The Trunk/Spine

1. 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

2. 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

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

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

5. Body Transverse process Vertebral foraman Spinous process Intervertebral foraman

6. Muscular Attachments • muscular attachments on spinous and transverse processes

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

8. Further depiction of vertebral shapes

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

10. 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

11. Shock Absorbers Bending Loads

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

13. 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

14. 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

15. 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

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

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

18. Regional ROM in Spine Atlas (C1) & axis (C2) account for 50% of rotation in the cervical region. Thoracic region is restricted, mainly due to connection to ribs.

19. Spine - Posterior Muscular Supportprimarily produce extension and medial/lateral flexion • Superficial to deep • erector spinae • semispinalis • deep posterior

20. Spine - Posterior Muscular Supportprimarily produce extension and medial/lateral flexion • Posteriorly • erector spinae iliocostalis longissumus thoracis spinalis

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

22. Semispinalis capitis cervicis thoracis

23. IT IS intertransversarius interspinales Deep posterior multifidus rotatores

24. rectus abdominis Abdominals transverse abdominus external oblique internal oblique

25. 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

26. 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

27. 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

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

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

30. 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)

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

32. 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

33. 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

34. 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)

35. TW Tm Consequences of Pelvic Tilt • in normal standing the line of gravity passes ventral (anterior) to the center of the 4th lumbar vertebral body • This creates a forward bending torque which must be counter-balanced 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

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

37. 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

38. 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

39. 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.

40. Pelvic Tilt and Sitting vs. • 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

41. L3 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

42. 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

43. Spinal Injuries

44. Progression of Disc Degeneration

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

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

48. Tearing of Annulus Disk Herniation