Ultrastructural investigation of the human hand after tendon and motor nerve injury.

Specimens of the affected muscles obtained during reconstructive surgery 4 to 16 weeks after injury of the tendon or of the motor nerve of the human hand were studied. After tenotomy the most serious lesions were displayed by the contractile elements which were homogeneous brittle and atrophied, and disintegrated independently of the functional units. The number of mitochondria decreased, the sarcoplasmic reticulum accumulated and the red and white muscle fibres could not be distinguished. After motor nerve injury the motor end plates were completely destroyed and Wallerian degeneration appeared. The contractile elements atrophied and were brittle. The number of mitochondria and the sarcoplasmic reticulum decreased, the sarcoplasmic glycogen content was higher than normal, and often the cell nuclei occupied a central position.