Abstract
Context: Low back pain (LBP) affects up to 85% of all persons at some time in life and is a condition for which osteopathic manipulative treatment (OMT) has been shown to be beneficial. Measures that can improve the efficacy of OMT would further benefit patients; one such measure, hydration status, was explored in this study.
Objective: To determine whether there is a relationship between a patient's hydration status before OMT for LBP and the outcome of that treatment.
Design: A randomized, single-blind crossover study conducted from March to December 2010.
Setting: Outpatient academic center.
Participants: Eight women and 11 men with LBP of 1 to 12 months duration.
Interventions: Both euhydrated and hypohydrated conditions were achieved in each participant by modifying water consumption for 36 hours before OMT sessions. Participants received 2 sessions of OMT, each in a different hydration condition and with a 1-week washout period in between.
Main Outcome Measures: Pre- and posttreatment visual analog scale scores for pain, number and severity of somatic dysfunction as scored on the somatic dysfunction severity scale, and number of asymmetric landmarks found on the osteopathic standing structural examination.
Results: Improvements in total and severe number of lumbar somatic dysfunction (P=.001 and P=.013, respectively) and number of asymmetric landmarks on standing structural examination (P=.002) were found to be greater in the euhydrated vs the hypohydrated condition. Participants had a mean of 2 fewer areas of posttreatment somatic dysfunction when euhydrated than when hypohydrated, and they had a mean decrease of 2 asymmetric landmarks on the standing structural examination when euhydrated but none when hypohydrated. Osteopathic manipulative treatment improved self-reported pain immediately after treatment regardless of hydration status.
Conclusion: Outcome measures improved for all participants, with greater improvement observed after participants were treated in the euhydrated condition than when in the hypohydrated condition. It is reasonable for clinicians to recommend that patients increase their hydration to optimize treatment.
As early as the 1870s, Andrew Taylor Still, MD, DO, theorized that osteopathic manipulative treatment (OMT) improves blood flow and thus health by allowing the body full opportunity to heal itself.
1,2 More recently, spinal manipulation has become accepted as a clinically helpful treatment for patients with low back pain (LBP).
3-5 Given that OMT is an effective treatment for patients with back pain and that its effects are elicited through the body's implicit ability to perfuse tissue, the question arises as to whether the body's hydration status affects the efficacy of OMT.
Before discussing the effects of hydration status on human physiology, several terms require defining.
Hypohydration is defined as reduced total body water.
Euhydration, or normal body water content, is not a specific point but rather is best represented by a sinusoidal wave that oscillates around an average.
6 Previous research
7 indicates that this average euhydration value can be determined by taking the mean of 3 consecutive daily body mass (BM) measurements. Subsequent BM measurements can be compared with this baseline value; a morning body weight within 1% of the baseline indicates euhydration and anything lower indicates hypohydration.
6-9 Urine specific gravity (USG), the density of a urine sample relative to that of water, as measured with a refractometer, is another validated method of measuring hydration status.
10-14
Previous studies
9-14 have used measures of BM and USG to help quantify the ways in which all physiologic systems in the human body are influenced by hypohydration. The degree of hypohydration dictates the extent of systemic compromise. Hypohydration of up to 5% body weight has been achieved in humans by a variety of methods and with no long-term adverse effects.
15-19 Mild to moderate hypohydration of between 2.5% and 3% can be achieved by water restriction alone.
20-22 Changes at the level of the muscle tissue have been identified in exercise studies at these levels of hypohydration; they include increased lactate level,
9 increased rate of glycogen degradation,
23,24 elevated muscle temperature,
25 and measurable adverse influences on strength, work capacity, performance, and time to exhaustion.
9 These findings may be caused by a decrease in blood perfusion of the muscle tissue during the recovery between contractions, secondary to the contracted hypohydrated state of the body.
9 Although, to our knowledge, no studies have been published exploring whether such findings are seen after OMT or whether these changes affect treatment outcome, similarities between the effects of exercise and OMT are obvious, particularly for modalities such as muscle energy. Even so, a clinical study that investigates whether and how hydration affects the outcome of OMT is needed.
As LBP is highly prevalent and has been shown to improve with osteopathic care,
3-5 it is a useful condition for investigating the relationship between the efficacy of OMT and hydration status. The cost of back pain in America is in excess of $85.9 billion annually, higher than that of arthritis ($80.3 billion) and just below that of cancer ($89.0 billion); this value represents only health care expenditures and does not include lost earnings or productivity.
26 Sixty to seventy percent of all persons are affected by LBP at some time in life,
27 with 85% of LBP cases considered nonspecific or biomechanical.
28 Low back pain is the second most common reason for visiting a primary care physician.
29,30 For a condition with such a considerable national and individual toll, any variable that improves the efficacy of OMT could have a considerable effect. The current experimental, randomized, single-blind crossover trial was designed to determine whether hydration status would affect the efficacy of OMT. We hypothesized that treatment outcomes would be more favorable when patients were in a euhydrated rather than a hypohydrated condition.
The present investigation was a randomized, single-blind crossover study. After obtaining approval from the Midwestern University Institutional Review Board, we recruited 19 study participants with LBP of 1 to 12 months duration from the faculty, students, and staff of Midwestern University in Downers Grove, Illinois.
Participants were included in the study if they had a documented somatic dysfunction of the lumbar spine with or without sacral and pelvic dysfunction and a subjective complaint of LBP of 1 to 12 months duration. Previous studies
5,30-33 have demonstrated that the majority of primary care patients with LBP show substantial improvement within the first month independent of intervention, making it difficult to demonstrate the value of OMT or any other intervention in patients with acute symptoms. For this reason, 1 month was used as the lower limit. The upper limit of 12 months was selected so that inclusion criteria would not be too narrow and study results would be applicable to more patients with LBP, including those with subacute LBP (6-12 weeks duration) and those in the first months of chronic LBP.
