Association of Pre-Operative Computed Tomography Hounsfield Units with Pseudarthrosis Requiring Revision After Multi-Level Anterior Cervical Discectomy and Fusion

Wednesday, February 21, 2024

Presenting Author(s)

Tej D. Azad, MD, MS

Resident
Department of Neurosurgery, The Johns Hopkins University School of Medicine
Baltimore, MD, US

Co-Author(s)

KA

Karim Ahmed, MD

Resident
Johns Hopkins University
Baltimore, Maryland, United States
Safwan Alomari, n/a

Resident
Johns Hopkins
Baltimore, Maryland, United States
AB

Ali Bydon, MD

Professor
Johns Hopkins University
Baltimore, Maryland, United States
Daniel Davidar, MD

Research Fellow
Johns Hopkins University School of Medicine
Baltimore, Maryland, United States
Andrew M. Hersh, B.S.

Medical Student
John Hopkins Medical School
Baltimore, MD, US
Kelly Jiang, n/a

Medical Student
Johns Hopkins University School of Medicine
Baltimore, MD, US
Daniel Lubelski, MD

Assistant Professor of Neurosurgery
Johns Hopkins University School of Medicine
Baltimore, MD, US
AT

Anthony Tang, B.S.

Medical Student
University of Pittsburgh School of Medicine
Pittsburgh, Pennsylvania, United States
Nicholas Theodore, MD, MS (he/him/his)

Director, Neurosurgical Spine Center; Professor of Neurosurgery
Johns Hopkins University School of Medicine
Baltimore, MD, US
Carly Weber-Levine, MS (she/her/hers)

Medical Student
Johns Hopkins University School of Medicine
East Setauket, NY, US
TW

Timothy Witham, MD

Professor
Johns Hopkins University
Towson, Maryland, United States

Disclosure(s):

Andrew M. Hersh, AB: No financial relationships to disclose

Carly Weber-Levine, MS: No financial relationships to disclose

Introduction: Multi-level anterior cervical discectomy and fusion (ACDF) is associated with an increased risk of pseudarthrosis. Bone mineral density (BMD) is a risk factor for the failure of fusion following spinal surgery. While the gold standard for evaluating BMD is the dual-energy x-ray absorptiometry (DEXA) scan, it is not part of the routine pre-operative workflow. Alternatively, Hounsfield units (HU) can determine BMD and can be derived from routine pre-operative computed tomography (CT) scans. In this study, we examine the association of HU values with the development of pseudarthrosis requiring revision surgery in patients undergoing multi-level ACDF.

Methods: Between January 2016 and March 2022, patients undergoing multi-level ACDF at a single tertiary center were identified. Clinical data were collected from medical charts. HUs were measured from CT scans at the C2 and C3 vertebral levels using picture archiving and communication systems (PACs). Pearson χ2 and student t-tests were used to evaluate for differences in categorical and continuous variables, respectively. A multivariate logistic regression was performed.

Results: One hundred patients underwent multi-level ACDF during this timeframe, with thirty-one patients having suitable pre-operative CT scans. Patients had a median age of 61 and C4-C7 were the most common operative levels. Five patients subsequently underwent revision surgery for pseudarthrosis with a median time from initial surgery to pseudarthrosis of 4.57 months. Patients with pseudarthrosis had significantly lower HU values at C2, C3, and averaged across C2 and C3 compared to patients who did not develop this complication (p=0.004, p< 0.0001, and p< 0.001, respectively). The multivariate logistic regression showed that average HU value at C2 and age were the closest predictors for pseudarthrosis, though neither was statistically significant.

Conclusion : Deriving HU value from CT scans provides an assessment of BMD without the need for additional imaging and may potentially inform a patient’s risk of developing pseudarthrosis following multi-level ACDF.