No immediate changes on neural and muscular mechanosensitivity after first rib manipulation in subjects with cervical whiplash: A randomized controlled trial

1 Title: No immediate changes on neural and muscular mechanosensitivity after first rib manipulation in subjects with cervical whiplash: A randomized controlled trial Short Title: Rib manipulation in cervical whiplash Authors: Marta Peña-Salinasa, Jesús Oliva-Pascual-Vacaa,b, Alberto Marcos Heredia-Rizoa, Cleofás Rodriguez-Blancoa, François Ricardc, Ángel Oliva- Pascual-Vacaa,* a Department of Physical Therapy, Faculty of Nursing, Physiotherapy and Podiatry, University of Sevilla, Sevilla, Spain. b Department of Physical Therapy, Universitary School of Osuna, Sevilla, Spain. c Madrid Osteopathic School, Madrid, Spain. *Corresponding Author: Ángel Oliva-Pascual-Vaca. C/ Avicena s/n, 41009 Sevilla, Spain. E-mail: [email protected] Tel: +34 954482168 Fax: +34 954486528 2 Abstract BACKGROUND: Upper rib manipulative therapy appears to be effective on primary complaint of shoulder pain, but its efficacy has not been evaluated in subjects with whiplash-associated disorders. OBJECTIVE: To assess the immediate changes on neural and muscular mechanosensitivity after first-rib manipulation in patients with neck or cervicobrachial pain secondary to cervical whiplash (CW). METHODS: A single-blind (evaluators were blinded to subject allocation) randomized trial was conducted. Fifty-three (N=53) subjects, 34.7 (SD 10.8 years; 56.6% females), with cervical or cervicobrachial pain following CW, were distributed into two groups. The experimental group (n=27) underwent a single first-rib high-velocity low-amplitude manipulation technique, while the control group (n=26) received a sham placebo intervention. Outcome measures were taken at baseline and immediately after intervention, of the pressure pain threshold over the trigeminal, median and ulnar nerves, and over the area described for the location of tense bands in the upper trapezius, masseter, biceps brachii and triceps brachii muscles. RESULTS: No significant differences in mechanosensitivity values were observed after intervention in the between-groups comparison (p>0.05). CONCLUSION: The use of a sole first-rib thrust technique has no immediate effect on neural or muscular mechanosensitivity, when compared to placebo, in subjects with cervical or cervicobrachial pain after CW. 3 Keywords. Brachial plexus, Manual therapy, Pain threshold, Ribs, Whiplash injuries 4 1. Introduction Cervical whiplash (CW) is the most common trauma following motor vehicle collisions, being a serious problem for its level of incidence, the long-lasting symptoms, and the economic burden involved [1]. Even though most of whiplash patients recover within 3 months of the accident, little improvement is expected after that [2]. Persistent neck pain is the predominant symptom within chronic whiplashassociated disorders (WAD), and usually radiates to the head, shoulder girdle, and upper limb areas [3], with 60% of patients reporting cervicobrachial pain in the chronic stage [4]. The prevalence and incidence of temporomandibular disorders has also been found to increase after whiplash trauma [5]. Headache is present in 50% to 70% of individuals in the acute CW phase [6], and chronic headache attributed to whiplash injury ranges from 8% [7] to 30% of cases [6]. Among the possible underlying mechanisms to explain chronic WAD, central sensitization (an increased sensitivity of the nervous system) [8], and widespread hypersensitivity [9], are widely accepted. Reduced pain thresholds at the head, neck, thoracic spine and upper and lower limbs [10], along with changes in neural mechanosensitivity patterns [11], are measures of altered central pain processing in chronic WAD. Current evidence suggests a potential effect of spinal manipulative therapy (SMT) on neuromuscular excitability [12], and pain central mechanisms [13]. The use of spinal manipulation has been purported to improve self-perceived pain and pressure pain sensitivity in chronic mechanical neck pain [14,15]. There seems to be, however, no clear evidence to support any intervention for WAD [16], 5 although conservative approaches (including manual therapy) seem to decrease pain and improve functionality in the acute stage [16]. SMT may help to accelerate the recovery process [17], and it has shown to relief head, neck and upper thoracic pain in subjects with WAD [18]. The use of upper rib and spinal thrust manipulation, either alone [19], or in combination with usual medical care [20], is effective on patients with primary complaint of shoulder pain. In chronic WAD, a sustained scalene muscles spasm may pull the first rib up [11], which could affect the brachial plexus. No previous study has evaluated the possible impact of upper rib thrust manipulation in subjects with WAD. Therefore, the main aim of the trial was to observe the immediate changes on neural and muscular mechanosensitivity after a highvelocity low-amplitude first-rib thrust manipulation, when compared to placebo, in individuals suffering from cervical or cervicobrachial pain secondary to CW. 2. Methods 2.1 Study Design A controlled, single-blinded (subject allocation to the study groups was blinded to the evaluators) randomized trial was carried out. The study has been conducted in agreement with the CONSORT statement. 2.2 Participants and Eligibility Criteria Participants were recruited from a private medical centre. Sixty-four consecutive patients, who were diagnosed as suffering from cervical or cervicobrachial pain following CW trauma after a motor vehicle collision, were 6 selected. Eleven participants were excluded for several reasons. The final sample comprised a total of 53 participants (30 women and 23 men), mean age 34.7 years (standard deviation [SD] 10.8), who were randomly distributed into an experimental group (EG) (n=27) or a control group (CG) (n=26). No loss to followup was recorded during the study (figure 1). When the subject agreed to participate, physical and clinical baseline data were collected. All individuals also completed the Spanish version of the Northwick Park Neck Pain Questionnaire (NPQ) [21]. The NPQ includes 9 items scored from 0 (no pain or disability) to 4 (the highest pain or disability). Responses are summed and then divided by 36 or 32, if the question related to driving is not answered, to get a percentage score. The outcome measures (pressure pain threshold values) were collected at baseline and immediately after intervention. The inclusion criteria were: a) age between 18-50 years; b) subjects with neck and/or cervicobrachial pain following CW in the 3 months before data collection (no minimum intensity of pain was required); c) a grade II CW according to the Quebec Task Force Classification [22]; and d) a positive response to the cervical rotation lateral flexion test [23]. The established exclusion criteria were: a) history of rheumatic, tumor or degenerative diseases; b) the presence of 2 or more positive neurologic signs consistent with neural pain associated to disc protrusion or herniation at the lower cervical spine (muscle weakness, altered upper extremity deep tendon reflex, and diminished sensation to pinprick in the upper limb); c) previous surgery in the neck or upper limb regions; d) use of analgesic and/or antiinflammatory 7 medication in the 48 hours prior to data collection; e) having undergone manual treatment in the neck or upper limb in the eight weeks before the study; f) neck pain within three months before CW; g) any contraindication to first rib manipulation; and h) an evidence of central nervous system involvement (e.g., presence of pathologic reflexes). All participants gave verbal and written consent to participate and the procedures were conducted according to the World Medical Association Declaration of Helsinki. Ethical clearance was obtained from the Institutional Review Board. 