Summary

The study findings show that the RA- TKA does not take additional time than C-TKA.

Abstract

Background

Despite improvements in the implants and surgical techniques about 20% of Total Knee Arthroplasty (TKA) patients remain dissatisfied. Accurate implant size/ alignment and limb alignment are necessary for the long term implant survival and successful outcome. Implant overhang/ under sizing and limb malalignment is associated with suboptimal patient reported outcome measures and increased chances of revision. Use of robotic system for performing TKA is increasing. Robotic assisted Total Knee replacement (RA- TKR) has shown to improve the accuracy of the implant size. It also allows dynamic confirmation of the implant and limb alignment during the TKA procedure. The major inhibition of the Arthroplasty surgeon in adapting to the robotic assisted TKA is the extra time spent during the registration process and milling of the bone with the Robot. The aim of the study was to ascertain the extra time spent during these two steps as compared to the conventional TKA (C-TKA).

Methods

A prospective study involving 30 patients each in the C-TKA and RA- TKA operated by the same surgical team using posterior stabilized high flexion TKA implant. The sample size was estimated to be 28 patients in each group for anticipated 10 % increase in operation time with alpha error of 0.05 beta error of 0.2 and power of study being 80%. Patients were given a choice between the C-TKA and RA-TKA and consecutive 30 cases in each group were studied by an independent observer. RA-TKA group patients underwent a pre-operative 3 dimensional CT scan. After segmentation of the scan images a bone model was prepared. The operating surgeon along with system specialist did the preoperative planning as regards the implant size/ alignment and limb alignment on a computer with specialized software. After surgical exposure of the knee joint and insertion of tracker pins, the surgeon did registration of 40 points on the femur and the tibia. Once the actual anatomy of the patient matched with the CT generated bone model as judged by root mean square error <1, the robot was docked to the patients leg with external fixator pins. After confirming a clear path for milling of the tibia and femur, the fully automated active robot performed the femur and tibia cuts by milling of the bone utilizing high speed burr. In C-TKA group the time for the application of appropriate zigs and execution of the bone cuts and soft tissue release was recorded whereas in RA-TKA group the time taken for registration and bone milling with robot and required soft tissue release was measured. The statistical difference between the times of two groups was measured with student t-test and p-value <0.05 was considered significant.

Results

The pre-operative patient characteristics (age, sex, BMI, HKA angle, pre-operative ROM) were similar in both the groups. The time taken in C- TKA and RA-TKA group was 33.6 +/- 4.4 and 35.5 +/- 4.5 respectively which is statistically non-significant (p value < 0.0599).

Conclusion

The study findings show that the RA- TKA does not take additional time than C-TKA.