Summary
Fixation methods for osteochondral shell grafts were studied using replace-ment of a femoral trochlear autograft in rabbits as the model. Twenty skeletally mature rabbits were divided into four groups with five rabbits in each. The articular cartilage of the femoral trochlea, including 2.0 mm of subchondral bone, was removed using a sagittal bone saw. The grafts were immediately reattached using either small Kirschner pins (K-pins), polydioxanone pins (PDP), polydioxanone suture (PDS), or polymethylmethacrylate (PMMA) cement. Six months postoperatively the rabbits were killed and the graft sites compared to the contralateral control using radiography, gross examination, Safranin-O and H & E staining, and sulphate-35 radioactive uptake. Mild degenerative joint changes were evident radio-graphically in all of the operated joints. Articular surface defects at the graft sites were common and included small craters and erosions; a few had larger areas devoid of cartilage. Defects associated with the pin entrance sites were common in the K-pin and PD P groups. The PDS group had the least number of animals with articular surface defects. Safranin-O staining was complete in the PDS group, partial or complete in the K-pin and PD P groups, and partial in all of the joints in the PMM A group. H & E preparations of the cartilage sections were graded from 1 (normal cartilage) to 5 (multiple fissures, severe degradation). The PDS group had a mean (SD) score of 1.8 (0.8), the PD P group 2.4 (1.1), the K-pin group 2.5 (1.3), and the PMM A group 4.6 (0.6). The scores for the PMM A group were significantly greater then the scores for the other groups (p <0.05). The mean (SD) for radioactive counts per minute/mg tissue in treated graft sites as a percent of control was PDS: 130 (83); PDP : 115 (14); K-pins: 92 (42); PMMA : 91 (29). The relative percentages for radioactive uptake were not significantly different (P >0.05). Graft fixation using PDS, PDP, or K-pins was technically easy to perform and the results were generally satisfactory. Fixation using PMM A was technically demanding and histological evidence of moderate to severe cartilage degradation was present in all treated joints.
Femoral trochlear autografts in rabbits were used to study fixation methods for osteochondral graft fragments. Six months after the operations the graft sites were evaluated using radiographs, gross examination, Safranin-O and H & E staining, and sulphate-35 radioactive uptake. Grafts stabilized using polydioxanone suture had the least number of articular surface defects and the most complete Safranin-O staining.
Keywords
Osteochondral graft - fixation - rabbit - cartilage defects
