Accuracy of implantation of a unicompartmental total knee arthroplasty with 2 different instrumentations: a case-controlled comparative study.

The accuracy of implantation is an accepted prognostic factor for the long-term survival of unicompartmental total knee arthroplasties (UKAs). We adapted the conventional instruments for tricompartmental total knee arthroplasty implantation, with intramedullary femoral and extramedullary tibial guiding rods, to a UKA implantation. A total of 52 patients in whom a UKA was implanted with this instrumentation were matched (using age, sex, body mass index, preoperative coronal mechanical femorotibial angle, and severity of preoperative degenerative changes according to Ahlback) with 52 patients operated with the alternative instruments. Accuracy of implant placement measured by radiography was improved significantly by the new instrumentation, but there was no difference in the survival rate or the clinical outcome after 5 years in both groups. No complication related to the new instrumentation occurred. Longer follow-up is required to determine the advantages and disadvantages of both techniques.