RESUMO
Background: Many procedures to reconstruct osteochondral defects of the elbow radiocapitellar (RC) joint lack versatility or durability or do not directly address the subchondral bone structure and function. Purpose/Hypothesis: To biomechanically characterize the RC joint contact area, force, pressure, and peak pressure before and after reconstruction of osteochondral defects using a novel hybrid reconstructive procedure. It was hypothesized that the procedure would restore the contact characteristics to the intact condition. Study Design: Controlled laboratory study. Methods: A total of 10 cadaveric elbows (mean age 67 ± 2.7 years) were dissected to isolate the humerus and radial head. RC contact area, contact force, mean contact pressure, and peak contact pressure were measured with the elbow at 45° of flexion and neutral forearm rotation at compressive loads of 25, 50, and 75 N. Osteochondral defects 8 and 11 mm in diameter were created at the center of the capitellum; the defects were then reconstructed with a titanium fenestrated threaded implant, countersunk in the subchondral bone, with an acellular dermal matrix allograft sutured in place on top of the implant. Five conditions (intact, 8-mm defect, 8-mm repair, 11-mm defect, and 11-mm repair) were tested and results were compared using repeated-measures analysis of variance. Results: Both 8- and 11-mm defects significantly increased RC mean contact pressure at all compressive loads (P ≤ .008) and significantly increased peak contact pressure at compressive loads of 50 and 75 N (P < .002) compared with the intact condition. Repair of the 8-mm defect significantly decreased RC mean contact pressure at 25- and 50-N loads (P ≤ .009) and significantly decreased peak contact pressure at 50- and 75-N loads (P ≤ .035) compared with the defect condition. Repair of the 11-mm defect decreased mean contact pressure significantly at all compressive loads (P ≤ .001) and peak contact pressure at 50- and 75-N loads (P < .044) compared with the defect condition. Conclusion: RC joint contact pressure was restored to intact conditions while avoiding increased peak contact pressure or edge loading after repairing osteochondral defects related to osteochondrosis with a novel hybrid reconstruction technique. Clinical Relevance: This hybrid procedure that addresses the entire osteochondral unit may provide a new treatment option for osteochondral defects.
RESUMO
BACKGROUND: Component mal-positioning may contribute to a poor clinical outcome after hemiarthroplasty. Eccentric head components, recently introduced, allow posterior offset of the humeral head relative to the shaft so the purpose of this study was to determine effects of mal-aligning humeral head offset. MATERIAL/METHODS: Five glenohumeral joints were each placed in 60 and 90 degrees of shoulder abduction and in apprehension positions using a custom shoulder-testing device. Joint reaction force and contact areas, pressures and patterns were measured. Humeral head offset was then mal-aligned by rotating the eccentric head component 90 degrees and testing was repeated. RESULTS: There were no significant differences in the joint reaction forces in comparison of the hemiarthoplasies that mimicked and mal-aligned humeral offset. A significant increase in total contact area was found only at 60 degrees of abduction, increasing from 137.4+/-32.2 millimeters(2) to 243.4+/-27.0 millimeters(2). (p<0.05) No changes were found in contact pressures; only the patterns of contact were meaningfully different after hemiarthroplasty mal-aligned in humeral offset. In the apprehension position, rather than elongated ovals, there were multiple irregular patterns in the posterior joint. CONCLUSIONS: Meaningful alterations in joint biomechanics did not result from hemiarthroplasty that mal-aligned humeral offset, albeit the mal-alignments studied were small. Glenoid impingement with the humeral metaphysis may occur if portions of the humeral osteotomy surface, not covered by the head component, are not chamfered during the surgical procedure.
