American Association for Hand Surgery

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Impact of Body Mass Index and Patient Comorbidities on Outcomes in Upper Extremity Nerve Transfers
Linden K Head, MD, HBA, BSc, BPHE1, Maria C M├ędor, BHSc2, Aneesh Karir, BHSc2, Gerald Wolff, BSc, MD, FRCSC3 and Kirsty U Boyd, BHSc, MD, FRCSC4, (1)Division of Plastic and Reconstructive Surgery, University of Ottawa, Ottawa, ON, Canada, (2)University of Ottawa, Ottawa, ON, Canada, (3)Division of Physical Medicine and Rehabilitation, University of Ottawa, Ottawa, ON, Canada, (4)Division of Plastic and Reconstructive Surgery, Ottawa, ON, Canada

INTRODUCTION: An understanding of the injury features, patient factors, and patient goals are important in selecting the optimal treatment in the context of peripheral nerve injuries. While robust work has been done to elucidate prognostic features of nerve injuries there remains a paucity of evidence addressing the influence of patient factors such as comorbidities. The objective of this study was to evaluate the impact of body mass index (BMI) and comorbidities on the clinical outcomes of upper extremity nerve transfers.

MATERIALS & METHODS: The study design was a retrospective cohort of prospectively collected data. Medical records were reviewed for all patients undergoing nerve transfer surgery by a single surgeon (2012-2018). Patients were eligible for inclusion if they had undergone an upper extremity nerve transfer with a minimum of 12-months follow-up. Data was collected by two independent reviewers regarding demographics, comorbidities, injury etiology, nerve transfer, as well as preoperative and postoperative clinical assessments. The primary outcome measure was postoperative strength of the recipient nerve innervated musculature (Medical Research Council [MRC]). Statistical analysis used descriptive statistics and non-parametric tests.

RESULTS: Thirty-eight patients undergoing 43 nerve transfers were eligible for inclusion. Patients had a mean age of 48.8 years and mean BMI of 27.4 kg/m2. Injuries involved the brachial plexus (32%) or its terminal branches (68%) and the most common etiologies were trauma (50%), compression (26%), and brachial neuritis (21%). Anterior interosseous nerve to ulnar motor nerve (35%) was the most common nerve transfer performed. Patients with acute etiologies underwent surgery a mean of 6.7 months following their injury and those with chronic compression underwent surgery a mean of 20.7 months following onset of symptoms. With a mean follow-up of 20.1 months following nerve transfer surgery, the mean MRC increased significantly (p=0.000) from 1.0 to 3.3. Increased BMI was significantly associated with poorer postoperative strength in the recipient nerve innervated musculature (r=-0.320, p=0.036). Mean postoperative MRC amongst active smokers (2.6) was significantly lower (p= 0.021) than non-smokers (3.6). There were no significant differences in outcomes based on the presence of other comorbidities.

CONCLUSIONS: This retrospective cohort study demonstrated that increased BMI and smoking may be associated with worse outcomes in upper extremity nerve transfers. To facilitate patient selection and guide expectations regarding prognosis, further experimental and clinical work is warranted to understand the potential influence of BMI and smoking on recovery following nerve injury and nerve transfer surgery.

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