Low back pain is currently a common problem with a considerable medical and therapeutic impact [
One measurement method that illustrates important spine parameters is rasterstereography [
Khallaf examined 16 patients with lumbar disc herniation using rasterstereography [
All participants were recruited in 2011. The individuals in the patient group were enrolled in a rehabilitation hospital with a special section for chronic spinal diseases at Montanus-Klinik Bad Schwalbach, Germany. The healthy individuals in the control group were recruited from the general population and were examined at a second hospital, that is, University Hospital in Marburg, Germany. Both hospitals used the same measurement system.
The inclusion criteria for the patient group were underwritten patient information and informed consent, the ability to speak the German language, the ability to stand free without any assistance, the ability to lay flat on their back, evidence of lumbar disc herniation or protrusion detected by magnetic resonance imaging (MRI), and low back pain and/or leg pain; all stadia of pain (acute, subacute, chronic) were included.
The exclusion criteria for the patient group were age younger than 18 years, cancer, previous spinal surgery, relevant bone degeneration, red flags, pension request, relevant tattoos or scars on the surface of the back, and no pain on a numeric rating scale (NRS = 0).
The inclusion criteria for the healthy controls were the ability to speak the German language, no back or leg pain on a numeric rating scale (NRS = 0), the ability to stand free without any assistance, and the ability to lay flat on their back. The exclusion criteria were age younger than 18 years, cancer, previous spine surgery, relevant spinal degeneration, red flags, pension request, relevant tattoos or scars on the back, chronic low back pain, and lumbar low back pain and/or leg pain.
The study received ethical approval from the independent ethics committee of University Hospital Marburg (reference number Az. 22/11). Information about the procedure and risks were included in the patient information. Participants in the patient and control groups had to provide written informed consent.
All participants had to complete a general self-assessment questionnaire to provide individual data, for example, age, height, weight, comorbidities, pain anamneses, and a pain chart.
The Numeric Rating Scale for Pain (NRS) was used to measure pain intensity. The numeric scale has 11 items with “0” representing no pain and “10” representing the worst pain imaginable [
The level of functional ability was measured by the Hannover Functional Ability Questionnaire (FFbH-R). This instrument was developed for patients with musculoskeletal disorders, comprising 12 short self-administered questionnaires on functional capacity in the activities of daily living [
The PDI is a comprehensive self-administered questionnaire for assessing disability associated with pain. The respondents indicate the amount of perceived pain-related disability in seven different areas of daily living on an 11-point Likert scale with one end point of 0 (no disability) and the other end point set at 10 (maximum disability). The areas are home, social activities, recreational, occupational, sexual functioning, self-care, and life support activities. Higher scores indicate greater disability. The PDI has been shown to have a correlation of r = 0.7-0.9 with the Oswestry Disability Questionnaire in patients with low back pain [
The MPSS is classified in three chronification levels. Four axes were considered: temporal aspects of pain, pain distribution, drug intake, and utilisation of health care. The final score described three chronification levels. On level I, the pain is intermittently, temporary, with changeable intensity, mostly in one localization, adequate drug intake, visiting just one medical specialist, and not more than one stay in a hospital due to pain. Level II is characterized as follows: the pain during a longer time, more than one pain localization, drug abuse, changing medical consultations, and 2-3 clinical stays caused by pain. Continuous pain, pain on a large areal and changing localizations, long-time drug abuse, and more than three alterations of the medical specialist and clinical stays describe level III.
The SLR is widely used and is well suited for clinical investigations. The subject lies in a supine position with their head on the ground. The tester lifts the measured leg passively with an extended knee and ankle in the neutral position as high as possible. If the subject indicates pain or the investigator notices resistance, the investigator measures the hip flexion angle at the limit of the SLR using a plurimeter. A positive test result is associated with nerve root compression. The SLR is a reliable tool with a high intraclass reliability of 0.99 [
RS is a noninvasive technique for analysing back and spinal deformities that uses the triangulation method [
View of the raster lines on a patient’s back. Blue dots: left and right lumbar dimples. Lower red dot: dimple mid-point (DM).
The lateral shift is a lateral deviation in the frontal plane. For the calculation the perpendicular from vertebrae prominence was dropped and the difference from this perpendicular to the DM was measured.
