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The Somatic Connection  |   January 2011
The Somatic Connection
Article Information
The Somatic Connection   |   January 2011
The Somatic Connection
The Journal of the American Osteopathic Association, January 2011, Vol. 111, 7-12. doi:10.7556/jaoa.2011.111.1.7
The Journal of the American Osteopathic Association, January 2011, Vol. 111, 7-12. doi:10.7556/jaoa.2011.111.1.7
Web of Science® Times Cited: 341
This month's installment of “The Somatic Connection” focuses on manipulation of the cervical spine. In the context of concerns over deaths that may have been caused by chiropractic cervical spinal manipulation, it is important to note that there is evidence of benefits from osteopathic manipulative treatment and other types of manual therapy, including chiropractic manipulation, applied to the cervical spine. Results of a Cochrane Systematic Review on the latest evidence-based literature assessments of manipulation of the cervical spine are reviewed by Michael A. Seffinger, DO. Also reviewed by Dr Seffinger are results of a unique clinical trial in which Australian chiropractors, physiotherapists, and an osteopath collaborated to assess the comparative effectiveness of cervical manipulation vs mobilization. A review of a chiropractic study from The Netherlands reveals no serious neurologic events associated with cervical manipulation. In addition to these reviews, Hollis H. King, DO, PhD, has assembled 3 other studies from Europe that are representative of research showing efficacy of cervical-area osteopathic manual therapy. Estimates indicate that risks of cervical high-velocity, low-amplitude (HVLA) manipulation are very low—with serious adverse events such as death being rare and adverse reactions being self-limiting, usually resolving spontaneously within a few days. The American Osteopathic Association House of Delegates' position paper on this matter states that benefits outweigh the risks for osteopathic manipulative treatment, including HVLA, in osteopathic clinical practice and education.  
Cochrane Library Review of Cervical Manipulation
Gross A, Miller J, D'Sylva J, et al. Manipulation or mobilisation for neck pain. Cochrane Database Syst Rev. 2010, Issue 1. Art No: CD004249. doi: 10.1002/14651858.CD004249.pub3  
Questions have been raised in the medical research and clinical literature regarding the efficacy and safety (ie, benefit vs risk) of a type of high-velocity, low-amplitude (HVLA) cervical manipulation performed by chiropractors. The most common cervical spine manipulation performed by chiropractors is HVLA, whereas US-trained osteopathic physicians may use a variety of direct, indirect, or combined methods of osteopathic manipulative treatment (OMT) that may include HVLA. This is not to say that chiropractic HVLA is the same as osteopathic HVLA. To my knowledge, there have been no collaborative clinical trials by the 2 professions, so any comparison of HVLA as used by chiropractors vs HVLA as used by osteopathic physicians lacks evidence. 
In discussions at osteopathic and chiropractic scientific meetings in the United States, there has been some discrepancy regarding at which point in the cervical spine's range of motion the thrust, or force, is provided by the practitioner. For example, discussions at the Focused Research Forum on Cervical Spine Manipulation, which met at the request of the American Osteopathic Association (AOA) House of Delegates in 2006 and 2007, included representatives from the AOA Bureau of Osteopathic Clinical Education and Research, the AOA Bureau of Scientific Affairs, the AOA Council on Research, the American Academy of Osteopathy, the Osteopathic Research Center at the University of North Texas Health Science Center, and a consultant epidemiologist and biostatistician from the chiropractic profession. The debate at these meetings focused on whether the HVLA thrust performed by chiropractors or osteopathic physicians occurred at the restrictive barrier, the physiologic barrier, or the anatomic barrier of the restricted joint's motion. 
Nevertheless, in 2009, the AOA House of Delegates reaffirmed the use of cervical HVLA by osteopathic physicians in a position paper originally approved in 2004. The position paper includes a review of the literature on the safety and efficacy of this procedure. In short, the AOA endorses the use of cervical HVLA by osteopathic physicians, based on the conclusion that the benefits outweigh the risks of this form of OMT. To update readers of “The Somatic Connection” on this issue, I conducted a search for the latest evidence-based literature assessments of manipulation of the cervical spine. 
