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Lumbar Instability

Lower back pain has been a problem to the Westernized world for centuries. Recently published figures indicate that the escalation of its incidence shows no sign of reduction. At last count, 80% of the Westernized population will suffer some form of lower back pain, in their lifetime, and it continues to be a major contributor to increasing health costs and days lost from work.

A variety of factors have been identified, which may predispose a person to develop lower back pain. These include sedentary occupations, jobs that include bending and/or twisting, exposure to vibration and interestingly, lack of fitness.

There is a group of patients, usually very active (and most commonly sports people), who suffer from chronic lower back pain and unresolving symptoms, secondary to repetitive movements at the extremes of range. Activities include gymnastics, cricket, weightlifting, ballet and similar participations. Broadly, but ill-defined, these patients are defined as sufferers of "lumbar instability".

The term instability has been bandied around, recently, as a major cause of lower back pain. Unfortunately, very little scientific evidence exists regarding its defining objective presentation. Various concepts exist, but very little in the form of investigation, has been able to identify the entity known as instability.

Definition

A definition of instability is made by first looking at the definition of 'stable'. A stable joint is one that moves through a 'normal' range of motion, when it is subjected to a 'normal' physiological load. For the purposes of this discussion, 'normal' is defined as that which is average for that person and painfree. So, an unstable joint is one that has the same 'normal' physiological load, but moves through an abnormal, and usually excessive, range of motion. Instability may also be defined as a loss of functional competence of the soft tissues (both passive and active) that provide restraint to movement, that is, the discs, ligaments, capsules and muscles. Serious instability may result from damage to the bony elements e.g. fracture-dislocation.

There is contention as to whether there is association between instability and spondylolisthesis (Fig. 1), as well as instability and hypermobility. The term hypermobility relates to a situation where there is excessive mobility in the motion segment, but there is control utilizing the muscular system (Fig. 2). This differs from instability, in that there is very little or no muscle control of the motion segment in the unstable joint. In the hypermobility patient, treatment is aimed at improving the control of the motion segment, usually utilizing dynamic lumbar stabilization exercises.

Spondylolisthesis

Fig 1. Normal L5 on S1 presentation (left) and Grade 1 spondylolisthesis of L5 on S1 (right).

Hypermobility

Fig 2. Hypermobility seen in a young gymnast.

Another term that is being utilized, at present, is "Functional Instability". This is characterized by good structural integrity of the joint, but involving lost or impaired control of movement. This loss of muscular control may result from loss of fitness, sedentary lifestyle (including occupational and recreational activity), repetitive activity - resulting in overuse injury and muscle imbalances.

History

There is usually no direct trauma, or injury, but more so a repetitive injury. In some cases though, instability may result from a trauma e.g. fracture-dislocation. The patient may report that they are essentially painfree between exacerbations, but often will feel that their lower back is weak. These exacerbations may also be becoming more frequent, with trivial incidents now bringing on the symptoms.

Assessment

The patient will often describe a set of symptoms, which seem to be commonplace in "instability" sufferers. These include:

An arc of pain, usually into flexion, but can be other movements. This may also include      "walking up" the legs when returning from the flexed position;

Pain on relaxed postures i.e. when the muscles are relaxed;

Pain on quick movements, where there is little or no muscular control;

Excessive range of intervertebral movement at the motion segment i.e. by passive      testing of gliding motion and physiological movements;

Pain, either 'catching' or sharp, on changing positions following a prolonged period of      time;

An alternating 'list' or scoliosis, with a catch of pain when this corrected;

Often good range of motion, with some degree of pain at the end range;

X-ray findings are inconclusive, as traction spurs, posterior subluxation and excessive      translation of one vertebral body on another during flexion/extension radiography may      suggest instability, however 'functional instability' may still exist in the absence of x-     ray findings.

Radiological Studies

Two types of radiological examinations may be used to diagnose instability. The first, passive radiological examination, is non-movement orientated. A variety of findings may suggest instability, which include:

An anterior slip of one vertebral body on the adjacent vertebral body;

Traction spurs;

Disc and zygapophysial joint degenerative changes (which may include gas within the      intervertebral disc in older age groups).

As the name implies, dynamic radiological examination, relates to signs seen when the spine is subjected to movement. The common findings seen with this examination are:

Angulation of the disc space;

An anterior slip of one vertebral body on the adjacent vertebral body. It is commonly      accepted that if there is a greater than 3 mm slip, a structural instability should be      suspected.

Slip of L5 on S1 ? Instability

Spondylolisthesis. Lateral lumbar spinal radiograph in a pediatric patient shows spondylolysis with grade 1 spondylolisthesis.

Treatment Approaches

A variety of treatment methods have been discussed in relation to spondylolysis and spondylolisthesis, which may be applied to lumbar instability. These include conservative measures such as mobilization of the vertebral segment within range, not aiming to "mobilize" the unstable segment but to provide pain relief. Braces or corsets can be used to provide short term assistance to stability, but not longer than 6 weeks.

Most efforts should be made to providing the patient a programme of self-help exercises, to encourage spinal stability. These come in the form of dynamic lumbar stabilization exercises which have been shown to be effective in providing core muscle stability.

In the case of failed conservative treatment, surgery may be indicated, in the form of spinal fusion.

The concepts presented here are entirely the author's own (unless expressly stated) and do not represent the thoughts or ideas of any other person.


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