The influence of body posture on cervical alignment measured in the sagittal plane on conventional radiographs: a systematic review.

BACKGROUND CONTEXT

Cervical sagittal balance parameters are an important aid in surgical decision-making and influence outcome in cervical spine surgery. In current literature, the normative values of these parameters vary highly within and between patients. This variability might be attributed to body posture.

PURPOSE

The primary aim is to review the literature on the influence of body posture, including studies that compare sitting or standing positions possibly varying in arm positions, on cervical alignment measured in the sagittal plane on X-rays.

STUDY DESIGN

A systematic review was performed.

METHODS

PubMed, Embase, Cochrane Library, Web of Science, and CINAHL were systematically searched for articles published up to and including May 2024. The primary outcome was variability in cervical alignment in the sagittal plane as measured in altering body postures on X-rays. Quality of the included articles was assessed with the QUADAS-2 tool.

RESULTS

Out of 17,628 screened articles, 8 were eligible for inclusion. Articles were excluded based on irrelevant outcomes (n=10,372), duplicates (n=4,315), wrong study design (n=1,462), or the influence of body posture was not described (n=612). Overall cervical alignment ranged from 33.3° lordosis to 3.5° kyphosis. In all studies, statistically significant differences in T1 Slope (T1S), C2C7 Sagittal Vertical Axis (SVA), McGregor Slope (McGS), or C7 SVA were observed with respect to body posture. The observed differences between postures for cervical alignment ranged from 1° to 16.6°.

CONCLUSIONS

Body posture significantly influences cervical alignment values measured in the sagittal plane on X-rays. Studies investigating this influence are scarce and vary highly in investigated body postures. Standardization of body posture is imperative to enable optimal comparison of cervical sagittal balance parameters within and between patients, but also between studies. Moreover, the high variability observed raises questions about the comparability of measured values in previously published studies.