The 'over-the-top' technique allows for accurate and reproducible restoration of the native tibial slope in kinematically aligned total knee arthroplasty: A retrospective comparative analysis from the FP-UCBM Knee Study Group.

purposeA critical challenge in kinematically aligned total knee arthroplasty (KA TKA) is achieving accurate sagittal alignment of the tibial component. Correct reproduction of the native posterior tibial slope (PTS) is essential for proper posterior cruciate ligament (PCL) tensioning, minimising wear of the polyethylene insert while ensuring stability on dense subchondral bone. This study assessed the accuracy of manually setting the tibial slope in KA TKA, comparing the conventional technique with the novel 'over-the-top' technique, hypothesising that the latter would provide greater accuracy and reproducibility, even for less experienced surgeons.

methodsA retrospective analysis was performed on 81 patients (90 knees, 29 operated by a senior resident) using the conventional KA technique and 83 patients (90 knees, 32 operated by a senior resident) using the 'over-the-top' technique. The latter involves using an angel wing placed through the cutting slot of the tibial guide and over the anterior and posterior rims of the medial tibial plateau to set the PTS. Pre- and postoperative PTS were measured on lateral radiographs, and the PTS difference (PTSD) was calculated. Patients were classified as inliers (PTSD ≤ ±2°) or outliers (PTSD > ± 2°).

resultsMean pre- and post-operative PTS were 5.7 ± 3° and 6.4 ± 3.1° in the control group, and 5.6 ± 2.9° and 5.3 ± 2.9° in the study group. The study group had significantly lower mean PTSD (-0.3° ± 0.7°) compared to the control group (0.7° ± 2°; p < 0.001), with 0% and 25.5% outliers, respectively. Tibial recuts were required in 0% of cases in the study group and 15.6% in the control group (p < 0.0001), with differences between the lead surgeon (9.8%) and senior resident (27.6%).

conclusionThe 'over-the-top' technique provides superior accuracy and reproducibility in restoring the native PTS compared to the conventional KA technique and can be safely adopted even by less experienced surgeons. LEVEL OF EVIDENCE: Level III, retrospective comparative study.