Lesion Size Location Dependency on Maximum Pressure in Osteochondral Defects: Experiments and Finite-Element Analysis

Background: Osteochondral defects (OCDs) in the knee joint have significant clinical implications, particularly regarding contact pressures and pressure distribution. Understanding how these factors are influenced by defect size and location is crucial for developing effective therapeutic strategies.Purpose/Hypothesis: The purpose of this study was to investigate the impact of defect size and location on contact pressures and pressure distribution in the knee joint. It was hypothesized that an increase in defect size would result in elevated contact pressures and alterations in pressure distribution, with specific variations related to defect location.Study Design: Descriptive laboratory study.Methods: The study utilized 6 cadaveric knees, including the patella and fibula, subjected to controlled compressive loading for measuring contact pressures. Simultaneously, computed tomography-based models were created for finite-element analysis (FEA) to investigate the impact of varying defect sizes and locations on contact pressures and pressure distribution in the knee joint, excluding the patellofemoral joint. The study employed analysis of variance to assess contact pressure and defect size association. Comparison between medial and lateral femoral condyles at full extension and 30 degrees flexion angle was performed, followed by post hoc testing. Fisher exact test analyzed peak pressure point location and defect size, categorizing them into medial and lateral.Results: An increase in defect size corresponded with heightened contact pressures on both medial and lateral femoral condyles at full extension (P = .013 for medial and P = .024 for lateral). However, this correlation did not yield significant differences at 30 degrees of flexion (P = .674 for medial and P = .333 for lateral). During mechanical testing, the highest pressures occurred near 5 mm defect dimensions. FEAs showed a significant increase in pressure and circumferential-edge stress with 7-mm defects. Peak contact pressure points shifted laterally with more significant defects.Conclusion: Our study demonstrated the impact of defect size, location, and alignment on knee joint contact pressures. Intervening promptly with defects exceeding 3 mm is crucial, as significant stress levels manifest beyond this threshold. Significant increases in contact pressures were noted with larger defect sizes, particularly between 3 and 10 mm at full extension. Peak pressure points shifted with defect size increments, and alignment variations showed minimal stress variation at 30 degrees compared with 0 degrees. FEA validated increasing contact pressures up to 7 mm defect size, beyond which pressures stabilized or slightly decreased. A concentrated pressure distribution on the medial side was observed. These findings inform our understanding of the biomechanical implications of OCDs.Clinical Relevance: In the field of sports medicine, this research offers valuable insights to clinicians and researchers, elucidating key factors influencing knee joint health and the potential consequences of OCDs.