Spasticity-correcting surgery in patients with injuries to upper motor neurons include various techniques, including tenotomies and lengthening of tendons of spastic muscles. Early mobilization including active loading of a lengthened tendon is essential to prevent adhesion formation, which necessitates a lengthening technique that resists the forces produced by the involved muscles. This study on animal tendons reports the biomechanical properties in regards to elongation and load to failure in porcine tendons lengthened by either a 3 or 5 cm overlap and tested in a simple force rig. The lengthening technique used in these tendons is described in step-by-step detail. The mean elongation of 20 lengthened tendons at 100 N was 10 mm for tendons with a 3 cm overlap and 6 mm for tendons with a 5 cm overlap. The mean peak load at failure of the construct was 138 N for lenghened tendons with a 3 cm overlap and 201 N for tendons with a 5 cm overlap. The results of this study indicate that a tendon lengthened by the described technique with a mere overlap of three cm will withstand the estimated forces elicited by muscles in the forearm immediately after surgery.
Keywords: Tendon lengthening; biomechanics; flexor tendon; spasticity surgery.