Abstract
Dear Sir,
A 46-year-old businessman had been holding a can with his right hand when he fell heavily on his fully flexed right wrist. He noticed severe pain from the dorsum of the distal forearm to the wrist joint at the time of injury, and he could not extend his index finger. At his first visit to our clinic, there was diffuse dorsal swelling and tenderness from the distal forearm to the hand, and he could not extend the metacarpophalangeal (MP) joint of the index finger. However, he could fully extend his other fingers and the proximal interphalangeal (PIP) joint and distal interphalangeal (DIP) joint of the index finger. The dynamic tenodesis effect could be demonstrated except in the index finger. There was no sensory disturbance around the hand and wrist, and no clinical or laboratory evidence of inflammatory arthropathy. Plain radiographs were normal. On 3D CT images, the distal tendon stump of extensor indicis proprius (EIP) was located on the dorsum of the hand. Although the tendon stump of the index extensor digitorum communis (EDC) was not identified, the tendon was slack and redundant at the same site (Fig 1).
Closed rupture of the EIP and the index EDC tendons over the distal forearm was suspected. At exploration, avulsion rupture of both tendons at themusculotendinous junction was confirmed (Fig 2). There was no evidence of synovitis or osteoarthritis. The distal stump of the index EDC was sutured to the middle EDC in an end-to-side fashion with the interlacing suture technique, and the EIP was sutured with the tendinous remnant of the proximal stump in an end-to-end fashion. A splint holding the wrist in 20° extension and all four fingers in full extension was worn for 3 weeks after surgery, and then motion exercise was started. Six months after surgery, the active range of the index MP joint motion had recovered well.
There was no evidence of a predisposing cause of tendon rupture such as inflammatory arthropathy or distal radius fracture in this case, suggesting that the mechanism was purely traumatic. Traumatic closed extensor tendon rupture at the musculotendinous junction caused by forced wrist and finger flexion has been rarely documented in the literature (Mudgal et al., 2007; Stuart and Briggs, 1993; Takami et al., 1995). In these reported cases, the fingers and wrist were forcibly flexed when a work glove was caught in a machine or a gymnast’s leather grip became entangled in the high bar; most of the cases involved multiple extensor tendons, and were treated with tendon transfer or end-to-side suture with an uninjured tendon. However, the energy of these injuries is thought to be more severe than that of the present case.
The dynamic tenodesis effect, which is spontaneous finger extension during wrist flexion, requires the continuity and normal gliding of the extensor tendons, and it is well known that this effect appears strongly in the index finger. In our case, in which the patient simply fell down on his hand, the wrist joint was exposed to the sudden unexpected impact of full flexion, and the index extensor tendons, which were severely loaded at one of the dynamically weak points in the musculotendinous unit (McMaster, 1933).