Osteochondritis dissecans is a localized form of ischemic necrosis that most frequently affects young males and is probably caused by trauma. It occurs primarily about the knee, usually on the lateral aspect of the medial femoral condyle. Other common locations are the ankle, femoral head, elbow, and shoulder.
In this condition, a small, round or oval necrotic segment of bone with its articular cartilage detaches and lies in a depression in the joint surface. Often denser than the surrounding bone, the necrotic segment is well-demarcated by a crescentic lucent stone. The necrotic segment may separate from the joint to form a free joint body, leaving a residual pit in the articular surface.
· medial femoral condyle
· gynecologic problems with dermatomyositis
A contracture refers to the permanent shortening and rigidity of muscles, joints, and fascial structures that may be a sequel to joint immobility due to disease or severe pain. Congenital contractures include clubfoot, torticollis, and the deformities associated with arthrogryposis (see the section “Arthrogryposis Multiplex Congenita” later in this chapter). Acquired contractures may reflect primary muscle, fascia, or ligamentous disturbances or be secondary to neural disorders (poliomyelitis, cerebral palsy), primary connective tissue diseases, or injuries to the skin (scarring, trauma, burns).
Volkmann’s contracture is a rare complication of fracture that is caused by muscle ischemia resulting in necrosis and subsequent fibrosis and contracture. This complication may develop whenever muscles are contained in a closed or confined compartment and subjected to a sustained increase in tissue pressure due to edema or hemorrhage. The major sites of ischemic contracture are the anterior tibial compartment and the forearm (especially in children following supracondylar fracture of the humerus). A fasciotomy in the affected compartment and repair of any associated arterial injury must be performed rapidly before irreversible muscle necrosis ensues. In Dupuytren’s contracture, contraction and thickening of the palmar aponeurosis causes flexion deformities and an inabilty to extend one or more of the fingers.
The radiographic manifestations of poliomyelitis reflect muscular weakness and paralysis due to necrosis and a loss of motor nerve cells in the spinal cord, brain, or cranial nerves. Decreased peripheral muscle tone causes a loss of muscular soft tissue volume and secondary bone atrophy; this produces thinning and demineralization of the bones of the extremities. Severe scoliosis of the thoracolumbar spine can develop. In patients with severely paralyzed extremities, calcification and ossification may form in the periarticular soft tissues and appear to bridge across the joints. This finding is most common about the hip.
Involvement of the phrenic nerve can cause paralysis of the diaphragm. Weakness of the accessory muscles of respiration may force the patient to require lifelong mechanically assisted ventilation. Radiographic changes associated with the chronic use of a respirator include erosive rib lesions, presumably secondary to the continued pressure of the scapula against the posterior aspect of the ribs, and discal calcification in the thoracolumbar spine.
Although there are no direct effects of polio virus on the lung, weakness of the thoracic musculature and retention of bronchial secretions can lead to recurrent pneumonia and focal atelectasis.
No radiographic changes are usually seen during acute polio virus infection.
Myositis ossificans refers to the development of calcification or ossification within injured muscles that is usually related to acute or chronic trauma to the deep tissues of the extremities. Persons in certain occupations and sports are prone to develop myositis ossificans. Thus heterotopic bone often arises in the adductor longus (rider’s bone), brachialis (fencer’s bone), and soleus (dancer’s bone) muscles.
The earliest radiographic change in myositis ossificans is a soft tissue mass that develops soon after injury. After about 1 month, faint calcification appears as a hazy shadow of increased density. Over a period of several weeks, the calcification becomes progressively denser and appears as a central lacy pattern of new bone formation surrounded by a sharply circumscribed peripheral cortex. The heterotopic calcification or ossification typically lies parallel to the shaft of the bone or along the axis of the muscle. Although the radiographic appearance may simulate a parosteal sarcoma, myositis ossificans is completely separated from the bone by a radiolucent zone, unlike the malignant tumor, which is attached by a sessile base and a discontinuous radio-lucent zone.
Up to half of patients with paraplegia demonstrate myositis ossificans in the paralyzed part. Osseous deposits occur in muscles, tendons, and ligaments. The heterotopic bone is most pronounced around large joints, especially the hip.
Generalized (progressive) myositis ossificans is a rare congenital dysplasia in which thick columns and plates of bone eventually replace tendons, fascia, and ligaments. This causes such severe contractures, deformity, and limitation of movement that the patient becomes a virtual “stone man” and death ensues.
Polymyositis is an inflammatory disease of skeletal muscles in which a lymphocytic infiltration produces muscle fiber damage and degeneration. In dermatomyositis, polymyositis is associated with skin inflammation and a characteristic rash. Adults with dermatomyositis have a relatively high incidence of underlying malignancy.
