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During grasping, the median nerve undergoes mechanical stress in the carpal tunnel which may contribute to carpal tunnel syndrome. This study investigated the effects of wrist posture, grip type, and grip force on the shape and cross-sectional area of the median nerve. Ultrasound examination was used to obtain cross-sectional images of the dominant wrist of 16 healthy subjects (8 male) at the proximal carpal tunnel during grasping. The cross-sectional area, circularity, and axis lengths of the median nerve were assessed in 27 different conditions (3 postures × 3 grip types × 3 force levels). There were no significant changes in median nerve cross-sectional area (P > 0.05). There were significant interactions across posture, grip type, and grip force affecting nerve circularity and axis lengths. When the wrist was flexed, increasing grip force caused the median nerve to shorten in the mediolateral direction and lengthen in the anteroposterior direction (P < 0.04), becoming more circular. These effects were significant during four finger pinch grip and chuck grip (P < 0.05) but not key grip (P > 0.07). With the wrist extended, the nerve became more flattened (less circular) as grip force increased during four finger pinch grip and chuck grip (P < 0.04) but not key grip (P > 0.3). Circularity was lower during the four finger pinch compared to chuck or key grip (P < 0.03). The findings suggest that grip type and wrist posture significantly alter the shape of the median nerve. Clin. Anat. 30:470-478, 2017. © 2017 Wiley Periodicals, Inc.

Subpectoral implants for breast reconstruction after mastectomy requires the surgical disinsertion of the sternocostal fiber region of the pectoralis major. This technique is associated with significant shoulder strength and range of motion deficits, but it is unknown how it affects the underlying integrity of the shoulder joint or pectoralis major. The aim of this study was to characterize the long-term effects of this reconstruction approach on shoulder joint stiffness and pectoralis major material properties. Robot-assisted measures of shoulder strength and stiffness and ultrasound shear wave elastography images from the pectoralis major were acquired from 14 women an average of 549 days (range: 313-795 days) post reconstruction and 14 healthy, age-matched controls. Subpectoral implant patients were significantly weaker in shoulder adduction (p < 0.001) and exhibited lower shoulder stiffness when producing submaximal adduction torques (p ¼ 0.004). The underlying material properties of the clavicular fiber region of the pectoralis major were altered in subpectoral implant patients, with significantly reduced shear wave velocities in the clavicular fiber region of the pectoralis major when generating adduction torques (p ¼ 0.023). The clinical significance of these findings are that subpectoral implant patients do not fully recover shoulder strength or stability in the long-term, despite significant recovery time, and substantial shoulder musculature left intact. The impact of these procedures extends to the remaining, intact volume of the pectoralis major. Optimization of shoulder function should be a key aspect of the post-reconstruction standard of care. ß

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