Radially subluxated extensor tendons after a karate demonstration

Abstract

Traumatic disruption of the extensor tendon mechanism over the metacarpophalangeal joins has become commonly termed as 'boxer's knuckle', with the literature focussing on boxing injuries. Descriptions of the mechanism of tendon subluxation have concentrated on damage to the sagittal band, with ulnar subluxation due to radial sagittal band disruption being the focus. Traumatic radial subluxation has been reported previously, 3 although the mechanism of its occurrence has not being fully uncovered. It has been suggested that boxers should be carefully instructed on good punching technique in order to avoid these injuries. 3 We describe a case of boxer's knuckle in a karate instructor, with a demonstration of good punching technique resulting in radial subluxation of the extensor tendons of the index and long fingers over the metacarpophalangeal joints. Written informed consent was received from the patient described in this report. HistoryA 37-year-old martial arts instructor damaged his dominant right hand whilst demonstrating good punching technique to his class. The injury occurred at the time of one apparently standard well executed punch. He presented to clinic with difficulty forming a comfortable closed fist. ExaminationThe extensor tendon of the index finger could be felt to radially subluxate on flexion of the metacarpophalangeal joint. On flexing the metacarpophalangeal joint of the long finger, the extensor tendon could be felt to dislocate radially, with a palpable gap being felt on the ulnar side. ManagementUlnar sagittal band disruption of the index and long fingers was diagnosed and the option of surgical management offered to the patient. The risks involved were presented to him, including joint stiffness, scar tenderness and potential difficulties in continuing as a martial arts instructor, before proceeding to surgery.A transverse, dorsal incision across the second and third metacarpophalangeal joints was employed. Operative findings were complete ulnar sagittal band rupture of the long finger (see Fig. 1) with a capsular tear and partial ulnar sagittal band rupture of the index finger. Both extensor tendons were recentralised by repairing the ulnar sagittal bands with 2-O Injury Extra (2007) 38, 295-297

Role of the Juncturae Tendinum in Preventing Radial Subluxation of the Extensor Communis Tendons after Ulnar Sagittal Band Rupture: A Cadaveric Study

“…With there being so few cases of radial subluxation reported, there is little precedent concerning management. Surgical repair has been reported as being successful with sagittal band repair alone [ 2 ] and after using an additional extensor tendon slip to aid repair in a case after a failed period of nonoperative management [ 4 ].…”