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KneeFurther Opinion

The low contact stress patellofemoral replacement

C. P. Charalambous, Z. Abiddin, S. P. Mills, S. Rogers, P. Sutton, and R. Parkinson

J Bone Joint Surg Br 2011 93-B: 484-489.

This is the first independent study published on the early results of the LCS patellofemoral arthroplasty. Fifty one consecutive patellofemoral arthroplasties are followed retrospectively for a maximum of 60 months. The results at 3 years were rather disappointing, with an estimated 3 year survival rate of 63% (95% CI 47% to 80%) with revision as the end point and 46% (95% CI 30% to 63%) with revision as well as ongoing moderate/severe pain as the end point.

The authors have also attempted to identify and analyse the main causes of failure of this prosthesis. Based on findings at revision surgery, they feel that the mobile polyethylene may be the intrinsic weakness of this prosthesis leading to most of the observed complications. The poly bearing was designed to be mobile on the metal base, so that its movement would aid patellar tracking. However, a significant number of bearings were found to have reduced or no mobility due to surrounding soft tissue overgrowth. Other findings at revision included excessive wear, dislocation or subluxation of the polyethylene patellar component and extensive metallosis due to metal on metal articulation of the patellar and trochlear components at the extremes of motion, leading to chronic inflammation and pain.

This paper emphasises the importance of proper understanding of patellofemoral mechanics in the design of the isolated patellofemoral arthroplasty.  It also conveys a very clear clinical message: on the basis of their results the authors have discontinued using the LCS patellofemoral arthroplasty and recommend caution if it were to be used by others.

 

Dr Dimitrios Karataglis MD, PhD

Consultant Orthopaedic Surgeon

1st Orthopaedic Dept, Aristotelian University of Thessaloniki

“G. Papanikolaou” Gen Hospital

Thessaloniki, Greece

Email: dkarataglis@yahoo.gr