Experimental arthroplasty of the canine hip. Extracellular matrix composition in noninterpositional arthroplasty

In an attempt to establish an experimental model to study the development, maturation, and function of arthroplasty surfaces, noninterpositional hip arthroplasties have been performed on dogs, and the arthroplasty matrix studied over a 12-month period. Macroscopic and microscopic observations are recorded. In all instances, loss of granulation tissue occurred over the pressure-or weight-bearing area of the femoral head. It is concluded that a satisfactory arthroplasty surface can be achieved only if the granulation tissue is protected in the early post-operative phase from the harmful effects of shearing and compressive forces.Biochemical analyses for collagen, hexosamine, and acid mucopolysaccharides were carried out on the tissue which developed in the nonpressure-bearing areas of the arthroplasty surfaces. For the first 2 months, collagen values rose sharply to a level above that in control tissue; peak values were obtained at 4 months after surgery, and thereafter they decreased slightly. Throughout the observation period, the total hexosamine and acid mucopolysaccharide concentration continued to increase. Chondroitin-4 and chondroitin-6 sulfates were detected in significant amounts and appeared first in appreciable quantities 1 month after surgery. The shape of the curve for these matrix components was paralleled by that of keratosulfate, but at a considerably lower level. The supervention of secondary degenerative changes makes an exact interpretation of these findings difficult. However, in a qualitative sense, the arthroplasty matrix of this experimental model contains components identical to those in normal articular cartilage, though obviously quantitative differences exist; these conclusions were supported by the microscopic evidence.It has been demonstrated that the constituent cells of a noninterpositional canine hip arthroplasty surface have adequate potential to produce the necessary matrix components, but the present experimental model is not suited for the more desirable study of a longer time. Other types of arthroplasty are currently under investigation, and the results will be reported in due course.