Atypical Club Foot
- Atypical clubfeet have severe equinus and plantarflexion of all metatarsals and a short hyperextended great toe
- Atypical clubfeet are challenging to treat
- Initial treatment with the modified Ponseti method can be successful, but relapses and complications are frequent
Description:Atypical clubfeet or complex idiopathic clubfeet are defined by Ponseti 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 hyperextended first toe.” (Ponseti, 2006) While typical idiopathic clubfeet respond well to the standard method of Ponseti casting and generally correct after 4-6 casts, atypical clubfeet are resistant to correction and standard manipulation and casting may lead to worsened deformity. Turco noted that these feet respond differently to operative and nonoperative treatment and warned that early surgery can result in a grotesquely deformed foot (Ponseti, 2006). While they may also be difficult to treat, arthrogrypotic, syndromic, and neuromuscular clubfeet are excluded from the definition of atypical or complex idiopathic clubfeet.
Epidemiology:A small percentage of idiopathic clubfeet are classified as atypical. In Ponseti’s series 6.5% of idiopathic clubfeet were atypical and 68% of these occurred in boys. (Ponseti, 2006)
Clinical Findings:Complex idiopathic clubfeet are distinguished by significant shortening, rigid equinus with a deep crease above the heel, severe plantar flexion of all metatarsals with a deep plantar crease across the full width of the sole of the foot and high cavus, and a short and hyperextended big toe; with a normal neurologic examination. The Achilles tendon is long and wide with the gastrocsoleus muscle bunched in the proximal third of the calf. The anterior calcaneus is prominent dorsolaterally and in contact with the small and often difficult to palpate talar head. The navicular is displaced medially contacting the medial malleolus (Ponseti, 2006; Matar, 2017). Two-thirds of patients with atypical clubfeet demonstrate anterolateral bowing of the tibia, and there is a greater size discrepancy in unilateral atypical clubfoot compared to the unaffected contralateral foot than is usually seen in unilateral idiopathic clubfoot (Matar, 2017).
Imaging Studies:Radiographs may be used to evaluate atypical clubfeet. The talocalcaneal angle is generally parallel on both the AP and lateral views. The cuboid is displaced medially. There is severe plantarflexion of the talus, calcaneus, and all metatarsals, especially the first metatarsal. In patients who have developed abduction of the forefoot after attempted casting, the metatarsals may be hyperabducted at the tarsal-metatarsal joins with up to 90 degrees of plantarflexion. (Ponseti, 2006)
Treatment:The modified Ponseti method is an effective first line treatment for atypical clubfoot, but it requires an increased number of casts and an increased rate of relapse and surgical releases have been reported (Matar, 2017). Ponseti described modifying the usual protocol to treat atypical clubfoot. The subtalar joint and head of the talus must be precisely identified, which may be difficult due to the prominent anterior process of the calcaneus. Once identified, place the thumb over the talar head and index finger on the posterior aspect of the lateral malleolus and then gently abduct the foot with the other hand. Care should be taken not to over abduct the forefoot. Once the forefoot abduction is corrected, the plantarflexion of all metatarsals is addressed by grasping the ankle with both hands and dorsiflexing the foot with both thumbs while an assistant supports the knee in flexion. The knee should be casted in at least 110 degrees of flexion to prevent cast slippage. Percutaneous Achilles tenotomy is performed after plantarflexion of the metatarsals has been corrected. The site chosen is 1.5cm above the posterior skin crease as opposed to the traditional 1cm to avoid injury to the proximally positioned posterior tuberosity of the calcaneus. A second Achilles tenotomy may be required for some patients with serial casting following until five degrees of dorsiflexion and no more than 40 degrees of abduction are obtained. At this point abduction bracing is initiated with a soft 3-strap sandal attached to the bar at 40 degrees of external rotation (Ponseti, 2006). Higher rates of relapse and risk factors for relapse of the more severe clubfoot have been identified (Sangiorgio 2017).
Complications:Atypical clubfeet do not correct with the standard Ponseti method. Frequent cast slipping may cause foot edema, bruising, and skin breakdown. Ponseti reported a 22% complication rate with his modified method including erythema, swelling of the forefoot and toes, mild rocker-bottom deformity, midfoot hyperabduction, and repeated downward cast slippage. Relapse rate at 2 years was 14%, and most frequently attributed to difficulty with ill-fitting shoes during abduction bracing (Ponseti, 2006). Using the modified Ponseti method, Matar found 53% relapse at 7 years average follow up (range 3-11 years) (Matar, 2017).
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