Historical Background

The first documentation of muscular dystrophy was provided by Meryon in 1852 when he described a family in which progressive atrophy and weakness of the muscles developed in four boys during childhood. Even though autopsy revealed degeneration of muscle, Meryon still confused the condition with progressive neurologic atrophy.

In 1868 Duchenne characterized the entity as a muscle disease of childhood or adolescence, most commonly seen in boys, that is typified by progressive weakness of the muscles, beginning in the lower limbs and spreading to the trunk and arms; enlargement (pseudohypertrophy) of the weakened muscles; hyperplasia of interstitial connective tissue; and an increase in fat cells in the affected muscles. Duchenne also noted that the changes occurred only in the muscles; no pathologic changes were evident in the nervous system.

In 1879 Gowers described the classic clinical sign of a patient “climbing up the legs” ( Fig. 39-1 ) and later delineated another form of muscular dystrophy that affected primarily the distal musculature. Limb-girdle, facioscapulohumeral, and myotonic dystrophies were all described in the late 1800s.

Gowers sign: a patient with hip extensor weakness “walks” his hands up his legs to raise his trunk to an upright position.

Classification

The classification of progressive muscular dystrophy that is most relevant from clinical and genetic standpoints is the system proposed by Walton ( Box 39-1 ).

Etiology

Significant advances in molecular genetic research have helped establish the cause of the primary progressive muscular dystrophies. The gene responsible for Duchenne muscular dystrophy is located on the Xp21 region of the X chromosome and spans 2 million base pairs. One third of all cases of Duchenne muscular dystrophy occur as a result of spontaneous mutation. The Xp21 region of the X chromosome encodes for dystrophin, a 400-kilodalton protein present in skeletal, smooth, and cardiac muscle and in the brain. Dystrophin is critical to the stability of the cell membrane cytoskeleton. Boys with Duchenne muscular dystrophy have mutations that disrupt the translational reading frame or the promoter region of DNA, thereby resulting in a lack of dystrophin.

Becker muscular dystrophy, which is a more benign form, occurs in males and is transmitted in an X-linked recessive manner, similar to Duchenne muscular dystrophy. The gene responsible for Becker muscular dystrophy is the same gene that encodes dystrophin. However, boys with Becker muscular dystrophy have in-frame mutations that result in the production of low-molecular-weight dystrophin or lower amounts of normal-molecular-weight dystrophin. Genetic testing has revealed that 60% to 80% of children with Duchenne or Becker muscular dystrophy have demonstrable mutations or deletions of the dystrophin gene.

Dystrophin is not abnormal in other forms of muscular dystrophy. The gene locus for Emery-Dreifuss muscular dystrophy is located on the long arm of the X chromosome at Xq28. This gene encodes for emerin, a protein that is present in the nuclear membranes of skeletal and cardiac muscle. Even though dystrophin is normal in Emery-Dreifuss syndrome, emerin is absent.

The gene associated with myotonic dystrophy is located on chromosome 19. This disease is epitomized by expansion of a sequence of three nucleotides: cytosine, thymine, and guanine. The number of repeats of this trinucleotide (CTG) increases as the gene is passed to subsequent generations, and the clinical manifestations of myotonic dystrophy become more severe with an increasing number of repeats. Thus, anticipation is characteristic of the phenotype of the disease, with children of affected mothers exhibiting greater severity.

The locus for facioscapulohumeral dystrophy is located on chromosome 4 at the 4q35 region.

Pathology

The pathologic changes in muscles are similar in all forms of muscular dystrophy. Yet each disease is a separate entity based on its genetic transmission, age at onset, clinical course, distribution of involvement, and results of molecular genetic testing.

The most important histologic feature of muscular dystrophy is loss of muscle fibers, which is caused by segmental necrosis and eventual fragmentation of the fibers ( Fig. 39-2 ). The size of individual muscle fibers displays marked variation, with fibers ranging from 10 to 230 µm. In addition, the arrangement of large and small fibers is random. Enlarged, “hypercontracted” fibers may contain abnormally increased amounts of calcium. The muscle fibers retract from their endomysial sheaths, with forking or branching (“splitting”) of the fibers, which some researchers hypothesize may represent an attempt at regeneration. Necrosis of the muscle fibers is accompanied by phagocytosis and histiocytic proliferation in the areas of necrosis. The sarcolemmic nuclei are enlarged in regenerating fibers. Interstitial connective tissue is increased, with substantial infiltration of adipose tissue.

Histologic changes in progressive muscular dystrophy. A, Transverse section taken from the vastus lateralis muscle of a 7-year-old boy with early-stage disease (hematoxylin-eosin, ×400). Note the substantial variation in the size of individual muscle fibers and retraction of the muscle fibers from the endomysial sheaths. B, Longitudinal section from an enlarged gastrocnemius muscle (hematoxylin-eosin, ×250). Note the accumulation of adipose tissue and reduction in the number of muscle fibers.

The histopathologic findings vary with disease severity. Fiber necrosis, splitting, phagocytosis, and fatty replacement are most pronounced in Duchenne muscular dystrophy. In later-onset dystrophies (e.g., distal muscular dystrophy), fiber size variation, fibrosis, and central nucleation are more common. In myotonic dystrophy, a unique finding of rows of central nuclei and annulets is sometimes seen. Histochemistry often reveals a predominance of small type I fibers.

Analysis of dystrophin in muscle biopsy specimens has become an integral part of the evaluation and diagnosis of muscular dystrophy. The content of dystrophin in muscle biopsy specimens can be determined by immunofluorescent staining with antibodies against parts of the dystrophin molecule. Commonly, a Western blot of a homogenate of muscle tissue is examined for the presence, amount, and molecular weight of dystrophin. An enzyme-linked immunosorbent assay is also used to quantify the amount of dystrophin.

Because dystrophin is absent in the vast majority of boys with Duchenne muscular dystrophy, a definitive diagnosis can be made when no dystrophin is present. In patients with Becker muscular dystrophy, dystrophin is altered in size, amount, or both. The amount of dystrophin present has been correlated with the clinical phenotype; specifically, the age at which the patient loses the ability to walk independently. The presence of normal dystrophin rules out Duchenne or Becker muscular dystrophy while raising the possibility of limb-girdle dystrophy or one of the other less common forms.

Analysis of dystrophin has also been used in genetic testing to help distinguish potential carriers of Duchenne and Becker muscular dystrophy. In some women who are carriers, dystrophin immunostaining has been documented as abnormal.

