Spine Biomechanics PDF

TOPIC 11: Biomechanics of the Spine Main functions Protection of the spinal cord Provides mobility and stability to the trunk Absorb and transmit forces. Provides tendon and ligament attachment sites. Organization of the spine: 24 movemeable vertebrae Cervical 7 Thoracic 12...

TOPIC 11: Biomechanics of the Spine Main functions Protection of the spinal cord Provides mobility and stability to the trunk Absorb and transmit forces. Provides tendon and ligament attachment sites. Organization of the spine: 24 movemeable vertebrae Cervical 7 Thoracic 12 Lumbar 5 8-10 fused vertebrae Sacral 5 Coccyx 3-5 4 curvatures Thoracic and sacral (primary: present at birth) Cervical and lumbar (secondary from supporting the body in upright position) Functional unit of the spine: vertebra Vertebral types Spine osteokinematics Degrees of freedom -Flexion/extension -Lateral flexion -Axial rotation Own ROM at each individual joint -Multiple segments: cumulative effect Different mobility for each level: -Cervical -Thoracic -Lumbar Joints of the Human Spine 1. Between vertebral bodies: intervertebral joint 24 joints Symphysis Intervertebral disk -Nucleus pulposus -Annulus fibrosus Weight shock absorber/ Motion Disk behaviour during movements -Distraction -Compression -Torsion 2. Between articular processes: Facet joints/ Zygapophyseal joints 2 joints in each segment (24 pairs): 2 superior processes, 2 inferior. Plane synovial joints (synovial capsule present) Translational movement: gliding -Allow and guide back motion -Limit motion -Weight absorber (20%) Arthrokinematics at the facet joints Spinal stability 1. Passive structures Intervertebral disk Facet joints & capsule Ligaments: -Anterior longitudinal ligament (ALL):Runs the length of the spine anteriorly. Restricts extension! -Posterior longitudinal ligament (PLL): Runs on the posterior surface from sacrum to C2. Restricts flexion! -Supraspinous ligament: Runs the length of the spine posteriorly over the spinous processes. Restricts flexion! -Intertransverse ligaments: Restricts lateral flexion -Ligamentum flavum: Between lamina. Additional protection for nerves. -Interspinous ligaments. Restricts flexion. 2. Active structures: muscles and tendons 3.Nerve roots Exit through the intervertebral foramen Responsible for motor and sensory functions Nerve roots -Ventral portion: motor function -Dorsal portion: sensory function Cervical spine Upper cervical spine: C1-C2 -C1: atlas -C2: axis Lower cervical spine : C3-C7 Atlantoaxial joint (C1-C2) Provides rotational motion ++ Central atlanto-odontoid joint -Between odontoid process and terror arch/ transverse ligament -Pivot joint Two lateral atlanto-axial facet joints -Between articular processes -Plane joints Stability: Anterior atlantoaxial ligament and posterior atlantoaxial ligament Transverse ligament of the atlas: hold dens of C2 against atlas Atlanto-occipital joint (C0-C1) Between two superior articular facets of atlas and occipital condyles Ellipsoid Stability -Posterior atlanto-occipital ligament -Anterior atlanto-occipital ligament Convex rule: occipital bone Cervical spine; Osteokinematics Cervical spine: arthrokinematics (Flexion-Extension) Atlanto-occipital: CONVEX RULE (occipital moving on C1) -Flexion: anterior roll, posterior glide -Extension: posterior roll, anteriorly glide Intracervical facet joints -Flexion: glide anterior and cranial + separation -Extension: glide posterior and caudal + approximation Cervical spine: arthrokinematics (Rotation) Atlanto-occipital: negligible Atlantoaxial facet joints: -Glide posteriorly: homolateral side -Glide anterior: contralateral side Intercervical facet joints -Glide posterior and inferior: homolateral side -Glide anterior and superior: contralateral side Cervical spine: arthrokinematics (Lateral flexion) Atlanto-occipital: CONVEX RULE -Right lat. flexion: roll right, glide left -Left lat.flexion: roll left, glide right Atlanto axial facet joints: negligible Intracervical facet joints -Glide posterior and inferior + compression: homolateral side -Glide anterior and superior + separation: contralateral side Thoracolumbar spine: Osteokinematics Thoracolumbar spine: arthrokinematics (Flex/ext) Facet joints -Flexion: glide anterior and cranial -Extension: glide posterior and caudal Thoracolumbar spine: arthrokinematics (Lateral flexion) Facet joints -Glide inferior: homolateral side -Glide superior: contralateral side Thoracolumbar spine: arthrokinematics (Rotations) Facet joints -Glide posterior: homolateral side -Glide anterior: contralateral side Kinetics of the spine: Intrinsic muscles of the back and neck Control the posture Stabilize: -Trunk and pelvis -Head and neck Produce movement Bilateral vs unilateral activation Gravity Erector spinae Bilateral activation: -Extension: trunk, neck, head -Ant pelvic tilt Unilateral activation -Ispilat Lat flex (+iliocostalis) -Ipsilat rot (+iliocostalis) Transversospinal and short segmental (deep) Bilateral activation: -Extension: trunk, neck, head. -Increase lordosis -Reduce kyphosis -Deep stability Unilateral activation -Ipsilateral: lateral flexion & rotation Anterior-lateral muscles