Research Review By Dr. Michael Haneline©


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Date Posted:

May 2023

Study Title:

Identifying patient characteristics associated with the occurrence of post treatment non-serious adverse events after cervical spine manual therapy treatment in patients with neck pain


Peters R, Schmitt M, Mutsaers B, et al.

Author's Affiliations:

SOMT, University of Physiotherapy, Amersfoort, The Netherlands; Erasmus Medical Centre, Department of General Practice, Rotterdam, The Netherlands; Rotterdam Hogeschool, University of Applied Science, Rotterdam, The Netherlands; BISI, VUB, University of Brussels, Belgium; University of Technology Sydney, Discipline of Physiotherapy, Australia; Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, The Netherlands; Center for Muscle and Joint Health, University of Southern Denmark Odense, Denmark

Publication Information:

Archives of Physical Medicine and Rehabilitation 2023 Feb; 104(2): 277-286. doi: 10.1016/j.apmr.2022.08.007.

Background Information:

Cervical spine manipulation and mobilization are commonly used for the treatment of patients with neck pain, with 6% to 12% of neck pain patients utilizing cervical spine manipulation annually. Manual therapy (MT), comprising high velocity thrust (HVT) manipulation and/or low velocity non-thrust mobilization combined with exercise, has been shown to be beneficial to neck pain patients (1).

Adverse events (AEs) have been reported following cervical manipulation and mobilization, which have been categorized as serious and non-serious. Serious AEs (ex. cervical artery dissection and stroke) can result in life-threatening situations or even death, whereas non-serious AEs are benign and short lived, usually resolving within 24 hours (2). Serious AEs following cervical spinal manipulation are rare, with incidence rates ranging from 1 in 100,000 to 1 in several million (3).

A typical MT visit rarely consists of high-velocity thrust (HVT) manipulation exclusively, rather, a combination of interventions is often utilized, making it difficult to determine which intervention caused a given AE. Therefore, the primary aim of this study was to investigate the occurrence of serious and non-serious AEs after MT treatment in patients with neck pain. A secondary aim was to explore risk factors for non-serious AEs after HVT manipulation and non-thrust mobilization in patients with neck pain.

Pertinent Results:

263 out of 287 eligible manual therapists participated in the study and each MT contributed 5 patients on average. 1195 out of 3813 eligible patients were included in the study, with most exclusions being due to the manual therapists (MTs) already providing the maximum of 5 patients, or patients who did not want to participate. Out of 1195 included patients, complete cases, consisting of both patient and manual therapist data, were provided on 686 patients (57.4%), and were included in the analysis.

Participating patients were allocated into the following 4 groups: 1) HVT manipulation (MP); 2) non-thrust mobilization (MOB); 3) a combination of HVT manipulation and non-thrust mobilization (MP+MOB); and 4) other modalities (other). A total of 3171 treatments were provided and each treatment session with its AEs were analyzed separately.

Non-serious AEs were reported as follows:
  • High-velocity manipulation (MP) group (1014 sessions): stiffness (after 58.7% of sessions), headache (52.0%), radiation (50.3%), aggravation of complaints (48.2%), and fatigue (45.2%). Uncommon AEs after manipulation included cramps (6.8%), disorientation/confusion (5.3%), and vomiting (0.3%).
  • MOB group (829 sessions): stiffness (after 64.7% of sessions), radiation (64.0%), aggravation of complaints (57.0%), fatigue (55.6%), and headache (54.6%). Uncommon AEs after mobilization included blurred vision (12.4%), disorientation/confusion (7.5%), and vomiting (2.2%).
  • MP+MOB group (437 sessions): stiffness (after 62.0% of sessions), radiation (56.1%), headache (49.0%), aggravation of complaints (48.3%), and fatigue (44.6%). Blurred vision (8.9%), disorientation/confusion (6.4%), and vomiting (0.7%) were uncommon after MP+MOB.
  • Other modalities group (891 sessions): stiffness (after 57.1% of sessions), radiation (55.8%), headache (54.0%), aggravation of complaints (50.4%), and fatigue (49.4%). Blurred vision (9.4%), disorientation/confusion (7.4%), and vomiting (0.6%), were uncommon after treatment with other modalities.
No serious AEs were reported by patients in any group.

When the occurrence of AEs was calculated between all groups, there was a statistically significant difference showing the highest rate of AEs in the mobilization group.

Risk factors (predictors) for developing commonly reported non-serious AEs were as follows:
  • Headache: was predicted by age, pain intensity, smoking, and disability. Smoking was the strongest predictor of headache after manipulation.
  • Stiffness: predicted by smoking and pain intensity, with smoking being the strongest predictor.
  • Radiation: predicted by biological sex, smoking, and disability, with smoking being the strongest predictor after manipulation.
  • Fatigue: again, smoking was the strongest predictor after manipulation.
Predictors for uncommon AEs after manual therapy included: cramps after manipulation were predicted by smoking, while nausea after manipulation was predicted by the presence of comorbidity and by biological sex (men had 51% lower odds of AEs versus women).

Predictors of AEs after MOB were as follows: Stiffness was predicted by pain intensity and the presence of comorbidity. Men had 78% lower odds of stiffness after MOB than women. A strong predictor of aggravation of complaints was comorbidity, which also predicted radiation and nausea. Interestingly, smoking was inversely associated with vertigo after MOB.

