TKA Flashcards
What is the anatomic relationship of the popliteal artery in the back of the knee in relation to distance from posterior aspect of tibia in flexion and popliteal vein?
In knee flexion - 9 mm from posterior aspect of tibial plateau and ANTERIOR to the popliteal vein (just think - we don’t really talk about hitting the popliteal vein b/c first thing you hit is the artery!)
Varus alignment of the knee results in what force moment about the knee?
Increased adductor moment
Which osteotomy around the knee causes a DECREASE in posterior tibial slope?
What age group of patients should osteotomies be considered in?
Lateral closing wedge tibial osteotomy
Typically active, < 45 yo w/ unicompartmental dz
What is the surgical treatment on the ABOS exam for isolated PFA?
TKA!
Name the 5 DMARDs which can be continued through surgery.
Can steroids be continued through TJA surgery?
Methotrexate Hydroxychloroquine Leflunomide Sulfasalazine Doxycycline (To remember: "Must Have Less Shitty Dz")
Yes! Continue steroids! No stress dose needed for patients taking 16 mg/day or less!
What is the rule for use of biologic agents around time of TJA? And how does this relate to surgical timing?
STOP ALL BIOLOGIC AGENTS (-mab, -ib, etc.) PRIOR TO SURGERY!
Schedule surgery at end of dosing cycle + 1 week.
EXCEPT Tofacitinib -> stop 1 week before surgery (has very short 1/2 life)
When can biologic agents be restarted after TJA?
After wound healing/all sutures/staples removed! ~ 14 days
What is the rule regarding continuation/discontinuation of immunosuppressant meds for severe SLE ( = with organ involvement)?
What is the rule regarding this for non-severe SLE (= w/o organ involvement)?
Severe SLE: CONTINUE all meds perioperatively!!
B/c risk of organ damage»_space; risk of infection!
Non-severe SLE: DISCONTINUE all meds 1 week prior to surgery and RESTART 3-5 days after surgery if wound healing is going okay.
What is the timing for stopping blood thinners/anti-coagulants/NSAIDS prior to TJA?
1 week
Which patient population has been shown to have less improvement after TKA compared to others after TKA?
Obese patients have less improvement in outcomes with TKA compared to others
What axis are femoral and tibial cuts made perpendicular to?
What is maximum amount of jointline change that can occur before kinematic conflict due to change of center of rotation?
Perpendicular to the MECHANICAL AXIS.
8 mm (raise or lower)
What is the differential release on the medial side of the knee (ie to give more laxity in flex vs ext or vice versa)?
How about lateral side?
Medial side: superficial MCL (release more anterior if flexion needed, more posterior if extension needed).
Lateral side: Popliteus if need more flexion/ IT if need more extension (to help remember: know that your IT is tight in ext…think about Ober test!!…or just remember that POP is DAD..and the A is for anterior structure..)
Note: LCL gives a balance fle/ext release
Which is more problematic: extra-articular coronal deformity near or far from the joint? Why?
How do you deal with extra-articular coronal deformity?
Deformity CLOSER to the joint is more problematic b/c larger bone cuts are required in order to cut perpendicular to the mechanical axis -> and these will often directly compromise ligament insertion and/or make you compromise other ligaments in order to balance.
McPherson 1/4 Rule: if w/in 1/4 of joint (so 1/4 distal femur or 1/4 of proximal tibia) and 20 degrees or more of deformity -> NEED AN ADDITIONAL OSTEOTOMY TO FIX IT.
If have less than 20 degrees in the sagittal or coronal plane then you can correct this with your intra-articular cuts.
Fill in the following:
X mm of distal bone resection gives Y more degrees of flexion
2 mm
10 degrees
If have a tight flexion gap in a CR knee - what ligament can be released (different from PS knee) to help with this?
Anterior portion of PCL!
How should anti-coag ppx be changed for Factor V Leiden?
Nothing to change!
What is diff b/t femoral nerve block vs adductor nerve block? What do they both NOT cover?
Femoral = motor & sensory (can fall after surgery!! Knee buckles, so need KI)
Adductor = sensory only! (saphenous and articular branches to vastus medialis)
Neither give posterior capsule pain contol -> so get this intraop with posterior capsule block!
What is the cause of early postop flexion contracture in a patient that you had good ROM in OR?
Hamstring spasm! Put pillow under foot!
What is the major blood supply to the patella (and it’s always cut during TKA)?
After typical TKA what is the source of remaining blood supply to the patella?
