|Year : 2007 | Volume
| Issue : 5 | Page : 44-54
Evolution of abnormal postures in Duchenne muscular dystrophy
Maria Kinali1, Marion Main2, Eugenio Mercuri3, Francesco Muntoni1
1 Department of Paediatrics, Dubowitz Neuromuscular Centre, Imperial College, London, United Kingdom
2 Department of Physiotherapy, Hammersmith Hospital Trust, London, United Kingdom
3 Department of Paediatrics, Dubowitz Neuromuscular Centre, Imperial College, London, United Kingdom; Department of Child Neurology, Catholic University, Rome, Italy
Dubowitz Neuromuscular Centre, Department of Paediatrics, Division of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road,London W12 ONN, United Kingdom
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Spinal deformities are common abnormalities of posture observed in Duchenne Muscular Dystrophy (DMD). Spinal alignment is the result of the integrity of different variables, ranging from normal vertebral development to balance and symmetry of tone and strength, normal control by central pathways and integrity of the sensory feedback. Any disturbance altering one or more of these variables increases the risk for developing abnormal postures. Scoliosis is a frequent complication (68-90%) of DMD. Although the risk of developing scoliosis is higher in non-ambulant DMD patients, scoliosis and kyphosis can be found occasionally in ambulant patients. In DMD patients the onset and the evolution of the abnormal postures are related to the onset and the progression of weakness. This review discusses the factors affecting posture in DMD, especially in relation to scoliosis and gives an overview of general guidelines on the diagnostic approach and some management issues related to DMD.
Keywords: Duchenne muscular dystrophy, management, posture, scoliosis
|How to cite this article:|
Kinali M, Main M, Mercuri E, Muntoni F. Evolution of abnormal postures in Duchenne muscular dystrophy. Ann Indian Acad Neurol 2007;10, Suppl S1:44-54
|How to cite this URL:|
Kinali M, Main M, Mercuri E, Muntoni F. Evolution of abnormal postures in Duchenne muscular dystrophy. Ann Indian Acad Neurol [serial online] 2007 [cited 2020 May 26];10, Suppl S1:44-54. Available from: http://www.annalsofian.org/text.asp?2007/10/5/44/33496
| Introduction|| |
Scoliosis, kyphosis and lordosis and abnormal seating postures are almost invariable features in patients affected by neuromuscular disorders, of which Duchenne muscular dystrophy (DMD) is the most common. The recognition of these abnormal postures is important as they ultimately interfere with activities of daily living, function and quality of life. The assessment and management of posture is thus one of the most important aspects of the medical and rehabilitative care of these patients.
Spinal alignment is the result of the integrity of different variables, ranging from normal vertebral development and normal muscle power to balance and symmetry of tone and strength, normal control by central pathways and integrity of the sensory feedback. Any disturbance altering one or more of these variables increases the risk of developing abnormal postures.
Scoliosis is a frequent complication of DMD (68-90%).,,,,,,,,, Although the risk of developing scoliosis is higher in non-ambulant DMD patients, scoliosis and kyphosis can be found occasionally in ambulant patients. Spinal deformities are common but they are not the only abnormal postures observed in DMD as severe joint contractures may also be responsible for abnormal seating or standing postures. In some DMD patients, worsening contractures of the lower limbs (often asymmetrical) are responsible for abnormal seating postures even if no spinal deformity exists.
In DMD patients, the onset and the evolution of the abnormal postures are related to the progression of weakness. This review discusses the factors affecting posture in DMD, especially in relation to scoliosis. We will give an overview of general guidelines on the diagnostic approach and some related management issues.
| Scoliosis|| |
In DMD, untreated scoliosis is associated with multiple complications such as compromised seating and trunk balance, discomfort, pain and difficult attendant care, exacerbation of any underlying cardio- respiratory dysfunction.,,, Spinal surgery is considered the treatment of choice, for almost all DMD boys soon after their confinement to a wheelchair, a practice now adopted by several different centers worldwide.,,
In the recent years the natural history of DMD has changed due to the effect of better overall management and intervention. Survival has been extended to mid twenties, and a number of nonrandomized studies now report a reduced prevalence and severity of scoliosis.
