Sacral agenesis

In the challenging field of pediatric orthopedics, the physician must learn to distinguish the abnormal from the wide variations of normal and avoid the mistake of improperly labeling a condition that neither merits nor requires correction. The extremely wide variations of normal body shape and function change spontaneously with age, and seemingly abnormal conditions at birth can resolve or improve over time, while other conditions are considered abnormal if they persist into adulthood. Normal variations can often be a source of great concern to parents, grandparents, friends and neighbors of perfectly healthy children.[1]

Once the specific area of concern is examined and the correct diagnosis made, the primary care physician must also perform a general musculoskeletal screening examination. For example, a child with metatarsus adductus must be examined carefully to rule out an accompanying congenital dislocation of the hip. After the general screening examination, the primary care physician must determine whether referral to a pediatric orthopedic surgeon is appropriate.

According to Staheli,[2] treatment is appropriate if the following three criteria are met: the therapy must be necessary, it must be effective, and the benefits must outweigh the accompanying risks and potential adverse psychosocial effects. Some normal orthopedic variants do not resolve as the child grows but are not serious enough to cause disability and thus do not necessitate corrective surgery. Ineffective treatment of conditions with a history of spontaneous resolution should be avoided. For example, corrective shoes, exercises and braces are not effective in the majority of cases.

Nearly all interventions can have negative aspects that must be weighed against the proposed benefits. Factors to consider include radiation exposure, financial cost, poor self-image, limited play function and the loss of opportunities to develop interpersonal and motor skills, the intrinsic risks of surgery (such as infection and exposure to anesthesia) and the prospect of worsening the disability. Observation is more appropriate than placebo treatments for parents who demand therapy for a "condition" that is a normal variant. Most parents respond positively to reassurance and the offer of close follow-up after a thorough examination and careful diagnosis.[2]

Etiology

Deformities (or deformations) occur when abnormal mechanical forces distort tissues. Deformation can be defined as an abnormality in the shape, position or form of a body or body part, caused partly by intrinsic or extrinsic mechanical molding.3 Hypomobility of the fetus secondary to a defect in the nervous system is an example of intrinsic molding (increased susceptibility to deformation), while uterine constraint is an extrinsic force.

Deformation can occur either prenatally or postnatally; other forms of dysmorphogenesis (i.e., malformations, disruptions, dysplasias) originate before birth. Deformation is rarely familial and, unlike other types of birth defects, may resolve spontaneously or after simple therapy. The musculoskeletal system is particularly susceptible to deformation. A list of factors causing fetal constraint and resultant deformation can be found in Table 1.[3,4]

Deformities (or deformations) occur metatarsus adductus, calcaneovalgus foot and some forms of clubfoot, are extremely common. Once a foot deformity is identified, a search should be made to detect other deformations, such as torticollis or congenital dislocation of the hip. Intrinsic anomalies of the central nervous system, bone or muscle should be considered if the gestational history fails to confirm the presence of extrinsic compression, includes a history of teratogenic exposure or contains the rare family history of deformation. Deformation not associated with intrinsic anomaly usually has an excellent prognosis because the infant is no longer exposed to the deforming force.3 Table 2 lists conditions known to cause foot deformities.[5]

Diagnosis

The calcaneovalgus foot (a cause of out-toeing), metatarsus varus or metatarsus adductus (a cause of in-toeing) and talipes equinovarus (clubfoot) are the three most common neonatal foot deformities.[5]

Feet in neonates often look very much alike, but disorders can easily be distinguished by seeking and documenting three variables. First, the foot should be examined from the side to see if it is in an abnormal, fixed equinus position (tiptoe/ tight-heel-cord/plantar-flexed). A normal neonatal foot can easily be dorsiflexed above the neutral position (90 degrees). Second, the, sole of the foot should be viewed from below to see if it is shaped like a kidney bean (deviated medially) or like a banana (deviated laterally). Third, the heel should be held in the neutral position and viewed from behind to check for heel varus (medial deviation) or heel valgus lateral deviation). Parameters that are used to formulate the diagnostic foot examination are summarized in Table 3.[5] [TABULAR DATA 5 OMITTED]

Calcaneovalgus Foot

The calcaneovalgus foot is the most common neonatal foot deformity. It is the result of positional confinement in utero. The foot has a banana-shaped sole (lateral deviation), dorsiflexes quite easily because of a stretched, abnormally long heel cord and has a heel that deviates laterally (Figure 1). Prognosis is excellent; most cases improve spontaneously and rapidly. Parents who are uncomfortable with the prescription of observation alone may be encouraged to exercise the child's foot at each diaper change by stretching the ligaments and dorsal tendons.

