Intentional asymmetric balancing in robotic‐assisted valgus TKA: Early outcomes and intraoperative laxity changes
Stefano G. Petrillo, Damiano Ardiri, Matteo Marullo, Giampaolo Giordano, Sergio RomagnoliAbstract
Purpose
To evaluate early patient‐reported outcome measures (PROMs), radiographic alignment changes, intraoperative laxity changes and complications in a retrospective series of constitutional valgus knees treated with robotic‐assisted total knee arthroplasty (TKA) using an intentional asymmetric balancing strategy and a semi‐personalized (SP) alignment technique.
Methods
This retrospective single‐centre cohort included consecutive patients with end‐stage valgus osteoarthritis (OA) and constitutional valgus morphotypes (coronal plane alignment of the knee III/VI) treated with imageless robotic‐assisted TKA and a minimum follow‐up of 12 months. The balancing workflow intentionally accepted mild residual lateral laxity. Medial and lateral compartment laxity (mm) were quantified intraoperatively at 0° and 90°. PROMs (Knee Society Score [KSS] and Forgotten Joint Score [FJS]), range of motion (ROM) and hip–knee–ankle angle (HKA) were assessed preoperatively and at the latest follow‐up. Complications were recorded.
Results
Fifty‐eight patients were included at a mean follow‐up of 26.5 ± 15.0 months. KSS Knee improved from 58.3 ± 9.4 to 87.9 ± 11.0 (mean change +29.6 points, 95% confidence interval [CI] = 26.0–33.2; p = 0.00002) and KSS Function from 58.8 ± 15.0 to 82.4 ± 15.7 (mean change +23.6 points, 95% CI = 18.8–28.4; p = 0.00004). Flexion contracture improved from 3.9 ± 4.0° to 0.6 ± 1.2° (mean change −3.3°, 95% CI = −4.3 to −2.3; p = 0.00010), while flexion increased from 101.4 ± 6.0° to 126.8 ± 8.6° (mean change +25.4°, 95% CI = 23.2–27.6; p = 0.00001). HKA improved from 6.2 ± 4.5° valgus to 2.1 ± 1.8° valgus (mean change −4.1°, 95% CI = −5.2 to −3.0; p = 0.00030). Lateral laxity decreased in extension from 4.5 ± 1.7 to 2.5 ± 1.3 mm (mean change −2.0 mm, 95% CI = −2.7 to −1.3; p = 0.001) and at 90° from 5.3 ± 2.0 to 1.9 ± 1.2 mm (mean change −3.4 mm, 95% CI = −4.3 to −2.5; p = 0.0008), with smaller medial reductions. Post‐operative complications occurred in four patients (6.9%) (deep vein thrombosis, transient peroneal neuropraxia, superficial wound issue and one manipulation under anaesthesia); there were no pulmonary emboli, periprosthetic joint infection or revision procedures.
Conclusion
In this retrospective single‐surgeon series of constitutional valgus knees treated with robotic‐assisted TKA, intentional asymmetric balancing was associated with good early clinical outcomes, correction towards less valgus alignment, and a reproducible reduction in lateral laxity, with a low complication rate. These findings support the feasibility of this measurable laxity‐guided strategy, but do not establish superiority over alternative balancing philosophies.
Level of Evidence
Level III, retrospective cohort.