The term clubfoot refers to a positional abnormality of the fetal foot, resulting in it being fixed in adduction, supination, and varus, with concomitant soft-tissue abnormalities (Drvaric et al., 1989). The Latin term talipes equinovarus (tali = ankle, pes = foot, equino = horse, varus = bent inward) (abbreviated as TEV) is used interchangeably with clubfoot.

Two general categories of clubfoot are recognized. Intrinsic clubfoot describes a foot that is rigid at birth with marked atrophy, fibrosis, and abnormal bony relationships. This form of clubfoot is generally treated by surgical intervention. Extrinsic clubfoot refers to a foot that is flexible at birth, although bony relationships may be abnormal. This type of clubfoot may be corrected conservatively, with manipulation and stretching (Kawashima and Uhthoff, 1990).

Even today, the cause of clubfoot is not precisely known. Most investigators agree that clubfoot is the result of an intrauterine developmental deformity, although controversy exists as to whether the cause is primarily muscular or neurologic in origin. The chief anatomic abnormality is the deformity of the talus, which is smaller than normal. Plantar and medial deviation of the head and neck of the talus also exists.

Bony malposition and subsequent development of contractures serve to keep the foot in a fixed position, resulting in forefoot adduction, midfoot supination, and hindfoot supination or equinus deformity (Drvaric et al., 1989). One hypothesis proposed for the cause of clubfoot involves a potential arrest in fetal development. The evidence for this relates to studies performed by Kawashima and Uhthoff (1990), who demonstrated that during normal embryologic development of the lower limb bud, the foot is first adducted in a position that resembles the clubfoot deformity at approximately 8 to 9 weeks of gestation (Figure 107-1) (Kawashima and Uhthoff, 1990). Movements of the fetal lower limb begin between 9 and 11 weeks of gestation. Thus, ifneurologic or muscular abnormalities impede limb movement, the joints will eventually become stiff and contracted. Flexion of the fetal foot occurs to the point at which by 11 weeks of gestation it reaches a normal position (Kawashima and Uhthoff, 1990). Therefore, some investigators believe that anything that arrests development of the fetal foot at approximately 8 to 9 weeks will eventually result in a clubfoot deformity. Other theories regarding the cause of clubfoot include primary bony abnormalities, either intrinsic or because of exogenous forces acting on the bone, primary muscle imbalances, ligamentous contractures with fibrosis, peroneal nerve weakness, peroneal dorsiflexor weakness, collagen abnormalities, neurogenic abnormalities, or the presence of subcellular retractile elements (Drvaric et al., 1989), excessive fibrous tissue resulting in a retracting fibrosis, contracture of myofibroblastlike cells enhanced by histamine release from mast cells, anomalous insertion of the Achilles tendon, tibialis anterior or peroneal tendons (Bleck, 1993), or relative delay in the growth of the tissues of the posteromedial foot and leg (Dietz, 1985).

Early amniocentesis, at 11 to 14 weeks of gestation, is associated with an increased incidence of clubfoot (Sundberg et al., 1997; Canadian Early and Mid-Trimester Amniocentesis Trial Group, 1998; Cederholm et al., 2005). Pediatric orthopedic surgeons who reviewed the data from the Canadian Early and Midtrimester Amniocentesis Trial group (CEMAT) concluded that the increase in foot deformities seen in the early amniocentesis group suggested that the period between 11 and 16 weeks is a vulnerable time (Tredwell et al., 2001). Weeks 12 to 16 are a period of maximal foot growth velocity and also a time when the fetus is developing coordinated movements, which are necessary for the development of normal synovial joints. During this period the amniotic fluid volume is also increasing exponentially. The orthopedists proposed that the loss or leakage of amniotic fluid induces a temporary fetal akinesia, which results in joint and limb deformities. The underlying mechanism is at present unknown, but has been speculated to be either a physical response or a result of maternal humoral and local microcellular response to the loss of amniotic fluid (Tredwell et al., 2001).

