Alignment Disorders

Chapter 134


Alignment Disorders





Upper Extremities



Erb Palsy






Imaging: At birth, radiographs serve to exclude fractures of the clavicle and humerus. Ultrasonography and magnetic resonance imaging (MRI) have been used to directly evaluate the brachial plexus;1,2 however, the primary goal of advanced imaging is to evaluate orthopedic anatomy to determine function and orthopedic treatment since 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. 134-1).3 In normal shoulders, the glenoid is mildly retroverted by approximately 5 degrees posteriorly relative to a line perpendicular to the axis of the scapular body.4 With Erb palsy, glenoid retroversion averages 25 degrees. The scapula is hypoplastic and elevated; the acromion is tapered and inferiorly directed, as is the coracoid; the clavicle is shortened.



Many of these findings are seen on radiography; however, 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.5–9 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. 134-2) and CT in older children. To determine glenoid version, the articular cartilage should be used when MRI is performed; the glenoid cortical bone should be used when CT is performed. In infants, ultrasonography may be used to assess instability of the glenohumeral joint.1012





Treatment: Microsurgery techniques may be attempted to address the underlying traumatic neural injury.13 Controversy exists as to their role and proper timing. The main focus of treatment is on the reconstructive surgical techniques of the shoulder, elbow and forearm, and hand and wrist, aimed at preserving joint integrity and maximizing function.13,14 Therefore, imaging optimization should be tailored for orthopedic anatomy rather than the brachial plexus.



Madelung Deformity





Etiologies, Pathophysiology, and Clinical Presentation: In Madelung deformity, the radius is short and its distal articular surface tilted toward to ulna.15 In most cases, the cause of Madelung deformity is unknown. Madelung deformity occurs more often in girls.16 Patients may have pain; however, treatment is more often sought because of deformity or limited range of motion. With an underlying syndrome, the deformity is more likely to be bilateral. Madelung deformity is occasionally seen with Turner syndrome and is a characteristic in dyschondrosteosis (Léri-Weill syndrome) (Fig. 134-3).15 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. Madelung deformity may occur as a complication of infection or trauma that results in medial and volar radial physeal growth disturbance.17




Imaging: The distal articular surface of the radius is tilted in an ulnar and volar direction.18,19 The radius is short and bowed dorsally and laterally (“bayonet deformity”). Secondary distortion of the carpus is observed with an abnormally narrow carpal angle and proximal lunate migration.18,19 The distal ulna is subluxed. The distal radial growth plate may prematurely fuse along its ulnar aspect. CT or MRI may be used to assess the extent of distal radial physeal fusion.20




Ulnar Variance






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.21,22 With negative ulnar variance, the ulna ends more proximally, and with positive ulnar variance, the ulna ends more distally (e-Fig. 134-5).21,23 Ulnar variance may be exaggerated with forearm pronation and decreased with forearm supination.






Lower Extremities



Hip/Femur



Coxa Vara




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.25 External or internal rotation of the hip or femoral anteversion may affect measurement.26


Functional coxa vara occurs with disorders that result in femoral neck shortening, as in trauma, infection, or epiphyseal osteonecrosis.27 True coxa vara occurs as a congenital anomaly that is caused by bone softening (e.g., rickets, osteogenesis imperfecta, fibrous dysplasia) or to abnormal growth (e.g., spondyloepiphyseal dysplasia congenita, spondyloepimetaphyseal dysplasia, cleidocranial dysplasia).28,29 Children with developmental coxa vara present with a limp (unilateral deformity) or a waddling gate (bilateral deformities). Coxa vara may occur as the result of abnormal growth at the proximal femoral physis that results in abnormal angulation of the physis. Congenital coxa vara occurs with a congenital short femur (i.e., proximal focal femoral deficiency) and does not spontaneously resolve.28 With infantile or developmental coxa vara, the hip is normal at birth, and deformity is noted when the child begins to walk.28,30 Infantile coxa vara may be self-limited. Acquired coxa vara is caused by another process such as trauma.28



Imaging: In coxa vara, the femoral neck-shaft angle is decreased from normal. A measurement below 110 degrees is considered coxa vara.31 Fragmentation and sclerosis may be seen at the medial margin of the proximal femoral metaphysis (Fig. 134-7).30 The Hilgenreiner epiphyseal angle is the angle between the Hilgenreiner line and a line drawn through the physis (e-Fig. 134-8).28,31 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, leg length discrepancy, or both.28 Valgus osteotomy is performed, and physeal fixation or tendon transfers may also be performed to deter progression and improve mechanical function.