Every few years, The Cochrane Library publishes an updated systematic review of randomized controlled clinical trials on the efficacy of cervical manipulation and other manual therapies compared to the efficacy of other therapeutic methods for the treatment of patients with neck pain and headaches—the 2 main symptoms for which patients receive cervical spine manipulation. A 2010 Cochrane systematic review by Gross et al assessed 27 randomized, controlled clinical trials (a total of 1522 participants) of the use of manipulation and mobilization of the cervical spine for patients with neck pain. The review found that, among the practitioners assessed, cervical manipulation (ie, HVLA) was most commonly performed by chiropractors, and mobilization (ie, non-HVLA manual therapies) was most commonly performed by physical therapists (ie, physiotherapists) or chiropractors in the studies cited. The 1 study that was performed by US-trained osteopathic physicians (McReynolds et al. J Am Osteopath Assoc. 2005;105[2]:57-68) did not delineate between HVLA and other OMT procedures in reported outcomes. Thus, that osteopathic study did not meet the inclusion criteria for this systematic review. 
The Cochrane systematic review used criteria described in the following excerpt from the article to rate the quality of evidence in the reviewed studies: 

Domains that may decrease the quality of the evidence are: 1) the study design, 2) risk of bias, 3) consistency of results, 4) directness (generalizability), 5) precision (sufficient data), and 6) reporting of the results for studies that measure one particular outcome. Domains that may increase the quality of the evidence are 1) large magnitude of effect, 2) all residual confounding [variables that] would have reduced the observed effect, and 3) a dose-response gradient is evident. High quality evidence was defined as RCTs [randomized, controlled trials] with low risk of bias that provided consistent, direct and precise results for the outcome. The quality of the evidence was reduced by a level for each of the domains not met or increased by factors such as large magnitude of effect; all plausible confounding [variables that] would reduce a demonstrated effect and dose-response gradient.

 
  • High quality evidence: Further research is very unlikely to change our confidence in the estimate of effect. There are consistent findings among 75% of RCTs with low risk of bias that are generalizable to the population in question. There are sufficient data, with narrow confidence intervals. There are no known or suspected reporting biases. (All of the domains are met).
  • Moderate quality evidence: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. (One of the domains is not met).
  • Low quality evidence: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. (Two of the domains are not met).
  • Very low quality evidence: We are very uncertain about the estimate. (Three of the domains are not met.)
  • No evidence: No RCTs were identified that measured the outcome.
Two trials (total of 369 participants) in the Gross et al review specifically compared the use of HVLA to the use of mobilization for treating patients with neck pain (Hurwitz et al. Am J Public Health. 2002;92[10]:1634-1641; Cassidy et al. J Manipulative Physiol Ther. 1992;15[9]:570-575). Results of these trials demonstrated that the efficacy of HVLA is equivalent to that of mobilization procedures for statistically significantly reducing neck pain and improving patient function and satisfaction. The reviewers rated the evidence for this conclusion as being of “moderate quality.” These trials found that patient response to treatment with either HVLA or mobilization was immediate and of short-term duration. The researchers have not yet conducted long-term follow-up studies. 
Some studies in the review evaluated the number of HVLA treatments needed to obtain desired results. Unfortunately, those studies were rated as having low-quality evidence. Nevertheless, 3 of the trials (total of 130 participants) demonstrated that cervical HVLA provides improved short-term pain relief compared to controls (ie, no treatment, muscle relaxant medication, or sham manipulation) after only 1 to 4 sessions. For patients with chronic cervicogenic headaches, 1 trial (with 25 participants), classified as having low-quality evidence, showed that 9 or 12 manipulation sessions were superior to 3 sessions for improvement in pain immediately after treatment. 
Only about one-third of the studies (8 of 27) in the review reported on whether adverse effects from cervical manipulation occurred during the study period. Five of these 8 studies reported that adverse effects occurred, and the other 3 studies reported that no adverse effects occurred. The adverse effects were minor and temporary and included headache, pain, stiffness, minor discomfort, and dizziness. Similar to results in previously published systematic reviews, the Gross et al review found that rare but serious adverse events, such as stoke or severe neurologic deficits, were not reported in any of the trials. 
