The Use of CT Hounseld Unit Values to Identify The Bone Quality in Patients With Cervical Degenerative Diseases. Lei He Peking University Third Hospital https://orcid.org/0000-0002-2930-3465 Fei Fei Zhou ( [email protected] ) Peking University Third Hospital Yu Sun Peking University Third Hospital Wei-Shi Li Peking University Third Hospital Research article Keywords: CT Hounseld unit value, dual-energy X-ray absorptiometry, T-score, cervical vertebrae, bone mineral density Posted Date: September 25th, 2020 DOI: https://doi.org/10.21203/rs.3.rs-75561/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 1/14 Abstract Background It is well known that osteoporosis may lead to the failure of spinal surgery. As the gold standard, dual-energy X-ray absorptiometry (DXA) is used to evaluate the overall bone mineral density (BMD). Previous studies have used CT (Computed tomography) value to evaluate local bone mineral density. The objective of this study was to investigate the application value of cervical CT value in preoperative bone quality evaluation of cervical degenerative diseases. Methods A total of 939 patients who received surgical treatment for cervical degenerative diseases in our center from January 2015 to December 2017 were retrospectively reviewed. The Hounseld unit (HU) values were measured in middle transverse CT images of the C2–C7 on the picture archiving and communication system (PACS), and the total bone mineral density T-score of L1–L4 was obtained by dual-energy X-ray absorptiometry. The changes in the HU values of C2–C7 were observed, the correlation between the HU value of C2–C7 and the total BMD T-score of L1–L4 was analyzed, and the HU thresholds of C2–C7 for different T-scores (-2.5 < T-score <-1 or T-score ≤2.5, respectively) were identied. Results The HU values of C2–C7 show a decreasing trend. The mean HU value of C2–C7 was 322.52 ± 89.27 HU. The average BMD T-score of L1-L4 was -0.73. The average HU value of C2–C7 was positively correlated with the average BMD T-score of L1–L4 (r = 0.487, P < 0.001). The HU threshold of C2–C7 was 269 HU when -2.5T-score-1, and it had a sensitivity of 75.7% and a specicity of 59.8% when used for screening for osteopenia; the HU threshold of C2–C7 was 269H U when T-score ≤-2.5, and it had a sensitivity of 63.8% and a specicity of 80.8% when used for screening for osteoporosis. Conclusions The HU values of cervical vertebrae gradually decrease from C2 to C7 in patients undergoing surgical treatment for cervical degenerative disorders. The CT HU value of cervical vertebrae is positively correlated with the BMD T-score provided by lumbar DXA, which is helpful for clinical evaluation of bone quality before surgery. 1. Background With an increasingly aging society, osteoporosis is becoming more prevalent. Dual-energy X-ray absorptiometry is the most widely used technique for diagnosing osteoporosis [1], and a T-score is used to determine whether the bone mineral density is normal. Many recent studies have explored the role of computed tomography Hounseld unit values in the diagnosis of osteoporosis, especially in the lumbar spine [2–6]. The attenuation coecients in a CT image are expressed in HU value, which quanties the amount of attenuation of any specied tissue or organ. In general, a larger tissue HU value represents a higher tissue density. An abundance of research has conrmed that the HU value of a lumbar vertebra is positively correlated with BMD and T-score in patients with non-degenerative lumbar spine disease. HU value can accurately reect the bone quality of lumbar vertebrae and can be used as a supplementary method to evaluate the density of the lumbar spine [7]. For degenerative lesions of the lumbar spine, Page 2/14 however, DXA may overestimate the BMD; instead, the HU value of the lumbar vertebrae may reect the actual bone quality [7, 8]. Unfortunately, few studies have investigated the role of HU values in the assessment of the cervical spine. In our current retrospective study, we explored the changes of the HU value of cervical vertebrae in patients undergoing surgery for cervical degenerative disease, the relationship between the HU value of the cervical spine and the T-score of the lumbar spine, and the application of HU value in assessing bone quality. 2. Methods 2.1 General data This study is retrospective. The hospital institutional review board approved this study. A total of 1,170 patients with cervical degenerative diseases underwent cervical spine surgery in the Department of Orthopedics and Cervical Spine, Peking University Third Hospital, from January 2015 to December 2017. Among these, 939 eligible patients (484 males and 455 females) with a mean age of 59 years, entered the nal analysis. All patients received surgical treatment, with 644 cases undergoing anterior cervical surgery and 295 cases undergoing posterior cervical surgery. 