Clinician proficiency in delivering manual treatment for neck pain within specified force ranges

Design and Validation of a Novel Robotic Neck Brace for Cervical Traction

Cervical traction is a common and effective treatment for degenerative disk diseases and pain in the cervical spine. However, the manual or mechanical methods of applying traction to the head-neck are limited due to variability in the applied forces and orientation of the head-neck relative to the shoulder during the procedure. Current robotic neck braces are not designed to provide independent rotation angles and independent vertical translation, or traction, to the brace end-effector connected to the head, making them unsuitable for traction application. This work proposes a novel architecture of a robotic neck brace, which can provide vertical traction to the head while keeping the head in a prescribed orientation, with flexion and lateral bending angles. In this paper, the kinematics of the end-effector attached to the head relative to a coordinate frame on the shoulders are described as well as the velocity kinematics and force control. The paper also describes benchtop experiments designed to validate the position control and the ability of the brace to provide a vertical traction force. It was shown that the maximum achievable end-effector orientations are 16° in flexion, 13.9° in extension, and ± 6.5° in lateral bending. The kinematic model of the active brace was validated using an independent motion capture system with a maximum root mean square error of 2.41°. In three different orientations of the end-effector, neutral, flexed, and laterally bent, the brace was able to provide a consistent upward traction force during intermittent force application. In these configurations, the force error has standard deviations of 0.55, 0.29, and 0.07N, respectively. This work validates the mechanism's ability to achieve a range of head orientations and provide consistent upward traction force in these orientations, making it a promising intervention tool in cases of cervical disk degeneration.

High-velocity, low-amplitude spinal manipulation training of prescribed forces and thrust duration: A pilot study

OBJECTIVE

High-velocity, low-amplitude spinal manipulation (HVLA-SM) may generate different therapeutic effects depending on force and duration characteristics. Variability among clinicians suggests training to target specific thrust duration and force levels is necessary to standardize dosing. This pilot study assessed an HVLA-SM training program using prescribed force and thrust characteristics.

METHODS

Over 4 weeks, chiropractors and students at a chiropractic college delivered thoracic region HVLA-SM to a prone mannequin in six training sessions, each 30 minutes in duration. Force plates embedded in a treatment table were used to measure force over time. Training goals were 350 and 550 Newtons (N) for peak force and ≤150 ms for thrust duration. Verbal and visual feedback was provided after each training thrust. Assessments included 10 consecutive thrusts for each force target without feedback. Mixed-model regression was used to analyze assessments measured before, immediately following, and 1, 4, and 8 weeks after training.

RESULTS

Error from peak force target, expressed as adjusted mean constant error (standard deviation), went from 107 N (127) at baseline, to 0.2 N (41) immediately after training, and 32 N (53) 8 weeks after training for the 350 N target, and 63 N (148), -6 N (58), and 9 N (87) for the 550 N target. Student median values met thrust duration target, but doctors' were >150 ms immediately after training.

CONCLUSION

After participation in an HVLA-SM training program, participants more accurately delivered two prescribed peak forces, but accuracy decreased 1 week afterwards. Future HVLA-SM training research should include follow-up of 1 week or more to assess skill retention.

Neural Responses to Physical Characteristics of a High-velocity, Low-amplitude Spinal Manipulation: Effect of Thrust Direction

STUDY DESIGN

Electrophysiological recordings were obtained from proprioceptors in deep lumbar paraspinal muscles of anesthetized cats during high-velocity low-amplitude spinal manipulation (HVLA-SM).

OBJECTIVE

To determine how thrust direction of an HVLA-SM affects neural input from back musculature.

SUMMARY OF BACKGROUND DATA

A clinician's ability to apply the thrust of an HVLA-SM in a specified direction is considered an important component of its optimal delivery. However, previous biomechanical studies indicate that the shear force component of the thrust vector is not actually transmitted to paraspinal tissues deep to the thoracolumbar fascia because the skin-fascia interface is frictionless.

METHODS

Neural activity from muscle spindles in the multifidus and longissimus muscles was recorded from L6 dorsal rootlets in 18 anesthetized cats. After preload to the spinal tissues, HVLA-SMs (100-ms thrust duration) were applied through the intact skin overlying the L6 lamina. Thrusts were applied at angles oriented perpendicularly to the back and obliquely at 15° and 30° medialward or cranialward using a 6 × 6 Latin square design with three replicates. The normal force component was kept constant at 21.3 N. HVLA-SMs were preceded and followed by simulated spinal movement applied to the L6 vertebra. Changes in mean instantaneous discharge frequency (ΔMIF) of muscle spindles were determined both during the thrust and spinal movement.

RESULTS

ΔMIFs during the HVLA-SM thrust were significantly greater in response to all thrust directions compared with the preload alone, but there was no difference in ΔMIF for any of the thrust directions during the HVLA-SM. HVLA-SM decreased some of the responses to simulated spinal movement but thrust direction had no effect on these changes.

CONCLUSION

The shear force component of an HVLA-SM's thrust vector is not transmitted to the underlying vertebra sufficient to activate muscle spindles of the attached muscles. Implications for clinical practice and clinical research are discussed.

LEVEL OF EVIDENCE

N/A.

Development of an attention-touch control for manual cervical distraction: a pilot randomized clinical trial for patients with neck pain

Background

Manual cervical distraction (MCD) is a traction-based therapy performed with a manual contact over the cervical region producing repeating cycles while patients lie prone. This study evaluated a traction force-based minimal intervention for use as an attention-touch control in clinical trials of MCD for patients with chronic neck pain.

Methods

We conducted a mixed-methods, pilot randomized clinical trial in adults with chronic neck pain. Participants were allocated to three traction force ranges of MCD: low force/minimal intervention (0-20 N), medium force (21-50 N), or high force (51-100 N). Clinicians delivered five treatments over two weeks consisting of three sets of five cycles of MCD at the C5 vertebra and occiput. Traction forces were measured at each treatment. Patient-reported outcomes included a pain visual analogue scale (VAS), Neck Disability Index (NDI), Credibility and Expectancy Questionnaire (CEQ), and adverse effects. A qualitative interview evaluated treatment group allocation perceptions.

Results

We randomized 48 participants, allocating an average of five each month. Forty-five participants completed the trial with three participants lost to follow-up. Most participants were women (65 %) and white (92 %) with a mean (SD) age of 46.8 (12.5) years. Mean traction force values were within the prescribed force ranges for each group at the C5 and occiput levels. Neck pain VAS demonstrated a benefit for high traction force MCD compared to the low force group [adjusted mean difference 15.6; 95 % confidence interval (CI) 1.6 to 29.7]. Participants in the medium traction force group demonstrated improvements in NDI compared to the low force group (adjusted mean difference 3.0; 95 % CI 0.1 to 5.9), as did participants in the high traction force group (adjusted mean difference 2.7; 95 % CI -0.1 to 5.6). CEQ favored the high force group. Most low force participants correctly identified their treatment allocation in the qualitative interview. No serious adverse events were documented.

Conclusions

This pilot study demonstrated the feasibility of a clinical trial protocol and the utility of a traction-based, minimal intervention as an attention-touch control for future efficacy trials of MCD for patients with neck pain.

Trial registration

ClinicalTrials.gov NCT01765751 (Registration Date 30 May 2012)