Demographics, radiographic characteristics, treatment, and classification of pediatric thumb bony Ulnar Collateral Ligament (UCL) injuries

Background: Pediatric thumb ulnar collateral ligament (UCL) injuries usually have osseous involvement presenting as a Salter-Harris III avulsion fracture from the base of the proximal phalanx. There is limited guidance about when surgical or non-surgical treatment is more appropriate. Methods: Patients with thumb bony UCL injuries who presented to a large pediatric hospital between 2007 and 2017 were retrospectively identified. Demographics, fracture pattern, treatment, clinical course, and outcomes were collected. Radiographic measurements included size and displacement of fracture fragment as a percentage of the proximal phalanx base articular surface. A classification system was developed incorporating clinical stability of the metacarpophalangeal joint and quantity of displacement. Results: Sixty-five patients were included (47 males and 18 females). The mean age at time of injury was 14.8 SD 1.9 yrs old. 46 (71%) injuries occurred during sporting activities. 50 (77%) patients underwent nonsurgical management with immobilization, and 15 (23%) patients were treated surgically with open reduction internal fixation. For patients treated surgically, the mean fragment size was 28.2% SD 6.8% of the articular surface compared to 14.3% SD 12.5% of those treated non-surgically ( P <0.0001). The mean fracture displacement for surgically treated patients was 32.7% SD 19.0% compared to 11.4% SD 7.3% of those treated non-surgically ( P <0.0001). Overall, 100% of patients reported they were able to return to their previous level of activity. Conclusion: Many pediatric thumb bony UCL injuries can be treated non-surgically. A classification system based upon joint stability and fracture displacement may help guide appropriate management of these injuries.