Treatment and Outcomes of Atraumatic Subtalar Dislocations in Adult Acquired Flatfoot Deformity

Abstract

Category: Ankle; Hindfoot Introduction/Purpose: Painful adult acquired flatfoot is classified into multiple types, with a one category reserved for those that have rigid deformity. However, there is a subset of patients with rigid progressive collapsed foot deformity (PCFD) in which navicular and calcaneus are subluxed from the talus causing sub-fibular impingement and erosion and fixed abduction of the forefoot. This condition is not well described in the literature. The treatment of these patients can be technically difficult given the attenuation and erosion of soft tissue and articular constraints. In this study we sought to identify reduction technique, shared characteristics, treatments, and outcomes in patients with severe hindfoot valgus deformity with subluxation and subfibular impingement who were treated by subtalar reduction and arthrodesis, and talonavicular arthrodesis at a single institution. Methods: A retrospective chart review was done of all patients who underwent flat foot reconstruction by a single surgeon. Patient were included in the study if on preoperative weight-bearing (WB) CT they met the following radiographic criteria: 3 sequential sagittal cuts of the calcaneus without the talus present, 3 sequential sagittal cuts of the talus without the calcaneus present, and the presence of a calcaneofibular articulation on coronal cuts. Patients with neuromuscular disorders or peripheral neuropathy were excluded. This review evaluated demographic data, comorbidities, complications, and the need for reoperation. Plane radiographs and CT findings were compared to identify subluxation on plane images. Patients were treated with a double, triple, or pantalar arthrodesis based on the treating surgeon’s discretion. A cohort of 23 patients has already been identified, but additional data review is currently underway. Results: The initial patient cohort consisted of twenty-three patients who met the inclusion criteria with an average age of 64.5 (range, 48-79) years. The initial cohort consisted of patients who were treated from 2009-2014. Seven of the twenty-three patients (30.4%) required reoperation for various reasons ranging from late infection to nonunion and symptomatic hardware (Table 1). We found that the average BMI for patients with this disorder was 34kg/m 2 . Four patients have fibular stress fractures on presentation, these patients had an average BMI of 41.6kg/m 2 . Specific techniques for reduction included use of distractors at subtalar and TN joints. Radiographic findings on plane films are linked to findings on CT scan. Recurrence of deformity occurred with tilt of the talus requiring bracing in 2 patients. Incomplete correction was common, particularly early in the study period. Conclusion: PCFD is a very problem seen by foot and ankle surgeons. Physicians should be aware of the challenges presented in treating the subset of patients who have atraumatic dislocation of the subtalar joint. Diagnosis can be made on plane radiographs, though WB CT is useful for treatment planning. Treatment of these patients requires careful physical and radiographic examination. Reduction and arthrodesis is the treatment of choice. Patients should also be counseled about the possible need for reoperation given the high rate of reoperation in this population.