PTA 2021 - Spine lecture

The Spine: Structure, Function, and Posture

Overview

  • The spine plays a crucial role in structure, function, and posture.

  • Chapter 14 focuses on the biomechanics of the spine, its stability, posture-related issues, pain etiologies, and management strategies.

Structure and Function

  • Structure: Includes vertebrae, ribs, and joints that provide stability and mobility.

  • Biomechanics: Focuses on movement mechanics and how body parts interact.

  • Stability: Essential for maintaining posture and preventing injury.

  • Impaired Posture: Can lead to pain and dysfunction.

Posture

  • Defined as the alignment of body parts while upright, sitting, or lying down.

    • Evaluated by the positions of joints and segments, and the muscle balance across these joints.

  • Impairments can arise from issues in muscles, joints, and connective tissues.

  • Faulty postures can lead to disabilities and limit functionality.

Anatomy of the Spine

  • Vertebrae Count: 33 total (7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, 3-4 coccygeal).

  • Ribs: 12 pairs articulate with the thoracic spine.

  • Joints: Includes cranium at occipital-atlas joint and pelvis at sacroiliac joint.

Pillars of the Spine

  • Anterior Pillar: Comprises vertebral bodies and intervertebral discs, serves as weight-bearing and shock-absorbing architect.

  • Posterior Pillar: Formed by articular processes and facet joints, facilitates movement.

Motion Dynamics of the Spine

  • Six Degrees of Motion:

    • Flexion/extension/rotation/lateral flexion/distraction/compression and lateral shear.

Zygapophyseal (Facet) Joints

  • Cervical Spine:

    • Craniovertebral Region: Contains the occipito-atlanto (OA) and atlanto-axial (AA) joints; allows flexion, extension, and rotation.

    • Cervical Region: Features angled facet joints; motion typically couples side bending and rotation.

Intervertebral Discs

  • Annulus Fibrosus: Outermost ring providing tensile strength.

  • Nucleus Pulposus: Gelatinous center that distributes pressure; maintains alignment during motions.

Biomechanical Influences on Postural Alignment

  • The spine has established curvatures categorized as primary (kyphosis) and compensatory (lordotic).

    • Importance of curves for managing gravitational effects and external forces.

Gravity's Role in Posture

  • Gravity challenges postural stability; muscles and inert structures counteract this force to maintain upright posture.

  • Proper alignment involves specific landmarks through the body.

Stability Measures

  • Stability is defined by the line of gravity (LOG) within the base of support (BOS).

  • Strategies to improve stability include lowering the center of gravity or increasing base of support.

Postural Stability in the Spine

  • Comprised of three systems:

    • Passive (inert structures)

    • Active (muscles)

    • Neural Control

    • Imbalance in any subsystem can lead to instability.

Impairment and Pain Etiology

  • Mechanical Stress: Can cause pain without inflammation; alleviation involves addressing stress on sensitive structures.

  • Postural Support: Relaxation leads to exaggerated spinal curves; impaired support increases risk of injury.

  • Muscle Endurance: Weakness develops from sustained postures, increasing strain on inert tissues.

Common Faulty Postures

  • Types of Postures:

    • Increased lumbar lordosis

    • Increased thoracic kyphosis

    • Decreased lordosis in lumbar and cervical regions

    • Slouched posture causes shifting of the pelvic segment and compensatory thoracic kyphosis.

  • Scoliosis: Lateral curvature can be structural (irreversible) or non-structural (flexible).

Management Strategies

  • Awareness and Control: Train patients to isolate and align body segments properly.

  • Mobility and Muscle Performance: Important to identify and address specific restrictions; strengthens muscles to improve endurance.

  • Ergonomics: Adapt working and daily activities to reduce postural stresses.