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Pain and Spine Medicine

Reliability of MRI Epidural Depth Measurements in Cervical and Lumbar Epidural Steroid Injections

Friday, October 24, 2025
12:00 PM - 1:30 PM MT
Location: Original Research Theater

    Primary Author(s)

  • Insup Hong, Other

    Medical Student
    Loyola University Chicago Stritch School of Medicine
    Oak Park, Illinois

    • Co-Author(s)

  • Luis Soliz, MD

    Assistant Professor
    Loyola University Medical Center
    Elmhurst, Illinois

  • AH

    Adam Hintz, MD

    Physician
    Loyola University Medical Center
    Elmhurst, Illinois

  • PB

    Prempreet S. Bajaj, DO

    Associate Professor
    Loyola University Medical Center
    Oak Brook, Illinois

Disclosure(s):
Insup Hong, Other: No financial relationships to disclose
Luis Soliz, MD: No financial relationships to disclose
Background and/or Objectives: Current protocol for epidural steroid injections (ESIs) involves utilizing advanced imaging, ideally magnetic resonance imaging (MRI), for diagnosis and procedural planning. There are currently no studies evaluating the reliability of epidural depth measured using MRI compared to actual procedural depth.

Design: A retrospective study of prospectively collected data was performed at a single academic institution with 3 experienced pain management physicians. Skin to epidural depth (SED) was measured from MRI and compared to intraoperative loss of resistance (LOR).

Setting : Outpatient pain clinic

Participants : 50 patients were included: 13 cervical and 37 lumbar ESIs. 31 (62%) were female, 35 (70%) were white, average body mass index (BMI) was 30.12 (SD 5.94), median Charleson comorbidity index (CCI) was 3 (IQR (1-6)), and 10 (20%) of patients were tobacco users.

Interventions: MRI and procedural SEDs were measured to the millimeter for patients undergoing cervical or lumbar ESIs. MRI SED was measured using a T1-weighted sagittal MRI from the posterior aspect of the epidural space to the skin. Procedural SED was obtained by measuring intraoperative needle depth at LOR with a sterile ruler.

Main Outcome Measures: The correlation of MRI and procedural SEDs was assessed utilizing a paired t-test. The influence of patient-related factors on the reliability of MRI SEDs was evaluated by regression modeling.

Results: On average, MRI SED was 6.9 cm (SD 1.7 cm) and procedural SED was 7.0 cm (SD 1.6 cm). MRI SED was significantly lower than procedural SED by 0.2 cm (p = 0.04, 95% CI [-0.3, -0.1]). There was no significant influence of patient-related factors on the difference of MRI and procedural SED.

Conclusions: MRI SEDs statistically significantly underestimated procedural SED. However, the results were not considered clinically significant, reinforcing MRI SEDs as reliable predictors of procedural SEDs. We did not observe any patient-related factor to significantly influence the reliability of MRI SED in predicting actual SED.