The orthopedic examination of a newborn can at times be intimidating, even to an experienced pediatric orthopedist; just as children are not small adults, neonates are not small children. A thorough, consistent approach and agreed-on nomenclature can help identify musculoskeletal anomalies that may be present in isolation or may be part of a larger syndrome; treatment may vary from observation to casting or bracing to surgery. Being familiar with the most common diagnoses, their treatments, and anticipated outcomes can help ease parental anxiety and avoid unnecessary delays in treatment or overtreatment. Management of parental expectations is often one of the most important roles we as physicians serve.
PHYSIOLOGIC MUSCULOSKELETAL FINDINGS
Familiarity with the range of musculoskeletal findings in a newborn is important in that the line between physiologic and pathologic can be subtle. Often, severity and flexibility can be clues about whether a finding is normal.
Joint contractures, especially of the elbows, hips, and knees, are normal and slowly resolve over time; absence of these normal contractures may be the sign of an abnormality, such as arthrogryposis or congenital knee dislocation. If the contractures are especially severe and very stiff, that may also be a sign of arthrogryposis. Thumb-in-palm positioning is physiologic at birth, but lack of resolution over time may be a sign of neurologic abnormality.
Most infants are born with a bowed appearance of the tibia, which, in conjunction with the common external rotation contracture at the hip, gives the legs a “bowlegged” appearance. In fact, most of the apparent bowing is actually caused by internal tibial torsion; when the patella is placed directly forward, the knee will appear neutral to even slightly valgus. With time, the external rotation contracture at the hip and internal tibial torsion resolve so that by toddlerhood, most legs have “straightened out.” Abnormal tibial alignment in the neonate includes posteromedial and anterolateral bowing. Posteromedial bowing of the tibia is usually distal and often is associated with calcaneovalgus positioning of the foot; both resolve over time without formal treatment, but posteromedial bowing is associated with an ultimate leg length discrepancy of up to 3–4 cm that parents should be informed of at the outset. Anterolateral bowing can be midshaft or distal and is commonly associated with neurofibromatosis type 1 (NF 1); if anterolateral bowing is found on physical examination, it should be further evaluated by x-ray (Figure 64-1), and the patient should be closely examined for café-au-lait spots, axillary freckling, iris hamartomas, and other manifestations of NF 1. Finally, more nonspecific bowing of the tibia or the femur can be a sign of osteogenesis imperfecta.
Radiographic appearance of anterolateral tibial bowing seen in neurofibromatosis type 1.
Variation in foot alignment is extremely common in newborns and is usually the result ...