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Lumbar Tactile Acuity in Experimentally Induced Acute Low Back Pain (NCT03021278)

Universitätsklinikum Hamburg-Eppendorf
The purpose of this study is to determine whether experimentally induced acute low back pain might lead to alteration in lumbar tactile acuity measured in region affected by pain compared to pain-free side and pain-free controls.
  • Other: Saline injection
    In the saline injection group, low back pain will be induced via 1.0 ml hypertonic (5% NaCl) saline bolus injection which is a commonly used model of acute low back pain. Saline will be injected into the right (or left) lumbar longissimus muscle 50 mm lateral to the spinous process just above (5 mm) previously marked point. Injections will be performed by a physician under ultrasound imaging guidance to ensure that each single injection will be equally placed at a depth of 30 mm. The side for the pain induction will be randomised across subjects. The place of needle insertion and corresponding point on the opposite side of the body will be covered by placing a small piece of adhesive plaster.
    • Experimental pain
  • Other: Sham injection
    In the sham-injection group (placebo comparator), a real needle will be shown to the participants to imitate and produce the anticipation of a pain experience. A pinprick sensation will be produced by a weighted stimulus applied perpendicularly to the skin just above without piercing the skin. A stimulus of 512 mN will be used to produce a pinprick sensation and activation of cutaneous nociceptors. Adhesive tapes covering stimulation points will also be provided.
    • Sham pain
Ages eligible for Study
18 Years to 35 Years
Genders eligible for Study
Accepts Healthy Volunteers
Accepts Healthy Volunteers
Inclusion Criteria:
  • Only participants with similar mechanical detection threshold (MDT) on both sides of the spine will be included.
Exclusion Criteria:
  • sex: female
  • age < 18 or > 35 years
  • laterality: left-handed
  • current pain experience
  • episodes of back pain lasting more than 24 hours within the previous one-month period
  • history of chronic pain, i.e. pain lasting more than one-month
  • comorbidities affecting the nervous system
  • cardio-vascular diseases
  • psychiatric illnesses
  • any disease requiring systematic drug consumption.
  • diagnosed hypersensitive reaction to saline solution
Healthy male participants will be recruited at the Academy of Physical Education in Katowice. Each participant will be assessed only once. All participants will be asked to provide written informed consent for participation prior to the experimental procedure and will be naïve to the experimental hypothesis. The plan for this research project has been previously approved by the local bioethical committee.

Between-subject (real-injection, sham-injection and control group) and within-subject (assessment 1 versus assessment 2 and 3) design will be used for the purpose of this experiment. After the screening procedure and preparation phase, participants will be randomly assigned to one of three groups: control, saline injection or sham-injection. Groups will differ only in terms of the specific manipulation: the experimental group will receive intra-muscular saline injection, the sham-injection group will be stimulated by pinprick sensation produced by a PinPrick device. No manipulation will take place in the control group allowing to control for the learning effect. In fact, participants will be informed that the study includes only two branches so they can be assigned either to the group with pain evoked as a result of an injection or to the control group without any noxious stimuli. Not revealing the sham-injection condition will allow for comparison between nociceptive (injection) and non-nociceptive (sham-injection) condition.

Because no previous studies have investigated tactile acuity changes in acute low back pain, the sample size calculation was based on the data from our own systematic review and meta-analysis (Adamczyk et al., under review) and previous cross-sectional data among healthy controls (Adamczyk et al., 2016). Based on reported mean difference of 9.49mm between chronic low back pain patients and healthy controls and standard deviation of 9.90mm, a total sample size of 57 participants (19 per group) is required to detect a significant effect. Power calculation was performed for specific planned-comparison tests that were described in detailed under 'statistical analysis' section below. Calculation was performed in G*Power (G*Power statistical software) with the alpha level set at =0.05 and 80% power.

Baseline differences in descriptive statistics will be analysed by one-way analysis of variance (ANOVA) with 'group' as the between-subject factor. Further statistical comparisons will be performed using a repeated-measures ANOVA design, with 'group' (real-injection, sham-injection, and control group) as between-subject factor and repeated measures (assessment 1, 2 and 3) as a within-subject factor. In order to test hypothesis on tactile acuity alteration during pain induction, F-tests will be followed by planned comparisons on data from assessment 1 versus assessment 2 in experimental group. To determine whether the magnitude of tactile acuity alteration has differed between the groups, planned comparisons will be performed on the difference in tactile acuity (assessment 1 vs. assessment 2) between real-injection and sham-injection group and between real-injection and control group. Bonferroni correction will be used for multiple planned comparisons. Forward, stepwise multiple regression will be performed to determine the degree to which tactile acuity change is predicted by either pain intensity or the size of its distribution. All the analyses will be conducted using the STATISTICA data analysis software, version 12 (StatSoft Inc., Tulsa, OK, USA). The level of significance will be set at p < 0.05.

1 locations

Poland (1)
  • The Jerzy Kukuczka Academy of Physical Education
    Not specified
    Katowice, Poland, 40-065
31 December, 2016
26 July, 2017
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