Tibial Stress Fracture Following Ankle Arthrodesis.

Background: End-stage ankle arthritis is frequently treated with either tibiotalar or tibiotalocalcaneal (TTC) arthrodesis, but the inherent loss of accommodative motion increases mechanical load across the distal tibia. Rarely, patients can go on to develop a stress fracture of the distal tibia without any antecedent traumatic event. The purpose of this study was to determine the incidence of tibial stress fracture after ankle arthrodesis, highlight any related risk factors, and identify the effectiveness of treatment strategies and their healing potential.

Methods: A retrospective chart review was performed at 2 large academic medical centers to identify patients who had undergone ankle arthrodesis and subsequently developed a stress fracture of the tibia. Any patient with a tibial stress fracture before ankle arthrodesis, or with a nontibial stress fracture, was excluded from the study.

Results: A total of 15 out of 1046 ankle fusion patients (1.4%) developed a tibial stress fracture at a mean time of 42 ± 82 months (range, 3-300 months) following the index procedure. The index procedure for these 15 patients who went on to subsequently develop stress fractures included isolated ankle arthrodesis (n = 8), ankle arthrodesis after successful subtalar fusion (n = 2), primary TTC arthrodesis (n = 2), and ankle arthrodesis subsequent to successful subtalar fusion with resultant ankle nonunion requiring revision TTC nailing (n = 3). Four patients had undergone fibular osteotomy with subsequent onlay strut fusion, and 5 had undergone complete resection of the lateral malleolus. Stress fracture location was found to be at the level of the fibular osteotomy in 2 patients and at the proximal end of an existing or removed implant in 9. Fourteen of the 15 patients had a nondisplaced stress fracture and were initially treated with immobilization and activity modification. Of these, 3 failed to improve with nonoperative treatment and subsequently underwent operative fixation (intramedullary nail in 2; plate fixation in 1). Only 1 of the 15 patients presented with a displaced fracture and underwent immediate plate fixation. All patients reported pain improvement and were ultimately healed at final follow-up.

Conclusion: In this case series review, we found a 1.4% incidence of tibial stress fracture after ankle arthrodesis, and both hardware transition points and a fibular resection or osteotomy appear to be risk factors. Operative intervention was required in approximately 25% of this population, but the majority of tibial stress fractures following ankle fusion were successfully treated nonoperatively, and ultimately all healed.

Level Of Evidence: Level IV, retrospective case series.