Prevalence-incidence of scoliosis in DMD
Scoliosis prevalence in DMD is strongly related to age and weakness. Several studies have reported that more than 90% of DMD boys will develop scoliosis after having lost the ability to walk, with typical onset between 11-16 years.,,,, Approximately 50% of DMD boys acquire scoliosis between 12-15 years, with a sharp deterioration at 13 years or one to two years after wheelchair confinement. Only a few studies have reported onset of scoliosis (£30o) in DMD boys who are still walking albeit with difficulties (independently or in knee-ankle-foot-orthoses).,,, Heckmatt et al. reported scoliosis of less than 30o Cobb angle in 12/27 (45%) of DMD boys studied whilst walking in their KAFOs. Smith et al. Reported scoliosis of less than 20o Cobb angle in 51 DMD boys who were in the late stages of ambulation. It is quite likely that this mild, sub clinical, scoliosis, a problem of the late ambulant stages of the disease, is under recognised in the various series reported, as scoliosis X-rays are not routinely done until loss of ambulation.
Although scoliosis is a very common problem in DMD, it is also not an inevitable complication. Up to 19-38% of DMD boys aged up to 16 years, had not developed any scoliosis,,, or had only got mild-moderate scoliosis (<35o in up to 25% of cases)., Oda et al.  reported 15% of DMD patients having mild curvatures (10-30o) and McDonald 10% with no clinical scoliosis. These patients have been either managed conservatively, or operated upon, according to the various units' protocols. We have recently found that approximately a quarter of our patients (28/123=23%) did not have any scoliosis or only had a minimal scoliosis, £30o at aged 17, when growth was completed.
The reason for this marked variability in prevalence of DMD scoliosis remains unclear. It is possible that any combination of the following reasons might account for this discrepancy such as different criteria for scoliosis definition (inclusion or exclusion of minimal curvatures), differences in management and intervention amongst various units; non comparable DMD age groups reported.
Patterns of scoliosis in DMD
Different scoliosis patterns have been described in DMD, taking into account the presence of kyphosis, hyperlordosis, rotation or pelvic obliquity. Wilkins et al postulated that scoliosis in DMD is the result of loss of lateral support from the paraspinal muscles. They classified 62 late ambulant DMD boys as having one of the following types of spinal configuration: early straight (group 1); kyphotic (group 2); kyphoscoliotic (group 3); scoliotic (group 4); and extended spine (group 5). Muscle strength of the paraspinal muscles was better preserved in those DMD boys with an early straight spine and was reduced with transition from a kyphotic (group 2) to a scoliotic without an extended spine (group 4).
Oda et al. also classified the natural history of scoliosis in DMD. Type 1 (unremitting progression of scoliosis with kyphosis); type 2 (transition from kyphosis to lordosis before age 15 years); or type 3 (milder deformity without prominent longitudinal changes). Type 1 scoliosis was due to a collapsing spine with rotation. DMD boys with type 1 scoliosis had reached 30o Cobb angle before aged 15 years and tended to progress rapidly after that, an indication for surgery. Type 2 had no uniform course and the authors could neither predict the final outcome nor whether later spinal surgery would be needed. Granata et al. described three patterns of scoliosis: 1) kyphoscoliosis as the most frequent deformity with the most rapid evolution; 2) lordoscoliosis and 3) hyperlordosis with spinal rigidity.
| Factors Affecting Posture in Children with DMD|| |
The factors affecting posture in children with DMD are different from those observed in other neurological disorders observed in a paediatric population, such as cerebral palsy. In cerebral palsy, scoliosis or more generally spinal deformities and abnormal postures are mainly related to an imbalance of tone between different groups of muscles, such as asymmetrical increased tone of the paraspinal or more generally the control of trunk and limb balance by central pathways. In children with DMD, in contrast, the prominent factor is muscle weakness but an array of different factors due to the underlying pathology may influence the course of disease and the eventual development and progression of spinal asymmetry/scoliosis and other abnormal postures.
Weakness is the major contributing feature of DMD. Where the child becomes functionally more dependent due to increase in size the effect of weakness becomes increasingly more pronounced. A child with weakness where both head and trunk control are compromised, leading to inability to attain a stable, functional and symmetrical sitting or standing position, is at risk of deformity. Asymmetry of power may be more important than the degree of weakness. Muscle imbalance, both between sides of the body and between agonists and antagonists, can be responsible for abnormal postures both directly, when producing imbalance of the paravertebral muscles or indirectly, leading to contractures, preferred sitting and standing postures and asymmetrical gait patterns that will ultimately lead to spinal deformity.
| Common Concepts About Predictive Factors Influencing Scoliosis|| |
The likelihood of curvature development and progression is variable and multifactorial. Because of this the prediction of the final spinal deformity can be difficult. Many of the factors that cause asymmetry of posture in DMD are relevant to both ambulant and non-ambulant children.
