Triple arthrodesis is considered as a late salvage-stabilising procedure that relieves pain but sacrifices joint motion. If the subtalar or midtarsal joints are arthritic and painful, a triple arthrodesis will allow correction and pain control. The trend for triple fusion in the younger HMSN has fallen out of favour of late.
Levitt (1973) studied 15 children with HMSN or Freireich’s ataxia and concluded that ‘triple arthrodesis must eventually be performed in every patient who has a significant degree of deformity’, finding that soft tissue procedures did not last.
Subsequently however, two long-term studies by Wukich (1989) and Wetmore (1989) – 14 and 21 years average follow up, respectively, found unsatisfactory results of early fusion and recommended it as a salvage procedure. In Wetmore's series, 7/30 feet had recurrent cavus deformity, six had extended fusions of OA, eight had painful calluses and, overall, 14/30 had poor functional results. Relatively few tendon transfers were done at the time of fusion.
The ‘beak’ triple arthrodesis propsed by Siffert (1983) is adapted to correct severe varus. Cutting a beak into the talar head under which the navicular can be slotted, can allow better correction of forefoot equinus. Occasionally excision of the entire navicular may be necessary, with displacement of the cuneiforms under the talar beak. Complications of the procedure include over pronation of the forefoot due to excessive plantar depression of the first metatarsal and shortening the foot.
A deformed or arthritic ankle usually needs a fusion as the combination of deformity and neuropathy increase the risks of ankle replacement. There is usually hindfoot deformity as well, in which case, tibiotalocalcaneal fusion with retrograde nail fixation is required. This is performed through a lateral transfibular or double approach.