114


PART II THE VERTEBRAL COLUMN


iliacus muscle. The distal end of the psoas merges with the iliacus muscle that runs from the iliac crest to the lesser trochanter. Both muscles are principal hip fl exors, moving both the femur on the pelvis and the pelvis on the femur. However, the psoas plays a role as a vertical stabilizer of the spine as it compresses the lumbar seg- ments providing spinal stability during hip fl exion. The iliopsoas is discussed in greater depth in Chapter 11.


Thoracolumbar fascia


Transversus abdominis


Posterior rectus sheath


Inguinal ligament


A


SPINAL MUSCLE STABILIZATION AND ALIGNMENT


Transversus abdominis


Multifidus


Quadratus lumborum


Iliac crest Lateral


Intertransversarii B


Figure 5.34 (A) Transversus abdominis and its attachment to the thoracolumbar fascia. (B) Transversus abdominis and its relationship to multifidus.


thoracolumbar fascia. Its contraction also plays a role in stabilization of the SI joints. The internal and external oblique muscles and the transversus abdominis form a type of internal, corset-like support of the thoracolumbar spine, with the abdominal wall as the anterior section and the thoracolumbar fascia and muscle attachments forming the posterior section (Fig. 5.34). Although not a muscle directly associated with the spine, the iliopsoas plays a role in pelvic motion and infl uences spinal kinematics. The muscle consists of two portions. The psoas muscle originates in the lumbar area and attaches to the lesser trochanter of the femur and the


The transversus abdominis, internal oblique abdominal, and deep lumbar multifi dus muscles all stabilize the spine in healthy people. The transversus abdominis stabilizes the SI joints and the lumbar spine. Both the transversus abdominis and the internal oblique muscles stabilize the trunk before rapid movement of the extremities. The multifi di are effective segmental lumbar vertebrae stabi- lizers. These muscles compress and control shear forces between vertebrae and contribute to fi ne control of seg- mental motion. Without this intrinsic control, vertebral segments can become unstable, often resulting in pain and dysfunction. People with acute and chronic low back pain often display signifi cant atrophy in the multifi di that can occur within days of the onset of symptoms. Activation of the transversus abdominis and multifi di is often ineffective or absent in people who have back pain. Training the spinal stabilizer muscles using specifi c exer- cises to strengthen the lumbar multifi di and transversus abdominis muscles is often incorporated into rehabilita- tion programs for people with low back pain. Lumbar stabilization exercises are designed fi rst to activate the deep lumbar stabilizers and then progress to contraction of the primary trunk movers (Fig. 5.35). Postural alignment plays an important role in mini- mizing stresses to the spinal joints that can result in degenerative changes, leading to arthritis, pain, and dys- function. Any posture or position that exaggerates the normal curves of the spine overstretches muscles and connective tissue on one side of the curve, producing weakness, and shortens these structures on the opposite side of the curve. An example of this concept can be observed in a person in a slouched sitting posture. As depicted in Figure 5.36A, this position affects the cervi- cal, thoracic, and lumbar spines. Because of the exces- sive lumbar fl exion with the decreased lumbar lordosis and increased thoracic kyphosis, the cervical spine is in fl exion anterior to the thoracolumbar vertebrae. To view the computer, the person extends the occipital vertebrae to take the eye level from a downward orientation. The cervical spine is in a protracted posture (lower cervical fl exion and occipital extension), which can result in spinal pain and dysfunction and upper extremity symptoms. By moving the cervical spine into a retracted position (lower


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