ORTHOPEDICS AND MUSCULOSKELETAL CONDITIONS
Kevin P. Murphy, Colleen A. Wunderlich, Elaine L. Pico, Sherilyn Whateley Driscoll, Elizabeth Moberg Wolff, Melanie Rak, and
Maureen R. Nelson
GROWTH AND DEVELOPMENT OF THE BONY SKELETON
The skeletal system develops from mesoderm and neural crest cells (1). Somites form from paraxial mesoderm and differentiate into sclerotomes, dermatomes, and myotomes. Sclerotome cells migrate from the somite and ultimately become chondrocytes. The remaining dermatome cells form the dermis. Myotome cells give rise to striated muscles of the backs of limbs (Figure 10.1).
Limbs and respective girdles, the appendicular skeleton, are derived from cells of the lateral plate mesoderm. Limb buds appear in utero approximately on day 26 for the upper extremities and day 28 for the lower extremities (2). The hand plate forms in the fifth week, with digitization of rays in the sixth week. Notches appear between the rays in the seventh week, the failure of which results in syndactylism. During the seventh week, the limbs also rotate laterally in the upper extremities and medially in the lower extremities. This brings the thumb to the more lateral position in the upper extremity and the great toe to the more medial position in the lower extremity. Chondrification begins in the sixth week, followed by early ossification in the seventh week and subsequent joint cavity formation in the sixteenth week. By the eighth week, definite muscle formation is noted, as the embryo assumes a human appearance and basic organ systems are completed. The fetal period begins at 9 weeks with rapid growth and changes in body proportion (3).
Knowledge of the normal proportions and growth and development of the musculoskeletal system allows a firm foundation for the understanding of both congenital and acquired conditions requiring care in the developmental years.
Figure 10.2 displays the growth rates for boys and girls by age. About half of the individual's height is reached by age 2 and three-fourths by age 9. Prediction of adult height can be obtained by plotting bone age against current height to determine percentile value (Figure 10.3). Following the percentile to skeletal maturation is a method for estimating final adult height. Paley height multipliers offer an even simpler way of estimating adult height at any child age (4). Predictions are less accurate for the younger child (Figure 10.4). The reader is referred to more detailed references for tables displaying differences over time and growth and rates for standing, sitting, and subischial lengths in boys and girls (5). The measurement of arm span provides an indirect control parameter for the measurement of standing height, particularly useful in those who are nonambulatory. To measure arm span, the patient simply raises the arms to a horizontal position, and the distance between the tips of the middle fingers is measured with a tape measure (6,7). The standing height is about 97% of arm span. In children with spinal deformity, arm span is a good estimate of what standing height would be if there were no abnormal curvatures. It is well known that different proportions of the body grow and change at different percentages over the developmental years (Figure 10.5).
CONGENITAL CONDITIONS
Minor limb deficiencies are relatively common in the upper and lower extremities. Syndactyly occurs in approximately 1 in 2,200 births, either as cutaneous with simple webbing of the fingers or osseous with fusion of the bones when the digital rays fail to separate between the fifth to eighth weeks of gestation (8). It is most frequent between the third and fourth fingers and between the second and third toes, and is inherited as a simple dominant or simple recessive trait. It can occur in isolation or as part of a syndromic condition. Surgical separation of
FIGURE 10.1 Trilaminar disk. Neural tube closure. Mesoderm differentiates into dermatome, myotome, and sclerotome. Migrating sclerotome cells become chondrocytes. Chondrocytes ultimately form vertebral bodies and arches.
FIGURE 10.2 Greene and Anderson growth curve.
Source: Greene W, Anderson M. Skeletal age and the control of bone growth. Instr Led Am Acad Orthop Surg. 1960;17: 199-217.
the digits is more common with complete syndactyly for functional and cosmetic reasons. Polydactyly has an incidence of approximately 1 to 1.5 per 1,000 live births and is the most common congenital toe deformity (5). Eighty percent of Polydactyly in the foot occurs with the fifth toe. Most often an isolated trait, an autosomal-dominant inheritance pattern has been identified with variable expressivity. Radiographic evaluation is necessary to define duplicated structures. Deferring radiography until after 6 months of age allows phalanges to ossify. Surgery around the age of 1 not only improves cosmesis, but also is helpful in facilitating shoe fitting.
Camptodactyly, translated from Greek, means "bent finger." The proximal interphalangeal (PIP) joint is flexed, most commonly digit 5. Incidence is felt to be less than 1% of the general population with equal gender distribution (8,9). Appearance in adolescence, often girls, is less common. Surgical reconstructions are for functional and cosmetic reasons.
