Failure of Unispacer
In the absence of reliable evidence, it is the opinion of the work group not to use the free-floating (un-fixed) interpositional device in patients with symptomatic medial compartment osteoarthritis of the knee.

Rationale
One published case series reported the results of free-floating (un-fixed) interpositional device surgery for treatment of medial unicompartmental OA of the knee.129 We determined that the evidence was low-strength.

The evidence indicated high reoperation rates in the patients who were followed.  Thirty-two percent of patients were revised to total knee arthroplasty. The evidence showed differences from baseline that were not clinically or statistically significant for increased pain measured with the VAS two years postoperatively. Knee Society Score function subscale scores were “poor” postoperatively.

The AAOS workgroup modified the grade of this recommendation to consensus, because of the high revision rates in this study, increased pain, and the potential harm associated with this intervention (anesthesia risks, VTE, infection, and reoperation).

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