Some of the trials reviewed by Gross et al had such low-quality evidence that confidence in their results is lacking. Osteopathic physicians need to develop rigorous randomized controlled clinical trials and comparative effectiveness studies that would shed more light on the benefits vs the risks of cervical HVLA.—M.A.S. 
Support for Cervical HVLA and Mobilization for Patients With Acute Neck Pain
Leaver AM, Maher CG, Herbert RD, et al. A randomized controlled trial comparing manipulation with mobilization for recent onset neck pain. Arch Phys Med Rehabil.2010 ;91(9):1313 -1318.  
This study by Andrew M. Leaver, PhD, and colleagues is a unique clinical trial in which Australian chiropractors, physiotherapists, and an osteopath collaborated to assess the comparative effectiveness of cervical manipulation (ie, high-velocity, low-amplitude [HVLA] manipulation) vs mobilization (ie, manual low-velocity, oscillating passive movement applied to the cervical spine) for patients who had less than 3-months duration of neck pain. 
In the trial, 182 patients were recruited by 7 physiotherapists (n=125), 5 chiropractors (n=56), and 1 osteopath (n=1) from 12 primary care clinics in Sydney, Australia, between October 2006 and June 2008. Sixty-four of the patients (35.2%) were men, and the mean (standard deviation [SD]) age of the patients was 38.9 (10.7) years. Of the recruited patients, 179 completed all 4 treatment sessions in the 2-week study protocol. Participants were randomized to receive either HVLA (n=91; 2 withdrew; n=89 in final analysis) or mobilization (n=91; 3 withdrew; n=88 in final analysis). 
The primary outcome measure was median number of days to recovery from neck pain. The mean (SD) initial pain rating on a 0 to 10 scale (with 10 as most severe) was 6 (2). One-hundred fifteen participants (63%) reported a history of neck pain. Most of the patients had pain in other body regions as well as the neck: 79% had upper limb pain, 64% had headache, and 63% had upper back pain. The mean (SD) baseline disability score reported by participants on a 0 to 50 scale (with 50 as most disabled) was 15.5 (7). 
Results of the study showed that mean recovery time from neck pain was 47 days in the manipulation group and 43 days in the mobilization group. Participants who received neck manipulation did not experience more rapid recovery than those who received neck mobilization (hazard ratio=0.98; 95% confidence interval, 0.66-1.46; P=.909). Recovery of normal activity was also statistically similar between groups (hazard ratio=1.02; 95% confidence interval, 0.72-1.47; P=.897). The median time for functional recovery was 22 days for the cervical HVLA cohort vs 24 days for the cervical mobilization cohort. There were no statistically significant differences between the manipulation and mobilization groups in the secondary outcomes of pain, disability, function, global perceived effect, or health-related quality of life at any time point. 
Approximately twice as many participants who received HVLA had a relapse of their neck pain, compared to participants who received mobilization procedures (28.6% vs 14.9%, respectively). As in all previous randomized controlled clinical trials of cervical HVLA, this study found that no serious neurovascular adverse effects were reported by participants during the treatment period; no adverse events were identified during the 3-month follow-up period. Participants reported various self-limiting minor adverse effects, including increased neck pain (reported by 29.4% of participants) and headache (reported by 22% of participants). There were no statistically significant differences in incidence of these minor adverse effects between participants receiving cervical manipulation vs those receiving mobilization. 
The Leaver et al study supports the use of either cervical HVLA or low-velocity, articulatory-type manual therapy to treat patients with recent-onset neck pain.—M.A.S. 
Adverse Events Associated With Chiropractic Cervical Manipulation
Rubinstein SM, Leboeuf-Yde C, Knol DL, de Koekkoek TE, Pfeifle CE, van Tulder MW. Predictors of adverse events following chiropractic care for patients with neck pain. J Manipulative Physiol Ther.. (2008). ;31(2):94 -103.  