Major blood supply -> Inferior medial genicular artery (always disrupted w/ approach and removal of retropatellar tendon fat pad)
Remaining -> Lateral superior genicular artery (can be hit and get patella AVN if you do a lateral retinacular release!)
What is minimum thickness that bony patella can be?
12-13 mm
What are the 2 main options if intraop cut the MCL?
- ) Convert to revision prosthesis w/ high post
2. ) Primary repair of MCL w/ a ROM knee brace worn for 6 weeks unlocked to allow full ROM
What do you do if you have an extensor mechanism disruption (MC patellar tendon avulsion from tibial tubercle)?
Only 1 option -> extensor allograft reconstruction
How do you treat early stiffness vs late stiffness?
Early (< 3 months): MUA
Late -> if can figure out the reason then do a revision and fix the maligned component! Note: an arthrotomy, scar removal, and smaller polly is NOT recommended b/c high failure rate!
Most common metal allergy seen in TJA?
What type of hypersensitivity rxn is it?
What test DOES work and what test DOES NOT work to tell who might get this?
Nickle (followed by Co/Chr) - incidence is 1%
Delayed Type IV
Works: Lymphocyte T Cell proliferation test
DOES NOT work: Skin patch test
What problem/wear is seen in CR knees due to retention of PCL?
Sliding wear - w/o ACL the femur slides anterior in the beginnning of flexion
What can cause a CAM jump in a PS knee?
Loose flexion gap (ie accidentally cutting the popliteus!)
What is patella clunk syndrome? Treatment?
What factors contribute to it?
Scar tissue superior to patella on back of quad tendon forms and gets caught in the box w/ knee extension. Tx -> open or arthroscopic removal.
Risk Factors:
1) MOST = wide and/or tall femoral box! (Quad tendon rubs on box and forms scar!)
2) Just reason yourself through anything that causes a low patellar height or patella pulled lower down (ie. small patella implant, thin patella, baja, increased posterior condylar offset)
3) Also, people who have had previous knee surgery - “scar begets scar”
What causes anterior post wear in a PS knee?
- ) Net hyperextension of knee components = flexion of femoral component/increased posterior slope of tibia
- ) Knee hyperextension (due to soft tissues)
- ) Anterior translation of tibial component
In what situations are CR knee’s not to be used? (must use PS)
- ) Patellectomy
- ) Inflammatory arthritis
- ) Hx of trauma to PCL (attenuation or rupture)
What can happen if you have a rotating platform and loose flexion gap?
Bearing spin out!
Will need open reduction - and correction of loose flexion gap!
What is a downside of modular poly (that we always use?)
Backside wear
What is the indication for a hinged knee replacement?
- ) Hyperextension deformity
2. ) “Global instability”
What are constrained options for TKA?
- ) High tibial post (non-hinged)
- ) Hinge w/ rotating platform (note: uniplanar hinge IS NOT used really - too much stress at cement/bone interface!)
* *Also note: A PS IMPLANT AND PS+ ARE NOT CONSTRAINED IMPLANTS!
What are indications for a constrained TKA? (high post or hinge?)
- ) Residual flexion gap laxity that you cannot balance!
- ) MCL/LCL deficiency
- ) Charcot
Where else can knee pain come from that we must remember?
Check the hip and spine!!!
What is the #1 reason for early failure of TKA (failure in first 2 years)?
Infection
What are the numbers for aspiration of a chronnic infection? (WBCs & % neutrophils)
For acute?
Chronic:
WBC > 3,000
Neutrophils > 70%
Acute:
WBC > 10,000
Neutrophils > 90%
How long should PE last in a well-balanced knee on average?
13-15 years!
PE bearing failure at 5-7 years is worrisome! Don’t just blame patient activity….likely technical error!
If there are multiple longitudinal incisions over knee - which one should be used?
MOST LATERAL (since all of the blood supply comes mostly from medial!)
What is the relation of the jointline to the fibular head?
1.5 cm
How long is biofilm bacteria in its G0 phase?
6 weeks - this is why we use this length of minimum abx treatment!!
What do you do if you get a positive culture when you are doing a revision for what you thought was aseptic?
basically just think that you did single stage -> carry on an treat with 6 wks IV abx and monitor them
What is recommended for periop abx?
30 min prior to incision AND 24 hrs after
What is the main source of FLAP coverage for soft tissue problems around the knee? What is the blood supply?
Medial Gastroc FLAP -> medial sural artery
*Lateral Gastroc FLAP only used for lateral defects - poor excursion and if pull too tight get peroneal nerve palsy!
