Tibial Stress Fracture After Ankle Arthrodesis: Case Series with Different Treatment Modalities

CATEGORY: Ankle, Ankle Arthritis, Trauma INTRODUCTION/PURPOSE: End-stage ankle arthritis is frequently treated with tibiotalar or tibio-talar-calcaneal (TTC) arthrodesis, whose sequelae include adjacent joint arthritis presumptively due to the increased stress inherent to the loss of a motion segment. The loss of ankle motion may also stress the distal tibia, and individual case reports exist describing tibial stress fracture after ankle arthrodesis. These case reports do not describe operative treatment however. The purpose of this study is to report a case series of patients who presented with a stress fracture of the tibia after ankle arthrodesis, a subsegment of whom failed nonoperative management, highlighting related risk factors and treatment strategies. METHODS: The medical records at two large academic medical centers were reviewed retrospectively, from 1990 to 2017 at the first center and from 2013 to 2017 at the second center, to identify patients who had undergone ankle arthrodesis. Any patient who subsequently developed a stress fracture of the tibia, confirmed clinically and/or radiographically, was included in the subsequent analysis. Patients with a history of stress fracture prior to arthrodesis or with non-tibia stress fractures were excluded. Patient demographics were collected alongside surgical technique, duration of postoperative non-weight bearing status, presence of medical co-morbidities including osteoporosis and tobacco use, location of tibial stress fracture, and treatment strategy. RESULTS: Twelve patients out of 988 (1.2%) developed tibial stress fracture. Seven patients underwent isolated ankle arthrodesis, four underwent ankle arthrodesis subsequent to subtalar fusion with a resultant ankle nonunion in two requiring revision TTC nailing, and one underwent primary TTC arthrodesis. Four patients had fibular osteotomy, and four had the lateral malleolus resected. The stress fracture was at the level of fibular osteotomy in two patients, and at the proximal end of existing or removed implant in six patients. All patients were treated initially with immobilization and activity modification except for one who had fracture displacement and underwent immediate plate fixation, and three who failed to improve with nonoperative treatment required fixation (two intramedullary nails, one plate). CONCLUSION: Tibial stress fractures can occur after an isolated ankle arthrodesis but is likely potentiated in the setting of previously or concomitantly fused subtalar joint. Transition points are especially at risk, either at the proximal end of an implant or at the proximal extent of a fibular osteotomy. Critically, stress fractures may present many years after ankle arthrodesis, with an average of four years in this series. In our series one third of patients necessitated surgical management, underscoring the importance of accurate diagnosis. Ultimately patients appear to do well with surgical repair even if they fail initial nonoperative treatment.