**5. Discussion**

**4.3. Horizontal plane values (rotation)**

**Height difference and SD in mm**

**Mean spinal distances between spinal anatomical landmarks in** 

12 Innovations in Spinal Deformities and Postural Disorders

Distance between the apical cervical vertebra and the vertebra

Distance between the vertebra prominens and the thoracic apical

Distance between the thoracic apical vertebra and the 12th Thoracic

Distance between the 12th Thoracic vertebra and the lumber apical

**4.4. Sagittal plane values for female and male subjects**

were found (see **Table 5**).

**Differences in depth levels between the two sides of the back in males and females Left side minus right** 

female and male subjects.

**the frontal plane**

prominens

vertebra

vertebra

vertebra

**side**

SLy‐SRy

Shoulder level (acromium) ALy‐ARy

horizontal plan.

Inf. angle of scapula

The left inferior angle of the scapula in females was rotated forward in comparison to the right shoulder. No other statistically significant differences at the acromium, iliac crests or PSIS

**Table 5.** Female and male normative values and mean differences between the left and right side of the back in the

Iliac crests ICLy‐ICRy 2.08 ± 13.81 −1.52 to 5.69 NS −0.298 ± 34.2 −14.41 to 8.45 NS PSIS PSLy‐PSRy 2.45 ± 13.84 −1.15 to 6.06 NS 3.29 ± 12.54 −0.89 to 7.47 NS

**Females Males**

Distance between the lumbar apical vertebra and the sacral point 89.5 ± 25.8 96.3 ± 27.5

**Table 4.** Normative values for the mean spinal distances between spinal anatomical landmarks in the frontal plane for

Distance between C2 and the apical cervical vertebra CA 27.9 ± 8.1 44.2 ± 73.5

**P value Height difference and SD in mm**

**Mean values and SD in mm**

**For female subjects For male subjects**

49.5 ± 29.7 66.6 ± 41.8

371.0 ± 51.2 388.6 ± 67.6

227.9 ± 32.6 241.1 ± 40.6

90.5 ± 29.6 88.9 ± 40.7

5.85 ± 40.05 −4.58 to 16.29 NS 11.55 ± 34.9 −0.10 to 23.19 P = 0.05

5.82 ± 23.24 −0.23 to 11.88 P = 0.05 6.22 ± 18.64 0.01 to 12.44 P = 0.05

**95% CI of the difference in mm**

**P value**

**95% CI mm of the difference in mm**

The mean thoracic kyphosis angle was 29.37 *+* 3.94° and the mean lumbar lordosis angle was ‐37.7.

The purpose of this study was to produce normative data for asymptomatic standing back shape and posture in young adults, against which significant postural deformity could be defined. Although numerous commercial optical and computer systems are available [17–20] data on normal adolescent and adult back shape have so far been scarce [12, 13]. This will affect the clinical certainty with which we can establish an observed spinal curve as abnormal and therefore be able to initiate appropriate treatment.

Overall young adults in the current study were very symmetrical. The mean distances between the left and right sides of the back and the average values were calculated. Overall only the distance between the scapula and the acromion process was significantly smaller on the right side than the left side of the back. It is possible that this is related to the fact that most subjects were right handed and asymmetry can be related to the upper limb dominance influ‐ ence. In a typical posture pattern the right shoulder is lower than left in right‐handed people [1, 21]. Additionally, as the body is not perfectly symmetrical, some deviations may have no clinical implications [5].

"Normal" standing posture is generally described as one with a straight back and no trunk asymmetries [22]. Comparison between studies using quantitative results is difficult because of the wide diversity of tools used within other studies. A further challenge is that different quantitative variables have been measured in different studies through different approaches; for example, the different back shape instruments that have been used in previous studies, such as non‐tactile optoelectronic systems like the formetric and ISIS2 systems where a light beam is shone onto the back [23–25]. The microscribe digitizer used in this study is a tool for acquiring a static 3‐D computer recording of a physical object based on optical sensors in each joint of the instrument and is capable of measuring all three X, Y, Z coordinates. The methods for measuring angles or distance used by these different systems has meant that comparison of "normal" values between different systems is very difficult as the individual parameters are calculated in different ways.