The musculoskeletal changes are most severe in childhood dermatomyositis. Diffuse edema of the subcutaneous and muscular tissues leads to increased muscular bulk and density, poor delineation of the normally sharp subcutaneous-muscular interface, and edema of subcutaneous tissue septa. In chronic disease, there is decreased muscle bulk and joint contractures. A characteristic finding is extensive calcification in the muscles and subcutaneous tissues underlying the skin lesions. This calcification may appear as superficial or deep masses, as linear deposits, or as a lacy, reticular, sub
cutaneous deposition of calcium encasing the torso. Radial subluxation or dislocation of the interphalangeal joint of the thumb is a not uncommon complication.
polymyositis and spleen
Dysfunction of the gastrointestinal musculature is most evident in the esophagus. A pattern of decreased peristalsis or esophageal atony, simulating scleroderma, is often produced. Because dermatomyositis and polymyositis involve striated muscle (infrequently affected by scleroderma), there aiso may be disruption of the normal stripping wave in the upper third of the esophagus. Atony and dilatation of the stomach and small bowel can also occur.
Many patients with polymyositis or dermatomyositis have normal chest radiographs. In others, there may be a diffuse reticular or reticulonodular interstitial pattern that predominantly involves the lung bases. The radiographic findings usually respond dramatically to corticosteroid therapy. Unlike other connective tissue disorders that produce a similar radiographic appearance, polymyositis and dermatomyositis are infrequently associated with pleural effusion. Involvement of the muscles of respiration, particularly the diaphragm, can cause diaphragmatic elevation along with basilar atelectasis and a decrease in lung volume. Paralysis of the pharyngeal musculature can lead to patchy aspiration pneumonia.
· polymyositis and the spleen
· polymyositis pituitary
Myotonic dystrophy is an inherited disease in which an anatomic abnormality of the motor end plate and striated muscle leads to atrophy and an inability of the contracted muscle to relax (myotonia). Associated findings include cataracts, frontal baldness and testicular atrophy in men, and a characteristic facial expression (myopathic facies).
In addition to severely disturbed pharyngeal peristalsis associated with the pooling of contrast material within the valleculae and pyriform sinuses, patients with myotonic dystrophy have a reduced or absent resting pressure of the cricopharyngeus muscle. Because a major function of this upper esophageal sphincter is to prevent esophageal contents from refluxing into the pharynx, the diminished resting tone in patients with mvotonic dystrophy permits easy regurgitation from the esophagus
into the pharynx and leads to a high incidence of aspiration. Reflux across the cricopharyngeus muscle results in the characteristic radiographic pattern of a continuous column of barium extending from the hypopharynx into the cervical esophagus, even during the resting phase when the patient is not swallowing. Concomitant smooth muscle atrophy can lead to dilatation and diminished peristalsis within affected segments of the gastrointestinal tract.
peristalsis myotonic dystrophy
About half the patients with myotonic dystrophy demonstrate changes within the skull. These include a generalized increase in the width of the calvarium, a small sella turcica, and enlargement of the frontal sinus. Progressive atrophy of skeletal muscle is manifested radio-graphically by loss of muscle mass and a corresponding increase in fat and connective tissue deposition between the remaining muscle bundles, nonspecific findings that can be seen in other forms of muscular dystrophy.
Pharyngeal dysfunction can lead to the development of patchy areas of aspiration pneumonia. Diaphragmatic involvement results in elevation of the diaphragm along with basilar atelectasis and an increased incidence of infection. Rare involvement of the cardiac muscles may lead to generalized cardiac enlargement and congestive heart failure.
Replacement of muscle by fat in the muscular dystrophies results in a characteristic radiographic appearance of the extremities. Although the total muscle mass is not decreased, the extensive accumulation of fat within the remaining muscle bundles produces a fine striated, or striped, appearance. In the pseudohypertrophic dystrophy of Duchenne, enlargement of specific muscle groups (calves, shoulder girdles) suggests muscular strength, though the patient is actually extremely weak. In wasting diseases, most of the muscle tissue is replaced by fat, so the fascial sheath bounding the muscle stands out as a thin shadow of increased density as it is visualized on edge.
A characteristic sign of muscular dystrophy is unusual widening of the shaft of the fibula in its anteroposterior diameter. Decreased muscular tone can lead to osteoporosis, bone atrophy with cortical thinning, scoliosis, and joint contractures.
An abnormal swallowing mechanism in muscular dystrophy can result in the failure to clear barium adequately from the valleculae and pyriform sinuses; this may lead to tracheal aspiration and nasal regurgitation of barium.