| Sumario: | Purpose: The primary purpose of this study was to investigate the role the ligamentum teres has in providing hip stability using a biomechanical model. The second purpose was to review arthroscopic findings in those with a complete ligamentum teres rupture and question them regarding instability to determine how clinical findings related to the biomechanical model.Methods: A string model was created to examine ligamentum teres excursion during various hip positions. A retrospective review of 350 consecutive surgical patients identified 20 subjects with a complete ligamentum teres rupture that was not repaired at the time of surgery.Results: The model found the ligamentum teres to have the greatest excursion when the hip was externally rotated in flexion (ER/FLEX) and internally rotated in extension (IR/EXT). During operative assessment, it was noted that all 20 subjects had laxity during dynamic impingement testing when their hip was in a position of ER/FLEX. Nine (45%) of the 20 subjects with ligamentum teres rupture were available for follow-up (mean 31 months post-op). Five out of these 9 subjects noted instability: 5 of 9 with squatting (ER/FLEX) and 4 of 9 with crossing one leg behind of the other (IR/EXT). These 5 subjects had osseous risk factors that compromised hip stability including inferior acetabular insufficiency.Conclusions: The ligamentum teres may contribute to hip stability when the hip is in ER/FLEX and IR/EXT. Individuals with osseous risk factors for instability, including inferior acetabular insufficiency, may have instability with squatting (ER/FLEX) and crossing one leg behind of the other (IR/EXT).Level Of Evidence: IV.
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