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Background Crush injury of nerves is a common condition but the biomechanical integrity of the human peripheral nerve after crushing is unknown. This study aims to investigate the impact of crush injury on human digital nerves based on different compressive forces. Materials and methods Twenty digital nerves were harvested from three fresh-frozen cadaver hands. The original diameters of proximal, middle and distal end of nerve segment were measured. The midst of each digital nerve was compressed by a customized mechanical system, at 1N, 3N and 5N for 30sec. The diameters were measured again within 1 minute after the nerve crush test was performed. The digital nerve was then subjected to biomechanical test to measure its ultimate tensile strength, stiffness, maximum stress and strain. Deformity of digital nerve was computed based on the diameter of middle nerve segment before and after crush test. Results No significant difference was found in between groups for ultimate tensile strength ( p =0.598) , stiffness ( p =0.593) , maximum stress ( p =0.7) and strain ( p =0.666) . The deformity of nerves under the compression of 1N, 3N and 5N was computed at 72.1%, 54.2% and 45.9%. The effect of compression on the deformity of nerves was statistically significant ( p <0.001) . Conclusions It was found that the compressive forces have no impact on the biomechanical integrity of peripheral nerves but the deformity of nerves could be severely caused by low compressive force. It is suggested that the management of nerve crush injury shall be taken immediately and focus on neurophysiological function and degeneration of nerves for a crush with low compressive force and short duration.

Background: The single looped suture modified Lim/Tsai technique is widely used for flexor tendon repairs. It has been shown to possess better biomechanical properties and require less repair time per tendon as compared to the double looped suture original Lim/Tsai technique. However, there is no clinical data on the modified technique. Methods: The retrospective study included zone 2 flexor tendon repairs made using the modified Lim/Tsai technique from January 2008 to December 2014. Clinical outcome was assessed using the revised Strickland and Glogovac criteria, which categorises repairs based on the total active motion of the repaired digit. Results: Sixty-two patients with 74 digits were included. The overall mean total active motion was 122°. The overall satisfactory outcome of the modified Lim/Tsai technique was 81.1%. The rupture rate of the modified Lim/Tsai technique was 2.7%. Using multivariate linear regression model, we found that outcomes were negatively influenced by subzone 2C and crush/saw injuries, but not by concomitant neurovascular injuries or post-operative follow-up duration. Conclusions: Based on this retrospective study of patients with zone 2 flexor tendon injuries, the clinical outcomes of modified and original Lim/Tsai techniques are comparable. As such, there is no clinical evidence favouring one over the other.

Background: Patients with ulnar-sided wrist pain and positive ulnar fovea sign are usually treated nonsurgically before surgical options are considered. However, the outcomes of nonsurgical management are unknown. Many of these patients also have unstable distal radioulnar joint, but there has been no comparison between the outcomes of these patients with stable and unstable distal radioulnar joint. The objectives of this study are to (1) determine the outcomes of nonsurgical and surgical treatment of patients with positive ulnar fovea sign, and (2) compare the outcomes of patients with stable and unstable distal radioulnar joint. Methods: A retrospective analysis of the outcomes of patients with ulnar sided wrist pain and positive fovea sign was performed from March 2009 to December 2014. Outcomes were measured based on patient-reported pain improvement, grip strength and range of motion of the affected wrist before and after treatment. A total of 100 wrists in 98 patients were reviewed. Results: 54% of wrists managed nonsurgically experienced pain improvement. 83% of wrists managed surgically experienced pain improvement. The mean grip strength increased by 2.8 kg and 2.7 kg, while the range of motion decreased by 14° and 5° after nonsurgical and surgical treatment respectively. When comparing patients with stable and unstable distal radioulnar joint, there were statistically more wrists with unstable distal radioulnar joint that experienced pain improvement after treatment. Conclusions: The study showed that there is a role for nonsurgical treatment for wrists with positive ulnar fovea sign with more than half of the patients experiencing pain improvement. We also found that positive ulnar fovea sign patients with unstable distal radioulnar joint had better pain outcomes compared to those with stable distal radioulnar joint.