Concern has been raised recently about the risk of serious adverse events, including death, resulting from high-velocity manipulation of the cervical spine as performed by chiropractors (Ernst E. Int J Clin Pract. 2010;64[8]:1162-1165). A recent American Osteopathic Association position paper endorses continued use by osteopathic physicians of cervical high-velocity, low-amplitude (HVLA) osteopathic manipulative treatment (OMT)—which is not necessarily the same high-velocity technique as that performed by chiropractors. However, that position paper is based predominantly on clinical trials performed by the chiropractic and physiotherapy professions. Only 1 randomized controlled clinical trial on the use of cervical OMT in the United States has been published (McReynolds and Sheridan. J Am Osteopath Assoc. 2005;105[2]:57-68). Researchers in that trial measured only short-term pain relief response in an emergency department setting, and they reported no adverse events from cervical OMT. 
In this prospective, multicenter chiropractic study conducted in The Netherlands by Sidney M. Rubinstein, DC, MSc, and colleagues, an 11-point numerical rating scale documented the adverse events associated with cervical HVLA and other manual techniques at the second visit (within 1 week of baseline) and fourth visit (within 6 weeks of baseline) of patients to chiropractors: (1) pain or stiffness at the treated area, (2) pain or stiffness in another treatment-related area, (3) headache, (4) tiredness or sleeplessness, (5) radiating pain to an upper extremity, (6) dizziness or light-headedness, (7) nausea, (8) ringing in the ears, (9) confusion or disorientation, (10) depression or fear, and (11) any other symptom not defined by any of the previous categories. An adverse event was defined as either a new, related complaint that was not present at baseline or the worsening of an existing complaint by more than 30% compared to baseline. 
Seventy-nine chiropractors (65% men; 96% full-time practitioners; mean [SD] experience, 10.2 [6.3] years [range, 1-28 y]) recruited and treated 529 patients (69% women; mean [SD] age, 41.2 [11.5] years [range, 18-65 y]) who had constant or intermittent neck pain or neck-related pain of any duration. Included patients had not undergone manual therapy during the previous 3 months. Sixty-seven percent of patients had visited a general practitioner physician during the previous 6 months, but only 6% of patients were using prescription analgesics at the time of the study. The most common symptoms associated with neck pain were fatigue, headache, and dizziness. 
The predominant manipulation procedure used by chiropractors in the study was cervical HVLA, which was referred to by the authors as “diversified” technique. According to the study, 95% of participating chiropractors “regularly used” diversified technique in their practices, and diversified technique was the most commonly used treatment delivered to the neck at first visits in the study (78% of first-visit treatments). Study results showed that rotational cervical HVLA was used in 57% of first-visit treatments. 
Altogether, 60 prognostic variables were examined in this study, including descriptors of the patient, chiropractor, and type of treatment delivered. Logistic regression analyses with multivariate random coefficients were conducted to determine predictors for adverse events. Fifty-six percent of the study population reported an adverse event, mostly related to pain in the musculoskeletal system. Increased neck pain after the first visit was the easiest outcome variable to predict (area under the curve [AUC], 0.88; 95% confidence interval, 0.84-0.91), using the following explanatory variables: duration with neck pain, pattern of pain in the preceding year, headache, and neck disability at baseline. (An AUC of 0.5 indicates no discriminative ability of the model beyond chance; an AUC of 1.0 indicates 100% discriminative ability.) 
The study identified 4 variables as predictors of adverse events related to cervical spine manipulation. Three of these variables predicted increased likelihood of having an adverse event: HVLA using cervical rotation, the working status of the patient (ie, being on sick leave or workers' compensation), and longer duration of neck pain in the preceding year (ie, if neck pain persisted for more than 60 days, the association was strong [odds ratioadj, 3.2] for new or increased headache). 
Patients in the Rubinstein et al study who saw a general practitioner for neck pain or stiffness within 6 months before chiropractic treatment were less likely to have an adverse event than other patients in the study. No serious neurologic events, such as stroke or death, were reported as a result of cervical manipulation in this chiropractic study.—M.A.S. 
