Subjects
The study population consisted of 144 boys who had an established diagnosis of Duchenne muscular dystrophy and who had been followed at our facility for at least one year between 1953 and 1994. The diagnosis of Duchenne muscular dystrophy was based on a clinical history of an onset of weakness by the age of five years, progressive weakness of the proximal muscles, increased levels of serum creatine kinase that were at least ten times the upper limit of normal, and findings consistent with Duchenne muscular dystrophy on muscle biopsy5. Thirty-five boys had a brother or a first-degree relative who had Duchenne muscular dystrophy.
Collection of Data
Data were compiled from the medical records of each patient as well as from a flow sheet31 that was developed at our center and has been used routinely since 1953. This form was completed by a physician at the Muscle Disease Center in order to document the functional abilities of the patient and the range of motion of the lower extremities at each follow-up visit. Function of the lower extremities was measured with use of timed tests of walking and stair-climbing as well as with an assessment of the ability to perform daily activities36. Function then was rated on the basis of these measurements35. The functional classifications ranged from 1, which indicated that the patient could walk and climb stairs without assistance, to 9, which indicated that the patient was confined to a wheelchair or bed. The passive ranges of motion of the ankle, knee, and elbow were assessed according to the technique of The American Academy of Orthopaedic Surgeons3. Intratester and intertester reliability of goniometric measurements of dorsiflexion of the ankle as well as extension of the knee and elbow for patients who have Duchenne muscular dystrophy have been reported to be acceptable, with intraclass correlation coefficients ranging from 0.90 to 0.94 and 0.58 to 0.91, respectively21. Measurements of weight, height, and vital capacity were recorded at each follow-up evaluation, and creatine and creatinine ratios, the level of creatine kinase, and muscle strength were determined once a year.
Analysis of Data
The patients were divided into three groups. Group 1 consisted of twenty-eight patients who had not been managed with bracing or an operation to prolong the ability to walk. Some of these patients had not had bracing or an operation because the family had refused such measures. Others had not been considered by the staff at the center to be good candidates for either bracing or operative intervention because of mental retardation, poor motivation of the patient or the family, or non-compliance with previously prescribed programs of physical therapy. This group also included patients who had become permanently confined to a wheelchair by the time that they were first seen at the center. Group 2 consisted of seventeen patients who had been managed with knee-ankle-foot orthoses but whose family had declined operative intervention or who had only slight heel-cord contractures. Group 3 comprised ninety-nine patients who had had operative intervention followed by the application of knee-ankle-foot orthoses for walking. This group was additionally divided into two subgroups to examine the outcomes of two different operative procedures. Group 3-A consisted of twenty-six patients who had had tenotomy of the Achilles tendon with use of a closed method and release of the iliotibial bands with a Yount distal fasciotomy. Group 3-B included seventy-three patients who had had these procedures as well as posterior tibial-tendon transfer29 in which the tendon was moved through the interosseous membrane and was inserted on the third cuneiform bone. This tendon-transfer procedure removes the deforming effect of the strong posterior tibial muscle and increases dorsiflexion strength of the foot29.
Three separate analyses were done. First, the data on all 144 boys were used to analyze the demographics of the patient population, changes in the functional class of the lower extremities, and the age at which the patient lost the ability to climb stairs. Second, the occurrence and progression of contractures were analyzed for the ninety-three patients who had attended the center for at least two years after bracing or permanent confinement to a wheelchair. Third, the ability to walk after bracing was examined for eighty-one patients who had been seen at the center for a minimum of one year before bracing and at least two years after bracing.
The patients who were managed with bracing wore metal or, more recently, plastic knee-ankle-foot orthoses. The same criteria for bracing were used for all patients31. Bracing or an operation and bracing was initiated when a physician at the center observed, during a follow-up evaluation, that the child needed to touch the wall or furniture or to seek assistance from another person in order to maintain balance while walking. That point in time was recorded as the end of the ability to walk independently without braces.
The quality of walking was assessed both before and after bracing, by measuring the length of time that a patient was able to walk and the time that was needed to walk a seven-meter course.
