Biomechanical research by Panjabi2-4 introduced a comprehensive spinal stabilization model, clinical instability and its relationship to LBP. Demonstrated spinal stabilization required composite function of: ligamentous system, muscular system, and neural control system. Emphasized the importance of small, deep muscles of the spine and neural control necessary for segmental stabilization. Previous studies emphasized global stabilization, "muscular corset" (White,M.D.) with emphasis on muscles which support the the spine from the thorax to pelvis.


"Core Trunk Stabilization" video clip

Windows Media Video file, 4.1 MB

Jull et al5 introduced a stabilization model which emphasized segmental stability and the muscles which support the lumbosacral junction. The muscles lumbar multifidus, transverse abdominis, and internal obliques provide localized segmental stability.

Concept of "Self-Bracing" mechanism introduced by Snijders6 that protects the SIJ against shear load. A biomechanical model for the equilibrium of the sacrum under load consisting of muscles, ligaments and ridges/grooves in the joint surfaces called "Form Closure". These ridges once thought to be pathological process but later determined to be a physiological adaptation to promote pelvic stability7 (Vleeming). Form closure stabilizes the lumbosacral complex without extra forces required to maintain the integrity of the system.

Vleeming8 validated the co-activation concept called "Force Closure" utilizing contraction of the gluteus maximus and latissimus dorsi muscles to transfer load through the thoracolumbar fascia to produce compressive forces to the SIJ via this "posterior sling". Force closure requires external forces to maintain the integrity of the system. The sacrotuberous ligament and it's attachment to the biceps femoris, gluteus maximus, piriformis, quadratus lumborum,rectus abdominis, psoas(major) play an important role in the dynamic stabilization by compressive forces on the SIJ complex. Transverse addominal, external oblique muscles are important for self-bracing of the SIJ specifically in a stooped posture.9

Neural control is a subsystem of spinal stability often overlooked by clinicians. Panjabi introduced a model of spinal stability consisting of : neural motor control, spinal column (osseous/ articular structures, ligaments) and spinal muscles. The neural control systems programs the spinal muscles to respond to sensory input to maintain spinal postural control or intersegmental stability.

References:
  1. Guide to Physical Therapist Practice. 2nd ed. Phys Ther. 200181.
  2. Panjabi,M 1992. The Stabilising System of the Spine. Part 1. J Spinal Disorders 5:383-389.
  3. Panjabi M 1992. The Stabilising System of the Spine. Part 2. J Spinal Disorders 5:390-397.
  4. Panjabi M 1994.Lumbar spine instability: A Biomechanical challenge. Current Ortho 8:100-105.
  5. Richardson C, Jull G, Hodges P, Hides J 1999. Therapeutic Exercise for Spinal Segment Stabilization in Low Back Pain: Scientific basis and Clinical Approach. Churchill Livingstone.
  6. Snijders, Spine. 1990;15(2) 130-132.
  7. Vleeming. Spine. 1990;15(2) 130-132.
  8. Vleeming. Clin biomech. 1993;8:295-301.
  9. Vleeming. Clin biomech. 1989;4:204-209.