Effect of obesity and low back pain on spinal mobility: a cross sectional study in women

Abstract

Background: obesity is nowadays a pandemic condition. Obese subjects are commonly characterized by musculoskeletal disorders and particularly by non-specific chronic low back pain (cLBP). However, the relationship between obesity and cLBP remains to date unsupported by an objective measurement of the mechanical behaviour of the spine and its morphology in obese subjects. Such analysis may provide a deeper understanding of the relationships between function and the onset of clinical symptoms.

Purpose: to objectively assess the posture and function of the spine during standing, flexion and lateral bending in obese subjects with and without cLBP and to investigate the role of obesity in cLBP.

Study design: Cross-sectional study

Patient sample: thirteen obese subjects, thirteen obese subjects with cLBP, and eleven healthy subjects were enrolled in this study.

Outcome measures: we evaluated the outcome in terms of angles at the initial standing position (START) and at maximum forward flexion (MAX). The range of motion (ROM) between START and MAX was also computed.

Methods: we studied forward flexion and lateral bending of the spine using an optoelectronic system and passive retroreflective markers applied on the trunk. A biomechanical model was developed in order to analyse kinematics and define angles of clinical interest.

Results: obesity was characterized by a generally reduced ROM of the spine, due to a reduced mobility at both pelvic and thoracic level; a static postural adaptation with an increased anterior pelvic tilt. Obesity with cLBP is associated with an increased lumbar lordosis.In lateral bending, obesity with cLBP is associated with a reduced ROM of the lumbar and thoracic spine, whereas obesity on its own appears to affect only the thoracic curve.

Conclusions: obese individuals with cLBP showed higher degree of spinal impairment when compared to those without cLBP. The observed obesity-related thoracic stiffness may characterize this sub-group of patients, even if prospective studies should be carried out to verify this hypothesis.

Figure 1

Marker setup. Markers were placed on superior posterior iliac spines (LPSI, RPSI), on superior anterior iliac spines (LASI, RASI not visible), on spine spinous processes (S1, L3, L1, T6, T1) and on acromions (LACR, RACR).

Figure 2

Representation of markers and angles in sagittal plane during forward flexion. On the left (Figure 2A) are shown: frontal trunk inclination (αFTI), pelvic obliquity (α1), angle related to kyphosis (αK), angle related to lordosis (αL). On the right (Figure 2B) are represented: lumbar movement (α2), and thoracic movement (α3).

Figure 3

Representation of markers and angles in frontal plane during lateral bending. On the left (Figure 3A) are shown: lateral trunk inclination (βLTI), pelvic obliquity (β1), proximal curvature (PC), distal curvature (βDC). On the right (Figure 3B) are represented: lumbar movement (β2), thoracic movement (β3), and angle of shoulders (β4).

Figure 4

Lateral bending movement in frontal plane, with representation of markers (sphere: standing position, square: left bending, pentagon: right bending), and the localization of the center of rotation (CoR). On the right the code assigned to the CoR to characterize the movement. The represented normal subject was classified as Zone 1, because CoR was located between T6 and L1).

Figure 5

Lateral bending movement represented in frontal plane (C1, T1, T6, L1, L3, S1, LASI and RASI trajectories) for the different groups. On the left (Figure 5A) the "hourglass" shape of a normal subject, in the center (Figure 5B) the "cone" shape of a representative obese subject and on the right the "wider cone" shape of a cLBP subject.