Comparison of replacement prostheses for segmental defects of bone. Different porous coatings for extracortical fixation
Okada, Y.; Suka, T.; Sim, F.H.; Gorski, J.P.; Chao, E.Y.
Journal of Bone and Joint Surgery. American Volume 70(2): 160-172
1988
ISSN/ISBN: 0021-9355 PMID: 3343260 Document Number: 320132
The extent of extracortical bone-bridging and ingrowth into porous-coated prostheses for the stabilization of segmental defects was studied in a canine model. Initial fixation of the implant was achieved using bone cement. Autogenous bone grafts were applied over the porous-coated segmental portion of the prosthesis to stimulate the ingrowth and formation of bone. At twelve weeks, bone-bridging and ingrowth occurred uniformly in both the titanium fibermesh and the cobalt-chromium-molybdenum beaded prostheses. Maximum formation of osseous tissue over the implants occurred at two to four weeks. More bone formed in the posterior aspect of the prosthesis. At twelve weeks, 26 per cent of the porous space of the titanium fibermesh prosthesis and 47 per cent of the porous space of the cobalt-chromium-molybdenum beaded prosthesis were filled with bone. The torsional strength and stiffness of the prosthetic midsection that contained a conical coupling joint were increased significantly due to bone-bridging and ingrowth. The cortical bone that was apposed to the segmental prosthesis showed an increase in porosity. The use of bone cement did not appear to impede new-bone formation extracortically. The initial stability of the implant and the application of sufficient autogenous bone grafts are two important factors that contribute to the ultimate stable fixation of an implant by extracortical bone formation. CLINICAL REVELANCE: Segmental replacement for bones and joints is indicated in patients who have had resection of a musculoskeletal tumor, severe trauma, or non-union; for salvage of a failed joint arthroplasty; and for certain metabolic bone diseases that involve massive osseous defects. Prosthetic replacement using a custom-made metal prosthesis has been plaqued with complications, mainly involving loosening of the stem and fracture. The proposed concept for the design and fixation of implants may provide an improved outlook for limb and joint-salvage procedures.