Introduction Osteoarthritis of the knee is a very common disease.In 80 to 90% of the cases it starts in the medial compartment and tends to remain there.Therefore, the Oxford Unicondylar Knee Prosthesis (OUKP) is a attractive device as it only replaces the diseased parts of the knee.For the past 15 years, the results of the OUKP, especially those achieved by the designer’s group, have mostly been very good. However, reports about long-term follow-up are scarce. For the designer group, Murray reported a 98% ten year survival. The only independent research bij Svard an Price and by Lewold of the Swedish Arthroplasty Study showed a good survival of 95% at 10 years and a poor survival of 87% at 8 years respectively.Our independent study reviews a ten year follow up of 149 OUKP’s.

Methods and Results One hundred forty-nine medial prostheses were implanted in 140 patients between 1988 and 1996. After a mean of 67 months 28 patients had died, without the need for revision. Seventeen prostheses were lost to follow-up. Revision surgery using a total knee prosthesis was performed in 16 cases. In 4 others, a lateral prosthesis was implanted subsequently to a medial one. One of these 4 was revised to a total knee prosthesis 6 years later. In another 4 cases, late complications of the meniscal bearing were treated with replacement of this bearing. In the group af patients older than 75 years, no revisions were recorded. The surviving prostheses were seen back after a mean of 126 months. The cumulative survival rate at 10 years was 82% for the whole population and 84% when knees with a previous high tibial osteotomy were excluded.

This difference is significant (p=0,0000).

Conclusion These results are in line with those of the Swedish arthroplasty register and compare poorly to the survival of total knee arthroplasty, therefore this prosthesis is not the first choice for most cases. Because it preserves a maximum of bone stock and is revised to a total prosthesis almost without difficulty, it is the first-choice implant for medial unicompartmental osteoarthritis in the relatively young patient.The survival rate in the group of patients older than 75 years is as good as or better than that for total knee arthroplasty.Since the OUKP can now be placed minimally invasive, it might have its place in this subgroup. It should not be used in osteotomized knees.