Cone Beam Computed Tomography Assessment of Cervical Spine Bone Density

Introduction: Age-related loss of bone density is a characteristic of osteoporosis, leading to reduced bone strength and increased risk of fracture. In spine surgery patients, osteoporosis also leads to poor outcomes, including pedicle screw loosening, proximal junctional failure, cage subsidence, and adjacent segment disease. Osteoporosis screening is generally performed using dual energy X-ray absorptiometry (DXA) to assess bone density. Cone beam computed tomography (CBCT) is widely used in orthopedic surgeries, including spine surgeries, and in dental and maxillofacial surgery to visualize teeth and jaws for pathology, surgical planning for jaw and TMJ joint reconstruction, structural maxillofacial deformity, pre-operative implant site assessment, 3D cephalometry, and appropriate treatment planning. CBCT is also used for evaluation of cervical vertebrae in skeletal maturation - growth assessment, diagnosis of obstructive sleep apnea, and temporomandibular disorders. In comparison to traditional computed tomography (CT), CBCT introduces several advantages including high spatial resolution (favorable for bone architecture evaluation); high image accuracy; low cost, faster scan time, ease of use, compact machinery, and low radiation exposure. Few studies have investigated the potential use of CBCT images for opportunistic assessment of bone health as an alternative to traditional CT and DXA. This study investigates whether bone density in the C3 vertebrae as determined by CBCT image analysis aligns with previously known trends of age-related bone loss in women post-menopause. Specifically, this study examines changes in bone density of the C3 vertebrae in females, beginning from puberty to post-menopause to late adulthood. Since the use of CBCT beyond dentistry is not well-established, the overarching goal of this study is to provide support for the reliability of dental CBCT images in the determination of bone health for orthopedic applications.

Objectives: This study aims to provide support for the reliability of cone beam CT in allowing for measurements of bone density. The use of CBCT for opportunistic screening of osteoporosis and potentially orthopedic surgeries is highly relevant for medical and dental professionals. The various advantages of CBCT, including high accuracy, low costs, and greater convenience strengthens its position as a potential alternative to traditional CT. Also, as a result of longer life expectancies, more osteoporotic patients are visiting dental clinics, and existing CBCT scans could be utilized to assess osteoporosis risk.

Methods: Cone beam scans of 416 female patients with ages ranging from 10 to 93 years were obtained between 2010 ─ 2019. CBCT scans included visualization of the patient's skull, jaw, facial bones, and upper portion of the cervical spine. Sagittal views of the scans were analyzed, with a specific focus on the C3 vertebrae. ImageJ analysis was used to quantify the intensity of the C3 vertebrae region of interest, as a measure of bone density after calibration. Intensity of the muscle area adjacent to the C3 vertebrae and intensity of air in the lungs were measured for the internal calibration of CT Hounsfield units (HU). A linear and spline lines of fit showing changes in bone density values as a function of age were generated to display the overall decline in bone density in females. The linear lines of fit, confidence intervals, linear equations, and R values were calculated using JMP statistical software based on measurements retrieved from the 416 patient scans.

Results: A decline in bone density with age was observed (-2.83 HU/year, p< 0.0001). A rapid decline was observed after 50 years of age (-3.72 HU/year, p=0.0001). These findings are consistent with previously established trends depicting changes in BMD as a function of age in females, such that peak loss of bone density occurs during the first few years post-menopause, beginning around ages 50 to 54.

Conclusions: The finding that female subjects aged 50-93 years exhibited a significant decrease in bone density is in line with scientific literature exploring the increased prevalence of osteoporosis in postmenopausal women. The ability to identify these established trends using CBCT scans provides evidence for the utility of obtaining bone density measurements through CBCT image analysis. Our findings may be useful in providing evidence in support of CBCT scans as an alternative method of osteoporosis screening and assessment of bone quality in orthopedic and dental surgery patients. Notable limitations of the present study include the exclusion of body mass index (BMI) and race, among other demographic information. Further efforts to obtain this demographic information would be crucial in developing a more complete understanding of our sample data.