Video based measurement of sagittal range of spinal motion in young and older adults

Abstract

A revised model of skin marker placement with the two-dimensional (2D) PEAK Motus system was used to investigate the effect of aging on sagittal range of spinal motion. Twenty-four healthy young adults and twenty-two healthy older adults were videotaped while performing the movements of flexion and extension in each spinal region — cervical, thoracic and lumbar spine. Alternative movement tests that may allow a greater range of motion (ROM) for thoracic extension and lumbar flexion were also investigated. Older adults demonstrated significantly decreased flexion/extension ranges in the cervical, thoracic and lumbar spine. The movement of cat-stretch in the all-fours position allowed greater thoracic extension, and the movement of toe-touch in standing permitted greater lumbar flexion. This study provides reference data for sagittal ranges of spinal motion in healthy young and older adults as measured by a 2D imaged-based system. The sagittal model of skin marker placement used in this study can have a broader application for ROM measurement in the clinical setting using a digital camera and freely downloadable software.

Introduction

Knowledge of the expected range of motion (ROM) in healthy subjects provides the basis for assessment and for establishing appropriate treatment goals in clinical practice. Radiographic methods are considered the ‘gold standard’ for ROM measurement (Portek et al., 1983), however the risk of radiation exposure limits its use. Previous studies agree that increasing age is associated with decreased spinal motion, however the descriptive information provided from simple clinical tools (Loebl, 1967, Moll and Wright, 1971, Kuhlman, 1993) has frequently been jeopardized by measurement issues. For example, the Schober tape measure method (Moll and Wright, 1971) provides an index of lumbar movement (in cm) reported as unreliable (Portek et al., 1983, Miller et al., 1992). Use of a single inclinometer positioned over a specific spinous process (e.g. T12/L1) is gravity referenced, and thus only indicates the orientation of the body segment in space, with the angle being dependent on the position of the more caudal body segments. The dual inclinometer method provides more valid and accurate measurement for lumbar flexion (Loebl, 1967, Saur et al., 1996), however the reliability of measurement for lumbar extension has shown to be low (Merritt et al., 1986, Dillard et al., 1991).

In contrast, a motion analysis system that tracks the displacement of reference markers attached to the skin over relevant bony landmarks can provide more reliable and accurate measurement of human movement. However, previous ROM studies have been compromised by problematic models of marker placement. For example, Hu et al. (2006) placed markers over a swimming cap and a sleeveless shirt to measure ROM in the cervical spine. Possible stretch or slide of the cap and clothes as well as skin movement errors likely influenced the validity and reliability of the data. In addition, the cervical spine was measured as a whole without acknowledging the functional differences between the upper and lower cervical regions. Also, in most surface-based studies information regarding ROM has been limited to a single spinal region (Dvorak et al., 1995, McGill et al., 1999, Sforza et al., 2002, Wu et al., 2007), with no attempt to determine the mobility of adjacent regions in this functionally interdependent chain of joints.

Another factor influencing the ROM is test movement. The clinical tests for lumbar flexion and extension are often performed in standing, and patients with balance problems may have difficulty achieving full lumbar extension. Similarly patients attempting thoracic extension in sitting tend to lean backwards from the hips so that the full available thoracic movement is not achieved. An alternative test movement may be provided by the ‘cat-stretch’, a common spinal ROM exercise performed in the all-fours position (Fig. 1). Patients arch their back upward and downward accompanied by coordinated head movement while kneeling on the hands and knees. When patients hollow their back, the end position is achieved by simultaneous extension of the thoracic and lumbar spine. The opposite movement, arching the back toward the ceiling, is comprised of thoracic and lumbar flexion. The movement of cat-stretch in the all-fours position is stable, allows the normal movement interaction between the spinal regions, may permit a greater range of thoracolumbar motion, and also minimises the trouble of changing test positions.

Therefore, the aim of this study was to use our previously developed two-dimensional (2D) model of marker placement (Tully and Stillman, 1997) with the 2D PEAK Motus video analysis system (PEAK Performance Technologies Inc., Englewood, Colorado, USA) to establish reference values for sagittal ROM in all spinal regions, and to investigate the effect of aging on regional mobility. The second aim of this study was to investigate the feasibility of an alternative movement, cat-stretch, for testing ROM in the lumbar and thoracic spine.