For this study, the following parameters were measured according to Degenhardt 2017 [
(1) Pelvic tilt (PT): Difference in the height of the lumbar dimples is shown in Figure
Rasterstereographic parameters: pelvic tilt (left) and lordotic angle (right) adapted by Lippold et al. [
(2) Pelvic inclination (PI dimples): A positive value indicates the vertical component of the left dimple and the right dimple is adjusted to the top; negative values denote the opposite. This value is provided in degrees.
(3) Pelvic inclination (PI symmetry line): This parameter is a symmetry line of the spinous processes. A positive value indicates an anterior pelvic inclination and a negative value indicates a posterior pelvic inclination. This value is provided in degrees.
(4) Lordotic angle (LA): There are two tangents estimated relating to the surface of the back. The angle between surface tangents of ITL (thoracic-lumbar transition) and ILS (lumbar-sacral transition) is shown in Figure
(5) Trunk torsion (TT): This value is provided in degrees.
(6) Lateral shift (LS): This describes the difference in the translative shift (lateral shift) from L1 to DM. This value is provided in degrees. See Figure
A person with a left LS from the posterior view.
For this study, the Formetric® III 4 D system (Diers International GmbH, Schlangenbad, Germany) was applied for data collection. It can assess individual clinical parameters under static and dynamic conditions.
To avoid potential bias, the positioning of the subject was standardised. The subjects stood barefoot on a wooden platform with slightly extended knees. The upper extremities hung down lateral to the body, and the subject looked forward. One record took 6 seconds. Two pictures were taken per second. The mean of these 12 pictures of every record was used for the analysis.
The calculation of the power was based on the data of a pilot study. The difference of LS between healthy subjects and patients was 5.3 mm, the standard deviation 7.9 mm. The significance level was 0.05 and power 0.8. The statistical power analysis suggested a minimal number of 35 subjects for each group (the patients and the healthy controls). A dropout rate of 10% for the sample size was estimated; therefore four additional volunteers were enrolled in each group as a safety margin.
Mean, minimum and maximum values, and standard deviations were calculated for all parameters. The Shapiro-Wilk-Test was used to estimate the normal distribution. The independent sample
In the patient group, 39 patients with a radiologically diagnosed herniated disc were enrolled. Out of the 36 healthy controls, three volunteers had to be excluded: one volunteer reported back pain, and two volunteers had scoliosis. Scoliosis is defined as a deviation of the spine greater than 10° in the coronal plane and an axial rotation [
Characteristics of participants.
| | | | |
---|---|---|---|---|
| Patient group | 48.2 | 9.4 | .721 |
Healthy controls | 47.4 | 9.5 | ||
| Patient group | 175.1 | 10.8 | .898 |
Healthy controls | 175.4 | 10.1 | ||
| Patient group | 87.4 | 15.0 | .014 |
Healthy controls | 79.3 | 12.6 | ||
| Patient group | 28.5 | 4.5 | .002 |
Healthy controls | 25.7 | 2.9 |
Comparison between patient group and healthy controls: mean, standard deviation (SD), and
The lateral shift had a mean value of 5.6±6.0 mm in the patient group and 5.0±7.6 mm in the healthy controls. This difference was not significant (
The participants with a positive SLR demonstrated a slightly increased LS (5.5±5.0°) compared to the participants with negative SLR (5.2±8.1°). However, the difference was not significant (
The patients showed an increased pelvic tilt in [°] as well as [mm], a decreased anterior pelvic inclination (dimples [°] as well as symmetry [°]), an increased trunk torsion [°], and a decreased lordotic angle [°] compared to the healthy controls (Table
Parameters of trunk, lumbar spine, and pelvis.
