Augmentation of Internal Fixation With Multiplanar External Fixator in High Risk Hind Foot Fusion Patients
Authors: Kelly Meghan , Whitlow Scott R. , Cassinelli Spenser J. , Lundeen Gregory A. 
Published: November 2020

Category: Hindfoot; Ankle; Diabetes Introduction/Purpose: Achieving adequate fixation is a critical component for successful fusion. Internal fixation can be compromised in the setting of poor bone quality due to open trauma, infection, osteoporosis, neuropathic arthropathy resulting in published ankle non-union rates of 38% in high risk patients. These failures may be magnified by weightbearing non-compliance. While the use of multiplanar external fixation (MEF) alone can be utilized - it can often require an extended period of time within the frame (mean 18 weeks, range 9-28 weeks) and complications such as pin site infections. We hypothesized that hybrid fixation, MEF in conjunction with internal fixation, will provide adequate stability elevating the fusion rates in complex fusion cases while allowing early weight bearing and reduces the MEF time and infection rate. Methods: Eleven patients were identified that demonstrate significant risk factors for a successful fusion (infection, charcot, neuropathy, smoking, history of non-union) that were treated with internal fixation augmented with MEF. Patients with an active infection underwent surgical irrigation and debridement, placement of an antibiotic spacer and a course of intravenous antibiotics six weeks prior to placement of internal fixation. In these cases, MEF was placed at the time of surgical irrigation and debridement to allow for stability. In those patient’s without an active fixation, both the internal fixation and MEF were placed at the same time. Internal fixation construct was based on surgeon preference. Patients were allowed to transfer weight bear at the time of surgery and could advance as tolerated after 2 weeks. CT was utilized to assess fusion. Outcomes measured were fusion rate and occurrence of internal fixation infection. Results: The mean age of patients was 55 (range 26-75), eight patients had diabetes, three were current smokers, two were former smokers, two patients had open trauma, one patient had peripheral neuropathy and one patient had a history of a non- union with known non-compliance. Six patients had an active infection and underwent irrigation and debridement, placement of antibiotic spacer and MEF during antibiotic treatment. Seven patients underwent intramedullary nail fixation, three patients underwent plate and screw constructs and one patient underwent screw only fixation. CT demonstrated fusion in all patients (100%). The mean time for external fixation was 72 days (range 41-111). There were no cases of infected internal fixation. Conclusion: The findings of the current study suggest high rates of hind foot fusion with the use of internal fixation augmented with MEF in a complex patient group with identified high non-union risk factors. Using internal fixation, patients time in the frame is much reduced than published studies evaluating MEF alone for fusion fixation. MEF did not result in any cases of infected internal fixation. Patients with hybrid fixation also benefit from early weight bearing. We emphasize the importance of good surgical technique and infection management using this technique.