Exclusion criteria included previously diagnosed musculoskeletal diseases, nerve root compression or any other findings of frank neurologic signs during physical examination, history of spinal injuries or operations, malignant tumor, scoliosis, a systemic inflammatory disorder, uncontrolled diabetes, urinary tract infection at baseline, and pregnancy.
Figure 1 illustrates the flow of participants in the study. At the baseline visit, written informed consent was obtained and participants were randomly assigned to 1 of 2 treatment sequences, according to the crossover study protocol (
Figure 2). The assignments were generated by a computer and dispersed at the baseline visit.
Data were collected on paper forms, which were then transferred to Microsoft Excel spreadsheets (Microsoft Corporation, Redmond, Washington) for data management and then statistical software for analysis. The SPSS statistical software (version 17.0; SPSS Inc, Chicago, Illinois) was used for all analyses. Descriptive statistics were compiled for participants' sex, age, and duration of LBP in months; χ2 and t tests were used to examine these differences, as well as the hydration status, between the 2 treatment sequences. Nonparametric analysis was used to analyze measures owing to the distribution of the data and underlying constructs. The Wilcoxon signed rank test for related samples was used to compare outcome measures before and after treatments in both the euhydrated condition and the hypohydrated condition. The Wilcoxon signed rank test was used to determine differences in the magnitude of change in somatic dysfunction severity scores, number of asymmetric landmarks, and VAS score between the 2 hydration conditions.
Regarding hydration status, although all participants achieved adequate euhydration or hypohydration levels according to either BM (threshold, 1% BM loss) or USG (threshold, 1.0200) criteria, only 7 participants met both criteria for both hydration conditions. Although this finding suggests that some participants were not as euhydrated or hypohydrated as desired, it allows the findings to be generalized to a clinical population, where patients alter their hydration status under real-world conditions, not in a laboratory. While a more tightly controlled hydration state—produced, for example, by having participants run in a heated room to dehydrate them to the same point immediately before treatment—would yield a more narrow range of hypohydration, it would also have less clinical applicability. Osteopathic physicians treat patients in a variety of hydration conditions and the present data suggest that patients in a slightly more hydrated state respond to treatment better than those who are less hydrated.
Although participants in both euhydrated and hypohydrated conditions showed an improvement in the total and severe number of somatic dysfunctions, the extent of improvement in the euhydrated condition was greater than that in the hypohydrated condition, and this difference was statistically significant. Osteopathic manipulative treatment resulted in a mean improvement of 3 total areas scored on the somatic dysfunction severity scale when participants were euhydrated vs 1 when they were hypohydrated.
The distinction between total and severe scores on the somatic dysfunction severity scale was meant to address the fact that patients could have clinically different presentations that might not be represented by total scores alone. For example, a patient who has 5 areas of somatic dysfunction, each scored as a 1 (mild) in severity, is clinically different to an osteopathic physician than a patient with 2 areas of somatic dysfunction scored as 2 and 3 (more severe), even though both patients have the same total score. Considering the improvement in higher-scoring areas of somatic dysfunction as a separate outcome measure helped elucidate the effects of treatment in clinically different patients with the same total scores. Thus, the data suggest that OMT in the euhydrated condition reduced scores to a statistically significant degree for both the total number of dysfunctions and the “key” lesions, as represented by the se vere somatic dysfunction severity scores of 2 and 3.
Osteopathic physicians are trained to assess the symmetry of landmarks as a sign of potential disease and to use their resolution or lack of resolution as indicators of treatment success. Although asymmetries may be structural and not functional, the mean improvement of 2.4 fewer asymmetric landmarks for participants in the euhydrated condition indicates that OMT had a positive effect on those asymmetries that were functional. There was no mean difference in the number of asymmetric landmarks after OMT in the hypohydrated condition.
Osteopathic manipulative treatment is effective at lowering self-reported pain immediately after treatment, regardless of hydration status, possibly indicating that the improvement is so noticeable to patients that their state of hypohydration does not negate the perceived difference after treatment. The differences in self-reported pain 3 days after treatment were not statistically significant between hydration conditions despite the fact that there was, in fact, a statistically significant change after the euhydrated treatment. This finding may be a result of the small sample, the mild nature of the patients' LBP (mean VAS score at baseline, 35 mm), or the relatively small changes in hydration status (10 of the 19 participants were <1% dehydrated according to BM measures). While the data demonstrate a statistically significant improvement in VAS 3 days after euhydrated treatments, it is possible that these factors prevented this finding from achieving a statistically significant difference from the VAS 3 days after hypohydrated treatments.
The main areas of methodologic weakness in the present study were the size of the study group, subjective and temporal nature of the outcome measures, and lack of a placebo control. This study relied on subjective outcome measures, as reported by both the study physicians and the participants themselves. Although these measures were selected because of the confounding nature of objectively measuring OMT outcomes, and although few previous studies have successfully used objective measures, the subjective measures still pose a weakness. The study participants provided information about pain immediately and 3 days after treatment, but they were not followed up long enough to provide information about functional changes. The short period of euhydration or hypohydration and the lack of extended follow-up for structural and somatic changes are limitations of this study because trends over time or with repeated sessions could not be addressed. Regarding a control group, the potential for LBP improvement with minimal or no treatment in each hydration status was not addressed, and therefore the effects of hydration status alone on LBP cannot be differentiated from those of hydration status coupled with OMT.