Chiropractic + Naturopathic Doctor • JulyAugust 2019 • Research review

STUDY TITLE: An exploratory study examining factors underpinning postural instability in older adults with idiopathic neck pain

The cervical spine is a critical contributor to the overall sensorimotor system that governs movement and balance. This system relies on the ability of cervical mechanoreceptors to integrate multisensory input from the visual, vestibular, proprioceptive and central nervous systems. Patients with neck pain have demonstrated sensorimotor disturbances, often manifesting as impaired postural stability (1). Older patients similarly have poorer dynamic postural stability, which increases the risk of injury due to fall (2). Those who are older and also have neck pain may theoretically be vulnerable via two distinct, yet perhaps related, mechanisms.

The impact of neck pain on the multitude of variables that influence postural control is an important concept and one that requires careful investigation. Decreased levels of physical activity are known to be associated with poorer limb function and consequently contribute to decreased postural stability in older adults with neck pain (3-5). Also, neck pain in older adults is expected to diminish cervical proprioception and vestibular, visual and central nervous system functions, ultimately increasing the risk of falls in older adults with neck pain (6, 7).

This is a complex topic that has not yet been extensively studied. The purpose of this cross-sectional, exploratory study was to understand the mechanisms associated with postural control deficits in older adults with or without neck pain.

84 older adults with (n = 35, average age 69.6 ± 6.3 yrs) and without (n = 49, average age 69.5 ± 4.9) idiopathic neck pain were enrolled in the study.

Physical activity level, lower limb motor and sensory function, vestibular function and visual contrast sensitivity did not differ between the study groups (p > 0.05 for all). Patients with neck pain did demonstrate poorer Activities- Specific Balance (ABC) scale scores (p = 0.01), lower Dynamic Gait Index (DGI) (p = 0.02) and higher Dizziness Handicap Inventory (DHI) scores (p < 0.01). Older patients also showed higher NDI scores (p > 0.001).

Patients with neck pain also demonstrated greater centre-of-pressure (CoP) velocity (both overall and in the A-P axis) in both eyes-open and eyesclosed conditions. CoP and standard deviation of path length were also greater in the eyes-open condition in patients with neck pain. Finally, patients with neck pain demonstrated significantly higher CoP velocity only in the moderate (1.56–6.25 Hz) and low (0.39–1.56 Hz) frequencies in eyes-open and eyes-closed conditions.

The results of this cross-sectional, exploratory study suggest that postural control deficits in older patients with neck pain may not be associated with variables such as physical activity level, lower limb motor or sensory function, vestibular function and visual contrast sensitivity. Rather, impairments to cervical proprioceptive inputs (likely related to their neck pain) are most likely responsible for change in postural activity in this cohort. The authors suggest that further research is necessary to determine the relationship between the observed reduced balance confidence, poorer dynamic balance and higher fall risk in older patients with neck pain. Clinicians should be aware of these concerns when treating such patients.

COMMENT: Unraveling the complex relationship among balance, postural stability, aging and neck pain is a challenging proposition that requires further research. This study adds to our existing body of knowledge and should stimulate clinicians to investigate for these deficiencies in your older patients with neck (or low back?) pain. Simple balance exercises and progressions could form a standard component of treatment provided in addition to manual and other therapies for our older patients, in an effort to preserve and enhance their postural stability and general balance.

This was a cross-sectional, exploratory study conducted on older adults who were recruited via convenience sampling. Participants were added to the neck pain (NP) group if they had chronic NP for ≥ 3 months, a Neck Disability Index (NDI) score of ≥ 10 per cent and neck-related pain of ≥ 2/10 on a Visual Analogue Scale (VAS).

• Activities-Specific Balance (ABC) scale to assess falls-related self-efficacy

Lower limb function: Ankle ROM was assessed using a standard goniometer. Sensory testing evaluated both light touch and vibration sense at the lateral malleolus of the dominant foot.

Vestibular function tests: Participants were screened for vestibular hypofunction via a Dynamic Visual Acuity (DVA) test with a Snellen chart and the head impulse test (HIT) (this combination has been previously validated). Active Benign Paroxysmal Positional Vertigo (BPPV) was screened for via the Dix-Hallpike manoeuvre.

Visual contrast sensitivity: Visual contrast sensitivity evaluated using the Melbourne Edge Test (MET).

Balance: Dynamic balance was assessed using the Dynamic Gait Index (DGI); static balance was evaluated using the Nintendo Wii Balance Board.

• Participants suitably represented the relevant patient population that many of us see in practice

• Vestibular tests may lack precision to detect subtle deficits in eye movement, which may result in underreporting of vestibular deficits

• Dizziness Handicap Inventory (DHI) scores may be misinterpreted as neck pain as opposed to dizziness

• Balance tests performed in multiple settings (laboratory, patient’s home) may lead to inconsistency in the results

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