Individualised compared to off‐the‐shelf total knee arthroplasty results in lower and less variable patellar tilt

Purpose The purpose of this study was to compare postoperative patellar tilt at 4 months follow‐up in a consecutive series of randomised patients that received individualised or off‐the‐shelf (OTS) primary total knee arthroplasty (TKA). The hypothesis was that patellar tilt would be lower and less variable in patients who received individualised TKA compared to patients who received OTS TKA. Methods A consecutive series of 385 patients randomised (1:1) to receive either OTS TKA or individualised TKA were analysed. Pre‐ and postoperative radiographs at 4 months were obtained of weight‐bearing long leg, anterior–posterior and lateral knee views and a skyline view at 30° of flexion. Postoperative patellar tilt was measured between the anterior femoral line and patellar resection surface (β) and the anterior femoral line and mediolateral patellar axis (σ). Postoperative patellar tilt (absolute value) was compared between the individualised and OTS TKA groups based on preoperative phenotypes of their femoral mechanical angle, tibial mechanical angle and hip–knee–ankle angle. Variability in postoperative patellar tilt was compared using the 95% confidence intervals (CIs). Results Comparisons of baseline patient characteristics revealed no difference between the individualised and OTS TKA groups. Comparison of absolute postoperative patellar tilt revealed significant differences between individualised and OTS TKA (|β|, 1.0° ± 1.0° and 2.5° ± 2.2°, respectively, p