Alignment errors in medial unicompartmental knee arthroplasty (UKA) predispose to premature implant loosening and polyethylene wear. The purpose of this study was to determine whether a novel CT-free robotic surgical assistant improves the accuracy and reproducibility of bone resections in UKA compared to conventional manual instrumentation.
Sixty matched cadaveric limbs received medial UKA with either the ROSA® Partial Knee System or conventional instrumentation. Fifteen board-certified orthopaedic surgeons with no prior experience with this robotic application performed the procedures with the same implant system. Bone resection angles in the coronal, sagittal and transverse planes were determined using optical navigation while resection depth was obtained using calliper measurements. Group comparison was performed using Student’s t test (mean absolute error), F test (variance) and Fisher's exact test (% within a value), with significance at p < 0.05.
Compared to conventional instrumentation, the accuracy of bone resections with CT-free robotic assistance was significantly improved for all bone resection parameters (p < 0.05), other than distal femoral resection depth, which did not differ significantly. Moreover, the variance was significantly lower (i.e. fewer chances of outliers) for five of seven parameters in the robotic group (p < 0.05). All values in the robotic group had a higher percentage of cases within 2° and 3° of the intraoperative plan. No re-cuts of the proximal tibia were required in the robotic group compared with 40% of cases in the conventional group.
The ROSA® Partial Knee System was significantly more accurate, with fewer outliers, compared to conventional instrumentation. The data reported in our current study are comparable to other semiautonomous robotic devices and support the use of this robotic technology for medial UKA.
Level of evidence
Cadaveric study, Level V.
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We are grateful to the orthopaedic surgeons who performed the cadaveric surgeries: Dr. Jeff Almand, Dr. Tomasz Antkowiak, Dr. Miles Birmingham, Dr. Nathan L. Cafferky, Dr. Michael A. Charters, Dr. Sridhar M. Durbhakula, Dr. Nicholas Frisch, Dr. Thomas John, Dr. Atul F. Kamath, Dr. Barry Kraushaar, Dr. W. Trevor North, Dr. Ari D. Seidenstein, Dr. Ahmed Siddiqi, Dr. Garen Daxton Steele and Dr. Charles Toulson.
This research was funded by Zimmer Biomet.
Conflict of interest
Dr. Jess H. Lonner is a paid consultant for Zimmer Biomet and Smith & Nephew. Dr. Ari D. Seidenstein, Dr. Michael A. Charters, Dr. W. Trevor North, Dr. Nathan L. Cafferky, Dr. Sridhar M. Durbhakula and Dr. Atul F. Kamath are paid consultants for Zimmer Biomet.
The study did not include research with animals or living human participants and was declared exempt by the local institutional review board.
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Lonner, J.H., Seidenstein, A.D., Charters, M.A. et al. Improved accuracy and reproducibility of a novel CT-free robotic surgical assistant for medial unicompartmental knee arthroplasty compared to conventional instrumentation: a cadaveric study. Knee Surg Sports Traumatol Arthrosc (2021). https://doi.org/10.1007/s00167-021-06626-4
- Unicompartmental knee arthroplasty
- Robotic surgery
- Conventional instrumentation
- Bone resection
- ROSA® Partial Knee System