Malformations of the radius are more common than those of the ulna and are associated with numerous syndromes (5,10,11,12). In children with limb anomalies, a multisystemic review is generally indicated because abnormalities in other systems are often present. Simple and multifactorial inheritance may all be causative in addition to teratogenic effects, such as maternal exposure
FIGURE 10.3 Prediction of adult height. Adult height predicted by plotting child's bone age versus current height to determine percentile value. Follow the percentile to skeletal maturation for estimate of final adult height.
Height Multiplier: GIRLS, Birth to 18 Years Height Multiplier: BOYS, Birth to 18 Years
FIGURE 10.4 Paley height multipliers. Charts provide a simple method of predicting adult height for boys and girls.
to viral infections and chemical dependency such as alcohol (10). A failure of the scapular to descend from its cervical region overlying the first through fifth ribs results in Sprengel's deformity (6,13-16). Children often present with a shortened neckline (Figure 10.6). Lack of normal scapulothoracic motion and malpositioning of the glenoid causes limited forward flexion and abduction of the shoulder. An omovertebral bar is present in up to 50% of cases (17). The bar connects between the superior medial angle of the scapula and the cervical spine, and consists of fibrous cartilaginous tissue or bone. It is not uncommon to see other abnormal regional anatomy and syndromes that need to be screened for carefully, including scoliosis, spina bifida, rib anomalies, and Klippel-Feil syndrome (18,19). Renal and pulmonary disorders can also be present, and a renal ultrasound, if not already completed, is indicated. The condition can be bilateral in up to 30% of cases.
Congenital dislocation of the radial head unaccompanied by other congenital abnormalities of the elbow or forearm is rare (5). Congenital radioulnar synostosis is also a rare condition caused by failure of the radius and ulna to separate, usually proximal (Figure 10.7). The forearm is usually left in significant pronation with the condition bilateral 80% of the time (20). This condition is also associated with multiple other syndromes, which need to be carefully screened for (10). Children present for evaluation depending upon the degree of functional deficit. Radiographs can be helpful when ossification is present. MRI scans of the proximal radius and ulna can reveal more of a cartilaginous synostosis or a fibrous tether that has not ossified. Children with radioulnar synostosis without functional limitation should be observed. Success with surgery to resect the synostosis is often limited with minimal functional gain (5). Rotational osteotomies for pronation deformities greater than 45 degrees can be helpful. Postoperative compartment syndrome of the forearm needs to be watched for (21,22).
FIGURE 10.5 Proportions of the body as they change during growth. (Source: Lowrey GH. Growth and Development of Children. 6th ed. Chicago, IL: MYB; 1973.)
In about 5% of humans, there are minor variations in the number or proportions of vertebra (23). Osseous anomalies are felt to account for up to 6% of children who present with signs of torticollis. Individuals with cervical fusion are generally apparent on plain cervical radiographs, including flexion and extension views. The Klippel-Feil syndrome, sometimes called brevicollis, is characterized by short neck, low hairline, and restricted neck movement. Consisting of congenital fusions of the cervical vertebra, its incidence is approximately 0.7% (5,11). Failure of segmentation in the cervical spine most often characterizes the Klippel-Feil syndrome. Patients with Klippel-Feil syndrome or related conditions should have a renal ultrasound and cardiac evaluation (echocardiogram). Contact sports are contraindicated, as are similar, more aggressive activities.
FIGURE 10.6 Sprengel's deformity.
FIGURE 10.7 Radial ulnar synostosis.
Intraspinal anomalies need to be considered, especially in the presence of hairy patches, dimples, nevi tumors, or asymmetric or absent abdominal reflexes. In children with Down syndrome, atlantoaxial instability may be identified in up to 13% (11), but only 1% to 2% has symptomatic instability that requires surgery. X-ray examination of the cervical spine in children with Down syndrome is recommended at about the age of 3 years and before such children enter competitive sports such as the Special Olympics. Repeat x-rays are obtained after the cervical spine has been completely formed, at around the age of 8 years and every decade thereafter across the life span, as recommended by the American Association of Down Syndrome. The atlantodens interval (ADI) should be no greater than 4 mm in children 7 years of age and younger and no greater than 3 mm for children 8 years and older (5,8). ADI up to 5 mm has been accepted in the more traditional sense (24).