Laboratory Findings

The level of creatine kinase (CK) in blood is elevated in patients with muscle disease and is not specific to the muscular dystrophies. As the muscle cell degenerates, CK is released and serum CK levels can be elevated 20 to 200 times higher than normal. Serum CK levels are generally higher in children with Duchenne muscular dystrophy than in those with the Becker type; however, the two diseases do have some overlap, and a distinction cannot be made simply by measuring serum CK levels. In Duchenne muscular dystrophy, the CK level is elevated in the presymptomatic phase of the disease, falls as the disease worsens, and approaches nearly normal levels in end-stage disease, when almost all skeletal muscle has been replaced. In some cases, female carriers of Duchenne muscular dystrophy have elevated CK levels; however, genetic counseling based only on this finding is ill advised.

Aldolase is another enzyme that is elevated in children with muscular dystrophy. Its course is similar to that of CK: serum levels are highest in the early phase of the disease, decline as the disease progresses, and approach normal levels in end-stage disease. Serum glutamic-oxaloacetic transaminase (also known as aspartate transaminase) and lactate dehydrogenase may also be elevated, but abnormalities in these enzyme levels are nonspecific for muscle disease.

Electromyography and Nerve Conduction Velocity

An electromyogram (EMG) can help differentiate myopathic and neuropathic processes. The EMG recording in patients with muscular dystrophies is distinguished by a pattern of low-amplitude, short-duration, polyphasic motor unit potentials. Nerve conduction velocity is normal in patients with muscular dystrophies. It should be noted that nerve conduction velocity increases with age as myelination occurs in young children. Normal adult values (i.e., 50 m/sec) are usually seen by 6 years of age.

Etiology and Diagnosis

Duchenne muscular dystrophy, the most common form of muscular dystrophy, occurs in 1 in 3500 boys. It is transmitted in an X-linked recessive fashion whereby all affected persons are male; females are carriers of the gene. On very rare occasion, females with Turner syndrome exhibit the disease because of their XO genotype. Other rare chromosomal events, such as translocations, can also result in clinically affected girls.

The first responsibility of the orthopaedic surgeon is to establish the diagnosis. It may be difficult for an orthopaedist to diagnose Duchenne muscular dystrophy at a child’s initial visit. Duchenne muscular dystrophy and polymyositis have some similarities, but certain features of the two diseases can help establish the correct diagnosis ( Table 39-2 ). It is extremely important to diagnose Duchenne muscular dystrophy as soon as possible because a delay may lead to further pregnancies in a carrier and the birth of affected children in an uninformed family.

Molecular genetic testing has eliminated the need for muscle biopsy in many patients, but in some cases, muscle biopsy is still necessary. The vastus lateralis is the usual site for biopsy. It is important to excise enough muscle so that dystrophin analysis can be performed in addition to light microscopy. The muscle sample must not be traumatized; careful surgical technique is used so that the specimen is not stretched or crushed, and handling of the specimen should be minimized. Preoperative consultation with the pathologist is essential so that the tissue is delivered promptly and not placed in an inappropriate solution. Fresh tissue for cryostat section is necessary for an accurate diagnosis.

Debate exists whether open biopsy is preferable to needle biopsy. Special clamps to maintain muscle length have fallen out of favor as more specific testing of the tissue has become available. Mubarak and associates found needle biopsy to be diagnostic in most patients; in addition, it required less anesthetic and left minimal scarring.

In utero fetal muscle biopsy has been used to establish the diagnosis of Duchenne muscular dystrophy following the diagnosis of one previously affected male in whom no gene deletion could be identified.

Clinical Features

The disease is usually manifested in children between 3 and 6 years of age. The onset of weakness is insidious. Affected boys may achieve motor milestones at somewhat older ages, and a slight delay in walking may be noted. Although the disease is not usually evident until after 3 years of age, the Gowers sign may be present as early as 15 months.

Initial signs can range from a waddling gait to difficulty climbing stairs to marked muscle weakness and clumsiness. In the early stages of the disease, boys may have notable toe-walking during ambulation. Duchenne muscular dystrophy should be considered in any young boy with ankle equinus and a normal birth history.

The muscle weakness develops symmetrically. Weakness is noted initially in the proximal musculature, with the hip extensors often being the first muscles affected. Lower extremity involvement usually precedes upper extremity disease by 3 to 5 years. As the disease progresses, contractures occur predictably in certain muscle groups while sparing others. Weakness coupled with contractures leads to deviations in gait.

Ankle equinus is frequently the first sign of Duchenne muscular dystrophy. Contracture at the ankle leads to toe-walking and a tendency to hyperextend the knees. Knee hyperextension locks the posterior capsule of the knee, thereby augmenting the weak quadriceps and preventing buckling of the knee. Hip extensor weakness leads to anterior tilt of the pelvis, which results in hyperlordosis of the lumbar spine during gait. The body realigns itself to take advantage of the stability offered by the hip and knee joints. The hip becomes more stable as the ground reaction force comes to lie posterior to the joint, whereas the knee gains stability when the ground reaction force is located anterior to the joint. Thus, the patient partially overcomes weakness in the quadriceps by locking the knee joint via the posterior capsule in full extension ( Fig. 39-3 ).

Typical posture of ambulatory patients with Duchenne muscular dystrophy. To compensate for a weak quadriceps and prevent buckling of the hip, the patient locks the knee joint in full extension. Stability is increased when the ground reaction force is posterior to the hip and anterior to the knee.

Muscle weakness is also present in the gluteal muscles early in the disease and leads to the development of a Trendelenburg gait. The stance-phase limb abductors are not strong enough to hold the pelvis up as the contralateral limb enters the swing phase. As a result, the child brings the weight of the upper part of the body over the stance limb via trunk sway to augment abductor strength ( Fig. 39-4 ). Such compensation results in a waddling appearance as the trunk sways back and forth over each limb during the stance phase. The base of the gait also widens in an attempt to improve stability and avoid falling. Subsequent contractures of the iliotibial band cause further widening of the base of the gait.

Trendelenburg gait. The stance-phase limb abductors are not strong enough to hold the pelvis up as the contralateral limb enters the swing phase. As a result, the patient brings the weight of the upper part of the body over the stance limb via trunk sway to augment abductor strength. When viewing the patient from behind, the clinician can see a drop in the hemipelvis on the side of the non–weight-bearing limb, which indicates weakness of the gluteal muscles.

As the disease progresses and muscle weakness becomes more pronounced, the stance phase of gait is prolonged and the swing phase shortens. The child’s cadence decreases as it becomes more difficult to take steps. The amount of time spent in double-limb support increases as the patient experiences more difficulty standing on a single limb.

Behavioral studies have shown that patients with Du­­chenne muscular dystrophy have cognitive impairment with lower than normal intelligence. Abnormal central nervous system architecture and loss of neurons, as well as electroencephalographic abnormalities, have been documented.

