Original Editor - Africa Clubfoot Training Team as part of ICRC and GCI Clubfoot Content Development Project
The “Atypical” Clubfoot, also referred to as Complex Clubfoot in some research, has recently been recognized as a specific Subtype of Clubfoot. It can be treated but it needs a slight modification of the usual Ponseti Technique, and specific attention to details.
Recognizing Atypical Clubfoot
- The foot is short and cylindrical: “the short fat foot”
- The first metatarsal is often flexed and the big toe hyperextended
- The foot is tight posteriorly, giving it marked equinus, but less tight medially so there is not so much varus
- There is often a deep transverse crease across the middle of the sole of the foot. This is because the foot is flexed across the middle, the “plantaris” deformity
- The tibia can also appear curved 
Comparison of Normal Idiopathic and Atypical Clubfoot
The normal idiopathic clubfoot is tight medially, while the atypical clubfoot is tight posteriorly and on the plantar aspect. Note also short and hyper extended big toes are common in atypical clubfoot. 
Causes of Atypical Clubfoot
This is not fully understood. Some children are born with an Atypical Clubfoot, but we believe many others become Atypical as a result of poor treatment. If the POP cast slips down, usually between the 2nd and 4th Casting, then the foot is pushed into Equinus and Plantaris, the midfoot flexes in the middle, and can cause swelling and irritation.
Cast slipping may occur because of:
- Too much padding
- Not enough moulding around the Foot and Heel
- Not enough Knee Flexion
- Below-Knee Casts 
Treatment of Atypical Clubfoot
- Recognize it early
- If the foot is very swollen then give it a “Cast Holiday” for 1 - 3 weeks to let swelling settle
- The child’s parent/guardian can be encouraged to massage the foot if you teach them how
- Recommence manipulation and casting after swelling is reduced
- If Cavus deformity recurs during "Cast Holiday", correct Cavus
- The next step of treatment is limited, cautious Midfoot Abduction and elongation of the Plantar Tissues
Foot Abduction is less important than in normal idiopathic clubfoot. The amount of abduction is determined by observing the plantar surface of the foot and feeling for what is happening in the bones of the foot. Over abduction will cause a lateral or transverse crease so 10-20 degrees may be sufficient. Sufficient Abduction has been reached when the anterior process of the Calcaneus can be felt coming out below the lateral head of Talus.
The cast for an atypical clubfoot should maintain the elongation. There should be thin, snug padding and good moulding. The cast should go above the knee, and knee flexion of 100 degrees should be aimed at, to stop the cast slipping down.
Good cast for an atypical clubfoot; note the toes well supported from below but clearly visible. Note the flexed knees to prevent the cast slipping off. 
There is no need to abduct the foot very much in an atypical clubfoot as the talar head is usually covered early. As soon as the talar head cannot be felt and the plantaris is treated then a tenotomy can be done. Sometimes full dorsiflexion is not achieved after the tenotomy and it is worth recasting after a week to gently improve dorsiflexion. 
- A Normal Foot Abduction Brace can be used but the abduction should be reduced to 30 - 40 degrees
- Dorsiflexion can be increased gradually
- A close watch should be kept for recurrence of plantar crease and equinus
- Walking improves the hindfoot but emptiness of the heel can continue for some years
- Warn the parents that there is an increased likelihood of recurrence
- Good results are possible with care 
- Africa Clubfoot Training Project. Chapter 12 Africa Clubfoot Training Basic & Advanced Clubfoot Treatment Provider Courses - Participant Manual. University of Oxford: Africa Clubfoot Training Project, 2017.