Both MacIntosh and McKeever reported positive results, but neither’s results could be replicated consistently enough to be deemed successful. In 1972, MacIntosh published his results and saw an 80% success rate for osteoarthritic knees and only a 69% success rate for rheumatoid knees (Table 1.1;I). Early historical reports of UKA survivorship exhibited varying degrees of success, resulting in many surgeons abandoning the procedure as a treatment for isolated compartmental joint arthritis.
UKA Prosthesis-specific design survivorship % based on implant failures resulting in revision surgery at time of study reported follow-up
Historically, selection criteria for UKA were nonexistent, and no official consensus was available to guide surgeons. Essentially, there were believers and nonbelievers in the procedure, with no definitive algorithms available for determining appropriate candidates. Kozin and Scott developed the first widely adopted set of indications and contraindications for UKA in the late 1980s. Such criteria were held steadfast until recently, when there has been a challenge to expand the indications for UKA. While some surgeons may now recommend UKA in patients with ACL-deficient knees or patellofemoral arthritis , there remains relatively strong opposition that ascribes to the stricter indications outlined by Kozin and Scott et al. (Table 1.2) . Following these relatively stringent parameters, Ritter et al. found that 4.3% out of 4021 knee arthroplasties met the indications for UKA, while 6.1% were appropriate candidates for UKA based on surgical pathology assessments . These numbers are relatively consistent with current rates of UKA in the United States; however, there are centers driving these numbers up with rates as high as 20–30%.
Classic indications for UKA outlined by Kozinn and Scott , suggesting the ideal patient should be selected using the following inclusion criteria. Many surgeons still follow these classic indications with extended measures applied to age, weight, and level of activity
Inflammatory arthritis, age less than 60, high activity level, pain at rest, patellofemoral pain, opposite compartment pain, exposed bone in PF compartment
UKA Historical Advancements and Innovation
After the initial introduction of UKA prostheses, modern changes to the implants and refined surgical techniques soon followed and have continued to develop over time. In 1969, the St. Georg Sled (Fig. 1.2) was developed in Hamburg, Germany, as a new cemented UKA option. It built upon the flat polyethylene tibial components used in earlier prosthetic prototypes and added a biometallic biconvex femoral component with two pegs for stability. This fixed-bearing prosthesis reported high levels of survivorship reported out to 25 years (Tables 1.1 and 1.3). At roughly the same time, Gunston and other polycentric knee replacement implants were being developed and brought to market.
Oxford Knee UKA prosthesis by historical phase design and survivorship % based on implant failures resulting in revision surgery at time of study reported follow-up