Different factors have been postulated to explain curvature onset and progression. These can be broadly divided into those which are protective and those, which aggravate scoliosis. A lordotic posture, walking and/or standing beyond 13 years and a higher predicted FVC at 10 years are thought to be protective for scoliosis development.,,,, At variance, pubertal growth spurt and skeletal maturation, an asymmetrical stance, an asymmetry of lower limb flexion contraction deformities, pelvic tilt and prolonged wheelchair use, hand dominance, curvature magnitude, convexity and location, the degree of paraspinal muscle fibrosis, are thought to be aggravating factors for scoliosis.,,,,
No cause-effect relationship has been established between all the above factors in randomised-controlled studies. Some of these factors have been discussed controversially and/or subsequently refuted. These studies are discussed below.
| Determinants of Scoliosis Curvature Onset and Progression|| |
(i) A lordotic posture
A lordotic posture is thought to prevent scoliosis and loss of the lumbar lordosis increases the severity of scoliosis. Increase in the normal lumbar lordosis is frequently present and is often due to a compensatory mechanism in the ambulant boys who have proximal muscle weakness.
In DMD the weakness is most profound in the hip extensors but may also affect the hip abductors and adductors. The pelvis becomes unstable due to this weakness and frequently in the ambulant DMD boy action of the iliotibial bands (ITBs) will compensate for instability and pull the pelvis into anterior tilt. The trunk then adopts a lordotic posture to balance. Wilkins et al. postulated that this lordotic posture makes spine more "stable" as the facet joints are locked in hyperextension allowing very little lateral mobility thus affording scoliosis protection. They quoted observations in DMD patients, non-human primates and examination of articulated spinal specimens. Maintaining walking and standing (supported in KAFOs or in standing frames) preserves the lumbar lordosis in DMD and is therefore thought important to protect from scoliosis onset and development. Galasko claimed that a supported standing regimen, in patients who had lost ambulation and provided with standing frames appeared to delay the onset and progression of scoliosis and indirectly preserve lung function (FVC, PEFR), both being worse in those DMD boys who did not stand. Conversely the loss of lumbar lordosis due to worsening hip flexion contractures especially in non-ambulant patients can contribute to further deterioration of scoliosis.
Functional level is considered one of the major indicators of disability in DMD and there is a direct link between functional level and development of scoliosis. Many studies have shown that maintaining ambulation is one of the most important factors in preventing or slowing the progression of scoliosis. Intervention strategies, which include stretching exercises, nocturnal ankle-foot-orthoses, rehabilitation in lightweight Knee-ankle-foot-orthoses (Calipers/KAFOs) and glucocorticoids, contribute to the prolongation of walking and standing.,,,,,
(ii) Rehabilitation in long leg orthoses (Calipers/KAFOs)
Rehabilitation in long leg orthoses (Calipers/KAFOs) at the time of increasing difficulties in independent walking has been effective in prolonging walking and standing beyond 13 years. The technique was initially introduced in 1962 by Spencer and Vignos in 15 DMD boys and shortly afterwards in the UK (1964). The technique was streamlined further with the use of lightweight KAFOs rather than conventional orthoses as part of an active rehabilitation programme in our center. 57 MD boys were originally reported to have been rehabilitated in KAFOs., Of note there was a lack of correlation between the age at rehabilitation in orthoses and duration of its use. Since 1972 we have offered rehabilitation in KAFOs to approximately 90% of DMD boys at the end of independent ambulation i.e.: boys who are almost totally wheelchair dependent, taking only a few steps or standing momentarily with/without assistance, as the chances for severe lower limbs contractures are still small., KAFOs can prolong independent walking for an average of 18 months to two years and standing up to 50 months. The procedure is not performed in DMD boys with severe cognitive or behavioural problems unable to collaborate with the rehabilitation program.,
