High-precision universality? A matched-pair sawbone study on the learning curve, accuracy, and implant...

Robotic-assisted unicompartmental knee arthroplasty (UKA) improves implant positioning over conventional techniques, but commercial systems commonly bind the robotic platform to a single implant manufacturer, restricting clinical flexibility. Open-platform systems offer a vendor-neutral alternative, yet their effect on novice execution precision and workflow stability during implant switching remains insufficiently characterized.

A prospective exploratory matched-pair case series was conducted on standardized synthetic bone models (Sawbones). Two robotic-naïve medical students, after identical training and baseline assessment, each performed 20 consecutive robotic UKA procedures on the ROPA open-platform system (Beijing Changmugu Medical Technology). Operator A used a single implant (Sigma HP Uni, DePuy Synthes); Operator B alternated between two manufacturer-specific workflows (DePuy Synthes; Kangernuo Medical). Because each condition included only one operator, observed differences reflect combined operator- and workflow-related factors that cannot be disentangled. Learning curves were assessed by Cumulative Sum (CUSUM). Three-dimensional resection accuracy was quantified by high-precision laser scanning. Overall perceived workload was assessed with NASA-TLX.

The precision CUSUM oscillated around zero for both operators (peak amplitudes +0.30 and -0.54 mm), indicating sub-millimeter accuracy from the first case without a detectable learning phase. All 40 cases fell within the ±1 mm safe zone (P > 0.05 across resection depths). Tibial valgus deviation was greater in Operator B (1.74° ± 1.33° vs. 0.97° ± 0.96°; P = 0.028, Wilcoxon signed-rank test), and the mean deviation of both operators remained below the ±2° degree threshold. Operator B reached the operative-time inflection point earlier (Case 5 vs. 10) and reported lower NASA-TLX workload (32.05 ± 25.60 vs. 38.35 ± 23.72, P = 0.010); this difference cannot be attributed to workflow alone.

Under sawbone conditions-which cannot reproduce soft-tissue balancing, bleeding, anatomical variability, patient-specific deformity, or intraoperative decision-making-this two-operator exploratory evaluation found no evidence of compromised accuracy during alternating-implant workflows, with all 40 cases sub-millimeter. Findings are hypothesis-generating pre-clinical observations requiring validation in adequately powered, multi-operator prospective studies before clinical inference.