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Lower Limb Orthotic Management of Duchenne Muscular Dystrophy: A Literature Review

Stevens, Phillip M. MEd, CPO

JPO Journal of Prosthetics and Orthotics: October 2006 - Volume 18 - Issue 4 - p 111-119
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Although currently incurable, Duchenne muscular dystrophy remains treatable. The characteristic gradual loss of functional muscle and the concurrent developments of progressive contracture are often indications for orthotic interventions. As the disease progresses through the abbreviated life of the young man, he will encounter three functional stages: independent ambulation, assisted ambulation, and wheelchair mobility. Although controversy continues as to the appropriate role of orthoses during each of these stages, some generalities may be gleaned from a review of published literature. Specific patterns of weakness, accommodation, and contracture development characterize the initial stage of independent ambulation. Orthotic intervention is often confined to nighttime splints to slow the development of equinus contracture. As weakness and contracture progress, balance becomes increasingly precarious, and independent ambulation is ultimately precluded. Many authors have suggested that a degree of ambulation may be maintained during this phase by combinations of surgery, knee-ankle-foot orthoses and aggressive rehabilitation. The popularity of such procedures has declined since its peak in the 1970s and 1980s. Appropriate timing, patient selection, and rehabilitation appear to be essential in obtaining optimal outcomes. Weakness and contracture continue to progress until even assisted ambulation is precluded and wheelchair confinement ensues. Some authors have suggested a limited role of orthotic intervention in the form of postoperative positional ankle-foot orthoses to prevent recurrence of deformities. The relevance of corticosteroids, fracture incidence, and cognitive ability are also discussed.

The role of orthotic intervention in the treatment of patients with Duchenne muscular dystrophy is controversial. This article attempts to synthesize available literature as it relates to the orthotic management of these young men.

PHILLIP M. STEVENS, MEd, CPO, at the time of the study, was affiliated with Dynamic Orthotics and Prosthetics, Houston, Texas. He currently is affiliated with Specialized Prosthetic and Orthotic Technologies, Salt Lake City, Utah.

Correspondence to: Phillip M. Stevens, MEd, CPO, Specialized Prosthetic & Orthotic Technologies, 5292 South College Drive, Suite 103, Salt Lake City, UT 84123; e-mail: philmstevens@hotmail.com

Of the identified muscular dystrophies, the x-linked Duchenne muscular dystrophy (DMD) has been described as the most common and most severe. Although its incidence is still relatively rare, described variously as two to three cases per 10,000 live male births1 or one in 3,500 live male births,2 it is encountered with regularity in the orthotic community. Its degenerative processes begin at birth and continue through the next 2 decades, until it ultimately claims the life of the affected young man.1 Despite the relentless progression of the disease, many efforts have been made to optimize the abbreviated life of the child with DMD. As Siegel3 accurately reminded the medical community, “incurable is not synonymous with untreatable.” The characteristic gradual loss of functional muscle and the concurrent developments of progressive contracture are indications for appropriate intervention from the orthotic community as a part of the global management of this patient population.

The purpose of this report is to describe the physical presentations observed within this patient population during the various stages of disease progression and to review the published literature to date on the use of lower extremity orthoses across these same stages. It is not intended as a consensus of current practice techniques but an evaluation of the methods that have been used during the past several decades.

When treating the patient with DMD, it is helpful to consider the needs of the patient according to three chronologically encountered functional stages: independent ambulation, assisted ambulation, and wheelchair mobility. Perhaps because of the incurable but treatable nature of the disease, controversy exists regarding the appropriate orthotic intervention at each of these three stages. Although several authors have reported the average ages at which patients tend to transition from one stage to the next, there is tremendous heterogeneity from patient to patient.4,5 In addition, there has been increasing discussion and use of several medications that have been reported to slow muscle degeneration and thereby alter the natural history of the disease process. Therefore, categorizations and generalizations of anticipated function based solely on age should be avoided.

