Abstract
BackgroundHypothyroidism has been independently associated with the development of several comorbidities and is known to increase complication rates in non-spinal surgeries. However, there are limited data regarding the effects of hypothyroidism in major spine surgery. Therefore, we present the largest retrospective analysis evaluating outcomes in hypothyroid patients undergoing spinal fusion.MethodsA retrospective review of the National Inpatient Sample (NIS) from 2004-2014 was performed. Patients with an International Classification of Diseases, 9th revision, Clinical Modification (ICD-9-CM) procedure code indicating spinal fusion (81.04-81.08, 81.34-81.38, 81.0x, 81.3x) were included. Patients with an ICD-9-CM diagnosis code indicating hypothyroidism (244.x) were compared to those without. Cervical and lumbar fusions were evaluated independently. Significant covariates in univariable logistic regression were utilized to construct multivariable models to analyze the effect of hypothyroidism on perioperative morbidity and mortality.ResultsA total of 4,149,125 patients were identified, of which 9.4% were hypothyroid. Although, hypothyroid patients had a higher risk of hematologic complications (lumbar - odds ratio [OR] 1.176, p < 0.0001; cervical - OR 1.162, p < 0.0001), they exhibited decreased in-hospital mortality (lumbar - OR .643, p < 0.0001; cervical - OR .606, p < 0.0001). Hypothyroid lumbar fusion patients also demonstrated decreased rates of perioperative myocardial infarction (MI) (OR .851, p < 0.0001). All these results were independent of patient gender.ConclusionsHypothyroid patients undergoing spinal fusion demonstrated lower rates of inpatient mortality and, in lumbar fusions, also had lower rates of acute MI when compared to their euthyroid counterparts. This suggests that hypothyroidism may offer protection against all-cause mortality and may be cardioprotective in the postoperative period for lumbar spinal fusions independent of patient gender.
Highlights
The population of the United States has been increasing over the last several decades and, in turn, the prevalence of chronic illnesses has risen
Hypothyroid patients had a higher risk of hematologic complications, they exhibited decreased in-hospital mortality
Hypothyroid lumbar fusion patients demonstrated decreased rates of perioperative myocardial infarction (MI) (OR .851, p < 0.0001). All these results were independent of patient gender
Summary
The population of the United States has been increasing over the last several decades and, in turn, the prevalence of chronic illnesses has risen. Hypothyroidism, which carries a prevalence of approximately 1%-4% in the US and has been independently associated with the development of hypertension, cardiovascular disease, osteoporosis, peripheral neuropathy, muscular weakness, and increased complication rates in non-spinal surgeries, has had only a limited number of studies suggesting that it confers increased perioperative risk in patients undergoing major spine surgery [2,3,4,5,6,7,8,9,10]. Hypothyroidism has been independently associated with the development of several comorbidities and is known to increase complication rates in non-spinal surgeries. We present the largest retrospective analysis evaluating outcomes in hypothyroid patients undergoing spinal fusion
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