Relationship Between Craniovertebral Angle, Lumbar Proprioception, and Trunk Muscle Strength in Cervical Radiculopathy

Cervical radiculopathy is a major disabling condition characterized by neck pain radiating to one or both of the upper extremities . Epidemiological data suggest that CR affects approximately 83 per 100,000 individuals annually, with peak incidence occurring between ages 40 and 50 years and a lifetime prevalence of 3.5% in the general population .

Cervical radiculopathy is a common neurological condition caused by nerve root compression. Cervical radiculopathy is frequently associated with neck pain and includes tingling, numbness, or discomfort in the arm, upper back, and upper chest with or without an associated headache. Frequent headaches, scapular pain, and sensory, motor and reflex dysfunction in the upper extremities are often associated with cervical radiculopathy. These symptoms can be extended to the neck muscles, zygapophyseal joints, intervertebral discs, nerve roots, or trunk. In addition, higher levels of self-reported disability are reported among patients with neck pain and cervical radiculopathy .

The underlying cervical spinal pathologies, including disc herniation, osteophyte formation, and spinal canal stenosis, are widely recognized as common precipitating factors for nerve root compression or inflammation in CR . Approximately 70-75% of CR cases co-occur with degenerative changes, while 20-25% are attributed to intervertebral disc herniation. Repetitive overloads and micro-injuries lead to spinal canal narrowing and disc degeneration via the hypertrophy of the spinal joints and the encroachment of surrounding structures. This degeneration promotes osteophyte formation, elevated levels of local prostaglandins causing inflammation near the dorsal root ganglion .

According to the latest Global Burden of Disease data, neck pain is the fourth leading cause of years lived with disability, following only back pain, major depressive disorder, and arthralgias .Over the past ten years, there has been an increase of 19% in both the prevalence of cervical spine pain and the number of years people have been disabled globally.

Forward head posture (FHP) is a poor habitual neck posture resulting from the prolonged inherence of a static awkward position .It is associated with muscle imbalance and joint decentration, particularly at the atlanto-occipital joint, C4-C5 segment, glenohumeral joint, cervicothoracic joint, and T4-T5 segment . FHP has been viewed as a cervical sagittal imbalance and is defined as an increase in C2-C7 sagittal vertical alignment (SVA). Lately, cervical sagittal vertical alignment has been found to be the most relevant parameter of cervical sagittal balance in distinguishing symptomatic subjects from asymptomatic subjects .

FHP-induced changes in cervical alignment exaggerate the extension of the upper cervical vertebrae (C1-C2) and flexion of the lower cervical vertebrae (C3-C7) in the sagittal plane, increasing the load on the cervical discs and joints . In FHP, the deep cervical flexor ,which plays an important role in the stability of the cervical vertebra, is weakened and elongated, resulting in lower cervical flexion, and the upper trapezius, suboccipital, semispinalis, splenius, sternocleidomastoid, and levator scapula muscles are shortened, resulting in hyperextension of the upper cervical vertebra . The occurrence of FHP is increasing as the time spent using smartphones and computers increases . FHP is also caused by carrying a heavy backpack, sitting in front of a computer screen for a long time without using a desk and chair properly for physique, and not exercising .

FHP evaluation is often based on the cranio-vertebral angle (CVA) between the horizontal line passing through the spinous process of C7 and the line connecting the tragus of the ear to the spinous process of C7 . The normal Craniovertebral angle ranges between 48-50 degrees, Anything less the 48 degrees is defined as Forward head . As CVA decreases, neck pain increases, leading to chronic pain that causes physical changes and dysfunction .

A forward head posture (FHP) produces various negative symptoms such as neck ache, shoulder pain, upper back pain, persistent headaches, increased curvature of the spine, and scapular dyskinesia . In the long run, this incorrect posture can injure not only the cervical vertebrae and ligaments but also the structures around the lumbar area .

Muscle imbalance due to long-term poor posture habits such as forward head posture leads to asymmetry and functional deterioration of the musculoskeletal system . In the past decade several publications have identified that head and neck alignment plays a role in whole body pain and impairment including LBP and related disorders. Studies have identified that several of the postural upright postural neurophysiological reflexes, are located within the head and neck region. Relatively few correlational studies were identified linking cervical spine alignment to thoracic spine ailments and full spine alignment to LBP it would seem logical that alterations in cervical spine alignment would influence, at least to some extent, pain and radiculopathy in lumbosacral disorders leading to low back pain .

Lower back pain (LBP) is a common musculoskeletal condition characterized by discomfort or pain in the lower region of the spine . Low back pain is a group of symptoms characterized by pain, muscle tension, soreness and/or stiffness from the bottom of the rib cage to the buttock folds, sometimes accompanied by sciatic pain . The lower back is the most commonly reported complaint area in musculoskeletal conditions, leading to pain, disability, and a reduction in overall life quality . LBP affects the physical, psychological, and social areas and carries a great socioeconomic burden, as it is the main cause of work absenteeism and the excessive use of therapeutic service.

Lumbar proprioception or Lumbar Repositioning Error (LRPE) refers to an individual's capacity to perceive and control the precise position of their lumbar spine. An adequate lumbar repositioning is crucial for sustaining spinal stability and an optimal function during activities. Proprioception involves conscious and unconscious awareness of joint position sense, kinesthesia, and force sense of body parts without vision, Since paraspinal muscles contain abundant muscle spindles ,they play an important role in generating proprioceptive signals to monitor midrange spinal motion . When lumbar repositioning is inaccurate, it can lead to ineffective movement patterns that might contribute to the development of low back pain.

Trunk muscles are the active neuromuscular system that responsible for maintaining stability of the spine as the spine needs to be mechanically stable at all times to avoid injuries that can eventually lead to pain. The trunk is the center of the kinematic chains, transferring forces and acting as a bridge between the upper and lower extremities. Multiple factors have been associated with the occurrence of LBP, among them the alteration of the neuromuscular response of the trunk . The deconditioning or decrease in the function of the lumbar musculature ,the reduction in the muscular mass of the trunk , and the reduction in the muscular strength of the trunk . Decreased trunk muscle strength could be considered risk factors for developing LBP, specifically isometric and isokinetic strength of trunk flexors and lumbar extensors muscles .