A New Hip-Action Adjustable-Abduction Orthosis
ARTHUR L. MESSINGER, M.D. CHARLES W. HAVILAND, C.O.A.
The design objective in orthotics is to meet the functional needs of the patient requiring a brace without imposing undesirable restrictions to his motions.
It is frequently difficult to achieve these objectives in the case of children with cerebral palsy (CP) and requires that factors which are unique to the disease - namely, defective voluntary control of muscles and perceptual dysfunction - be considered. In addition, and pertinent to the orthosis design to be described, spasticity of the hip adductor muscles, which interferes with reciprocal leg motion, is a major problem requiring attention by the clinic team.
The common method of bracing the CP child is the bilateral, double-upright,long-leg orthosis or HKAFO (hip-knee ankle-foot orthosis) with a pelvic band. Typically, such orthoses are heavy, burdensome, and motion-restricting. Their principal value is that they provide standing stability.
A 1967 report1 described a bilateral orthosis which controlled the spastic adductors, allowed reciprocal leg motions, and permitted free abduction. These braces provided a wider base of support in kneeling and standing, and, at the same time, provided stability at the hips. The authors understand that this design was introduced at Rancho Los Amigos Hospital in Downey, California, prior to the date of the report referred to above and has been in continuous use there since that time.
In 1971, a new hip-action orthosis was designed by one of the authors to provide additional functions required by certain CP children. It was nicknamed the "Mini-Brace."
The Mini-Brace combines the functions of the hip-abduction splint, and the hip-action brace for walking. Moreover, it incorporates three additional features:
Medial condylar extensions which limit internal leg rotation by applying resistive support to the medial femoral condyles ( Figures 1-A and 1-B ).
A screw to adjust the abduction joint so that it will provide between zero and approximately 30 deg. of abduction as desired ( Figures 2-A and 2-B ).
A plunger lock at the hip level which allows the brace to be locked in full extension for standing or sleeping ( Figure 3 ).
The benefits of these features are doubtless evident to anyone involved in CP orthotics. Experience with about 50 fittings in CP schools in three treatment centers in Santa Clara County, California, has demonstrated that these additional features of the Mini-Brace provide important new benefits.
First, the medial condylar extensions prevent progressive inward femoral rotation which can occur when a hip-action walking brace with conventional cuff attachments is used. The prevention of such rotation is profoundly important to the future gait pattern of the developing child with CP.
Second, the abduction angle-screw-adjustment feature provides a built-in orthosis "modification" capability which simplifies adjustment. It also permits the orthosis to be set in "neutral abduction" to provide stability for CP patients whose stability is impaired because of abductor surgery or neurectomies.
Third, the plunger lock of the hip joint can be manually or automatically engaged with the orthosis in the fully extended position. Thus, the device can, be locked during sleep as a corrective measure. The lock can also be engaged to provide stability during standing. When not engaged, hip-flexion and extension motions are virtually free. Reciprocal crawling or walking is aided by the Mini-Brace. Sitting and standing positions are achieved with a minimum of interference from the orthosis.
A major children's hospital carried out electromyographic analyses of the activity of the rectus femoris, vastus medialis, and medial hamstrings during ambulation of one eight-year-old CP child wearing the Mini-Brace. A summary of the results stated that "The braces made, or allowed her to have, more phasic muscle activity and a more normal foot placement sequence."
The Mini-Brace component kit* includes a pelvic band which the orthotist must fit carefully into the region between the crests and the anterosuperior spines of the ileum. This careful pelvic-band fitting presumes that the prime use of the orthosis will be with the hip joint locked in the full-extension position. As presently supplied, the pelvic band is made of aluminum. However, it is possible to make a molded-plastic pelvic band if this type of support is desired. The form of the condylar support elements supplied in the Mini-Brace component kit is such that they can be moved easily or their shape modified.
The Mini-Brace can also be incorporated in long-leg braces (HKAFOs), if certain fitting adjustments are made.
CP children can now be provided with a lower-limb orthosis which meets most functional requirements and does not impose undesired restrictions on the patients. The finished orthosis provides support at the hip, permits reciprocal movements by controlling abductor motion patterns, and allows abduction adjustment from a fixed neutral position to any angle up to 30 deg. maximum, beyond which free abduction is still possible. In addition, internal leg rotation can be prevented or corrected by the use of femoral condyle supports which are a part of the orthosis design. A plunger lock at the hip joint permits the joint to be immobilized in full extension during standing or sleeping. Walking, crawling, sitting, and standing are aided. The brace has been used in about 50 cases over a two-year period with good results.
1. Guess, V. S., Control dysfunction bracing in cerebral palsy. Phys. Ther., September 1967.