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Reciprocating Gait Orthosis with Linear Bearing

To be able to walk is an important objective for many children who are paraplegic. The achievement of this goal depends on many factors, such as the cause of their paraplegia, the level of the lesion of the spinal cord, the strength of the upper limbs, the patient's coordination and motivation, and the quality of orthotic management.

Principles of orthotic management for these children demand that both the improvement of function and the prevention of deformity are viewed simultaneously. The skeleton is molded by muscular and gravitational forces in childhood when bony tissue is more malleable and the epiphyseal plates are not ossified; bone and joint deformation can develop if these forces are abnormal. Orthotic stabilization of the spine and of the lower limbs may be required to decrease skeletal changes resulting from neuromuscular dysfunction. Any orthosis should, in some way, correlate to the degree of neuromuscular dysfunction; in other words, the child with the high lumbar lesion does not warrant or need as much stabilization or mechanical assistance as the child with a thoracic lesion. To achieve ambulation is an important component of treatment; however, it cannot be viewed as the sole component. This philosophy of management underlies the development of the reciprocating gait orthosis with linear bearing.

Reciprocating Gait Orthosis

The Louisiana State University Reciprocating Gait Orthosis (RGO) has proven to be a successful form of orthotic management for many children and adults who are paralysed. Roy Douglas, Wallace Motloch, and Carlton Fillauer1 have made significant contributions to make the orthosis available and the preferred mode of treatment for such patients.

The RGO with linear bearing (Fig. 1 ) is an attempt to improve the mechanical and clinical efficiency of the basic design and has been used clinically by patients with spina bifida with myelodysplasia, neuroblastoma, and muscular dystrophy. The original system is designed so that flexion of one leg results in extension of the other. This is achieved by coupling the hip joints with two Bowden cables. Friction in the cables warrants improvement. The Bowdenflex push pull mechanical remote control was designed by Bowden to overcome the friction problem for marine and aeronautical engineering applications.2 The push pull linear bearing is a highly efficient means of joining the hip joints to transmit forces that assist reciprocal walking. Joining the hips also prevents simultaneous hip flexion, thus ensuring an upright posture or gradual stretching of hip flexion contractures, if warranted. Alignment capability is attained by passing the bearing through an "alignaball" or eye bolt which also serves as an attachment to the pelvic or spinal component (Fig. 2 ).

The Bowdenflex push pull mechanical remote control is essentially a linear ball bearing enclosed in a flexible outer casing (Fig. 3 ). The input load is transmitted by means of a center rail which is grooved on both faces to provide races for the two rows of ball bearings. This is a mechanical component for the transmission of linear motion from one remote point to another, and achieves this at a load efficiency greater than 80 percent with a travel efficiency greater than 94 percent; both figures are significantly higher than standard Bowden cable as utilized in the current RGO design. The Bowdenflex push pull linear bearing is available from Bowden Controls Limited, Llanelli, Dyfed, Great Britain.

Spinal Deformity

The associated problem of spinal deformity in the paraplegic child should be a major factor when considering any form of orthosis.3,4 Incidence of severe thoraco-lumbar scoliosis is high, particularly among children who have a thoracic lesion. A hip knee ankle foot orthosis should have the capability of managing present or potential scoliosis. For example, scoliosis increased during a 10 month period in an 8year-old girl with a low thoracic lesion (Figs. 4 -5 ). During this period, she ambulated daily and efficiently in a standard RGO despite the fact that her spine was deteriorating rapidly. It is not possible, therefore, to understate the importance of the proximal component of the orthosis which needs to be determined by the presence or likelihood of spinal deformity. Scoliosis is influenced by many factors, including the level of lesion and the skeletal maturity of the patient. A pelvic band may be appropriate for one child, while another requires a thoracolumbosacral orthosis.

A one-year clinical study at the Department of Orthotics and Prosthetics, Cleveland Clinic Foundation, involved 20 children fitted with the RGO. They ranged from 19 months to 13 years in age, averaging 9.5 years old. The average lesion level was T 9, with a range from T 4 to L3. Spinal deformity was present in 63 percent of the participants.

The Bowdenflex push pull linear bearing is an improved method of linking orthotic hip joints to provide reciprocal walking for paraplegic children. Correlation between improved mechanical efficiency of the orthosis and reduction of energy expenditure has yet to be established. The relationship between pediatric paraplegia and severe spinal deformity is apparent and, at the very least, warrants closer scrutiny when prescribing or fitting any design of RGO. Half of the children involved in the Cleveland study were existing RGO users; therefore, it was possible to assess function and evaluate radiographically improvement in spinal alignment. As expected, the quality of gait and function related directly to neuromuscular dysfunction.

Acknowledgments

The Reciprocating Gait Orthosis with Linear Bearing was developed at the University of Strathclyde, Glasgow, Scotland. The author acknowledges the significant contribution made by George Ballantyne.

Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada

References:

  1. Durr Fillauer Medical Inc., Post Office Box 1678, Chattanooga, TN 37401.
  2. Bowdenflex Control Marine Manual. Bowden Controls Limited, Llanelli, Dyfed, Great Britain.
  3. Molnar GE: "Orthotic Management of Children," in Orthotics Etcetera, 3rd Edition, JB Redford, Ed. Baltimore: Williams & Wilkins, 1986. Pp. 352-387.
  4. Rose GK, Sankarankutty M, Stallard J: "A Clinical Review of the Orthotic Treatment of Myelomeningocele Patients. Journal of Bone and Joint Surgery 65-B:242246, 1983.