Effect of cervical vs. thoracic spinal manipulation on peripheral neural features and grip strength in subjects with chronic mechanical neck pain: a randomized controlled trial

Title: Effect of cervical vs. thoracic spinal manipulation on peripheral neural features and grip strength in subjects with chronic mechanical neck pain: a randomized controlled trial Authors and affiliations: Francisco BAUTISTA-AGUIRRE1, 2, Ángel OLIVA-PASCUAL-VACA3 *, Alberto M. HEREDIA-RI ZO3, Juan J. BOSCÁ-GANDÍA2, François RICARD2, Cleofás RODRI GUEZ-BLANCO 3 1 Department of Physical Therapy, European University, Valencia, Spain; 2 Madrid Osteopathic School, Madrid, Spain; 3 Department of Physiotherapy, Faculty of Nursing, Physiotherapy and Podology, University of Sevilla, Sevilla, Spain. * Corresponding author: Ángel Oliva-Pascual-Vaca, Department of Physiotherapy, Faculty of Nursing, Physiotherapy and Podology, University of Sevilla, Calle Avicena s/n, 41009, Sevilla, Spain. E-mail: [email protected] Abstract BACKGROUND: Cervical and thoracic spinal manipulative therapy has shown positive impact for relief of pain and improve function in non-specific mechanical neck pain. Several attempts have been made to compare their effectiveness although previous studies lacked a control group, assessed acute neck pain or combined thrust and nonthrust techniques. AIM: To compare the immediate effects of cervical and thoracic spinal thrust manipulations on mechanosensitivity of upper limb nerve trunks and grip strength in patients with chronic non-specific mechanical neck pain. DESIGN: Randomized, single-blinded, controlled clinical trial. SETTING: Private physiotherapy clinical consultancy. POPULATION: Eighty-eight subjects (32.09±6.05 years; 72.7% females) suffering neck pain (grades I or II) of at least 12 weeks of duration. METHODS: Participants were distributed into three groups: 1) cervical group (N.=28); 2) thoracic group (N.=30); and 3) control group (N.=30). One treatment session consisting of applying a high-velocity low-amplitude spinal thrust technique over the lower cervical spine (C7) or the upper thoracic spine (T3) was performed, while the control group received a sham-manual contact. Measurements were taken at baseline and after intervention of the pressure pain threshold over the median, ulnar and radial nerves. Secondary measures included assessing free-pain grip strength with a hydraulic dynamometer. RESULTS: No statistically significant differences were observed when comparing between-groups in any of the outcome measures (P>0.05). Those who received thrust techniques, regardless of the manipulated area, reported an immediate increase in mechanosensitivity over the radial (both sides) and left ulnar nerve trunks (P<0.05), and grip strength (P<0.001). For those in the control group, right hand grip strength and pain perception over the radial nerve also improved (P≤0.025). CONCLUSIONS: Low-cervical and upper-thoracic thrust manipulation is no more effective than placebo to induce immediate changes on mechanosensitivity of upper limb nerve trunks and grip strength in patients with chronic non-specific mechanical neck pain. CLINICAL REHABILITATION IMPACT: A single treatment session using cervical or thoracic thrust techniques is not enough to achieve clinically relevant changes on neural mechanosensitivity and grip strength in chronic non-specific mechanical neck pain. Key words: Brachial plexus - Hand strength - Neck pain - Pain threshold - Musculoskeletal manipulations. Introduction Neck pain is a common disorder which it is estimated to affect around 50-67% of the population at some point of their lives, with the subsequent associated costs.1 Widespread sensory hypersensitivity is a common feature in patients with whiplashassociated disorders,2 and can also be present in non-traumatic and idiopathic chronic neck pain,3, 4 suggesting some inconclusive evidence of central sensitization (an increased sensitivity of the nervous system).4 Lowered pressure pain thresholds, compared to healthy controls, have been observed in patients with chronic non-specific neck pain locally at the cervical spine,5 and at peripheral nerve trunks (median,5, 6 radial and cubital nerves).6 Even though no active treatment seems to be distinctly superior to any other for neck pain,7, 8 spinal manipulation may show a more favorable effect on increasing pressure pain thresholds than other forms of manual therapy and sham interventions, with this effect being consistent also beyond the local region of manipulation.9 Upper limb neurodynamic tests are used to detect increased mechanosensitivity of the brachial plexus nerve trunks and report a satisfactory level of reliability.10 Spinal manipulative therapy is widely used, along with exercise, mobilization and softtissue techniques, in patients reporting musculoskeletal symptoms of the spine.11 It has shown a potential clinical efficacy on muscle inhibition,12 neuromuscular excitability,13 and functional performance.14 The use of cervical 15, 16 or thoracic 7, 17, 18 spinal thrust techniques has reported positive results on pain relief, cervical mobility, and selfreported function in non-specific mechanical neck pain. However, recent systematic reviews conclude that there is still insufficient and discrepant evidence to support the use of thoracic or cervical manipulation or mobilization versus control intervention for patients with neck pain.7, 19 Within manual therapies, the presence of adverse events, although benign and transient, appears to be more common in subjects who undergo manipulation.20 These perceived risks are usually associated with cervical thrust techniques.21 Therefore, some attempts have been made to compare the effectiveness of cervical and thoracic thrust manipulation on pain perception, disability level,18, 22 pressure pain sensitivity, and mobility,23 in neck pain. However, these previous studies lacked a control group,18, 22, 23 assessed acute neck pain,18 or combined thrust and nonthrust techniques,22 thus no definitive conclusions can be drawn in this issue.7 New research is needed to associate peripheral effects with a possible centrally-mediated response to manipulative techniques.24 This study assessed and compared the effectiveness of a spinal thrust manipulation directed to the cervical or the thoracic spine in patients with chronic non-specific mechanical neck pain. To assess treatment efficacy, we primarily evaluated changes on upper limb neural mechanosensitivity and, as secondary goals, we aimed to compare changes on grip strength. Measurements were taken at baseline and immediately after