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Table 1

Functional positioning protocol guidelines in lateral unicompartmental knee arthroplasty [HKA: hip-knee-ankle angle; JLO: joint line obliquity; CPAK: coronal plane alignment of the knee].

Parameter Target
Final coronal alignment (HKA) 180°–185°
Final sagittal alignment with gravity only 0° ± 5°
Femur
 Varus/valgus Femoral resurfacing aims to obtain centered contact points between the femoral and tibial implants throughout the full range of motion
 Flexion
 Rotation
Tibia
 Varus/valgus 0°–3° valgus
 Slope 0°–12°
 Rotation Alignment of the implant’s lateral edge with the lateral cortex axis of the lateral femoral condyle
 JLO and height Preservation of the JLO orientation
Final joint line height ±2 mm from native
 Balancing 0–2 mm of final lateral laxity
Goal:
  • 0–1 mm in extension

  • more laxity in flexion (up to 3–4 mm) in order to restore the native lateral flexion gap

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