Chiropractic + Naturopathic Doctor • May 2019 • Research Review

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

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

Neck pain remains one of the most common and disabling MSK complaints globally, with a lifetime prevalence of up to 70 per cent. Neck pain is often treated using high-velocity low-amplitude (HVLA) cervical spine manipulation, which has proven to be an effective treatment modality, 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.

20 patients were recruited for the study. After screening, 15 patients were 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.

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.

DR. SHAWN THISTLE is a practising chiropractor, educator, international speaker, knowledge-transfer leader, evidence-based health care advocate, entrepreneur and medicolegal consultant. He founded RRS Education in 2006 and currently acts as the company’s CEO. RRS Education helps chiropractors and other manual medicine clinicians around the world integrate research into patient care via weekly research reviews, online courses and seminars. rrseducation.com