Osteopathic Manual Therapy Improves Cervical Range of Motion and Reduces Pain in Patients With Temporomandibular Disorders
Cuccia AM, Caradonna C, Annunziata V, Caradonna D. Osteopathic manual therapy versus conventional conservative therapy in the treatment of temporomandibular disorders: a randomized controlled trial [published online ahead of print September 20, 2009]. J Bodyw Mov Ther.2010 ;14(2):179 -184.  
Italian researchers led by A.M. Cuccia compared osteopathic manual therapy with conventional conservative therapy (CCT) in the treatment of patients with temporomandibular disorders (TMDs). Patients with TMD were recruited from the Department of Orthodontics and Gnathology at the University of Palermo in Italy. Fifty consecutive patients aged 18 to 50 years were randomly assigned to either the osteopathic manual therapy group (12 men, 13 women) or the CCT group (10 men, 15 women). There were no statistically significant age differences between the groups. Patients were included in the study if they had a temporomandibular index (TMI) reference value in the severe range and a minimum pain intensity of 40 mm on a visual analog scale (VAS). 
Outcome measures were pain intensity rating on the VAS, TMI value, maximal mouth opening, and cervical range of motion as measured by a standard instrument. Osteopathic manual therapy was administered by a “doctor of osteopathy” (V. Annunziata, University of Palermo), who used “gentle techniques such as myofascial release, balanced membranous tension, muscle energy, joint articulation, high-velocity, low-amplitude thrust, and cranial-sacral therapy” according to standard osteopathic manual therapy and osteopathic manipulative treatment texts. The CCT was provided by a gnathology practitioner and included application of oral appliances, physical therapy, hot and cold packs, and transcutaneous electrical nerve stimulation. All patients were attended by their clinic medical practitioners and prescribed nonsteroidal medications (ie, anti-inflammatories and analgesics), muscle-relaxant medications, or a combination of medications as needed. 
Patients visited their practitioners for osteopathic manual therapy or CCT every 2 weeks for 6 months, and outcome measures were recorded on initial visit, at 24 weeks (ie, end of therapy), and at a 32-week follow-up. Outcome measure assessments were made by a researcher who was blinded to the intervention group. 
Symptoms of patients in both groups improved over the course of the study, and there were no statistically significant differences in outcome measures between the osteopathic manual therapy and CCT groups. Similar to results of the Andersson et al study comparing osteopathic spinal manipulation with standard care for patients with low back pain (N Engl J Med. 1999;341[19]:1426-1431), the Cuccia et al study found that patients in the osteopathic manual therapy group required statistically significant less medication (both nonsteroidal medications and muscle relaxants) than did patients in the conventional care group (P<.001). 
The authors concluded that osteopathic manual therapy is a viable treatment for patients with TMD and is certainly comparable in outcomes—though not superior—to CCT. However, the authors did not discuss the possible confounding factor that patients in the CCT group received some manual contact in the form of physical therapy, which—in this reviewer's experience—is a major factor in TMD treatment outcomes. Thus, it is possible that if there had been no physical therapy in the CCT group, the outcome measures would have favored the osteopathic manual therapy group. 
The Cuccia et al study was selected for the present review because of the large amount of cervical osteopathic manual therapy and physical therapy muscle stretching applied to the study participants. The study found no adverse events when cervical high-velocity, low-amplitude thrust was applied to patients, and results revealed improvement in maximal mouth opening and cervical range of motion in virtually all patients.—H.H.K. 
Efficacy of Cervical Manipulation and Mobilization Is Demonstrated
Oliveira-Campelo NM, Rubens-Rebelatto J, Martín-Vallejo FJ, Alburquerque-Sendín F, Fernández-de-las-Peñas C. The immediate effects of atlanto-occipital joint manipulation and suboccipital muscle inhibition technique on active mouth opening and pressure pain sensitivity over latent myofascial trigger points in the masticatory muscles. J Orthop Sports Phys Ther.2010 ;40(5):310 -317.  
