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01.12.2015 | Research article | Ausgabe 1/2015 Open Access

BMC Musculoskeletal Disorders 1/2015

Metal backed fixed-bearing unicondylar knee arthroplasties using minimal invasive surgery: a promising outcome analysis of 132 cases

BMC Musculoskeletal Disorders > Ausgabe 1/2015
Joel Baur, Lukas Zwicky, Michael Tobias Hirschmann, Thomas Ilchmann, Martin Clauss
Wichtige Hinweise

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

JB analyzed the data and wrote the manuscript, LZ did the statistical analysis, MTH wrote the manuscript, TI planed the study and wrote the manuscript, MC planed the study, analyzed the data and wrote the manuscript. All authors read and approved the final manuscript.
Level of evidence: Level IV (Therapeutic study, case series with no comparison group)



Unicondylar knee arthroplasty (UKA) is a well-established treatment for isolated osteoarthritis (OA) of the medial knee compartment. Aim of this retrospective study was to evaluate the early clinical and radiological outcomes of a consecutive series of patients treated with medial metal backed fixed-bearing UKA. Furthermore, the influence of the component orientation on the outcome was analyzed.


From 09/2006 to 11/2010 106 patients (132 knees; 69 ± 9 years) were treated using a metal backed fixed-bearing UKA with a MIS approach. All patients underwent a standardized clinical and radiological follow-up at 6 weeks, 1, 2 and 5 years. Mean follow-up was 3.4 ± 1.0 years. Two patients (three UKAs) deceased and two patients (two UKAs) were lost to follow-up. Three different survival analyses were performed using three different endpoints defining failure: (a) revision with exchange of any UKA component (b) aseptic loosening and (c), a worst case scenario, where it was assumed that all progressive radiolucencies would lead to aseptic loosening and thus these were additionally counted. Clinical outcome was assessed using the American knee society score (AKS) and the Oxford knee score (OKS). Radiographic analysis was done according to the American Knee Society Evaluation and Scoring System adapted for UKA and correlated with the AKS and OKS.


Five UKAs (3.8 %) were revised to total knee arthroplasties (TKAs) after a median of 25 (10–33) months. Five year survival was 95.2, 97.5 and 87.7 % for the aforementioned endpoints. At final follow-up the median AKS knee score was 99 (50–100) points and the median AKS function score was 100 (60–100) points. The median OKS was 43 (8–48) points. Clinical outcome was independent of the component orientation.


Fixed-bearing UKA showed excellent clinical and radiological results at up to 5 years follow-up. Outcome was independent of component orientation.
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