[Compression of the ulnar nerve at the wrist due to an arthro-synovial cyst. Apropos of 2 cases].

The authors report two cases of ulnar nerve compression at the wrist due to arthrosynovial cysts arising from the hamatotriquetral joint. The absence of strict parallelism between the type of neurological deficit observed, the site of the cyst and the site of compression requires ulnar nerve release as far as its division in the pisi-unciform hiatus, where the section of the hypothenar fibrous arcade and pisi-unciform ligament is essential. Complete recovery of these 2 patients confirmed the favourable prognosis of this form of compression provided surgical treatment is performed early and rigorously.