MRI-Based Tool Assesses Bone Quality Prior to Spine Surgery

Try this if you don’t have access to a DEXA scan

Poor bone density is linked to poor outcomes of spine surgery, but DEXA scans are not routinely performed preoperatively. Part of the reason may be that the equipment is expensive, specialized and sometimes unavailable. As a surgeon, you want to maximize positive outcomes from all angles and give your patients every chance to succeed, so how can you screen for osteoporosis and osteopenia when there’s no DEXA scanner available?

VBQBone quality is a predictor of spine surgery outcomes

Virtually all patients undergoing spine surgery have magnetic resonance imaging (MRI) scans available. Researchers from The Johns Hopkins Hospital have used MRIs to develop a simple tool that accurately measures bone quality with no additional cost to the patient or health system, as reported in the April 1 issue of The Spine Journal.  

“Providers need to try this technique, which involves using the standard tools on an MRI viewer software,” senior author Daniel M. Sciubba, MD, told SpineUniverse. “Once learned, it literally takes seconds to check bone quality by looking at an MRI scan. It is a true game changer for the field.

“Given that inadequate assessment of bone quality prior to spinal fusion can lead to disastrous results, it is imperative that spine surgeons innovate in this area,” emphasized Dr. Sciubba, who is Director, Spine Tumor and Spine Deformity Surgery, and Professor of Neurosurgery at The Johns Hopkins Hospital in Baltimore, MD.

The VBQ Tool

The researchers developed the MRI-based tool, called the Correlation of the Vertebral Bone Quality (VBQ), which is based on the higher T1 signal intensity (SI) linked to fatty spinal bone marrow infiltration in patients with osteoporosis. The VBQ score is calculated using the following steps:

  • Place regions of interest (ROI) within the medullary portions of the L1-L4 vertebral bodies and within the cerebrospinal fluid (CSF) space at the level of L3 using midsagittal cuts. (If the ROI is not visible, a parasagittal cut may be used.)
  • Assess average SIs within each ROI and the average SI of the CSF
  • Calculate the VBQ as the quotient of the median SI of the vertebrae divided by the SI of the CSF

The researchers created a short video to show spine surgeons how to use the VBQ score. The normal range on the VBQ is between 2 (healthy bone quality) and 4 (very poor bone quality).

VBQ exampleNon-contrast-enhanced T1-weighted MRI of the lumbar spine detailing the regions-of-interest (circles) used to calculate the VBQ score; AV = average signal intensity of the region-of-interest (VBQ score in shown example = 3.73). Image courtesy of Jeff Ehresman.

“Our previous papers have elucidated that adverse bone-related events most commonly occurred in patients with VBQ scores greater than 3,” explained lead author Jeffrey Ehresman, MD Candidate, Johns Hopkins University School of Medicine. “Therefore, a VBQ score of 3 is our tentative cutoff and further work will refine this threshold.”

VBQ Accurately Predicts Bone Density

When VBQ score was compared to DEXA scan findings in 68 patients who underwent spine surgery for degenerative conditions (37 of whom had osteopenia/osteoporosis), VBQ score was significantly associated with the presence of osteopenia/osteoporosis with a predictive accuracy of 81%.

VBQ scores were “moderately” correlated with femoral neck T-scores and the lowest overall T-scores (r=0.51) of each patient, and “fairly” correlated with total hip T-scores. The VBQ score was generalizable across multiple MRI systems, according to the researchers.

“Providers and patients can obtain immediate assessment of bone quality when undergoing any preoperative spinal MRI scan,” Dr. Sciubba explained. “Given that the technique is independent of location or type of MRI scanner used, such information is obtained easily and without additional cost. Furthermore, our results suggest that this technique is as predictive if not more predictive for potential osteoporotic mishaps related to spine surgery than the current gold standard of expensive and time-consuming DEXA scans.”

Patients in this study underwent spine surgery between January 2013 and January 2018, and underwent both DEXA imaging and noncontrast T1-weighted MRI of the lumbar spine within 2 years prior to surgery. Only DEXA T-scores of the femoral neck and total hip were included in this analysis. Lumbar spine T-scores were not included as degenerative osteophytic growths that may occur with aging may artificially inflate bone density measurements, according to previous research.1 Patients with previous instrumentation on ≥2 lumbar vertebrae were not included in the study as instrumentation can affect average SI.

Bone Quality May Alter Spine Surgery Plans

“Given the aging of our population, spine surgeons are offering instrumented fusions to an increasing number of patients who are older and frail,” Dr. Sciubba said. “Unfortunately, poor bone density is now extremely common, affecting younger women and men to a much greater degree than many providers appreciate.”

Poor bone quality places patients at risk for fragility fractures and mechanical complications in spine surgery, including proximal junctional kyphosis and hardware failure, the researchers explained. Thus, awareness of poor bone quality may alter operative plans. For example, surgeons may choose to include cement augmentation in the operative construct or to delay surgery to allow for medication intervention to improve bone quality with use of pro-osteogenic medications.

“Such interventions, even if they delay surgery, would be welcome to patients and providers given the potential to prevent disastrous instrumentation failures and spinal fractures,” Dr. Sciubba said.

Unfortunately, DEXA scans are not routinely conducted before surgery, research shows, in part because scheduling these scans can delay the patient’s surgical treatment and they are costly.2

“Since MRI scans are performed preoperatively on virtually all patients undergoing spine surgery, our solution involves using an MRI-based bone density tool to provide essential bone quality information at no added cost to the patient or health system,” Dr. Sciubba said. MRI also does not pose a risk of radiation exposure.

DEXA vs VSQ: Which to Use When?

“If a DEXA scan has already been obtained prior to my involvement as a spine surgeon, I will definitely use the information provided,” Dr. Sciubba said. “However, I now routinely use the VBQ score as the most predictive instrument. I am willing to forego ordering a DEXA scan, as this saves time, energy and money. Obviously, in those rare cases in which an MRI is not obtained prior to a spine surgery, I will still rely on the DEXA scan.”

 

Updated on: 07/14/20
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