The Effect of Body Mass Index on Fluoroscopic Time and Radiation Dose During Intra-articular Hip Injections

Abstract

BackgroundIntra-articular hip injections are commonly performed for both diagnostic and therapeutic interventions. Because of the risk of damage to neurovascular structures, fluoroscopic guidance with injection of contrast material has been established as the gold standard to ensure proper needle placement into the intra-articular space. However, fluoroscopically guided intra-articular hip injections put patients at risk due to radiation exposure. ObjectiveTo examine the relationship between body mass index (BMI) and fluoroscopy time and radiation dose during intra-articular hip injections. DesignRetrospective study. SettingThe study was conducted at an academic orthopedic center. All procedures were performed by physicians board-certified in PM&R and/or with subspecialty certification in sports medicine, or by a trainee under close supervision from an attending physician. ParticipantsAll patients who underwent fluoroscopically guided intra-articular hip injections between the years 2003-2014 with a documented height/weight, fluoroscopy time, and radiation dose. InterventionsAll patients received unilateral or bilateral intra-articular hip injections with fluoroscopic guidance. Fluoroscopy time and dose were recorded. Main Outcome MeasuresThe main outcome measures were fluoroscopy time and radiation dose. A Bonferroni correction was implemented for multiple comparisons, defining statistical significance at P < .01. ResultsA total of 438 subjects (446 injections) were included. Mean fluoroscopy times were 17.4 ± 9.9, 17.5 ± 11.4, and 19.1 ± 13.4 seconds for normal, overweight, and obese body mass (BMI) index groups, respectively, with no significant difference between groups (P = .148). The mean radiation doses were 601 ± 690, 678 ± 558, and 1049 ± 812 mGy-cm2, respectively (P < .001, r = 0.29). There was no association of age (P = .03), needle length (P = .34) or trainee involvement (P = .159) with fluoroscopy time. ConclusionThis study demonstrates that increasing BMI leads to elevated radiation dose during fluoroscopically guided intra-articular hip injections. The increased radiation experienced by patients with a larger BMI, however, is likely negligible.