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STAGE 1: INDEPENDENT AMBULATION

Affected boys are unremarkable in their presentation at birth and through infancy as early developmental milestones such as rolling, sitting, and standing are reached within normal age limits.1,6 As toddlers, it is not uncommon for their walking to be delayed until 18 months or older.2 Deficits in gait are not typically noticed until 3 to 5 years of age.7,8 When first seeking medical opinions, parents often site clumsiness or an inability of their son to keep up with his peers at school. In the absence of a genetic history that would suggest the presence of DMD, definitive diagnosis is often delayed. In one study, Read and Galasko9 reported that although the average age of initial referral to an orthopedist was 3 years, the correct diagnosis of DMD was not assigned until an average of 2 years later.

As the disease progresses, functional muscle is incrementally replaced with fibrofatty tissue.1,10 This results in strength deficits while the muscle bellies may appear to be quite developed. This “pseudohypertrophy” is most commonly noted in the triceps surae. Although this attribute is common among patients with DMD, it is not always present. In addition, its presence may be secondary to other muscular dystrophies and should not, therefore, be considered exclusive to the DMD population.8

Weakness always occurs in proximal muscles before distal ones, initially targeting the hip and knee extensors.8,11 This weakness is often manifested at an early age in the child’s employment of the Gowers’ maneuver when transitioning from the floor to a standing position. Initially the child will roll onto his hands and knees in the prone position. He will then extend his knees, raising his buttocks upward. Next, he will use his upper limbs to “walk” his hands along his legs until the torso can be brought upright.1 As with the pseudohypertrophy of the calf muscles, the use of the Gowers’ maneuver is not exclusive to the DMD population but is simply a manifestation of weakened gluteal musculature that may be found in spinal muscle atrophies and other myopathies.1,8

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MECHANICS OF STANCE AND GAIT

During this functional stage, boys with DMD gradually develop a characteristic standing posture (Figure 1). Among the muscles of the lower limbs, hip extensors are the first to demonstrate critical weakness. Increasingly unopposed, the hip flexors contract and draw the pelvis into an anterior tilt. This allows the tensor fascia lata to pass further anterior to the greater trochanter, where it progressively shortens. In addition, as the trunk is drawn forward, aggressive lumbar lordosis and hyperextension of the spine occur. This positions the weight line posterior to the hip joint, thereby establishing passive hip stability and accommodating the weakened hip extensors. Concurrently, as knee extensors become increasingly weaker, the subject relies more on active equinus posturing of the feet and ankles bilaterally to maintain the weight line anterior to the knees and thereby establish a passive knee stability. Unlike hip and knee flexion contractures that usually remain mild as long as the child is ambulatory, equinus contractures continue to progress during this stage, gradually diminishing the child’s functional base of support. As balance becomes increasingly precarious, the child establishes a wider base of support by abducting the hips. The result is further shortening of the tensor fascia lata.12–16

Figure 1.

Figure 1.

Ambulation is similarly affected as the proximal weaknesses progress. During early ambulation, gait deviations are subtle. Excessive plantar flexion may be seen in swing phase, with a concomitant increase in hip flexion to assist in toe clearance. Cadence may be reduced, and initial contact is with the entire planar surface of the foot to minimize the early flexion moments experienced at the hip and knee in stance.5,6

As muscle weakness progresses, cadence continues to decline and changes are seen in both the coronal and sagittal planes. In the coronal plane, increasing gluteus medius weakness and the progressive shortening of the tensor fascia lata lead to incrementally exaggerated trunk leaning, increased shoulder sway, and the adoption of a wider base of support.5,6

In the sagittal plane, boys soon learn to position themselves so the weight line is anterior to the knee throughout single leg support, abandoning early stance phase knee flexion to accommodate their weakening knee extensors.1,5,6,17 This passive stability of the knee is assisted by the concurrent development of equinus contracture, such that several authors have cautioned against surgical overlengthening of the Achilles during this functional stage.17–19 Even if equinus contractures are minimal, there is evidence that as the proximal weaknesses progress, the child actively plantarflexes in stance for stability.5 Equinus may likewise be manifested in gait as the presence of early heel rise in terminal stance1 and ultimately as toe-walking.6,16 Throughout this functional stage, periods of prolonged immobilization secondary to minor trauma or illness should be avoided because the child may deteriorate quickly, losing the ability to walk.20

Progressive contracture of the hip and knee flexors is prevented by daily ambulation,8,18,20,21 and weaknesses can still be accommodated at this functional stage by the outlined compensations. Accordingly, orthotic interventions should be confined to attempts at delaying the development of severe plantarflexion contractures.

