Osteochondral reconstruction of a non-weight-bearing joint using a high-density porous polyethylene implant

Currently, there is no reliable reconstructive modality allowing anatomic r esurfacing of traumatic digital osteochondral articular defects. The purpos e of the present study is to demonstrate the utility of Medpor, a high-dens ity porous polyethylene (HDPP) scaffold biomaterial that can (1) be readily contoured to fit any joint defect, (2) permit stable internal fixation, an d (3) permit osteocyte and chondrocyte ingrowth and subsequent articular ca rtilage resurfacing necessary to restore joint congruity. HDPP has gained w ide acceptance for use in craniofacial and skeletal reconstruction and augm entation. An avian non-weight-bearing joint model was designed to study the role of the HDPP implant in small joint reconstruction. An osteochondral d efect was created with a 5-mm circular punch in the humeral articular surfa ce of both glenohumeral joints of 32 adult White Leghorn chickens. In each animal, one defect was press-fitted with a correspondingly sized HDPP impla nt (HDPP implant group); the contralateral defect was filled with the origi nal osteochondral plug (isograft group) or left unrepaired (control group). At 2 weeks, and 1, 3, and 6 months,joints from each group were harvested a nd evaluated. Over the 6-month study period,joints in the control group dem onstrated healing with dense collagenous scar tissue leaving residual defec ts at the articular surfaces and significant degenerative disease of the gl enohumeral joints radiographically. Joints in the isograft group demonstrat ed near-complete resorption with some preservation of the cartilaginous cap but overall depression of the articular surface and significant degenerati ve joint disease. Joints in the HDPP implant group demonstrated stable fixa tion by highly mineralized bony trabecular ingrowth, preservation of the ar ticular contour of the humeral head, and no evidence of significant degener ative joint disease. These findings indicate a potential role for this high -density porous polyethylene implant in the reconstruction of small joint a rticular and osseous defects.