13.21 Congenital talipes equinovarus

The treatment of patients with clubfeet in the twenty-first century has gone through a revolution pioneered in the mid-twentieth century: the primary treatment was surgical but now serial manipulation and casting is the mainstay of management. Surgery still has a role in the management of older children with relapsed deformities and especially for recalcitrant and teratologic feet.

The incidence of talipes equinovarus (TEV) varies with ethnicity: 0.4 (Chinese)–1.2 (Caucasians)–6.8 (Polynesians) per 1000 births. The male to female ratio is 2.5:1. Fifty per cent of cases show bilateral involvement and in 24% there is a positive family history. These factors indicate a polygenic inheritance. See Box 13.21.1.

Although the aetiology of idiopathic clubfoot remains unknown, there are numerous theories regarding its development. Intrauterine moulding as a cause of clubfoot was first proposed by Hippocrates and whilst it may play a role in some cases, the evidence from antenatal ultrasound scans is that most TEV deformities are identifiable early in pregnancy in the presence of adequate amniotic fluid.

Histological studies have identified abnormalities both in the muscles and in the medial ligaments with an increase in connective tissue content and a greater number of myofibroblasts. A higher prevalence of type 1 muscle fibres in affected feet compared to unaffected feet has been noted. One study found a significant reduction in the number of anterior horn cells in the affected side of stillborn fetuses with unilateral clubfoot but as with much of this work it does not distinguish between cause and effect. Subtle abnormalities have been identified on neurophysiological testing.

Contrary to popular belief, there is no known association with hip dysplasia.

Investigations into the genetic influences on TEV have progressed rapidly and are based on Hox genes involved in limb bud development. Chromosomal deletions (2q31–33) and candidate genes such as CASP8 and 10, and CFLAR that encode protein regulators of apoptosis during growth and development have been associated with clubfoot.

TEV found in association with other conditions is referred to as teratologic or syndromic TEV rather than idiopathic (Box 13.21.2).

The essential deformities are a displacement of the navicular, os calcis, and cuboid around the talus, characterized by hindfoot equinus, internal rotation with varus and adduction, and supination of the forefoot (Figure 13.21.1).

The key to understanding the TEV deformity is to consider that the talus is firmly held by the ankle mortise and to assess the remainder of the foot in relation to the talus. Thus, the essential deformity is that the os calcis is internally rotated beneath the talus. In order to achieve this position it must assume an equinus and varus posture. The remainder of the foot is attached to the os calcis through the cuboid and the navicular allows rotation of the forefoot around the talar head. With the os calcis internally rotated, the forefoot must be in an adducted and supinated position. The metatarsals are joined in the transverse plane but there is independence of the medial and lateral columns in the sagittal plane and the first metatarsal often adopts a plantar flexed posture which explains the cavus deformity of the medial foot.

In addition to the abnormal bony architecture, the soft tissues are frequently abnormal and vascular studies have identified abnormalities in the arterial supply in patients with TEV.

The limb below the knee is thinner than normal and both the foot and the lower leg are usually short. The degree of shortening reflects the severity of the initial deformity.

Classification systems are of value in providing a prognosis to parents and for comparing the results of treatment between centres. There have been numerous attempts to classify clubfeet but the most popular in use today are those described by Pirani and Dimeglio. The Pirani system is based on 6 criteria: 3 each from the hindfoot and forefoot. Each criteria is graded 0, 0.5 or 1, giving a maximum score of 6 for each foot. The Dimeglio system scores each foot out of 20 points and then assigns it a grade. Both systems can be used for sequential assessments to monitor treatment and to predict the need for tenotomy when using the Ponseti method of treatment.

The earliest documented treatment for TEV, in 1000BC, was massage and Hippocrates (circa 400BC) recommended treating the foot as near to birth as possible using gentle serial manipulations and fixation, aiming for over-correction. Special shoes were worn afterwards to help prevent relapse and maintain correction.

Surgery became a part of treatment in the eighteenth century and became increasingly common and increasingly aggressive during the twentieth century due to disillusionment with the protracted nature of the contemporary casting techniques such as that advocated by Kite. In time, however, it became apparent that the results following an aggressive surgical approach were also disappointing and a resurgence of the conservative management of TEV has been seen.

Kite’s view was that the fulcrum for correction of the clubfoot was the calcaneocuboid joint but correction at this site results in a midfoot break through the metatarsal–tarsal articulation. Ponseti has shown clearly that the fulcrum for correction is the lateral head of the talus and hence he developed his method of correcting a clubfoot by serial stretching and casting according to the principles of Hippocrates. The description was first published in 1963 but it took over 30 years for the method to be adopted by other surgeons.

The method consists of weekly manipulations during which the foot is stretched gently according to a well-defined sequence. After stretching, the foot is placed in a plaster cast to maintain the position that has been achieved. The procedure is repeated until correction is achieved. This takes approximately 6 weeks but varies depending on the flexibility of the foot (Figure 13.21.2).

Firstly the cavus of the first ray is elevated and the foot assumes a supinated position. This ensures that the metatarsals are in the same plane. The foot is then progressively abducted in the plane of the metatarsals, the effect of which is to correct the adduction deformity of the forefoot and additionally the internal rotation of the os calcis. As the abduction progresses the forefoot drives the os calcis from its position of internal rotation beneath the talus to its reduced position thus correcting the varus and part of the equinus deformity.

It is important to over correct the forefoot to 70 degrees of abduction to ensure accurate reduction of the hindfoot. As the forefoot abducts it adopts a more pronated position because of the change in position of the os calcis relative to the talus. Forced pronation should never be used as it recreates the original cavus deformity by plantar flexing the first ray thus locking the foot and preventing hindfoot correction.