Clubfoot, talipes equinovarus, is a common term used to describe several kinds of ankle or foot deformities present at birth. The foot is generally in equinus, with forefoot and hindfoot varus and severe adduction (Figure 10.8). As the most common birth defect, it carries an incidence ranging from 1:250 to 1:1,000 live births, depending on the population (8). The condition is one of the most treatable of birth defects, often leading to normal or near-normal athletic activities later in life (5). Multifactorial genetic inheritance, along with poorly understood environmental factors, may explain the bulk of etiology. Some clubfoot disorders are transient or apparent in nature and result simply from intrauterine crowding. Other conditions may occur in association with myelodysplasia, arthrogryposis, and particularly hip dislocation. Prenatal ultrasound can be effective in diagnosing intrauterine clubfoot, with no false-negative prediction and a true-positive predictor rate of 83% (8). Recent treatment has focused primarily on the Ponseti technique (25,26,27,28). The range of motion (ROM) should be maintained by passive exercise and therapeutic play, particularly into dorsiflexion and eversion. Persistent deformity into adulthood can result in unstable ankles, lateral sprains, and difficulty with weight-bearing and other gross mobility tasks.
Metatarsus adductus can be seen in up to 12% of full-term births (8). Intrauterine crowding or positioning may be causative. Flexibility can be determined by fixing the hindf oot in a neutral position and gently manipulating the mid-foot and forefoot to a more lateral position. Internal tibial torsion may be associated, making the thigh-foot angle worse. Serial casting may be helpful in children under 1 year of age. Careful attention should be given not to place the hindfoot in valgus or create a skew foot deformity. Surgery is rarely indicated, but can be done in the more rigid persistent deformities after the age of 5. Various forms of posterior medial release are available (5).
Flat feet or pes planus may be flexible or rigid (5). Flexible pes planus is usually asymptomatic, at least in
FIGURE 10.8 Clubfoot deformity. Associated forefoot supination, deep medial crease, and equinovarus of the hindfoot.
the early years, and is the most common type found in children. Inexpensive scaphoid pads or medial inserts may help to create more plantigrade weight-bearing in the child, but they do not correct the deformity. Extreme cases, such as in children with hypotonia, may require surgery after the age of 5 years in the form of a calcaneal lengthening once the bony cortices are more solid. Untreated progression may occur with compensatory hallux valgus, planovalgus, and secondary bunion and toe deformities. Pes planovalgus is associated with more active or shortened peroneal musculature, progressing over time, with the development of pain, particularly in later years. Rigid pes planus is a congenital deformity associated with other anomalies in 50% of cases (29). It is caused by failure of the tarsal bones to separate leaving a bony cartilaginous or fibrous bridge or coalition between two or more tarsal bones (30,31). Talocalcaneal coalitions tend to become symptomatic earlier, between 8 and 12 years, whereas calcaneonavicular coalitions are more likely to be symptomatic between 12 and 16 years. Symptoms are insidious with occasional acute arch, ankle, and mid-foot pain. The hindfoot often does not align in its normal varus position on tiptoe maneuvers (5). Patients are predisposed to ankle sprain secondary to the limited subtalar motion, and stress to the subtalar and transverse tarsal joints frequently causes pain. Computed tomography (CT) scans are diagnostic, and initial treatment is conservative with short-leg casting or molded orthosis and rest. If conservative care fails, surgical intervention is usually necessary. With all symptomatic pes planus, accessory navicular bones need to be considered (8). Rigid cavus feet may be associated with metatarsalgia, clawing, and intrinsic muscle atrophy. With a cavus foot, stresses are increased across the joints, along with pressures on bony prominences, muscle strength being required to maintain posture. The result is pain, fatigue, and instability. The cavus foot may be caused by an underlying neurologic condition such as Charcot-Marie-Tooth disease, spinal dysraphism, Friedreich's ataxia, or spinal tumor. Custom-molded inserts or orthosis may be helpful in providing arch support and decreased pain by relieving pressure off bony prominences and providing a shock-absorber effect. Cavus feet can often run in families, making family history critical. Clinical exam for flexibility with localization of the deformity to the forefoot or hindfoot should be completed. The Coleman block test for determination of hindfoot flexibility can be critical, particularly for any surgical repair in the more rigid and symptomatic deformity (32). Plantar fascia release is standard for all cavus foot procedures (33,34).
