Validation of a computer analysis to determine 3-D rotations and translations of the rib cage in upright posture from three 2-D digital images

Abstract

IntroductionHuman thoracic cage posture has been of interest since ancient times, especially deformities of the rib cage [20,25,35,36,45]. In his classic texts, Breig [8][9][10] showed that human postures can cause adverse mechanical tension on the central nervous system, thus correlating abnormal posture with disease. During the past century, thoracic posture (axial translation) has been associated with the treatment of disc degeneration and prolapse [13,37,50]. Abstract Since thoracic cage posture affects lumbar spine coupling and loads on the spinal tissues and extremities, a scientific analysis of upright posture is needed. Common posture analyzers measure human posture as displacements from a plumb line, while the PosturePrintä claims to measure head, rib cage, and pelvic postures as rotations and translations. In this study, it was decided to evaluate the validity of the PosturePrintä Internet computer system's analysis of thoracic cage postures. In a university biomechanics laboratory, photographs of a mannequin thoracic cage were obtained in different postures on a stand in front of a digital camera. For each mannequin posture, three photographs were obtained (left lateral, right lateral, and AP). The mannequin thoracic cage was placed in 68 different single and combined postures (requiring 204 photographs) in five degrees of freedom: lateral translation (Tx), lateral flexion (Rz), axial rotation (Ry), flexion-extension (Rx), and anteriorposterior translation (Tz). The PosturePrintä system requires 13 reflective markers to be placed on the subject (mannequin) during photography and 16 additional ''click-on'' markers via computer mouse before a set of three photographs is analyzed by the PosturePrintä computer system over the Internet. Errors were the differences between the positioned mannequin and the calculated positions from the computer system. Average absolute value errors were obtained by comparing the exact inputted posture to the PosturePrintä's computed values. Mean and standard deviation of computational errors for sagittal displacements of the thoracic cage were Rx=0.3±0.1°, Tz=1.6±0.7 mm, and for frontal view displacements were Ry=1.2±1.0°, Rz=0.6±0.4°, and Tx=1.5±0.6 mm. The PosturePrintä system is sufficiently accurate in measuring thoracic cage postures in five degrees of freedom on a mannequin indicating the need for a further study on human subjects.

Postural Assessment Software (PAS/SAPO): Validation and Reliabiliy

“…In total, 88 pictures were taken from the anterior and posterior directions as well as from both sides. The sample size and number of pictures were chosen based on the relevant literature 20, 21,26,28,29. Pictures were taken with subjects in the standing position, and the subjects were dressed to allow the visualization of 32 anatomic points (including 14 bilateral points).…”

“…Nevertheless, studies are necessary to validate and estimate the reliability of each of these systems. Although partial validations have been conducted for several of these tools, most of these studies have only assessed specific regions of the body (not global posture assessments) or only examined small samples 20–26…”

Head and shoulder posture affect scapular mechanics and muscle activity in overhead tasks

“…Subjects were excluded if they reported a history of shoulder surgery, current shoulder pain limiting activities, upper extremity injury limiting activities, cervical or thoracic fracture, displayed functional or structural scoliosis, or excessive thoracic kyphosis (>50°) (Vialle et al, 2005). Thoracic kyphosis was calculated using the BioPrint Ò software using a validated, optimized estimation technique (Harrison et al, 2007).…”

Reliability of a Photographic Method for Assessing Standing Posture of Elementary School Students

“…Recent technology improvements have paved the way for a development of highly reliable and applicable methods, such as low-dose x-ray scanning (Lodox Systems Ltd, Johannesburg, South Africa) 15 and computer-assisted systems for the analysis of posture photographs. [16][17][18] Posture assessment by Lodox allows a direct insight into the position of bones. This makes it a more valid method than photographic assessment, which determines the position of external anatomical points.…”