In the rare instance that the foot remains severely deformed, corrective casts are applied. If the calcaneovalgus foot can only be partially corrected, a flexible flatfoot results. The severe, resistant calcaneovalgus foot must be differentiated from a congenital vertical talus (congenital convex pes valgus), which is associated with neurologic disorders such as spina bifida or arthrogryposis in about 50 percent of cases. The vertical talus foot has a "rocker-bottom" appearance, with a tight heel cord.[5]

Metatarsus Adductus

The terms "metatarsus adductus" and "metatarsus varus" are used synonymously in practice, although they describe slightly different variations of the forefoot. In both cases, the heel deviates laterally, the sole is kidney-shaped (medial deviation) and the foot is easily dorsiflexed[5] (Figure 2). The incidence of metatarsus adductus is two cases in 1,000 live births.[1] Metatarsus adductus may be bilateral or unilateral and is probably secondary to in utero confinement. Often an infant presents with "windblown feet" (both feet pointing in the same direction), in which one foot has calcaneovalgus while the other has metatarsus adductus.[5]

Metatarsus adductus usually improves during the first two months of life, and 85 percent of cases fully resolve spontaneously.[6] The newborn examination should document the severity of the metatarsus adductus, which is classified as (1) mild/flexible, (2) moderate/fixed or (3) severe/rigid.[5] Associated deformities such as congenital dislocation of the hip should also be ruled out.

Parents should be taught how to stretch the child's foot by firmly holding and stabilizing the heel to prevent more heel valgus and stretching the forefoot laterally, holding for a count of five (the baby may wince but should not cry). The exercise should be performed five times at each diaper change.[5]

Mild, flexible metatarsus adductus should rapidly improve by two months of age. Moderate, fixed metatarsus adductus generally is not corrected with stretching alone, and the feet are still deformed at two months of age. To determine the extent of deformity, the child is held in a standing position, because weight-bearing makes the deformity even more obvious.

A pediatric orthopedic surgeon should be consulted when children with moderate fixed metatarsus adductus are approaching two months of age, so that the need for serial corrective casts can be determined. A child should be referred for possible casting by no later than four months of age, if possible, so that the foot is still pliable. By six months of age, foot stiffness and vigorous kicking make correction by serial casting difficult. The most common reasons cited for treating metatarsus adductus are prevention of bunions and calluses of the base of the fifth metatarsal as an adult, although treatment is controversial.[5] Rapid correction of metatarsus adductus can be obtained by applying three or four plaster casts every one to two weeks.[7]

Severe, rigid metatarsus adductus includes a fixed-joint deformity of the midfoot that does not respond to conservative therapy. Infants with this rare condition should be referred for serial corrective casting in the first few weeks of life to take advantage of neonatal ligamentous laxity resulting from exposure to maternal hormones. Corrective surgery is sometimes required, usually at two to four years of age.[5]

A moderate case of metatarsus adductus is occasionally accompanied by a persistent extreme adduction (medial deviation) of the great toe, or metatarsus primus varus. Application of shoes and socks is difficult, and surgical release of the abductor hallucis tendon may be necessary at six to 18 months of age.[5]

Clubfoot

Clubfoot is characterized by the inability to dorsiflex, the presence of heel varus (medial deviation) and a sole that is kidney-shaped when viewed from the bottom (Figures 3 and 4). Mild cases can be attributed to deformation caused by intrauterine compression, while more severe, fixed cases are usually secondary to underlying anatomic abnormalities, such as an ab-normal talus.

Accompanying deformities such as congenital dislocation of the hip must be ruled out, and the child must be examined carefully for an underlying neurologic or muscular disorder such as spina bifida, myotonic dystrophy or arthrogryposis. Newborns with dubfoot should be referred as soon as possible for corrective serial casts starting in the first week of life to take advantage of residual neonatal ligamentous laxity. Significant correction can be obtained with four to eight casts applied one week apart.

Some physicians try to maintain correction with shoesconnected to a device such as a Denis Browne splint. The splint and shoes are worn continuously for several months and then during naps and nighttime sleeping until the child is one year old or surgical correction is attempted. Severe clubfoot requires surgery (posteromedial release) late in the first year of life if full correction is to be achieved. The proportion of children requiring major surgery varies from 75 percent, if full anatomic, radiographic and clinical correction is attempted, to less than 50 percent, if mild radiographic and clinical deformity is accepted.[5]

Flexible Flatfoot

The flexible flatfoot is extremely common, with an incidence ranging from 7 to percent.[8] The condition is often hidden by normal adipose tissue in the infant foot and usually becomes noticeable after a child begins to stand. The most common etiology of the flexible flatfoot is ligamentous laxity, which allows the foot to sag with weight bearing (Figure 5). Children often have accompanying hyperextension of fingers, elbows and knees, as well as a family history of flatfoot and ligamentous laxity.

