Primary anterior cruciate ligament reconstruction for simultaneous femoral-sided tear and tibial avulsion fracture: proposing the term “Bipolar Anterior Cruciate Ligament Injury”: case report.

Avulsion fractures of the anterior cruciate ligament (ACL) are rare in adults and typically involve the tibial insertion. Femoral-sided avulsion or proximal detachment is exceedingly uncommon, particularly in skeletally mature individuals. To date, simultaneous disruption of both the tibial and femoral attachment sites-whether via ligamentous rupture or bony avulsion-has not been systematically described in the literature. We present a rare case of a 23-year-old female who sustained acute knee trauma resulting in a dual-site ACL injury. Initial radiographs demonstrated a displaced tibial spine fracture consistent with a Type III avulsion. Preoperative MRI revealed hyperintense signal changes at the femoral origin of the ACL, suggestive of a proximal tear. Arthroscopic evaluation confirmed a bipolar pattern of injury: an avulsed tibial eminence fragment and a proximal detachment of the ACL from its femoral origin. Due to the non-viability of the remnant ACL tissue and the complexity of anatomical repair, the avulsed tibial fragment was excised, and a primary single-bundle ACL reconstruction was performed using a semitendinosus tendon autograft. The patient achieved excellent clinical outcomes, with restoration of knee stability, full range of motion, and negative Lachman and pivot-shift tests at follow-up. We propose the term "Bipolar ACL Injury" to describe this unique pattern of simultaneous disruption at both the femoral and tibial insertion sites. This terminology may also encompass previously reported cases involving combined failure of the ACL's origin and insertion. Early recognition of this injury pattern is critical for surgical decision-making, as tibial fixation alone may be insufficient. MRI plays a pivotal role in preoperative diagnosis. In cases where anatomical repair is not feasible, primary ACL reconstruction provides a reliable and definitive treatment approach. LEVEL OF EVIDENCE: V.