The mechanical changes of finger tendons under use of dynamic orthosis / 中华物理医学与康复杂志

ABSTRACT

Objective To study the mechanical changes of extensor and flexor tendons during use of dynamic orthosis after repair operation on the flexor tendons of hand.Methods An experiment model was established in eight groups (at different stages) using eight descarded fresh and integral human fingers which were broken from the distal plane to the proximal plane of metacarpal bone,thereby while using a dynamic orthosis the extension and flexion movement of extensor and flexor tendons of fingers were induced.An initial tensile force (F) of 0.2 N ～ 0.5 N was exerted on the flexor tendons of each group to simulate the extension and flexion movement of the muscle and a tensometer was connected to the extensor tendon exerting a tensile force (F2) and pulling the finger to the proximal interphalangeal joint at various positions of 20° ～ 50°,thus the tensile force (Fx) of flexor tendons and the tensile force (F2) of extensor tendons were measured.A rubber band was fixed at the distal end of the finger nails to simulate the dynamic orthosis and was pulled toward the proximal-end of the finger,while exerting an initial traction force (F1) of 0.1 N ～ 0.4 N and pull the extensor tendons with the tensometer to cause the finger extension until they reach the same position as that before the simulated dynamic orthosis was employed.Then the tensile force (Fx') of flexor tendons of each group as well as the tensile force (F2') of extensor tendons were measured,after which a statistical comparison was made with regard to the tensile force Fx and Fx' of flexor tendons and the tensile force F2 and F2' of extensor tendons before and after the simulated dynamic orthosis was employed.Results The tensile force (Fx') of flexor tendons during the simulated orthosis was used was compared with the tensile force (Fx) during the simulated orthosis was not used,it showed no statistical significant (P ＞ 0.05) ; in the meantime,by comparing the tensile force F2' and F2 of extensor tendons,it was found that the difference statistically significant (P ＜ 0.001) ; after the orthosis was used the tensile force of extensor tendons F2' increased remarkably with the increase of the initial tensile force F1 during the dynamic orthosis of rubber band was used.Conclusion The tensile force of flexor tendons would not be changed during a dynamic orthosis was used after repair operation on the flexor tendon of hand;however,with the increase of extensor tensile force,the resistance of finger extension would be multiplied and cause more difficulty to do exercise.