The final correction required is the residual ankle equinus. Approximately 25% of feet correct completely with further stretching but most will not. If ankle dorsiflexion of 10–15 degrees cannot be achieved, a tenotomy is required. This can be done simply in the clinic under local anaesthesia. In 5% of cases insufficient dorsiflexion is achieved and surgery is required to gain complete correction. This can usually be achieved by a posterior release of the ankle capsule but in a few feet more radical soft tissue surgery is required. Following complete correction, the foot is held in a final cast for 3 weeks and then the child is treated with boots on a bar to maintain the correction (Figure 13.21.3). For the first 3 months, the boots are worn for 23 hours a day and then at ‘night time and nap time’ until the age of 4 years.

Pirani’s elegant MRI study showed that the cartilaginous deformities of the clubfoot correct with progressive manipulation and casting.

Cooper and Dietz published a 30-year follow up on 29 of Ponseti’s original group of 45 patients. The functional results did deteriorate over time but at 30 years, 78% of feet were rated as excellent/good with a supple, plantigrade foot. Relapse occurred in 50% overall but was treatable by repeated casting, with or without a further Achilles tenotomy and with a transfer of the anterior tibialis tendon in those feet with a supination deformity. Long-term results are better in those with a sedentary occupation and who are not overweight.

The true success of a procedure is whether the results can be repeated by others: initial reports failed to produce satisfactory results, invariably due to inaccurate casting techniques; however, with strict adherence to the Ponseti method, good results have been published from many centres. Relapse rates are significantly higher with poor brace compliance and although they may be treated by reapplication of the Ponseti method, compliance may still be a problem and open surgery is often necessary. A complete correction of the deformities is essential to ensure accurate brace fitting which is important to optimize brace compliance. In a series of 62 patients with 3-year follow-up from Southampton the author reports an initial failure rate of 5% and a subsequent relapse rate of 21% successfully treated with repeat casting, Achilles tenotomy or tibialis anterior transfer. All of the relapses occurred in patients with an initial hindfoot Pirani score of 2.5 or 3.0.

The Ponseti method has also been shown to be an effective means of treating clubfeet when performed by non-medical personnel such as physiotherapists and clinical officers in the developing world where facilities for surgery are less established. However, the involvement of a paediatric orthopaedic surgeon is essential to ensure continuity of care and to manage the early failures and recurrences.

Ponseti and others have identified certain atypical feet that behave differently to the standard idiopathic clubfoot. Clinically, they are defined as having rigid equinus, severe plantar flexion of all metatarsals, a deep crease above the heel, a transverse crease in the sole of the foot, and a short and hyperextended first toe. The Achilles tendon is exceptionally tight and fibrotic up to midcalf. In such patients, correction can be achieved by modifying the Ponseti technique and performing an Achilles tenotomy earlier than usual, prior to full correction of the forefoot. This has the effect of releasing the os calcis from under the talus. Casting may then proceed as usual but a further tenotomy may be required as little as 3 weeks later if the equinus cannot be corrected.

With teratologic or syndromic foot deformities, the Ponseti method is less likely to succeed, but it should be attempted and it may reduce the extent of the subsequent surgical release.

There is still a place for soft tissue surgery in the treatment of TEV. All published reports of the Ponseti method have a small, early failure rate and these feet will require a limited posterior or full posteromedial release. In addition there are some families for whom the Ponseti method will not be suitable for logistical reasons. For some, the use of the boots and bar present a major problem and poor compliance amongst certain population groups has been noted. In these patients surgery may be advocated to provide a traditional complete correction with no need for on going orthotic use.

Surgery also has a role in the treatment of relapses. As discussed previously the initial approach to a relapse is to repeat the Ponseti method. If the forefoot is supinating then a transfer of the anterior tibialis muscle is required. On occasion these steps are insufficient and more extensive surgery may be required. If the child is less than 5 years old, a posteromedial release can be performed to restore the orientation of the os calcis beneath the talus. Shortening of the lateral column can be very effective in correcting the adductus deformity that occurs. Several methods are described and include resecting part of the anterior os calcis or cuboid, or fusing the calcaneocuboid joint.

Relapse following surgical release is common: a 9–16-year follow-up study found that almost 80% of Dimeglio grade 4 feet had relapsed. With increasing age and increasingly rigid deformities, the prospect of further open surgery becomes less attractive due to the inevitable increased stiffness and scarring associated with it. For those feet that do require surgical intervention to obtain a plantigrade foot, the use of gradual correction using the principles of Ilizarov avoids the need to perform extensive soft tissue dissection. By using circular frames the complex deformities can be corrected gradually with distraction and fixed or virtual hinges. The Taylor Spatial Frame (TSF) is a circular frame device where the correction is calculated using a web-based software program. Using the principles of the Ponseti method, an olive wire inserted into the head of the talus can be used as a fulcrum to correct the deformity in the same way as the thumb is used in a standard manipulation.

TEV is relatively common affecting approximately 1 in 1000 live births. The optimal contemporary management is the Ponseti method of sequential manipulation and casting followed by maintenance of the correction by boots and bar for approximately 4 years. Ideally, treatment starts as soon after birth as possible but it can still be used for delayed presentations. The same approach is used for relapses that occur in approximately 20–30% of cases and a transfer of the anterior tibialis muscle may be required to treat supination of the forefoot. Soft tissue surgery may still be necessary for initial failures, for relapses and teratologic feet. Gradual correction using circular frames is one method of treating difficult deformities without the need for open surgery and the risk of associated fibrosis.