. Nonoperative

• Indicated for elderly, sedentary patient or poor surgical candidate
• Involves walking aids and knee brace (locking in extension while ambulating and unlocking allowing flexion when sitting)

2. Operative

• Primary repair
  
  • Poor outcomes, opt for reconstruction instead
• Reconstruction with fresh frozen allograft or autograft
  
  • Achilles allograft
    • Useful when the patella and patellar component are intact and patella can be mobilized within 3-4cm of joint line
  • Whole extensor mechanism allograft
    
    • Useful when patella is deficient or if patella cannot be mobilized to within 3-4 cm of joint line
  • Semitendinosus autograft
• Reconstruction with synthetic material (mesh)
• Gastrocnemius rotational flap
  
  • Medial head of gastroc with medial portion of achilles
    
    3. Keys for reconstruction
• Graft tensioned in extension to prevent extensor lag
• Knee is immobilized in extension or hyperextension for 6-8 week

Question 142

What is the recommended treatment for quadriceps tendon rupture following TKA?

[JBJS 2014;96:e47(1-9)]

Answer 142

1. Partial rupture (extensor lag <20°)
   * Nonoperative (cast or brace)
2. Compete rupture (extensor lag >20°)

• Direct repair
  
  • Midsubstance = end-to-end AND augment
  • Insertional with adequate bone stock = longitudinal drill holes AND augment
  • Insertional with inadequate bone stock = suture anchor repair AND augment

Question 143

What is the likelihood of requiring a TKA after undergoing ORIF for a tibial plateau ORIF?

[JAAOS 2018;26:386-395]

Answer 143

1. 5x more likely in tibial plateau ORIF compared to matched controls
2. 7.3% undergo TKA after 10 years

Question 144

What are the risk factors for requiring TKA following tibial plateau ORIF?

[JAAOS 2018;26:386-395]

Answer 144

• Increasing age
• Split-depression or Condylar fractures
• Female

Question 145

What are the preoperative considerations for a TKA following tibial plateau ORIF?

[JAAOS 2018;26:386-395]

Answer 145

1. Evaluate for infection
   * Aspirate, cultures and blood markers
   * Intraoperative frozen section analysis
2. Previous scars
3. Hardware
4. Bone loss
   * Consider cement augmentation, metaphyseal cones or sleeves, wedges and bone graft
5. Alignment (intra- and extra-articular)
   * Consider computer navigation and custom cutting blocks
6. Implant considerations
   * Cement and stemmed tibial component in most cases
   * Level of constraint
7. Periarticular adhesions and stiffness
8. Joint instability

Question 146

What is the suggestion for incision when previous incisions are present in context of TKA post tib plateau ORIF?

[JAAOS 2018;26:386-395]

Answer 146

1. Most recent scar should be used (provided it allows for adequate exposure)
2. Use the most lateral scar
3. Short peripatellar incisions may be ignored
4. Previous transverse incision can be crossed longitudinally at right angles

Question 147

What approach is recommended for TKA post tibial plateau ORIF?

[JAAOS 2018;26:386-395]

Answer 147

1. Medial parapatellar
2. Consider quads snip or tibial tubercle osteotomy for increased exposure

Question 148

What is the risk of infection when undergoing TKA after tibial plateau ORIF?

[JAAOS 2018;26:386-395]

Answer 148

3-20%

Question 149

What are the advantages of TKA for post-traumatic arthritis following tibial plateau fractures?

[JAAOS 2018;26:386-395]

Answer 149

1. Improved pain
2. Minor improvement in ROM

Question 150

What are the advantages of TKA for the primary management of tibial plateau fractures?

[JAAOS 2018;26:386-395]

Answer 150

1. Immediate stability
2. Early mobilization
3. Decreased reoperation rates

Question 151

What population can be considered for primary TKA for tibial plateau fracture?

[JAAOS 2018;26:386-395]

Answer 151

Elderly and osteoporotic

Question 152

What is the recommended timing for a primary TKA for tibial plateau fracture?’

