What are the strategies for maintaining horizontal gaze in asymptomatic subjects?

Abstract

Introduction Maintaining horizontal gaze is essential for activities of daily living. In subjects with postural malalignment, compensatory mechanisms are recruited to maintain horizontal gaze, especially at the cervical level [1] . While the cervical curvature had been typically considered to be lordotic, recent studies have shown that different forms of curvatures can occur even in asymptomatic subjects [2] . It is still not known how asymptomatic subjects achieve horizontal gaze. The aim was to investigate the different cervical strategies for maintaining horizontal gaze. Materiel et methodes Overall, 144 asymptomatic subjects (age: 29 ± 11 years, 71F) filled the SF36 quality of life (QoL) questionnaire and underwent full body biplanar X-rays in free standing position. Typical global postural and spino-pelvic alignment parameters were assessed. Head and cervical parameters were measured: radiographic chin brow vertical angle (CBVA), C0C2, C1C2, C2C7, C2 slope, C2C7 SVA, T1 slope, neck tilt, thoracic inlet angle (TIA). Subjects were divided into 3 groups of cervical curvature forms per C2C7 angle: kyphotic (K: 5°). Demographics, SF36 parameters and CBVA were compared between groups (Kruskal–Wallis test). Global postural, spino-pelvic, head and cervical parameters were compared between groups, while controlling for confounding factors (ANCOVA). Resultats Forty-six (32%) subjects had kyphotic (−12 ± 7°), 39 (27%) straight (0 ± 3°) and 59 (41%) lordotic (12 ± 7°) cervical spines. While demographic and SF36 parameters did not differ between groups, CBVA was found to be significantly different between lordotic and kyphotic groups (2° vs. 6.5° resp., P = 0.002), Subjects in the 3 groups had similar PI, PT, SS, LL and knee flexion ( P > 0.05). However, SVA (L: −2, S: −11, K: −26 mm, P P P Discussion Kyphotic cervical spine subjects presented more posterior global alignment, with smaller TK and decreased T1 slope. These subjects compensated at the lower cervical level with a kyphotic C2C7 and a hyperlordotic upper cervical spine (increased C0C2 and C1C2) in order to maintain horizontal gaze. In contrast, lordotic cervical spine subjects had more anterior global alignment, with larger TK and increased T1 slope. These subjects compensated at the lower cervical level with a lordotic C2C7 and a hypolordotic upper cervical spine (decreased C0C2 and C1C2). Straight cervical spine subjects had an intermediate profile. Asymptomatic subjects can employ different cervical strategies in order to compensate for differences in global alignment in order to maintain horizontal gaze, without alteration of QoL.