ASEPTIC LOOSENING IN UNCEMENTED TOTAL HIP-ARTHROPLASTY IN A CANINE MODEL

An in vivo canine model was developed to investigate the histologic an d biochemical parameters associated with aseptic loosening. Thirty-eig ht canines had cementless total hip arthroplasty. Experimental groups were designed specifically to investigate the relative contributions o f implant motion and particulate debris (cobalt chrome alloy, titanium aluminum vanadium, and polyethylene) on the resultant periprosthetic tissues. Tissues from a stable, well-ingrown prosthesis provided a con trol. Importantly the histologic and biochemical characteristics of th e experimentally induced membranes consistently correlated with previo us in vitro reports of tissues retrieved at revision surgery for asept ic loosening. Implant motion and all 3 particulate debris groups resul ted in increased numbers of macrophages in the periprosthetic membrane s. The histologic findings paralleled the increase in levels of bioche mical mediators of bone resorption as measured by collagenase, gelatin ase, prostaglandin E(2), and interleukin-1 activity. The most striking results were seen in the histology and biochemistry of the particle g roups with highly cellular membranes showing increased biochemical act ivity when compared with controls. The clinical relevance of this work lies in the description of an in vivo model of aseptic loosening that can be used to investigate the effects of numerous variables implicat ed in aseptic loosening, Ultimately, the model may serve as a basis fo r developing therapeutic interventions.