Acetabular Insertion Avulsion Fracture of the Ligamentum Teres in a Child: A Case Report

Background/Objectives: Bony avulsion at the acetabular insertion of the ligamentum teres is rare in children and may be mistaken for a loose body. Case Presentation: A 12-year-old boy had persistent left hip pain and restricted motion after a road-traffic accident without documented dislocation. Radiographs suggested acetabular injury, prompting computed tomography (CT), which showed inferior acetabular irregularity and an intra-articular fragment. Magnetic resonance imaging (MRI), obtained to assess associated soft-tissue injury, showed effusion and periarticular edema but did not establish the fragment’s attachment. Arthroscopy identified a 15 × 10 mm notch-adjacent osseous fragment tethered to the ligamentum teres, with an intact femoral insertion and separate labral and chondral lesions. The fragment was excised because reliable arthroscopic fixation was not considered feasible under the operative conditions. After traction release, passive examination showed maintained concentric reduction without gross instability. At approximately 5 years, the modified Harris Hip Score was 100/100, pain was absent, and the patient had returned to sports; no contemporary imaging was available. Discussion: Arthroscopy distinguished a ligament-attached insertion avulsion from a free loose body. Previous excision reports provide a precedent, not comparative evidence favoring excision over fixation. Conclusions: Arthroscopy clarified the injury when imaging was indeterminate. The favorable outcome is limited to clinical and functional recovery, not long-term structural preservation.