1. 2017;20;E721-E726The Relationship Between Body Mass Index and Fluoroscopy Time During Intraarticular Hip Injection: A Multicenter Cohort Study
   Retrospective Evaluation
   Zachary L. McCormick, MD, Meghan Bhave, MD, David T. Lee, MD, Paul Scholten, MD, Samuel K. Chu, MD, Ashwin N. Babu, MD, Mary Caldwell, DO, Craig Ziegler, MD, Humaira Ashraf, MD, Ryan Clark, DO, Claire Gross, MD, Jeffrey Cara, DO, Kristen McCormick, MD, Brendon Ross, DO, Joel Press, MD, David R. Walega, MD, and Daniel Cushman, MD.

BACKGROUND: Higher body mass index (BMI) is associated with difficulty in obtaining imaging studies. While there is a small body of literature regarding the relationship between fluoroscopy time and BMI during injections for pain management, this has not been studied for intraarticular (IA) hip injections. Further, in academic training centers, trainee involvement may affect this relationship.

OBJECTIVE: To determine the relationship between BMI and fluoroscopy time during IA hip injections, both with and without involvement of a trainee.

STUDY DESIGN: Multicenter retrospective cohort study.

SETTING: Three academic, outpatient musculoskeletal and pain medicine centers.

METHODS: Patients who underwent fluoroscopically guided IA hip injections with encounter data regarding fluoroscopy time during the procedure and BMI were included. Mean and standard deviation fluoroscopy time were recorded. Comparisons were made between BMI categories of normal (18.5 – 24.9 kg/m2), overweight (25.0 – 29.9 kg/m2), and obese (greater than or equal to 30.0 kg/m2). Statistical significance was set at P = 0.01 due to multiple comparisons.

RESULTS: A total of 559 IA hip injections are represented in this cohort. Patients had a mean age of 58 (standard deviation [SD] 14) years and 63% were women. There was no significant difference in fluoroscopy time when comparing BMI categories (P = 0.02). However, when trainees were not involved in the injection, fluoroscopy times were significantly shorter with decreasing BMI category, with normal weight patients requiring the shortest fluoroscopy times (P = 0.01).

LIMITATIONS: This study evaluated total fluoroscopy time, not radiation dose exposure per injection, which provides more direct and precise information with regard to provider and patient radiation exposure and overall safety. Future study of the impact of BMI on radiation dose during fluoroscopically guided IA hip injections is needed.

CONCLUSIONS: Fluoroscopy times during IA hip injections increase with higher BMI categories in a statistically significant manner when performed by experienced clinicians but this relationship is not observed when injections are performed with a trainee in a teaching institution. This finding appears to be related to longer fluoroscopy time required to complete an IA hip injection in patients with lower BMI when a trainee is involved.

KEY WORDS: Hip, injections, obesity, overweight, body mass index, fluoroscopy, radiation, pain