The goal of treatment was to enable the patient to walk independently for short distances indoors. With this limited goal in mind, the patients were classified, according to a modification of the system of Ziter and Allsop38, as ambulators, borderline ambulators, or ambulation failures. Ambulators were able to walk the seven-meter course independently in sixty-nine seconds or less. Borderline ambulators were able to walk only a portion of the seven-meter course, needed more than sixty-nine seconds to walk the total distance, or needed assistance to walk. Ambulation failures were not able to walk and needed a wheelchair for mobility but were able to stand while wearing the orthoses.
Descriptive statistics were calculated for all of the variables. Non-parametric statistics were used to analyze the results of treatment.
Demographics and Functional Status
The mean age (and standard deviation) of the patients when they were first seen at the center was 7.5 ± 2.6 years (range, 2.3 to 15.8 years). Sixty-three patients (44 per cent) were first seen before the age of seven years (Fig. 1-A). Ninety-two patients (64 per cent) had mild functional impairment (functional class 1 or 2) at the first visit (Fig. 1-B).
The duration of regular, long-term, serial follow-up of the patients in the present study was extensive (mean, 8.9 ± 4.8 years; range, 1.2 to 25.6 years). One hundred and six patients (74 per cent) were followed for five years or more and sixty-three (44 per cent), for ten years or more (Fig. 1-C). The mean age of the patients at the latest follow-up examination was 16.3 ± 4.8 years (range, 6.7 to 31.7 years).
All of the patients were scheduled to have follow-up examinations at the center at regular three-month intervals. Seventy-nine patients (55 per cent) had had four follow-up examinations at the center each year, and 118 (82 per cent) had had a mean of at least three examinations per year.
The interval between the loss of the ability to climb stairs and bracing varied widely (Fig. 2). The patients lost the ability to climb stairs at a mean age of 9.3 ± 1.4 years (range, 5.8 to 13.8 years). One-half of the 104 patients who were managed with bracing and for whom the information was available had lost the ability to climb stairs within six months before bracing and the other half, seven to forty-two months before bracing. With the numbers available, we could not detect a significant difference in the interval between the loss of the ability to climb stairs and the application of braces among Groups 2, 3-A, and 3-B.
Loss of the ability to walk independently was noted when a patient was observed, by a physician at the clinic, to need support from a wall, furniture, or another person in order to walk. Two patients lost the ability to walk by the age of six years; five, by the age of seven years; twenty, by the age of eight years; twenty-six, by the age of nine years; thirty, by the age of ten years; twenty, by the age of eleven years; ten, by the age of twelve years; and three, by the age of thirteen years. The mean age at which the ability was lost was 10 ± 1.5 years. At that time, an operation or bracing, or both, was recommended to most patients in order to allow them to continue to walk.
Eighty-three patients died; the cause of death was pulmonary insufficiency for fifty-one patients (61 per cent), pneumonia for twenty-six (31 per cent), and cardiomyopathy for six (7 per cent). Seventy-eight (94 per cent) of the eighty-three patients had had a functional classification of 9 at the time of death (Fig. 1-D). A cohort approach was used to study the age at death during successive time-periods: the mean age at the time of death was 18.1 ± 3.2 years (range, 11.8 to 24.6 years) during the 1960's, 19.0 ± 2.8 years (range, 13.7 to 27.5 years) during the 1970's, and 18.8 ± 3.4 years (range, 13.1 to 26.4 years) during the 1980's. With the numbers available, we could not detect a significant difference among the treatment groups or time-periods with regard to the age at the time of death.
Eight patients were still alive and were more than nineteen years old at the time of writing. Five of these men, who were between thirty-one and thirty-three years old, needed ventilator support.