[JAAOS 2018;26:386-395]

Answer 152

1. At the earliest opportunity by an experienced arthroplasty surgeon
2. Delayed fashion in the presence of severe comminution to allow fracture consolidation and tibial tubercle healing

Question 153

What are the 3 forms of osteonecrosis of the knee?

[JAAOS 2011;19:482-494]

Answer 153

1. Secondary ON
2. Spontaneous ON (SONK)
3. Post-arthroscopic ON

Question 154

What are the features of the 3 forms of osteonecrosis of the knee?

Answer 154

1. Secondary ON

• Age = <45
• Sex = men > women
• Bilaterality = >80%
• Other joints = >90% (hip, shoulder, ankle)
• Risk factors:
  
  • Direct causes (trauma, caisson disease, chemo, radiation, Gaucher)
  • Indirect causes (alcohol abuse, coagulation abnormalities, corticosteroids, inflammatory bowel disease, organ transplant, SLE, smoking)

2. SONK

• Age = >50
• Sex = women > men (3:1)
• Bilaterality = <5%
• Other joints = no
• Risk factors = idiopathic, chronic mechanical stress or microtrauma

3. Postarthroscopic ON

• Age = any
• Sex = no predilection
• Bilaterality = never
• Other joints = no
• Risk factors = meniscectomy, cartilage debridement, ACL reconstruction, laser or RFA surgery

Question 155

What imaging should be ordered for patients with suspected or confirmed osteonecrosis of the knee?

[JAAOS 2011;19:482-494]

Answer 155

1. Radiographs
   * Good for staging and monitoring progression
   * Can also screen for other diseases on differential
2. MRI
   * Good for early detection and assessing extent of disease (surgical planning)
3. Bone scan
   * Good for early detection in patients unable to get MRI

Question 156

What is the radiographic classification of osteonecrosis of the knee?

[JAAOS 2011;19:482-494]

Answer 156

Ficat classification

• Stage I – no radiographic changes
• Stage II – mottled sclerosis
• Stage III – ‘crescent’ sign indicating subchondral fracture
• Stage IV – collapse of subchondral bone

Question 157

What are the treatment options for osteonecrosis of the knee?

[JAAOS 2011;19:482-494]

Answer 157

1. Nonsurgical management

• Protected WB, analgesia, NSAIDs
• Not indicated for secondary ON
• Successful in ≥89% of early SONK with no radiographic changes and no collapse

2. Joint preserving procedures (limited evidence)

• Core decompression – if no subchondral collapse
• Bone graft through extra-articular cortical window – early ON
• Osteochondral autograft – SONK with subchondral collapse
• Osteotomy

3. Arthroplasty

• TKA – if subchondral collapse or failure of joint-preserving treatment
  
  • Recommended for secondary ON
• UKA
  
  • Not recommended for secondary ON (frequently involves multiple condyles)

Question 158

What is the most common metal used in manufacturing of femoral TKA components?

[JAAOS 2016;24:106-112]

Answer 158

Cobalt-chromium

Question 159

What are the most common metal sensitizers (allergens)? [JAAOS 2016;24:106-112]

Answer 159

Nickel, followed by cobalt and chromium

Question 160

What is the prevalence of metal sensitivity in the general population?

[JAAOS 2016;24:106-112]

Answer 160

10-15%

Question 161

What type of hypersensitivity reaction occurs with TKA metal reactions?

[JAAOS 2016;24:106-112]

Answer 161

Delayed type IV cell-mediated allergic reaction

• Interaction between T-cells, macrophages and monocytes (not antibodies)

Question 162

What screening is available preoperative for patients at risk of metal hypersensitivity (in TKA)?

[JAAOS 2016;24:106-112]

Answer 162

No evidence to recommend routine skin tests, in vitro lab tests (leukocyte migration inhibition test) or screening questionnaires

Question 163

What are the clinical presentations of metal hypersensitivity in TKA?