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ORTHOTIC INTERVENTIONS

Daytime ankle-foot orthoses (AFOs) should generally be avoided because they compromise increasingly precarious ambulation, placing excessive demands on incapable knee extensors during the loading response phase of gait.1,22 Furthermore, recent literature has drawn attention to the susceptibility of dystrophic muscles to permanent injury when subjected to eccentric contractions.23–25 Preliminary evidence has verified an increased external flexion moment at the knee when DMD patients ambulate with daytime orthoses.22 By requiring greater eccentric contractions of proximal extensors, the inappropriate prescription of daytime AFOs during this functional stage may actually further weaken the quadriceps, potentially shortening the child’s period of independent ambulation.

Nighttime AFOs are often prescribed at this stage in conjunction with passive stretching regimens.1,10,20 The effectiveness of night splints in altering the natural history of heel cord contracture formation has been questioned26,27 and warrants investigation.

In 1981, Scott et al.21 reported on 59 boys with DMD, in whom assessments of joint contractures and functional abilities were performed at 3- to 4-month intervals during a period of 3 years. The authors reported a delay in the loss of dorsiflexion range of motion among boys who had worn night splints and received regular daily stretching. These same boys were able to walk independently for longer periods. In contrast, boys who did not wear night splints and received no stretching were observed to require wheelchair confinement at earlier ages. The authors concluded that early and persistent splinting slows the development of contracture and enhances walking ability.21

In 1985, Seeger et al.28 reported a smaller case series in which the researchers followed up 12 boys for just more than a year. Reductions in plantar flexion contractures were observed in subjects who were compliant in the use of night splints combined with regular stretching. However, during an 8-week period when physical therapy was suspended and parental compliance with brace wear and home stretching could not be ascertained, equinus contractures increased.

In 1989, Brooke et al.4 published the broadest evaluation of the effects of passive joint stretching and nighttime AFOs on slowing the development of equinus contractures, reporting on 283 boys with DMD from four different medical centers. No correlation was found between the use of passive joint stretching and joint contracture. However, regular use of night splints was found to have a marked effect in reducing contractures of the heel cord.

In 2000, Hyde et al.29 reported on a prospective randomized study of 27 boys observed for a period of 30 months. Those treated with a combination of night splints and stretching experienced annual increases in equinus contracture that were 23% less than those treated with stretching alone.

A universal challenge in the provision of nighttime AFOs during this functional stage is the facilitation of compliance on the part of the patient and his family. In the treatment of cerebral palsy and other pediatric neuromuscular disorders, splints are typically molded in relative dorsiflexion to provide the maximum nocturnal stretch of the Achilles tendon. Sussman1 suggests that among the DMD population, night splints be molded with the ankle at neutral alignment to enhance patient tolerance and ultimately compliance. This is consistent with the observations of several authors that conservative interventions can, at best, only slow the progression of equinus contracture.1,19,20 Ultimately, the orthoses must be comfortable or they will not be worn.

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SUMMARY

Orthotic intervention during the independent ambulation stage is limited to the foot and ankle complex. Although proximal weakness is primarily responsible for the end of a child’s independent ambulation, extreme equinus contractures contribute to this eventuality. Daytime AFOs place excessive demands on increasingly weakening quadriceps and should generally be avoided. There is some evidence that compliant use of nighttime AFOs can modify the natural history of the disease process during this stage by slowing the progression of equinovarus deformities. The comfort of the orthoses plays a critical role in facilitating compliance.

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STAGE 2: ASSISTED AMBULATION

While contracture of the hip flexors, knee flexors, and plantar flexors may each play a part, it is ultimately the combination of progressive hip and knee extensor weakness that gradually precludes the child’s functional abilities.6,7,15,18 It has been observed that patients with DMD generally lose their ability to rise from the floor, climb stairs, and walk independently, in that order, and at intervals of approximately 1 year between each functional deficit.4,30 Although there is some variability among authors, the consensus observation is that the natural course of the disease will lead to increasing frequencies of falls, growing uncertainty in walking ability and ultimately the loss of independent ambulation.7,16,18–20,31

For a family coping with a disease characterized by a series of crises, the loss of ambulation may represent the biggest crisis since the initial diagnosis. As Gardner-Medwin15 expressed, “the loss of their boy’s ability to walk confirms in a graphic and inescapable way the prognosis they [the parents] had been given and had been hoping against hope might be wrong” (p 659).

