Unicompartmental knee replacement

Hemiarthroplasty of the knee, first described in the 1950s, refers to the concept of placing a spacer in one half of the femoral tibial joint to prevent bone on bone apposition. McKeever [1] first introduced his Vitallium (Zimmer Inc., Warsaw, IN) tibial plateau (Fig. 1) in 1957. MacIntosh [2] followed with an acrylic tibial plateau (Fig. 2) in 1958, and then one made of Vitallium in 1964. MacIntosh and colleagues [3] then presented their initial series in Switzerland in 1967 and published findings from a series of patients in 1972 that demonstrated "good results" in most patients who had follow-ups of 6 years [2]. The modem-day version of the hemiarthroplasty is the Unispacer (Smith & Nephew, Inc., Memphis, TN) (Fig. 3A, B), with results from 2-year follow-ups reported as 80% successful [4]. In the early 1970s, the Gunston and polycentric unicompartmental knee arthroplasties were introduced (Fig. 4A, B). The revision rate of these early devices at 2 years was approximately 10% [5,6]. Multiple authors from 1973 to 1983 noted success rates varying between 37% and 92% with 2- to 8-year follow-ups [5-13]. From 1987 to 1991, long-term results were published with 87% to 90% survivorship at 13 to 16 years [14-16]. From 1990 to 1993, several authors reported 90% to 96% fair to good results using a combination of metal-backed and all polyethylene tibial components with 2- to 7-year follow-ups [17-21]. These reports were the first to note that obese patients had a 1.4 times greater failure rate [18].