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Research Review By Dr. Ceara Higgins©

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Date Posted:

July 2016

Study Title:

A literature review of clinical tests for lumbar instability in low back pain: validity and applicability in clinical practice

Authors:

Ferrari S, Manni T, Bonetti F et al.

Author's Affiliations:

Department of Molecular Medicine, University of Padova, Italy; Physical Therapy, Private practice, Treviso, Italy; Physical Therapy, Private practice, Rome,Italy; IRCCS Don Gnocchi Foundation, Milan, Italy.

Publication Information:

Chiropractic & Manual Therapies 2015; 23: 14-26.

Background Information:

Low back pain (LBP) is an extremely common problem in the industrialized world, the prevalence of which has been increasing (1). Instability is thought to be a clinical classification of LBP that clinicians should be aware of. Traditionally, overt (or structural) instability can be identified on standing lumbar flexion-extension radiographs. This condition is characterized by a loss of passive integrity, resulting in excessive vertebral translation or rotation on imaging (2). In clinical practice, we often look for and/or encounter ‘functional’ instability, which is thought to be caused by poor function of the muscles of the trunk or insufficient motor control in and around the lumbar spine (3). The distinction between these two types of instability remains controversial. Lumbar segmental (or, ‘functional’) instability, existing in the absence of defects of the bony architecture of the lumbar spine, has been cited as a significant cause of chronic low back pain. The differences between surgical instability criteria and ‘functional’ instability has also been outlined by Panjabi decades ago (13). Most manual medicine clinicians are more interested in the ‘functional’ loss of motor control than overt hypermobility/instability detectable via flexion-extension radiographs, which is typically more useful to spine surgeons.

Despite the controversy and clinical challenges surrounding the concept of lumbar instability, many tests exist. Unfortunately, we still have no gold standard test for detecting instability (neither overt, nor segmental/’functional’). This review assessed the most commonly used clinical tests for instability. These included the Prone Instability Test (PIT), the Passive Lumbar Extension (PLE) test, the Aberrant Movements Pattern (AMP), the Posterior Shear Test (PST), the Prone Bridge Test (PBT), the Supine Bridge Test (SBT), and the Active Straight Leg Raise Test (ASLR).

Pertinent Results:

Six studies were included, only two of which showed high methodological quality.

Diagnostic Accuracy of Lumbar Instability Tests:

Two studies investigated the diagnostic accuracy of clinical tests. Kasai et al. (10) looked at a population diagnosed with spinal stenosis, lumbar spondylolisthesis, or lumbar degenerative scoliosis and found that the Passive Lumbar Extension (PLE) test was the most accurate clinical test (high sensitivity and specificity), recommending that it is likely the best test to use clinically. The PLE test is performed with the patient prone. Both lower extremities are then elevated concurrently to a height of about 30 cm from the table while maintaining the knees extended and gently pulling the legs. Pain in the lumbar spine is considered a positive result (10).

When the individual parts of the Aberrant Movements Pattern (AMP) were assessed, the Instability Catch Sign (standing patient flexed forward – positive if sudden onset of lumbar pain preventing return to upright position), Painful Catch Sign (supine patient lifts both legs straight up in the air with knees straight – positive if legs fall to table due to lumbar pain when they attempt to lower them), and Apprehension Sign (asking patients if they feel a sensation of lumbar collapse because of sudden pain during ordinary movements) all showed low sensitivity, but good specificity, which suggests the need for caution in the use of these tests. As well, it is important to note that the AMP includes 5 tests that could be considered as one comprehensive test.

Fritz et al. (9) also found that the AMP tests showed low sensitivity and high specificity in a population with chronic LBP. In this group, the Prone Instability Test showed low to moderate sensitivity and specificity and the Posterior Shear Test (PST) showed poor sensitivity and specificity. The Prone Instability Test (PIT) begins with the patient prone with hips at the edge of the table and legs resting on the floor. The examiner then places down-ward (posterior to anterior) pressure through each lumbar segment to assess for a level that is hypermobile or painful. The second part of this test, as it was originally published) involves having the patient extend both legs off the floor while repeating the P-A pressure. If pain or hypermobility is reduced, this test is considered positive (EDITOR’S NOTE: I find this second part very challenging and even unnecessarily aggravating for some acute LBP patients) (8). The Posterior Shear Test is performed with the subject standing with arms crossed over the lower abdomen. The examiner stands at 1 side and places 1 arm around the subject’s abdomen, over the subject’s crossed hands. The heel of the examiner’s opposite hand is placed on the subject’s pelvis for stabilization while the index or middle finger palpates the L5-S1 interspace. The examiner produces a posterior shear force through the subject’s abdomen and an anterior stabilizing force with the opposite hand. The test is repeated at each lumber level. A positive test occurs when symptoms are provoked and is not based on the amount of intersegmental motion detected (8).

Reliability of the Tests:

Five papers looked at test reliability. A single study (4) showed good inter-rater reliability for the PLE (i.e. consistency between two different examiners). The PIT was assessed in 5 studies (4, 8, 9, 11, 12) and rated from fair to good for inter-rater reliability. However, once the 2 studies with the most severe methodological weaknesses were eliminated, that rating went up to moderate to good. The inter-rater reliability of the AMP was assessed in 3 studies (4, 8, 9) and rated from poor to moderate. Finally, the PST was only investigated by Fritz et al. (9) and showed the worst inter-rater reliability.

