Total Knee Replacement – Valgus Knee

Definition of Valgus Knee

  • >10° of anatomic valgus

Aetiology

  • commonest cause is osteoarthritis.

Other causes:

  • Posttraumatic arthritis
  • Overcorrection of HTO
  • Unresolved physiological deformity
  • Rickets
  • Osteodystrophy

Epidemiology

higher incidence in

  • Inflammatory Arthritis
  • Posttraumatic arthritis
  • Overcorrection of HTO
  • Unresolved physiological deformity
  • Rickets
  • Osteodystrophy

Surgical Considerations

Problems with Anatomy Bony

  • Deficient Lateral femoral condyle
  • Deficient Lateral tibial plateau

Soft Tissue

  • Contracture of lateral structures
  • Laxity of medial structures

Problems intraoperatively

  • Exposure may be difficult
  • Obtaining proper alignment & component position
  • Difficult soft tissue balancing

Problems with Postop Complications

  • Tibiofemoral instability (2-70%)
  • Recurrent valgus deformity (4-38%)
  • Stiffness requiring manipulation (1-20%)
  • Wound problems (4-13%)
  • Patellar stress fracture or osteonecrosis (1-12%)
  • Patellar tracking problems (2-10%)
  • Peroneal nerve palsy (3-4%)

General Solutions

  • Enhance patient preoperatively
  • Thorough preoperative preparation

Alignment

Options

  • Epicondylar axis
  • Posterior referencing
  • Whitesides line

Problem

  • Abnormal anatomy (deformed posterior condyle) may make referencing inaccurate leading to internal rotation of femoral prosthesis & patella tracking problems

Solution

  • Use of the AP axis (Whiteside’s line)

Exposure

Options

  • Medial parapatellar
  • Lateral parapatellar

Medial Parapatellar:

  • Pros
    • often used & familiar
    • patellar eversion usually easy because of the valgus deformity & tibial tubercle is positioned even more laterally than normal
    • overall best approach
  • Cons

Lateral Parapatellar:

  • Pros
    • allows easy access to the lateral structures
  • Cons
    • poor access to the medial joint line (a tibial tubercle osteotomy may be necessary to gain access)
    • problems with wound closure
      • after division of contracted lateral structures there may only be skin & subcutaneous tissue left
      • This problem can be addressed by Z-cut capsulotomy or using the fat pad to cover the joint line

Bony architecture

Lateral bone deficiency

  • Deficiency of the posterior part of the lateral femoral condyle may lead to excessive internal rotation of femoral component when referencing off epicondylar axis or posterior condyles, leading to patellar maltracking
  • Deficiency of condyle
    • bone graft augmentation

Soft Tissue & Stability

  • Tight Lateral Structures
    • There is no consensus about the sequence in which structures around the knee should be released
    • structures commonly addressed are:
      • ITB
      • posterolateral capsule
      • LCL
      • Popliteal tendon
      • Lateral head of gastrocnemius
        • If the joint is tight only in extension,
          • release of the ITB or popliteus
        • If it is tight in flexion,
          • posterolateral capsule & popliteofibular ligament
  • Lax Medial Structures
    • Advancement of the MCL on the tibial side
    • Midsubstance imbrication of the MCL
  • Marked flexion contractures
    • More off distal femoral cut
  • Use of PCL substituting prosthesis