Treatment of Second and Third Carpometacarpal Joint Instability in Elite Boxers

Background: Instability of the second and third carpometacarpal joints (CMCJs) is a rare disorder. This study aimed to present treatment outcomes of CMCJ instability in elite boxers. Methods: Combat-sport athletes with second and third CMCJ instability treated at our hospital between 2011 and 2023 were included. Diagnosis and severity were assessed using lateral stress radiographs (Iijima-Kusunose [IK] classification). Treatment was based on the IK classification. Patients requiring surgery underwent arthrodesis using a single headless compression screw. Data collected included age, sex, symptom duration, type and level of sport, hand involved, number of CMCJs involved, IK grade, treatment type and follow-up period. The lead and rear hands were defined by boxing stance, independent of hand dominance. Outcome measures were pain (visual analogue score [VAS]), postoperative stability and complications. Results: Twenty athletes (19 male, 1 female; mean age: 24.7 years) were included. All had unilateral injuries, involving the lead hand in 2 and the rear hand in 18. There were 5 patients with grade 1, 3 with grade 2 and 12 with grade 3. Seven were treated conservatively and 13 surgically. Mean symptom duration was 15.8 weeks in conservatively treated and 1.7 years in surgically treated patients. All returned to their pre-injury competition level and were pain-free without residual instability. The mean follow-up was 6.7 years (range: 1.8-11.7 years). Three surgical patients had complications (one screw fracture, one metacarpal base fracture and one loosening), all resolving without sequelae. Conclusions: The IK classification-based strategy and a simplified single-screw arthrodesis provide an effective framework for diagnosing and treating CMCJ instability in elite combat-sport athletes. Level of Evidence: Level IV (Therapeutic).