A study performed in 1988 on 93 DMD boys at the Hammersmith Hospital suggested a reduction of scoliosis incidence to 65% of boys in the older DMD population (13-20 years). There was an inverse relationship between the severity of scoliosis and the age when ambulation was lost in KAFOs. Prolongation of ambulation in KAFOs for a further 22 months was observed in 22% of DMD boys who walked beyond aged 13 years. They all showed slower scoliosis evolution (mean rate of deterioration 0.5o-0.95 o /month) compared to the boys who had stopped walking before 13 yrs (2.4o /month respectively). Scoliosis was also milder (mean Cobb: 32˚ versus Cobb 64˚ respectively).,
Glucocorticoids have been proven to be effective in prolonging independent walking ability for a variable length of time according to the age of the DMD boy at their onset, regime and length of treatment. In six nonrandomized studies published since 2004, steroids might have a role in reducing scoliosis prevalence and severity (0-30% with scoliosis >20˚-30˚) and even the need for spinal surgery (0-11%).,,,, It remains however obscured whether this protective role of glucocorticoids on scoliosis is related to the prolongation of walking per se and/or to an additional effect on increasing the strength of axial muscles. Given that scoliosis tends to progress until the end of puberty it is important that follow-up beyond puberty especially of those DMD continuing to be treated with glucocorticoids is established in order to demonstrate a lifelong protection from scoliosis (prevention or delayed onset). This is important as administration of glucocorticoids significantly delays the age at which final skeletal maturation is achieved.
| Aggravating Factors in Development of Scoliosis|| |
(i) Pubertal growth spurt
Children grow and change in height and weight. With age also comes change in functional demands on the body. The education, home and social integration needs of a child change and become more exacting. The child with DMD will also be subject to these pressures and they will, in turn, affect posture. Even in nonprogressive neuromuscular diseases, as the children grow, they tend to have increasing scoliosis as the trunk "concertina's" against the increasing forces. With the common growth spurts seen in childhood, but most noticeably around puberty, increasing difficulty with or loss of ambulation will add to the development of spinal deformity. Amongst the most obvious of these changes is the advancing linear growth including the trunk length; the latter has to be kept upright by weakening axial muscles, which in DMD boys do not get stronger to cope with the increasing loading demands. Scoliosis is likely to progress considerably if present before the onset of the rapid pubertal growth and adolescent skeletal maturation. The accurate staging of puberty (" Tanner staging" ) and less frequent signs such as the ossification of the iliac apophysis (" Risser sign" ), have allowed the evaluation of the remaining growth potential of the spine in conditions such as adolescent idiopathic scoliosis, but far less so in DMD. Tanner staging in studies of bone mineral density has shown delayed puberty in DMD boys. The accuracy of the "Risser sign" remains doubtful when not assessed by experienced clinicians; the iliac apophysis is often obscured in the routine scoliosis AP views (X-rays) in DMD boys with severe scoliosis who are obese and are constant wheelchair users and has, therefore, not been used routinely in assessing DMD scoliosis. Most of the studies have not reported on scoliosis progression after the end of puberty. There are two main reasons for this, namely, DMD patients did not previously survive long enough after the end of puberty to be able to assess their scoliosis evolution and most importantly they almost exclusively had been operated upon for their scoliosis, once non-ambulant. Due to the extended survival into adulthood it would be of interest to report whether scoliosis continues to progress into early adulthood. This last point will determine the need for an on-going monitoring of DMD patients with scoliosis into early adulthood, which is not a routine practice.
(ii) Lower limb contractures and pelvic tilt
Contractures are a feature of DMD and while they may not be apparent at onset, they will develop through weakness, muscle imbalance, position and immobility. Studies have shown that tight tendo-achilles (TAs) and iliotibial bands (ITBs) are the primary contractures with hips, knees and upper limb contractures becoming more pronounced with increasing age and loss of ambulation.