Physical Examination

Findings on physical examination vary depending on the stage of the disease. Initially, the only discernible contracture is in the gastrocsoleus. The muscle belly of the gastrocsoleus is usually enlarged (termed pseudohypertrophy ) ( Fig. 39-5 ). Enlargement results from fibrofatty replacement of muscle fibers, which is most notable in the gastrocsoleus muscle and feels like hard rubber. The patient is unable to fully dorsiflex the ankles.

In patients with Duchenne muscular dystrophy, the muscle belly of the gastrocsoleus is usually enlarged (termed pseudohypertrophy ).

Careful, complete muscle testing reveals weakness in the proximal musculature of the lower extremities. Hip abductor weakness can be demonstrated by having the patient attempt to stand on one leg. When viewing the individual from behind during this maneuver, the clinician can see a drop in the hemipelvis on the side of the non–weight-bearing limb (Trendelenburg sign), which indicates weakness of the gluteal muscles (see Fig. 39-4 ). If the examiner is not sure whether the patient has muscular weakness, the child should be asked to sit on the floor of the examining room and then rise quickly to a standing position without assistance. Difficulty performing such a maneuver leads the patient to use the arms to push up on the lower extremities to assist in hip and knee extension while standing up. A boy with Duchenne muscular dystrophy “walks” his hands up his legs to raise his trunk to an upright position (Gowers sign; see Fig. 39-1 ). A second clinical sign is the Meryon sign ; when the examiner lifts the child by the chest, the child’s arms abduct and slide through the embrace of the examiner’s arms because of shoulder girdle weakness.

As the severity of the disease increases, contractures occur throughout the lower extremities. Abduction contractures of the hips develop because of tightness of the iliotibial bands. Such contractures can be demonstrated with the Ober test, which is performed with the child lying on his side. The leg is abducted, and the hip is extended and brought into adduction in the extended position. Abduction contractures in children with Duchenne muscular dystrophy usually exceed 30 degrees. Ankle equinus becomes more pronounced, and varus of the hindfoot appears as the posterior tibialis muscle becomes contracted ( Fig. 39-6 ). Knee and hip flexion contractures develop as the child loses the ability to walk and starts using a wheelchair more often. When measuring hip flexion contractures, the hip must be adducted because the abduction contracture may mask the severity of the flexion contracture.

Equinovarus contracture of the foot in a nonambulatory patient with Duchenne muscular dystrophy.

Scoliosis appears in late childhood or early adolescence. It is mild at first but progresses relentlessly in most patients. The curve is frequently accompanied by an increase in lumbar kyphosis after the patient starts using a wheelchair. While in the wheelchair the patient’s trunk lists to the side, and sitting without the assistance of the upper extremities becomes progressively more difficult ( Fig. 39-7 ).

A and C, Thirteen-year-old boy with Duchenne muscular dystrophy and scoliosis. Clinical photographs and radiograph ( B ) show listing to the right and waist asymmetry.

In the upper extremities, contractures eventually develop in the elbow flexors. The patient loses the ability to abduct the shoulders. Hand function is not usually affected until late in the course of the disease. Boutonnière and swan-neck deformities develop in the fingers but rarely interfere with the patient’s ability to use a motorized wheelchair.

Medical Concerns

As the myopathy worsens, the pulmonary and cardiac systems are affected. The first sign of pulmonary insufficiency is a reduction in expiratory muscle strength. With advancing age, pulmonary function steady declines. Cardiac changes include right ventricular hypertrophy, sinus tachycardia, mitral valve prolapse, and diminution of the QRS wave. A policy statement has been published that provides recommendations for cardiac evaluation in boys with Duchenne muscular dystrophy.

Treatment

No definitive treatment is available for Duchenne muscular dystrophy, and the disease is inevitably fatal. Coordinated multidisciplinary care, including orthopaedic surgery, neurology, pulmonology, cardiology, nutrition, and physical therapy, focuses on maximizing the child’s function. The primary goal of early treatment is to help the patient maintain functional ambulation as long as possible. When the patient becomes nonambulatory, management is directed toward treating scoliosis when it develops and addressing the problems associated with nonambulation as they occur.

Lower Limb Surgery

As muscle weakness worsens and contractures develop, walking becomes more labored and unstable, which results in many falls. Soft tissue surgery can improve gait and prolong the child’s ability to walk.

Timing of Surgery.

The timing of this surgery is controversial. Surgery for lower limb contractures in patients with Duchenne muscular dystrophy has been classified by Shapiro and Specht ( Box 39-2 ).

Box 39-2

Shapiro and Specht Classification of Contracture Surgery of the Lower Limbs in Patients With Duchenne Muscular Dystrophy

• •
  

  Early-extensive ambulatory approach: release at the hip, hamstrings, and heel cords and posterior tibialis transfer before the onset of significant contractures

  
  
• •
  

  Moderate ambulatory approach: rarely includes hip abductor releases, with surgery being performed while the child is still able to walk but is experiencing increasing difficulty

  
  
• •
  

  Minimum ambulatory approach: correction of only equinus contractures

  
  
• •
  

  Rehabilitative approach: operative intervention after the child ceases walking but surgery pursued with the goal of reestablishing ambulation

  
  
• •
  

  Palliative approach: surgical correction of equinovarus after full-time wheelchair use has begun, with the goals of pain relief and improved ability to wear shoes

From Shapiro R, Specht L: The diagnosis and orthopaedic treatment of inherited muscular diseases of childhood, J Bone Joint Surg Am 75:439, 1993.

The strongest proponents of early surgery (i.e., performed between 4 and 6 years of age, before contractures develop) believe that the quality of ambulation without braces is enhanced and the child’s need for a wheelchair is delayed. However, a randomized trial by Manzur and associates reported no beneficial effect on strength or function at 12 to 37 months of follow-up. Smith and colleagues found that patients who underwent surgery at a later age (>10 years) maintained their ability to walk an average of 2 years longer than did those who did not undergo surgery, and they were able to stand almost a year after they lost the ability to walk. With the advent of steroid therapy, muscle strength is preserved for longer periods and therefore early surgery has fallen out of favor.

It is difficult to compare the results of the various studies of lower extremity surgery in patients with Duchenne muscular dystrophy. On average, such operations prolong walking time 2 to 3 years, but the age at which children who are not treated with steroids lose ambulation varies from 7 to 16 years (whereas with Becker muscular dystrophy, loss of ambulation may occur after 16 years). It may be that the children who were able to walk for the longest time after surgery had milder disease to start with—that is, they may have had some dystrophin present—and thus severe Becker muscular dystrophy should have been diagnosed instead of Duchenne muscular dystrophy. A more accurate diagnosis may be achieved through dystrophin analysis.

