The TrunkSpine largest segment of body most significant

The Trunk/Spine • largest segment of body • most significant functional unit for general movement • integral role in upper and lower extremity function • relatively little movement between 2 vertebrae 1

The Vertebral Column 7 cervical vertebrae develop as an infant begins to lift its head Cervicothoracic junction 12 thoracic vertebrae present at birth Thoracolumbar junction 5 lumbar vertebrae develop in response to weight bearing Lumbosacral junction Sacrum - 5 fused vertebrae Coccyx - 4 -5 fused vertebrae 2

Vertebral Articulation • each articulation is a fully encapsulated synovial joint • these are often called apophyseal joints Superior articular process Inferior articular process Note: the processes are bony outcroppings. 3

Costal (Rib) Articulation Superior costal facet Transverse costal facet Note: the facets are the articular surfaces. Inferior costal facet 4

Transverse process Body Vertebral foraman Spinous process Intervertebral foraman 5

Muscular Attachments • muscular attachments on spinous and transverse processes 6

Vertebral shape changes to reflect movements possible within a given region 7

Further depiction of vertebral shapes 8

Motion Segment: Functional unit of the vertebral colum Neural arches intervertebral joints transverse & spinous processes ligaments Two bodies of vertebrae common vertebral disc ant & post longitudinal ligaments 9

Intervertebral Disks ‘shock absorbers’ of the spine capable of withstanding compressive torsional and bending loads role is to bear and distribute loads in vertebral column and restrain excessive motion in vertebral segment 10

Shock Absorbers Bending Loads 11

• 2 regions of vertebral disk Disc is avascular & aneural NP -- nucleus pulposus so healing of a damaged disc is • gel-like mass in center of disk under unpredictable & not promising pressure such that it preloads disk Disc rarely fails under compression • 80 -90% water, 15 -20% collagen vertebral body will usually fracture AF -- annulus fibrosus before damage to disc occurs • fibrocartilaginous material • 50 -60% collagen 12

Anterior Motion Segment Ant. Longitudinal ligament very dense & powerful attaches to ant disc & vert body limits hyperextension and fwd mvmt of vertebrae relative to each other Post. Longitudinal Ligament travels inside the spinal canal connects to rim of vertebral bodies & center of disc posterolateral aspect of segment not covered - this is a common site for disc protrusion offers resistance to flexion 13

Posterior Motion Segment Bone tissue in the pedicles and laminae is very hard providing good protection for spinal cord Muscle attachments at spinous & transverse processes articulation between vertebrae occurs at superior and inferior facets these facets are oriented at different angles related to spinal section accounting for functional differences 14

Posterior Motion Segment Ligamentum flavum spans laminae connecting adjacent vertebral arches very elastic thus aids in extension following flexion of the trunk under constant tension to maintain tension on disc Supraspinous and interspinous ligaments span spinous processes resist shear and forward bending of spine 15

Spinal Movement • • collectively -- LARGE ROM flex/ext L-R rotation L-R lateral flexion 16

MOVEMENTS OF THE SPINE ACCOMPANIED BY PELVIC TILTING 1 st 50 -60º in lumbar vertebrae Flexion beyond 50º due to anterior pelvic tilting 17

Regional ROM in Spine Atlas (C 1) & axis (C 2) account for 50% of rotation in the cervical region. Thoracic region is restricted, mainly due to connection to ribs. 18

Spine Posterior Muscular Support primarily produce extension and medial/lateral flexion • Superficial to deep – erector spinae – semispinalis – deep posterior 19

Spine Posterior Muscular Support primarily produce extension and medial/lateral flexion • Posteriorly – erector spinae iliocostalis longissumus thoracis spinalis 20

spinalis longissimus Erector spinae Versatile muscles that can generate rapid force yet are fatigue resistant cervicis iliocostalis thoracis lumborum 21

Semispinalis capitis cervicis thoracis 22

IT IS intertransversarius interspinales Deep posterior multifidus rotatores 23

rectus abdominis Abdominals transverse abdominus internal oblique external oblique 24

Intra-Abdominal Pressure acts like a “balloon” to expand the spine thus reducing compressive load, this in turn reduces the activity in the erector spinae Internal & external oblique muscles & transverse abdominis attached to the thoracolumbar fascia covering the posterior region of the trunk when these abdominals contract - added support for the low back is created 25

Additional muscles contributing to trunk flexion Collectively known as the iliopsoas Powerful flexor whose action is mediated by the abdominals Quadratus lumborum forms lateral wall of abdomen also maintains pelvic position during swing phase of gait 26