2.3 Randomization A set of randomized numbers generated by an external online website (www.randomizer.org) was used as the random sequence, and was safeguarded by an assistant not involved in the study. Numbered balls concealing the treatment allocation were prepared inside an opaque bag, and participants were asked to pick a ball. 2.4 Sample Size The software ENE 2.0 (GlaxoSmithKline, London, UK and Universidad Autónoma de Barcelona, Spain) was used to estimate the sample size. Based on previous research [24], the following parameters were taking into account: a) a two-tailed test; b) an α level of 0.05; c) a statistical power of 80%; d) a mean score difference after intervention in the outcome measure (pressure pain threshold) of 0.5 kg/cm2; and e) a SD of 0.5 kg/cm2 at postintervention data. For an allocation 8 ratio of 1:1 between groups, at least 26 participants per group were necessary to complete the trial. 2.5 Outcome measures The pressure pain threshold (PPT), defined as the minimal amount of pressure necessary to evoke pain or discomfort [25], was evaluated in several neural and muscular sites. Pain thresholds have been widely used when assessing subjects with WAD in order to detect signs of local and central hyperexcitability [10]. A digital algometer (FDX 25, Warner Instruments, Greenwich, CT, USA), with a 1cm2 contact area, was used with an increasing pressure of 1kg/cm²/s. The mean of three not consecutive measurements, with a 30-second resting interval, was chosen as the reference value. Pressure algometry is a valid and reliable tool to assess pain processing [26], and has shown a high inter-examiner reliability [27]. The assessment locations were: a) the three emerging branches of the trigeminal nerve: supraorbital, infraorbital, and mental nerves [28]; b) the median nerve, at the elbow site, medial to the tendon of the biceps brachii, and the ulnar nerve, located between the medial epicondyle and the olecranon [9]; and d) the area described to locate tense bands over the upper trapezius, biceps brachii (over the midpoint of the muscle length), triceps brachii (located deep in the long head of the muscle, in the medial side of the muscle belly), and masseter (close to the mandibular angle) muscles [29]. 2.6 Interventions 9 The intervention technique was carried out in both groups by the same physiotherapist, with over 10 years of clinical experience. Subjects in the EG underwent a first-rib thrust technique at the side where the cervical rotation lateral flexion test was positive, or at the most painful side in case the test was positive in both sides. The technique was performed as follows [30] (figure 2). The subject was in seated position while the therapist stood behind. One of the therapist’s hands contacted the rib’s body with the metacarpophalangeal joint of the index finger, while the thumb lied over the supraspinatus fossa, and the rest of the fingers were over the clavicle. The other therapist´s hand was holding the patient’s head, and exerted ipsilateral cervical side bending towards the first rib, and contralateral head rotation. Then, an inferomedial pressure was applied to the first rib until the end-feel, and this was followed by the thrust manipulation. In the CG, a sham-placebo technique was used. Participants were placed in the same position and following the same parameters than in the EG, but no softtissue tension or articular thrust were performed. The placebo intervention was also carried out at the side where the cervical rotation lateral flexion test was positive, or at the most painful side. 2.7 Statistical Analysis The statistical package PASW Advanced Statistics 18.0 (SPSS Inc., Chicago, IL, USA) was used for processing the data. The statistical analysis considered as significant a p-value < 0.05. Normality of the study variables was evaluated using the Shapiro-Wilk test. Results are expressed as the mean value with the corresponding SD and/or 95% confidence intervals (95% CI), as 16 a systematic review and meta-analysis of randomised controlled trials. PLoS One 2015; 10: e0133415. [17] Fernández de las Peñas C, Fernández-Carnero J, Palomeque del Cerro L, Miangolarra-Page JC. Manipulative treatment vs conventional physiotherapy treatment in whiplash injury. A randomized controlled trial. J Whiplash Relat Disord 2004; 3: 73-90. [18] Fernández de las Peñas C, Fernández-Carnero J, Plaza-Fernández A. 