It is agreed that if the child has already lost the ability to walk, the operation must be done in a timely manner if ambulation is to be reestablished. Once the patient becomes nonambulatory, muscle strength is lost quickly. A small window of opportunity—3 to 6 months—is available after the child stops walking when surgery can make ambulation possible again in rare instances. Operations after this time do not help the patient walk; however, foot surgery in a nonambulatory patient can make wearing shoes possible.

Factors other than age play an important role in determining the success of tendon surgery in patients with Duchenne muscular dystrophy. The child’s motivation to retain walking ability and to cooperate with postoperative bracing and physical therapy cannot be overlooked. Depression, which is common in patients in the surgical age group, can interfere with postoperative care and home exercise programs. The parents’ motivation must also be taken into account. Another factor is obesity, which is common in boys with Duchenne muscular dystrophy and is a poor prognostic sign for regaining the ability to ambulate after surgery.

Techniques.

Equinus is managed by percutaneously lengthening the Achilles tendon. Varus is treated by surgery on the posterior tibialis tendon. Some authors recommend tenotomy or lengthening of the posterior tibialis, but most advocate anterior transfer of the tendon through the interosseous membrane to the center of the dorsum of the foot ( Plate 39-1 ). This approach not only corrects varus of the hindfoot but also augments dorsiflexion of the ankle, which leads to less frequent recurrence of deformity.

Scher and Mubarak reported that patients who underwent multilevel surgery to prolong ambulation did not believe that the results were worth the surgery, bracing, and therapy, and families stated that they would not choose to do it again. However, satisfaction with the status of the feet after Achilles tendon lengthening and posterior tibialis tendon transfer was high, and patients who underwent posterior tibialis tendon transfer were more likely to be able to wear whatever shoes they liked. The authors recommended that Achilles lengthening, posterior tibialis tendon transfer, and toe flexor tenotomies be offered to all boys with Duchenne muscular dystrophy. It should be noted that their surgical technique of posterior tibialis tendon transfer was novel in that the tendon was divided longitudinally proximal to the fibrocartilaginous insertion and extended in length by doubling back the divided tendon from the musculotendinous junction. The site of transfer chosen was the base of the second metatarsal, which necessitated a longer tendon for transfer.

Another study in which patients who underwent Achilles tendon lengthening and posterior tibial tendon transfer were compared with patients who had no foot surgery found no differences between the two in terms of the ability to wear shoes, foot pain, and patient satisfaction, although greater degrees of equinus were noted in the nonsurgical group. Based on the different results of these two studies, it can be concluded that foot surgery consisting of tendon lengthening and transfer can benefit some boys with Duchenne muscular dystrophy, but many patients remain asymptomatic despite the presence of contractures. The decision to perform surgery should be made on an individualized basis in consultation with the family.

Knee surgery consists of lengthening or tenotomy of the hamstrings. Abduction contractures of the hips are treated by resecting the iliotibial band through a proximal Ober release, with or without a distal Yount resection, or via fasciectomy of the iliotibial band. Hip flexion contractures can be improved by release of the sartorius, rectus femoris, and tensor fasciae latae.

Postoperative care should include early weight bearing and ambulation, with the child placed in a standing position on the first postoperative day ( Fig. 39-8 ). Because every day of bed rest adds to the child’s weakness, effort must be made to mobilize the child immediately. Casting should be limited to below the hips so that the child can take steps with the cast on. Short-leg casts are preferable when immobilization of the knees is not crucial. When surgery is performed on children 10 years or older, bracing with lightweight knee-ankle-foot orthoses (KAFOs) is necessary to prolong ambulation ( Fig. 39-9 ). The need for bracing should be anticipated before surgery so that the orthoses are ready immediately afterward. Locked-knee KAFOs are needed postoperatively for ambulation. Many children have a well-founded fear of falling in their KAFOs because upper extremity weakness prevents them from breaking the fall. In children with sufficient arm strength, a walker may be of assistance.

Early physical therapy in long-leg casts immediately after soft tissue releases in a boy with Duchenne muscular dystrophy.

Postoperative lightweight knee-ankle-foot orthoses used by a patient with Duchenne muscular dystrophy. A, Braces can be used for standing and walking. B, When the patient is using a wheelchair, the knees of the braces are unlocked.

Spinal Surgery

Scoliosis develops in nearly all children with Duchenne muscular dystrophy who are not treated medically, and it becomes increasingly pronounced after the child is nonambulatory. Historically, scoliosis developed in one in four children before becoming nonambulatory. Currently, the use of corticosteroids in boys with Duchenne muscular dystrophy is reducing the incidence and delaying the development of scoliosis. Curves are long and sweeping and are associated with pelvic obliquity. The pattern of the deformity does not resemble that seen with idiopathic scoliosis; instead, it is neuromuscular in appearance ( Fig. 39-10 ). Thoracolumbar kyphosis is commonly present, but lumbar hyperlordosis may be seen in some boys. If left untreated, many curves progress beyond 90 degrees. Such curves make it difficult for the child to sit comfortably and lead to skin breakdown because the muscle weakness interferes with the patient’s ability to relieve pressure during sitting.

Long sweeping thoracolumbar curve in a patient with Duchenne muscular dystrophy.

Timing of Surgery and Indications.

The appropriate treatment of scoliosis is surgical intervention. Bracing has been tried but is not recommended in this patient population for several reasons. First, the goal of bracing is to prevent progression of the curvature during the time of spinal growth, yet progression occurs in these patients despite bracing. Second, the risk for progression is prolonged because of the patient’s profound muscle weakness. Third, bracing can impede full respiratory effort. Pulmonary function is already precarious in these children, with forced vital capacity (FVC) decreasing by approximately 4% each year and by another 4% for each 10 degrees of thoracic scoliosis. Because curve progression is the rule rather than the exception and because pulmonary function deteriorates rapidly when the patient is no longer able to walk, it is preferable to perform surgery earlier, when the child’s respiratory status is functionally better. Delaying surgery because of brace treatment may make any subsequent operation less safe as a result of the presence of pulmonary disease.

A lesser known reason for early stabilization of scoliosis is to prevent any subluxation or dislocation of the hip that may result from the pelvic obliquity. Hip abnormalities, though rare, have a deleterious effect on balanced seating of nonambulatory boys with muscular dystrophy.

The indications for spinal fusion to correct scoliosis in patients with Duchenne muscular dystrophy are different from those for idiopathic scoliosis. Surgery should be performed once a curve reaches 30 degrees and the patient is nonambulatory because curve progression is guaranteed and pulmonary function will deteriorate as the curve worsens. Mubarak and associates recommended surgery for curves greater than 20 degrees in children whose FVC is greater than 40% of normal. Surgery is best tolerated before the patient’s FVC is less than 35% of age-matched normal values. Although surgery has been performed successfully in children with more advanced pulmonary disease, the risk for prolonged mechanical ventilation and postoperative pneumonia increases. Use of noninvasive mask ventilation such as bilevel positive airway pressure (BIPAP) has improved postoperative outcomes in patients with poor preoperative pulmonary function (i.e., FVC <30%). Preoperative planning must include cardiac evaluation and pulmonary function tests. If the child’s projected life span is less than 2 years, surgery may be contraindicated.

