Faculty Bibliography

BACKGROUND CONTEXT: The literature has demonstrated that sagittal pelvic and thoracolumbar alignment parameters vary with age. However, existing studies on age-based variations in cervical alignment have been primarily limited to studies in Asian populations. PURPOSE: To investigate age-based variations in sagittal cervical radiographic parameters in an asymptomatic North American population. STUDY DESIGN/SETTING: Prospective single-center database. PATIENT SAMPLE: Asymptomatic subjects>18 years who underwent fullbody stereoradiographs and completed health-related quality of life (HRQOL) measures. OUTCOME MEASURES: Oswestry Disability Index (ODI), Neck Disability Index (NDI), sagittal radiographic parameters. METHODS: Subjects were divided into 5 age groups (<35y, 35-44y, 45- 54y, 55-64y, >=65y) based on standards from previous literature. Demographics and radiographic parameters were compared between age groups using ANOVA. Cervical parameters included C0-C2, C2-C7, and C0-C7 angles; contribution of the upper cervical angle to the total cervical angle (UpperC%: C0-2 divided by C0-7); C2-7 sagittal vertical axis (cSVA); cervical lordosis apex (CL); and T1 slope (T1S). Horizontal gaze parameters included the chin-brow vertical angle (CBVA), Slope of Line of Sight (SLS), and McGregor's slope (McGS). RESULTS: A total of 118 subjects were included. Age group sizes were:<35y: 30 (25%); 35-44y: 18 (15%); 45-54y: 17 (14%); 55-64y: 21 (18%); >65y: 32 (27%). ODI and NDI were similar across age groups (p=.582-0.749). Age groups had similar values for T1S-CL (mean 21.1, range 2-47; p=.170), cSVA (mean 27 mm, range -22-63 mm; p=.381), C0-C2 angle (mean 20.7, range -5-44; p=.527), and apex of CL (mean C5) (p>.05). C2-C7 angle increased significantly with age, <35y: -2.2; 35-44y: 1.6; 45-54y: 3.6; 55- 64y: 10.7; >65y: 11.8 (p<.001). C0-C7 increased with age (p<.01). There was a trend for UpperC% to decrease with age: <35y: 94%; 35-44y: 98%; 45-54y: 97%; 55-64y: 70%; >65y: 73% (p>.05). CBVA, SLS, McGS, and T1S did not change with increased age. CONCLUSIONS: This study is one of the few to describe age-based variations in cervical alignment in a North American population. C2-7 and C0-7 angles increased with increased age, despite similarities in cervical sagittal vertical axis. Age-based changes in lower cervical alignment did not result in worse HRQOL and thus may be a component of physiologic aging. These results should be considered in surgical planning, especially when considering any instrumentation of the cervical spine