MusCles in FunCtional stability oF the luMbar spine

The Anatomy of the Lumbar Vertebral Column T he lumbar portion of the vertebral column has an ideal structure aiming at maintaining stability and mobility. This region has a solid structure designed to carry the weights of the head, the neck, the trunk and the extremities. The pains associated with this region are very common complaints affecting 80% of the population at least one time during their lifetimes. 1 The functional unit of the backbone is the smallest segment that provides for all the mechanical features of the vertebral column. Functional spinal unit consists of two neighboring vertebrae, between them lies the intervertebral disc to the anterior and bilateral facet joints to the posterior forming a triple joint complex. 2 Functional spinal unit has two segments: the anterior (static) and the posterior (dynamic). The anterior segment consisting of the two neighboring vertebral bodies and the intervertebral discs between them has the responsibility to bear weight and to give flexibility to the vertebral column. The posterior segment protects the neural structures and controls the movements of the lumbar region. 1. Transfers any external load carried by the head and the upper part of the trunk and any related bending momentums to the pelvis. 2. It allows for movements between the head, the trunk and the pelvis. 3. Maintains the integrity of the spinal cord and prevents any forces or movements that might cause damage. The lumbar vertebral column has five active vertebrae. The sizes of these vertebrae increase as we proceed distally. The lumbar vertebra constitutes 25% of the whole backbone length. When approached from the lateral, it has an angulation with a posterior concavity called the lumbar lordosis. 3 Most of the bone structures contained in the lumbar vertebrae are cancellous bones creating vulnerability for collapses due to trauma or osteoporosis. Thin but dense cortical bone usually proliferates around ligament attachment sites forming osteophytes as a result of aging. Neural arch consists of pedicles, superior and inferior facet joints and laminas. The localiza-tion of facet joints change based on the level of the vertebra. At the midthoracic region, they are located on the frontal plane whereas at the lumbar region they are on the sagittal plane. This allows for antero-posterior sliding of the facet joints thereby increasing the flexion and the extension capacity of the lower lumbar region. The superior facet joint is smaller than the inferior. It has a …