**4.1 Two-dimensional analysis of posture and back shape**

### *4.1.1 Tactile methods of measurement*

### *4.1.1.1 Flexiruler*

The flexiruler for the evaluation of posture is common for clinical and research purposes [11, 12]. This objective method of postural measurement requires the manual placement of the flexiruler onto the contours or curvatures of the spine followed by the tracing and calculation of these angles onto paper (see **Figure 2A** and **B**).

Greenfield et al. [13] used a flexiruler to measure the mid-thoracic curvature, while Rheault et al. [14] observed the inter-rater reliability of the flexiruler for measuring cervical lordosis in two different positions (neutral and fully flexed) in 20

### **Figure 2.**

*An example of the flexiruler method (A) data collection and (B) measurement of lumbar lordosis based on the captured data [15].*

healthy subjects [13, 14]. In both studies, the flexiruler was placed on the curvature of the spine, with its tip at the most proximal part of the curvature and the other end at the distal end of the spine.

Following the measurement of the spine, the flexiruler was placed on a paper, to trace its curve. Greenfield et al. [13] reported good to moderate Pearson correlation for intrarater (r = 0.90) and interrater reliability (r = 0.70). Furthermore Rheault et al. [14] reported no significant difference between raters (t = 1.24; p>0.05) at the two different positions of the cervical spine. The results of both Greenfield et al. and Rehault et al. studies suggest that the flexible ruler is a reliable measuring tool between raters for measuring sagittal plane curvature.

Concerning validity, many researchers have demonstrated a high correlation between radiographic and surface measurements for measuring the lumbar spine curvature [16, 17]. For example, Hart and Rose [18] compared the angles of the curve taken with a flexible ruler to the angle obtained by the standard roentgenographic technique and found good validity with the Pearson product moment correlation of +0.87. Burton further substantiated the result by reporting a correlation of +0.87 for the validity of the flexible ruler in comparison to the radiographic method for measuring lumbar lordosis [16]. Even though the above studies demonstrated good validity, the main limitation was that the results were based on a very low sample size (n = 8). In addition, the measurement of postural variables through a flexiruler is always two-dimensional. The presentation of spinal curvature is not necessary always two-dimensional. There is a possibility of the deviation of curvature being in more than one plane. In this scenario, the obtained spinal curvature angle might not represent the real degree.

It is important to note that most of the above studies reported their results based on the data collected from young normal healthy participants. Although the use of the flexible ruler is important for this population, there is a possibility that the flexible ruler may be more difficult to use for patients with pain, disease, or postural deformity. Other limitations of this method of postural assessment are the following. Firstly, it is difficult for patients to maintain one position during data collection. Secondly, the literature reports only one measurement plane (sagittal). It is difficult to measure both the frontal and the transverse plane posture variables. Third, this method of postural assessment has a high possibility of manual error during data collection and angle measurement [19].

### *4.1.1.2 Goniometry*

In clinical practice, goniometers are commonly used to measure joint range of motion (ROM) [20]. Icn et al. reported the use of a goniometer for the assessment of a number of posture variables [21]. This method of direct body measurement used a goniometer to quantify posture variables with a value from zero to 360 degrees. The results of their study demonstrated moderate correlation (r = 0.47) to measure the tibiotarsal angle, knee flexion/extension angle, quadriceps angle as well as the sub-talar angle in relation to photogrammetry.

Conversely, Harrison et al. reported poor interrater reliability when using manual goniometry for the measurement of sagittal postural angles in the neck inclination angle (craniovertebral angle) and cranial rotation (sagittal head tilt) (see **Figure 3**) [22]. The ICC measures were found to be r = 0.68 and r = 0.34 for the cervical rotation angle and neck inclination angle, respectively. The authors attributed the poor results to the difficulty in maintaining the arm of the goniometer parallel with the horizontal axis.

Fortin et al. ([9], pp. 381-382) suggest that the main limitation for this type of individual measurement of postural variables is the lengthy evaluation process

*Posture and Back Shape Measurement Tools: A Narrative Literature Review DOI: http://dx.doi.org/10.5772/intechopen.91803*

**Figure 3.** *Measurement of shoulder and neck inclination angle using goniometer (reproduced from Harrison et al. [22]).*

involved for both the therapist and the patient. The author states that 'this approach may be appropriate for the assessment of one body segment or a variable, but not for the whole body or posture'.
