- Yuval Krieger, Avia Moses, Eldad Silberstein, Shimon Weitzman, Naftali Liberman, Amiram Sagi Aims: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy. Open decompression of the median nerve is considered the standard surgical treatment for CTS. This article describes a study to assess and compare the clinical efficacy of operative treatment performed by transverse carpal ligament release alone (limited carpel tunnel release (CTR)), to that achieved after transverse carpal ligament release with additional division of the proximal portion of the flexor retinaculum (extended CTR) which is continuous with the deep investing fascia of the forearm. Methods: A retrospective cohort study was performed by telephone interview, using a modified Levine scale to assess symptoms and functional impairment 4–7 years post-operatively in two patient groups who were operated using two different techniques, over a two year period. One group (N = 73) had open CTR by limited transverse carpal ligament division alone, performed by one hand surgeon; the second group (N = 83) had open CTR by division of the transverse carpal ligament and the proximal portion of the flexor retinaculum, performed by another hand surgeon. Findings: Pre-operatively the two groups were similar, both in terms of patient characteristics and of disease severity. Both groups improved significantly. No clinical difference was demonstrated in terms of symptom relief, recurrence or complication rate. Conclusions: This study suggests that adjunctive division of the proximal portion of the flexor retinaculum, although safe, offers no advantage over division of the transverse carpal ligament alone in standard open carpal tunnel release.