Summary

Early experience of the use of fully automated active robotic system in TKA shows that it is safe and also is effective in achieving accurate implant size and implant/limb alignment.

Abstract

Background

Despite improvements in the implants and surgical techniques about 20% of patients remain dissatisfied with their primary Total Knee Arthroplasty (TKA). Accurate implant size/ alignment and limb alignment are necessary for the long term survival of the implant 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 semi-active and active robotic system for performing TKA is increasing. The novel fully automated active robotic system performs milling of the bone surfaces with a high speed burr. The aim of the study was 1) To study the safety of the fully automated active robotic system by comparing the incidence of adverse events to the literature control values associated with conventional manual TKA. and 2) To study the effectiveness of the system in predicting the implant size/ alignment and limb alignment and compare it with the literature control values for conventional manual TKA

Materials And Methods

A single center clinical trial was conducted following 60 knees undergoing active RA-TKA for 6 months. Inclusion criteria were patients undergoing RA-TKA for end stage osteoarthritis and rheumatoid arthritis. Patients undergoing conventional TKA and revision TKA were excluded from the study. Sample size was estimated to be 58 patients with a error of 0.05 and ß error of 0.2 with power of study being 80. A pre-defined list of RA-TKA adverse events was employed to study the safety of the system. The safety endpoint was assessed against the composite rate of adverse events incidence rate of 7.6 %. The adverse events associated with the manual TKA reported in the literature are medial collateral ligament injury (2.7%), extensor mechanism injury( 2.1%), nerve injury /palsy( 1.3%), femoral/ tibial condyle fracture( 0.68%) , patellofemoral malalignment ( 0.5%), knee subluxation/ dislocation ( 0.2%) and popliteal vessels injury( 0.15 %) .
Efficacy was judged by comparing the planned versus achieved Implant size, alignment and limb alignment on post-operative radiographs. The post-operative clinical evaluation was done by an independent observer who was not part of the operating team. The primary safety hypothesis was tested using a one sided Exact binomial test. The primary efficacy hypothesis was tested using Chi-squared test. The p value < 0.05 was considered significant.

Results

Pre-defined adverse events did not occur in any of the 60 RA-TKA (statistically significant p value < 0.001). The implant size accuracy was 100 % (60 out of 60 knees) for femoral component and 96.67% (59 out of 60 knees) for tibial component (statistically significant, Chi-squared test, p value 0.0003 and 0.0461 respectively). The implant position and limb alignment was accurate in 100 % of patients (p value < 0.001).

Conclusion

Early experience of the use of fully automated active robotic system in TKA shows that it is safe and also is effective in achieving accurate implant size and implant/limb alignment. This may have a potential to improve the implant longevity, clinical outcomes and patient satisfaction.