The incidence of clubfoot is approximately 1 in 1000 liveborn infants (Wynne-Davies, 1964a; Bakalis et al., 2002). In a study that encompassed a period of 45 years (1946-1990) in Malmo, Sweden, Danielsson (1992), determined that there were more than 128 cases of clubfoot in 137,614 livebirths that occurred over this period, yielding an incidence of 0.93 case per 1000 livebirths. In one study, the incidence of prenatally diagnosed clubfoot was 0.43% of cases (Treadwell et al., 1999). The incidence of clubfoot depends on the ethnic background of the patient. The highest incidence of clubfoot occurs in individuals of Polynesian ancestry, specifically Hawaiians and Maoris of New Zealand, who have an incidence of 6.5 to 7 cases of clubfoot per 1000 livebirths (Wynne-Davies, 1972; Drvaric et al., 1989). In all published studies, the incidence of clubfoot is more common in males than in females, with an approximate 2:1 ratio (Wynne-Davies, 1964a). In Danielsson’s study, 79% of affected patients were males (the range in other studies was 64%-76%) (Danielsson, 1992). Forty-four percent of cases are bilateral (range 40%-59%) (Danielsson, 1992). When the clubfoot is unilateral, there is a slight right-sided predominance (Drvaric et al., 1989). The incidence of clubfoot is not increased with advanced maternal age (Yamamoto, 1979). In one study, a seasonal variation was demonstrated, with an increased incidence of milder forms of clubfoot occurring in babies born between November and April (Pryor et al., 1991).

Prenatal sonographic detection of clubfoot is now common. The first prenatal diagnosis of clubfoot was reported in 1985 by Benacerraf and Frigoletto, who described five affected fetuses. Of the five fetuses, four had other associated malformations (Benacerraf and Frigoletto, 1985). These authors recommended examining the fetal lower extremity in a transverse section, in which the plantar aspect of the foot can be seen perpendicular to the shaft of the tibia (Figures 107-2 and 3). They made a diagnosis of clubfoot deformity when the foot was oriented in the same plane as the lower leg and was visualized only in a plane or section parallel to the lower leg rather than perpendicular to it. Transvaginal sonography has been used to diagnose the presence of bilateral clubfeet in a female fetus at 13 weeks of gestation (Bronshtein and Zimmer, 1989). In this case, the family history was notable for maternal congenital hip dysplasia and a maternal uncle with orthopedic problems in one of his ankles during infancy. This case highlights what has been noted previously in a genetic epidemiologic study of clubfoot: A high frequency of associated connective tissue disorders, such as hernia, congenital hip dislocation, and generalized joint laxity are observed in families that have at least one affected member (Wynne-Davies, 1964a).

The presence of a clubfoot deformity may not be apparent on an early sonographic scan. For example, intrauterine progression of a clubfoot deformity was demonstrated concurrent with the worsening of hydrocephalus observed by transvaginal scanning over a period between 11 and 16 weeks of gestation (Bronshtein et al., 1992). Similarly, in a fetus with trisomy 18, early scans performed at 14 and 17 weeks of gestation did not reveal the presence of a clubfoot deformity (Bar-Hava et al., 1993). At 21 weeks of gestation, multiple sonographic abnormalities, including clubfoot, were easily observed.

The targeted anatomic scan for a fetus with clubfoot should include measurement of amniotic fluid volume; observation for the presence of amniotic bands; detailed observation for the presence of masses within the uterus that could result in an abnormal, fixed position of the fetus; evidence for uterine abnormalities that might similarly crowd the fetus, resulting in a positional deformation; and a careful observation for the presence of associated anomalies.

Using this approach, a number of studies have looked at outcome for fetuses diagnosed with clubfoot (see Table 107-1). The relatively high percentage of associated anomalies (23%-62%) reflects the fact that most of these studies were performed in high-risk referral centers. Studies involving large numbers of liveborn infants quote a 10% incidence of associated anomalies (Yamamoto, 1979). Also of note is the fact that there is a significant false-positive rate for the diagnosis of clubfoot (Bar-On et al., 2005; Mammen and Benson, 2004). While three-dimensional sonography (see Figure 107-3) is not usually needed to make or clarify the diagnosis of clubfoot, in one case it was used to help a couple visualize the problem and better understand it (Mohammed and Biswas, 2002).