SURVIVORSHIP AND PATIENT SATISFACTION OF ROBOTIC-ASSISTED MEDIAL UNICOMPARTMENTAL KNEE ARTHROPLASTY AT A MINIMUM TWO-YEAR FOLLOW-UP

INTRODUCTION

Successful clinical outcomes following unicompartmental knee arthroplasty (UKA) depend on component positioning, soft tissue balance and lower limb alignment, all of which can be difficult to achieve using manual instrumentation. A new robotic-guided technology has been shown to improve postoperative implant positioning and lower limb alignment in UKA but so far no studies have reported clinical results of robotic-assisted medial UKA. Goal of this study therefore was to assess outcomes of robotic-assisted medial UKA in a large cohort of patients at short-term follow-up.

METHODS

This multicenter study with IRB approval examines the survivorship and satisfaction of this robotic-assisted procedure coupled with an anatomically designed UKA implant at a minimum of two-year follow-up. A total of 1007 patients (1135 knees) underwent robotic-assisted surgery for a medial UKA from six surgeons at separate institutions in the United States. All patients received a fixed-bearing metal backed onlay implant as the tibial component between March 2009 and December 2011 (Figure 1). Each patient was contacted at minimum two-year follow-up and asked a series of five questions to determine implant survivorship and patient satisfaction. Survivorship analysis was performed using Kaplan-Meier method and worst-case scenario analysis was performed whereby all patients were considered as revision when they declined study participation. Revision rates were compared in younger and older patients (age cut-off 60 years) and in patients with different body mass index (body mass index cut-off 35 kg/m²). Two-sided chi-square tests were used to compare these groups.

RESULTS

Data was collected for 797 patients (909 knees) with an average follow-up of 29.6 months (range: 22 – 52 months). At 2.5-years follow-up, eleven knees were reported as revised, which resulted in a survivorship of 98.8% (Figure 2). Thirty-five patients declined to participate in the study yielding a worst-case survivorship of 96.0%. Higher revision rates were seen in younger patients (2.60% versus 0.93%, p = 0.09) and in morbidly obese patients (3.36% versus 0.91%, p = 0.03). Of all patients without revision, 92% was either very satisfied or satisfied with their knee function (Figure 3).

CONCLUSION

In this multicenter study, robotic-assisted UKA was found to have high survivorship and satisfaction rate at short-term follow-up. Prospective comparison studies with longer follow-up are necessary in order to compare survivorship and satisfaction rates of robotic-assisted UKA to conventional UKA and robotic-assisted UKA to total knee arthroplasty.

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