[JAAOS 2016;24:106-112]

Answer 163

1. Eczematous dermatitis
   * Often located in the lateral parapatellar region
   * Refer to dermatologist for topical or systemic steroids
2. Severe painful persistent synovitis

• Workup for infection
  
  • CRP, ESR, aspirate for cell count, differential, culture
• The diagnosis of metal hypersensitivity is one of exclusion
• Do not obtain serum metal levels
• No proven nonoperative treatments
• No strong evidence to support revision TKA
  
  • Patients may be offered revision TKA with zirconium or titanium alloy with nitride coating

Question 164

What is the incidence of wound complications after TKA requiring further surgery?

[JAAOS 2017;25:547-555]

Answer 164

0.33% (data from Mayo Clinic Registry with >17,000 TKAs)

Question 165

What is the incidence of postoperative incisional drainage following TKA?

[JAAOS 2017;25:547-555]

Answer 165

1-10%

Question 166

What is considered ‘persistent wound drainage’ post TKA?

[JAAOS 2017;25:547-555]

Answer 166

Continued drainage from a surgical incision for >72 hours

• Substantial drainage (>2x2 area of gauze) beyond this time is abnormal

Question 167

What is the wound strength of the healing incision at 1 week, 3 weeks, 3 months and ≥1 year (post TKA)?

[JAAOS 2017;25:547-555]

Answer 167

1 week = 3% of final strength

3 weeks = 30% of final strength

3 months = 80% of final strength

1 year = never achieves strength of normal tissue

Question 168

What are the preoperative modifiable risk factors or medical conditions that increase the risk of soft tissue complications and what optimization strategies should be considered?

[JAAOS 2017;25:547-555]

Answer 168

1. Diabetes = tight glycemic control
2. RA = medication review
   * Hold 1-2 weeks preop, restart 2 weeks postop
   * 2-3x greater risk of surgical site infection compared to OA
3. Smoking = cessation at least 6-8 weeks preop
   * ~2x rate of deep infection
4. Obesity = weight loss from caloric reduction and/or bariatric surgery
5. Malnutrition = nutritional screening, education and/or supplementation
   * Increased risk associated with:
   
   • Serum albumin <3.5g/dL
   • Total lymphocyte count <1,500mm³
   • Transferrin level <200mg/dL

Question 169

If concerned about wound healing in TKA, when should you consider preoperative consult with plastics?

[JAAOS 2017;25:547-555]

Answer 169

1. Anticipiated difficulties with closure or wound healing
   * Previous incision, severe varus or rotational deformity, prior trauma with contracted or immobile skin
2. Prior soft tissue flaps

Question 170

What is the blood supply to the anterior skin about the knee?

[JAAOS 2017;25:547-555]

Answer 170

Medial
* From deep perforating vessels passing through anterior thigh muscles and intermuscular septum
* Arterioles arborize in plane directly superficial to deep fascia of subcutaneous layer
* Skin flap dissection should be deep to this layerto preserve the perforating arteriolar
network

Question 171

What is the blood supply to the patella?

[JAAOS 2017;25:547-555]

Answer 171

Terminal branches of the peri-patellar anastomoses
* Arterial contributions from the supreme/descending geniculate artery, the medial and lateral superior geniculate arteries, the anterior tibial recurrent artery and a branch of the profunda femoris artery
* Blood supply to the patella is separated from the skin by the patellar bursa

Question 172

How should prior incisions be managed when doing TKA?

[JAAOS 2017;25:547-555]

Answer 172

1. Use the most lateral and vertical incision (even if it necessitates a lateral arthrotomy)
2. Previous transverse incisions should be crossed at 90 degrees
3. Previous short oblique incisions should be incorporated into a new vertical incision
4. Minimum 7cm skin bridge

Question 173

What is the most common area of wound complication in a mildine incision in TKA?

[JAAOS 2017;25:547-555]

Answer 173

Distal aspect

Question 174

What are important factors in incision and closure to minimize wound complications in TKA?

