Bilateral fast magnetic resonance imaging of the operated carpal tunnel

Our aim was to quantify the structural changes of the carpal tunnel including area and volume after surgical release. We studied 28 patients who underwent 31 operations for carpal tunnel syndrome (CTS), mean age 54.7 years (range 32-78). All had abnormal nerve conduction studies. Magnetic resonance imaging (MRI) of both wrists was done before and after operation using two fast imaging sequences, turbo spin echo (TSE) and fast field echo (FFE). The same surface coils and parameters were used in both instances. With a computerised analyser we calculated the volume of the whole tunnel from inlet to outlet before and after operation and the wrist volume:carpal tunnel volume ratio. The intensity of the magnetic resonance signal emitted by the median nerve was assessed in all wrists before and after operation. The mean (SD) volume of the tunnel in 31 wrists with CTS was 11511.7 (2857) mm3 before and 13803.4 (3034.9) mm3 after operation (p = 0.0001). The mean (SD) relative signal intensity of the median nerve was 1.7 (1.8) preoperatively and 1.3 (1.1) postoperatively (p = 0.19). Other postoperative changes included persistent nerve enlargement (n = 21), misalignment of the tendons (n = 20), fibrous tissue deposits (n = 20), fat tissue deposits (n = 21), and muscle oedema (n = 6). The modifications of the carpal canal as a consequence of open surgical release (including increased volume and displacement of the flexor tendons) argue for the use of an endoscopic procedure in the treatment of CTS.