Techniques.

Surgery consists of posterior spinal fusion with instrumentation. Luque instrumentation with sublaminar wires provides segmental fixation at each vertebra. Rigid cross-linking of the rods is essential to maintain correction. Use of a unit rod has also been recommended for posterior spinal fusion in patients with Duchenne muscular dystrophy ( Fig. 39-11 ). Good correction of scoliosis and pelvic obliquity with segmental fixation via hook–screw constructs has also been reported. Posterior spinal fusion with segmental pedicle screw fixation is currently favored by many surgeons because of improved curve correction and reduced blood loss in comparison to sublaminar wires ( Fig 39-12 ).

Posterior spinal fusion with unit rod instrumentation for Duchenne muscular dystrophy.

A and B, Posterior fusion from T2 to the sacrum using pedicle screw segmental fixation with iliac screws in a boy with Duchenne muscular dystrophy.

Debate continues about the need to extend the fusion to the pelvis. Mubarak and associates reported that for mild curves without preexisting pelvic obliquity, fusion to L5 was sufficient. More recently, Sengupta and co-workers found that with smaller curves and no preoperative pelvic obliquity, fixation to L5 with lumbar pedicle screws and thoracic sublaminar wires prevented pelvic obliquity at a 3.5-year follow-up. Most recently, all pedicle screw constructs to L5 have been shown to maintain correction of severe scoliosis with pelvic obliquity as long as L5 tilt measured less than 15 degrees preoperatively. Alman and Kim are proponents of fusion to the pelvis in boys with Duchenne muscular dystrophy. In a review of 38 patients with the pelvis fused to L5, worsening pelvic obliquity occurred in 10 patients, 2 of whom required further spinal surgery.

In clinical practice, most patients have preexisting pelvic obliquity at the time of treatment of the spinal curvature. Because one of the primary goals of the operation is to ensure a level pelvis for comfortable seating, most surgeons continue to fuse to the pelvis with the Galveston or Dunn-McCarthy technique or iliac screws ( Figs. 39-13 and 39-14 ). Marchesi and associates described the use of sacral screws at S1 in patients with Duchenne muscular dystrophy rather than Galveston rods between the tables of the ilium. Regardless of the particular technique used, caudal fixation is recommended to control pelvic obliquity.

Preoperative ( A ) and postoperative ( B and C ) radiographs of posterior spinal fusion with Luque-Galveston instrumentation in a patient with Duchenne muscular dystrophy.

A, Anteroposterior radiograph of the spine of an 11-year-old boy with Duchenne muscular dystrophy and 30-degree scoliosis. B and C, Posterior spinal fusion via hybrid fixation, including hooks, pedicle screws, and Dunn-McCarthy sacral fixation, was performed.

Results and Complications.

The effect of spinal fusion and correction of scoliosis on pulmonary function has been studied by a number of investigators. Most authors have found no difference in the rate of pulmonary deterioration or long-term survival between patients who underwent spinal fusion and those who did not, although all agree that surgery improves sitting. Conversely, Velasco and colleagues found that the rate of decline in pulmonary function was half the annual preoperative rate of decline in a group of 56 patients following posterior spinal fusion. Additionally, an average perioperative decrease in pulmonary function of 1% has been reported, which should be considered in the preoperative assessment of the patient. Galasko and associates, on the other hand, found that children whose scoliosis was stabilized maintained better pulmonary function and lived longer.

The complication rate of spinal surgery in patients with Duchenne muscular dystrophy is a concern. Major complications occurred in 27% in one study. During spinal fusion, loss of blood can be substantial. Although the results of laboratory analysis of platelet function are normal, bleeding times may be increased, and blood vessel reactivity is impaired. Platelet adhesion has also been found to be deficient in boys with Duchenne muscular dystrophy. Therefore, one should be prepared for the transfusion of several units of blood. Intravenous administration of an antifibrinolytic medication such as tranexamic acid has been shown to decrease blood loss in this patient group. Postoperative infection is not uncommon, and instrumentation failure can occur. Medical complications, such as pneumonia, also occur more frequently in this patient population. Miller and Hoffman noted pulmonary complications in 17% of 183 patients who underwent surgery. Cardiac complications have been reported during anesthesia and in the postoperative period. Sudden death can occur on rare occasion in these children during the perioperative period.

Studies have shown that the families of children with Duchenne muscular dystrophy believe that the patients’ quality of life is enhanced by spinal fusion surgery. Without surgery, scoliosis interferes with comfortable sitting in a wheelchair, thereby deterring children from getting out into the community and forcing them into their beds during the terminal phase of the disease. One substantial functional change noted by parents is that their children can no longer feed themselves after spinal fusion surgery because the spine can no longer collapse and enable the head to be lowered to the level of the food tray. Postoperative malnutrition has been documented in some of these children. Families should be counseled about the serious risks associated with this surgery and the consequences if the surgery is not performed. A validated outcome tool has been developed to assess symptoms and functional abilities important to children with scoliosis and muscular dystrophy and their parents.

Steroid and Other Drug Therapy

The efficacy of oral steroids in slowing the progression of Duchenne muscular dystrophy has been tested in clinical trials, the results of which strongly support their use. Steroids are potent antiinflammatories and can help stabilize the cell membrane. They act by decreasing the inflammatory response to the disrupted muscle cell. Prednisone has been shown to delay the loss of ambulation in patients with Duchenne muscular dystrophy for 2 to 5 years. Further investigations have been undertaken to evaluate pulsed treatments and alternate-day dosing to preserve the efficacy of steroids but decrease their potential side effects. Convincing work has come from Toronto and Quebec, where protocols using the steroid deflazacort have produced prolonged ambulation and a striking decrease in the incidence of scoliosis. High-dose daily deflazacort has been shown to maintain strength, preserve pulmonary function, and prevent deformity better than lower-dose regimens. Seventy-seven percent of boys maintained on a protocol of deflazacort, vitamin D, and calcium remained able to walk at 15 years of age. Scoliosis was present in only 16% of the treated boys as compared with 90% of controls. A 2007 study of corticosteroid use found that boys who were treated daily with steroids walked 3.3 years longer than did untreated boys and had a 31% incidence of scoliosis versus 91% in the untreated cohort. Pulmonary function is also better preserved in Duchenne patients treated with both deflazacort and prednisone than in untreated controls as evidenced by greater FVC (88% versus 39% of predicted FVC) and a delay in the use of noninvasive ventilation. The improved health in patients treated with steroids versus untreated controls is maintained at longer-term follow-up (age of 18 years).