[JAAOS 2017;25:547-555]

Answer 174

1. Avoid excessive tension on distal incision (should always look like a ‘V’ and not a ‘U’)
2. Use full thickness skin flaps
3. Meticulous hemostasis
4. Tension free closure
5. Correct wound alignment
6. Proper closure of distal incision

Question 175

When should surgical intervention be considered to manage postoperative incisional drainage in TKA?

[JAAOS 2017;25:547-555]

Answer 175

Profuse and persistent drainage for >5-7 days

Question 176

How should you manage acute incisional drainage post TKA?

[JAAOS 2017;25:547-555]

Answer 176

1. Drainage on days 2-3
   * Keep in hospital
   * Compressive dressing
   * Avoid PT and ROM
   * Short term cessation of anticoagulants
   * Continue mechanical VTE prophylaxis
   * Consider Vac dressing
2. Drainage >5 days
   * Surgery indicated to prevent deep infection

Question 177

when is it safe to proceed to TKA after an intra-articular injection

1.

Answer 177

1. intra-articular injection of corticosteroid or hyaloronic acid <= 3months before a TKA increases the odds of periprosthetic joint infection within the first 6 months postop, independent of age, sex or comorbidities
2. injections >3months prior to TKA did not lead to a significant increase in the odds of joitn infection

Question 178

what is the mechanism of action, effectiveness and complications of corticosteroids

Answer 178

1. mechanism of action
   
   • anti-inflammatory (alter B and T cell immune function and inhibit phospholipase A2 to decrease expression of inflammatory cytokines)
   • increases fluid viscosity and HA concentration within the joint space
2. effectiveness
   * intra-artic corticosteroid is more effective on pain relief than hylaruonic acid in short term (up to 1 month) while HA is more effective in long term ( up to 6 months)
3. complications
   
   • post-injection flares within a few hours and lasting 2-3 days (experience in 2-25% of patients but does not alter the therapeutic response of corticosteroid)
   • skin depigmentation, cutaneous atrophy, and fat necrosis
   • systemic inhibition of hypothalamus-pituitary-adrenal axis - shown to last up to 2 weeks
   • increase blood glucose
   • septic arthritis
   • direct injury to cartilage with needle
   • evidence suggest assocaited with cartilage volume loss, gross cartilage daamage and chondrocyte toxicity

corticosteroids have a time and dose dependent effect on articualr cartilage, with beneficial effects occurring at low doses and durations and detrimental effects at high doses and durations

Question 179

what is the mechanism of action, effectiveness and complications of HA injections

Answer 179

1. composition
   
   • HA is naturally occuring polysaccharide within synovial fluid produced by type B synoviocytes, fibrblasts, and chondrocytes
   • sources either from a rooster combs or synthesize by means of in vitro bacterial fermentation
   • exists as high or low molecular weight and cross linked or non crosslinked
2. MOA
   *anti-inflammatory (inhibits the fibroblast release of arachidonic acid, impairing leukocyte activity, and reducing synovial levels of prostagladin, fibronectin, and cyclic adenosine monophosphate)
   
   • analgesic (inhibits nociceptors, bradykinin synthesis and substance P signoaling)
   • increases the viscosity of intraarticular fluid and entangles btw collagen fibers to trap water, providing increased compressiv strength to articular cartilage
3. effectiveness
   
   • clinically important reduciton in pain for younger patients with knee OA in those formuation with higher molecular weights or HA cross linking
4. complications
   * post injection flare lasting 1-3 days
   * rare pseudoseptic reaction, which can be characterized as inflammation and joint swelling not assocaited with infection

Question 180

what is the composition, MOA effectiveness, and complications of PRP injections

Answer 180

1. composition
   * prepared by centrifuging a blood sample which separates the blood allowing extraction of the platelel rich plasma
   * can be leukocyte-rich or leukocyte-poor
2. mechanism of action
   
   • platelets degranulate after injection releaseing growth factors resulting in:
     
     • decreased inflammation
     • stimulates chondrocyte and chondrogenic mesenchymal stem cell proliferation, promotes chondrocyte cartilaginous matrix secretion, and diminishes the catabolic effects of pro-inflammatory cytokines
3. effectiveness
   
   • compared with HA and saline, intra-artic PRP may have more benefit in pain relief and functional improvement in patients with symptomatic knee OA at 1 year post-injection
   • leukocyte poor may be more effective than leukocyte rich
4. complications
   - post-injection flare

Question 181

What are general considerations and preparation in revision TKA?

