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Functional Anatomy of the Trunk 7 cervical vertebrae, a convex curve o the anterior side of the body develops as an infant begins to lift its head support the head and assumes its curvature in response to head position 12 thoracic vertebrae convex to the posterior side 5 lumbar vertebrae convex anterior side develops in response to weight bearing influenced pelvic and lower extremity positioning Junction site of great mobility vulnerable to injury →Cervicothoracic, thoracolumbar, and lumbosacral regions curves exaggerated → more mobile curves flat → more rigid Cervical and lumbar most mobile → thoracic and pelvic more rigid Besides support and flexibility, main responsibility protecting the spinal cord The vertebral column acts as a modified elastic rod, providing rigid support and flexibility. 33vertebrae, 24 movable contribute to trunk movements Arranged into 4 curves facilitate support by offering a springlike response to loading Provide balance and strengthen the spine The last curve is the sacrococcygeal curve Canal formed → body, pedicles, pillars of the vertebrae, disc, ligament, ligamentum flavum Peripheral nerves exit through the intervertebral foramen on the lateral side of the vertebrae 1 The Vertebral Column Trunk play a integral role in both upper and lower extremity function Anatomical and Functional Characteristics of The Joints First two cervical vertebrae have unique structure Motion segment Motion Segment:Anterior Portion Two bodies, intervertebral disc, anterior and posterior longitudinal ligaments Vertebral body is tube-shaped and thicker on the front side Absorbs large amounts of compressive forces The disc is withstanding compressive forces as well as torsional and bending forces applied to the column bear and distribute loads in the vertebral column restrain excessive motion in the vertebral segment Load transmitted via the intervertebal discs distributes stress uniformly over the vertebral end plates It consists of cancellous tissue surrounded by a hard cortical layer and has a raised rim that facilitates attachment of the disc, muscles, and ligaments Surface of the body is covered with hyaline cartilage, forming articular end plates into which the disc attaches responsible for most of the mobility in the spine 2 Each disc consists of the nucleus pulposus and the annulus fibrosus Gel-like spherical mass in the →central portion of the cervical and thoracic discs →posterior in the lumbar discs nucleus pulposus 80 to 90% water, 15 to 20% collagen, creating a fluid mass always under pressure exerting a preload to the disc well suited for withstanding compressive forces The day, water content reduced with compressive forces during daily activities, resulting shortening of the column by about 15 to 25mm height and volume reduced 20% bulge radially outward, increase the axial loading on the posterior joints At night, imbibes water, restoring height to the disc The elderly is less(approximately 70 %) imbibe reduced, leaving a shorter vertebral column Trunk rotation, annulus fibrosis become taut and the rest relax Compressive – tension force 3 Motion Segment:Posterior Portion Includes the neural arches, the intervertebral joints, transverse and spinous processes and ligaments Facets different angles in the cervical, thoracic, and lumbar regions of the functional differences Prevent the forward displacement of one vertebra over another and participate in load bearing Hyperextended position, joints bear 30 % of the load Highest pressures in the joints occur with combined torsion, flexion, and compression Movements of The Total Spine Motion is small, restricted by the discs and the arrangement of the facets 110-140° 75-85° 90° Pedicles and laminae is very hard →providing good resistance to the large tensile forces The spinous and transverse processes serve as attachment sites for the spinal muscles running the length of the column Two synovial joints formed by facets on the upper and lower border of each laminae Ligamentum flavum → elastic qualities, allowing it deform and return to its original length In the neutral position, under constant tension, imposing continual tension on the disc Trunk flexion occurs primarily in the lumbar vertebrae first 50 to 60° moved into more flexion by forward tilt of the pelvis Extension first the pelvis tilts posteriorly Flexion begins placing compressive force on the anterior portion of the disc 4 Ligaments and annulus fibers absorb the compressive forces Lateral flexion range of motion is about 75-85° mainly in the cervical and lumbar regions Cervical Region Rotation is limited in the lumbar region C1, C2→ no vertebral body, shaped like a ring C2→large transverse processes with transverse foramen which blood supply travels C1, No spinous process, hold the occiput of the skull Atlanto-occipital joint Head nods, allows free sagittal plane movements 10 to 15° of flexion /extension, 8° of lateral flexion, no rotation Atlantoaxial joint the most mobile of the cervical joints, 10° of flexion/extension, 47° of rotation, no lateral flexion 5 Transverse process of the cervical vertebera →Foramen where the arteries pass through, this is not found in other regions Difference between the C-T-L Cervical discs, thicker ventrally than dorsally producing a wedge shape and contributing to the lordotic curvature in the cervical region Short spinous processes Maximum rotation C1-C2 maximum lateral flexion C2-C4 maximum flexion/extension at C1-C3 and C7-T1 6 Thoracic Region The most restricted regions bodies become taller, longer pedicles, transverse processes are long, angle backward On the back, long spinous processes overlapping, directed downward Flexion/extension combined is 3 to 12°, very limited motion in the upper thoracic(2-4°) increases in the lower thoracic to 20° at the thoracolumbar junction Lateral flexion is limited, ranging from 2 to 9° Upper T, lateral flexion is limited to 2 to 4° Lower T it may be as high as 9° Lumbar region Large lumbar vertebra most highly loaded structure, pedicles are short, spinous processes broad, small transverse