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ORTHOTIC INTERVENTIONS

Prior to the early 1960s the sole treatment alternative of a child with DMD was temporary prolongation of ambulation through orthotic interventions, soon followed by confinement to a wheelchair.12,18,30 Then, in 1962, Spencer and Vignos18 reported the successful preservation of orthotic-assisted ambulation in 15 boys through the combination of Achilles tendon release, iliotibial band (ITB) fasciotomy, and the use of double upright knee-ankle-foot orthoses (KAFOs) with locking knee joints. The authors reported that although patients continued to slowly weaken at varying rates, an average of 24 additional months of orthotic-assisted ambulation was observed.18

In 1967, observing the unique strength retention of the posterior tibialis among the lower limb muscles, Spencer32 reported anterior transfer of these tendons through the interosseous membrane attaching to the cuneiform. This was done to restore some degree of muscular balance to the foot and ankle and prevent the recurrence of equinovarus posturing. Three years later, Roy and Gibson33 reported on 30 children treated according to Spencer’s modified protocols, including ITB fasciotomy, Achilles release, and posterior tibialis tendon transfer. In their series, walking was prolonged for a mean value of 25 months.

In 1968, Siegel et al.34 reported on their protocols in the treatment of 21 boys, incorporating Spencer’s original methods32 with the addition of proximal tenotomies of the sartorius and rectus femoris to address hip flexion contracture. The authors reported that all patients were able to stand without support and walk unassisted for short distances.34

Continuing to as recently as 2003, numerous others have reported similar results of an additional 2 to 4 years of orthotic-assisted ambulation using variations from the original surgical protocols of Spencer.6,14,16,19,31,35–41 The muscles treated surgically by the various authors, along with the mean values of the periods of assisted ambulation observed are summarized in Table 1. It should be noted that most of these studies were published in the late 1970s and early 1980s, with a limited number occurring in the past 20 years. The prevalence of such assistive procedures in current practice may be justifiably questioned.

Table 1

Table 1

There is consensus that if such ambulation-prolonging procedures are to be performed, they should be implemented as soon as the child loses the capability for independent ambulation and requires external assistance.14,19,31 One author reported increasing the frequencies of follow-up evaluations as gait and balance became increasingly precarious to ensure appropriate timing of the interventions.33 Periods of prolonged nonambulation increase disuse atrophy of muscle and contractures of weight-bearing joints, thereby compromising outcomes.15,18,31,39

Regardless of the type of surgical procedures performed, rapid and aggressive rehabilitation procedures are required after surgery. Research consistently advocates the immediate application of postoperative casts to allow for early standing and ambulation.14,16,18,31–36,39 Standing, and in some cases, walking, occurs on the first postoperative day14,16,31,32,34–36,39 but may begin as early as 12 hours after surgery.19 In the ensuing weeks, an aggressive physical therapy regimen is undertaken as the child regains balance and learns to ambulate with his new body alignments. Long-leg casts are used until orthoses are provided 1 to 3 weeks later.14,32,34–36,39 Prolonged postoperative immobilization should be avoided because of the patient’s susceptibility to rapid disuse atrophy.3

Orthoses should be lightweight, plastic KAFOs. Ischial shelves have been incorporated to allow the child to “sit” into the orthoses.13,34,36,39 The height of the orthosis is important. If too high, the patient is pushed forward out of balance; if too low, a severe kyphosis may develop.13 Locking knee joints substitute for weakening quadriceps.6 It has been suggested that the ankle region of the orthosis should provide a rigid anterior stop, allowing a secondary knee extension force anteriorly6 and preventing painful stretching of the Achilles tendon.14 At the ankle, slight dorsiflexion may be needed to facilitate the child’s balance of his upper body. Heel wedges can also facilitate this alignment.6 It has also been suggested that the foot plate of the orthoses should extend only to the metatarsal heads.39

