Side bending movement patterns in two different populatìon, a novel model for trunk motion analysis

Purpose The aim of this study was to test a novel technique for motion analysis data collection and reduction for trunk motion analysis in evaluating trunk side bending kinematics in two groups of young people: subjects with a referral for LBP (rLBP) and healthy subjects (hSUB) Relevance Quantitative assessment of movements at the trunk, those voluntary as well as those induced by the lower limbs, is a key factor for several rehabilitation approaches to LBP. The proposed model can meet this need in a modern approach to LBP. Methods Thirty-eight volunteers, mean age 20.7 years mean BMI 21.1, and, according to a standardized questionnaire, were divided in the two groups. Subjects were instrumented with 10 mm diameter spherical markers on the following anatomical landmarks: left and right acromio-clavicular joints (ACJ), suprasternal notch, xiphoid process, 1st thoracic (T1) and 5th lumbar vertebrae (L5). Three markers were placed on the spine respectively at 25, 50 and 75% of the length between T1 and L5, an additional marker was placed at the iliac crest height level (ICHL) (Fig1). To identify a standard pelvic reference frame, four markers were placed on left and right, anterior and posterior superior iliac spines. Qualisys motion capture system was used for marker 3D tracking during the selected task. The new proposed model (derived from IORtrunk, Gait & Posture 2006, 24 Suppl 1, S26-S27) which distinguished between a 3D thorax model, defined using 4 markers, a 2D shoulder line, and 5 different 2D segments along the spine was implemented. All these rotations were calculated both with respect to the laboratory and to the pelvic reference frame. Sagittal and frontal plane rotations were analysed for the 5 spinal segments. Results The thorax-to-pelvis maximum side bending motion exhibit no differences between rLBP and hSUB. Spinal segments between T1 and ICHL showed less movement during the task in the rLBP group when compared to hSUB group; vice-versa the spinal segment between ICHL and the pelvis showed more movement in the rLBP group when compared to hSUB group (Fig2). Furthermore, the subject from rLBP group who reported pain during the task (4 out of 38) also demonstrated large movement at the spinal segment between ICHL and the pelvis (both on left and right side bending). A trained clinician evaluated the movement pattern of the subjects, subjects who were classified as “shifter” (e.g. those using a lower lumbar pivot strategy during side bending) showed larger movement at the spinal segment between ICHL and the pelvis. Conclusions Subjects in the rLBP group and subjects who reported pain during the task shown a greater contribution to the side bending from the lower spinal segments when compared to healthy subjects. The comparison between clinical assessment and instrumental measurement seems to be coherent. Implications Although further studies are required to assess the reliability of this new technique it is our belief that the obtained results are encouraging and that rehabilitation procedures can benefit in the future from this model as a support to clinical research.