Congenital vertical talus is exceedingly rare (5). The navicular bone is dislocated dorsolaterally on the head of the talus (Figure 10.9). It is commonly associated with neuromuscular and genetic disorders, including trisomy 13, 14, 15, and 18 (35). Clinical features include a rigid convex plantar surface (rocker bottom) with hindfoot equinus and hypoplastic laterally deviated forefoot. Casting can initially have some benefit for contracted dorsolateral soft tissues, but only as a prelude to surgical intervention. A single-stage procedure is generally the consensus (5) and can involve talectomy, naviculectomy, subtalar arthrodesis, and triple arthrodesis.
FIGURE 10.9 Vertical talus.
Arthrogryposis multiplex congenita refers to a symptom complex characterized by multiple joint contractures that are present at birth. The clinical literature has delineated as many as 150 entities under this term (8,36). The incidence of arthrogryposis as a whole is approximately 1 per 3,000 live births. Amyoplasia (which literally means no muscle growth) affecting all four limbs is less common, at approximately 1 in 10,000 live births (8). There are many different ways to classify the arthrogrypotic conditions (5,37). A simple way is to divide the contracture syndromes into three different groups (5). Group number 1 involves arthrogryposis multiplex congenita, Larsen syndrome, and more or less total body involvement.
Larsen syndrome is a rare condition involving multiple congenital dislocations of large joints, a flat fades, and significant ligamentous laxity (38,39). Patients commonly have abnormal cervical spine segmentation with instability and can be associated with myelopathy. Group number 2 would include the distal arthrogryposis predominantly involving hands and feet.
Distal arthrogryposis type II involves the presence of facial findings, whereas type I does not. Freeman-Sheldon syndrome is an example of distal arthrogryposis type II, with a characteristic "whistling face" appearance (40,41). Group number 3 involves the pterygium syndromes. Pterygium comes from the Greek word meaning "little wing." Pterygiums can be isolated or multiple. Multiple pterygium syndrome is characterized by webbing across every flexion crease in the extremities, most prominently across the popliteal space, elbow, and axilla (42). Popliteal pterygium syndrome has features involving the face, genitals, and knees (43). A popliteal web is usually present bilaterally running from the ischium to calcaneus, resulting in severe knee flexion deformities (Figure 10.10). The diagnosis of arthrogryposis can be suspected with prenatal ultrasound. Absence of fetal movements of distal or proximal joints in combination with polyhydramnios is suggestive (44). The birthing process can be complicated by joint contractures, with neonatal fractures resulting. Perinatal fractures are common and believed to be secondary to hypotonia and rigid joints (45). Therapy should not be initiated in a newborn until such fractures are ruled out (46). Children who survive infantile arthrogryposis often have upper and lower extremity involvement in typical patterns. Common deformities of the upper extremities include adduction; internal rotation contractures of the shoulders; fixed flexion or extension contractures of the elbows, either wrist flexion and ulnar deviation or extension and radial deviation; and thumb-in-palm deformities. In the lower extremities, flexion, abduction, and external hip rotation contractures with unilateral or bilateral dislocations are noted. Bilateral dislocations of the hip are more often left alone, whereas unilateral dislocations, because of scoliosis risk, are more often surgically treated (5). Fixed extension or flexion contractures of the knees are also seen along with severe rigid bilateral clubfeet. In the most severe rigid clubfeet, not
FIGURE 10.10 Isolated popliteal pterygium.
correctable with casting and conservative care, a talectotny may be necessary or talar enucleation in association with the posterior medial releases. Extension wedge osteotomies of the distal femur may be necessary to correct flexion contractures of the knee. There is always a well-recognized risk of neurovascular damage, with operative correction of knee flexion contractures needing careful consideration to avoid overstretching of the neurovascular bundle. Shortening osteotomies completed at the same time as the extension wedge osteotomy may minimize these risks. In the absence of degenerative neurologic conditions, individuals with arthrogryposis maintain their strength and ROM over time (5). Surgical and rehabilitation goals are generally centered on self-help skills, such as feeding, toileting, and mobility skills such as standing, walking, and transfers using assistive devices as needed. Surgical procedures of the upper extremity are usually delayed until the child is old enough for a more definitive functional assessment to be completed. If both elbows are involved with extension, surgery to increase flexion may be best done on only one side.
Outcomes appear better if joint surgery is completed prior to the age of 6 to avoid adaptive intra-articular changes (8). Osteotomies for realignment are usually performed closer to skeletal maturity. Early mobility and avoidance of prolonged casting may result in improved ROM and function postsurgery. Most individuals do not have intellectual impairment or sensory deficits. The children often have a keen natural ability to learn substitution techniques. A strong association between initial feeding difficulties and subsequent language development is known, which should not be misidentified as intellectual deficiency (47).