The child with flexible flatfoot secondary to ligamentous laxity can form a good arch when asked to stand on tiptoe. The heel rolls into a varus position (medial deviation) on tiptoe, and good strength of the ankle and foot muscles is assured (Figure 6).[5]

Flexible flatfoot may be secondary to a tight heel cord and muscular dystrophy, mild cerebral palsy (deep tendon reflexes are increased) or congenital tightness of the heel cords (normal deep tendon reflexes). A stiff and painful flatfoot is unusual and may be attributed to trauma, occult infection, a foreign body, tarsal coalition, bone tumors, Kohler's disease (osteochondrosis of the tarsal navicular bone) or other disorders. Radiographs are not routinely obtained for the diagnosis of flexible flatfoot but are useful in the examination of a stiff, painful flatfoot, which requires orthopedic referral.[1,5,8]

Treatment of the flexible flatfoot is controversial.[1,5] In the past, corrective shoes were modified in an attempt to improve the arch. Custom orthotics worn in normal shoes were tried, without documented success. In 1979, a survey by Staheli and Giffin[9] revealed that most pediatricians and pediatric orthopedic surgeons did not prescribe orthotic inserts or corrective shoes for children with flatfoot. A randomized, prospective study of 129 children with flexible flatfoot, comparing aggressive treatment using corrective shoes or orthotic inserts with no treatment, found no benefit from treatment.[10] Some physicians recommend that children with flexible flatfoot wear well-fitted tennis shoes and recommend special shoes only for children who complain of persistent pain or have such a severe deformity that regular shoes are worn out after a few weeks.[5]

Corrective Shoes

The 1979 survey by Staheli and Giffin[9] demonstrated for the first time that corrective shoes are not recommended by the majority of pediatricians and orthopedic surgeons for pediatric lower extremity deformities.

Most high-top leather infant shoes are made to fit children with metatarsus adductus and do not fit the straight inner border of a normal foot. These shoes are expensive and quickly outgrown. Staheli and Giffin[9] suggest that a properly fitted infant or child shoe should be straight and not exert any inward medial or lateral pressure on the toes. The shoe should be broad enough so the toes assume a natural, noncompressed position when the child is standing. Inexpensive shoes meet these requirements. High-topped shoes are only recommended when the child first begins to walk and is in danger of stepping out of a low-cut shoe.

REFERENCES

[1.] Salter RB. Textbook of disorders and injuries of the musculoskeletal system. 2d ed. Baltimore: Williams & Wilkins, 1983:101-44. [2.] Staheli LT. Philosophy of care. Pediatr Clin North Am 1986;33:1269-75. [3.] Dunne KB, Clarren SK. The origin of prenatal and postnatal deformities. Pediatr Clin North Am 1986;33:1277-97. [4.] Dunne PM. The influence of the intrauterine environment in the causation of congenital postural deformities with special reference to congenital dislocation of the hip [Thesis]. Cambridge, Eng.: Cambridge University, 1969. [5.] Wenger DR, Leach J. Foot deformities in infants and children. Pediatr Clin North Am 1986;33: 1411-27. [6.] Staheli LT. Torsional deformity. Pediatr Clin North Am 1986;33:1373-83. [7.] Ponseti IV, Becker JR. Congenital metatarsus adductus: the results of treatment. J Bone joint Surg [Am] 1966;48:702-11. [8.] Barry RJ, Scranton PE Jr. Flat feet in children. Clin Orthop Rel Res 1983;181:68-75. [9.] Staheli LT, Giffin L. Corrective shoes for children: a survey of current practice. Pediatrics 1980;65:13-7. [10.] Wenger DR, Mauldin D, Speck G, Morgan D, Lieber RL. Corrective shoes and inserts as treatment for flexible flatfoot in infants and children. J Bone Joint Surg [Am] 1989;71:800-10.

CATHERINE A. CHURGAY, M.D. is a clinical instructor in the Department of Family Practice at the University of Michigan Medical School, Ann Arbor, where she received her medical degree and served as co-chief resident.

COPYRIGHT 1993 American Academy of Family Physicians
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