processes Gender differences and different disc heights at different levels of the vertebrae→higher in ♂ ,highest disc height is found at L4-L5 and L5-S1 Apophyseal joints→ 60° to the transverse plane 20° to the frontal plane Movements limited primarily by he connection with the ribs orientation of the facets long spinous processes that overlap in the back Rotation from 2 to 9° Disc injuries is not common Flexion/extension 8 to 20° lateral flexion from 3 to 6° very little rotation(1 to 2°)at all levels of the lumbar vertebrae Lumbosacral joint is the most mobile Flexion/extension→75% 20% at L4-L5 5% at the other 7 Combined Movements Of The Pelvis And Trunk MUSCULAR ACTIONS Lumbar flatten Trunk extension is an important movement raise the trunk and to maintain an upright posture Anterior tilt of the pelvis Trunk Extension Spinal extensors 1. erector spinae (iliocostalis, longissimus, spinalis) 2.deep posterior, paravertebral, muscles (intertransversarii, interspinales, rotators, multifidus) Trunk Flexion Consist of 4 muscles 1. the rectus abdominus 2. the internal oblique 3. the external oblique 4. the transverse abdominus 8 Increase intra-abdominal pressure when contract decrease the compressive force on the spine reduces the activity of the erector spinae muscles Transverse abdominus plays a greater role →↑ intra-abdominal pressure than the obliques Trunk Lateral Flexion Most activity in lateral flexion →lumbar erector spinae muscles deep→ intertransversarii and interspinales muscles on the contralateral side STRENGTH AND FORCES AT THE VERTEBRAL JOINTS Greatest strength output in the trunk extension → averaging values of 210 Nm for males Quardratus lumborum → form lateral wall of the abdomen and runs from the iliac crest to the last rib maintaining pelvic position on the swing side in gait. Trunk Rotation More complicated Trunk flexion strength was 150 Nm, or approximately 70% of the strength of the extensors Lateral flexion was 145 Nm, or 69% of the extensor strength rotation was 90 Nm 43% of the extensor strength Female→ approximately 60% recorded for males 9 Discs, apophyseal joints and intervertebral ligaments → load-bearing structures Compressive forces are perpendicular to the disc Lumbar vertebrae handle the largest load → because positioning, center of mass relative to the lumbar region and greater body weight acting at the lumbar region Loads Acting on the Vertebrae Loads produced by body weight muscular force acting on each motion segment prestress forces due to the disc and ligament forces Muscle forces protect the spine from excessive bending and torsion subject the spine to high compressive forces Axial load in standing is 700N Lumbar spine can resist approximately 9800N of vertical load before fracturing Various postures and Exercises Shearing force across LS joint is 50% BW Sacral °↑50 °, Shearing force ↑75% BW 10 Loading on Lumbar POSTURE 1470 N 1176 N Unsupported sitting position more load than standing 686 N 1715 N 1764 N because a backward tilt, a flattening of the low back and forward shift in the center of gravity 1813 N Sitting long→ ↑the resting length of the erector spinae muscles and overstretch the posterior ligamentous structures Continuous flexion cause of both lumbar and cervical flexion injuries in the workplace C- or S-shaped depending on the direction and the beginning and ending segments Postural Deviations Rounded-shoulder may cause thoracic kyphosis associated with osteoporosis other disorders Exaggerated lumbar curve →Lumbar lordosis or hyperlordosis most serious postural disorders → scoliosis CONDITIONING The cause of scoliosis is unknown, ♀>♂ Force production→ Low back is a common site of injury in sports and in the workplace, special attention should be given to exercises strengthen and stretch trunk exercises should evaluated for negative impact on trunk function and structure 11 Ball exercise Excessive lordosis, hyperextension of the lumbar should be avoided, pay attention to its risks CONTRIBUTION OF TRUNK MUSCLES TO SPORTS SKILLS OR MOVEMENTS 12 Lumbar muscles serve to restrict locomotion →controlling lateral flexion/the forward flexion of the trunk Cervical muscles serve to maintain the head in an erect position on the trunk INJURY POTENTIAL IN THE TRUNK Back sprain accounts for only 2 to 3% of the total sprains in the athletic population in sports→ require high levels of bending and rotation, such as golf, gymnastics, and baseball Compression on the spinal cord or nerve roots from an intervertebral disc protrusion or disc prolapse speed of walking↑,corresponding ↑ in lumbar range of motion One difference → in walking trunk extension at touchdown → in running trunk will be flexed at touchdown only at fast speeds At slower speeds, the trunk will be extended at touchdown. The incidence of injury is very high, 60 to 80% will have back pain at some time in their lives Low-back pain is most common→ age range of 25 to 60 uncommon in children and athletes Disc protrusions→ most frequently at C5-C6, C6-C7, L4-L5, and L5-S1 13 Disc protrusion impinge nerve Significant amount of torsion, or rotation, of the trunk has been shown to tear fibers in the annulus fibrosus of the disc Pure compression to the spine usually injures the vertebral bodies and end plates rather than the disc Disc degeneration Fatigue fracture 椎弓解離 脊椎滑脫 Most common in repeated flexion, extension and rotation 20.7% incidence of spondylolysis in athletes Spondylolysis on both sides, spondylolisthesis can develop In cervical region, whiplash injury are common Rapidly flexed, straining the postreior ligaments even dislocation In thoracic region, is not injured as frequency as C and L region Stabilization and limitated as a result of interface with the ribs In lumbar region, is the most injured →myofascial pain, muscle spasm, irritation of the joints, disc prolapse, sciatic, low-back pain.. whiplash injury 14 Effect of Aging on The Trunk flexibility↓ Loss of strength in the trunk muscle of approximately 1% per year Disc, small fluid, place more stress on the annulus fibrosus Mobility ↓ in segments ↓loading imposed on the low back 15