Topical Menthol Gel versus a Placebo Gel on Post-manipulation Pain and Range of Motion in Patients with Mechanical Neck Pain
Robert Topp, Kara Solem, Jena Etnoyer-Slaski, and Barton Bishop
Journal of Performance Health Research Volume 1, Issue 2. Pages 40–47DOI: 10.25036/jphr.2017.1.2.topp.2 © 2017 Performance Health www.performancehealthresearch.com
The purpose of this study is to determine whether patients with mechanical neck pain who received topical menthol gel application to their neck before cervical manipulation experienced a reduction in pain and an increase in neck range of motion following cervical manipulation.
Patients (mean age, 35 years) with non-radicular mechanical neck pain were randomly assigned to a control (n = 31) or a treatment (n = 29) group. Five minutes before cervical manipulation, controls received topical placebo gel application to their neck, whereas the treatment received topical application of a menthol-containing gel (Biofreeze®). Participants rated their neck pain on a 10-point scale before application of the get (Pre) and at 1 min (T1), 10 min (T2), 20 min (T3), and 30 min (T4) after cervical manipulation. Six measures of neck range of motion were assessed before the topical applications of gel and at T1 and T4. Repeated-measures ANCOVA was performed to compare the pain and neck range of motion following manipulation while controlling for premeasures.
There were no significant differences between the groups’ pain or range of motion assessed at Pre. The treatment group reported significantly (P<.05) reduced pain at T2, T3, T4 compared to T1, while the control group did not experience significant change in their pain compared to T1. Neither study group rated a change in neck range of motion during the study.
Topical menthol application before manipulation may reduce neck pain, but it has no measurable effect on neck range of motion following cervical manipulation among patients with mechanical neck pain.
Neck pain is the fourth leading cause of disability, with an annual prevalence rate exceeding 30%. Most episodes of acute neck pain will resolve with or without treatment, but 50% of individuals will continue to experience some degree of pain or frequent occurrences.1,2 Almost 50% of the individuals who complain of neck pain experience incomplete resolution of their symptoms.3 Neck pain is also the second most common complaint patients present with in chiropractic treatment facilities.4
Mechanical neck pain has been defined as “non-specific (pain) in the area of the cervico-thoracic junction that is exacerbated by neck movements.” This definition does not include the cause of mechanical neck pain because there are a variety of combinations of underlying biomechanical and physiologic disorders, trauma, and psychological factors that result in mechanical neck pain.
To evaluate and treat mechanical neck pain, health practitioners take a detailed history, perform a physical examination, and when medically necessary visualize the structures of the area through X-rays, computed tomography scans, and magnetic resonance imaging scans. The development of mechanical neck pain is commonly accompanied by reduced neck range of motion with or without a clear initiating event or structural deformity.6
Conservative treatment of this condition involves interventions to reduce pain and improve intersegmental mobility while the provider provides treatment or information to guide the patient on how to increase neck range of motion, muscular coordination, endurance, and strength.7 One effective treatment option to treat patients with mechanical neck pain is cervical manipulation.8 However, cervical manipulation has been reported to result in adverse effects in 30%–61% of all patients, including increased neck pain, stiffness, headache (or head pain), and radiating pain.9 A majority of these adverse effects begin on the day of therapy, last less than 24 hours, and are reported to range from mild to moderate by patients.10 Investigators have also reported that cervical manipulation can result in acute muscle soreness that may last up to 6 hours post manipulation.11
Current evidence suggests that although there are mild-to-moderate increases in neck pain immediately after neck manipulation, the long-term benefits of neck manipulation include increased neck range of motion and decreased pain levels among patients with neck pain.12 The immediate post-manipulation neck pain experienced by some patients is offset by the long-term benefits of neck manipulation.13 While pain immediately following cervical manipulation does not typically last more than 24 hours, this temporary increase in pain may deter patients from maintaining compliance with other prescribed therapies.14 For example, increased pain following cervical manipulation may contribute to a lack of compliance with prescribed rehabilitation therapies, which is essential for managing pain symptoms.15 Topical application of menthol has long been considered to be an effective treatment for mild-to-moderate pain.16 Investigators have confirmed the pain-relieving effects of topical application of menthol on a variety of conditions, including neuropathic pain,17 knee osteoarthrosis,18 and carpal tunnel syndrome.19 A more recent study indicated that topical application of menthol was effective in reducing pain among patients with non-radicular, acute neck pain.11 Topically applied menthol relieves mild-to-moderate pain and no previous clinical trials have reported any adverse events resulting from the use of the topical menthol. This evidence appears to indicate that topical application of menthol may be effective in mitigating pain immediately post cervical manipulation and is accompanied by a low risk of adverse effects. The purpose of this study is to determine whether patients with mechanical neck pain who received topical menthol gel application to their neck before cervical manipulation experienced a reduction in pain and an increase in neck range of motion following cervical manipulation. This purpose was addressed by testing two hypotheses: H1: Patients with mechanical neck pain who receive a topical menthol gel application to their neck before cervical manipulation will report a significant reduction in pain post manipulation compared with those who receive a placebo gel application before cervical manipulation. H2 Patients with mechanical neck pain who receive topical menthol gel application to their neck before cervical manipulation will experience significantly increased neck range of motion post manipulation compared with those who receive a placebo gel application before cervical manipulation.
Table 1 presents comparisons of background characteristics, pain ratings, and the six measures of neck range of motion before the application of any intervention at Pre. This table indicates that there were no statistically significant differences (P <.05) between the two study groups on any of the background characteristics or measures of pain or neck range of motion. The sample included individuals of 35 years of age, suffering for >100 days with neck pain, completed close to 9 previous clinic visits for their neck pain, and reported a moderate amount of neck pain before the application of any interventions. Of particular note is the observation that a majority of the participants did not consume any pain medication within the previous 24 h. At Pre, the participants in both the treatment and control groups reported a moderate degree of neck pain at 5.10 and 4.29 out of 10, respectively. This non-significant 20% difference in neck pain between the study groups assessed at the Pre-data collection point supported the decision to use the ANCOVA statistic, which controlled for this difference in the analysis to address the hypothesis based on the participant’s Pre measures. The analysis to address H1 indicated a significant time effect (P<.05), although the non-significant group and interaction effects showed that the groups were not different at any data collection point over the duration of the study. Post hoc comparisons based on the time effect did reveal that the treatment group reported a significant decrease in pain at T2, T3, andT4 compared with their measures at T1, while the control group did not report a significant change in their pain levels over the duration of the study (Table 2). Table 2 also presents the comparisons within and between groups on the six measures of neck range of motion. This table indicates that the study groups exhibited similar levels of neck range of motion overall data collection points. Further, neither of the study groups showed a significant change in their neck range of motion at 1 (T1) or at 30 (T4) min following cervical manipulation. These measures of the sample’s neck range of motion were less than the anatomical norms cited previously.
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