Movement into fully flexed position 1) initiated by abdominals (1/3 of flexor moment) and iliopsoas 2) once it has begun gravity becomes a contributing factor such that the erector spinae act eccentrically to control the movement (thru ~50 -60º) 3) beyond 50 -60º flexion continues by anterior tilt of pelvis this mvmt is controlled by an eccentric action of hamstrings and gluteus maximus while erector spinae contribution diminishes to zero 4) in this fully flexed position the posterior spinal ligaments and the passive resistance in the erector spinae resist further flexion 5) this places the ligaments at or near the failure strength placing a greater importance on the load sustained by the thoracolumbar fascia loads supported thru the lumbar articulations 6) return to standing posture initiated by posterior hip muscles 7) erector spinae (1/2 of extensor moment) muscle active initially but peak activity during the final 45 -50º of movement 27

Strength of Trunk Movements Extension Flexion (70% of extension) Lateral Flexion (69% of extension) Rotation (43% of extension) 28

Postural Alignment • 2 naturally occurring curves – LORDOTIC (in lumbar region) – KYPHOTIC (in upper thoracic lower cervical regions) – Abnormalities -- accentuated vertebral curves 29

Lumbar Lordosis • exaggeration of the lumbar curve • associated w/weakened abdominals (relative to extensors) • characterized by low back pain • prevalent in gymnasts, figure skaters, swimmers (flyers) 30

Thoracic Kyphosis • exaggerated thoracic curve • occurs more frequently than lordosis • mechanism -- vertebra becomes wedge shaped • causes a person to “hunch over” 31

Kyphosis • aka “Swimmer’s Back” • develops in children swimmers who train with an excessive amount of butterfly • also seen in elderly women suffering from osteoporosis 32

Scoliosis • lateral deviation of the spinal column • can be a ‘C’ or ‘S’ shape • involves the thoracic and/or lumbar regions • associated w/disease, leg length abnormalities, muscular imbalances 33

Scoliosis • more prevalent in females • cases range from mild to severe – small deviations may result from repeated unilateral loading (e. g. carrying books on one shoulder) 34

Consequences of Pelvic Tilt • in normal standing the line of gravity passes ventral (anterior) to the center of the 4 th lumbar vertebral body Tm • This creates a forward bending torque which must be counterbalanced by ligaments and muscles in the back • any movement or displacement of this line of gravity affects the magnitude of the bending moment (or torque) • slouched posture support comes from ligaments – this is bad for extended periods of time TW 35

Pelvic Tilt and Lumbar Loading • relaxed standing: the angle of inclination of the sacrum (sacral angle) is 30 to the transverse plane 36

Pelvic Tilt and Lumbar Loading • posterior pelvic tilt reduces the sacral angle or flattens the lumbar spine (reduces lordosis) • causes the thoracic spine to extend which adjusts line of gravity such that muscle expenditure is minimized • BUT load is now passed on to ligaments 37

Pelvic Tilt and Lumbar Loading • anterior pelvic tilt increases sacral angle • accentuate lumbar lordosis and thoracic kyphosis • this adjusts line of gravity to increase muscle energy expenditure 38

Pelvic Tilt and Sitting • Sitting (relative to standing) – pelvis posteriorly tilted – lumbar curvature is flattened – line of gravity (already ventral to lumbar spine) shifts further ventrally – increases the moment created by body weight about the lumbar spine – increased muscular support increases the load on the spine vs. 39

Pelvic Tilt and Sitting • erect sitting – pelvis tilts anteriorly – increases lumbar curvature – reduces the moment arm of body weight – reduces need for muscular support – reduces load on lumbar spine – however, pelvis still much more tilted than during normal erect standing vs. 40

L 3 Load • lowest when lying supine • normal when standing upright • 140% when sitting with no back support • 150% when hunched over • 180% when sitting hunched over with no back support 41

• apparent that lumbar load is strongly related to support needed to maintain lumbar lordosis • in erect, supported sitting the addition of a back rest reduces lumbar load • reclining seated position reduces disc pressure even further 42

Spinal Injuries 43

Progression of Disc Degeneration 44

Degenerative Disks • lose ability to retain • ability to distribute • disk integrity water in disk so load across disk decreases with disks “dry out” changes age 45

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Herniated Disks • NP protrudes out from between the vertebrae • nerves are impinged by the bulging NP • lead to numbness and/or pain 47

Tearing of Annulus Disk Herniation 48

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Whiplash Rapid flexion/extension injuries in cervical region strain posterior ligaments dislocate posterior apophyseal joints 7 th cervical vertebra is likely site for fracture in this injury 52

Low Back Pain Vertebral instability 1) Muscle strain from lifting may create muscle spasms 2) distorted posture for long periods of time 3) avoid crossing legs at the knee 4) tight hamstrings or inflexible iliotibial band 5) weak abdominals 53

Lift With Your Legs • What does this mean? – the idea is to keep the weight (W) as close to the axis of rotation as possible smaller muscular torque axis W 54