Knee

Knee arthrodesis and special patient groups

Arthrodesis indications, and knee replacement in haemophilia and post-polio paralysis.

21 questions 3 source pages

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Q1What are the indications for knee arthrodesis?▸

Q2What are the contraindications to knee fusion?▸

Q3What alignment should a knee arthrodesis be fixed in?▸

7 degrees valgus
15 degrees flexion
0-10 degrees external rotation (match the other leg)
On examination, tell pathological from surgical fusion by looking at alignment

Q4Compare plate, nail and external fixator for knee arthrodesis.▸

Plate: advantage allows compression; disadvantage extensive dissection
Nail: advantage load transmitting (increases healing and early WB); disadvantage difficult insertion
Ex Fix: advantage usable in poor soft tissue envelope; disadvantage pin tract infection

Q5What are the complications of knee arthrodesis?▸

Q6What are the key considerations when converting a fused knee to TKA?▸

Preop: extensor mechanism (clinical/EMG/MRI), contracted soft tissue envelope (expander), CT for bone stock, instruments (navigation, BG/augment, semiconstraint + stem)
Skin: choose most lateral wound, mainly full thickness fasciocutaneous flap
Bone stock: osteoporotic, hard to evaluate with hardware; +/- staged implant removal + bone graft; prepare BG/augment/stem
Soft tissue: shortened extensor mechanism --> quadriceps VY plasty; deficient collaterals --> semiconstraint; rotational flap for closure
Previous deformity

Q7Describe the X-ray features of haemophilic arthropathy.▸

Decreased joint space, OA change, osteopenia
Ballooning of distal femur (paediatric epiphyseal overgrowth), wide notch, squaring of femoral condyle
Squaring of patella (Jordan sign), no fracture
Large subchondral cyst
Pseudotumour
Ddx: OA, post-traumatic OA, post-infectious OA, inflammatory arthritis

Q8What is the Arnold-Hilgartner classification?▸

Q9Tell me about haemophilia.▸

Inherited disease of clotting dysfunction; most common type A (factor 8) and type B (factor 9), both X-linked recessive
Childhood onset of easy bleeding, usually at joints and intramuscular regions; mucosa less likely; affects hinged joints (knee, elbow, ankle)
Mild 5-25% / moderate 1-5% / severe <1% factor concentration determines bleeding risk
Recombinant factor transfusion in bleeding episodes (no blood-borne disease now)
Factor VIII inhibitors (including IgG antibodies) in 5-25% - inhibit response to therapeutic factor (monoclonal recombinant factor VIII); relative contraindication to surgery, screen preoperatively
Factor <1% --> spontaneous bleeding

Q10What is the pathology of haemophilic arthropathy?▸

Bleeding --> haemosiderin deposition --> synovitis --> bleeding
Repeated haemarthrosis --> capsular fibrosis
Articular damage (lyzosomal enzyme from synoviocytes) (lysosomal enzymes from synoviocytes)
Hyperemia --> LLD/ deformity (+/- overgrowth) (hyperaemia --> LLD/deformity)
Disuse: atrophy, contracture, osteopenia --> arthropathy

Q11What history and examination findings are important in haemophilia?▸

Hx: symptoms of bleeding/effusion, male or female, onset, previous medical follow-up, investigation, factor transfusion, complications of treatment
PE: joint effusion, ROM, deformity, gait (function)
Numbness in the L4 distribution caused by iliacus haematoma compressing the femoral nerve

Q12What investigations are needed in haemophilia?▸

Blood test: Hb, aPTT prolonged, PT normal
Bethesda assay measures factor 8/9 antibody (megadose/ neutralize)
Preop workup: factor transfusion, cell saver, check inhibitor IgG, HIV testing

Q13What is the aim and conservative management of haemophilic joint disease?▸

Systemic: refer haematologist for bleeding control (regular/symptomatic transfusion)
Aim: preventive - decrease bleeding episodes, prevent soft tissue contracture, deformity and ankylosis
Conservative: analgesics + physiotherapy
Prophylactic factor replacement >2%

Q14How are bleeding episodes and surgery managed in haemophilia?▸

Acute haemarthrosis: aspiration, factor infusion aim 40-50%, splint/compressive dressing, +/- steroid, early rehab
Recurrent: aspiration, factor VIII >20% for 6 weeks, IA steroid, cast; desmopressin
Chronic stage 1-3 (joint space preserved): synovectomy, radioactive synoviorthesis with colloidal 32P chromic phosphate
Chronic stage 4-5: arthrodesis / TKR (higher infection rate)
Skeletal surgery: factor to 100% in 1st week, keep >50% in 2nd week
Targets: vigorous physiotherapy 20%; acute haematoma 30%; acute haemarthrosis / soft tissue surgery 40-50%

Q15What are the difficulties of TKR in haemophilia?▸

Pre-op: factor transfusion, cell saver, check inhibitor IgG, HIV testing
Intra-op soft tissue: contracture, easy bleeding
Intra-op bone: soft bone easy fracture, bone graft cysts, large femoral epiphysis (difficult sizing), small IM canal, valgus knee, tibia posterolateral subluxation + decreased slope, thin patella
Post-op: factor transfusion to cover (1 week 100%, 2 weeks >75%), haematoma formation

Q16What is the prognosis of TKR in haemophilia?▸

J Arthroplasty meta-analysis 2022 Fenelon: overall complication rate 28.7%
Similar survivorship to the general population

Q17What is the pathogenesis of knee deformity in polio?▸

Weak quads with failed knee extension in stance phase
Hyperextension of the knee to bring the ITB anterior to the knee centre of rotation, acting as an extensor
Gradual stretching of the posterior capsule
Weight bearing and gravity elongate the tibial condyles posteriorly
Articular surface angle to the tibial axis becomes more acute; proximal third of tibia bows posteriorly

Q18What bone problems complicate TKR in polio patients?▸

Q19What soft tissue problems complicate TKR in polio patients?▸

Q20How is recurvatum addressed during TKR in polio?▸

Exposure limited by patella baja: lateral retinacular release, medial soft tissue release, quads snip / TTO
Extension gap: cut less distal femur
Flexion gap: small component to increase flexion gap
Constraint

Q21What is the reported outcome of TKR in polio patients?▸

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