Implant Position, Survivorship, and Patient-Reported Outcomes in Manual Medial Unicompartmental Knee Arthroplasty.

BACKGROUND

Two related recent reports described high error rates for implant positioning and reduced implant survivorship in manual unicompartmental knee arthroplasty (MUKA) compared to robotic-assisted unicompartmental knee arthroplasty (RUKA). The present study scientifically replicated these reports by comparing MUKAs similarly performed by an experienced high-volume surgeon in similar patients using the same study methods as these reports.

METHODS

A total of 216 consecutive MUKAs were retrospectively evaluated radiographically for achievement of implant positioning targets. Achievement of targets was compared to the published MUKA and RUKA outcomes and correlated with revision rates and patient-reported outcome measures.

RESULTS

There were 20% of study MUKAs compared to 88.1% of comparison MUKAs (P < .001) and 31.4% of comparison RUKAs (P < .048) that failed to meet all 7 implant positioning targets. The MUKA revision rates were significantly lower in the study sample than for comparison MUKAs (3.2% versus 14.2%, P < .001). Implant survivorship was 91.7% (95% confidence interval 84.9, 98.5%) at 8.9 years compared to 70.0% (95% confidence interval 56.0, 80.0%) at 10.2 years, respectively. Most patient-reported outcome measures did not differ based on achievement of implant positioning targets (P ≥ .072).

CONCLUSIONS

Present study findings indicate that observations in the 2 recent reports may not be generalizable to all UKA surgeons. Additional data on the relationship between implant positioning and revision as well as functional outcomes are needed to identify appropriate robotic arthroplasty applications.