Chronic Tibial Eminence Avulsion Nonunion with Mechanical Extension Block and Anterior Cruciate Ligament Insufficiency: A Case Report

Abstract

Aims: This case report described a mechanism-based surgical strategy and early outcome for chronic tibial eminence avulsion nonunion causing both a mechanical extension block and anterior cruciate ligament (ACL) insufficiency. Presentation of Case: A 28-year-old woman presented 2 years after a motorcycle injury with recurrent giving-way, a flexed-knee gait, and range of motion (ROM) of 20°–130°. The Lachman test was grade III with a soft endpoint, and the anterior drawer test was positive. Arthroscopy showed a nonunited tibial eminence fragment attached to ACL fibres. Dynamic extension demonstrated fragment-notch impingement; probing showed a lax ACL-bony fragment complex that could not be tensioned. Because reliable fragment reduction and restoration of functional ACL tension were not achievable, the fragment was excised arthroscopically; full passive extension was confirmed before single-bundle ACL reconstruction with a double-loop peroneus longus tendon autograft. At 3 months, ROM was 0°–130°, pain was 0 on the visual analogue scale, and Lachman and anterior drawer tests were grade I. Lysholm and International Knee Documentation Committee subjective scores improved from 51 and 21.8 to 85 and 80.5, respectively. Discussion: Dynamic arthroscopy identified two distinct mechanisms arising from one chronic lesion. However, the combined procedure and rehabilitation preclude attribution of the postoperative improvement to either surgical component independently. Conclusion: In this case, treatment selection was based on mechanical impingement, fragment reducibility, fixation feasibility, and ACL-bony fragment complex competence rather than chronicity alone. The 3-month findings represent early functional recovery only; longer follow-up is required to assess graft durability and sustained stability.