Lower limb contractures of ITBs or hamstrings especially in ambulant DMD patients, hip flexion contractures, hip subluxation and pelvic tilt, curve convexity and dominant side, have all been hypothesized as aggravating factors for scoliosis development. In any neuromuscular disorder, the specific joints affected by contractures will vary, although not all will influence spinal posture directly, such as upper limb contractures, but any contracture that affects function may indirectly have an effect. Like power, it is more frequently the asymmetry of contractures rather than the actual size that will lead to asymmetry of posture. While this may be more apparent in the ambulant child, asymmetry of the hip and ITB contractures can cause pelvic obliquity and poor sitting position. The ITB, although not a muscle, acts over both the hip and the knee joint and contracture of the fibrous band will pull the hip into abduction and flexion, with anterior tilt of the pelvis. The asymmetrical contracture of the ITB bands determined the direction of the curve in 105 natural history DMD patients who developed scoliosis (95%) after the loss of ambulation. The influence of hip contractures and pelvic obliquity on the convexity and progression of scoliosis was discussed in a German study. The authors studied the relation between prolongation of walking, incidence of scoliosis and lower limb contractures. All 45 DMD boys included had scoliosis surgery. Scoliosis was absent in the ambulant patients but present in 96% once constant wheelchair users. All patients had hip flexion or ITB (hip abduction) contractures, asymmetrical in the great majority (80%). The side of greater contracture determined the side of scoliosis convexity.
Pelvic tilt is part of a complex deformity involving the spine and the hips. Four different types of pelvic tilt can be recognized by viewing different planes and accounting for the deforming forces, some of which relate to certain neuromuscular disorders. Chan et al. showed that hip subluxation and dislocation is a frequent finding (35%) of the hip X-rays in DMD. Most of these X-rays were taken late in the course of follow-up and just prior to spinal stabilization for those that had surgery. The authors showed a linear positive relationship between advancing age ( P <0.001), pelvic tilt ( P =0.002) and scoliosis severity. The possible progressive relationship between subluxation and pelvic tilt and its impact on sitting balance, comfort and scoliosis deterioration was also discussed. Pelvic obliquity, when the pelvis is not level in the sitting or standing position provides an unstable sitting base and affects the degree of spinal asymmetry. Whether the development of pelvic obliquity precedes or follows the development of scoliosis has never satisfactorily been proven but once the pelvic deformity is fixed, then the compensatory postures will in turn, become more pronounced to maintain balance, comfort and functional head position. Leg length discrepancy, either real or apparent will affect the level of the pelvis in standing. This can be caused by a single hip subluxation or true shortening following a fracture. Weakness and inability to achieve ambulation are often underlying causes of hip subluxation or dislocation. However, these are rarely seen in DMD and when they do occur, it is after the onset of scoliosis or following spinal surgery.
(iii) Paraspinal muscle degeneration
It has been speculated that asymmetrical paraspinal muscle degeneration leads DMD patients to adopt initially a compensatory posture and subsequently a persistent poor posture with scoliosis. Muscle imaging by either CT or MRI may also help in identifying different mechanisms underlying weakness and scoliotic posture. Although this has not been systematically investigated there is increasing evidence that a detailed MRI protocol using different sequences, including T1, T2 and STIRS sequences may provide information not only on the extent and severity of muscle involvement (seen as increased signal on T1) but, using 'fat suppression' sequences may also distinguish between fat and fibrotic tissue replacement of the muscles. Two studies were designed to determine whether the degeneration of the paraspinal muscles was a potential mechanism of developing scoliosis., Computer tomography (CT) was used to look into the erector spinal muscles of the ninth dorsal and the third lumbar vertebrae level in 31 DMD boys. Loss of paraspinal muscle and replacement by fat was greater on the concave side and lateral portion than that of the medial portion. The density differences between the convex and concave sides correlated with the degree of curvature measured by the Cobb method., As the CT was taken close to the scoliosis onset, the changes seen in the paraspinal muscles might indeed reflect the secondary changes seen in the muscle of older age DMD boys.
Many nonambulant DMD boys are unable to change their posture or position once in their wheelchairs, because of their weakness. A persistent adoption of a poor sitting posture may become a fixed scoliosis posture further compromised by the effects of gravity. It is therefore only natural to assume that scoliosis severity increases with time spent in a wheelchair and advancing age. Rodillo et al. demonstrated a positive relationship with scoliosis severity and the time spent (months) in a wheelchair. Lord et al. showed a relationship between wheelchair use and scoliosis only after 3.5 years wheelchair reliance.
| Other Proposed Factors in the Development of Scoliosis|| |
Yamashita et al., examined various factors in order to predict scoliosis severity: 1) vital capacity (VC) at 10 years, 2) the age at which ambulation ceased and 3) Cobb angles at 10 years and 4) Oda's classification for the spinal deformity. The strongest predictor was the VC at age 10 years. Yamashita et al., were able to predict the severity of scoliosis in 91.7% of 12 DMD studied, although the significance of the findings by using multiple discriminant analysis remains doubtful in view of the very small number of DMD studied.
