Extensor tenolysis and intrinsic release of the hand
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Adhesions of the extensor tendons can occur following operations or trauma. One of the common causes of extensor tendon adhesions is a fracture fixation of the metacarpal or proximal phalanx. When this occurs in the context of a crush injury hand often there can be scarring of the intrinsic muscles of the hand. This results in a combination of extrinsic and intrinsic tightness.
To understand the pathology of this condition and to recognise it one needs to understand the anatomy of extensor tendons and instrinsic muscles. The extensor mechanism of the fingers are made up of EDC tendons, EIP and EDM which arise in the forearm. At the MCP joint level they form the extensor hood and continue into the fingers as central slip and lateral bands. The intrinsic muscles, namely the lumbricals and interossei arise in the hand and are attached to the lateral bands. Therefore if there is scarring of the long extensor tendons or the instrinsic muscles patient looses the flexion of the fingers as the lateral bands are not able to move. To differentiate the two, one uses the Bunnell’s Instrinsic tightness test. In this test the PIP joint passive movements are checked with MCP joint in flexion and hyperextension. When there is tightness of the extrinsic muscles, the PIP joint flexion is improved when the MCP joint is hyperextended and the reverse is true with intrinsic tightness. This is because with MCP joint hyperextension the long extensors are relaxed and the intrinsics are stretched.
Though both lumbricals and interossei are involved in the scarring following a crush injury, it is the lumbrical which usually causes the loss of flexion. Lumbricals originate from FDP tendons and are four in number. The radial two are supplied by median nerve and the ulnar two by ulnar nerve. Lumbricals flex the MCP joints and extend the IP joints.
The patient in the case series sustained a crush injury to is left hand in an industrial press. He had closed fractures of four metacarpals and three proximal phalanges. They were treated with open reduction and internal fixation. After six months of hand therapy the plate and screws were removed and extensor tenolysis performed. However after six months it was noted that over the middle finger he had reduced flexion and on examination intrinsic tightness test was positive. A revision tenolysis was performed along with intrinsic release.
Author: Mr Rajive Jose FRCS
Institution : The Queen Elizabeth Hospital ,Birmingham ,UK.