SPINAL FUSION IN DUCHENNE MUSCULAR DYSTROPHY
Spinal deformity is a significant problem for patients in the final stages of Duchenne muscular dystrophy (Robin and Brief 1971; Gibson and Wilkins 1975; Gibson et al. 1975, 1978; Wilkins and Gibson 1976; Hsu 1983; Kurz el al. 1983). Because of the kyphoscoliosis, most patients traditionally have spent the last 10 years of their lives in bed, unable to sit or able to sit for only short periods (Gibson et al. 1975, 1978). Attempts to brace the spines of these patients have proved unsuccessful because of deterioration of pulmonary function and the patients' inability to move to relieve pressure areas in the orthosis. Since the 1970s, Donald Gibson has been involved with the orthopaedic care of the patients with muscular dystrophy at the Hospital for Sick Children in Toronto, and under his direction attempts have been made to define the scoliotic deformity and to understand the mechanism of curve progression to try to prevent it (Gibson and Wilkins 1975; Gibson et al. 1975, 1978; Wilkins and Gibson 1976; Weiman et al. 1983). Attempts to use orthoses to prevent the early lordoscoliosis from progressing to kyphoscoliosis have failed (Smith et al. 1989). There have been reports on instrumentation for patients with Duchenne muscular dystrophy (Weiman et al. 1983, Cambridge and Drennan 1987, Smith et
al. 1989), but complications and longterm benefits are still uncertain. This report will address these two issues, as well as the indications for instrumentation for patients with Duchenne muscular dystrophy.
Material and method The Muscular Dystrophy Clinic at the Hospital for Sick Children, Toronto, had 183 patients with Duchenne muscular, dystrophy with sufficient follow-up data to evaluate the progression of their spinal deformities. Of these, 87 were followed until their death. All diagnostic data, genetic information, orthotic prescriptions, spinal radiographs and pulmonary function data were maintained on a computer data-base. All measurements of height used to determine growth and to calculate normalized pulmonary function data were made from three-dimensional computer reconstructions of spine length (Koreska et al. 1978). The radiographs were obtained while patients sat on a specially designed seat that allows them to sit in a position similar to their usual seating posture. The seat is on castors so that it can be turned to obtain both anteroposterior and lateral views, without repositioning the patient (Fig. 1). The radiographs were digitized and a computer was used to reconstruct a three-dimensional configuration of the
'.
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'A
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Fig. I. This seating device allows reproducible upright spine radiographs to be taken without holding the patient. Device is on castors so that both anteroposterior and lateral projections can be made without changing patient 's position.
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776
spine (Koreska et al. 1978, Koreska and Smith 1982). A graph chart was used to compare the results from the patient's previous examinations to determine progression of deformity and growth.:The patient's height was calculated from a known constant relationship between the length of the thoracolumbar spine and standing height (Miller et al. 1992). The 482 pulmonary function tests for 147 patients were done at the pulmonary function laboratory at the Hospital for Sick Children. In order to ascertain the problems of late-stage muscular dystrophy, patients or their principal caretakers were interviewed by a registered nurse who was experienced in dealing with patients with muscular dystrophy. The patients had been diagnosed by a neurologist, using acknowledged criteria. Care was taken to include only patients with classic Duchenne muscular dystrophy and to exclude related diseases such as Becker dystrophy, limb-girdle dystrophy and spinal muscular atrophy.
