In last ten years U.K.R. number increased due to diffusion of M.I.S. concepts, new indications/tecniques and durable prosthetic models. Also the amount of revisions, performed for different reasons, has increased. Failures relate to planning and surgical errors, aseptic loosening, non treated or femoro patellar compartment degeneration, ligaments instability, P.E. wear, components ruptures, infections.

In our division in 1990–2003 we performed 136 U.K.R. revisions on 13 different implants with a prevalence of “fixed bearing” (79,40%) on “meniscal bearing” (20,60%). A classification withprevalence of failure causes, different from T.K.R.’s, is proposed. Revision procedure strongly depends on causes: “Uni”, “BiUni” or “Total” approach is possible. We present our experience and derived indications.

Aseptic loosening were treated differently depending on bone stock and on failure risk factors (ligament laxity, surgical osteotomic or axial errors, fixation defects) with a “Uni” revision or with a “Total”. Unicompartimental degeneration with a previous medial or lateral U.K.R. in good conditions may undergoes “BiUni” instead of “Total” only in absence of ligament laxity and femo-ropatellar symptomatic degeneration. Femoro-patellar degeneration needs a T.K.R. implant. We managed cases with macroscopic surgical errors (ostheotomy or component alignment) by using T.K.R. (stemmed and with auto-graft if needed) and U.K.R. revision. Failures due to varus-valgus instability were normally treated with T.K.R. (standard or stemmed) and with constrained T.K.R. (1 Reumatoid Arthritis case). We resolve P.E. debris failures in fixed bearing implants simply with a component change as we do in stress fractures (femur or “full poly” tibia). We treat infections with a 2 step procedure; for 2°step we used T.K.R. (standard or stemmed).

In conclusion U.K.R. revision is technically easier than TKR’s, bone stock defect may be fighted with auto graft and/or stems and in a selected amount of cases it’s possible to use U.K.R. orstandard T.K.R. with very similar long term results of first implants.

Background: Unicompartmental knee arthroplasty was developed as an alternative to the finality of tricompartmental, total knee arthroplasty. Recent short-term and intermediate-term results show favorable results when compared to the first generation results reported in the 1970’s and early 1980’s. The purpose of this study was to report the long-term, single surgeon use of the Allegretto unicondylar knee prosthesis.

Methods: We evaluated 115 medial unicompartmental knee arthroplasties that were implanted by a single surgeon using the Allegretto prosthesis. The average age of the patients at the time of surgery was sixty-eight years. No patients were lost to follow-up. Nineteeen patients were unable to continue long-term office follow-up and were contacted by telephone. Thirty-four patients (thirtyfive knees, 30%) died from unrelated causes. None of the patients that died underwent revision of the index UKA. Thus there were sixty-one patients available for prospective clinical and radiographic evaluation beyond ten-years.

Results: The average time to follow-up for those patients available prospectively was 11.1 years (0.8 years; range, ten years to thirteen years). Clinical evaluations revealed an average pre-operative HSS score of fifty-four points which improved at the most recent post-operative follow-up to an average of ninety-three points. At the most recent average time to follow-up, the post-operative range of motion was assessed at an average of 0.3 degrees of extension through 124.4 degrees of flexion. Radiographically, no component showed evidence of loosening as defined as change in position of the components on serial radiographs. Twenty-one knees demonstrated radiolucencies less than 2 mm of thickness and none were progressive. The Kaplan-Meier survival analysis was calculated and showed a probability of survival of all UKA implants of 97% at thirteen years follow-up (standard error 0.04) with an end-point of revision or radiographic failure.

Conclusions: Provided correct patient selection and technical expertise, the Allegretto UKA system allows for the expected relief of pain, restoration of function and component survival in those patients with medial compartmental knee arthrosis through ten-years.