Ulnar head hemiresection with interposition and extensor reconstruction
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Patients with distal radio-ulnar joint (DRUJ) arthritis, particularly but not exclusively due to systemic inflammatory arthritis, may develop painful dysfunction of their DRUJ, with well localised pain, restriction of forearm rotation and, potentially, extensor tendon dysfunction. The extensor tendons pass from the forearm into the dorsum of the hand in 6 different compartments, each containing different tendons.
On the radial side of the wrist, the 1st and 3rd dorsal compartments carry tendons to the thumb, and the 2nd dorsal compartment the tendons of the two radial wrist extensors. The finger extensors to all four fingers (extensor digitorum communis- EDC) pass in the 4th dorsal compartment on the dorsal aspect of the radius (along with the independent extensor to the index finger, extensor indicis proprius (EIP)). The independent extensor to the little finger, extensor digiti minimi (EDM) passes in the 5th dorsal compartment, which is found immediately overlying the longitudinal joint line of the DRUJ, and the extensor carpi ulnaris (ECU) tendon is found in its own compartment (the 6th dorsal compartment), usually found in a groove on the dorso-ulnar aspect of the ulnar head.
Due to its position over the DRUJ joint line, the extensor digiti minimi (EDM) tendon is vulnerable to synovitis and tenosynovitis due to attrition from ulnar head osteophytes, on occasion proceeding to rupture. Tenosynovitis due to the DRUJ arthrosis may cause attenuation and sequential rupture of the tendons of EDC, a condition eponymously called Vaughan-Jackson syndrome. Classically tendon loss usually progresses sequentially from ulnar to radial (little-ring-middle-index). The earliest potential clinical sign, an inability to independently extend the little finger, may be masked by continuity of the EDC tendon to the little finger still enabling the little finger to be extended actively with the adjacent digits. Even after this EDC tendon has ruptured, the little finger may appear to actively extend due to connections between the EDC tendons in the hand, called junctura tendinae. Patients with DRUJ arthritis who are not ready to accept surgery should therefore be instructed to ensure that they can independently extend their little finger every month, seeking review if this becomes increasingly painful or difficult.
Depending on how many tendons have ruptured, different reconstructive options exist through a combination of “buddying” tendon stumps together into functional units with an appropriate relative tension (little combined with ring or the middle combined with index) and transferring motor units (tendons from other muscles) onto the combined distal stumps in order to restore extension of the digits. This will improve function, but the surgery should be combined with steps to debride the DRUJ and “smooth-off” the ulnar head even if the joint function is good to minimise the risk of further tendon ruptures.
One key point with this technique is to be sparing with the resection of the ulnar head in order to minimise radio-ulnar convergence, but be sure to remove enough distally to eliminate ulno-carpal abutment; this technique produces good clinical results.
Author:Chris Little FRCS (Tr & Orth)
Institution: The Nuffield Orthopaedic centre, Oxford, UK.