Summary

With regard to the learning curve, it was possible to quickly become proficient in 10 cases when TKA was performed by a certified arthroplasty surgeon using the Mako robotic arm.

Abstract

Purpose

The application of robotics in the operating room for total knee arthroplasty (TKA) remains controversial. The aim of this study was to investigate the short-term results and learning curve of robotic arm-assisted TKA performed by one certified prosthetic surgeon in Japan.

Methods

A retrospective analysis was performed of 40 patients (7 males and 33 females) receiving a TKA with Mako robotic arm-assisted system and were evaluable up to 3 months after surgery. The average age of the patients was 76.6 ± 6.4 years, and BMI was 25.3 ± 3.8. We investigated operative time, pre- and postoperative range of motion and thigh circumference. Cumulative summation (CUSUM) analyses were used to assess learning curves for operative time as the outcome. In addition, the Pain Visual Analogue Scale (VAS), the Knee injury and Osteoarthritis Outcome Score (KOOS), the MOS Short-Form 36-Item Health Survey (SF-36), and the Forgotten Joint Score-12 (FJS) were used as evaluation criteria.

Results

At discharge (average 17.5±5.9 days postoperatively), there was significant improvement in the angle of extension (p<0.001), VAS during exercise (p<0.001), KOOS (Pain, ADL, Total) (p<0.05), SF-36 (PF, MH) (p<0.05), and FJS (p<0.01). At 3 months postoperatively, there was significant improvement in extension angle (p<0.001), VAS during exercise (p<0.01), KOOS (Symptom/Stiffness, Pain, ADL, Quality of Life, Total) (p<0.05), SF-36 (PF, BP) (p<0.001), and FJS (p<0.01). The operative time was average 49.8±8.0 minutes, with a median of 50 minutes; robotic arm-assisted TKA was associated with a learning curve of 10 cases for operative times (p< 0.01). There was no significant difference in thigh circumference before and after surgery.

Discussion

The fact that the femoral circumference did not change before and after surgery and that the pain score and FJS had already improved at the time of discharge from the hospital led us to believe that Mako robotic arm-assisted TKA is a less invasive procedure than manual surgery. Regarding the learning curve, it was possible to achieve proficiency quickly in 10 cases when performed by a certified arthroplasty surgeon. Vermue et al. examined the learning curves of several surgeons at various surgical levels and found that 10 to 40 cases were needed. However, the way they read the graph was different from ours, and it was clear that a high-volume surgeon who performs more than 100 manual TKA cases per year can become proficient in 10 to 20 cases. Robotic arm-assisted TKA is associated with a learning curve for surgical time, which might be shorted than reported in current literature and dependent on the profile of the surgeon.