Intra- and inter-operator reliability assessment of a novel extramedullary accelerometer-based smart cutting-guide for total knee arthroplasty: an in-vivo study

Aims To verify the intra- and inter-operator reliability of an extramedullary (EM) accelerometer-based smart cutting-guide for distal femoral resection during primary total knee arthroplasty (TKA). Hypothesis: good correlation between operators and a difference < 1°, indicating a good reliability of the device. Methods 25 not consecutive patients with knee osteoarthritis undergone to primary TKA using an EM inertial-based cutting guide to perform distal femoral resection. In order to assess the agreement in femoral axis definition of the device, two operators performed three time each the maneuvers necessary to define axis. Inter rater agreement was evaluated with Bland & Altman agreement test. Intra rater repeatability was evaluated analysing average results distribution of repeated measurements. Accuracy of the device was evaluated comparing differences between intra operative device data with final implant alignment measured on post-operative longstanding x-rays using Students’ t test. Results Agreement between the two operators was statistically significant (p<0.05) with a Bias of -0.4° (95%CI -0.6° to -0.2°). Average difference between cut orientation measured with device and final implant position, measured on x-rays was 0.2° (95%CI -1.5° to 1.7°) with no statistical difference between the two measurements. Final implant alignment, measured on x-ray was 90.2°, with 95% of cases distributed within range 88.0° to 92.0° for varus-valgus and 2.8°, with 95% of cases distributed within range 2.0° to 4.0° for flexion-extension. Conclusions The inertial-based EM cutting guide used to perform distal femoral resection during primary TKA demonstrated a good intra- and inter-operator reliability in the present in-vivo study.