Subclinical Neck Pain and the Effects of Cervical Manipulation on Elbow Joint Position Sense

1. Subclinical Neck Pain and the Effects of Cervical Manipulation on Elbow Joint Position Sense Heidi Haavik, PhD, BSc (Chiro), and Bernadette Murphy, PhD, DC J Manipulative PhysiolTher 2011:34:88-97

2. Background • Segmental restriction may lead to maladaptive neuroplastic changes. • These changes have been implicated in long-term pain conditions and may cause changes in proprioception. • Cervical spinal dysfunction disturbs proprioception from the neck and upper limb. • Head and neck position may also influence upper limb proprioception. • Reduced accuracy of elbow joint position sense (JPS). • Subclinical Neck Pain (SCNP) • Definition: Reoccurring neck dysfunction such a mild neck pain, ache, and/or stiffness with or without a history of known neck trauma. Do not have constant symptoms and have not sought treatment. • Use: Explore neurophysiologic dysfunction without the confounding effect of pain.

3. Hypotheses • Restricted segments of the spine may represent an ongoing state of altered afferent input that could induce maladaptive neuroplastic changes possibly impacting proprioception. • High-velocity, low-amplitude (HVLA) manipulation has a neuromodulatory effect on central nervous system (CNS) function, thus spinal manipulation may improve central proprioceptive processing.

4. Aims • Determine whether elbow JPS accuracy differs between subclinical neck pain (SCNP) participants and those with no history of any neck symptoms or injury • Determine whether manipulating (adjusting) dysfunctional cervical segments in the SCNP group can improve the accuracy of the elbow JPS.

5. Experimental Protocol • 2 groups: SCNP (n=25) (no acute pain but history of subclinical pain) vs. Healthy control (n=18) (no history of neck pain or injury). • Control: 11/18 had no intervention to assess for learning and boredom effects. • Exclusion: History of shoulder/elbow pain, current pain anywhere in the body, diagnosis of degenerative joint disease (DJD), anything effecting the sensory system, and if they sought treatment. • 14/25=had a previous head, neck, whiplash injury.

6. Experimental Protocol Also assessed for cervical dysfunction Continuous EMG ensured total rest throughout passive and rest conditions of the data collection procedure.

7. Experimental Protocol 4 things that reduced sensory cues: Cloth doughnut (elevated arm so forearm did not touch the surface. Eyes were closed during each experimental condition. JPS was performed at the midrange movement to decrease cues from skin/tendon stretch and joint contact at end ROM. Speed of arm positioning varied.

8. Experimental Protocol

9. Experimental Protocol

10. Data and Statistical Analysis Accuracy (i.e. angle reproduction) was assessed using 3 parameters: • Absolute Error-magnitude of the error; absolute difference (in either direction). • Constant error-direction and magnitude of error (diff. b/w the presented and reproduced angles). • Variable error-standard deviation (SD) of the mean constant error.

11. Data and Statistical Analysis • Overall accuracy • Multifactorial ANOVA • GROUP (SCNP vs. control group) • CONDITION (neutral, flexion, left rotation, and combined flexion with left-rotation) • Effect of adjusting dysfunctional segments • Multifactorial, repeated measures ANOVA • TIME (pre and post measures) • CONDITION (neutral, flexion, left rotation, and combined flexion with left-rotation) • GROUP (SCNP vs. control group) • Pairwise comparisons of pre/post intervention data.

12. Results Absolute Error: Overall group effect comparing pre-intervention data. Control group significantly better (p=.04). • FYI… • Absolute Error-magnitude of the error; absolute difference (in either direction). • Constant error-direction and magnitude of error (diff. b/w the presented and reproduced angles). • Variable error-SD of the mean constant error.

13. Results • The effect of cervical adjustments: • Significant interactive effect for TIME , GROUP, and HEAD POSITION (p=.008). • Significant interactive effect for TIME and GROUP (p<.001). • Further analysis of SCNP • Overall effect for TIME (p<.001) • Significant interactive effect for TIME and HEAD position (p=.025).

14. Results • A priori pairwise comparisons of pre/post adjustment data. • Significant improvement in JPS after adjustments when the participants had their heads in: • Neutral (p<.04) • Full left rotation (p=.01)

15. Results • When participants were asked to repeat previously presented angle: Neutral control position • Before neck manipulation • Mean absolute error 3.31 (95% CI 2.93-3.68) • After neck manipulation • Mean absolute error decreased • 2.47 (95% CI 2.11-2.83) Full left rotation • Before neck manipulation • Mean absolute error=3.69 (95% CI 3.13-4.25). • After manipulation • Mean absolute error=2.90 (95% CI 2.49-3.31).

16. Results • Control group data: • Significant overall effect with the control participants less able to accurately repositioning their arms after the control intervention (p=.03). *?

17. Results • No significant group differences in variance (fig.3?). • Variance data assessing any effect from cervical manipulation revealed a significant interactive effect (p=.03), with variance error decreasing significantly after the adjustment. • Analysis of control group, significant overall effect (p<.001), with variance increasing significantly after the control.

18. Results • No significant group differences in constant error (fig.3?). • The interventions had no significant effect on constant error. • No significant effect due to head position was found in any of the calculated variables for either group, neither before nor after either intervention. • No significant group differences in background EMG for any muscle nor were there any changes in background EMG for any muscle after either intervention.

19. Conclusion by Authors • Participants with a self-reported history of SCNP have significantly worse elbow JPS compared to people that have no neck complaints and that a single session of HVLA adjustments of dysfunctional cervical joints resulted in a significant improvement of elbow JPS.

20. Discussion • Head and neck positions did not worsen JPS. • Possible methodological differences between this and previous studies. • In neck pain patients, proprioception and motor control rather than pain may be the “main factors” in the clinical picture. • This study: SCNP had worse JPS accuracy than control supports this. • Deficits in proprioception may be partly due to segmental dysfunction, which chiropractors treat. • Manipulation improved JPS accuracy in SCNP • Beneficial neuromodulaty effect • Dysfunctional segments, which may a source of altered afferent signaling leading to altered sensorimotor integration, may be normalized by HVLA-SM.

21. Limitations/Bias • Control- JPS accuracy was worse after control intervention. • Possible reasons why this occurred: • Time between pre/post measures (arms falling asleep) • Use of the supine position may have lead to upper limb sensory disturbances (vs. a reliable seated patient position). • Boredom effect in control • Placebo effect in SCNP • Avis Effect (participants responded because they were involved in a study).

22. Journal Club Discussion • What were the weaknesses of the article? • What were the strengths? • Are you convinced that SCNP participants have worse elbow JPS? • Do you feel that cervical spinal manipulation improved elbow JPS?

23. Thank You! • Thank you for attention! • Thank you Dr. Reed!