Occurrence and Progression of Contractures
The development of contractures was analyzed for ninety-three patients who had been followed for a mean of 11 ± 4.0 years (range, 2.75 to 22.4 years). The results in the three groups that had had intervention (Groups 2, 3-A, and 3-B) and those in the group that had not (Group 1) were compared in order to assess the relative effects of a comprehensive program of physical therapy and bracing with those of physical therapy, bracing, and an operation on the subsequent development of contractures of the lower extremities. With the numbers available, we could not detect a significant difference between the ages of the patients in the different study groups at the various times of data collection.
Bracing alone, without tenotomy of the heel cord, was prescribed for twelve patients. At the time that the braces were applied, these patients had slight contracture of the heel cords (mean and standard deviation, 1.5 ± 2.8 degrees; range, 0 to 8 degrees).
Sixty-nine patients had an operation (tenotomy of the Achilles tendon either alone or in conjunction with posterior tibial-tendon transfer) in addition to bracing. All seventeen patients who had had tenotomy alone had successful correction of the contracture of the heel cord and were noted to have approximately 10 degrees of passive dorsiflexion of the foot postoperatively29. Fifty (96 per cent) of the fifty-two patients who had had both tenotomy and posterior tibial-tendon transfer were able to dorsiflex the foot actively against gravity after the operation.
Two years after bracing, the patients in Groups 2, 3-A, and 3-B had good alignment at the ankle joint (Fig. 3-A). The patients who had had an operation (Groups 3-A and 3-B) had a mean contracture of 2 ± 4.7 degrees (range, 0 to 15 degrees) compared with 8 ± 13.1 degrees (range, 0 to 30 degrees) for the patients who had had bracing only (Group 2). With the numbers available, we could not detect a significant difference, with regard to the severity of contracture of the heel cord, between the groups that had had an operation and the group that had had bracing only.
Five to seven years after bracing, at the latest evaluation, the contractures of the heel cord were well controlled in both Group 3-A (the patients who had had tenotomy) and Group 3-B (the patients who had had tenotomy and posterior tibial-tendon transfer) (Fig. 4-A). The contractures were significantly less severe in both of those groups than in Group 2 (the patients who had had bracing only) (p = 0.003). Group 3-B had the best results; twenty-eight (88 per cent) of the thirty-two patients in that group had a contracture of less than 5 degrees. Severe contractures of the heel cord (mean, 45 ± 19.1 degrees; range, 33 to 70 degrees) had developed in Group 1 (the patients who had had neither bracing nor an operation) (Fig. 4-A).
Five to seven years after bracing, contracture of the knee continued to be fairly well controlled in most of the patients in Groups 2, 3-A, and 3-B (Fig. 3-B). The patients in Groups 3-A and 3-B had the best alignment, with a mean flexion contracture of approximately 14 ± 19.5 degrees (range, 0 to 60 degrees). The mean flexion contracture of the knee in Group 2 was slightly worse; it measured 19 ± 19.2 degrees (range, 0 to 60 degrees). The mean flexion contracture of the knee in Group 1 measured 49 ± 15.4 degrees (range, 10 to 90 degrees) at the time of the most recent follow-up examination (Fig. 4-B).
Flexion contractures of the elbow were poorly controlled in all groups. Such contractures began at approximately the time that the ability to walk was lost, and their severity increased in a linear fashion (Fig. 3-C).
Ability to Walk
Eighty-one patients were studied in order to analyze the effect of the different approaches of treatment on the duration of both independent and assisted walking. At the time of intervention, the mean age was 10.5 ± 1.3 years (range, 7.3 to 12.3 years) in Group 3-A, 9.8 ± 1.5 years (range, 6.0 to 13.5 years) in Group 3-B, and 10.7 ± 1.7 years (range, 7.8 to 12.8 years) in Group 2. With the numbers available, we could not detect a significant difference among the groups with regard to the age at the time of intervention.
The mean percentage excretion of urinary creatinine was used as a reflection of over-all muscle mass36. With the numbers available, we could not detect a significant difference among the groups, either at one year before bracing or at the time of bracing (Table I). This finding suggests that total muscle strength was comparable among the various groups at these times.
