An Unusual Pattern of Acromioclavicular Joint Instability With Coracoid Base Fracture.

BACKGROUND

Concurrent acromioclavicular (AC) joint dislocation and coracoid process fracture is a rare injury pattern, representing a double disruption of the superior shoulder suspensory complex (SSSC) and resulting in mechanical instability. Due to its rarity, there is no consensus on optimal management.

CASE PRESENTATION: A 43-year-old male sustained a right shoulder injury during a snowboarding accident. Imaging revealed a right-sided AC joint dislocation with minimal superior displacement (coracoclavicular [CC] distance 13.6 mm on the right vs. 12 mm contralaterally) and a base-near coracoid fracture (Ogawa Type I and Eyres Type IV). Clinical examination showed clavicular elevation and tenderness over the AC joint, with preserved neurovascular function. Surgical management included AC joint stabilization with a short hook plate and screw osteosynthesis of the coracoid fracture. Postoperative care involved immobilization in a functional brace with staged passive and active-assisted range-of-motion exercises, progressing to strengthening from Week 12.

OUTCOME AND FOLLOW‐UP: At 6 and 12 weeks, radiographs confirmed maintained reduction and fracture healing. The hook plate was removed 3.5 months postoperatively. Follow-up 6 weeks later demonstrated a healed coracoid base, congruent AC joint, minimal pain, and good shoulder function.

DISCUSSION: Surgical fixation restores biomechanical integrity of the SSSC and allows early functional rehabilitation. Combined AC and coracoid fixation represent a viable option, though isolated AC stabilization may also yield favorable outcomes if intraoperative imaging confirms adequate indirect reduction of the coracoid fracture. In our opinion, combined fixation provides a very stable construct with the best chances for anatomical healing and restoration of SSSC integrity.

CONCLUSION

Concurrent AC dislocation and coracoid fracture is a rare injury that requires careful diagnostic assessment, as the coracoid fracture may be overlooked on conventional imaging. This case demonstrates that surgical management with AC stabilization using a hook plate and coracoid screw fixation can achieve excellent radiological and clinical outcomes.