Alignment Disorders

Etiologies, Pathophysiology, and Clinical Presentation.

Neonatal brachial plexus palsy (also know as Erb palsy or brachial plexopathy ) is caused by injury to the cervicothoracic nerve roots during birth. It is associated with prolonged, difficult delivery (dystocia) and with larger infants. Infants present with decreased motion of the involved extremity. Children with a persistent defect will hold their arms in internal rotation with pronation of the forearm and flexion of the wrist (waiter's tip arm). This is the most common insult leading to secondary glenohumeral dysplasia.

Imaging.

At birth, radiographs can exclude fractures of the clavicle and humerus. Ultrasonography (US) and magnetic resonance imaging (MRI) have been used to directly evaluate the brachial plexus; however, the primary goal of advanced imaging is to evaluate orthopedic anatomy to determine function and orthopedic treatment as primary repair of the brachial plexus injury is difficult.

Progressive deformity with secondary glenohumeral dysplasia manifests as a small, flattened humeral head, which may sublux, usually in the posterior direction relative to a small, shallow, abnormally retroverted glenoid ( Fig. 133.1 ). In normal shoulders, glenoid version is near neutral, often mildly retroverted by approximately 5 degrees relative to a line perpendicular to the axis of the scapular body. With brachial plexus palsy, glenoid retroversion averages 25 degrees. The scapula is hypoplastic and elevated; the acromion is tapered and inferiorly directed, as is the coracoid; and the clavicle is shortened.

Many of these findings are seen on radiography. Computed tomography (CT) or MRI can be used to quantify the degree of glenoid retroversion, deformity of the glenoid and humeral head, glenoid–humeral head congruence, and relative muscle volume and quality of the affected shoulder. Ultrasound is useful, particularly in infants because no sedation is required, to evaluate muscle bulk, degree of glenoid and posterior labral abnormality, and dynamic alignment of the shoulder. The alpha angle can be measured to assess the degree of humeral head subluxation ( e-Fig. 133.2 ). The glenoid normally has a concave shape. With glenohumeral dysplasia, the glenoid becomes progressively flat, convex, or biconvex with a pseudoarticulation with the humeral head. MRI is preferred in young children (<5 years old) ( e-Fig. 133.3 ) to evaluate the cartilaginous glenoid; CT is sometimes preferred in older children to evaluate cortical bone.

Treatment.

Microsurgery techniques may be attempted to address the underlying traumatic neural injury. Controversy exists as to their role and proper timing. Typical treatment focuses on the reconstructive surgical techniques of the shoulder and distal upper extremity to preserve joint integrity and maximize function.

Etiologies, Pathophysiology, and Clinical Presentation.

In Madelung deformity, the radius is short and its distal articular surface tilted toward to ulna. The cause of the deformity is usually unknown. Madelung deformity occurs more often in girls. Patients may have pain; however, treatment is more often sought because of deformity or limited range of motion. Bilateral involvement is more common in the setting of an associated syndrome. Madelung deformity is occasionally seen with Turner syndrome and is a characteristic of Léri-Weill syndrome. Among these cases, 10% to 15% are familial. A Madelung-like deformity may also be seen in patients with hereditary osteochondromatosis or enchondromatosis, also suggesting a defect in normal distal radial maturation. It may also occur as a complication of infection or trauma that results in medial and volar radial physeal growth disturbance.

Imaging.

The distal articular surface of the radius is tilted in an ulnar and volar direction. The radius is short and bowed dorsally and laterally (“bayonet deformity”) ( Fig. 133.4 ). Secondary distortion of the carpus is observed with an abnormally narrow carpal angle and proximal lunate migration. The distal ulna is subluxed. The distal radial growth plate may prematurely fuse along its ulnar and volar aspect. CT or MRI may be used to assess the extent of distal radial physeal fusion. MRI can also identify an anomalous radiolunate ligament (Vickers ligament) which is present in true, idiopathic Madelung deformity.

Treatment.

Treatment is aimed at relieving pain caused by ulnocarpal impingement and improving wrist mobility. Ulnar shortening and radial wedge osteotomies are common techniques.

Etiologies, Pathophysiology, and Clinical Presentation.

Trauma, infection, inflammatory arthropathy (juvenile idiopathic arthritis), or other causes of premature fusion may lead to shortening of the ulna relative to the radius (negative ulnar variance) or shortening of the radius relative to the ulna (positive ulnar variance) ( Fig. 133.5 ). Most cases are idiopathic. Hyperemia resulting from fracture healing, infection, or vascular anomalies may lead to single bone over growth. Osteochondromas of either the radius or ulna can also lead to shortening of the affected bone.

Imaging.

At skeletal maturity, the distal radial and ulnar articular surfaces are nearly at the same level, and the radial styloid projects 9 to 12 mm distal to the ulnar articular surface. With negative ulnar variance, the ulna ends more proximally, and with positive ulnar variance, the ulna ends more distally ( e-Fig. 133.6 ). Ulnar variance may be exaggerated with forearm pronation and decreased with forearm supination.

Treatment.

Osteotomy with ulnar or radial shortening may be indicated to reduce symptoms and avoid complications. Negative ulnar variance is associated with the development of avascular necrosis of the lunate (Kienböck disease). Positive ulnar variance is associated with ulnolunate impaction syndrome ( Fig. 133.7 ) and triangular fibrocartilage complex degeneration.

