4/11/2016 | by Pooya Hosseinzadeh, MD
Minimally Invasive Method for Treatment of Congenital Vertical Talus (Dr. Matthew Dobbs Interview)
*Dr. Dobbs is a Professor of Orthopedic Surgery and director of Strategic Planning at Department of Orthopedic Surgery in Washington University School of Medicine in St. Louis, MO
1. Can you please tell us how you came up with the minimally invasive method for treatment of CVT?
My treatment method for congenital vertical talus evolved from the Ponseti method for clubfoot management. Early in my practice, I saw patients with clubfoot that I was treating with the Ponseti method while treating congenital vertical talus with more extensive surgery. This did not make sense to me and I thought there must be a better way, a gentler way of correcting vertical talus as well. Ironically, after I published on a gene discovery for vertical talus, I started seeing many more vertical talus patients referred to me for treatment. This relatively large volume of patients that came to me allowed me to develop the casting method, which would have been much harder to do seeing only a few patients a year.
2. Can you please describe your technique?
A key to my vertical talus minimally invasive technique lies in the ability to palpate the head of the talus just as it is with clubfoot. This can be challenging in the small infant foot. The principle of manipulation relies on the fact that the talus is fixed in the ankle mortise but the rest of the foot including the subtalar joint complex can rotate around the head of the talus. The method of gentle and serial casting is performed in the clinic on a weekly basis. It takes an average of 5 casts to achieve correction. Once correction is achieved, it is maintained with pin fixation of the talonavicular joint and a tendo Achilles tenotomy. While clubfoot uses the head of the talus as a fulcrum to externally rotate the foot, my method for vertical talus correction uses the head of the talus as a fulcrum to reduce the talonavicular joint while bringing the foot into plantar flexion and adduction. It is key to apply both a dorsal and lateral force on the talus to correct not only the lateral plane deformity, but also the coronal plane deformity. I realized early in the evolution of this technique that I achieved very good correction on the lateral x-ray by pushing dorsally on the talus, but I was not paying attention to residual deformity on the AP x-ray. That residual deformity was an increased AP talocalcaneal angle resulting in residual hindfoot valgus. This is when I evolved the technique to include a more lateral push on the talus as well as dorsal. The lateral push narrows the AP talocalcaneal angle correcting hindfoot valgus at deformity.
The other keys to the technique are to cast gradually into maximal equinovarus deformity to reduce the talonavicular joint. This is analogous to achieving 70˚ of external rotation in the final Ponseti cast for clubfoot correction. The maximal equinovarus position is essential to overcorrect the deformity in order to adequately stretch the dorsal and lateral soft tissues. If this is not done, there will either be lack of full correction or high relapse risk. Another key aspect is performing the tendo achilles tenotomy only after the talonavicular joint is reduced and stabilized with a Kirschner wire in the operating room. If the tenotomy is performed without stabilizing the talonavicular joint then reduction will be lost with dorsiflexion of the ankle. After correction is achieved in the operating room, the foot is casted in neutral in terms of forefoot rotation as well as neutral in terms of ankle dorsiflexion. The cast is changed at two weeks to ensure that the pin is not migrating out as well as to stretch the ankle. A final cast is placed with the foot and ankle in neutral for another four weeks. The pin is then removed at the end of the six week period. After the last cast is removed, the parents are instructed on stretching exercises emphasizing plantar flexion and adduction. The patient then goes into a shoe and bar brace system similar to that for clubfoot. However, in the brace the vertical talus foot is pointed straight ahead rather than externally rotated and, if using a static bar, the bar is not bent into dorsiflexion as it is in clubfoot. The bracing is used full-time for two months and then at nighttime for two years.
3. Can you please share your clinical results with us?
The clinical results of my method of vertical talus correction have been excellent. We have reported now a 10 year follow-up showing maintenance of correction and excellent mobility when comparing to a similar cohort treated with more extensive soft tissue release operation. This is an analogous to that seen when comparing the Ponseti method to soft tissue release for clubfoot deformity. A longer follow-up is of course necessary to ensure maintenance of this correction into adulthood though the early and midterm results are very promising. I have achieved these results both in isolated vertical talus deformity as well as in syndromic vertical talus. As one can imagine, the syndromic and neuromuscular vertical talus are more challenging, often require more casts, and sometimes require selective soft tissue release surgery. When surgery of the soft-tissues is necessary it is much less invasive than traditional vertical talus surgery due to the correction achieved with the casting protocol.
Others have reproduced excellent results with my method and there are more than ten articles in the literature demonstrating the treatment efficacy in patients from around the world.
4. What do you see as the struggles with this method?Are there any feet that are not suitable for this technique?
The struggles with this method I have tried to highlight above and most are related to the fact that there is a learning curve to becoming proficient with the technique. The most significant challenge as in clubfoot is being able to palpate the head of the talus accurately in an infant’s foot. If one is not able to palpate the head of the talus, the manipulative technique will be flawed and correction will not be achieved. Another caveat is achieving the maximal equinovarus before going to the operating room to adequately stretch the dorsal lateral soft tissues to minimize the risk of relapse. As mentioned above, this is analogous to achieving 70˚ of external rotation in clubfoot treatment management. Another pearl lies with K-wire fixation. It can be difficult in an infant’s foot to ensure that the pin is across the talonavicular joint as the talus and navicular are quite cartilaginous at this young stage, and pin placement can be tricky even under fluoro guidance. The pin should also be buried to prevent pin migration. A smooth Kirschner wire in an infant’s foot can have the tendency to migrate out underneath the cast, and if this happens a reduction may be lost.
To answer the question in terms of are there any feet not suitable for this technique, the answer is “no” and this is my same answer for clubfoot management with the Ponseti method. There is no foot that will not benefit from the casting method. This does not mean that all feet can achieve a full correction without some surgery involved, but all feet will gain some benefit making any surgery necessary a more thoughtful a la carte procedure rather than a blanket extensive soft tissue release operation.