Research Review By Dr. Jeff Muir©

Audio:

Download MP3

Date Posted:

June 2021

Study Title:

Extending the straight leg raise test for improved clinical evaluation of sciatica: reliability of hip internal rotation or ankle dorsiflexion

Authors:

Pesonen J, Shacklock M, Rantanen P et al.

Author's Affiliations:

Department of Rehabilitation, Kuopio University Hospital, Finland; Department of Surgery (incl. Physiatry), University of Eastern Finland; Neurodynamic Solutions, Adelaide, Australia; Department of Physical and Rehabilitation Medicine, Helsinki University Hospital, Finland; Department of Physical and Rehabilitation Medicine, Kanta-Häme Central Hospital, Hämeenlinna, Finland; Department of Physical and Rehabilitation Medicine, Tampere University Hospital, Finland; Josip Juraj Strossmayer University of Osijek, Faculty of Medicine, Orthopaedic and Rehabilitation Hospital “Prim. dr. Martin Horvat”, Croatia; Department of Natural and Health Studies, Juraj Dobrila University of Pula, Croatia

Publication Information:

BMC Musculoskeletal Disorders 2021; 22: 203.

Background Information:

Radicular symptoms accompany low back pain (LBP) in a remarkably high percentage of cases, with some estimates suggesting that 60% of patients with LBP also present with some degree of radiating leg pain (1). The cause of this radiating pain is multifactorial, with mechanical compression comprising the most common cause, although inflammatory processes, neural adhesions, arachnoiditis or viral mononeuritis are possible, albeit less common causes (2-4).

The straight leg raise (SLR) test is the most performed physical test for diagnosis of sciatica and lumbar disc herniation (5) and is considered positive when radiating pain along the course of the sciatic nerve is reported between 30 and 70 degrees of hip flexion with the patient supine (2). As a diagnostic tool, the SLR has shown high sensitivity but also low specificity (5, 6). The addition of dorsiflexion of the ankle (also called the Bragard test or Bragard’s sign) is purported to lower the angle at which a positive SLR test is noted; however, the research on the Bragard test itself is limited.

To address the low specificity of the SLR, the authors examined the reliability (i.e. the ability to produce consistent results) of an extended SLR (ESLR) – which adds hip internal rotation and/or ankle dorsiflexion to the standard test – in low back pain patients, with and without sciatica.

Pertinent Results:

40 subjects (20 sciatic patients, 20 non-sciatic controls) were recruited for the study: 25 women and 15 men. Their average age was 41 yrs (22-64); average height was 170 cm (SD: 9) and average weight was 80 kg (SD: 23). In the sciatic group, the average SLR angle was 60° (SD: 19); for the control group it was 84° (SD: 8). Two examiners applied ESLR and SLR tests and the results were compared to a Study Controller (SC) as the gold standard.

The inter-rater agreement between the two examiners was 0.85 (p < 0.001, 95% CI: 0.71-0.99). The overall agreement between the examiners and the SC was 92.5% and 95% for Examiner 1 and 97.5% for Examiner 2. The test results were unanimous in all but 3 patients.

Agreement between the ESLR and traditional SLR was not as strong as the interrater agreement. All 20 control group patients were judged as negative by both ESLR and SLR tests. Of the sciatic patients deemed positive with ESLR, only 10/20 were positive with SLR. Of the remainder, 6/20 were deemed negative with SLR due to hip flexion reaching 70 degrees and 4/20 were negative due to pain limited to the hamstring/gluteal region. Overall agreement between ESLR and SLR was 75%, with Kappa values ranging from 0.50 (p < 0.0001) to 0.54 (p < 0.0001) for comparisons between traditional SLR and ESLR results for both examiners.

Clinical Application & Conclusions:

Based on this study, the addition of hip internal rotation and/or ankle dorsiflexion to increase tension on the neural tissues produced statistically consistent results in patients with LBP with and without sciatic. While further studies are required to validate the findings, the extended SLR shows promise as a method of improving diagnostic ability for detection of neural elements of radiating low back pain.

EDITOR’S NOTE: I think this study is useful, providing practicing clinicians with two easy modifications to add to a common and already useful clinical test – the SLR. Attempting to differentiate SLR results further with these two movements is logical and can enhance the information gleaned from this test. Assessing neural tension throughout the body is certainly a nuanced clinical task and this paper adds to our ‘assessment toolbox’.