McDonald et al. showed 15% of DMD boys to have scoliosis before wheelchair reliance although a further 40% had no clinically detectable scoliosis even after three years of continuous wheelchair use. Other authors have not demonstrated a causal relationship between wheelchair reliance and scoliosis.
Adaptive, custom made and structured seating may provide support and comfort, enable better function and improve sitting position, but in studies, it has not been shown to alter the natural history of scoliosis.
Scoliosis has not been confirmed as being related to hand dominance (defined as the extremity used for writing and self-feeding). Despite the fact that Johnson et al. showed a correlation between hand dominance and scoliosis convexity in their study in 1976, a further study did not confirm this relationship. The authors looked into the relationship between hand dominance or prolonged use of one upper extremity and convexity of the spinal curve in 26 constant wheelchair DMD users aged between 11 and 23 years (average 16.5 years), 6/26 of them operated upon. It is customary that the side of the control of an electric wheelchair corresponds to the dominant side of the DMD boy. It is common in the smallest of electric wheelchairs for the control to be central, but this is less functional for the older school-age DMD boy where the control can prevent access to the work surface. Thus placement of the wheel chair drive control in the midline is unlikely to alter the convexity of scoliosis.
| Clinical Examination|| |
Curvature may be noted in the thoracic or lumbar or thoracolumbar regions. The examiner should inspect the spine for possible evidence of a curvature preferably in the standing but also in the forward flexed posture. Thoracic curvature tends to impact on the cervical spine, shoulder girdle and/or respiratory function, depending on the anatomical level (i.e., higher vs. lower thoracic) and their severity. The patient may have a resulting asymmetry of the shoulders, rib rotation or a rib kyphosis. Lumbar or thoracolumbar curvatures, depending on their extent, may cause asymmetrical waist contours, back pain, pelvic obliquity and secondary hip subluxation and dislocation. Lumbar scoliosis may be difficult to identify clinically especially if the examiner does not assess for pelvic obliquity. The latter can be assessed by examining for an apparent or true leg length discrepancy in those still walking or asymmetrical ischial weight-bearing in sitting.
The Cobb angle technique and scoliosis diagnosis and monitoring
The most useful tool in the diagnosis of scoliosis is a high quality plain radiograph. It is usually sufficient to have a frontal and lateral assessment of the whole thoracic and lumbar spine from vertebra C7 to the sacrum and iliac crest, with the patient standing erect if ambulant. In DMD patients with difficulties in walking and standing, standing X-rays tend to be substituted with sitting views on low stool.
The Cobb angle technique is the accepted gold standard for quantifying scoliosis on X-rays [Figure - 1], monitoring and decision-making regarding scoliosis management., One limitation is that Cobb angle measurements are based on a two-dimensional radiograph of a deformity that is effectively three-dimensional (i.e. does not take into account spinal rotation).
Scoliosis is defined as the lateral curvature of the spine, apparent on the coronal plane, which measures ³ 10o Cobb angle and is usually associated with vertebral rotation. Longitudinal spinal X-rays are used to monitor scoliosis evolution. In most centers this is a standard practice four to six monthly with only frontal (anterior-posterior, AP) sitting views. If a 10° change has occurred between two consecutive X-rays, one can confidently (95%) diagnose a true progression over a given time,, and the rate of progression of scoliosis can be worked out. In the clinical context, less that five degrees curvature progression can be due to intra-observer variability or a diurnal variation in posture. The clinical assessment should also include structured scales for the assessment of strength, such as the Medical Research Council scale that will help to identify the distribution of weakness.
Uncommonly used to assess the rate of progression and final severity of scoliosis, is the radiographic kyphotic index. In a single study it was found as a reliable guide to the age at loss of DMD ambulation and life expectancy.
| Rate of Scoliosis Evolution|| |
Different rates of evolution of the single or untreated spinal deformity have been reported. Hsu reported 0.3˚ - 4.5˚/month. Other rates were: 1˚/ month, 3.5˚/ month 0.5˚ -2.4˚/ month or per year between 11˚ - 42˚. The rate is increased during puberty. Rapid scoliosis deterioration by 90˚ in less than a year has been reported.
| Overall Strategies for Management of Postural Deformities in DMD|| |
While it is not possible to prevent the development of spinal deformity in children with neuromuscular disorders, management must be directed at trying to slow down the rate of progression and maintain spinal mobility to prevent it from becoming fixed, for as long as possible.