What is the treatment for Fungal PJI?
ALWAYS a 2 STAGE! + long-term anti-fungal: -azoles (TRIAZOLE); or Amphotericin (but this is more toxic and there is no oral version)
What is the MoA of anti-fungals?
Disrupts cell wall synthesis
Besides malrotation/translation of components - what can be 2 other causes of lateral patellar maltracking intra-op?
- ) Tourniquet
2. ) Overstuffing patella
What is the thinnest that a PE insert can be?
8 mm!
Any thinner than this and get catastrophic failure
AAOS Practice Guideline for Treatment of OA:
Recommended Conservative treatments (2)
- ) Self-management programs
2. ) Weight loss when BMI >25
AAOS Practice Guideline for Treatment of OA:
NOT Recommended Conservative treatments (3)
- ) Acupuncture
- ) Lateral wedge insoles to offload medial compartment dz
- ) Glucosamine & Chondroitin
AAOS Practice Guideline for Treatment of OA:
Recommended Pharmacologic treatment (2)
- ) NSAIDS
2. ) Tramadol
AAOS Practice Guideline for Treatment of OA:
Recommended Surgical treatment (1) (other than arthroplasty)
High tibial osteotomy
AAOS Practice Guideline for Treatment of OA:
NOT Recommended Surgical treatment (2)
- ) Arthroscopy w/ lavage and/or debridement
2. ) Free floating spacer
AAOS STRONG Evidence Recs for Surgical Management Practices related to TKA regarding: Periop Management (4)
- ) If no contraindications, TXA (topical or oral) decreases postop blood loss and reduces need for postop transfusions.
- ) Supports NOT using intraop navigation b/c no diff
- ) Supports NOT using patient specific instrumentation b/c no diff
- ) Supports NOT using a drain b/c no diff
AAOS STRONG Evidence Recs for Surgical Management Practices related to TKA regarding:
Periop Pain Management (3)
- ) Use of periarticular pain injection decrease pain and opioid use
- ) Peripheral nerve block decreases postop pain and opioid requirement
- ) Use of tourniquet INCREASES postop pain
AAOS STRONG Evidence Recs for Surgical Management Practices related to TKA regarding: Periop Rehab (2)
- ) CPM does NOT improve outcomes
2. ) Same day of surgery rehab starts on day of TKA and reduces length of hospital stay
AAOS STRONG Evidence Recs for Surgical Management Practices related to TKA regarding: Implant Design (4)
- ) No diff b/t PS or CR
- ) No diff b/t all poly or modular tibial components
- ) No diff in pain or fxn w/ or w/o patellar resurfacing (but higher incidence of anterior knee pain and need for revision w/ non-resurf patella…though the revision tends to make no diff in the anterior knee pain)
- ) Similar fxn outcomes and complications in tibial fixation that is cemented or cementless
What are the 4 main contraindications to UKA?
- ) Inflammatory arthritis
- ) Arthritis in more than one compartment!
- ) Uncorrectable deformity on preop exam
- ) Flexion contracture > 10 degrees
How to manage supracondylar periprosthetic femur fx if:
- ) implant loose
- ) implant stable
- ) highly comminuted fx in elderly
- ) Revise + ORIF
- ) ORIF - lateral locked plate
- ) DFA
What is MC cause of peroneal nerve palsy postop? And what should you always do?
Most common deformity to see peroneal nerve palsy postop in?
Aberrant retractor placement.
But always take tension off of the nerve when you see this (regardless of what you think mechanism was) by taking off any compressive dressing and flexing the knee.
Valgus/Flexion deformity
What is the pathway of osteolysis due to PE?
Macrophage initiates
Cytokines released -> TNF-alpha, IL-1beta IL-6
RANKL produced (by osteoblasts)
RANKL -> RANK on osteoclast -> bone resorption -> see round lytic lesions!
What structure primarily balances out the medial side of the knee in extension?
Posterior oblique ligament
What type of metal implant is most susceptible to pitting corrosion?
Stainless Steel (A316L)
What is the synovial fluid WBC cut off that suggests infection in the perioperative period? (up to 6 weeks after surgery date)
> 30,000 suggests infection
When compared to locked plating vs retrograde IMN for displaced periprosthetic distal femur fractures what has been seen?
Locked plating has been shown to demonstrate an increased trend toward nonunion compared to rIMN
Which biomaterial has the highest rate of bacterial adherence?
Lowest?
Highest -> Titanium
Lowest -> Tantalum
