The impact of soft tissue release on radiological and clinical outcomes in functional alignment robot-assisted total...

To assess the impact of soft tissue release (STR) on radiological and clinical outcomes in functional alignment robot-assisted total knee arthroplasty (FA-TKA).

This retrospective controlled study enrolled a total of 127 patients who underwent Mako robot-assisted FA-TKA. Based on whether soft tissue release was performed, patients were categorized into an STR group (n = 38) and a non-STR group (n = 89). Radiographic parameters, including the hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), and posterior tibial slope (PTS), were assessed. Knee function was evaluated using the Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) preoperatively and at 3 and 6 months postoperatively.

STR was required in 50% of knees with valgus deformity and 28.9% of knees with varus deformity. Rates increased significantly with deformity severity: 0% for varus < 10°, 62.5% for varus ≥ 10°, 95.8% for varus ≥ 15°. In knees with varus deformity, 68.6% medial collateral ligament (MCL) and 94.3% posterior cruciate ligament (PCL) were most commonly released; iliotibial band (ITB) release was universal in knees with valgus deformity requiring STR. Preoperative HKA and MPTA were significantly lower, while mLDFA was higher, in the STR group compared to the non-STR group (all P < 0.05). Postoperatively, HKA remained lower in the STR group compared to the non-STR group. There were no significant differences between groups in postoperative mLDFA, MPTA, PTS, or in KSS and WOMAC scores at any time point. Notably, the magnitude of correction in HKA and MPTA was greater in the STR group.

During FA-TKA, STR is commonly employed to achieve soft tissue balance in cases of severe varus (≥ 10°) or knees with valgus deformity. In knees with varus deformity, the most frequently released structures are the MCL and PCL, whereas in knees with valgus deformity, release predominantly involves the ITB. However, intraoperative STR did not significantly impact postoperative lower limb alignment or short-term clinical outcomes compared to no release. The decision to perform STR should be individualized based on the type and severity of preoperative deformity.