Abstract
Aim: To measure contact pressures in vivo in patients with unicompartmental arthritis fitted with osteoarthrosis (OA) braces to see if the arthritic side of the joint is unloaded.
Method: A thin flexible sensor (TekScan) was manoeuvered arthroscopically into the medial compartment of the knee joint under local anaesthesia in patients with unicompartmental OA of the knee undergoing either therapeutic or diagnostic arthroscopy. All 15 patients had been fitted with a brace before the arthroscopy. Measurements were made within the compartment of double leg stance and single leg stance. Ground reaction force using a load cell was measured for 14 patients and the knee sensor data were normalised relative to this. Recordings were then repeated with the patients with different commercially available braces.
Results: The first two groups of patients showed significant reductions in pressures. Normalised knee sensor forces were reduced to 68%(Sd 22%) and 61%(Sd31%). In the last group of patients, reductions in pressure recordings were less between no-brace and brace. Three patients produced low signals suggesting incorrect sensor replacement.
Conclusions:
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Significant unloading of the osteoarthritic compartment could be observed by applying manually a valgus force to the knee.
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Significant unloading of the arthritic compartment of the knee was not observed by applying a brace (up to 10%).
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Measurement of pressures within the osteoarthritic knee is difficult and variable.
The abstracts were prepared by Professor A. J. Thurston. Correspondence should be addressed to him at the Department of Surgery, Wellington School of Medicine, PO Box 7343, Wellington South, New Zealand
