Influence of age, body mass index and waist-hip ratio on the human spine; a radiographic study of adult male subjects in Port Harcourt-Nigeria

The study determined the Lumbosacral angle (LSA) of male subjects and evaluated its relationship to age, BMI and Waist -Hip ratio. Lateral radiographs of one hundred and forty-two informed healthy male volunteers between the age of 18-60 were studied using Ferguson’s method, and analyzed with respect to age, waist hip ratio (WHR) and body mass index (BMI).. The result showed the average value for Lumbosacral angle was 34.06 0 ± 0.56 0 , the body weight was 70.34 ± 1.02Kg, and BMI was 24. 64 ± 0.38Kgm -2 . Angle values were observed to increase with age up to 32years, followed by a sinusoidal increase and decrease pattern thereafter. Significant correlations were observed between LSA and Body weight as well as between LSA and BMI (p<0.05). The Lumbosacral angle of males in Port-Harcourt, South South Nigeria is within the range of literature derived measurement values world-wide, but lower than the average reported from previous studies on other Nigerian populations.


Introduction
The normal human spine has an S shape curve when viewed from the side [see figure 1] and the point of angulation between the sacrum and lumbar spines is the lumbosacral angle.The lumbosacral angle is a spine measurement derived from the wedge angle formed when the horizontal base of the angle is parallel to the ground level and the hypotenuse of the angle is formed at the level of the superior border of the sacrum.The plane of the sacrum forms the base from which the lumbar spine takes off in its ascent and by which it achieves its balanced state a [1,2,3].
High values of BMI have been reported to be associated with exaggerated lumbar curves and low back pain [3,4,5,6,7,8].On the contrary Youdas [9] and Noh, [10] reported there was no significant relationship between BMI and LSA.In a previous research, Mi-Yeon [7] did a across-sectional evaluation of 44 females between 21-45 years, with a mean age of 30 years, and reported a significant correlation between BMI and lumbar lordotic angle, lumbosacral angle and lumbar gravity line.In a related study Sibani [11] did not find any significant correlation between WHR and lumbar Lordosis.
In the healthy spine, specific arrangements of the wedge angles result in the regional curves and this enables the spine provide resilience and enables successive vertebrae bear and transfer weight of magnitude three times that which is attainable for a straight column.[1,12,13,14] It has been suggested that in patients presenting with non-specific back pain, considerable distortion in the size and orientation of lumbosacral angle occurs.[15,16,17] In the study by Silva, [18] lower back pain was observed to be etiologically related to increase in the LSA in as high as 75% of cases.Other authors have also suggested that physical examination of patients presenting with spine problems yield best results when combined with radiographic assessment.[12,19,20,21,22,23] The current study aimed to provide country normal values of the LSA of the spine for healthy adult male Nigerians, and to find out the influence of age and body indices on these normal values.

Figure 1
Diagram of the vertebral column and main regional curves.Derived from Sandring [1]   Approval was obtained from the Ethics Review Committee of the Faculty of Basic Medical Sciences, College of Health Sciences, of the University of Port Harcourt.The study sample comprised one hundred and forty-two (142) healthy male volunteers aged 18-60 who met the inclusion criteria and voluntarily gave informed consent.
Participants were required to be Nigerians with no medical records of musculoskeletal disease, resident in the South-South geopolitical zone, and mentally fit to sign the informed consent form provided.Volunteers were properly and adequately informed about the nature, risks, benefits and confidentiality of the study.Subjects with medical history of X-ray done one month prior to the current study, as well as those with radiographic evidence of scoliosis, kyphosis, degenerative changes such as spondylosis, presence of osteophytes or disc space narrowing were excluded from the study.
The study was conducted in three well designated centers in Port Harcourt; The radiology department of the University of Port Harcourt Teaching Hospital, Image Diagnostics center, Rumuola Port Harcourt.Ashford and Patrice Clinic LTD, D-line.These are located in Port Harcourt, a large multiethnic city in Nigeria A film plate of 35 x 43 cm was used for the lumbosacral spine, with a minimum subject image distance of 100 cm.