A successful overall management strategy requires an integrated team including pediatric neuromuscular consultant, physiotherapist, occupational therapist orthotist and orthopedic surgeon.
As the risk factors for developing postural asymmetry are known, then minimising deformity must be the goal, within the context of a growing, maturing child and while maintaining maximum possible function at home, at school and for leisure/play.
Conservative (non-operative) management
(i) Power and exercise
Weakness is the major underlying factor causing deformity and in most cases, there is limited treatment for this. Steroids in DMD have been shown to prolong ambulation and preserve function, which in some studies over time, has shown protective effects in development of scoliosis. Other drug treatments have not, as yet, proved as efficacious.
Exercise has not been proven to have any long-term protective effect against development of spinal deformity., This, however, should not discourage the use of regular exercise to maintain muscle power by preventing disuse atrophy, retain stamina and help to control contractures.
The control and management of contractures that contribute to loss of ambulation and lead to spinal asymmetry and deformity can be done through daily prolonged stretches, night splinting/orthotics, serial casting, positive positioning and surgery. The options will depend on the individual child with the more conservative treatments being those of first choice. Serial casting is preferable as a next course of action with knees and ankles being easily treated with minimal side effects. Surgery will be considered for TA tightness in combination with rehabilitation in KAFOs or for overall management efficacy.
(ii) Orthoses and splints
Studies have shown that walking in knee-ankle-foot orthoses (KAFO's) can lessen the progression of scoliosis and walking through puberty can greatly reduce the need for spinal surgery.,, Providing non-ambulant children with ischeal/gluteal weight bearing KAFO's to maintain ambulation is therefore a common part of the management of children with DMD and again, an experienced orthotist and physiotherapist are needed in the provision of KAFO's that will enable the children to maximise their walking ability. Lower limb contractures can be controlled by regular standing but it is important to ensure that the child is standing symmetrically. If the posture in standing is more asymmetrical than when the child is sitting, then the value of static standing is reduced and the standing time should be limited.
(iv) Thoracolumbar spinal orthoses (TLSO)
The use of spinal orthoses, (jackets or braces) has a role in the control of deformity and an orthotist experienced in paediatric neuromuscular disorders is an important member of the multidisciplinary team. Jackets may be used into adulthood if spinal surgery is not an option where respiratory, cardiac or nutritional problems prevail.
Management of spinal deformities with spinal orthoses is often ineffective to control deterioration [Figure - 2]. It has been reported that thoracic orthoses are only capable of controlling curvatures of less than 25o, but have little effect above this value., A TLSO is designed generally not to apply pressure to the spine or to correct deformity, but rather to support the trunk in a functional position, permitting the use of the upper extremities for purposeful activities and a degree of spinal hyperextension. A TLSO should be provided for Cobb angles greater than 20o. Patients should be advised to wear the TLSO for at least six to eight hours every day, while they are sitting. although for some as long as 23 hours per day. Spinal orthoses can be rather constrictive and potentially lower FVC.
(v) Custom made adaptive seating and sleep systems
Custom made adaptive seating is an alternative approach in the conservative management along with spinal exercises, electrical stimulation of paraspinal muscles and spinal manipulation. Custom made adaptive seating was originally designed by Gibson DA et al. to induce lumbar lordosis as a preventative measure for scoliosis. This was based on the observation that lordosis reduces spinal discs pressures and protects against the effects of lower back pain resulting from a kyphotic sitting position.,, Unaffected subjects who used backrest inclinations of 110 to 130 degrees with concomitant lumbar support were protected from lower back pain and had better electromyography recordings and lower disc pressures from their paraspinal muscles. This effect could not be reproduced in the late ambulant stage DMD boys. The speculation was that the technique used (comparison of the severity of the lateral curvature of the spine from scoliosis views following appliance of lateral deforming pressures when lying in supine, with/without a lumbar pad underneath) was not a true representation of the natural conditions as the X-rays were taken in the lying position and the effect of gravity removed.