Steroid therapy is associated with significant side effects, including weight gain, cataracts, and osteopenia. Weight gain is variable in boys taking steroids, with one study finding no gain in weight because of an increased activity level in treated patients. Bone mineral density, as measured by dual-energy x-ray absorptiometry, is decreased in all boys with Duchenne muscular dystrophy and is even more diminished in those taking steroids. Osteopenia may result in vertebral compression fractures and long-bone fractures ( Fig. 39-15 ). Bisphosphonates have been found to be beneficial in a small series when given to counteract the osteopenic effects of steroids.

Lateral spine radiograph of a 16-year-old boy receiving steroids long term as treatment of Duchenne muscular dystrophy. Note the severe osteopenia and lumbar compression fractures.

The current literature on the use of steroids for Du­­chenne muscular dystrophy can be summarized as follows: ambulation can be prolonged secondary to maintenance of muscle strength, scoliosis can be at least delayed and possibly prevented ( Fig. 39-16 ), and side effects are present but manageable. Therefore, steroids should be offered to boys in whom Duchenne muscular dystrophy is diagnosed to preserve strength as long as possible.

A and B, Anteroposterior and lateral radiographs of a 14-year-old boy with scoliosis who was being treated long-term with steroid therapy. Though rare, scoliosis may occur and is complicated by obesity and osteopenia. C and D, Same boy following posterior spinal fusion with segmental fixation.

Gentamicin is an effective treatment in a small subset of boys with Duchenne muscular dystrophy caused by a stop codon within the dystrophin gene. Aminoglycosides can allow readthrough of some stop codons.

Prognosis

Until recently, death from respiratory failure usually occurred by the late teens to early 20s. The age when vital capacity falls below 1 L has been shown to predict mortality, with a 5-year survival rate of only 8%. Cardiac involvement is the cause of death in approximately 20% of males with Duchenne muscular dystrophy. With current medical treatment, improved respiratory therapy, and the availability of home mechanical ventilation, life expectancy is increasing for patients. Median survival to the age of 30 was reported in a group of patients who underwent spinal fusion and were subsequently ventilated when pulmonary function declined over time. New problems are surfacing with survival into adulthood. In a survey of adults 18 to 42 years of age with Duchenne muscular dystrophy, musculoskeletal pain was a complaint in 40%.

Etiology and Diagnosis

Becker muscular dystrophy is inherited in an X-linked recessive pattern. The genetic cause of the disease is a mutation at the Xp21 locus on the X chromosome, the same location as the mutation that causes Duchenne muscular dystrophy. Genetic testing can identify the mutation in many patients.

Because this locus encodes for dystrophin, the protein is abnormal in patients with Becker muscular dystrophy as well. The site of deletion in the Xp21 locus determines the amount or size of dystrophin (i.e., an in-frame deletion causes Becker muscular dystrophy, whereas an out-of-frame deletion causes Duchenne muscular dystrophy). In-frame deletions result in the production of subnormal amounts of dystrophin or the production of dystrophin that is abnormal in size. The presence of diminished amounts of dystrophin on histochemical stains of muscle biopsy specimens is diagnostic of Becker muscular dystrophy. The prevalence of Becker muscular dystrophy, as established by dystrophin analysis, has been reported to be 2.38 per 100,000, a rate greater than that assumed before dystrophin analysis became available.

In young patients, muscle biopsy shows active necrosis of muscle fibers with regeneration. In older patients, a chronic myopathic process is seen on biopsy specimens.

Clinical Features

The clinical manifestations of Becker muscular dystrophy can vary significantly, with the severity of the patient’s weakness directly related to the amount of dystrophin present. In milder forms of the disease (in which dystrophin levels are ≥20% of normal), patients may be able to walk into their 20s. In the most severe form, little dystrophin is present, and before the availability of dystrophin analysis, Duchenne muscular dystrophy was often misdiagnosed in these boys. Other patients with severe Becker muscular dystrophy were thought to have spinal muscular atrophy or limb-girdle muscular dystrophy. Bushby and Gardner-Medwin described two groups of patients with Becker muscular dystrophy. Children in the first group are younger at disease onset, lose the ability to ambulate in adolescence, and more frequently have cardiac involvement. In the second group, onset occurs at an older age, the disease follows a milder clinical course, and patients may walk until 40 years of age. Calf pseudohypertrophy is seen in Becker muscular dystrophy, as it is in the Duchenne type ( Fig. 39-17 ).

A and B, Pseudohypertrophy of the calf in a boy with Becker muscular dystrophy.

Medical Concerns

Cardiac involvement occurs frequently in patients with Becker muscular dystrophy. The age at onset of cardiomyopathy has been correlated with the patient’s specific dystrophin mutation. Up to 71% of people with the disease have electrocardiographic abnormalities. Dilated cardiomyopathy develops in a high percentage of patients and can be incapacitating and life-threatening. Because patients with Becker muscular dystrophy live longer than those with Duchenne muscular dystrophy, a more significant long-term workload is placed on the weakened myocardium, which leads to mitral regurgitation and heart failure. Severe restrictive lung disease is a less frequent and later complication.

Treatment

Orthopaedic management of patients with Becker muscular dystrophy is similar to that for patients with Duchenne muscular dystrophy. Ankle equinus has been treated successfully by Vulpius or heel cord lengthening, with posterior tibialis transfer to the dorsum of the foot being performed as needed. Lower extremity bracing is often prescribed for patients with Becker muscular dystrophy (in contrast to Duchenne muscular dystrophy) because loss of muscle strength occurs more slowly in these patients. As patients become nonambulatory, scoliosis develops, particularly in those with severe Becker muscular dystrophy. Spinal fusion, using the same principles as for patients with Duchenne muscular dystrophy, is recommended.

Medical treatment with prednisolone has been investigated, with improvement in muscle strength reported. Short-term improvement in strength has likewise been reported in a small series of patients given creatine supplements. Gene therapy is also under investigation.

Etiology and Diagnosis

Emery-Dreifuss muscular dystrophy is an uncommon, X-linked recessive form of the disease that was first described in 1966. The gene most frequently responsible for Emery-Dreifuss muscular dystrophy is the STA gene located in the Xq28 region of the X chromosome, which encodes for a nuclear membrane protein called emerin. The abnormalities in this gene have been described in the literature. Although the disease is usually inherited as an X-linked recessive trait, severe cases caused by autosomal dominant inheritance as a result of mutations in the lamin A/C gene have been reported. This gene is also disturbed in patients with type 1B limb-girdle muscular dystrophy and type 2B Charcot-Marie-Tooth disease.