2.2 Inclusion and exclusion criteria The subject inclusion criteria were the following: a) preoperatively diagnosed cervical spondylotic myelopathy/radiculopathy, mixed cervical spondylosis, and/or ossication of posterior longitudinal ligament; b) failed standardized conservative treatment and clear surgical indications; and c) cervical three-dimensional-CT and DXA-based BMD examination at Peking University Third Hospital within 1 month before surgery. The subject exclusion criteria were the following: a) a history of cervical vertebrae and lumbar spine fractures or surgery; and b) cervical spine and lumbar spine bone destruction (e.g. tumors and infections). 2.3 Measurement method Based on the ndings of preoperative 3DCT of the cervical spine, the HU values of C2–C7 were measured by using the picture archiving and communication system (PACS) system (RA1000 version 3.0, General Electric Medical System (China) Co., Ltd.), and the mean of the HU values was calculated. The procedure for measurement of the HU value was as follows: on the middle-sagittal reconstruction view of C2–C7, the region of interest (ROI) was delineated as large as possible; however, this area did not include cortical bone and abnormal bone areas such as bone islands, venous sinuses, and compression fractures (Figure 1). The HU measurement for each vertebra was obtained by a PACS, and the HU value was independent from the change of CT window and level. Meanwhile, the total BMD T-score of the lumbar vertebrae was Page 3/14 measured by DXA before surgery. When T ≥ - 1.0, normal bone mass was diagnosed; when - 2.5 < T - 1.0, osteopenia was diagnosed; when T ≤ - 2.5, osteoporosis was diagnosed. 2.4 Statistical analysis Statistical analyses were performed by using SPSS 20.0 software package (IBM, USA). A two-sided test was applied, and a P value of <0.05 was considered statistically signicant. Spearman’s rank correlation was used to test the association between the cervical alignments and the HU value of the vertebral body. The General Linear Model (GLM) was used for assessing the difference between the mean T-score of L1– L4 and the mean HU value of C2–C7. Receiver operating characteristic (ROC) curves were drawn, and areas under the ROC curve (AUC) were calculated with -2.5 < T-score <-1 or T ≤-2.5 as the threshold of osteopenia or osteoporosis, respectively. When the sensitivity plus specicity was highest on the ROC curve as the critical points of the C2-C7 HU values, the sensitivity and specicity of screening for osteopenia or osteoporosis with the HU thresholds of C2–C7 were obtained. 3. Results 3.1 Measurement results The HU values of C2–C7 were 363.43 ± 92.52 HU, 340.44 ± 80.73 HU, 338.37 ± 86.92 HU, 333.43 ± 87.49 HU, 289.98 ± 76.60 HU, and 259.43 ± 62.59 HU, respectively. The mean HU value of C2–C7 was 322.52 ± 89.27 HU. The average total BMD T-score of L1–L4 in 939 patients, as shown by cervical DXA, was -0.73. 3.2 Correlation analysis The cervical alignment was negatively correlated with the HU value of the vertebral body (r = -0.396, P < 0.001). The average HU value of C2–C7 was positively correlated with the average BMD T-score of L1–L4 (r = 0.487, P < 0.001) (Figure 2). When the HU values of C2–C7 were used to screen for osteopenia (-2.5 < T < -1), the area under the ROC curve was 0.726 (95% condence interval [CI]: 0.694, 0.758) (Figure 3). The average HU value of C2–C7 was 327 HU when the sensitivity plus specicity was highest on the ROC curve, and it had a sensitivity of 75.7% and a specicity of 59.8% when used for screening for osteopenia; when it was applied for screening for osteoporosis (T ≤ -2.5), the area under the ROC curve was 0.767 (95% CI: 0.718, 0.816) (Figure 4). The average HU value of C2–C7 was 269 HU when the sensitivity plus specicity was highest on the ROC curve, and it had a sensitivity of 63.8% and a specicity of 80.8% when used for screening for osteoporosis. 4. Discussion Osteoporosis is a systemic skeletal disease characterized by low bone mass and deterioration of the micro-architecture of bone tissue and can lead to bone fragility and an increased risk of fracture. It is Page 4/14 common in postmenopausal women and elderly men. [1] Clinically, degenerative neck conditions are often complicated by osteoporosis. Osteoporosis can negatively affect cervical spine surgery and postoperative rehabilitation.