With regards to the methodological aspects of this study, the sample size of 100 individuals comprised a homogenous population of young adults. The results have provided a template or framework of the range and limits of normative values for specific back variables of young adults in a standing posture. We acknowledge that a hundred subjects is not usually consid‐ ered to be a large sample size and agree that a larger sample size of a few hundred subjects would have increased the external validity of this study (the degree to which the results can be transferred to the general population of young adults).

The other statistically significant difference was the distance between the inferior angle of the scapula and the apical thoracic vertebrae. For this parameter the right side distance was signifi‐ cantly greater than the left sided value. No other significant differences in the distances between key anatomical landmarks between the left and right sides of the back were found in females. For male subjects however no statistically significant differences were found between the left and right sides of the back for all the key anatomical landmark distances. To the best of our knowledge no similar studies using the Microscribe have been conducted that have measured similar variables so it was not possible to compare the results of this study with previous studies.

In the frontal plane the key difference in height levels between specific key anatomical landmarks on the two sides of the back was at the level of the shoulders; the left shoulder acromion was found to be significantly higher than the right. Further, no statistically sig‐ nificant differences were found at the levels of the inferior scapular angle, the iliac crests and the PSIS. In males there were no statistically significant differences between the two sides of the back. However, at the PSIS level, the left PSIS showed a trend toward being higher than the right PSIS.

With regards to the measurement of the frontal plane spinal angles, the mean frontal plane angles values showed that overall healthy young females have relatively straight spines. As stated previously, in this current study the mean thoracic curvature value was *+*2.38° and the mean lumbar curve was *+*1.65°. This supports the textbook "Ideal" of adults having a rela‐ tively straight spine [1]. These results however differ to the results we obtained previously using the surface topography equipment ISIS to measure a similar cohort of young adult stu‐ dents [6]. In this study, the mean thoracic curvature value found was 16.1° *+* 6.9° and the mean lumbar curvature value was 13.4° *+* 6.9°. It is the authors belief that the differences in values obtained from the ISIS2 scanner and the microscribe digitizer are due to the fact that the ISIS2 scanner has previously been shown to overestimate the magnitude of small curves [26].

In our study and in this population of young asymptomatic adults we found a mean thoracic kyphosis of 29.37° and lumbar lordosis of −37.7° in the sagittal plane. These values support the values provided by the Scoliosis Research Society who suggest that the normal range of tho‐ racic kyphosis is between 20 and 40° on X‐ray measurement [18, 26]. Our results also support the study by Betz [27] who found that the normal range for lumbar lordosis on X‐ray ranged between −20 and −60°. Propst‐Proctor and Bleck and Stagnara et al. evaluated the sagittal pro‐ file of a group of normal subjects aged 20–29 years old [28, 29]. The mean values of thoracic kyphosis ranged from 30 to 50° and the mean values of lumbar lordosis was calculated to be 55° which was greater than the lumbar lordosis in our group of subjects.

Bernhardt and Bridwell [30] conducted a segmental analysis of sagittal plane alignment of the normal thoracic and lumbar spines as well the thoracolumbar junction on X‐rays. Within this study a wide range of healthy subjects (n = 102) aged between 5 and 29 years old were included. The authors reported a mean value of thoracic kyphosis at 40°, and mean of lumbar lordosis at −44°. While the thoracic Kyphosis in our study support the results obtained in the Bernhardt study, the lumbar lordosis reported in the Bernhardt study is much higher than the mean lumbar lordosis in our study. This may possibly be attributed to the fact that Bernhardt study included a wide range of ages comprised of children, adolescents and adults.
