Extensor tendon rupture and three-dimensional computed tomography imaging of the rheumatoid wrist

Extensor tendon rupture on the dorsum of the wrist is commonly seen in patients with rheumatoid arthritis (RA). The diagnosis of tendon rupture is usually straightforward, but it is sometimes difficult in the hand with complex deformity. The purposes of this study were to investigate the reliability of three-dimensional computed tomography (3DCT) imaging of extensor tendons in the rheumatoid wrist and in the normal wrist and to clarify the validity of its clinical application to the diagnosis of tendon rupture in the rheumatoid wrist.

Preoperative 3DCT images of 48 wrists of 45 patients with RA and 3DCT images of 38 wrists of 38 healthy volunteers were reviewed retrospectively by six orthopaedic surgeons who were unaware of all other study data. Extensor tendon rupture was verified by operation on 20 rheumatoid wrists.

Regarding interobserver and intra-observer reliabilities of 3DCT imaging of the extensor tendons, agreement with respect to tendon rupture in this study group was high, and Cohen's kappa (kappa) coefficient was variable, depending on the individual tendon. Positive predictive value (PPV) of tendon rupture in the extensor digiti minimi (EDM), extensor digitorum communis (EDC) V and IV and extensor pollicis longs (EPL) tendons was more than 60%, but those for the other extensor tendons were less than 50%. Negative predictive value (NPV) was more than 96% in all extensor tendons, in both rheumatoid and normal wrists.

Extensor tendons in normal and rheumatoid wrists were well depicted by 3DCT imaging. In the rheumatoid wrists, extensors of the ring and little fingers and the thumb were depicted more accurately than those to the other fingers. 3DCT imaging was clinically applicable to wrists for which it was difficult to diagnose by physical examination a definite cause for the loss of extension of the fingers.