[New concepts in reconstruction of arm and hand function in tetraplegia--basic research and clinical application].

Reconstructive hand surgery improves the ability to meet the needs of daily life and the independence of patients who have lost their upper extremity function due to cervical spinal cord injury. Tendon transfer procedures provide the potential to restore key functions, such as elbow and wrist extension or hand grip control, ameliorate joint balance, reduce pain in spasticity and prevent joint contractures. The choice of the optimal donor muscle should be based on a thorough understanding of the biomechanical principles of the muscle-tendon unit. Intraoperative sarcomere length measurements allow to predict and set the optimal muscle-tendon unit length during reconstructive upper extremity surgery in order to prevent overstretch which may lead to insufficient active force generation. Macro-proteins and the extracellular matrix are in charge of the muscle ultrastructure, elasticity and thus passive muscle tension. Spastic muscles are characterized by greater stiffness, a shorter sarcomere length and an extracellular matrix with inferior mechanical properties. Basic science research and clinical studies in cooperation with international centers are of great importance to promote the development of refined techniques of surgical reconstruction and postoperative rehabilitation of upper extremity function in tetraplegic patients.