AEs after MP+MOB included radiation and fatigue, both predicted by smoking. Men had lower odds of reporting fatigue, nausea and stiffness after MP+MOB, whereas both men and women were equally likely to report tinnitus.

AEs after treatment with “other modalities” included headache, radiation, fatigue and stiffness, with smoking as the strongest risk factor. Nausea was predicted by comorbidity after treatment with “other modalities”, whereas comorbidity was inversely associated with vertigo and weakness of the limbs. There was also an inverse relationship between smoking and vertigo after “other modalities”.

Clinical Application & Conclusions:

The rate of non-serious AEs after HVT manipulation versus non-thrust mobilization yielded a statistical difference, with AEs more likely to occur after mobilization. In addition, when comparing the occurrence of AEs after manipulation with the occurrence of AEs after treatment with “other modalities”, there was no difference.

Factors that had the strongest associations with the occurrence of AEs after MT were smoking, with odds ratios ranging from 2.10 to 3.33, and comorbidity, odds ratios ranging from 2.32 to 3.88.

These findings should be helpful to clinicians when selecting manual therapy treatment modalities, realizing that patients may be more likely to experience non-serious AEs following mobilization as compared to manipulation. Clinicians should also be extra vigilant regarding possible AEs following MT treatment in patients with comorbidities and those who smoke. This could form an important part of your patient communication strategy with these patients when discussing what they might expect during their care.

Study Methods:

This was an inception cohort study involving Dutch manual therapists from multiple practices who followed patients for a 12-month period. Dutch manual therapists must have a Master’s degree in manual therapy that requires 3 to 4 years of study. They were also required to attend a 2-day course on the study protocol prior to participating.

To be eligible for participation in this study, patients had to have nonspecific neck pain (pain in the area between the occiput and the spine of scapulae), be between 18 and 80 years of age, and able to read and write Dutch. Patients were excluded if they had specific causes of neck pain, such as vascular or neurologic disorders, neoplasms and rheumatic conditions.

Each of the manual therapists included 5 consecutive non-specific neck pain patients within a 3-month inclusion period. They were instructed to provide their usual type of MT care. Only treatment provided between C0 and C6 was considered for the analysis, whereas treatment at C7 and below was excluded. Treatment modalities were grouped as follows:
  1. HVT manipulation,
  2. non-thrust mobilization,
  3. a combination of HVT manipulation and non-thrust mobilization, and
  4. other modalities.
Patients were asked to complete questionnaires on functioning, disability, and psychological factors at baseline. Disability was measured via the Neck Disability Index (NDI). The anxiety and depression questions of the Neck Bournemouth Questionnaire (NBQ) were used to assess anxiety and depression. The Fear Avoidance Beliefs Questionnaire-Physical Activity subscale (FABQ-PA) was used to assess fear for (re)injury and activity related pain. Other outcome measures included 1-10 numeric rating scales (NRS) for pain, duration of neck pain, and recurrence of neck pain.

Patients completed the Adverse Events Questionnaire within 48 hours after each treatment. This questionnaire queries the patient about any unpleasant reaction after treatment, including the type of reaction, time of onset, duration, and intensity of symptoms. Patients were able to add reactions that were not included in the questionnaire.

Patients completed the NRS, NDI, NBQ, and FABQ again at the end of the treatment series along with the Global Perceived Effect (GPE) questionnaire, which is scored on a 7-point scale that ranges from “total recovery” to “worse than ever”.

Study Strengths / Weaknesses:

This was a well-done prospective cohort study, and all the participating manual therapists were qualified and trained on the procedures that were used. However, patients were not randomized to groups, rather a convenience sample of sequentially presenting patients was used, and the therapist decided which modality to provide.

There were several study limitations, as follows:
  • Only 686 out of 1193 patients (57.5%) returned complete data before deadline.
  • Therapists were aware of the patients’ characteristics before deciding which type of manual therapy to provide which may have affected their clinical decision.
  • AEs were classified based on the intensity and duration of the patients’ AEs, whereas another study classified AEs based on whether the patients’ symptoms were neurologic vs. non-neurologic (4). The specific definition and classification of AEs relating to MT is currently being investigated and further elucidated.
  • It is possible that there was confounding due to the overlap of patient characteristics between the groups which might have led to over-representation.
  • Patients reported AEs only up to 48 hours after treatment; so no information was collected after that point in time to determine how much longer the AE may have lasted.
  • It is possible that some of the reported AEs were not caused by the treatment provided, instead they were caused by other activities or factors not covered in the questionnaire(s).

Additional References:

  1. Bronfort G, Evans R, Anderson A, Svendsen K, Bracha Y, Grimm R. Spinal manipulation, medication, or home exercise with advice for acute and subacute neck pain: randomized trial. Ann Intern Med 2012; 156: 1-10.
  2. Rubinstein S, Leboeuf-Yde C, Knol D, De Koekkoek T, Pfeifle C, Van Tulder M. The benefits outweigh the risks for patients undergoing chiropractic care for neck pain: a prospective, multicenter, cohort study. J Manipul Physiol Ther 2007; 30: 408-18.
  3. Cassidy JD, Boyle E, Cote P, et al. Risk of vertebral stroke and chiropractic care: results of a population-based case control and case cross over study. Spine 2008; 33: S170-5.
  4. Hurwitz E, Morgenstern H, Vassilaki M, et al. Frequency and clinical predictors of adverse reactions to chiropractic care in the UCLA neck pain study. Spine 2005; 30: 1477–84.

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