gms | German Medical Science

Objectives: The potential number of patients who fit the criteria for unicondylar knee arthroplasty (UKA) exceeds the number of procedures completed. A more invasive procedure, the total knee arthroplasty (TKA), is common where both the medial and lateral condyle is replaced with an implant rather than just one condyle as with the UKA. The revision rates for TKA are lower than those reported for a UKA but the UKA patients report superior clinical and functional outcomes compared to TKA patients. On major reason cited for the high revision rates us the implant malalignment. Robotic assistive UKA offers the potential to increase the accuracy of the bone preparation and implant positioning. This study reports the difference between the planned and achieved angle in the coronal plane reported by an image free robotic surgical system for UKA.

Methods: This prospective study reports on 300 UKA cases completed with the assistance of an image free robotic surgical system. These procedures were performed by 22 surgeons in 16 hospitals across Europe and the USA. The system uses infrared navigation for intra-operative registration. The surgeon plans the placement of the tibial and femoral implant components in all three rotational axes to “best match” the patient's specific anatomy. The soft tissue envelope is optimised and the system calculated the post-operative tibiofemoral alignment in the coronal plane prior to bone cuts. The implant placement plan is then implemented with accurate bone preparation using a robotically controlled cutting bur.

Results and Conclusion: The achieved tibiofemoral angle in the coronal plane was within 1o, 2o and 3o of the surgical plan in 88.9%, 96.6% and 99.3% of the cases respectively. The mean angular difference between the planned and achieved tibiofemoral angle was -0.1o (SD 1.03o). Therefore, 97% of the cases achieved an alignment within 2o which compares to only 40% of manual cases reporting this accuracy levels in the literature. It is important that navigation systems can be relied upon to accurately produce the planned results. This study reports excellent levels of accuracy in an image free robotic system when used for bone preparation in UKA.