Reduced knee adduction moments in bicruciate-retaining total knee arthroplasty compared with bicruciate-substituting designs: A contralateral within-patient study

BACKGROUND: This study compared frontal-plane knee loading during gait between bicruciate-retaining total knee arthroplasty (BCR-TKA) and bicruciate-substituting TKA (BCS-TKA) using a contralateral within-patient design. METHODS: Twenty-five patients undergoing simultaneous bilateral TKA received BCR-TKA in one knee and BCS-TKA contralaterally. The final implant selection was determined intraoperatively based primarily on anterior cruciate ligament integrity and functional preservability. Postoperative radiographs were obtained within 1 week before gait analysis, performed 287.4 ± 160.6 days after surgery (range, 109-739 days). The primary outcome was the first peak knee adduction moment (KAM). Secondary outcomes were the second peak KAM and the KAM impulse. Linear mixed-effects models were adjusted for postoperative hip-knee-ankle angle (HKA), joint-line obliquity (JLO), and stance-phase knee varus angle. RESULTS: Postoperative HKA (3.24 ± 3.1° vs. 3.50 ± 3.4°; P = 0.767) and JLO (178.33 ± 4.8° vs. 178.03 ± 5.0°; P = 0.757) were comparable between BCR-TKA and BCS-TKA. Adjusted first peak KAM was lower with BCR-TKA (BCS-BCR difference, 0.052 Nm/kg; 95% confidence interval, 0.011-0.094; P = 0.014), as was second peak KAM (difference, 0.035 Nm/kg; 95% confidence interval, 0.002-0.068; P = 0.038). KAM impulse did not differ significantly (P = 0.128). All patient-reported outcomes were comparable; Forgotten Joint Score-12 was 24.4 ± 10.7 vs. 25.6 ± 12.0 (P = 0.287). CONCLUSION: BCR-TKA was associated with lower first and second peak KAMs despite similar postoperative alignment, whereas KAM impulse and patient-reported outcomes were comparable between the implant designs.