Manual instrumentation is associated with greater precision than patient-specific instrumentation for initial tibial resections in unrestricted kinematic alignment total knee arthroplasty: a comparative cohort study - 07/11/26

Doi : 10.1016/j.otsr.2026.104983

Charles Rivière ^a,^b,⁎ , Giuseppe Aloisi ^a,^c, Loïc Villet ^a,^b

^a Bordeaux Arthroplasty Research Institute (BARI), 6 rue Georges Negrevergne, 33700 Mérignac, France

^b Clinique du Sport Bordeaux Mérignac, 4 rue Georges Negrevergne, 33700 Mérignac, France

^c Università Degli Studi Dell’Aquila, Department of Life, Health and Environmental Sciences, 67100 L’Aquila, Italy

^⁎ Corresponding author.

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Abstract

Purpose

Accurate tibial resection is critical in unrestricted kinematic alignment total knee arthroplasty (uKA-TKA), as component positioning aims to restore the native joint line through anatomical resurfacing. This study compared the reproducibility of initial tibial resections performed with manual instrumentation versus patient-specific instrumentation (PSI) in uKA-TKA. The secondary objective was to compare tibial recut rates between techniques.

Methods

This retrospective comparative cohort study analyzed prospectively collected intraoperative measurements from 124 primary uKA-TKAs performed between June 2024 and January 2026. Tibial resections were performed using manual instrumentation in 83 cases and PSI in 41 cases. Target and measured tibial resection thicknesses were recorded intraoperatively at the medial (MTP) and lateral tibial plateaus (LTP) using an analog sliding caliper (0.5-mm resolution). Resection error (Δ) was defined as measured minus target thickness. Accuracy was expressed as mean signed error and precision as the standard deviation of signed error. Absolute error thresholds and tibial recut rates were also analyzed.

Results

Mean signed error did not differ significantly between techniques for either plateau (medial: 0.15 mm PSI vs −0.10 mm manual, p = 0.158; lateral: 0.10 mm PSI vs −0.05 mm manual, p = 0.378), indicating comparable average accuracy. However, medial precision was significantly greater with manual instrumentation (SD 0.64 mm vs 1.02 mm with PSI, p = 0.002), with lower mean absolute error (0.38 mm vs 0.73 mm; p = 0.007). Fewer medial resections exceeded the ±1.5 mm threshold in the manual group (2.4% vs 9.8%, p = 0.024). No significant differences were observed laterally. Angular tibial recut was performed in 12.0% of manual cases and 22.0% of PSI cases (p = 0.187).

Conclusion

Manual instrumentation and PSI achieved similar mean accuracy for initial tibial resections in uKA-TKA. However, manual instrumentation was associated, in this two-surgeon series, with greater medial reproducibility and fewer large resection deviations, with a numerically lower, non-significant recut rate. Within the sequential uKA workflow – including caliper verification and corrective recut when required – both techniques allow reliable convergence toward the predefined resurfacing target.