Ulnar Nerve Strain in Functional Elbow and Shoulder Motions

Background: Shoulder and elbow motions can affect ulnar nerve strain. However, there is no evidence that links this kind of strain to specific activities. The purpose of this study was to examine ulnar nerve strain at the elbow resulting from normal daily activities. Methods: This study was conducted using thirty fresh frozen cadaveric elbows from subjects who had no deformities or history of previous upper extremity surgery. Strain was calculated based on nerve elongation. Ulnar nerve strain at the elbow from motion related to common daily activities was measured in both normal nerves and nerves in which gliding motion was restricted. The results of these measurement were then compared. Results: Activities related to extreme elbow and shoulder motions, such as cellular phone use, yielded an average strain of 6.3%. In addition, we found that nerve strain increased significantly in conditions in which gliding motion was restricted. Nerve strain due to motion associated with cellular phone use, for example, rose by 69.1%. Conclusions: Elbow flexion and shoulder abduction in daily activities are associated with increases in ulnar nerve strain, but this may not cause permanent damage to the nerve. After nerve gliding motion had been restricted, nerves that normally exhibited less strain often had even increased higher levels of strain than those nerves that normally exhibited high strain.