Research Review By Dr. Jeff Muir©


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Date Posted:

March 2019

Study Title:

Intervertebral Kinematics of the Cervical Spine Before, During and After High Velocity Low Amplitude Manipulation


Anderst WJ, Gale T, LeVasseur C, Raj S, Gongaware K & Schneider M

Author's Affiliations:

Orthopaedic Research Laboratories, Pittsburgh, USA; Departments of Orthopedic Surgery and Physical Therapy, University of Pittsburgh, USA.

Publication Information:

The Spine Journal 2018; 18(12): 2333-2342. doi: 10.1016/j.spinee.2018.07.026.

Background Information:

Neck pain remains one of the most common and disabling musculoskeletal complaints globally, with a lifetime prevalence of up to 70% (1). Neck pain is often treated using high-velocity low-amplitude (HVLA) cervical spine manipulation (2, 3), which has proven to be an effective treatment modality (4, 5), although the optimal dosage of manipulation as an intervention remains unknown.

The biological mechanisms of spinal manipulation are also currently unknown. Several theories suggesting biomechanical, psychological and/or neurophysiological mechanisms have been suggested, although the inability to accurately measure the intervertebral kinematics of the spine during manipulation acts as a barrier to fully understanding and optimizing treatments.

The objectives of this study were therefore to characterize the intervertebral kinematics (i.e. facet joint gapping) and manual forces at play in the cervical spine during spinal manipulation. The hypothesis was that patient-reported pain would decrease and the intervertebral range of motion (ROM) would increase following manipulation.

Pertinent Results:

20 patients were recruited for the study. After screening, 2 declined participation, 1 did not attend for testing, 1 was excluded due to lack of previous manipulation and 1 was excluded due to breastfeeding. 15 patients were then initially enrolled in the study, although 3 were excluded as portions of their upper cervical spine were occluded by the hands of the treating chiropractor (during imaging). 4 males and 8 females (average age was 40.1 ± 15.0 years) were eventually included. An audible cavitation was recorded in 11 of 12 patients.

Interestingly, facet gapping occurred on the contralateral side of the target. Maximal increase in facet gap from pre-manipulation to peak gap was 0.9 ± 0.4 mm (pre-gap mean: 0.8 ± 0.5 mm – meaning the ‘gap’ essentially doubled with SMT). The average increase in facet gap over all tracked motion was 0.7 ± 0.4 mm (pre-gap mean: 0.9 ± 0.5 mm). The mean rate of facet gapping was 6.2 ± 3.9 mm/s (mean time: 136 ± 54 ms).

Force-time characteristics were recorded in 5 patients. Average preload was 9.4 ± 3.1 N, with mean peak force recorded at 65.6 ± 3.9 N. Force was applied over 130 ± 10 ms at 440.4 ± 57.6 N/s.

Flexion/extension ROM increased at C4/5, C5/6 and C6/7, with mean increases of 1.2 ± 1.3° (p = 0.006), 2.1 ± 2.4° (p = 0.01) and 3.9 ± 1.8° (p = 0.003), respectively.

Lateral ROM increased at C4/5 (0.6 ± 0.8°, p = 0.034) and C5/6 (1.0 ± 1.4°, p = 0.050), although no changes in coupled axial rotational ROM were noted.

During axial head rotation, segmental ROM increased at C3/4 (1.3 ± 1.4°, p = 0.006), C4/5 (1.1 ± 1.6°, p = 0.034), and C6/7 (0.9 ± 0.8°, p=0.01).

Head ROM relative to the torso increased after manipulation. Lateral bending increased from 72.3 ± 13.3° to 80.7 ± 18.3° (p = 0.023), with axial rotation ROM increasing from 114.8 ± 21.3° to 125.1 ± 20.3° (p = 0.002) and flexion/extension ROM increasing from 94.7 ± 17.5° to 108.0 ± 17.3° (p = 0.019).