Ambulation after such interventions begins with a walker until the child learns to balance with stability in the orthoses. Swing phase is compromised by the locked extension of the knee joints bilaterally, necessitating lateral trunk lean over the stance limb to lift the swing leg. Initial contact is instigated by the heel, translating into forward progression of the locked limb. Hyperlordosis of the lumbar spine and trunk hyperextension persist, keeping the child’s weight line posterior to the hip, thereby providing passive stability at that joint.6,18,36

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RATIONALE FOR ORTHOTIC INTERVENTION

A year is a long time in the life of a child,16 and the additional period of ambulation afforded by surgery and bracing may represent as much as 20% of that patient’s life span.3,36 Authors have cited numerous benefits associated with the provision of this second functional phase of orthotic-assisted ambulation. Factors associated with wheelchair confinement in the DMD population, such as scoliosis, obesity, disuse atrophy, osteoporosis, pathologic fracture, pressure sores, severe contracture at the hip and knee flexors, and the development of further foot and ankle deformity, may be avoided or postponed.6,18,35–36,39–42 Additional benefits to both gastrointestinal and pulmonary function have been suggested.14,42 Psychological benefits have been reported, including enhanced self-sufficiency, self-confidence, and increased independence,18 as well as a delay in the lack of motivation that can ensue once a child is confined to a wheelchair.36

The effect of prolonged ambulation on spinal deformities warrants individual consideration. In addition to being both unsightly and uncomfortable, scoliosis restricts ventilation and aggravates the respiratory problems that result from weakness of the intercostal muscles and diaphragm.43 Numerous authors have cited a delay in the onset of severe scoliosis when standing and walking are prolonged,6,14,39 additionally observing that by slowing the progression of the scoliosis, surgery is postponed until the child is older and more amenable to the procedures.4

In a comprehensive evaluation, Rodillo et al.44 reported on 93 boys who had undergone reambulation procedures. They found a significant difference between the Cobb angles measured in the boys who stopped walking before the age of 13 years (62° ± 32°) and those who ambulated beyond that age (32° ± 22°). The monthly progression in the later group averaged 0.95°, whereas that of the former group averaged 2.4°. A highly significant relationship was found between the Cobb angle and the number of months each boy spent in a wheelchair. The authors concluded that although severe scoliosis was postponed until wheelchair confinement in the boys who discontinued ambulation before age 13, these boys ultimately were more prone to the rapid progression of scoliosis associated with puberty than were those who walked beyond 13 years of age. In this second group, it was hypothesized that the symmetrical lordosis associated with standing reduced pelvic tilt and stabilized the spine by locking the lumbar facet joints. The lateral flexion of the spine associated with walking was thought to avoid any prolonged fixed positions.44

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PREDICTING SUCCESS OF REAMBULATION PROCEDURES

Even given the benefits reported with successful orthotic-assisted, ambulation-prolonging procedures, the procedures remain controversial, with skeptics arguing that rewards are outweighed by “the frustration, inconvenience and cost involved.”35 Others have raised concerns about the excessive energy cost of braced ambulation and safety concerns in the event of a fall.10 Although the aggressive procedures outlined earlier have prolonged both independent and assisted ambulation for as many as 62 months and 85 months, respectively,31 in some cases the same protocols and procedures, performed at the same centers, have prolonged ambulation by only a few months.31,33,35 For these reasons, there have been several attempts to isolate the factors that might predispose a boy with DMD toward successful outcomes during this second functional stage.

