gms | German Medical Science

Objectives: The number of revision arthroplasty operations is rising recently. Robotic arthroplasty is increasingly being used in primary arthroplasty and is already showing promising results in terms of accuracy and revision rates. The purpose of this pilot study is to investigate the operation time, aligment accuracy and early revision rate of robotic-assisted revision arthroplasty from medial unicondylar arthroplasty (UKA) to total knee arthroplasty (TKA) and subsequently to compare it to primary robotic-assisted arthroplasty.

Methods: This pilot retrospective, case-control study included patients undergoing image-less robotic-assisted revision arthroplasty from medial UKA to TKA (n=20) and patients undergoing image-less robotic-assisted primary TKA (control group, n=20) from 11/2018 to 02/2020. The control group was matched on the basis of BMI and natural alignment (UKA revision group: contralateral alignment, or preoperative to primary UKA radiographs). Comparison of groups was based on postoperative alignment, outlier rate, onlay size, bone resection depth, incision-to-wound closure time and early revision rate (min. follow up: 1 year). All surgeries were performed by a single senior surgeon using the same bi-cruciate stabilizing TKA system functionally aligned with respect to the preoperative soft tissue balance and prearthritic anatomy. Alignment goal was the reconstruction of the prearthritic anatomy avoiding valgus OLA, severe tibial varus alignment with mPTA < 87°, and conservative slope of 3° (± 2°). Statistics consisted of parametric t-testing and fisher-exact test with a level of significance of p<0.05.

Results and Conclusion: Groups showed no difference of mean BMI and natural alignment (p> 0.05). Revision and primary groups showed no differences in mean overall limb alignment (178.6° vs. 176.0°, p=0.22), mean mPTA (88.5° vs. 88.9°, p=0.83), mean lDFA (87.6° vs. 89.5°, p=0.49) and mean slope (2.4 vs. 2.6, p=0.86). Outlier rate was similar for mPTA accuracy for both groups (5%, n=1 each) and higher for slope accuracy in the primary group (5% vs. 15%, n=1 vs. n=3, p=0.6). No outlier was found for OLA. Smallest onlay size (9mm) was used in 70% of the cases in the revision group (n=14) and in 90% of the cases in the primary group (n=18, p=0.24), distal femoral and tibial resection depth showed no statistical difference (p> 0.05). The incision to wound closure time was longer in the revision group, but showed no significant difference (78min vs. 65.5min, p=0.12). No complications or revisions were recorded in the time of follow up within both groups.

Image-less robotic-assisted revision arthroplasty of UKA to TKA procedures shows comparable surgery time, alignment accuracy and early revision rate in comparison to primary robotic-assisted TKA. Comparable bone preserving and consecutive onlay size use was observed for both groups.