Purpose of the study: The purpose of this study was to report the results observed in a consecutive series of 54 lateral unicompartmental knee prostheses with minimum five years follow-up.

Material and methods: One hundred forty-four unicompartmental cemented HLS resurfacing prostheses were implanted with a chromium-cobalt femoral element and an all polyethylene polyethylene element. Among these consecutive implantations performed from 1998 to 2003 in accordance with indications established in 1988, 54 were lateral unicompartmental knee prostheses (37.5%) implanted in 10 men and 44 women. Mean age was 68.5 years (range 25–88). A lateral approach was used for the first six implants in this series. One patient was lost to follow-up, five died and one underwent revision for a total prosthesis. Forty-seven patients were reviewed with mean 100.9 months follow-up (64–159). Clinical data were analysed with the IKS criteria and all patients had a complete radiographic work-up before surgery and at last follow-up.

Results: In this series 96.3% of patients (n=52) were satisfied or very satisfied. Mean flexion was 133 (110–150). The mean knee score was 81.1 (25–100). Mean residual alignment was 2° valgus. A lucency was noted in 13.2% of knees, but remained stable. There was one failure requiring revision for a total prosthesis (loosening of the tibial component). The Kaplan-Meier survival was 98.1% at ten years. Three patients exhibited wear of the medial femorotibial compartment and had a medial unicompartmental implant. The overall survival (rein-tervention irrespective of reason) was 91.1%.

Discussion: Outcomes were very satisfactory, globally similar to recent series in the literature. Reliable sustainable outcomes with lateral unicompartmental implants have led us to widen our indications (moderate overweight, younger patients).

Recently in Europe, Unicompartmental Knee Arthroplasty (UKA) has regained interest in the orthopedic community; however, based on various reports, results concerning UKA for isolated lateral compartment arthritis seemed to be not as good as for medial side. In 1988 our department started using Unicondylar Knee Pros-thesis with a fixed all polyethylene bearing tibial component and resurfacing of the distal femoral condyle. The aim of this study is to report on our personal experience using this type of implant for lateral osteoarthritis with a long follow-up period.

Between January 1988 and October 2003, we performed 54 lateral UKAs (52 patients) and all were implanted for lateral osteoarthritis (3 cases of which were posttraumatic). 52 knees in 50 patients were available after a minimum duration of follow-up of five years (96.3 %). The mean age of the patients at the time of the index procedure was 72.2±1.5 years. The mean duration of follow-up was 100.9 months (range 64 – 189 months).

At follow up, 4 underwent a second surgery: one conversion to TKA for tibial tray loosening at 2 years and 3 revisions for UKA in the medial compartment. No revision surgery was necessary for wear of either of the two components, nor for infection. The mean IKS knee score was 94.9 points, with mean range of motion 132.6° (range, 115–150) and a mean IKS function score totaling 81.8 points. The average femorotibial alignment was 1.8° (range −6° to 12°). Radiolucent lines in relation to the tibial component were appreciated in 6 knees and to the femoral component in 1 knee. Implant survival was 98.08% at ten years.

The UKA with a fixed bearing tibial component and a femoral resurfacing implant is a reliable option for management of isolated lateral knee osteoarthritis. It offers excellent medium-term results for both functional level and implant survival which even currently enable us to widen our selection criteria to include younger patients or those associated with starting patellofemoral osteoarthritis.