3.2.2. Explorative Data Analysis

The graphically apparent deviations of the vertebral bodies from the symmetrical zero position in the transverse and the coronal planes could be confirmed by statistical data analyses. The deviations were significant from T5 to L3 in the transverse plane and from C7 to T4, from T6 to T12 and for the pelvis in the coronal plane when that data of the entire group were considered and tested versus a hypothetical median of zero. Likewise, all the global parameters in the two respective planes deviated significantly from the respective symmetrical spine position (Table 5). The visual differences between the analyzed subgroups, however, could not be statistically confirmed for the transverse and coronal plane data. Here, only the isolated parameters revealed statistical trends pointing towards a possible existing difference (for "Pelvis Rotation" between the young and middle participants (*p* = 0.05) and for "Right Side Apical Deviation VP-DM + max (mm)" (*p* = 0.04) between the female and male participants).

In the sagittal plane, systematic deviations from a straight upright spine position existed in all the vertebral bodies except for T8 (neutral vertebrae of the thoracic kyphosis) and all the global spine parameters. In contrast with the two other planes, the statistical analyses also revealed systematic trends pointing towards possible differences between the analyzed subgroups. The global parameter of "Lumbar Lordosis (ITL-ILS) (◦ )" differed between the female and male participants (*p* < 0.001), while the parameter of "Thoracic Kyphosis (ICT-ITL) (◦ )" indicated a trend towards a difference between the participants in the different age cohorts (*p* < 0.001). The systematic trend behind these findings becomes apparent when observing the specific spine parameters. Sex-specific differences could be found for all the specific parameters except for the two major turning points (meaning the most flexed (T1) and the most extended (L1) vertebrae). Differences between the age cohorts in the global parameter of "Thoracic Kyphosis (ICT-ITL) (◦ )" were also apparent at the level of the specific spine parameters. The systematic differences due to the participants' belonging to different age cohorts can be seen here in the isolated upper thoracic vertebrae (C7–T4) and the pelvis (Table 5).

#### *3.3. Literature Comparison*

Table 6 compares the results for the global spine parameters of the current study with those derived from previous publications using the same VRS measurement device [18–23]. Most of the results were found to be almost comparable; however, there was a trend towards slightly lower values derived from the current study for the parameters of the transverse and the coronal plane when compared to those of previous research.


**Table 6.** Comparison of the results for the global spine parameters from the current study with those of previous research.

*Bioengineering*

 **2022**, *9*, 809

age = 23.6 ± 2.0 years and *n* = 65 males, age = 24.3 ± 2.2 years; [20]: *n* = 89 females, age = 26.4 ± 4.5 years and *n* = 88 males, age = 27.7 ± 4.4 years; [21]: *n* = 52 females, age = 26.1 ± 6.9 years

and *n* = 51 males, age = 28.2 ± 7.4 years; [18]: *n* = 168 girls, age = 8.3 ± 1.3 years and *n* = 177 boys, age = 8.6 ± 1.2 years.

#### **4. Discussion**

Various studies have analyzed spinal posture and its possible adaptations to different spinal and other musculoskeletal pathologies using VRS [29–31]. However, reference values for the comparison of the possible pathological findings are only available for global spine parameters that mainly derived from children [18], younger adults [19–21], or young and middle-aged adults, but these are based on very small numbers of participants [22,23]. Systematically collected normative data, which differentiates between subgroups according to sex and age, which can be used to identify possible changes in spinal posture over the adult life span, were missing. One aim of this study was, therefore, to complement existing knowledge with a further reference dataset that meets those requirements. Spinal posture data were thus captured and analyzed based on 201 healthy participants according to sex and age over an adult life span of 18 to 70 years. A further aim was to expand the current knowledge by providing an additional reference dataset of specific spine parameters that contains three-dimensional posture data for every vertebral body (from C7 to L4 and the pelvis).