Spanish and Portuguese researchers led by César Fernández-de-las-Peñas, PT, PhD, examined the effects of cervical manipulation and mobilization on facial muscle pressure pain threshold (PPT) over latent trigger points (TrPs) and on active mouth opening distance. In the study, conducted at the Escuela de Osteopatia de Madrid, Escola Superior de Tecnología de Saúde in Portugal, 122 volunteers with latent TrPs in the masseter muscle were randomly assigned to 1 of 3 groups. Individuals in the manipulation group received manipulation consisting of a thrust to the atlanto-occipital joint. Individuals in the mobilization group received soft-tissue inhibition mobilization to suboccipital muscles. Individuals in the control group received no intervention. Thirty-one men and 91 women with an age range of 18 to 30 years participated in the study. 
Two outcome measures were used in the study. One measure was assessment of PPT using a mechanical pressure algometer that was covered with a round rubber disk (1 cm2 in area) on the portion pressed against the skin. The TrP of the PPT was the point at which the participant reported the experience of pressure becoming pain. A latent TrP is a point that when firmly palpated produces a pain pattern not previously experienced by the individual—that is, a new unfamiliar nociceptive experience. By contrast, an active TrP is a point that when firmly palpated produces a familiar nociceptive experience. The second outcome measure was the distance of active mouth opening. 
The same researcher (Natalia M. Oliveira-Campelo, PT, DO) administered both interventions—manipulation to the atlanto-occipital joint and inhibition mobilization to the suboccipital muscles. Assessment of the latent TrPs over both the masseter and temporalis muscles and measurement of the active mouth opening distance was performed by a researcher who was blinded to the intervention group. 
Results of the study showed statistically significant increases in the amount of pressure needed to elicit pain over the masseter latent TrPs (P<.01) and temporalis latent TrPs (P=.003), as well as a statistically significant increased active mouth opening distance (P<.001), immediately after atlantooccipital joint thrust manipulation. Soft-tissue suboccipital muscle inhibition mobilization increased the PPT over the temporalis latent TrPs but not over the masseter latent TrPs. Active mouth opening distance was not changed with the soft-tissue suboccipital technique. The authors pointed out that their measured effect sizes were small, and that further study is needed to fully elucidate the clinical significance of their findings. 
This study was selected for review in this edition of “The Somatic Connection” for 2 reasons. First, it is among a growing number of studies suggestive of the efficacy of cervical manipulation and, as such, presents a counterpoint to the negative findings of the recent Ernst article (Ernst. Int J Clin Pract. 2010;64[8]:1162-1165). Second, it relates to a technical, nomenclature-related issue. In previous editions of “The Somatic Connection” (J Am Osteopath Assoc. 2009;109[4]:214-215 and 2010;110[5]:271-276), differences in nomenclature between that used in the Glossary of Osteopathic Terminology and that used in standard manual medicine/manual therapy (MM/MT) terminology have been pointed out. For example, from the perspective of osteopathic medicine, all manually guided forces are termed manipulation. Outside the osteopathic medical profession, however, manipulation means high-velocity, low-amplitude thrust, and mobilization means application of manually guided forces without a thrust. 
Most MM/MT researchers are aware of these nomenclature differences. Yet, in the communication of MM/MT research to the medical and research community at large, care is not always taken to operationally define all procedures used. 
The Oliveira-Campelo et al study illustrates this problem. In the study, as previously indicated, the researchers referred to one of the procedures as “suboccipital muscle inhibition.” From the illustrations and descriptions provided in the article, this technique appears to be identical to the “atlanto-occipital decompression” procedure described in Outline of Osteopathic Manipulative Procedures: The Kimberly Manual (Kimberly PE. Marceline, MO: Walsworth Publishing Co; 2008:69). The term inhibition may be misleading because of the implied inhibition or reduction in sympathetic nervous system activity, which may or may not have occurred in the Oliveira-Campelo et al study. The typical interpretation of this procedure in osteopathic medicine is that there is a separating, or decompression, of the base of the occiput away from the first cervical vertebral segment (in the order of microns). This decompression may also affect vagus nerve function and have much broader impact on the autonomic nervous system than implied by the word inhibition. 
Although this distinction in terminology may seem relatively minor, the need for broad definitional clarification is emerging in importance as evidence accumulates that neuromusculoskeletal changes result from manipulation and mobilization of the suboccipital area.—H.H.K. 