The mean duration of independent and assisted walking after bracing in Groups 2, 3-A, and 3-B was 3.2 ± 1.5 years (range, zero to 7.5 years). After the patients had lost the ability to walk, they retained the ability to stand with use of braces for a mean of 1.5 ± 1.2 years (range, 0.17 to 5.92 years). With the numbers available, we could not detect a significant difference among these three groups with regard to the duration of the ability to walk or to stand after bracing.
A determination of the ability and the time needed to walk a specified distance is important in the assessment of the over-all benefits of bracing for patients who have Duchenne muscular dystrophy. The time needed to walk the standard seven-meter course improved during the ten months after bracing for the patients who had had both an operation and bracing. In contrast, the patients who had had bracing alone generally needed increasingly longer times to walk the standard course (Fig. 5).
Forty-eight (68 per cent) of seventy-one patients were classified as ambulators approximately one year after bracing (Table II). Approximately two years after bracing, twenty-six (52 per cent) of fifty patients in Group 3-B were able to walk short distances indoors compared with ten (38 per cent) of twenty-six patients in Groups 2 and 3-A.
The results of the present study document the value of established operative methods and bracing for controlling contractures of the lower extremities in patients who have Duchenne muscular dystrophy and for prolonging their ability to walk. The data are useful for comparing the treatment outcomes as well as the cost-effectiveness of traditional operative procedures followed by bracing when the ability to walk independently has been lost with those of the newer and more extensive strategies of early operative treatment4,17,25.
The course of Duchenne muscular dystrophy has been documented in previous reports, with follow-up periods of two to eleven years2,6,7,16,18,27,35,37,39. The most comprehensive study that we know of included 283 boys from four centers who had been followed for a mean of 3.6 years6. The present study had the benefits of a large database from a single center and a long duration of follow-up (mean and standard deviation, 8.9 ± 4.8 years; range, 1.2 to 25.6 years). Nearly one-half of our 144 patients were followed for ten years or more, which afforded us the opportunity to analyze the long-term results of our comprehensive program of rehabilitation.
The importance of controlling contractures of the lower extremities has been demonstrated both at our center and at other facilities6,8,12,26. Control of these contractures, despite advancing weakness of the muscles, allows the patient who has Duchenne muscular dystrophy to retain the ability to walk before and after bracing1. Bracing enables the patient to walk about the house or school without calling for assistance or needing a wheelchair, and the need for continual attention at home or school is reduced. The patient can again play some games, go to the blackboard, change classes, and walk to places that are inaccessible by a wheelchair. Weight control is less of a problem for those who remain active.
The severe contractures associated with Duchenne muscular dystrophy, which involve all weight-bearing joints, not only are disfiguring but also create practical problems. Contracture of the ankle often makes it impossible for the patient to wear normal shoes. Positioning of the patient for sleep is difficult when there are marked contractures of the knees and hips31.
Patients and families report that the time needed for exercises to control contractures is worth the effort because of the functional benefits. A family member spends fifteen to twenty minutes per day helping the patient to perform the stretching exercises. When walking becomes difficult, slightly more time is necessary to assist the child with standing and walking. The patient continues to do two to three hours of prescribed walking and standing daily34.
Many methods of treatment have been suggested for the control of contracture of the ankle13,16,26,29,30. Our study demonstrates that a comprehensive program that includes daily passive stretching exercises as well as a prescribed time for standing and, later, tenotomy of the Achilles tendon, posterior tibial-tendon transfer, and application of knee-ankle-foot orthoses effectively controls equinus contracture.
Many investigators have reported on the benefits of tenotomy and bracing for the treatment of contracture of the ankle4,8,10,11,13,16,19,37. However, the additional advantage of an ongoing program of physical therapy after bracing rarely has been addressed. Hyde et al.16 reported on twenty-four boys who had had a release of the Achilles tendon followed by application of knee-ankle-foot orthoses but who were not managed with an ongoing program of stretching exercises. The mean age at the time of the operation and bracing was similar to that of the seventeen patients in Group 3-A who were evaluated with regard to the development of contractures. Two years after the tenotomy and bracing, the seventeen patients in our study had less severe contractures of the ankle; the mean plantar flexion contracture in our patients was only 2.5 ± 4.3 degrees (range, 0 to 15 degrees) compared with 24.2 degrees (range, 15 to 50 degrees) for the patients in the other study. These results suggest that treatment with an operation and bracing alone does not control contracture of the ankle as well as the continued postoperative use of a comprehensive program of daily standing and passive stretching exercises.
