MEMORIZE ARTHROPLASTY Flashcards
THA revision principles
THA revision
Preop
1 Rule out infection
2 Obtain old OR note and be familiar with components in situ
3 Follow previous skin incisions if possible
On the back table I will need tools to retrieve the current prosthesis, and revision components.
Tools for revision include
1 Any implant specific extraction tools (identify after speaking to rep, have old OR note)
2 Tools for removing cement = Curettes, osteotomes, flexible osteotomes, hooks, OSCAR, ETO
3 Tools for removing acetabulum = Explant, flexible osteotomy, screw driver
4 Tools for removing poly = small frag screw, corkscrew, drill bit, ream
Revision components
1 Femur
a Long fully porous coated diaphyseal fitting femoral revision stems
b Modular stems
c Fluted stems
d Cortical struts available
2 Acetabulum
a Highly porous coated hemispheric cups
b Revision cups
c Trabecular metal cups
d Jumbo cups
e Acetabular augments
f Constrained liners
g Cup/cage, triflange, antiprotrusio cages depending on scenario
3 Extras- Cerclage wires, proximal plates
TKA revision principles
TKA revision
Preop
1 Rule out infection
2 Obtain old OR note and be familiar with components in situ
3 Follow previous skin incisions if possible
4 Have extraction explant tools, high speed burrs, trephines, oscillating saws, curettes, and flexible
osteotomes available as well has a cement retrieval tool (ie Oscar).
5 In terms of implants I will have stemmed prostheses, sleeves, cones, and bulk structural allograft
and constrained prostheses available.
General plan
1 Develop the bone cement/implant interface
2 Preserving as much bone as possible
3 Atraumatic extraction of the prosthesis
4 Assess and manage bone loss, and incompetent of collateral ligaments
5 Reconstruct the joint with stemmed prostheses using as little constraint as possible, restoring a
stable joint line, length alignment and rotation of the limb.
DDH in adult deformity
- deformities
- Crowe classification
- Hartofilakidis
- radiographic parameters to measure dysplasia:
Acetab: shallow, hypoplastic (anterolateral/superior deficient), anteverted
Femur: Small head, short + anteverted neck, coxa valga, posterior GT, small canal
Grade 1 – Prox displacement < 10%, head subluxed < 50%
Grade 2 – prox displacement 10-15%, head subluxed 50-75% - roof deficient
Grade 3 – prox displacement 15-20%, head subluxed 75-100% - roof absent
Grade 4 – High riding – prox displacement >20%, head subluxed >100%, superior lip of acetab absent
Type A: Dysplasia – head within acetab, deficiency of superior wall, shallow
Type B: Low dislocation – false acetab superiorly, absent superior wall, shallow
Type C: High dislocation – femoral head completely uncovered – migrated superior/posterior
AP: LCEA <20; Tonnis angle >10 degrees
False profile (patient in the standing position and with an angle of 65° between the pelvis and the film): ACEA <20
THA in DDH
Approach; considerations
high vs true hip center
methods to find true acetab
steps
complications
Approach:
Posterior – able to identify sciatic nerve (deep to piriformis + superficial to SERs – best at quad fem), spares abductors, can do shortening osteotomy easily
**Troch slide **– gives better access to hip joint, can distalize abductors to enhance abductors, maintains SERs + posterior capsule – lowers dislocation risk
Soft tissue releases: Adductor tenotomy (if tight), glute max
Tight adductors, flexors – may need releases; Difficult dislocation – may need insitu neck cut, aberrant course of femoral nerve/profunda, horizontal abductors
Acetab - goal restore true acetab (can accept high position if needed)
High hip center – technically easier (don’t have to locate acetab, no shortneing), no bone graft, lower risk to nerve
Cons: Limp, increased dislocation rate (impingement), increased JRF/loosening, have to use small components
Normal hip center – Decreased limp (can maximize muscle tension), lower dislocation rate, larger components (better wear), restores LLD
Cons: Technically demanding (locate acetab, shorten femur), bone graft, higher risk to nerve with lengthening
Finding true acetab – 3 methods
Ligamentum teres (inside of capsule)
Intraoperative XR with reamer in true acetab
TAL, pulvinar
Consider pre-drilling medial wall to determine depth before reaming + reverse ream (soft bone)
May need smaller components - aim for cementless with screw fixation
Need about 70% coverage (can get away with less if TM cup)
Bone graft: for superior augmentation in CROWE 3-4 superolateral shelf graft (flying buttress) or Augments + TM cup
Options: Autograft/allograft femoral head – fix with 2-3 large fragment screws
Roof ring if too medial (place bone graft medially behind ring)
Femur – try to determine preop how much lengthening required - >3cm carries risk to sciatic nerve (10% femur)
Max 4 cm, can monitor with outrigger devide
Modular (wagner) stem to accommodate for increased anteversion/anterior bow
Smaller femoral component for narrow canal + smaller femoral head
Ideal to use cementless fixation with distal porous coat
Femoral neck cut at LT + psoas/adductor release
Shortening osteotomy – ream and broach the femur distally greater than amount to be shortened
Then** make subtroch osteotomy** – mark rotation with cautery first – transverse osteotomy
Place trial component in the proximal segment and reduce the hip, if irreducible – cut more
Determine overlap of osteotomy sites – create 2nd transverse osteotomy
**Place prophylactic wire distally **– reprepare the distal femoral segment + then retrial
CX:
Nerve injury
PACU – flex knee and extend hip (consider exploring nerve + further shortening if overlengthen), dislocation , troch nonunion = 10-25%, ST osteotomy nonunion (<10%), fracture, loosening, LLD, limp, infection
radiographic parameters to measure dysplasia:
AP: LCEA <20; Tonnis angle >10 degrees
False profile (patient in the standing position and with an angle of 65° between the pelvis and the film): ACEA <20
definition of coxa profunda vs acetab protrusio
types/causes
surgical principles
- Coxa profunda: Acetabular fossa is at or medial to ilioischial line
- Acetab protrusio: femoral head is at or medial to ilioischial line
Types:
* Primary/Idiopathic: Otto Pelvis – arthrokatadysis – young females
* Secondary:
* Infectious: Gonococcal/Staph/Strep/TB
* Neoplastic: Hemangioma/Mets/NF
* Inflammatory: RA/AS/JRA/PA/
* Metabolic: Pagets/OI/Ochronosis/Hyperthyroid
* Traumatic: Acetab fracture
* Genetic: Stickler, EDS, Marfans, Sickle cell, CMT, Tri 18
Surgical principles:
* If skeletal immature: triradiate closure/valgus intertroch osteotomy
* Difficult to remove femoral head: In-situ neck cut vs. remove piecemeal
* Place new hip center in anatomic location – more lateral + inferior to restore joint biomechanics — Use intraop XR or relationship of prosthesis to remaining acetab rim; this lengthens the leg (consider low femoral neck cut with extended offset)
- High rate of failure if new hip center is >10mm from anatomic
- Use intact peripheral rim of acetab to support component
- Do not ream the medial wall, ream peripherally – make walls convergent
- Bone graft medial wall (cancellous bone/graft from head)
- Sciatic nerve may be closer to joint than normal
- Troch osteotomy if difficult exposure
- TM cup if no bleeding bone
