Alterations in native coronal alignment in Asian osteoarthritic knees following four total knee arthroplasty alignment techniques

BackgroundThis study aimed to compare the impact of mechanical alignment (MA), anatomic alignment (AA), kinematic alignment (KA), and restrictive KA (rKA) on native coronal alignment in Asian osteoarthritic knees undergoing total knee arthroplasty (TKA). It also assessed the proportion of KA patients requiring rKA adjustment and compared early postoperative function between the two.MethodsA retrospective analysis of 700 knees involved measuring lateral distal femoral and medial proximal tibial angles on long-leg radiographs. Coronal plane alignment of the knee (CPAK) classification was determined using the arithmetic hip-knee-ankle angle and joint line obliquity (JLO). Simulations of MA, AA, KA, and rKA were performed to observe changes. The proportion of patients requiring adjustment to the rKA safe range was recorded. Postoperative functional scores at 1 year were compared between KA and rKA groups.ResultsKA preserved native coronal alignment entirely. MA and AA altered constitutional alignment in 71.1% and 71.7% of cases, respectively, versus 8.9% for rKA. CPAK classification changed in 91.7% (MA), 80.0% (AA), and 31.7% (rKA) of cases. Only 31.9% of patients fell within the rKA safe range without adjustment; 68.2% required corrective osteotomy. No significant difference in 1-year functional scores was found between KA and rKA groups.ConclusionsKA preserves native alignment, while rKA causes the least alteration among alternative techniques. Early functional outcomes are similar, though most patients require adjustment to meet rKA's safe coronal alignment boundaries.