Cervical Manipulation Affects Perception of Pain
Mansilla-Ferragut P, Fernández-de-las-Peñas C, Albuquerque-Sendin F, Cleland JA, Boscá-Gandía JJ. Immediate effects of atlanto-occipital joint manipulation on active mouth opening and pressure pain sensitivity in women with mechanical neck pain. J Manipulative Physiol Ther.2009 ;32(2):101 -106.  
Osteopathic practitioners in Spain, including lead author Pilar Mansilla-Ferragut, DO, conducted research examining the effects of atlanto-occipital joint manipulation on pain perception in women with mechanical neck pain. Supervised by the Escuela de Osteopatia de Madrid, Alcalá de Henares, 37 women aged 21 to 50 years (mean [SD] age, 35 [8] y) with mechanical neck pain were recruited into the study. Mechanical neck pain was described as general shoulder or neck symptoms caused by sustained neck postures, certain neck motions, or cervical muscle palpation. To be included in the study, patients needed to have bilateral symptoms of at least 6-months duration and an active mouth opening of less than 40 mm. 
The pressure pain threshold (PPT) of each patient was determined by the “minimal amount of pressure needed for a pressure sensation to first change to pain” and was measured by a mechanical pressure algometer. The standard site of the PPT measurement was over the greater wing of the sphenoid bone bilaterally. 
Eighteen women were randomly assigned to the experimental group, and 19 women were randomly assigned to the control group. Patients in the experimental group received atlanto-occipital joint manipulation consisting of a gentle rotary high-velocity, low-amplitude thrust at the joint, with the patient's head rotated to one side and cephalic traction applied. Patients in the control group received 30 seconds of manual contact positioned similarly to the thrust manipulation. The thrust and manual contact procedures were repeated on both sides of all patients. 
The same osteopathic practitioner (“a manual/physical therapist with a 6-year postgraduate training in spinal manipulative therapy” from the Escuela de Osteopatia de Madrid) conducted all interventions in the experimental and control groups. A researcher who was blinded to the intervention group performed the PPT and active mouth opening measurements. Each patient received 2 measurements—1 preintervention and 1 5-minutes postintervention. 
Results of the study showed a statistically significant increase in active mouth opening of 3.5 mm (P<.001) for the experimental group and no statistically significant change in active mouth opening for the control group. The experimental group also showed a greater improvement in PPT levels than did the control group. Calculations using Cohen d coefficient revealed a large positive within-group effect size (d>1.5) in active mouth opening for the experimental group and a negative medium within-group effect size (d=-0.5) in active mouth opening for the control group. Calculations also showed a medium positive within-group effect size (d=0.5) in PPT for the experimental group and a negative medium within-group effect size (d= -0.5) in PPT for the control group. 
The authors speculated regarding the mechanism of action for the observed effects. Possible mechanisms of action noted by the authors were changes in positional afferent signals from the atlanto-occipital joint and neurophysiologic changes related to upper cervical reflex-mediated inhibition of muscle contraction. Limitations of the study were the short-term nature of the observed effects and the fact that all study participants were women. 
The study by Mansilla-Ferragut et al was reviewed in this edition of “The Somatic Connection” because the included patients had neck pain, and results of cervical manipulation showed measurable effects in this patient population. However, the authors made no attempt to relate the obtained effects to any measurable or actual neck pain experienced by the patients.—H.H.K. 
 “The Somatic Connection” highlights and summarizes important contributions to the growing body of literature on the musculoskeletal system's role in health and disease. This section of JAOA—The Journal of the American Osteopathic Association strives to chronicle the significant increase in published research on manipulative methods and treatments in the United States and the renewed interest in manual medicine internationally, especially in Europe.
 
 To submit scientific reports for possible inclusion in “The Somatic Connection,” readers are encouraged to contact JAOA Editorial Advisory Board Member Michael A. Seffinger, DO (mseffinger@westernu.edu), or Editorial Board Member Hollis H. King, DO, PhD (hking@atsu.edu).
 
 Drs Seffinger and King were not involved in the decision to publish these contributions.