Unicondylar knee arthroplasties polycentric

Surgeons at the Mayo Clinic started using Polycentric UKAs beginning in 1971 (Skolnick, Bryan, and Peterson 1975). This procedure used identical implant components as the TKR version of the Polycentric. Stolnick and colleagues (1975) described the 1-year results for 14 knees in 13 patients in 1975. By 1979, Bryan and Peterson (1979) had reported that 338 Polycentric UKAs had been performed at the Mayo Clinic. 

At the Mayo Clinic, Polycentric UKA was performed only on patients with unicondylar disease (osteoarthritis) (Jones et al. 1981, Skolnick, Bryan, and Peterson 1975). An initial assessment was based on radiographic screening. However, the UKA implantation technique involved the same exposure as in TKA, so that both compartments could be directly examined and evidence of unicompartmental disease visually confirmed. Mallory also reported the utility of Polycentric UKA in the treatment of post-traumatic arthritis resulting from fracture-induced deformity of the knee (1973). 

The main feature of Polycentric UKA was the relief of pain and restoration of mobility in the majority of patients (Mallory 1973, Skolnick, Bryan, and Peterson 1975). In Stolnick and colleagues study, the average range of motion was 119 degrees before the procedure and 116 degrees after (1975). 

Because the implants and the procedure were identical. Polycentric UKA can be considered a special case of the Polycentric TKA. The primary difference is in the patient selection. Although superceded in the 1970s by other UKA designs, such as the Geomedic, Savastano, and Marmor prostheses (Marmor 1988), the Polycentric UKA is nonetheless the earliest example for the use of UHMWPE to treat unicompartmental disease in the knee. 

First-generation, cemented unicondylar knee designs from the mid-1970s. (A) Geomedic (B) Savastano unicondylar hemiknee prostheses. 

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