Vitamin D Deficiency and Outcomes after Ankle Fusion

Abstract

Category: Ankle Arthritis; Ankle; Basic Sciences/Biologics; Hindfoot Introduction/Purpose: Ankle fusions are associated with a complication profile including nonunion with associated poor functional outcomes, chronic pain, and need for reoperation. Local risk factors (bone and soft-tissue loss, infection, ankle and hindfoot deformity, and neuropathy) and systemic risk factors (advanced age, smoking, alcohol abuse, worker’s compensation, noncompliance, obesity, and systemic comorbidities such as diabetes and immunodeficiency) have been shown to be associated with the development of a nonunion following fusion procedures. Vitamin D has an important role in bone healing, and vitamin D deficiency has been proposed as a potential risk factor for the development of non-unions. The purpose of this study is to assess the impact of low vitamin D levels on reoperation rates and the development of nonunions following ankle fusion surgery. Methods: A retrospective chart review of all ankle fusions performed at a major health system from January 2010 to July 2019 was performed. In total, 240 ankle fusions were performed by seven surgeons. All patients who underwent primary fusion procedures were eligible for inclusion in this study. Exclusion criteria included: age less than 18 years; revision surgery; ankle fusion with the use of bulk allograft; ankle fusion performed as part of an oncologic reconstruction; and an absence of recorded vitamin D levels with 12 months of surgery. In total, 47 patients met inclusion criteria and formed the study group. In this group, 29/47 (61.7%) were female and 18/47 (38.3%) were male. Average age was 57.0 +- 12.3 years (range: 18.6 to 75.7). Patients were grouped according to their vitamin D levels as being deficient (<31 ng/ml) or normal (31-80 ng/ml). Results: Prevalence of vitamin D deficiency was 36.2% (17/47) at average of 35.7 ng/ml. In vitamin D deficient subgroup (n=17), average vitamin D level was 16.9 ng/ml. In normal vitamin D subgroup (n=30), average vitamin D was 46.4 ng/ml. Overall, reoperation rate was 21.3% (10/47). Reoperation rate was 35.3% (6/17) in vitamin D deficiency subgroup compared with 13.3% (4/30) reoperation rate in normal vitamin D subgroup (p<0.05). In vitamin D deficient subgroup, 5 procedures for nonunion included: dynamization (n=1), revision fusion (n=1), staged revision (n=2) and amputation (n=1) due to infected nonunion. There was also a symptomatic hardware removal. In normal vitamin D subgroup, reoperation indications included: malunion (n=1), elective dynamization before weightbearing (n=1), and symptomatic hardware removal (n=2). Normal vitamin D subgroup had zero nonunions. Conclusion: In patients undergoing ankle fusion, vitamin D deficiency (< 31 ng/ml) was associated with a reoperation rate over double that of patients with normal vitamin D levels. In the vitamin D deficient subgroup, nearly all reoperations were for nonunion as compared to zero nonunion incidence in those with normal vitamin D levels. These results suggest routine preoperative screening of vitamin D level is indicated as a key component of ankle fusion care. Vitamin D supplementation during the perioperative period may be indicated in regions with low sunlight to improve fusion rates and lower the risk of reoperation.