Coxa Valga





Imaging: The femoral neck-shaft angle is measured on radiographs. External rotation may mimic coxa valga and can be differentiated through the positioning of the greater trochanter.26 With external rotation, the greater trochanter projects through the femur, whereas with true coxa valga, it is located laterally. Increased femoral anteversion may cause the femoral neck-shaft angle to be overestimated.32 Acetabular dysplasia and femoral subluxation are frequently concomitant findings.32




Femoral Anteversion




Etiologies, Pathophysiology, and Clinical Presentation: Increased femoral anteversion may hinder proper localization of the femoral head relative to the acetabulum. Increased femoral anteversion is seen in hip deformity caused by developmental dysplasia of the hip, Legg-Calvé-Perthes disease, and cerebral palsy.32 With increased anteversion, in-toeing of feet is noted.


Femoral version is the angulation of the femoral neck in the transverse plane measured relative to the femoral condyles distally (Fig. 134-10). 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 35 to 50 degrees at birth, decreasing steadily to 10 to 15 degrees in adulthood (Fig. 134-11).27







Leg



Tibial Torsion





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.41 Tibial torsion is best measured as the angle between the posterior epiphyseal cortical margin of the tibia proximally and a bimalleolar line distally. Normal values are 5 degrees of external rotation in a newborn, which progresses to 15 to 20 degrees of external rotation in an adult.40,42




Bowleg (Genu Varum)




Etiologies, Pathophysiology, and Clinical Presentation: Bowleg deformity manifests as separation of the knees, with the legs in anatomic position. Pathologic causes include rickets, osteogenesis imperfecta, neurofibromatosis, skeletal dysplasias (i.e., campomelic dysplasia, achondroplasia), focal fibrocartilaginous dysplasia, congenital bowing, Blount disease, and, occasionally, growth plate trauma.43–46 Recently, greater prevalence of bowleg and tibia vara has been noted in some adolescent athletes, most notably soccer players.4749 Repetitive stress on the proximal tibial physis may play a role in this.48 Most lateral bowing in otherwise normal infants and children younger than 2 years of age is normal and developmental (“physiologic”) and resolves without treatment.44,5052 Similar to Blount disease, exaggerated physiologic bowing is seen in early walkers, African Americans, and heavier children.44



Imaging: Ozonoff described the following findings as characteristic of physiologic lower extremity bowing: (1) The tibia is abducted relative to the femur, and both bones are intrinsically bowed laterally; relative tibial torsion produces external rotation of the upper tibia relative to the distal tibia; (2) margins of the distal femoral and proximal tibial metaphyses are mildly accentuated with small beaks; (3) medial cortices of the tibia and femur are thickened; (4) distal femoral and proximal tibial epiphyses are not well ossified medially and are wedge shaped; (5) the distal tibial growth plate may be tilted lateral.53


Radiographically, the femur and the tibia are also mildly bowed anteriorly, with beaking occurring posteriorly (Fig. 134-13). Physiologic bowing is usually more marked in the tibias. Occasionally, lateral bowing may almost exclusively be seen in the distal femur (e-Fig. 134-14). The varus deformity is common in normal infants and converts to valgus between 18 and 36 months of age. Degree of valgus reduces spontaneously by 6 to 7 years of age to a mild degree that remains throughout life. Approximate normal angles are 17 degrees varus in a newborn, 9 degrees varus at 1 year, 2 degrees valgus at 2 years, 11 degrees valgus at 3 years, and 5 to 6 degrees valgus at 13 years (e-Fig. 134-15).52,54,55






Radiographs should be taken with the patient bearing weight as soon as he or she is able to stand (Fig. 134-16). The radiographs may suggest an underlying disorder such as rickets or a dysplasia.




Treatment: Persistent varus with delayed conversion to valgus may indicate a higher likelihood of Blount disease (tibia vara). In the second year, it may be difficult to distinguish normal physiologic bowing from Blount disease.56 Exaggerated varus during the second year is likely developmental or physiologic and does not require treatment.50,51,54 Any varus at the knee after 2 years of age should raise concern. Such patients must be monitored to exclude progression to Blount disease.55,57 Realignment surgery is rarely needed in isolated bowleg without underlying dysplasia, metabolic bone disease, or Blount disease.



Blount Disease (Tibia Vara)




Etiologies, Pathophysiology, and Clinical Presentation: Blount disease (tibia vara; osteochondrosis deformans tibiae) is a progressive deformity affecting the proximal tibia (Fig. 134-17).5860 It is theorized that stress on the posteromedial proximal tibial physis causes growth suppression.


Dec 20, 2015 | Posted by in PEDIATRIC IMAGING | Comments Off on Alignment Disorders
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