EVALUATION OF GEOMETRIC PARAMETERS OF LUMBOSACRAL VERTEBRAE

CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
The vertebral spine presents regional curves on sagittal plane designed to absorb impact, reduce its longitudinal stiffness and intensify muscular function (Gelb et al., 1995). Values of sagittal curve measurements on spine present great variability in normal individuals often with a wide range of variation. The lumbosacral region is the most important region in the vertebral column in terms of mobility and weight bearing. It is lordotic in the cervical and lumbar vertebrae, and kyphotic in the thoracic and coccygeal vertebrae. However, pathological conditions can alter these curvatures. The correlation between lumbosacral geometry and the incidence of low back pain has been established (Azar et al., 2009; Evcik and Yucel 2003; Sarikaya et al., 2007). The shape of the lumbosacral spine has been reported to be of importance in the occurrence of the low back pain (Lord et al., 1997; Fernand and Fox 1985).
Low back pain (LBP) is a highly common problem and causes much morbidity and socio-economic loss in the community (Dincer et al., 2007) with a lifetime incidence of between 50% and 90%. Therefore evaluation of the lumbosacral geometry is one parameter that is of importance in evaluating the possible etiology of low back pain (Lord et al., 1985). The radiographic parameters evaluated during an assessment of the lumbosacral vertebrae are:
·        Lumbosacral Angle (LSA),
·        Lumber Lordosis Angle (LLA),
·        Sacral Inclination Angle (SIA) and
·        Lumbosacral Disc Angle (LSDA).
Some studies have reported significant associations between some of the radiographic parameters and certain demographic and anthropometric factors (Lord et al., 1997; Fernand and Fox 1985; Amonoo-Kuofi 1992). However, the literature is still ambivalent with respect to an association between these radiographic parameters and certain anthropometric and demographic factors.
1.2     AN OVERVIEW OF THE RELEVANT BONY ANATOMY OF THE LUMBAR SPINE AND SACRUM 
1.2.1   Vertebral Column
The vertebral column also referred to as the human spine is a curved linkage of individual bones or vertebrae. It is a very complicated musculoskeletal structure containing various soft and hard tissues. The vertebral or spinal column is a composite anatomical structure made of a string of 33 bones each known as a vertebra. They are connected by a mass of cartilage called inter-vertebral disc. The vertebral column is also the attachment site of various spinal muscles and ligaments which provide the structural stability of the entire vertebral column. The spinal canal located in the posterior region of the vertebral column functions as a protective shell of the delicate spinal cord. The adult vertebral column consisting of 33 vertebral segments accounts for approximately 48% of the overall body length. Although the usual number of vertebrae is 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4 coccygeal, this total is subject to frequent variability, and there have been reports of variation between 32 and 35 bones. The sacral region consists of 5 fused vertebrae while the coccygeal region is made of 4 fused vertebrae. A typical vertebra has a ventral body, a dorsal vertebral (neural) arch, extended by lever-like processes, and a vertebral foramen, which is occupied in life by the spinal cord, meninges and their vessels (Andrew Williams et al., 2004).In keeping with the geometrical features of the vertebrae, the vertebral column is divided into five sections (fig 1.1), namely;