Objective
To study osteopathic manipulative treatment of back pain and related symptoms during the third trimester of pregnancy.
Study Design
A randomized, placebo-controlled trial was conducted to compare usual obstetric care and osteopathic manipulative treatment, usual obstetric care and sham ultrasound treatment, and usual obstetric care only. Outcomes included average pain levels and the Roland-Morris Disability Questionnaire to assess back-specific functioning.
Results
Intention-to-treat analyses included 144 subjects. The Roland-Morris Disability Questionnaire scores worsened during pregnancy; however, back-specific functioning deteriorated significantly less in the usual obstetric care and osteopathic manipulative treatment group (effect size, 0.72; 95% confidence interval, 0.31–1.14; P = .001 vs usual obstetric care only; and effect size, 0.35; 95% confidence interval, –0.06 to 0.76; P = .09 vs usual obstetric care and sham ultrasound treatment). During pregnancy, back pain decreased in the usual obstetric care and osteopathic manipulative treatment group, remained unchanged in the usual obstetric care and sham ultrasound treatment group, and increased in the usual obstetric care only group, although no between-group difference achieved statistical significance.
Conclusion
Osteopathic manipulative treatment slows or halts the deterioration of back-specific functioning during the third trimester of pregnancy.
Previous studies have found that a majority of pregnant women report low back pain during pregnancy. Other common neuromusculoskeletal problems during pregnancy include pubic pain, hip pain, knee pain, leg cramps, carpal tunnel syndrome, and DeQuervain’s tenosynovitis. When considering such neuromusculoskeletal aspects of pregnancy, virtually all women experience symptoms during pregnancy, with an estimated one quarter having at least temporary disability. Moreover, pregnancy-related back pain is often associated with sleep disturbance and may affect activities of daily living or quality of life.
Complementary and alternative medicine (CAM) therapies may be considered as treatment options for back-related symptoms during pregnancy because of the real or unknown risks inherent with many drug therapies. A majority of pregnant women and prenatal health care providers alike report that they would consider using CAM therapies for low back pain during pregnancy, particularly manipulative and body-based practices such as massage and spinal manipulation. Osteopathic manipulative treatment (OMT) is a form of manual therapy provided by osteopathic physicians. An intriguing aspect of OMT is that during pregnancy, unlike massage therapy or chiropractic, it potentially could be integrated with the routine prenatal visits provided by osteopathic obstetricians. However, relatively little research has been conducted on OMT during pregnancy. An observational study using medical records review at 4 sites found that prenatal OMT was associated with lowered risk of preterm delivery and meconium staining of amniotic fluid. Nevertheless, corroborating evidence of OMT benefits during pregnancy from prospective studies or clinical trials is lacking. The primary purpose of this randomized controlled trial was to explore the potential effects of OMT provided exclusively during the third trimester of pregnancy on maternal back pain and related physical functioning.
Materials and Methods
This Phase II randomized controlled trial was conducted by The Osteopathic Research Center at the University of North Texas Health Science Center. Recruitment was open from July 2003 through December 2005 within the Department of Obstetrics and Gynecology at the University of North Texas Health Science Center. All study procedures were approved by the Institutional Review Board for Protection of Human Subjects. The study was also registered with ClinicalTrials.gov ( ClinicalTrials.gov , NCT00298935 ).
Obstetric clinic patients were screened up to the 30th week of pregnancy for eligibility and willingness to participate in the study. Exclusion criteria included either of the following: (1) intent to deliver at a nondesignated hospital or (2) high-risk pregnancy as determined by the attending obstetrician. The latter criterion included, but was not limited to gestational diabetes, preeclampsia, placenta previa, and abruptio placentae. Clinic patients who met the eligibility criteria and provided informed consent were enrolled as subjects between the 28th and 30th weeks of pregnancy and were then randomly assigned as trial subjects.
