“Boxer’s knuckle” refers to injury to the extensor hood mechanism that results following resisted extension ("flicking") of the finger or direct trauma to the MP joint, usually involving the radial sagittal band of the middle or ring finger. Often, both the sagittal band and the dorsal capsule are torn. The hallmark of the physical examination is pain over the MCP with a palpable defect in the dorsal capsule, and it is important to examine for EDC subluxation with MP flexion. Sagittal band injuries seen within 3 weeks of injury may be treated nonoperatively with an MP joint flexion blocking splint. Patients presenting later than 2 to 3 weeks after the injury or patients who failed a trial of splinting are candidates for surgical repair.
Hame et al reviewed 27 patients who were treated for Boxer’s Knuckle. The authors concluded that in cases in which conservative treatment has failed, these injuries should be treated with sagittal band repair with centralization of the extensor tendon without repair of the capsule. In the acute period however (less than 3 weeks), as is the scenario for this patient, conservative management with extension splinting should be attempted first.
Araki et al peformed a study of 16 cases of rupture of the extensor hood initially treated conservatively with splinting. While 8/16 responded successfully to nonoperative management, the remaining 8 did not improve with conservative treatment and were eventually treated with surgical repair and closure of the joint capsule when injured.
Illustration A shows a clinical image of a boxer's knuckle and Illustration B displays an axial T2 MRI with a sagittal band rupture. Video V demonstrates a sagittal band reconstruction.
Hame SL, Melone CP Jr: Boxer’s knuckle: Traumatic disruption of the extensor hood. Hand Clin 2000; 16: 375-380.
PMID:10955211 (Link to Abstract)
Araki S, Ohtani T, Tanaka T: Acute dislocation of the extensor digitorum communis tendon at the metacarpophalangeal joint. JBJS Am 1987; 69:
PMID:3571321 (Link to Abstract)