Muscle biopsy specimens from patients with Emery-Dreifuss muscular dystrophy show a normal level of dystrophin but an absence of emerin. Microscopically, the muscles appear myopathic. Cardiac muscle biopsy specimens show structural changes within the myocardium. Skin biopsy to determine the presence or absence of emerin has been proposed as a diagnostic test.

Clinical Features

Emery-Dreifuss dystrophy is associated with the classic triad of slowly progressive muscle wasting and weakness, cardiomyopathy (most commonly manifested as heart block), and early contractures. Patients may have complaints of only diminished flexibility and contractures; because the cardiac manifestations are usually silent, it is critical that the orthopaedist be aware of this condition. Muscle weakness is manifested in a humeroperoneal distribution. The initial symptoms are mild weakness, clumsiness, and toe-walking. The Gowers sign may be present. Patients usually retain the ability to walk as they become older.

Laboratory Findings

Serum CK levels are elevated in males with Emery-Dreifuss muscular dystrophy, but the levels are not as high as those in patients with Duchenne or Becker muscular dystrophy. Female carriers of the disease do not usually have elevated CK levels.

Medical Concerns

The most serious medical condition associated with Emery-Dreifuss muscular dystrophy is cardiomyopathy. Patients are susceptible to conduction defects, and sudden death from complete heart block has occurred in patients in their 20s. In a series reported by Merlini and associates, 30 of 73 patients died suddenly, with most of them exhibiting no cardiac symptoms before the fatal heart block. Even female carriers without muscle weakness who have the STA gene may suffer bradyarrhythmias and die suddenly. Insertion of a pacemaker in patients in whom Emery-Dreifuss dystrophy is diagnosed has been recommended.

Treatment

The orthopaedic deformities associated with Emery-Dreifuss muscular dystrophy result from joint contractures, which are a hallmark of the disease. Achilles tendon contractures may be present at diagnosis, in which case patients may benefit from heel cord lengthening. Characteristic elbow flexion contractures occur but rarely exceed 90 degrees. Further flexion, pronation, and supination are preserved. Physical therapy may be helpful, but surgery is rarely indicated. Cervical extension contractures limit flexion of the neck, but they do not usually progress beyond the neutral position of the neck. Over time, lateral rotation may also become limited (rigid spine syndrome).

Scoliosis occurs in patients with Emery-Dreifuss muscular dystrophy, but unlike the situation in those with Du­­chenne or Becker muscular dystrophy, the curvature may stabilize. Thus, scoliosis in these patients does not always require spinal fusion. Progression of the curve should be monitored closely. The effect of contractures of the spine stabilizing curves of up to 40 degrees has been described ( Figs. 39-18 and 39-19 ).

A and B, Spinal radiographs of an 11-year-old girl with Emery-Dreifuss muscular dystrophy show mild scoliosis and increased lordosis throughout the spine.

Radiograph of the spine of a 16-year-old boy with scoliosis secondary to Emery-Dreifuss muscular dystrophy. The curve has an idiopathic appearance.

Anesthesia in persons with Emery-Dreifuss muscular dystrophy carries increased risk. In addition, intubation can be difficult because of cervical contractures, and cardiac arrhythmias may occur.

Etiology

Genetic analysis has identified numerous abnormalities. Type 2A LGMD is the most common form. The gene responsible for the production of calpain 3 is located on chromosome 15 and is defective in this type. Calpain is absent in patients with type 2A LGMD but, interestingly, is increased in patients with Duchenne muscular dystrophy. Type 2B LGMD is the result of mutations in the dysferlin gene on chromosome 2p13. Dysferlin is a transmembrane protein normally located in the sarcolemma. Types 2C through 2F are known as the sarcoglycanopathies. Type 2I results from mutations in fukutin-related protein. Fukutin mutations are also causative in congenital muscular dystrophy; therefore, these diseases are allelic. The genetic abnormalities that result in LGMD may also be shared by patients with Emery-Dreifuss muscular dystrophy and type 2b Charcot-Marie-Tooth disease, thus illustrating genetic overlap among the various progressive neuromuscular diseases.

Clinical Features

Significant similarities may be noted in the clinical manifestations of the different forms of LGMD, although disease severity can vary markedly, even within affected families. Onset is usually in the second or third decade at an average age of 17.2 years.

The age at onset of type 2A disease averages 14 years, with 71% of patients manifesting muscle weakness between 6 and 18 years of age. The disease is typically more benign than Duchenne muscular dystrophy, although the clinical course is variable. The age at onset and clinical symptoms mimic Becker muscular dystrophy, and type 2A LGMD was often confused with it before the availability of molecular genetic testing. The disease has also been mistaken for the Kugelberg-Welander form of spinal muscular atrophy. The mean age at loss of ambulation with type 2A disease is 32 years. In contrast, the onset of type 1A LGMD usually occurs in adulthood. This form is clinically distinct based on the presence of a dysarthric pattern of speech.

Two major patterns of weakness are noted in the various forms of LGMD. In the pelvic-femoral type, muscle weakness involves primarily the pelvic girdle musculature. In particular, the iliopsoas, gluteus maximus, and quadriceps are affected. Shoulder weakness becomes apparent soon thereafter. The tibialis anterior is affected before the gastrocsoleus. Contractures of the Achilles tendon and elbow are variable; in patients with type 2A LGMD, contractures develop early in the course of the disease, whereas in others, contractures may not develop for many years. Weakness of hip abduction and extension leads to increased lumbar lordosis. In the less common scapulohumeral type, the shoulder girdle is affected initially, with pelvic weakness occurring several years later. Initial symptoms include difficulty lifting the arms above the head, rising from the floor, or climbing stairs. Calf pseudohypertrophy may be present. Patients usually retain the ability to walk into adulthood.

Magnetic resonance imaging (MRI) shows typical patterns of muscular involvement in some forms of LGMD. In type 2I, changes are seen in the hip adductors, posterior thigh muscles, and gastrocsoleus. Clinical examination of this subset of patients shows weakness in hip flexion and adduction, knee flexion, and ankle dorsiflexion. In type 2A, MRI shows abnormal signal in the adductor and posterior thigh muscles as well, but the medial head of the gastrocnemius and the soleus muscles are significantly involved, whereas the lateral gastrocnemius is spared.

Laboratory Findings

Serum CK levels may be normal or elevated. Myopathy is noted on EMGs, but nerve conduction velocity is normal. Histologic evaluation of muscle biopsy specimens shows predominantly dystrophic changes; less frequently, myopathic and neurogenic changes may be present as well. Inflammatory cells are seen more frequently in the autosomal recessive forms, which is logical because these forms are clinically worse than the autosomal dominant subtypes. The diagnosis is made by immunoassay analysis of muscle tissue using antibodies against a panel of muscular dystrophy–associated proteins. For example, staining for dystrophin is normal in LGMD but abnormal in Duchenne and Becker muscular dystrophy, whereas stains for calpain are abnormal in patients with LGMD type 2A.