Sampling and Sample size
The convenience sampling method was employed and the participants recruited through phone conversations, direct communication during health talks and conferences as well as by use of posters and radio.The minimum sample size was determined using formula provided by Portney and Watkins [29] , Lehana [30] and European Commission. [31]and a total of 142 subjects were used for the study

Measurement Techniques
The Ferguson's method was used to evaluate the lumbosacral angle.The five lumbar vertebrae (L1-L5) were examined and the two end plates (superior and inferior) noted.The first sacral Vertebra (S1) was carefully identified and it's end plate (SEP) noted.On a transparency paper, a line (CD) was drawn horizontal and parallel to the edge of the table, and a second line (AB) drawn through and parallel to the superior end plate (sacral base) of the sacrum, the two lines were extended to their point of intersection, which technically is the fulcrum, at the lumbosacral articulation [See figures 2a and b] The fulcrum of the transparent goniometer was positioned to align with that of the joint and the lumbosacral angle is the angle between lines B and D as shown in figures 2 and 3 above, being read from the 360°protractor fixed on the Goniometer.Data were analyzed using SPSS version 17.0 (SPSS Inc., Chicago, IL.).

Results
The results are as presented below as Range, Mean and Standard Error [Table 1], comparison test (t-test for unpaired data) was also carried out [Table 2] as well as Pearson's correlation analysis [Table 3]   LSA also showed significant correlation with BMI and body weight respectively (p<0.05).

Discussion
The purpose of this study was to determine normal reference values of the lumbosacral angles of healthy adult male Nigerians and find out if a significant relationship exists between the size of the angle and specific anthropometric characteristics such as Age, WHR and BMI.
We observed a nonlinear relationship between LSA and age of subjects.This is in line with previous reports [1,12,15] suggesting that among other factors, vertebral column morphology may be influenced by certain others which are unique to individuals.
Peleg et al. [14] via analysis of the sacral orientation angle, and using a method similar to those employed by Bogduk, [12] Cailliet, [19] Yochum and Rowe [22] reported that LSA first increases with advancing age and then falls around age 21-40 years.Also Kyu-Bok Kang et al. [27] analyzed changes of Sagittal Spinopelvic parameters in normal Koreans aged 50years and over; mean sacral slope was 37 0 with a range of 21 0 -51 0.
Other investigators [12,19,22,23,28,29,30] argued that range 25-57° should be used as normal reference values for Caucasians.However Kim [18], in a more recent study recommended 30-40° to be used as reference values.Our findings are similar to those of Legaye, [31] Monister et al. [13] and Maduforo et al. [32].The higher LSA values in males as observed by Mdufuro [32] could be as a result of differences in methodology, as subjects were older compared to those of the current study.Similarly in the study by Okpala [33] the distinction between the lumbosacral angle and lumbar lordosis angle with regards to the measurement technique applied was not made.In this study, we found a significant correlation with BMI but not with WHR.This is in agreement with other studies.[4,7,33,34,35,36]

Conclusion
This study showed that LSA of males in Southern Nigeria increases with advancing age up to the age of 32, followed thereafter by a sinusoidal increase and decrease pattern.We also established that in non-obese males, spinal health can be influenced significantly by BMI and not so by the WHR.These findings will be helpful in the planning and design of interventions aimed at restoring the normal size and shape of the lower spine in patients of different age and body indices.

Figure 2 (
Figure 2(a)-(b) Measurement of Lumboscaral angle (LSA) AB: A line drawn through and parallel to the superior end plate of the sacrum; CD: A line drawn horizontal and parallel to the edge of the table; LSA: lumbosacral angle

Table 1
Distribution of LSA by age groups The highest value of LSA was observed in subjects older than 42 years, whereas the lowest observed mean LSA occurred in age class 23-27 years.

Table 2
Independent sample t test, comparing LSA between the different age groups NS= Not significant; S = Significant; Statistically significant differences were observed among various age groups as shown in the table above (p<0.05).

Table 3
Pearson Correlation analysis