Analysis of Components of Upper Cervical Lordosis in Asymptomatic Lordotic and Kyphotic Subjects.

Upper cervical lordosis (CL) can be divided into 2 components: C2 slope (C2S) and McGregor slope (MGS) or C0–1 and C1–2 angles. The aim of this study was to investigate the components of upper CL in asymptomatic kyphotic and lordotic subjects. CL, C0–2 Cobb angle, MGS, C2S, C1 Slope, C0–1 Cobb angle, C1–2 Cobb angle, T1 slope angular parameters, and the C2–7 sagittal vertical axis distance of 78 asymptomatic subjects were measured. Sixty subjects had lordotic curvature and 18 had kyphotic curvature. There was a significant difference between the kyphotic and lordotic groups in all parameters, except for C0–1 Cobb angle and C2–7 sagittal vertical axis. In lordotic subjects, MGS and C2S accounted for 58% and 42% of the C0–2 angle, whereas in kyphotic subjects, 86% of C0–2 was accounted for by C2S. There was a strong negative correlation between C2S and MGS. In asymptomatic subjects, as CL decreases, MGS decreases, C2S increases, and the C0–2 angle turns down on the horizontal plane to maintain the horizontal gaze. Turning down the C0–2 angle is more important than its value for maintaining horizontal gaze; thus, the slopes (MGS and C2S) can better represent the upper and lower cervical alignment than angle values can. The relationship between upper and lower cervical alignment should be evaluated in terms of slope angles rather than simple angles. The lack of significant difference between the C0–1 angles in the kyphotic and lordotic groups suggests that only the C1–2 angle is involved in the compensatory mechanism for the horizontal gaze. [ABSTRACT FROM AUTHOR]