intervention. We hypothesized that spinal manipulation would have a more positive impact on mechanosensitivity and grip strength than a control intervention, but no differences were expected between the manipulative groups. Materials and methods The sample consisted of 88 subjects (32.09±6.05 years; 72.7% females) recruited from a private clinical consultancy in L’Horta Sud region, Valencia, Spain. Participants were enrolled if they were aged between 20 and 65 years, diagnosed with neck pain grades Ior II, with or without pain radiating to the head, trunk and/or limbs, lasting for at least 12 weeks according to the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders,25 (no signs or symptoms suggesting major structural pathology, with lack of or minor interference with daily life in grade I, and major interference with activities of daily living in grade II). Additional inclusion criteria were a negative response to the Spurling test,26 and a positive response to the upper limb neurodynamic test of the median nerve in at least one upper extremity (both upper limbs were tested).27 Patients were excluded if they had mechanical neck pain secondary to whiplash, torticollis, rheumatoid arthritis, advanced cervical osteoarthritis and/or myelopathy, a previous history of ischemic episodes, severe trauma or surgery in the upper extremity and/or cervical spine, a clinical diagnosis of carpal tunnel syndrome, hormonal imbalance, diabetes, or cervicobrachial pain associated with herniation or disc protrusion at lower cervical spine (T1-weighted sagittal and axial MRI images, as assessed by an independent physician). Those who received manual treatment in the eight weeks before data collection, were currently using drugs or medication, or reported any contraindication to spinal manipulation, were also excluded. Ninety-nine subjects were initially selected and 11 were finally excluded. No loss to follow-up was recorded during the data collection or analysis phases (Figure 1). The study was conducted from late April to mid July 2015 in a specialized private clinical center in Valencia. Study design A randomized, controlled, single-blinded clinical trial was carried out. After the initial clinical interview conducted by a specialist manual therapist, an external assistant randomly allocated participants into three groups: 1) control group; 2) cervical group; and 3) thoracic group. Randomization was based on a single sequence of random assignments (simple randomization) using the Epidat software v. 3.1 (Consellería de Sanidade, Xunta de Galicia, Spain and Panamerican Health Organization), and was safeguarded by the assistant. Sealed opaque envelopes concealing the group allocation were used to distribute patients into the study groups. This external assistant was blinded to the study objectives and the examiner who collected data remained unaware of study factors and treatment allocation group. The required sample size was estimated using the ENE software v. 2.0 (GlaxoSmithKline, UK and Universidad Autónoma de Barcelona, Spain). Following previous research in this field,23 a mean difference of 0.5 kg/cm2 in mechanosensitivity values after intervention, with a standard deviation (SD ) of 0.5 kg/cm2 at postintervention data, was expected. We accepted a level of 0.05, a two-tailed test, and an 80% desired power. For an equal allocation between groups, at least 26 participants per group were necessary. We predicted a 5% lost to follow-up. All participants were assessed under the same conditions at baseline and immediately after intervention by the same examiner, who had over 10 years of clinical experience. The exposure times were also similar to all groups. The whole protocol was performed in a single session and lasted around 40-45 minutes. The present trial was approved by the Institutional Review Board (Research Ethics Committee of the University of Sevilla, Spain). Before data collection, all subjects agreed to participate by signing an informed consent form. The study procedures were conducted according to the Declaration of Helsinki, and the trial was registered in the Australian New Zealand Clinical Trial Registry (registration no. ACTR N 12615000412538). Interventions As in previous studies,28 the possibility of compromised vertebral artery was tested before intervention to minimize risks, and stringent eligibility criteria were used to ensure a very low risk of possible adverse events. Each patient received a single session of similar duration where participants remained on a treatment table and received the intervention according to the allocated group. The same therapist, with over 9 years of clinical experience in spinal thrust manipulation, was in charge of intervention in all groups. Cervical spinal thrust Subjects in this group underwent the thumb-move manoeuver at the low-cervical spine (C7).29 With the patient in seated position, the thrust was delivered either to the right or left side, based on subject’s pain perception and detection of joint hypomobility.23 Thoracic spinal thrust The subject was lying supine with arms crossed over the chest and hands placed over the opposite shoulder. The high-velocity low-amplitude thrust technique was performed as in previous studies,23 with T3 being the targeted vertebrae. Control group Participants in this group were lying supine and received a sham-manual contact in the scalp for three minutes. Therapist’s hands were placed over the lateral sides of the cranium, with a “five-finger hold” and with no movement or therapeutic intention. Assessment A baseline assessment about clinical and demographic features was conducted. After that, pain perception and grip strength were evaluated before and immediately after intervention. Mechanosensitivity was assessed with a digital dynamometer (model FM200, PC E Instruments UK Ltd., Southampton, UK). An increasing pressure of 1 kg/cm²/s was used, with a 30-second resting period between measurements, and taking the mean of three measurements as the reference score. With the subject lying supine, pressure pain threshold was evaluated over the upper limb nerve trunks in the following order: 1) median nerve, at the carpal tunnel site,30 and at the ulnar fossa;2 2) ulnar nerve;2, 30 and 3) radial nerve.2, 30 Pressure algometry has shown a high inter-examiner reliability.31 The pain-free grip strength was assessed with an isometric, hydraulic hand dynamometer (model 5030J1, JAMAR ®, Sammons Preston, Bolingbrook, IL , USA). 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ES: effect size. *Statistically significant difference in intra-group comparison (P<0.05).