Finally, numeric pain rating scale (NPRS) scores improved from 3.7 ± 1.2 prior to manipulation to 2.0 ± 1.4 (p < 0.001) after manipulation.

Clinical Application & Conclusions:

These authors demonstrated the ability to measure clinician-applied force and facet gapping during cervical spinal manipulation. In fact, this study is the first to measure facet gapping during cervical manipulation on live humans! They also demonstrated a trend toward changes in intervertebral motion following manipulation in both target and adjacent motion segments, as well as increased intervertebral ROM in all planes after manipulation. These findings provide a foundation for measurement of kinematic changes during manipulation that could be used by other authors. The results also suggest that the observed clinical and/or functional improvement after manipulation may occur as a result of small increases in intervertebral ROM across multiple motion segments. As well, the methodology of this project allows for the study of force application during manipulation, which may allow investigation into associations between these factors and patient-related outcomes following HVLA manipulation.

Study Methods:

This was a laboratory-based, prospective, observational study. Acute mechanical neck pain was considered to be pain of less than 12 weeks duration without radiation that was reproduced by neck movement and/or provocation tests.

Initial numeric pain rating scale (NPRS) scores, pre-treatment range of motion (ROM) and pre-operative radiographs were obtained. Skin-mounted reflective markers were placed on the head and torso and tracked via conventional motion analysis. Synchronized biplane radiographs were collected at 30 images/second for 3 seconds during each movement trial and at 160 images/second during manipulation. High-resolution CT scans of the cervical spine were obtained and 3-D models were created to define bone-specific anatomic coordinates (6).

Manipulation was performed by a licensed chiropractor with the patient supine, using an articular pillar push technique (7). In a subset of 5 patients, two pressure sensors were placed on the chiropractor’s thumbs to record the force associated with the manual pressure.

Outcome measures included:
  1. the amount and rate of cervical facet joint gapping during manipulation;
  2. pre- to post-manipulation change in ROM; and
  3. pre- to post-manipulation change in pain scores.

Study Strengths / Weaknesses:

  • Well-designed kinematic study, including advanced imaging and motion-capture design,
  • Study population, while low in numbers, met requirements of sample size calculation,
  • Clinically relevant outcomes and testing.
  • Large proportion of initial patient population excluded,
  • Treatment was provided by a single chiropractor,
  • Findings are applicable to acute changes and cannot be extrapolated to long-term outcomes, and
  • Sample size was low.

Additional References:

  1. Fejer R, Kyvik KO, Hartvigsen J. The prevalence of neck pain in the world population: a systematic critical review of the literature. Eur Spine J 2006; 15(6): 834-48.
  2. Gross A, Miller J, D'Sylva J, Burnie SJ, Goldsmith CH, Graham N, et al. Manipulation or mobilisation for neck pain: a Cochrane Review. Man Ther 2010; 15(4): 315-33.
  3. Hurwitz EL. Epidemiology: spinal manipulation utilization. J Electromyogr Kinesiol 2012; 22(5): 648-54.
  4. Hurwitz EL, Carragee EJ, van der Velde G, Carroll LJ, Nordin M, Guzman J, et al. Treatment of neck pain: noninvasive interventions: results of the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders. Spine 2008; 33(4 Suppl): S123-52.
  5. Wong JJ, Shearer HM, Mior S, Jacobs C, Cote P, Randhawa K, et al. Are manual therapies, passive physical modalities, or acupuncture effective for the management of patients with whiplash-associated disorders or neck pain and associated disorders? An update of the bone and joint decade task force on neck pain and its associated disorders by the optima collaboration. Spine J 2016;16(12) : 1598-1630.
  6. Anderst WJ, Donaldson WF, 3rd, Lee JY, Kang JD. Continuous cervical spine kinematics during in vivo dynamic flexion-extension. Spine J 2014; 14(7): 1221-7.
  7. Bergmann T, Peterson D. Chiropractic Technique: Principles and Procedures. St. Louis, MO: Elsevier Mosby; 2011.