Background. It was hypothesised that preserving a layer of gliding tissue, the parietal layer of the ulnar bursa, between the contents of the carpal tunnel and the soft tissues incised during carpal tunnel surgery might reduce scar pain and improve grip strength and function following open carpal tunnel decompression. Methods. Patients consented to randomisation to treatment with either preservation of the parietal layer of the ulnar bursa beneath the flexor retinaculum at the time of open carpal tunnel decompression (57 patients) or division of this gliding layer as part of a standard open carpal tunnel decompression (61 patients). Grip strength was measured, scar pain was rated and the validated Patient Evaluation Measure questionnaire was used to assess symptoms and disability pre-operatively and at eight to nine weeks following surgery in seventy-seven women and thirty-four men; the remaining seven patients were lost to follow-up. Results. There was no difference between the groups with respect to age, sex, hand dominance or side of surgery. Grip strength, scar pain and Patient Evaluation Measure score were not significantly different between the two groups, although there was a trend towards poorer subjective outcome as demonstrated by the questionnaire in the group in which the ulnar bursa within the carpal tunnel had been preserved. Preserving the ulnar bursa within the carpal tunnel did however result in a lower prevalence of suspected wound infection or inflammation (p=0.04). Conclusions. In this group of patients, preservation of the ulnar bursa around the median nerve during