| | | | |
---|---|---|---|---|
| Patient group | 5.9 | 9.2 | .016 |
Healthy controls | 2.0 | 2.4 | ||
| Patient group | 10.6 | 19.9 | .033 |
Healthy controls | 3.3 | 3.7 | ||
| Patient group | 12.5 | 7.5 | .002 |
Healthy controls | 17.8 | 6.9 | ||
| Patient group | 15.0 | 10.2 | .015 |
Healthy controls | 20.4 | 8.5 | ||
| Patient group | 7.5 | 6.2 | .017 |
Healthy controls | 4.5 | 4.1 | ||
| Patient group | 27.5 | 9.6 | .022 |
Healthy controls | 32.7 | 9.5 |
Comparison between patient group and healthy controls: mean, standard deviation (SD), and
PT = pelvic tilt; PI (dimples) = pelvic inclination (dimples); PI (symmetry) = pelvic inclination in relation to the symmetry line; TT = trunk torsion; LA = lordotic angle T12 – DM
In relation to the localization of pain, there was a significant difference in pelvic tilt in degrees (
There was a very high correlation between pelvic tilt [°] and pelvic tilt [mm] of 0.985 (
The correlation between FFbH-R and pain intensity was 0.804 (
Correlations with the FFbH-R.
| | |
---|---|---|
BMI | 0.310 | .007 |
MPSS | 0.445 | .005 |
Pain chart | 0.643 | ≤ .001 |
NRS | 0.804 | ≤ .001 |
Drug intake | 0.545 | ≤ .001 |
PDI | 0.793 | ≤ .001 |
BMI, MPSS, pain chart, NRS, drug intake, and PDI were correlated with the FFbH-R.
The correlation between the PDI and weight was 0.246 (
Correlations with the PDI.
| | |
---|---|---|
Weight | 0.246 | .033 |
BMI | 0.360 | .002 |
MPSS | 0.369 | .021 |
Pain chart | 0.623 | ≤ .001 |
NRS | 0.785 | ≤ .001 |
Drug intake | 0.379 | ≤ .001 |
FFbH-R | 0.793 | ≤ .001 |
Weight, BMI, MPSS, pain chart, NRS, drug intake, and FFbH-R were correlated with the PDI.
This study demonstrated that there is no significant LS in patients with diagnosed lumbar disc prolapse compared to healthy controls. Harrison et al. indicated a LS of the thoracic cage relative to the fixed pelvis with digitised anterior-posterior radiographs in a group of healthy volunteers [
This is the first study to evaluate the lateral shift using the rasterstereography. The findings in the present study showed a mean LS in healthy controls of 5.0±7.6 mm and 5.6±6.0 mm in the patient group. This difference was not statistically significant (
There are different methods available to measure LS, for example, the plumbline method and the shadow method [
Fritz and Georg analysed LS in patients with acute and chronic pain [
The patients demonstrated a significant different posture compared to the healthy subjects which was shown also by Khallaf [
In our study, there was a significant difference with respect to the BMI in both groups. Liljenqvist and colleagues reported that the thickness of soft tissue may result in measurement inaccuracies [
The force of gravity affects bone positions and trunk muscle activities. In the supine or standing position, these parameters are different. In patients with low back pain, the onset of symptoms typically decreases in the supine position and increases in the standing position. Therefore, an RS investigation is more functional than MRI or CT, which is often performed in the horizontal position. Some researchers have investigated LS by radiography [
RS can be applied to monitor postural changes, but caution should be taken when comparing absolute values because RS uses reference contours only. Radiological methods can derive the position of the spinous process directly from the morphology of internal bone structures.
Further research on this topic needs to be done. An investigation should be performed into other spine pathologies to find a specific pattern and to define demarcations between different pathologies.
The rasterstereography can identify changes of the posture of the spine in all three dimensions. This is the first study which illustrated the lateral shift using RS. Patients with disc herniation and low back pain show no increase in LS compared to healthy controls. Maybe, a lateral shift is more common in healthy patients as supposed. Alternatively, patients with disc herniation demonstrate other distinctive, significant parameters: an increased pelvic tilt, a decreased anterior pelvic inclination, a lower lordotic angle, and a higher amplitude of trunk torsion. In a further study, patients should be grouped, for example, based on their pathology like radiculopathy and discogenic pain to evaluate differences in posture.
Data are available upon request.
The authors declare that there is no conflict of interest regarding the publication of this paper.
We thank the Montanus-Klinik Bad Schwalbach, Germany, that it was possible to examine patients in that clinic and for all support to recruit the patients. We are thankful for the reprint permission of Figure