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Research Article | DOI: https://doi.org/
*Corresponding Author:
Citation:
Copyright: © Kha Tia 2018 et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Received: 25 March 2018 | Accepted: 02 April 2018 | Published: 09 April 2018
Keywords:
Several clinical tests have been proposed on low back pain (LBP), but their usefulness in detecting lumbar instability is not yet clear. The objective of this literature review was to investigate the clinical validity of the main clinical tests used for the diagnosis of lumbar instability in individuals with LBP and to verify their applicability in everyday clinical practice.
The lumbar spine, although often described as a single functional unit, is composed of five vertebrae forming what are called "motion segments" connected in series [2]. Each motion segment consists of two adjacent vertebral bodies and the connecting ligament [3]. It is the smallest functional unit of spine exhibiting biomechanical characteristics similar to those of the entire spine [2]. During spinal movements, the adjacent vertebrae maintain their relationship with each other due to configuration, orientation and integrity of facet joint complexes, the integrity of various ligamentous structures and due to the highly specialized connective tissue structure, the intervertebral disc [4]. Translation and rotation can occur at each spinal motion segment during lumbar spine movements in any of the cardinal body planes [2]. The maintenance of stability of the lumbar spine during these movements requires the coordinated movements of multiple motion segments, and a lack of stability may potentially occur at any lumbar segment in either translational or rotational movements, or both [5].
Unfortunately, the traditional teaching about instability is generally restricted to spondylolysis and resultant listhesis to the extent that many of the surgeons even refuse to believe that anything else could be an instability [4]. In this study, we try to determine this little fraction of instability due to mechanical causes other than spondylolisthesis along with the incidence of secondary lumbar instability at the operated spinal segments following standard surgical procedures like discectomy and decompressive laminectomy in patients with no obvious spondylolisthesis or instability preoperatively.
Concepts of Chronic Lumbar Instability Mechanical
A number of studies published since the symposium have focused on the relevance of radiographic findings, including X-rays and magnetic resonance imaging (MRI), for the diagnosis for mechanical instability. The use of flexion–extension X-rays is relatively common, but the ability to identify instability has had mixed findings.13–15 The use of side-bending X-rays is thought to provide minimal additional information related to the amount of angular motion and instability.14
The use of MRI to assist in diagnosing lumbar spine dysfunction has increased in the past two decades. The degree of disc degeneration, using standard MRI, is not thought to correlate with the amount of angulation (> 15°) or segmental instability (> 3 mm translation).16 Findings have differed when dynamic MRI is used to examine motion in a standing position.17 The degree of disc and facet joint degeneration has a positive association with excessive translational motion while the degree of facet joint degeneration has a negative association with excessive angular motion.17 These findings are similar to a previous study that indicated that zygapophyseal (facet) joint oedema was associated with the presence of instability on flexion–extension radiographs.18 Other spine pathology such as annular tears (+LR = 6.26, −LR = 0.83) or traction spurs (+LR = 6.58, −LR = 0.89) identified using standard MRI has also been associated with segmental instability (> 3 mm translation) on X-ray.19 It does appear that with more severe disc degeneration (grade V), there is a lesser amount of excessive angular and translational motion when compared to lower grades of disc degeneration.17 This lends support to Kirkaldy-Willis’s proposed degenerative cascade restabilization phase.20
Construct of instability
Terminology associated with a diagnosis of instability may be further clouded depending on the perspective of the medical professional (orthopaedic surgeon versus physical therapist). Using established terminology from the extremities may help decrease confusion. Individuals with chronic ankle instability have been described in different groups as having mechanical and functional ankle instability.24 Regardless of the affected region, mechanical instability refers to disruption of the passive stabilizers and decreased structural integrity while functional instability refers to a lack of neuromuscular control of the joint during activities.24 We propose the designation of chronic lumbar instability (CLI), which would include the subcategories of mechanical lumbar instability (MLI) and functional lumbar instability (FLI).
Clinical tests for instability
Certain subjective and objective examination findings may be used to identify lumbar spine clinical instability. A Delphi survey was conducted of physical therapists who were either board-certified in orthopaedics with the American Physical Therapy Association or Fellows in the American Academy of Manual Physical Therapists to determine consensus regarding the existence of specific examination criteria for the identification of lumbar spine clinical instability.25 Consistent subjective measures included a history of painful locking or catching during spinal motion, pain on return from forward bending, pain during transitional activities, pain with sudden or trivial activities, problems with unsupported sitting, or pain that worsens with sustained positions. Respondents consistently identified the following objective findings as the strongest predictors of clinical lumbar instability: muscle dysfunction, motor control abnormalities, and strength losses.
Materials and methods
A cross-sectional study with a prospective follow-up of 41 patients between 30 and 65 years of age visiting the outpatient clinic of our hospital due to low back pain with or without radiation into the lower extremities was conducted. They were subjected to a neutral anteroposterior (AP), lateral, flexion-extension and oblique X-rays of lumbo-sacral (LS) spine. Patients excluded were those who had a contraindication to radiographic assessment (e.g., pregnancy), spondylolisthesis, previous lumbar surgery, spinal trauma, spinal tumors including metastasis, osteoporosis with compression fractures, or unable to actively flex and extend the spine adequately due to pain or muscle spasm. All procedures performed were in accordance with the ethical standards of the institutional research committee. Informed consent was obtained from all individual participants included in the study. The patients were divided into two groups:
Group A (treated conservatively) included 23 patients (13 males and 10 females) with a mean age of 46.7 years. The mean duration of symptoms was 6.3 months. These patients were treated conservatively with analgesics, physiotherapy, back and abdomen strengthening exercises, lumbar traction, etc. at the time of evaluation and may or may not have required surgery in future. This group with low backache, not due to spondylolisthesis, was studied to determine the prevalence of instability.
Group A (Non-operated/pre-operative)
Out of 23 patients in the non-operated group A population, four patients (17.4%) had an evidence of radiological instability which was mainly due to the angular rotation and none had an instability caused by sagittal translation. The incidence of instability at each of the motion segments along with respective mean angular rotation and sagittal translation is summarized in Table 1. L4-L5 segment had the highest amount of mean angular rotation and sagittal translation.
Mean ST (% of vertebral body width)
Angular instability (% of Group A subjects)
Translational instability (% of Group A subjects)
Pearson coefficient (r-value)
Table 2: Table showing correlation of age with angular rotation (AR) and sagittal translation (ST) at each of the motion segment.
Conclusions: The quantification of normal and abnormal spinal motion is likely to be still dependent on imaging. If patients with spondylolisthesis were excluded from the study, instability still existed in patients with low back pain mainly because of rotational component in sagittal plane. Younger subjects had greater angular rotations and it decreased as the age progressed. Determination of the relationship between imaging instability and its symptoms remains challenging if not impossible. We did not find any significant correlation between spinal signs and symptoms considered and radiographic instability.
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