The use of posture control cushions and seating systems is common in children with DMD. There is a little evidence that some cushions can improve pelvic obliquity and pressure problems but not scoliosis. Generally, follow-up studies of both conservative measures (TLSO and custom made adaptive seating) have shown limited effect on controlling scoliosis. Although the progression of curvatures might be delayed, progression of scoliosis cannot be prevented.,
Systems that improve posture are preferred by therapists and physicians but in some cases they may restrict function, hinder transfers and not be aesthetically pleasing. Comfort is important for a child who is sitting for virtually all of their waking day and there has often to be a compromise between posture, function and comfort. When supplying seating, the considerations for different ages and needs of children, have to be taken in context with family, school and other issues and posture may not be considered the priority.
In the child with neck and/or spine rigidity, an occasional late feature of DMD, the control of posture and maintenance of function can be conflicting but a preferred seating system is one that can be adaptable to the child's changing needs over the course of a day, with provision for tilt-in space.
Although a child may be unable to change position in bed, the position a child adopts will be influenced by contractures rather than weakness as once lying, the affect of gravity is eliminated and spinal posture is no longer compromised. The use of sleep systems to control posture in older boys with no bed mobility has not been proven but such systems are being used to provide increased comfort in bed in the presence of painful contractures or disturbed sleep.
Surgical intervention is obviously the major method of management of spinal deformity in DMD. It should be considered a positive part of the treatment options available to these children and not as a failure of other management regimes. Early prophylactic spinal instrumentation has been recommended in a number of centers in Europe and the States as the treatment of choice, soon after ambulation is lost, even before significant scoliosis develops.,,,, The benefits of earlier than later scoliosis surgery are thought to include better correction of the spinal deformity and pelvic obliquity with secondary improved sitting in the wheelchair and respiratory function and prolongation of life expectancy. Furthermore the advantage of this approach is that the chances of a severe respiratory impairment at this stage are low; and the procedure in patients with mild curvatures is safer and technically easier.,,, Studies have also claimed that scoliosis surgery improves quality of life of the patient and parents/caregivers by improving sitting comfort and patient's appearance.,,,
Indications for surgical management of scoliosis include progressive deformity, compromise of sitting balance or of cardio-respiratory function and refractory pain. The primary goal of surgery is the prevention of curvature progression by bone fusion. The secondary goals include curve correction and trunk balance optimization. The decision to perform surgery lies with the multidisciplinary team but also should respect the wishes of the patient and family. Improvement of major curves by 50% (up to 70% in experienced hands) with posterior segmental instrumentation is often required. DMD boys almost exclusively have posterior segmental instrumentation with or without the fusion extended to the sacropelvis, which is a single stage procedure and has the advantage of exposing them only once to general anesthesia.
The Harrington instrumentation has now been abandoned as it required prolonged immobilisation in the postoperative period and is associated with a high risk of severe cardiopulmonary complications. The Luque fusion was widely used between 1970-1980, but follow-up studies have shown loss of trunk balance, severe compensatory cervical curvature and rod breakage. In the recent years, newer hardware such as the universal spinal system and the Duchenne instrumentation technique, a new technique that increases stiffness in the frontal plane with a rod but allows flexibility in the sagittal plane, have shown some preliminary and satisfactory results [Figure - 2]. The decision to provide a soft TLSO for up to six months whilst sitting and following surgery lies with the orthopedic surgeon judging the risks for failure of the fusion, especially in those older DMD boys with very osteoporotic spines.
| Summary|| |
Of all the postural deformities that are found in DMD, scoliosis has generated the most interest due to the many problems that it causes in the overall management of the child.
Scoliosis can become apparent while the boys are still ambulant so that monitoring and management needs to be considered at this stage, rather than after the boys have lost the ability to walk.
Prolongation of ambulation is an important means of trying to control the onset and slow the progression of deformity and therefore a priority of therapy.
Significant scoliosis (>50°) in DMD, while not life threatening, causes severe difficulties in function, seating, posture and quality of life and can compromise cardio-respiratory function.
In the relatively sizeable number of boys who do not progress to significant scoliosis, conservative management is a viable alternative to surgery and therefore, the current practice of surgical stabilization of the spine as soon as the boys lose ambulation needs to be further modified.
As scoliosis is treatable, a good multi-disciplinary team approach is needed to ensure the most appropriate care for these boys. In those cases where cardiac and respiratory problems prevent surgical intervention, there are non-operative strategies that can and should be followed.
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[Figure - 1], [Figure - 2]
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