Etiologies, Pathophysiology, and Clinical Presentation.

The normal neck-shaft angle of the proximal femur is approximately 150 degrees at birth and decreases to 120 to 130 degrees in adulthood. External or internal rotation of the hip or femoral anteversion may affect this measurement.

Functional coxa vara occurs with disorders that result in femoral neck shortening, as in trauma, infection, or epiphyseal osteonecrosis. This can result in abnormal growth at the proximal femoral physis that produces abnormal angulation. Coxa vara also occurs as a congenital anomaly that is caused by bone softening (e.g., rickets, osteogenesis imperfecta, fibrous dysplasia) or abnormal growth (e.g., spondyloepiphyseal dysplasia congenita, spondyloepimetaphyseal dysplasia, cleidocranial dysplasia, proximal focal femoral deficiency). Children will present with a limp (unilateral deformity) or a waddling gate (bilateral deformities). With infantile or developmental coxa vara, the hip is normal at birth, and deformity is noted when the child begins to walk and can be self-limited. Acquired coxa vara is caused by other processes such as trauma.

Imaging.

In coxa vara, the femoral neck-shaft angle is decreased from normal. A measurement below 120 degrees is considered coxa vara. Fragmentation and sclerosis may be seen at the medial margin of the proximal femoral metaphysis ( Fig. 133.8 ). The Hilgenreiner epiphyseal angle is the angle between the Hilgenreiner line and a line drawn through the proximal femoral physis ( e-Fig. 133.9 ). The normal angle is less than 30 degrees. If it is less than 45 degrees, progression is unlikely. If over 60 degrees, progression is likely. If 45 to 60 degrees, prognosis is less predictable.

Treatment.

Surgical management may be warranted for progressive disease, especially if asymmetric or associated with pain or leg length discrepancy. Valgus osteotomy is performed, and physeal fixation or tendon transfers may also be performed to deter progression and improve mechanical function.

Etiologies, Pathophysiology, and Clinical Presentation.

With coxa valga, the neck-shaft angle of the proximal femur is increased. Coxa valga is most often seen in patients who are nonambulatory and nonerect, such as those with cerebral palsy and other neuromuscular disorders ( Fig. 133.10 ).

Imaging.

The femoral neck-shaft angle is measured on frontal radiographs. External rotation may mimic coxa valga; with external rotation, the greater trochanter projects through the femur and the lesser trochanter is visualized in profile, whereas with true coxa valga in appropriate position, the appearance of the trochanters are reversed. Increased femoral anteversion may also cause the femoral neck-shaft angle to be overestimated. Acetabular dysplasia and hip subluxation are frequently concomitant findings.

Treatment.

Varus osteotomy and iliac osteotomy are often performed together in patients with cerebral palsy to better direct the femoral head into the acetabulum.

Etiologies, Pathophysiology, and Clinical Presentation.

Femoral version is the angulation of the femoral neck in the transverse plane measured relative to the femoral condyles distally ( Fig. 133.11 ). If the femoral neck is anteriorly angulated with respect to the femoral condyles, the femur is anteverted. If the femoral neck is posterior with respect to the femoral condyles, the femur is retroverted. Normal femoral anteversion is around 35 to 50 degrees at birth, decreasing steadily to around 8 to 15 degrees in adulthood ( e-Fig. 133.12 ).

Increased femoral anteversion may hinder proper localization of the femoral head relative to the acetabulum. Increased femoral anteversion may be idiopathic or seen in hip deformities caused by developmental hip dysplasia, Legg-Calvé-Perthes disease, and cerebral palsy. Increased anteversion is associated with in-toeing of feet.

Imaging.

On CT, femoral anteversion is the angle between the axis of the femoral neck and the transcondylar axis at the distal femur ( Fig. 133.13 ). Limited low-dose axial images are usually performed; however, axial oblique or three-dimensional (3D) images may improve measurement accuracy. CT imaging can be obtained concomitantly to evaluate for femoroacetabular impingement and tibial torsion. The biplanar digital slot-scanning radiologic device (EOS Imaging, Paris, France) uses two narrow fan beam sources to acquire concurrent, high-quality, orthogonal radiographic images of the spine or entire lower extremities. Frontal, lateral, and 3D views can be generated from the obtained data. Standard radiographic measurements of the lower extremities can be performed with these images. Also beneficial is lower radiation exposure with this device compared to standard radiographs and CT while maintaining image quality.

Treatment.

Most children with increased femoral anteversion are managed conservatively. Surgical indications for treatment include symptomatic in-toeing. Femoral rotational osteotomy may be performed to optimize femoral version.

Etiologies, Pathophysiology, and Clinical Presentation.

Tibial torsion is the degree of rotation of the distal tibia relative to the upper tibia. Newborns have internal tibial torsion relative to older children and adults. Lack of normal progression leads to in-toeing. Internal tibial torsion is the most common cause of in-toeing in the preschool age group.

Imaging.

Assessment of tibial torsion is often performed with assessment of femoral version. Limited axial low-dose CT images are obtained through the proximal and distal tibias. Tibial torsion is best measured as the angle between the posterior proximal epiphyseal cortical margin and a bimalleolar line distally. Normal values are neutral to mild (5 degrees) of external torsion in a newborn, which progresses to 18 to 47 degrees of external rotation in an adult.