Unusual case of locked trigger thumb due to tophaceous infiltration of the flexor tendon over the wrist: a lesson learned

Discussion

Gout is a form of inflammatory arthritis caused by cellular deposition of monosodium urate crystal. Gouty tophi are chalky material as a result of accumulation of monosodium urate crystals that build up in the soft tissue of an articular joint.

We presented an unusual and rare case of gout in the flexor tendon of the wrist, which occurred in isolation in a patient with no previous history of the disease.

In our case, there was tophaceous gout over the wrist in which paratendinous gouty tophi were found within the flexor pollicis longus tendon, resulting in trigger thumb symptoms and flexion contracture over the interphalangeal joint. During the preoperative clinical assessment, we failed to recognise the correlation between the volar wrist swelling and the flexion contracture of the thumb interphalangeal joint. Due to the trigger thumb symptoms given by the patient and the clinical picture of interphalangeal joint flexion contracture, we treated the case as a severe trigger thumb with surgical release of the A1 pulley. Because of the absence of obvious osteoarthritic change over the interphalangeal joint, we assumed that the fixed flexion contracture was attributed by the stenosing tenosynovitis over the A1 pulley. On retrospect, we should have examined and investigated more carefully over the volar wrist swelling, like ultrasounography. Therimadasamy et al 1 reported ultrasonographic detection of the flexor tendons tophaceous infiltration as a heterogeneous mass.

Gouty tophi presenting as a mass over the wrist are uncommon, and the additional involvement of the flexor tendon resulting in the flexion contracture of the IPJ is even more rare. Kumar et al 2 have presented a similar case of gouty tophi over the volar aspect of the forearm, which was mistaken as tuberculosis tenosynovitis. Tajika et al 3 presented a case of locked trigger finger due to tophaceous infiltration of the wrist flexor tendon.

One must pay particular attention to the soft tissue while operating on patients with gouty arthritis on the hand and wrist region. The skin overlying a subcutaneous tophi should be gently handled in order not to impair the vascular supply.4 Sharp dissection should be used for most infiltrative lesions involving tendons and joint capsules.

Inevitably there exists a debate between radical surgery to avoid recurrence and the avoidance of tendon rupture. Most of the time, the tendon can be kept intact by shaving or curetting the tophaceous surface, followed by medical management resulting into subsequent slow resorption of the remaining tophus.5 However, in cases where there is advanced tophaceous infiltration of the tendon, surgical resection of the involved tendon followed by primary repair or subsequent tendon transfer can be considered.6

This is an uncommon and unusual case of tophaceous infiltration of the flexor pollicis longus tendon, resulting in locked thumb with fixed flexion at the interphalangeal joint. We should keep in mind the differential diagnosis of tophaceous gout in our clinical assessment with a more thorough physical examination and radiological investigation.

The diagnosis of trigger finger may look simple and straightforward at times, but it is of utmost importance to going over all the possible causes in our mind before operating on the patient.