Background: While nonunion after foot and ankle fusion surgery has been associated with poor outcomes, we are not aware of any longitudinal study on this subject. Thus, we prospectively evaluated the impact of nonunion on clinical outcomes of foot and ankle fusions and identified potential risk factors for nonunion after these procedures.
Methods: Using data from a randomized clinical trial on recombinant human platelet-derived growth factor-BB (rhPDGF-BB; Augment Bone Graft, BioMimetic Therapeutics), union was defined either by assessment of computed tomography (CT) scans at 24 weeks by a reviewer blinded to the type of treatment or by the surgeon’s composite assessment of clinical and radiographic findings at 52 weeks and CT findings at 24 or 36 weeks. The nonunion and union groups (defined with each assessment) were then compared in terms of clinical outcome scores on the American Orthopaedic Foot & Ankle Society Ankle-Hindfoot Scale (AOFAS-AHS), Foot Function Index (FFI), and Short Form-12 (SF-12) as well as age, sex, body mass index (BMI), smoking status, diabetes status, work status, and arthrodesis site.
Results: Blinded CT assessment identified nonunion in 67 (18%) of 370 patients, and surgeon assessment found nonunion in 21 (5%) of 389 patients. Postoperatively, the nonunion group scored worse than the union group, regardless of the method used to define the nonunion, on the AOFAS-AHS and FFI, with mean differences of 10 and 12 points, respectively, when nonunion was determined by blinded CT assessment and 19 and 20 points when it was assessed by the surgeon. The nonunion group also had worse SF-12 Physical Component Summary scores. Differences between the union and nonunion groups were clinically meaningful for all outcome measures, regardless of the nonunion assessment method. The concept of an asymptomatic nonunion (i.e., imaging indicating nonunion but the patient doing well) was not supported. Patients with nonunion were more likely to be overweight, smokers, and not working.
Conclusions: This prospective longitudinal study demonstrated poorer functional outcomes in patients with a nonunion after foot and ankle fusion, regardless of whether the diagnosis of nonunion was based on CT only or on combined clinical, radiographic, and CT assessment.
Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
1Department of Orthopaedic Surgery, Inselspital, University of Bern, Bern, Switzerland
2Department of Orthopaedics, University of British Columbia, Vancouver, British Columbia, Canada
3BC’s Foot and Ankle Clinic, St. Paul’s Hospital, Vancouver, British Columbia, Canada
4Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, Rochester, New York
5Division of Orthopaedic Surgery, St. Michael’s Hospital and University of Toronto, Toronto, Ontario, Canada
6Dalhousie University, Halifax, Nova Scotia, Canada
7Queen Elizabeth II Health Sciences Center, Halifax, Nova Scotia, Canada
8Division of Foot and Ankle Surgery, Department of Orthopaedic Surgery, Massachusetts General Hospital and Newton-Wellesley Hospital, Waltham, Massachusetts
9Department of Orthopaedic Surgery and Rehabilitation, Loyola University Health System, Maywood, Illinois
10Foot & Ankle Service, Department of Trauma & Orthopaedics, Tan Tock Seng Hospital, Singapore
11Wright Medical N.V., Franklin, Tennessee
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