Each subject was randomly assigned to 1 of 3 treatment groups: (1) usual obstetric care and OMT (UOBC+OMT); (2) usual obstetric care and sham ultrasound treatment (UOBC+SUT); or (3) usual obstetric care only (UOBC only). In this trial, “usual obstetric care” refers to conventional prenatal care during pregnancy exclusive of OMT, which is generally considered a CAM therapy. Subjects were stratified by age and gravida number on the theoretical basis that these factors may influence response to OMT. Twenty-four years was estimated to be the median age of clinic patients seeking obstetric care based on previous records, and we arbitrarily stratified subjects as primigravida or multigravida. Hence, the 4 age- and gravid-specific strata were as follows: (1) age ≤24 years and primigravida; (2) age ≤24 years and multigravida; (3) age ≥25 years and primigravida; and (4) age ≥25 years and multigravida. Blocked treatment assignments were then made within each of the 4 age- and gravid-specific strata. Blocks of 6 subjects were used to randomly assign 2 subjects to each of the 3 treatment groups within each age- and gravid-specific stratum. Assuming continued eligibility and pregnancy, the UOBC+OMT and UOBC+SUT groups were scheduled to receive treatments at the 30th week (visit 1), 32nd week (visit 2), 34th week (visit 3), 36th week (visit 4), 37th week (visit 5), 38th week (visit 6), and 39th week (visit 7). Each treatment visit was scheduled to last 30 minutes.
The OMT protocol consisted of a standardized approach whereby each assigned subject received treatment provided by licensed physician faculty within the Department of Osteopathic Manipulative Medicine at the University of North Texas Health Science Center. The study protocol included any of the following treatment modalities: soft tissue, myofascial release, muscle energy, and range-of-motion mobilization. These modalities were used in a systematic manner within a protocol that enabled the physician to identify and treat specific somatic dysfunctions in the following anatomic regions: cervical, thoracic, and lumbar spine; thoracic outlet and clavicles; ribcage and diaphragm; and pelvis and sacrum. Treatment providers met regularly to ensure consistency in the duration, type, anatomic location, and manner of manipulation provided throughout the trial. The study protocol prohibited use of high-velocity, low-amplitude techniques because the increasing ligamentous laxity that occurs in late pregnancy may pose a theoretical risk in performing such maneuvers. A cranial technique known as compression of the fourth ventricle (CV-4) was also prohibited on theoretical grounds that it may potentially induce premature labor, although the small uncontrolled study suggesting that CV-4 may initiate uterine contractions involved only postdate women.
The SUT protocol was adapted from that described in a previous randomized controlled trial of manual therapy. The SUT treatments were provided by the same physicians who provided OMT. In addition to controlling for physician attention during the treatment visit, the SUT used a nonfunctional ultrasound therapy unit that was modified for research purposes to provide both visible and auditory cues that could potentially elicit a placebo response. The physician provided the SUT by placing the applicator head over the subject’s clothing and applying sufficient pressure for tactile stimulation of the skin and underlying tissues in the same anatomic distributions as would generally be addressed if the subject were being treated with OMT.
The subjects assigned to the UOBC-only group did not receive any study treatments beyond conventional obstetric care; however, they were expected to complete data collection forms on the same schedule as all other trial subjects. As with the UOBC+OMT and UOBC+SUT subjects, the UOBC-only subjects were allowed to receive conventional obstetric care, but not OMT, massage therapy, physical therapy, chiropractic manipulation, or therapeutic ultrasound intended to treat musculoskeletal disorders.
Data for subjects in each of the 3 treatment groups were collected by blinded clinical research personnel at the time of randomization and during third trimester visits 1-7. At each treatment visit, the blinded attending obstetrician confirmed the subject’s continuing eligibility during the prenatal visit immediately before the provision of the study treatment (ie, OMT or SUT in the applicable treatment groups). The 2 outcome domains included: (1) back pain, as measured by an 11-point scale (0, 1, 2, … , 10) for the average level of back pain; and (2) back-specific functioning, as measured by the Roland-Morris Disability Questionnaire (RMDQ). The back pain scale included interval ratings from 0 (“no pain”) to 10 (“worst possible pain”) with no temporal frame of reference. Responses to this item were analyzed as if obtained from a 10-cm visual analog scale for pain. The RMDQ was scored as the total number of affirmative responses to each of its 24 back-related items based on the day of data collection. A higher score was indicative of poorer back-specific functioning and a greater level of disability.
