Total Knee Arthroplasty

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Indications & Contraindications - Gatekeeping TKA

Indications:

  • Severe knee pain (often >6/10 VAS) with functional limitation, refractory to conservative treatment.
    • Primary Osteoarthritis (most common)
    • Rheumatoid Arthritis
    • Post-traumatic Arthritis
    • Avascular Necrosis (AVN) of knee
    • Failed conservative measures (analgesia, physiotherapy, intra-articular injections, unicompartmental knee arthroplasty)
  • Significant deformity (varus/valgus >15-20°)
  • Radiographic evidence of advanced arthritis (e.g., Kellgren-Lawrence Grade 3-4)

Kellgren-Lawrence (KL) grading scale for knee OA

Contraindications:

  • Absolute:
    • Active knee sepsis or systemic infection
    • Extensor mechanism dysfunction (e.g., patellar tendon rupture)
    • Severe vascular disease (PVD)
    • Neuropathic joint (Charcot knee) - relative to absolute depending on severity & stability
    • Recurvatum deformity due to muscular weakness
  • Relative:
    • Medical instability (uncontrolled comorbidities)
    • Obesity (BMI >40 kg/m²)
    • Young age (<50-55 years) - risk of earlier revision
    • Non-compliance with rehabilitation
    • Skin conditions over the knee (e.g., psoriasis)

Exam Favourite: Active infection in the knee joint is an absolute contraindication to TKA due to the high risk of prosthetic joint infection (PJI), a devastating complication requiring prolonged antibiotics and often multiple revision surgeries.

Pre-op Planning & Biomechanics - Blueprint & Balance

  • Pre-operative Assessment:
    • History: Pain, functional limitation, patient expectations.
    • Examination: ROM, deformity (varus/valgus), ligamentous stability, neurovascular status.
    • Optimize co-morbidities.
  • Radiographic Planning:
    • Essential X-rays: AP, Lateral, Skyline views.
    • Long leg films (scanogram): Crucial for mechanical axis & deformity assessment.
    • Templating: Component sizing, alignment, bone resection levels.
  • Biomechanical Goals:
    • Mechanical Axis: Restore to $\mathbf{0}^\circ \pm \mathbf{3}^\circ$ (Hip → Knee → Ankle).
    • Anatomical-Mechanical Angle: Femur approx. $\mathbf{6}^\circ$ valgus.
    • Joint Line Restoration: Critical for patellar tracking & mid-flexion stability.
    • Gap Balancing: Symmetrical, rectangular flexion & extension gaps.
    • Femoral Rollback: Ensure posterior femoral translation in flexion. Preoperative templating for TKA

⭐ Deviation from the target mechanical axis (neutral plus or minus three degrees) significantly increases polyethylene wear and risk of aseptic loosening.

Implant Design & Surgical Steps - Nuts, Bolts & Action

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Post-op Care & Complications - Recovery & Roadblocks

  • Immediate Post-op:
    • Mobilization: Weight bearing as tolerated (WBAT) from Day 0/1.
    • DVT Prophylaxis: LMWH/DOACs for 10-35 days. Intermittent Pneumatic Compression (IPC).
    • Pain Control: Multimodal analgesia (opioids, NSAIDs, regional nerve blocks).
    • Wound Care: Sutures/staples out at 10-14 days; monitor for discharge/erythema.
  • Rehabilitation:
    • Physiotherapy: Key for Range of Motion (ROM; target 0-120° flexion), quadriceps & hamstring strengthening.
    • Continuous Passive Motion (CPM): Use debated; may offer early ROM benefits.
  • Complications:
    • Early (<3 months):
      • Infection (Superficial Site Infection [SSI], Periprosthetic Joint Infection [PJI])
      • Deep Vein Thrombosis (DVT)/Pulmonary Embolism (PE)
      • Stiffness (Arthrofibrosis) - consider Manipulation Under Anesthesia (MUA) if <90° flexion by 6-12 weeks.
      • Periprosthetic fracture
      • Wound dehiscence/hematoma
    • Late (>3 months):
      • Aseptic Loosening (Most common cause of late failure)
      • Polyethylene Wear & Osteolysis
      • Late PJI
      • Instability
      • Patellofemoral pain/tracking issues

Post-op TKA X-rays: AP, Lat, Flex, Skyline

⭐ Mechanical axis alignment post-TKA within ±3° of neutral is critical for long-term implant survival and optimal function.

High‑Yield Points - ⚡ Biggest Takeaways

  • Osteoarthritis (severe, tricompartmental) is the most common indication for TKA.
  • Active knee sepsis and extensor mechanism dysfunction are key contraindications.
  • Femoral rollback is vital for deep flexion, facilitated by PS or CR designs.
  • Aim for neutral mechanical axis alignment () for implant longevity.
  • Patellar resurfacing is considered for anterior knee pain or patellofemoral arthritis.
  • Aseptic loosening is the most common long-term complication; PJI is a serious early one.
  • Cemented fixation is the gold standard, especially in older patients.

Practice Questions: Total Knee Arthroplasty

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The contraindication to internal fixation -

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Flashcards: Total Knee Arthroplasty

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Which muscle is used for girdlestone arthroplasty?_____

TAP TO REVEAL ANSWER

Which muscle is used for girdlestone arthroplasty?_____

Vastus lateralis

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