The Spine: Structure, Function, and Posture Chapter 14

Posture and Biomechanical Influences

Functional Components of the Spine Anterior Pillar Posterior Pillar Structure and Function of the Spine Figure 14.1 illustrates (A) lateral and (B) posterior views showing the five regions of the spinal column. Shown here, Figure 14.2 illustrates spinal segment showing (A) the anterior weight-bearing, shock-absorbing portion, and (B) the posterior gliding mechanism and lever system for muscle attachments.

Motions of the Spine Six Degrees of Motion Flexion/extension Side bending Rotation Anterior/posterior shear Lateral shear Compression/distraction Structure and Function of the Spine Figure 14.3 illustrates motions of the spinal column.

Arthrokinematics of the Zygapophyseal (Facet) Joints Cervical Spine Thoracic Spine Lumbar Spine Structure and Function of the Spine Table 14.1 summarizes Arthrokinematics of the Spine.

Structure and Function of the Intervertebral Discs Annulus Fibrosus Nucleus Pulposus Cartilaginous End-plates Structure and Function of the Spine Shown here, Figure 14.6 illustrates the intervertebral disc. (A) The annular rings enclose the nucleus pulposus, providing a mechanism for dissipating compressive forces. (B) Orientation of the layers of the annulus provides tensile strength to the disc with motions in various directions.

Intervertebral Foramina Located between each vertebral segment in the posterior pillar Anterior boundary: intervertebral disc Posterior boundary: facet joint Superior and inferior boundaries: pedicles of the superior and inferior vertebrae of the spinal segment Size is affected by spinal motion Structure and Function of the Spine Intervertebral foramina are larger with forward bending and contralateral side bending. They are smaller with extension and ipsilateral side bending.

Biomechanical Influences on Postural Alignment Curves of the Spine Gravity (the gravity line) Ankle-anterior Knee-anterior Hip-variable with sway Trunk-bodies of cervical and lumbar vertebrae Head-anterior to AO joint Figure 14.7 illustrates the lateral view of standard postural alignment.

Stability Postural Stability in the Spine Inert Structures: Influence on Stability Muscles: Influence on Stability Role of global and segmental muscle activity Segmental Muscle Activity Table 14.2 summarizes Stabilizing Features of Inert Tissues in the Spine. Table 14.3 summarizes Stabilizing Features of Muscles Controlling the Spine.

Muscle Control in the Lumbar Spine Abdominal Muscles Transverse Abdominis Stabilization Activity Erector Multifidus Stabilization Activity Thoracolumbar (Lumbodorsal) Fascia Muscles: Influence on Stability Table 14.4 summarizes Muscles of the Spine and Their Stabilizing Function.

Muscle Control in the Cervical Spine Mandibular Elevator Group Suprahyoid and Infrahyoid Group Rectus Capitis Anterior and Lateralis, Longus Colli, and Longus Capitis Multifidus Muscles: Influence on Stability

Role of Muscle Endurance Inactivity has been shown to change muscle fiber composition, leading to decreased muscular endurance during sustained or repetitive activities Muscles: Influence on Stability FOCUS ON EVIDENCE: In a study that looked at 17 mechanical factors and the occurrence of low back pain in 600 subjects (ages 20 through 65), poor muscular endurance in the back extensors muscles had the greatest association with low back pain.

Stability Neurological Control: Influence on Stability Feedforward control and spinal stability Effects of Limb Motion on Spinal Stability Localized muscle fatigue Muscle imbalance Effects of Breathing on Posture and Stability Effects of Intra-Abdominal Pressure and the Valsalva Maneuver Figure 14.16 illustrates coordinated contraction of the transversus abdominis, diaphragm, and pelvic floor musculature.

Impaired posture

Etiology of Pain Effect of Mechanical Stress Effect of Impaired Postural Support from Trunk Muscles Effect of Impaired Muscle Endurance Pain Syndromes Related to Impaired Posture Postural fault Postural pain syndrome Postural dysfunction Postural habits

Common Faulty Postures: Characteristics and Impairments Pelvic and Lumbar Region Lordotic posture Relaxed or slouched posture Flat low back posture Cervical and Thoracic Region Round back (increased kyphosis) with forward head Flat upper back and neck posture Figure 14.18 illustrates four different postures.

Common Faulty Postures: Characteristics and Impairments (cont'd) Frontal Plane Deviations, Scoliosis, and LE Asymmetries Scoliosis Structural Nonstructural Frontal plane deviations from LE asymmetries Characteristic deviations Figure 14.19 illustrates structural scoliosis. Figure 14.20 illustrates frontal plane asymmetries.

Management of Impaired posture

General Management Guidelines Awareness and Control of Spinal Postures Posture training techniques Axial extension (cervical retraction) to decrease a forward head posture Scapular retraction Pelvic tilt and neutral spine Thoracic spine Total spinal movement and control Reinforcement Postural support Box 14.1 contains Management Guidelines: Impaired Posture. Figure 14.21 illustrates training the patient to correct (A) forward-head posture and (B) protracted scapulae.

General Management Guidelines (cont'd) Posture, Movement, and Functional Relationships Relationship of impaired posture and pain Relationship of impaired posture and extremity function Joint, Muscle, and Connective Tissue Mobility Impairments Impaired Muscle Performance Body Mechanics Box 14.2 contains Stretching Techniques for Common Mobility Impairments. Box 14.3 contains Training and Strengthening Techniques for Common Muscle Impairments. Box 14.4 Functional Exercises in Preparation for Safe Body Mechanics.

General Management Guidelines (cont'd) Ergonomics Stress Management/Relaxation Muscle relaxation techniques Cervical and upper thoracic region Lower thoracic and lumbar region Conscious relaxation training for the cervical region Modalities and massage Healthy Exercise Habits

Independent Learning Activities Critical Thinking and Discussion Laboratory Practice Case Studies