All analyses were based on the intention-to-treat principle. Thus, once a particular treatment was started, each subject was included in that treatment group regardless of her adherence to the 7-visit treatment protocol during the third trimester. Subjects may have missed their assigned treatments for various reasons, including withdrawing from the study without cause, being lost to follow-up, being withdrawn by their attending obstetrician for development of a high-risk condition, or other miscellaneous reasons. In addition, subjects may have “missed” scheduled treatment visits because of delivery before visit 7 at the 39th week. Missing data were imputed using the last observation carried forward method. If a subject delivered before visit 7, to maximize statistical power, the carry-forward method was used to impute missing data for censored observations during the remaining obstetric visits that were obviated by the delivery. Because back pain was likely to increase and back-specific functioning to deteriorate as pregnancy progressed, this approach to imputation may have biased the results in favor of treatment groups with more missed visits. We analyzed the differences in frequency of missed visits among treatment groups to determine whether supplemental analyses were needed to further address this potential source of bias.
The baseline characteristics of subjects were summarized using descriptive statistics. Differences among the 3 treatment groups were assessed using the χ 2 test for categorical variables and analysis of variance for continuous variables. Life-table methods were used to assess subject flow through the trial, including the cumulative distributions of treatment-eligible subjects, treatment-withdrawn subjects because of development of high-risk status, and treatment-censored subjects because of delivery before visit 7. Treatment outcomes were assessed with repeated measures analyses of covariance (ANCOVA) using the baseline measures as covariates. The ANCOVA considered both treatment group and time (as proxied by visit number) main effects and the treatment group × time interaction. Additional analyses were performed to measure effect sizes for treatment outcomes. The latter were computed such that positive effect sizes reflected treatment outcomes in the desired directions (ie, lower pain levels and lower RMDQ scores). Effect size thresholds for minimally important benefits and harms attributable to OMT were used to supplement the conventional statistical interpretation of the results of this exploratory trial. Minimally important benefits were defined by effect sizes ≥0.2 based on a commonly accepted standard for small effects. Minimally important harms were more conservatively defined by effect sizes ≤−0.1. All hypotheses were assessed at the α = .05 level of statistical significance using 2-tailed tests. The treatment group sample sizes were estimated to achieve a statistical power of 70% in conventional independent group comparisons based on a hypothesized moderate and clinically relevant effect size of 0.5 for back pain (ability to detect differences of 1.25 cm among treatment groups on a 10-cm visual analog scale for back pain) and back-specific functioning (ability to detect differences of 3 units among treatment groups on the 24-unit RMDQ). Data management was performed with the SPSS version 14.0 software package (SPSS, Inc, Chicago, IL).
Results
As shown in Figure 1 , 863 obstetric clinic patients were screened for eligibility and willingness to participate in the study. A total of 177 eligible patients agreed to participate; however, 31 patients did not progress to random assignment, most often because of the development of a high-risk condition (n = 18) or voluntary withdrawal from the trial (n = 10). A total of 49, 48, and 49 subjects were randomly assigned to the UOBC+OMT, UOBC+SUT, and UOBC-only groups, respectively.
The baseline characteristics of these subjects according to treatment group are presented in the Table . Subjects were similar across treatment groups with regard to most characteristics. There was a significant difference among treatment groups with regard to illicit drug use ( P < .001). The UOBC+OMT group included substantially more former drug users and fewer never users than the other treatment groups. Also, there was a marginally significant difference among treatment groups with regard to vaginal bleeding ( P = .05). In subtable analyses, this was attributed to the greater percentage of subjects who reported vaginal bleeding in the UOBC+SUT group compared with those in the UOBC-only group ( P = .04). There were no significant baseline differences in any of the outcome measures among treatment groups.