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PLoS One 2015; 10: e0132191. 20 21 Table 1 Baseline clinical and physical characteristics of the study sample Values are the mean (standard deviation) unless for days since whiplash injury, where data are reported in percentiles 25, 50 and 75. * P value, statistical significance of the between-group differences Table 2 Baseline, final scores, and within-groups differences of the outcome measures Total Sample (N=53) Experimental Group (n=27) Control Group (n=26) P Value * Age (years) 34.70 (10.8) 32.11 (9.1) 37.38 (11.9) 0.07 Sex (n,%) Female Male 30 (56.6) 23 (43.4) 16 (59.3) 11 (40.7) 14 (53.8) 12 (46.2) 0.33 Weight (kg) 73.13 (15.9) 69.37 (14.2) 77.04 (17.0) 0.08 Height (m) 1.67 (0.08) 1.66 (0.07) 1.67 (0.09) 0.67 Body Mass Index (kg/cm2) 26.54 (5.1) 27.25 (4.9) 25.56 (5.2) 0.19 Days since whiplash injury (P25, P50, P75) (13.5, 20, 30) (11, 17, 33) (15, 20, 25.75) 0.43 Northwick Park Neck Pain Questionnaire 17.17 (6.7) 15.63 (7.4) 18.77 (5.5) 0.08 Painful side (n,%) Right Left 27 (50.9) 26 (49.1) 15 (55.6) 12 (44.4) 12 (46.2) 14 (53.8) 0.89 22 Baseline Post Intervention Score changes (pre – postintervent) P value PPT supraorbital Control group Experimental group 1.33 (0.3) 1.39 (0.4) 1.30 (0.3) 1.41 (0.4) 0.02 [-0.05 / 0.10] -0.01 [-0.11 / 0.08] 0.50 0.71 PPT infraorbital Control group Experimental group 1.69 (0.4) 1.79 (0.4) 1.66 (0.4) 1.86 (0.5) 0.03 [-0.06 / 0.12] -0.07 [-0.22 / 0.08] 0.50 0.35 PPT mental nerve Control group Experimental group 1.53 (0.4) 1.57 (0.4) 1.53 (0.3) 1.74 (0.6) -0.00 [-0.08 / 0.07] -0.16 [-0.33 / 0.01] 0.93 0.05 PPT median nerve Control group Experimental group 2.70 (0.7) 2.75 (0.8) 2.51 (0.7) 2.75 (0.8) 0.18 [-0.00 / 0.37] -0.00 [-0.26 / 0.25] 0.05 0.96 PPT ulnar nerve Control group Experimental group 3.12 (1.0) 3.30 (1.0) 2.97 (0.9) 3.03 (1.0) 0.14 [-0.06 / 0.36] 0.26 [-0.11 / 0.64] 0.17 0.16 PPT upper trapezius Control group Experimental group 1.78 (0.5) 1.83 (0.6) 1.74 (0.5) 1.94 (0.6) 0.04 [-0.09 / 0.77] -0.11 [-0.24 / 0.01] 0.54 0.08 23 Data are reported as mean (standard deviation), or mean [95% Confidence Interval] Abbreviations: PPT, pressure pain threshold (kg/cm2); P, statistical significance of the within-groups comparison. PPT masseter Control group Experimental group 1.78 (0.4) 1.84 (0.4) 1.84 (0.4) 1.80 (0.5) -0.06 [-0.17 / 0.05] 0.03 [-0.12 / 0.19] 0.29 0.64 PPT biceps brachii Control group Experimental group 1.95 (0.5) 1.91 (0.5) 1.93 (0.5) 1.93 (0.5) 0.02 [-0.14 / 0.18] -0.01 [-0.17 / 0.14] 0.79 0.86 PPT triceps brachii Control group Experimental group 2.86 (0.8) 3.10 (1.1) 2.85 (0.9) 3.00 (1.0) 0.01 [-0.19 / 0.21] 0.09 [-0.17 / 0.37] 0.93 0.46 24 Table 3 Analysis of the between-groups differences in the outcome measures Data are reported as mean [95% Confidence Interval] Abbreviations: PPT, pressure pain threshold (kg/cm2) Outcome Measure Mean between-groups score changes P value PPT supraorbital nerve 0.04 [0.16 / -0.08] 0.49 PPT infraorbital nerve 0.10 [0.27 / -0.07] 0.25 PPT mental nerve 0.16 [0.35 / -0.02] 0.08 PPT median nerve 0.18 [0.50 / -0.12] 0.22 PPT ulnar nerve -0.11 [0.31 / -0.54] 0.59 PPT upper trapezius 0.15 [0.34 / -0.02] 0.09 PPT masseter -0.09 [0.09 / -0.28] 0.32 PPT biceps brachii 0.03 [0.26 / -0.19] 0.75 PPT triceps brachii -0.09 [0.24 / -0.42] 0.58 25 Figure 1. Flow diagram of the sample