Lumbar And Lumbopelvic Stabilisation

The management and prevention of low back pain has historically presented a challenge to treating therapists. Therapeutic exercise has been an integral part of the treatment approach in an attempt to restore muscle function, assist in pain relief and prevent recurrent episodes. The efficacy of general back exercises however, appears somewhat limited in achieving these goals (Koes et al 1991).

Major developments in research and a greater understanding of motor control and segmental stabilization in back pain patients, has lead to a more specific exercise strategy. This approach has been found to influence the recovery of both acute and chronic back pain patients (Jull et al 1993, 1995, Hodges et al 1996, O’Sullivan et al 1997, Richardson et al 1995).

In 1992, Panjabi introduced a conceptual model of the spinal stabilisation system, one that describes the interaction between components providing stability in the spine. This model redefined the notion of spinal instability in terms of a region of laxity around the neutral resting position of a spinal segment, that he terms the ‘neutral zone’. This is in contrast to the traditional definition that has been more aligned with abnormal ranges of motion at the end-point of the range. There is some evidence that the neutral zone can be increased in cases of intervertebral disc degeneration, spinal injury and spinal fixation (Kaigle et al 1995, Mimira 1994, Panjabi 1992), and decreased with effective muscle control across a motion segment (Cholewicki and McGill 1996, Wilke et al 1995, Gardner-Morse et al 1995).

The size of the neutral zone is considered to be of major significance in determining spinal stability, and is influenced by the interaction between the systems of Panjabi’s model.

The model is comprised of three systems, all of which contribute to active stabilisation:

• Passive Sub-System: osseous / articular / ligamentous structures
• Active Sub-System: spinal muscles and tendons
• Neural Sub-System: Central nervous system and nerves coordinating and controlling the Active Sub-System

Based on this model, Panjabi (1992) suggests that the 3 sub-systems are interdependent components of the spinal stabilisation system with one capable of compensating for deficits in the other. Back pain can occur as a result of deficits in the control of the spinal segment when abnormally large segmental motions cause compression or stretch on neural structures, or abnormal deformation of ligaments and pain-sensitive structures. Potentially, a dysfunction in any of the 3 systems may lead to these deficits.

Panjabi (1992) went on to define spinal instability ‘as a significant decrease in the capacity of the stabilising systems of the spine to maintain the intervertebral neutral zones within physiological limits so that there is no neurological dysfunction, no major deformity, and no incapacitating pain.’ Instability within this broader definition and encompassing 3 interrelated systems may therefore relate also to an insufficiency of the muscular system.

Bergmark (1989) categorised the trunk muscles into local or global muscle systems depending on their main mechanical roles in stabilisation. The global muscle system is comprised of large torque producing muscles that act on the trunk, spine and pelvis without direct attachment. The local muscle system consists of those muscles attaching directly to the lumbar spine and is responsible for segmental stabilisation. It is the function of the local, deep muscles of the lumbar spine that contributes to the concept of neutral zone motion control.

Such work by Pool-Goudzwaard et al (1998), (Vleeming et al (1990a, 1990b, 1995) and Snidjers et al 1993, 1997) introduces the dimension of muscular control around the sacroiliac / pelvic region, in order to augment force closure in a region that is otherwise biomechanically susceptible to both vertical and horizontal translations. This force closure is dependant on both the inner (local) and outer (global) muscular systems to maintain compression through the pelvic complex to enhance stability in this region.

According to current literature, it is apparent that the role of such muscles as multifidus, transversus abdominus, diaphragm and pelvic floor, as well as those muscles working across the pelvic region, play an integral role in the dynamic stability of the lumbar and lumbopelvic regions (Hides et al 1996, Hodges and Richardson 1996, Hodges et al 1997, Sapsford et al 2001).

A definite link has been established between dysfunction in the local muscle system and back pain (Hides et al 1994, Rantanen et al 1993, Hodges and Richardson 1995). This has lead to a concept of therapeutic exercise to enhance lumbar and lumbopelvic stabilisation, based on the specific rehabilitation of both the global, and importantly, the local muscle system. Such an approach must address the timing of recruitment, strength and endurance of specific muscles, firstly in isolation and progressing through to an automated and functional contraction with other synergists to support this region under various loads.

Jenny Hynes, Physiotherapist