In vitro study of contact area and pressure distribution in the human knee after partial and total meniscectomy.

Many investigators have attempted to find the cause of the osteoarthritic changes after meniscectomy. Alteration of the mechanical factors resulting in stress concentration, is now thought to be one of the most important causes but few experimental studies have reported the differences in contact area and pressure distribution after partial or total meniscectomy. By using pressure sensitive film, we have calculated the contact area and the pattern of weight distribution in three different situations; intact meniscus, partial and total meniscectomy. The experimental materials were obtained from 5 above knee amputation specimens. The knee joint was fixed in full extension to an Instron machine using an aluminium box and mounting resin. Load was transmitted to the tibiofemoral joint containing the special film, within a physiological range. Analysis of the contact area for each situation (intact meniscus, partial and total meniscectomy) was made by reviewing the film. By measuring the contact area after meniscectomy, we showed that the meniscus performs a load transmitting function in the knee joint. The medial contact area of the tibiofemoral joint with an intact meniscus is always larger than the lateral compartment (1.36:1), but in partial and total meniscectomy the difference between them gradually decreased. There was a minor decrease in contact area after partial meniscectomy and a much greater decrease after total meniscectomy. The degree of stress concentration in the contact area was increased when part or all the meniscus was excised. There was little change of contact area in the opposite, intact side of the joint after partial meniscectomy, but marked change after total meniscectomy.