Medical Concerns

Cardiac involvement is less common overall in patients with LGMD. Electrocardiographic and echocardiographic abnormalities were discovered in 50% and 25% of patients, respectively. The clinical significance of these findings, however, remains unknown. Pulmonary involvement also occurs but is much milder than in Duchenne or Becker muscular dystrophy. The severity of pulmonary disease does not correlate with the degree of muscle weakness present in the limbs. Cardiac and pulmonary failure is more common in type 2I, the form linked with fukutin mutations.

Treatment

Treatment of LGMD is similar to that for Becker muscular dystrophy. Scoliosis rarely requires orthopaedic intervention because the onset of disease is later than that of Du­­chenne muscular dystrophy.

Etiology

Facioscapulohumeral (FSH) muscular dystrophy is inherited as an autosomal dominant trait and usually causes symptoms in the second decade of life. The incidence of FSH dystrophy is 1 in 20,000 live births. The gene for the disease has been localized to chromosome 4q35. The genetic defect is a deletion of a variable number of noncoding triplet repeats in the D4Z4 gene. Penetrance of the gene is variable, so even though the disease is transmitted as an autosomal dominant trait, clinical severity of the disease may vary among family members. Some individuals carry the mutation but have no identifiable muscle weakness. Females are more mildly affected than males and are more likely to be asymptomatic carriers.

Clinical Features

The clinical course of FSH muscular dystrophy is characterized by slow progression. Ninety percent of affected individuals have symptoms by the age of 20 years. Initial findings are a lack of facial wrinkles (noticeable around the eyes and on the forehead), a transverse smile, and an inability to fully and forcefully close the eyelids. A characteristic pattern of weakness involving the facial muscles and scapular stabilizers ensues.

The most significant weakness is seen in the trapezius, rhomboids, and levator scapulae. The deltoid remains strong, but its ability to abduct the shoulder is lost as the unstable scapula rotates with attempted abduction. Physical examination reveals winging of the scapulae, in addition to loss of forward flexion and abduction of the shoulder as a result of loss of stabilization of the scapula on the chest wall ( Fig. 39-20 ). As the patient tries to abduct the shoulder, the unstable scapula protrudes, elevates, and rotates inward. Patients complain of a loss of range of motion, stretching along the medial border of the scapula, pain, and fatigue.

A to C, Clinical appearance of a patient with facioscapulohumeral muscular dystrophy. Note the winging of the scapulae.

Lower extremity involvement is uncommon. Because the muscles of the lower limbs are usually spared, only 20% of patients eventually become wheelchair bound. Weakness of the anterior tibialis develops in some patients, and these individuals benefit from bracing. The hip girdle is affected late, and some patients may need wheelchairs in their 30s or 40s. Spinal deformity has been documented in up to 35% of patients, with the primary deformity being hyperlordosis. Scoliosis may occur but rarely requires treatment. Life expectancy is usually normal.

Laboratory Findings

Serum CK levels are generally normal in patients with FSH muscular dystrophy. Genetic testing can now demonstrate mutations in affected persons, but the size of the deletion varies among patients. The diagnosis of FSH muscular dystrophy is usually suspected on the basis of clinical findings. The supraspinatus muscle is recommended for obtaining a biopsy specimen to confirm the diagnosis when genetic testing is equivocal because specimens from other sites often result in nondiagnostic findings.

Medical Concerns

Medical complications from FSH muscular dystrophy are rare. Restrictive pulmonary disease has been documented (22% rate in one study). In a comprehensive survey of Dutch patients with FSH muscular dystrophy, 1% of the patient population was found to use nocturnal BIPAP. Cardiac disease occurs less frequently in these patients than in those with other forms of muscular dystrophy.

Treatment

The use of prednisone to slow the progression of FSH muscular dystrophy has not proved effective. However, trials indicate that albuterol (a β ₂ -receptor agonist) may be helpful.

Orthopaedic management of patients with FSH muscular dystrophy has focused on scapulothoracic stabilization ( Fig. 39-21 ). Indications for scapulothoracic fusion are intractable shoulder pain and loss of function because of lack of shoulder range of motion. Ketenjian first described scapulocostal stabilization for scapular winging in 1978 ( Plate 39-2 ). He advocated fixing the scapula to the ribs with double Mersilene tape, which he preferred to fascia lata. The tape is passed through drill holes along the medial border of the scapula and around three or four ribs. Alternatively, fixation of the scapula to the ribs may be achieved with wire passed through drill holes in the scapula and around the ribs, by plate and wire techniques, by multifilament cables, or by screw fixation.

Radiograph of the scapula after scapulothoracic arthrodesis with wire fixation to the ribs.

The position in which the scapula should be stabilized can be determined clinically by manually holding the scapula while the patient abducts the shoulder. When performing this maneuver, the preferred position of the scapula has been determined to be 15 to 20 degrees of external rotation. Less rotation does not maximize abduction, and greater abduction limits shoulder adduction. The scapula is not pulled distally because of the potential for endangering the brachial plexus.

Several authors have reported improvement in abduction ranging from 25 to 65 degrees and an increase in flexion ranging from 29 to 40 degrees after scapulothoracic arthro­desis. Demirhan and colleagues found that active shoulder flexion and abduction doubled 3 years following successful scapulothoracic fusion, with corresponding improvements seen in Disabilities of the Arms, Shoulder, and Hand (DASH) scores. Diab and co-workers found that some patients with FSH will experience a decrease in abduction following scapulothoracic arthrodesis over time, however, because of progression of weakness in the deltoid muscle.

The disadvantage of scapulothoracic fusion is limitation of rib motion, which can lead to loss of pulmonary function, although Bunch and Siegel found that vital capacity was reduced by approximately 10% in one patient (not clinically significant). Perioperative pulmonary complications (e.g., pleural effusion, atelectasis, pneumothorax) have also been described. Overall, complications of scapulothoracic arthrodesis are common and include brachial plexus palsy and pseudarthrosis. Intraoperative neuromonitoring of the brachial plexus may alert the surgeon to potential injury as a result of scapular repositioning. Despite modern fixation techniques consisting of plates, wires, and bone grafts, Krishnan and associates reported complications in more than half of their 22 patients.

One alternative to scapulothoracic fusion is scapulopexy, whereby the scapula is stabilized to the ribs via multiple wires, but fusion is not performed. A small study of 13 patients observed for an average of 10 years showed good results with only one incident of wire breakage.