Initially, we attempted to control contracture of the ankle with tenotomy, bracing, and passive stretching exercises. The varus deformity of the foot often progressed after the tenotomy, which made it painful for the patient to stand in braces. Spencer, in 1967, performed posterior tibial-tendon transfer in addition to tenotomy of the heel cord in order to correct the varus deformity and to balance the foot29. The findings of the present study suggest that contracture of the ankle is better controlled when a posterior tibial-tendon transfer is performed at the time of tenotomy and bracing. Five to seven years after tenotomy and bracing, the patients who had not had posterior tibial-tendon transfer (Group 3-A) had a mean contracture of the ankle of 9.9 ± 13.0 degrees (range, 0 to 40 degrees), while those who had had such a transfer (Group 3-B) had a mean contracture of only 4.9 ± 4.8 degrees (range, 0 to 20 degrees). This difference was significant (p = 0.004).
Bracing allows the patient to retain the ability to stand and provides good control of flexion contracture of the knee. Two years after bracing, the patients in Groups 2, 3-A, and 3-B had slight flexion contractures of the knee (mean, less than 5 degrees) at a mean age of 12.2 years. In contrast, two years after confinement to a wheelchair, the patients who had not had orthotic intervention (Group 1) had severe flexion contractures of the knee (mean, 46 degrees) at a mean age of 11.9 years.
We attempted to control the development of contractures in the upper extremities by prescribing daily passive stretching exercises of the elbow joint. However, severe contracture of the elbow developed despite the use of this program. The failure to control the progression of contracture of the elbow contrasts with the good control of contractures of the knee and ankle. The inability to control contracture of the elbow by stretching suggests that the chronically flexed position of the elbow of a patient who is not able to walk cannot be treated with stretching alone.
When walking with the aid of orthoses is no longer possible, additional physiological and biomechanical benefits may be derived from the use of orthoses for daily standing and transferring12,13,28. The present study demonstrates that management with an operation and bracing not only prolongs the ability of the patient to walk and controls contractures but also allows the patient to retain the ability to stand. The patients in our study who had had tenotomy and posterior tibial-tendon transfer retained the ability to stand and remained relatively free of contractures of the ankle and knee joints for a mean of 2.0 ± 1.3 years (range, 0.25 to 5.9 years) after having lost the ability to walk with braces.
The timing of operative intervention for patients who have Duchenne muscular dystrophy is controversial17. An operation performed early in the course of the disease has been reported to extend the duration of the ability to walk and to improve the quality of independent walking without the need for braces4,22-25. Rideau et al.24 reported that patients who had Duchenne muscular dystrophy and had had early operative intervention walked without braces until they were a mean of 10.6 ± 1.69 years old. Our patients who had had bracing or an operation and bracing were able to walk with braces until they were a mean of 13.6 years old. Thus, they retained the ability to walk for a considerably longer period of time than did patients who had been managed with early operative intervention only.
Advocates of early operative intervention have reported good initial control of contractures of the lower extremities4,17,22-25. However, such contractures are likely to recur when a patient who was managed with early operative intervention but not with bracing loses the ability to walk and is confined to a wheelchair.
In the present long-term study of patients managed at a single medical center, established methods of treatment were used to control contractures of the lower extremities and to prolong the ability to walk. Operative procedures combined with bracing and physical therapy, including daily passive stretching exercises and prescribed periods of standing and walking, were successful in controlling contractures of the lower extremities for as long as seven years after treatment. Our method of management allowed boys who had Duchenne muscular dystrophy to be able to walk until a mean age of 13.6 years and to be able to stand for an additional two years after the ability to walk with braces had been lost.