[Instr Course Lect. 2014; 63:239-51]

Answer 181

1. Rule out infection
   * a.History, physical, bloodwork (CBC, ESR, CRP), joint aspiration
2. Previous OR note

• a.Implants
• b.Approach
• c.Complications

3.Radiographs

• a.AP, lateral and full length standing
• b.Previous radiographs for comparison

4. Determine revision implants
   * a.Stems, augments, cones/sleeves, unconstrained, varus/valgus constrained, hinged, endoprosthesis
5. Surgical steps
   * See Separate Flashcard

Question 182

What are the surgical Steps for Revision TKA?

Answer 182

A.Skin incision

• i.Most lateral skin incision
• ii.Skin bridges >6cm
• iii.Avoid crossing previous incisions at angles <60°
• iv.Cross transverse incisions perpendicular

B. Approach

• i.Medial parapatellar preferred
  
  • 1.Generous release of the medial tibia to facilitate external rotation
  • 2.Release the medial and lateral gutters of scar tissue
  • 3.Release scar tissue between patellar tendon proximal tibia
• ii.`If difficult exposure
  
  • 1.Quadriceps snip (in medial, out lateral at 45def)
  • 2.Tibial tubercle osteotomy
    
    • a.Can assist with tibial stem removal
    • b.Medial to lateral, 5-8cm in length with 1cm bone bridge proximally, tapered distally, lateral soft tissue left intact to allow osteotomy to hinge open
    • c.Fixation at end of procedure with wire loops around fragment
  • 3.V-Y turndown

C. Poly liner removal

• Osteotome
• Drill, cancellous screw

D. Femoral component removal

• Oscillating saw and straight or curved osteotome used at implant-cement interface
• Punch and mallet

E. Tibial component removal

• i.Oscillating saw and straight osteotomes
• ii.Punch and mallet or stacked osteotomes to disengage tibial tray
• iii.Specialized extraction tools may be necessary

F. .Femoral or tibial stem removal

• i.If stem loose ensure if cemented that the bulk of the cement does not cause fracture with extraction (fracture cement mantle first)
• ii.If stem well fixed an anterior cortical trough can be created to debond – bypass with stem with revision

G.Cement removal

• i.Complete removal in septic cases; in aseptic cases well fixed cement may be left
• ii.Osteotomes, crochet hooks, burr, cement splitters

H.Patellar component removal

• i.Cemented poly buttons – use oscillating saw at cement-poly interface, cut through pegs and burr out pegs
• ii.Uncemented button – oscillating saw and metal cutting wheels to cut pegs

I.Sequence of reconstruction

• i.Rebuild the tibial platform
• ii.Measure the flexion and extension spaces and reconstruct the femur to equally fill those spaces
• iii. Implant selection depends on bone loss and ligamentous stability
  
  • 1. Bone defects
       * A. <5mm - cement alone
       * B. 5-10mm - cement and screw, bone graft, metal augments
       * C. >10mm - metal augments
       * D. Massive bone loss - cones, sleeves, structural allograft
  • 2.Ligamentous instability
    • A.Unconstrained – collaterals intact
    • B.Varus/valgus constrained – single collateral compromised
    • C.Hinged prosthesis – global instability, severe bone loss or deformity, flexion extension mismatch
  • 3.Stems
    
    • A. Generally required unless primary components used
    • B. Uncemented vs cemented