Reporting on their 9 years of operation at the Muscle Clinic at Arkansas Children’s Hospital, Bowker and Halpin14 identified both physical and psychosocial considerations in the selection of patients for reambulation procedures. Positive physical considerations included residual balance and the ability to take a few steps at the time of intervention. Negative considerations were periods of nonambulation exceeding 3 to 4 weeks with concomitant joint contracture and disuse atrophy, and an obese body habitus. Beneficial psychosocial considerations were positive family attitude, family stability, and family understanding of the procedures.14

In a more critical evaluation of 17 consecutive patients, Ziter and Allsop35 reported that bilateral Achilles tenotomy followed by orthosis-assisted ambulation was most effective in boys who ambulated independently until at least the age of 10 years, retained residual muscle strength of at least 50%, and did not show certain competing factors, including obesity, mental retardation, prolonged wheelchair confinement, undue family and psychological stress (such as that caused by parental divorce), or poor compliance. In the cases of more rapidly deteriorating patients who lost the ability to ambulate independently before age 9, patients and families were observed to welcome the mobility of a wheelchair over the orthotic treatment.35

Citing the attempts of earlier authors as being based on clinical impressions, rather than systematic analysis of data, Vignos et al.31 used linear and multiple regression to identify the variables most predictive of bracing outcomes among the DMD population. In that study, published in 1983, five variables were identified, including muscle strength, patient motivation, vital capacity, and certain laboratory indicators. The authors then developed a series of equations that would allow the physician to better predict the expected prolongation of ambulation on a case-by-case basis in the clinic setting. Using the values of each of the five variables on a patient-specific basis, such predictions would then facilitate a more informed decision on the part of the patient and his family when considering the expense and time commitment.31

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SUMMARY

Multiple authors have reported on the ability to extend the ambulatory period of most boys with DMD by an average of approximately 2 years through surgical contracture management and the fitting of bilateral KAFOs. If the number of published reports is reflective of prescription patterns, these techniques achieved their greatest popularity through the 1970s and 1980s, with declining use since then. These interventions should be timed correctly, immediately at or after the loss of independent ambulation. Once surgical intervention has been performed, the rehabilitation of the child must proceed quickly, with standing and/or walking occurring on the first postoperative day. Not all boys with DMD will benefit from these expensive and intense procedures, and factors such as remaining strength, motivation, and residual walking ability should be considered.

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STAGE 3: WHEELCHAIR CONFINEMENT

Once weakness progresses to the point where assisted ambulation is no longer possible, the child is confined to a wheelchair. In the absence of standing, flexion contractures of the hips and knees develop quickly. Equinovarus deformities are also common during this stage19,20 and can ultimately progress to painful subluxation of the midtarsal joints.19 From an orthopedic perspective, most attention is now turned to the spine, where scoliosis is often observed.1,20 With respect to the lower limbs, preservation of joint range at the hip and knee is no longer feasible or necessary, and any interventions are again directed solely at the foot and ankle complex.

In 1984, Williams et al.19 reported on the surgical elongation of the Achilles tendon as well as divisions of the tibialis posterior, flexor hallucis, and flexor digitorum longus to restore a neutral foot and ankle alignment. After 6 weeks of postoperative short leg casts, nighttime AFOs were provided. The authors reported compliance to be variable such that it was not possible to draw conclusions about the effect of orthoses in reducing the rate or severity of recurrence.19

One year later, Hsu and Jackson45 outlined the appropriate indications for surgical intervention on the feet of nonambulatory patients with neuromuscular disease. These included the prevention of pressure sores and skin breakdown, particularly on the dorsolateral aspects of the feet, pain, the need to obtain a shoeable foot so as to better protect it from the environment, and the need to facilitate a plantigrade foot so that it can rest on the footplate of the wheelchair and provide stability to the legs. They advocated lengthening the Achilles and anterior transfer of the posterior tibialis tendon in such cases. Following the use of postoperative short leg casts, AFOs were provided to prevent recurrence of deformities.45

In 2002, Scher and Mubarak41 reported on a series of five nonambulatory patients who underwent anterior transfer of the posterior tibial tendon and Achilles lengthenings, indicating that orthoses are not necessary following surgery.41 In contrast, 3 years later, Leitch et al.46 reported on 30 nonambulatory patients who underwent similar surgical procedures. As with the study of Hsu and Jackson, after 4 to 6 weeks of postoperative short leg casts, AFOs were routinely fitted. Interestingly, among both those who received and those who declined surgical intervention, the authors reported none of the boys wore his AFO routinely.46 In addition, the authors found no significant differences with respect to shoe wear, pain, hypersensitivity, or cosmesis between those who accepted and those who declined surgical correction of their feet.

