Closed Traumatic Avulsion of Extensor Digitorium Communis and Extensor Indicis Proprius of Index Finger at the Musculotendinous Junction

Abstract

Closed traumatic rupture of tendons at the musculotendinous junction occurs when there is a sudden longitudinal pull of the tendon against a contracting muscle as in resisted extension or flexion of a finger [1]. The weakest point in the whole musculotendinous unit is however at the distal insertion point of the tendon into bone as described by Boyes [2]. When considering the extensor tendons in isolation, the most closed ruptures occur at the insertion of the tendon on the distal phalanx or the attachment of the central slip at the base of the middle phalanx.Introduction: Closed traumatic rupture of extensor tendons of the fingers at the musculotendinous is rare. In fact the common sites of a closed rupture are distal attachment at the distal phalanx as well as at the attachment of the central slip at the base of the middle phalanx. The diagnosis of these injuries at the latter sites is straightforward. Case presentation: We present a 19 year-old right hand dominant motor mechanic male patient who sustained injury of his left forearm while swinging from gymnastic bars. He reports that while swinging, he felt a violent snap at the dorsum of his left forearm while his body swung down from a height. He thinks that the grip of the left hand did not release in time following the downward swing of his body. He presented few days after the injury complaining of pain, swelling and inability to actively extend the index finger. On surgical exploration, it was documented that both the extensor digitorium of the index as well as the extensor indicis proprius were torn at their musculotendinous junctions. Both tendons were sutured side to side before the resultant joined tendon was sutured to the extensor tendon of the middle finger. A below-elbow volar slab was applied for 6 weeks followed by hand therapy. The patient was seen for some time and came back only once for follow-up. At 8 months postoperatively, he was back to his work with full recovery demonstrating isolated index finger extension. Discussion: Closed traumatic rupture of the extensor tendons at the musculotendinous junction is very rare. This case serves to highlight, the peculiar mechanism of injury; the violent snap that results from the rupture and the presented clinical picture. Like this case, if surgery is done in time, a good outcome is to be expected when side-to-side suturing of the two tendons is done and the resultant joined tendon is sutured to the adjacent middle finger extensor tendon.