• Koji Tamai, Joshua Romanu, Phillip Grisdela, Permsak Paholpak, Pengfei Zheng, Hiroaki Nakamura, Zorica Buser, and Jeffrey C Wang.
• Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, HMR 710, 2011 Zonal Ave, Los Angeles, CA 90033, USA; Department of Orthopedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3, Asahimachi, Abenoku, Osaka, 545-8585, Japan.
• Spine J. 2018 Sep 1; 18 (9): 1505-1512.

Background ContextCervical sagittal vertical axis (cSVA) of ≥40 mm is recognized as the key factor of poor health-related quality of life, poor surgical outcomes, and correction loss after surgery for cervical deformity. However, little is known about the radiological characteristics of patients with cSVA≥40 mm.PurposeThe purpose of this study was to identify the radiological characteristics of patients with cervical imbalance.DesignRetrospective analysis of weight-bearing cervical magnetic resonance (MR) images.Patient SampleConsecutive 1,500 MR images of symptomatic patients in weight-bearing position.Outcome MeasuresCervical sagittal vertical axis, cervical alignment, cervical balance parameters (T1 slope, Co-C2 angle, C2-C7 angle, C7-T1 angle, neck tilt, and thoracic inlet angle), disc degeneration (Pfirmann and Suzuki classification), end plate degeneration (Modic change), spondylolisthesis (antero- and retrolisthesis), anteroposterior (AP) diameter of dural sac, cross-sectional area (CSA), and fat infiltration ratio of the transversospinalis muscles at C4 and C7 levels.MethodsPatients were divided into two groups: cSVA≥40 mm and cSVA<40 mm. Gender, age, and cervical alignment were analyzed. Subsequently, matched imbalance (cSVA≥40 mm) and control (<40 mm) groups were created using the propensity score to adjust for age, gender, and cervical alignment. Cervicothoracic angular parameters, disc degeneration, Modic change, spondylolisthesis, and degeneration of the transversospinalis muscles at C4 and C7 were compared. Variables with p<.05 were included in the multinomial logistic regression model to identify factors that relate to the cervical balance grouping.ResultsThe incidence of patients with cervical imbalance was 2.5% (37 patients). Those patients had a higher incidence of kyphosis, were older, and there were more male patients. In the matched imbalance group, the T1 slope was greater (p=.028), C7-T1 lordotic angle was smaller (p<.001), the number of anterolisthesis was greater (p=.012), and the fat infiltration ratio at C4 and C7 was higher (p=.023, 0.030) compared with the control. Logistic regression analysis showed that the C7-T1 angle (adjusted odds ratio [aOR]=0.592, p=.001) and fat infiltration ratio at C7 level (aOR=1.178, p=.030) were significant independent variables.ConclusionsSmaller C7-T1 lordotic angle and severe muscle degeneration at C7 level were independent characteristics of patients with cervical imbalance.Copyright © 2018 Elsevier Inc. All rights reserved.

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