- Facioscapulohumeral (FSH) muscular dystrophy is a progressive disease of skeletal muscle that primarily affects the muscles of the face and shoulder girdle
- Diagnosis is typically made based on clinical symptoms but can be confirmed with genetic testing for a deletion of a variable number of noncoding triplet repeats in the D4Z4 gene located on chromosome 4q35
- Shoulder pain and loss of function is due to weakness of the scapular stabilizers
- Patients with intractable shoulder pain can be treated with scapulothoracic fusion
Description:FSH muscular dystrophy is a progressive disease of skeletal muscle that primarily affects the muscles of the face and shoulder girdle. Initial symptoms of facial weakness typically present in the first decade of life. Weakness of the scapular stabilizers is another characteristic finding. Involvement of the pelvic girdle can occur later in life, and the back extensors, iliopsoas, hip abductors, and quadriceps are spared until much later in the disease process. Unlike other forms of muscular dystrophy, calf pseudohypertrophy and muscle contractures are rare findings.
Epidemiology:The incidence of FSH is 1 in 15,000-20,000 live births (Altherr, 1995; Karceski, 2015).
Clinical Findings:Initial symptoms include a lack of facial wrinkles around the eyes and forehead, an inability to forcefully close the eyelids, and a transverse smile. A pattern of weakness involving the facial muscles and scapular stabilizers typically ensues. The most significant weakness is seen in the trapezius, rhomboids, and levator scapulae. The deltoid remains strong but loses its mechanical advantage to abduct the shoulder because the unstable scapula rotates with attempted abduction. Weakness of the muscles that stabilize the scapula to the posterior thorax creates an abnormally mobile scapula. Examination reveals winging of the scapula, in addition to loss of forward flexion and abduction of the shoulder, as these movements rely on a normal scapulothoracic relationship. As the patient tries to abduct the shoulder, the unstable scapula protrudes, elevates, and rotates inward (DeFranco, 2010). Patients complain of a loss of range of motion, stretching along the medial border of the scapula, pain, and fatigue. FSH muscular dystrophy is characterized by slow progression of disease symptoms. 95% of affected individuals have clinical findings by the age of 20 years (Tawil, 2006).
Lower extremity involvement is uncommon. 20% of affected patients eventually become wheelchair bound (Tawil, 2006). Tibialis anterior weakness can develop in some patients, who may benefit from bracing or tendon transfer. Spinal deformity has been documented in up to one third of patients, with the primary deformity being hyperlordosis. Scoliosis may occur but rarely requires treatment (Shapiro, 1993).
Medical complications from FSH muscular dystrophy are rare. Although up to 50% of patients have vital capacity evidence of restrictive pulmonary disease, only 13% have severe involvement. Cardiac disease occurs less frequently in these patients than in those with other forms of muscular dystrophy (Kilmer, 1995). Although rare, patients with a low number of copies of D4Z4 may develop problems with their vision. They develop Coats disease, which can be detected by an ophthalmologist using special equipment called indirect ophthalmoscopy (Karceski, 2015). Life expectancy is normal.
Unlike other types of muscular dystrophy, serum CK levels are generally normal in patients with FSH muscular dystrophy. Genetic testing can demonstrate mutations in affected individuals, but the size of the deletion varies among patients (Butz, 2003; Karceski, 2015). 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 non-diagnostic findings (Bodensteiner, 1986).
Treatment:The use of steroids such as prednisone to slow the progression of FSH muscular dystrophy has not proven to be effective (Tawil 1997); however, albuterol (a ?2-receptor agonist) and strength training may be helpful (van der Kooi, 2004). Orthopaedic management of patients with FSH muscular dystrophy has focused on scapulothoracic stabilization or fusion (Shapiro, 1993; DeFranco, 2010). The primary indication for scapulothoracic fusion is intractable shoulder pain; the secondary indication is loss of function because of lack of shoulder range of motion. The procedure does not restore full shoulder range of motion because this is dependent on both normal glenohumeral motion and scapulothoracic motion.
When performing a scapulothoracic fusion, the preferred position of the scapula is 15-20 degrees of external rotation. The fourth rib should align with the scapular spine. A plate and wire technique, with 18 gauge wires passed around the 3rd through 6th ribs and brought through burr holes in the medial border of the scapula, which is supported by a five-hole contoured reconstruction plate, has been described (DeFranco, 2010). Fusion can be expected to eliminate scapular winging and increase forward flexion and abduction by 25 degrees postoperatively (Letournel, 1990).
Complications:Complications of scapulothoracic fusion include pneumothorax, pleural effusion, atelectasis, fracture of the scapula, and pseudarthrosis (Shapiro, 1993; DeFranco 2010). Surgery improves the appearance of the shoulder through the elimination of winging. However, the patient must be warned in advance that full, normal function is not achieved with scapulothoracic stabilization, because fusion of the scapula to the thoracic wall limits elevation of the arm above the level of the shoulder.
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