Patients Experience Good Long-Term Outcomes Following Robotic-Assisted Medial UKA

Robotic-arm assisted medial unicompartmental knee arthroplasty (UKA) provides good long-term outcomes, with implant survival and patient satisfaction rates exceeding 90% at 10 years of follow-up, according to a study published online ahead of print by The Journal of Bone & Joint Surgery.

Because UKA preserves most of the normal knee anatomy, it may offer a shorter hospital stay and greater knee range of motion postoperatively, compared with the more common and extensive total knee arthroplasty (TKA).

Previous studies have shown that the use of a surgeon-controlled robotic arm can improve the precision of UKA, potentially avoiding technical errors that can affect outcomes postoperatively. Previous studies have reported high survivorship free from conversion to TKA at mid-term follow-up following robotic-arm assisted UKA.

“Given the increased use of robotic systems in knee arthroplasty and the favorable early outcomes, the current challenge lies in demonstrating whether these results can be maintained at longer-term follow-up,” the study authors said in their published report.

Study Methods and Findings

In this prospective study, the researchers analyzed the 10-year outcomes of 411 knees in 366 patients who underwent robotic-arm assisted medial UKA at 4 participating centers. The average age of patients at surgery was 67.2 years, and 57% were male.

All procedures were performed by 4 experienced joint replacement surgeons who received special training and practice in robotic-arm-assisted UKA. The study included 10-year follow-up data on the initial series of patients who received a specific type of cemented implant (Restoris MCK Partial Knee Implant System, Stryker; Kalamazoo, Michigan) and a third-generation robotic-guided surgical system (Mako Robotic-Arm Assisted System, Stryker).

Follow-up results showed good outcomes of robotic-assisted UKA. Overall survivorship with the medial UKA implant still in place was 91.7%. Of the 29 revisions, 26 were a conversion to TKA, for a survivorship of 92.6%.

The rate of conversion to TKA was about twice as high in women compared with men (hazard ratio of 2.3). Revision risk was also higher for patients with a body mass index of 30 or higher and for younger patients, the latter likely reflecting a more active lifestyle and increased demands on the knee. Most revision surgeries resulted from unexplained knee pain or aseptic loosening.

Patient satisfaction ratings supported the good outcomes of robotic-assisted UKA. “Of all patients without revision, 91% reported being either very satisfied or satisfied with their operative knee, while 4% were dissatisfied or very dissatisfied,” the study authors said in their published report.

The high rates of survivorship and patient satisfaction are consistent with long-term studies of conventional UKA. The researchers note some limitations of their study, highlighting the need for prospective comparative studies. Dr. Bayoumi comments, “Since this was a single-arm trial, it remains to be determined whether robotic-arm assistance for UKA results in improved outcomes compared to conventional UKA.”


Bayoumi T, Kleeblad LJ, Borus TA, et al. Ten-Year Survivorship and Patient Satisfaction Following Robotic-Arm-Assisted Medial Unicompartmental Knee Arthroplasty: A Prospective Multicenter Study. J Bone Joint Surg Am. 2023 May 5. doi: 10.2106/JBJS.22.01104. Online ahead of print.

Leave a Reply

CME Updates