Assessment of accuracy of robotically assisted unicompartmental arthroplasty.

Purpose: The purpose of this study was to analyse the accuracy of component placement during unicompartmental knee arthroplasty (UKA) using a robotic-assisted system.

Methods: Two hundred and six patients (232 knees) who underwent medial robotic-assisted UKA were retrospectively studied. Femoral and tibial sagittal and coronal alignments were measured in the post-operative radiographs and were compared with the equivalent measurements collected during the intra-operative period by the robotic system. Mismatch between pre-planning and post-operative radiography was assessed against accuracy of the prosthesis insertion.

Results: Robotic-assisted surgery for medial UKA resulted in an average difference of 2.2° ± 1.7° to 3.6° ± 3.3° depending on the component and radiographic view between the intra-operatively planned and post-operative measurements. Mismatch between pre-planning and post-operative radiography (inaccuracy) was related to improper cementing technique of the prosthesis in all measurements (except for tibial sagittal axis) rather than wrong bony cuts performed by the robotic arm.

Conclusion: Robotic-assisted medial UKA results in accurate prosthesis position. Inaccuracy may be attributed to suboptimal cementing technique.