Clinical Application & Conclusions:

The Passive Lumbar Extension (PLE) test was found to be the most suitable test for detecting lumbar instability, as it shows excellent diagnostic accuracy and good reliability. This recommendation is based on only one study, however.

Further studies are needed to investigate the clinical utility of the PLE and other instability tests for differentiating patients with LBP.

Study Methods:

The authors used the PRISMA Guidelines (5) during the design, search, and reporting stages. Their search was done using the following criteria: Inclusion Criteria:
  • Articles published between 1972 and December 2013
  • Articles published in English, Italian, and Spanish
  • Diagnostic accuracy studies on an adult population with sub-acute or chronic low back pain where a clinical instability test (or multiple tests) were performed (dynamic radiographs were the reference test to diagnose lumbar instability)
  • Reliability studies on healthy or low back pain adult populations that considered the use of clinical tests to diagnose lumbar instability by one or more clinicians
  • Articles including data on sensitivity, specificity, or positive and negative likelihood ratios or enough data to synthesize these things
  • Studies where each test was looked at for both accuracy and reliability
Exclusion Criteria:
  • Narrative or systematic reviews, guidelines and meta-analysis
Titles, abstracts, and full text articles were reviewed by two independent reviewers, with a third reviewer consulted when consensus could not be reached. Additional references were then sought from textbooks, reference lists of included studies and an independent hand search of reference lists of other reviews. One reviewer gathered data on clinical tests including the description, score, study population, inclusion and exclusion criteria, diagnostic reference standard, differences in operationalizing the index tests, study raters, and study results (including sensitivity, specificity, LR+, LR-, and reliability). Two other reviewers verified the data collection. Two other reviewers assessed the methodological quality of the studies.

Study Strengths / Weaknesses:

Strengths:
  • The two types of included studies were assessed using different tools: the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool for diagnostic accuracy articles (6), and the Quality Appraisal of Reliability Studies (QAREL) checklist for diagnostic reliability articles (7).
Weaknesses:
  • There were a small number of articles found on any single clinical test – there simply isn’t a lot to go on in this area!
  • Studies on reliability were limited by statistical or methodological weaknesses.
  • The study populations were not homogeneous in age and, more importantly, spinal dysfunctions. This reduced the external validity of the results.
  • No descriptions of the tests investigated were provided in the article.

Additional References:

  1. Martin BI, Deyo RA, Mirza SK, et al. Expenditures and health status among adults with back and neck problems. JAMA 2008; 299(6): 656-664.
  2. Dupuis PR, Yong-Hing K, Cassidy JD, et al. Radiographic diagnosis of degenerative lumbar spinal instability. Spine 1985; 10(3): 262-276.
  3. Hodges PW, Moseley GL. Pain and motor control of the lumbopelvic region: effect and possible mechanisms. J Electromyogr Kinesiol 2003; 13(4): 361-370.
  4. Rabin A, Shashua A, Pizem K, et al. The interrater reliability of physical examination tests that may predict the outcome or suggest the need for lumbar stabilization exercises. J Orthop Sports Phys Ther 2013; 42(2): 83-90.
  5. Moher D, Liberati A, Tetzlaff J, et al. Preferred reporting items for systematic reviews and meta-analyses: the PTISMA statement. Int J Surg 2010; 8(5): 336-341.
  6. Whiting P, Rutjes AW, Reitsma JB, et al. The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews. BMC Med Res Methodol 2003; 3: 25.
  7. Lucas NP, Macaskill P, Irwig L, et al. The development of a quality appraisal tool for studies of diagnostic reliability (QAREL). J Clin Epidemiol 2010; 63(8): 854-861.
  8. Hicks GE, Fritz JM, Delitto A, et al. Interrater reliability of clinical examination measures for identification of lumbar segmental instability. Arch Phys Med Rehabil 2003; 84(12): 1858-1864.
  9. Fritz JM, Whitman JM, Childs JD. Lumbar spine segmental mobility assessment: an examination of validity for determining intervention strategies in patients with low back pain. Arch Phys Med Rehabil 2005; 86(9): 1745-1752.
  10. Kasai Y, Morishita K, Kawakita E, et al. A new evaluation method for lumbar spinal instability: passive lumbar extension test. Phys Ther 2006; 86(12): 1661-1667.
  11. Ravenna MM, Hoffman SL, Van Dillen LR. Low interrater reliability of examiners performing the prone instability test: a clinical test for lumbar shear instability. Arch Phys Med Rehabil 2011; 92(6): 913-919.
  12. Schneider M, Erhard R, Brach J, et al. Spinal palpation for lumbar segmental mobility and pain provocation: an interexaminer reliability study. J Manipulative Physiol Ther 2008; 31(6): 465-473
  13. Panjabi MM. The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis. J Spinal Disord 1992; 5(4): 390–6. discussion 7.

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