Study Methods:

Participants:
40 patients (20 with sciatica and 20 control subjects) were recruited consecutively for the study. The Study Controller examined all patients to determine which were likely to have exhibited sciatica and a lumbar nerve root disorder. Sciatic symptoms were not required to reach below the knee to be eligible. Subjects allocated to the sciatica group were selected based on a number of criteria including patient history and clinical findings such as leg pain, neurological deficits and positive SLR and ESLR tests. Control subjects reported pain in one or more regions of the low back, greater trochanter and/or hip with or without tightness in the posterior thigh.

Evaluation: Two blinded, independent examiners evaluated ESLR on each patient. Traditional SLR was evaluated by the treating physician.

Straight Leg Tests:
The extended SLR (ESLR) test was performed using the same fundamental technique as the traditional SLR. The leg was lifted passively towards 90 degrees with the hip neutral and the knee in full extension, per the standard SLR test. When a response was evoked, the tester internally rotated the hip or dorsiflexed the ankle, based on the location of the evoked response – that is, whether proximal (buttock/hamstring) or distal (below the knee). The additional movement was designed to focus on nerve movement without moving adjacent musculoskeletal structures. To clarify, in patients reporting symptoms in the gluteal or hamstring region, the additional movement was passive ankle dorsiflexion, to a maximum of 90 degrees of dorsiflexion (referred to as distal structural differentiation for proximal symptoms – see first photo below). Hip internal rotation was utilized when the patient reported symptoms below the knee (proximal differentiation for distal symptoms – see second photo below). In each case, the angle of SLR was not modified during the additional test movements. The ESLR test was deemed positive if: 1) the patient’s clinical symptoms were reproduced with the SLR; and 2) the symptoms increased with the additional movement.
Extended SLR distal differentiation
Distal structural differentiation (ankle dorsiflexion) for proximal symptoms
Extended SLR proximal differentiation
Proximal structural differentiation (hip internal rotation) for distal symptoms

Statistical Analysis:
Inter-rater agreement between the Study Controller and each Examiner was evaluated using Kappa values. Findings were cross-tabulated and Cohen’s Kappa was used between examiners. ESLR results were compared with traditional SLR results and inter-rater agreement was again calculated using Kappa.

Study Strengths / Weaknesses:

Strengths:
  • Sample size was properly calculated and sufficient to elicit a statistically meaningful result.
  • Inter-rater agreement across ESLR and SLR were tested appropriately.
  • Methodology regarding ESLR and SLR was well-described and sufficient to attribute differences to the testing procedures.
Weaknesses:
  • Lack of a legitimate reference standard with which to compare SLR results.
  • Traditional SLR performed by treating physician and not a blinded examiner.
  • The study participants did not fully represent a realistic population-wide distribution of sciatic and non-specific low back pain.

Additional References:

  1. Konstantinou K, Dunn KM, Ogollah R, Vogel S, Hay EM. Characteristics of patients with low back and leg pain seeking treatment in primary care: baseline results from the ATLAS cohort study. BMC Musculoskelet Disord 2015; 16(1): 332.
  2. Ropper AH, Zafonte RD. Sciatica. N Engl J Med 2015; 372(13): 1240–8.
  3. Gore S, Nadkarni S. Sciatica: detection and confirmation by new method. Int J Spine Surg 2014. https://doi.org/10.14444/1015.
  4. Kobayashi S, Takeno K, Yayama T et al. Pathomechanisms of sciatica in lumbar disc herniation: effect of periradicular adhesive tissue on electrophysiological values by an intraoperative straight leg raising test. Spine 2010; 35: 2004–14.
  5. van der Windt DA, Simons E, Riphagen II et al. Physical examination for lumbar radiculopathy due to disc herniation in patients with low-back pain. Cochrane Database Syst Rev 2010;(2):CD007431. doi: CD007431.
  6. Ekedahl H, Jönsson B, Annertz M, Frobell RB. Accuracy of clinical tests in detecting disk herniation and nerve root compression in subjects with lumbar radicular symptoms. Arch Phys Med Rehabil 2018; 99(4): 726–35.

Contact Tech Support  Contact Dr. Shawn Thistle
 
RRS Education on Facebook Dr. Shawn Thistle on Twitter Dr. Shawn Thistle on LinkedIn Find RRS Education on Instagram RRS Education (Research Review Service)