Orthosis for children with congenital tibia pseudarthrosis II

Second, Design of Orthosis

1) Design Ideas

MEDI-REHATEK Orthosis is designed for compensating unequal length of lower extremities,maintaining pelvis in the horizontal plane and avoiding the occurrence of spinal scoliosis; pseudarthrosis bears free of load and is protected ; realizing walking function.

The pseudarthrosis in the proximal tibia.The fabrication of orthosis of free-load on shank and patellar tendon bearing load,which has a small stress area with greater pressure in part that would exceed the tolerance of the skin. We will design an orthosis with free load on ischial tuberosity and soft tissue of thigh according to the specific circumstance (Fig. 2), although the orthosis has more weight than orthosis of free-load on shank and patellar tendon bearing load, it greatly improves the stress condition as well as offers significantly more comfort.

Taking into account that soft tissues of thigh change as age increases, we use opening type at the front of plastic plate with the fasteners in order to adjust the tightness;Orthosis has bilateral metal bars which increases its intensity. It also has a locking device of mechanical knee joint so that knee joint is stabilized when standing and the joint can be opened and bent down naturally when sitting down; There is a shank protection part put on the proximal leg protection for increasing the protection for lesion;The height can be adjustable between knee joint and stirrup as the growth of patient’s height.

2) Material Selection

Polyethylene plate on thigh part is suitable for the skin, which increases comfort and stability; bilateral bars and joint are made of metal that increase the intensity; The bottom of orthosis is connected with metal stirrup under which has rubber in order to increase the comfort level and the slip coefficient during walking.

3)Fabrication Process

The first step: Take the plaster cast from patient(guarantee of wearing comfort); The second step: modification of the positive plaster cast; The third step: the high temperature polyethylene sheet needs heating to be transparent and spreading on the surface of positive plaster cast.Then  get a vacuum molding; The forth step: cut the ideal shape of orthosis and edge polishing after the material is cooled; The fifth step: installation of metal bars, joints, stirrup, and determine the height of the orthosis according to the length of patient’s limb; The sixth step:The patient tries to wear the sample; The seventh step: install velcro straps and complete.

Relative blog:The Application of Spinal Orthosis I