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SUMMARY

The role of lower limb orthotic intervention during the wheelchair stage of DMD is limited to the foot and ankle. In the instances in which the need for corrective surgery outweighs the operative risks to the patient, some authors have suggested there is value in the use of postoperative nighttime AFOs to prevent recurrence of the deformity. The orthoses must be comfortable to augment patient compliance.

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OTHER CONSIDERATIONS

Although not immediately related to orthotic interventions, there are other factors that warrant awareness among the orthotic community, including the increased use of corticosteroids, the elevated risk of fracture within the patient population, and cognitive understanding.

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CORTICOSTEROIDS

As early as 1974, reports were published on the use of corticosteroids to alter the natural history of the muscle disease itself.47,48 These early reports demonstrated initial improvements in muscle strength and function among ambulatory patients47 and ultimately a less rapid progression of the disease when compared with that in controls.48 It is beyond the scope and intent of this paper to review the literature that has been produced since these early studies, as has been done elsewhere49; however, some general findings should be considered.

Of relevance to the orthotist is the reality that the use of corticosteroids has consistently been demonstrated to alter the natural history of the muscle disease. Independent ambulation has been prolonged with the use of both prednisone50 and deflazcort.51 Other benefits have included improved and temporarily sustained muscle strength, motor function, and pulmonary function.49 Common side effects to these treatments include weight gain and growth suppression.49

The role of orthotic intervention in the treatment of patients treated with corticosteroids undoubtedly will be re-examined in light of these alterations. For some patients, sustained muscle integrity may obviate or postpone the need for orthotic interventions. For others, these interventions may prolong stage 1 and stage 2 functions, making careful orthotic prescription increasingly relevant. Either way, practitioners should appreciate that variations to the natural history of the disease process of DMD may be encountered with increasing regularity.

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FRACTURES

Fractures are common in boys with DMD, with reports varying from 21% to 67%.10,52 This has been attributed to skeletal changes, including osteoporosis and decreased build-up of cortices in long and flat bones.53 In addition, diminished power and motor agility may predispose the child to an increased susceptibility to injury.10

Among boys in stages 1 and 3, fractures are reported most frequently in the lower limbs.10,52 Subjects in stage 2 are more likely to experience upper limb fractures, presumably in their attempts to prevent a straight leg fall using outstretched arms.10,52 Although concerns have been raised about the risk of falling during this stage of assisted ambulation, published reports indicate that boys are more likely to injure themselves in a fall from a wheelchair than when wearing lower limb orthoses.4,10,52

Even in the early stages of the disease, bone density in the proximal femur is considerably diminished,52 and unsurprisingly, the femur is the most common sight of fracture.4,10,52 This is particularly common during wheelchair transfers, and caution should always be used when these types of transfers are undertaken.54

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COGNITIVE UNDERSTANDING

It has been observed that boys with DMD have lower IQ scores than their peers, with a mean value between 80 and 90.1,34 However, more detailed analyses have revealed that such figures reflect selected deficits in younger boys. Although lower performances in verbal reasoning, verbal processing, and attentional-organizational skills have been observed in younger populations, older children were less likely to present with these shortcomings.55,56 Accordingly, just as interactions with younger boys should allow for such cognitive deficits, interactions with older boys should avoid condescension.

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CONCLUSION

The role of orthotic intervention in the treatment of patients with Duchenne muscular dystrophy is controversial. Considerable variation has characterized its use regionally, locally, and temporally. This article represents an attempt to synthesize available literature as it relates to the orthotic care of these young men. During independent ambulation, interventions generally should be confined to nighttime AFOs in an attempt to slow the progression of equinus contractures. For carefully selected patients treated at experienced centers, independent ambulation may be prolonged through surgical contracture releases, KAFOs and aggressive rehabilitation. Such exhaustive attempts to prolong an assisted stage of ambulation appear to be less common. Once ambulation ceases, lower limb interventions, if indicated, should be confined to the foot and ankle complex in an attempt to maintain any surgical corrections and deter the progression of deformities.

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Keywords:

Duchenne muscular dystrophy; lower limb; pediatric

© 2006 American Academy of Orthotists & Prosthetists