Indications for spinal fusion The patient's stage of growth should be taken into account when considering surgery. For example a 10-year-old boy who is still very short, has 60 per cent of normal forced vital capacity (FVC) and a scoliotic curve of 30" may have his surgery delayed for one year if he is very concerned about height. Scoliosis in the early stages is very flexible; even if the curve reached 50", it would still be completely correctable. It is also
important to have a radiographic seating device that allows reproducibility of position, otherwise it is very difficult to determine the degree of scoliosis. In 91 per cent of the patients, the scoliosis reached 30" before the percentage of normal FVC dropped to 35; the scoliosis always progressed in this group. In the remaining 9 per cent of patients with less than 35 per cent normal FVC and a scoliotic curve of
Spinal deformity is a significant problem for patients in the final stages of Duchenne muscular dystrophy (Robin and Brief 1971; Gibson and Wilkins 1975; Gibson et al. 1975, 1978; Wilkins and Gibson 1976; Hsu 1983; Kurz el al. 1983). Because of the kyphoscoliosis, most patients traditionally have spent the last 10 years of their lives in bed, unable to sit or able to sit for only short periods (Gibson et al. 1975, 1978). Attempts to brace the spines of these patients have proved unsuccessful because of deterioration of pulmonary function and the patients' inability to move to relieve pressure areas in the orthosis. Since the 1970s, Donald Gibson has been involved with the orthopaedic care of the patients with muscular dystrophy at the Hospital for Sick Children in Toronto, and under his direction attempts have been made to define the scoliotic deformity and to understand the mechanism of curve progression to try to prevent it (Gibson and Wilkins 1975; Gibson et al. 1975, 1978; Wilkins and Gibson 1976; Weiman et al. 1983). Attempts to use orthoses to prevent the early lordoscoliosis from progressing to kyphoscoliosis have failed (Smith et al. 1989). There have been reports on instrumentation for patients with Duchenne muscular dystrophy (Weiman et al. 1983, Cambridge and Drennan 1987, Smith et
al. 1989), but complications and longterm benefits are still uncertain. This report will address these two issues, as well as the indications for instrumentation for patients with Duchenne muscular dystrophy.
Material and method The Muscular Dystrophy Clinic at the Hospital for Sick Children, Toronto, had 183 patients with Duchenne muscular, dystrophy with sufficient follow-up data to evaluate the progression of their spinal deformities. Of these, 87 were followed until their death. All diagnostic data, genetic information, orthotic prescriptions, spinal radiographs and pulmonary function data were maintained on a computer data-base. All measurements of height used to determine growth and to calculate normalized pulmonary function data were made from three-dimensional computer reconstructions of spine length (Koreska et al. 1978). The radiographs were obtained while patients sat on a specially designed seat that allows them to sit in a position similar to their usual seating posture. The seat is on castors so that it can be turned to obtain both anteroposterior and lateral views, without repositioning the patient (Fig. 1). The radiographs were digitized and a computer was used to reconstruct a three-dimensional configuration of the
'.
f I
'A
r-
p'
'D
8
775
Fig. I. This seating device allows reproducible upright spine radiographs to be taken without holding the patient. Device is on castors so that both anteroposterior and lateral projections can be made without changing patient 's position.
.-C C
.-0 r2 v)
m
.P VY
776
spine (Koreska et al. 1978, Koreska and Smith 1982). A graph chart was used to compare the results from the patient's previous examinations to determine progression of deformity and growth.:The patient's height was calculated from a known constant relationship between the length of the thoracolumbar spine and standing height (Miller et al. 1992). The 482 pulmonary function tests for 147 patients were done at the pulmonary function laboratory at the Hospital for Sick Children. In order to ascertain the problems of late-stage muscular dystrophy, patients or their principal caretakers were interviewed by a registered nurse who was experienced in dealing with patients with muscular dystrophy. The patients had been diagnosed by a neurologist, using acknowledged criteria. Care was taken to include only patients with classic Duchenne muscular dystrophy and to exclude related diseases such as Becker dystrophy, limb-girdle dystrophy and spinal muscular atrophy.
Indications for spinal fusion The patient's stage of growth should be taken into account when considering surgery. For example a 10-year-old boy who is still very short, has 60 per cent of normal forced vital capacity (FVC) and a scoliotic curve of 30" may have his surgery delayed for one year if he is very concerned about height. Scoliosis in the early stages is very flexible; even if the curve reached 50", it would still be completely correctable. It is also
important to have a radiographic seating device that allows reproducibility of position, otherwise it is very difficult to determine the degree of scoliosis. In 91 per cent of the patients, the scoliosis reached 30" before the percentage of normal FVC dropped to 35; the scoliosis always progressed in this group. In the remaining 9 per cent of patients with less than 35 per cent normal FVC and a scoliotic curve of
