Severely disabled children suffer from a lot of musculoskeletal deformities. The diseases that cause musculoskeletal deformities are heterogeneous. It includes not only cerebral palsy (CP), but also myopathy, metabolic disease, motor neuron disease, and other various congenital diseases.

The prevalence of scoliosis in patients with spastic CP ranges from 15% to 61%. Hip subluxation and dislocation are the second most common deformities in patients with spastic CP, with a reported prevalence of up to 28%. Associated abnormalities include pelvic obliquity (68%), hip contractures (79%), and femoral head subluxation (59%). The most commonly affected muscles are the paraspinal muscles, hip flexors, hip adductors, hamstrings, gastrocnemius, and soleus [1].

In severely disabled children, scoliosis is one of the most common musculoskeletal deformities and is considerably worse compared to mildly disabled children. Curve progression of 0.8° per year when the largest curve was less than or equal to 50° at skeletal maturity and curve progression of 1.4° per year when the largest curve was greater than 50° at skeletal maturity [2].

As scoliosis shows the gradual increase of the deformed angle, it may induce pain, emotional disorder, pressure sores, cardiopulmonary dysfunction, and other secondary problems [3]. In contrast with idiopathic scoliosis, it has a tendency to progress from a flexible curvature to a permanent deformity because the progression continues even after the end of growth. Particularly, in cases with pelvic obliquity, the prognosis may become worse [4,5]. A large number of severely disabled children use the custom molded fitting chair that is manufactured for their specific body shape, because the premanufactured off-the-shelf component or fabric-based sling seat are not inclined for that purpose. Although disabled children surely need the orthotics for transfer, study, or nursing, they cannot use the ready-made or fabricated orthotics for their deformities. Their deformities are too severe to use the premanufactured or fabric-based type seat. Also, the chair is helpful to reduce the effort of the caregiver allowing the patient to sit comfortably for hours.

The chairs were manufactured in the Technical Aid Center of the Notre Dame Welfare Center. Before manufacturing the chair, the patients visited our hospital and were examined in regards to their disease, lifestyle, and musculoskeletal disabilities. The orthotics that can be manufactured are buggy, postural wheelchair (PW), wheelchair, car seat, chair for study, and so on. After determining which type of orthotics would be made, the inner is manufactured by the molding system. After laying the patient on the simulator, a suitable shape is created. Then, the simulator transmits the plane image of the shape to the computer. Once transmitted, the computer reconstructs the three dimensional image from the plane image, and the technician makes the inner according to the blueprint (Fig. 1). The arm board or headrest is added according to the kinds of orthotics and severity of the disability. The suspending belt for the pelvis or trunk is also attached. After manufacturing the inner, it is installed to the frame of the orthotics such as a wheelchair (Fig. 2).

When manufacturing the chairs, for their comfort, the physiatrist should consider the musculoskeletal deformity of the patients. The rapid growth in adolescents is likely to cause musculoskeletal deformity and several other complications in adulthood [6]. The most common problem is deformities of the spine and hip joint in patients with CP [1]. Scoliosis is defined as a deformity where the spine is deviated laterally or rotated. Cobb's angle is the most popular index to evaluate the severity of scoliosis [7]. Hip dislocation is also common in children with CP. Reimers migration percentage is the index to assess the severity of hip dislocation or subluxation [8]. Coxa valga has appeared in most hip joints of CP, and is evaluated with the femoral neck-shaft angle of the femur. The angle varies with age, stature, and width of the pelvis, being less in adults. When the angle is larger than 135°, condition is known as coxa valga [9].

We followed up the indices of musculoskeletal deformity in severely disabled children to investigate the effectiveness of custom molded fitting through comparison of musculoskeletal indices between pre- and post-chair status, and to determine the correlation between three indices of musculoskeletal deformity.

A custom molded fitting chair is equipment used to aid in the retardation of aggravation of musculoskeletal deformities or unstable body posture caused by brain, spinal, and neuromuscular diseases. Another purpose of the custom molded fitting chair is to provide comfort to patients and lessen the burden of the caregiver. In practical terms, most caregivers get the chair for the comfort and improvement of activities of daily living for their children.

A previous study investigated the effect of the body shape molded inner system on the attenuation of spinal curvature and pelvic obliquity in cerebral palsy with scoliosis [10]. However, there is a limitation in that it only compares the spinal curvature after application of chair immediately. Therefore, a follow-up study of more than 1 year would prove to be more meaningful to know its clinical usefulness.

Not only spinal scoliosis, but hip dislocation is one of the important deformities in patients with CP. Hip dislocation may include seating difficulties, pain, gait deterioration, and problems with perineal hygiene [11]. Miller and Bagg [4] found that the hips of children with CP who were younger than 8 years and had a migration percentage of less than 30% were less likely to progress to dislocation than were the hips of children with a migration percentage of more than 30%. If the migration percentage was greater than 60%, complete dislocation of the hips without surgical intervention was reported [12]. The femoral neck-shaft angle is greater in children with CP than in typically developing children and is more pronounced in children with CP who are at risk for eventual subluxation [13]. It could be confirmed by positive correlation between Reimers migration ratio and femoral neck-shaft angle in this study because Reimers migration ratio indicates the degree of hip dislocation.

Although the femoral neck-shaft angle was improved after application of the chair, spinal scoliosis and hip dislocation was slightly aggravated. However, considering rapid aggravation of deformities with the growth spurt in adolescents, it should be reconsidered if the chair did not affect scoliosis or hip dislocation significantly. The rapid growth in adolescents is likely to cause musculoskeletal deformity, and complications may be accompanied in adulthood. Furthermore, most aggravation from deformity is progressive in the grow spurt period. It is well known that even spinal orthosis for scoliosis is limited to prevent the exacerbation [14,15]. Thus, the physiatrist should consider the aspect of comfort, rather than aggressive correction of deformities. In that sense, the custom molded fitting chair would be a more suitable instrument for severely disabled children for its comfort. Although it is not significant statistically, a slight exacerbation of the deformity might be significant clinically.

The limitation of study is as follows. Without the chair, the deformities might become worse compared to the state with the chair. To confirm this problem, comparing between patients with the chair and without the chair in a controlled study is needed. However, an ethical problem arises in that the patients without the chair may endure discomfort.

The growth spurt is one of the most critical variables that affect numerous musculoskeletal deformities. Progression of scoliosis is greatest during the growth spurt and may continue after skeletal maturity, especially when associated with pelvic obliquity [12]. Therefore, it is important to separate the children with growth spurts. Although this was done, the number of subjects after the growth spurt is too little to acquire significant results. Further investigation should be done with more subjects who experience the growth spurt period.

In our study, it was found that the custom molded fitting chair had the effect of preventing the progression of coxa valga in severely disabled children. In addition, there was no significant aggravation of the Cobb's angle or Reimers migration percentage. However, a considerable number of patients did not show aggravation of deformities. Thus, we can expect the use of the custom molded fitting chair to delay rapid aggravation of musculoskeletal deformity.