6 biomechanics of vertebral column regional - sacral


Published on

  • Be the first to comment

  • Be the first to like this

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

6 biomechanics of vertebral column regional - sacral

  1. 1. 6.Biomechanics ofVertebral Column: Regional Structure & Function-Sacral RegionDr. D. N. BidSarvajanik College of Physiotherapy,Rampura, Surat – 395003.
  2. 2. Structure of the Sacral Region• Five sacral vertebrae are fused to form thetriangular or wedge-shaped structure that iscalled the sacrum.• The base of the triangle, which is formed by thefirst sacral vertebra, supports two articular facetsthat face posteriorly for articulation with theinferior facets of the fifth lumbar vertebra.• The apex of the triangle, formed by the fifthsacral vertebra, articulates with the coccyx.6/14/2013 dnbid71@gmail.com 2
  3. 3. • Sacroiliac Articulations• The two SIJs consist of the articulations betweenthe left and right articular surfaces on the sacrum(which are formed by fused portions of the first,second, and third sacral segments) and the leftand right iliac bones (Fig. 4-47).• The SIJs are unique in that both the structure andfunction of these joints change significantly frombirth through adulthood.6/14/2013 dnbid71@gmail.com 3
  4. 4. 6/14/2013 dnbid71@gmail.com 4
  5. 5. • Articulating Surfaces on the Sacrum• The articulating surfaces on the sacrum are auricular(C)-shaped 90 and are located on the sides of the fusedsacral vertebrae lateral to the sacral foramina.• The fetal and prepubertal surfaces are flat andsmooth, whereas the postpubertal surfaces are markedby a central groove or surface depression that extendsthe length of the articulating surfaces.• The articular surfaces are covered with hyalinecartilage. The overall mean thickness of the sacralcartilage is greater than that of the iliac cartilage.6/14/2013 dnbid71@gmail.com 5
  6. 6. • Articulating Surfaces on the Ilia• The articular surfaces on the ilia are also C-shaped.• In the first decade of life, the iliac joint surfaces aresmooth and flat and covered with fibrocartilage.• The type of cartilage covering the iliac articularsurfaces in the adult continues to be a matter ofdebate.• The cartilage is different in gross appearance and isthinner than the sacral articular cartilage. It was usuallydescribed as fibrocartilage.6/14/2013 dnbid71@gmail.com 6
  7. 7. • However, type II collagen, which is typical ofhyaline cartilage, has been identified in the iliaccartilage, and the iliac cartilage is described in the38th edition of Gray’s Anatomy as being hyalinecartilage.• After puberty, the joint surfaces develop a centralridge that extends the length of the articulatingsurface and corresponds to the grooves on thesacral articulating surfaces.6/14/2013 dnbid71@gmail.com 7
  8. 8. • Ligaments• The anterior, interosseous, and posterior sacroiliacligaments are directly associated with the SIJs. A separateportion of the posterior sacroiliac ligament is called eitherthe long posterior sacroiliac ligament or the long dorsalsacroiliac ligament.• The iliolumbar ligaments, which connect the fifth lumbarvertebra to the sacrum and the sacrospinous ligaments,and the sacrotuberous ligaments, which connect thesacrum to the ischium, are indirectly associated with theSIJs (Fig. 4-48).• The iliolumbar ligaments were described previously in thelumbar region.6/14/2013 dnbid71@gmail.com 8
  9. 9. • Sacroiliac Ligaments• The sacroiliac ligaments as a whole extend from theiliac crests to attach to the tubercles of the first foursacral vertebrae.• The sacroiliac ligaments, which are reinforced byfibrous expansions from the quadratus lumborum,erector spinae, gluteus maximus, gluteus minimus,piriformis, and iliacus muscles, contribute to the joint’sstability.• The fascial support is greater posteriorly thananteriorly because more muscles are locatedposteriorly.6/14/2013 dnbid71@gmail.com 9
  10. 10. 6/14/2013 dnbid71@gmail.com 10
  11. 11. • The anterior sacroiliac ligaments areconsidered by Gray’s Anatomy to be capsularligaments because of the ligaments’ intimateconnections to the anteroinferior margins ofthe joint capsules.• According to Bogduk, the anterior sacroiliacligaments cover the anterior aspects of theSIJs and join the ilia to the sacrum.6/14/2013 dnbid71@gmail.com 11
  12. 12. • The interosseous sacroiliac ligaments, which constitute themajor bonds between the sacrum and the ilia, areconsidered to be the most important ligaments directlyassociated with the SIJs.• The ligaments are composed of superficial and deepportions, which are divided into superior and inferiorbands. The superficial bands unite the superior articularprocesses and lateral crests of the first two sacral segmentsto the ilia.• This portion of the interosseous ligament is referred to asthe short posterior sacroiliac ligament.6/14/2013 dnbid71@gmail.com 12
  13. 13. • The deeper portions of the interosseoussacroiliac ligament extend from depressionsposterior to the sacral articular surface todepressions on the iliac tuberosities.• The posterior sacroiliac ligaments connect thelateral sacral crests to the posterior superioriliac spines and iliac crests.6/14/2013 dnbid71@gmail.com 13
  14. 14. • The paired long dorsal sacroiliac ligaments havesuperior attachments to the posterior superiorsacroiliac spines (PSISs) and adjacent parts of the ilium.• Inferiorly, the ligaments are attached to the lateralcrest of the third and fourth sacral segments.• The medial fibers are connected to the deep lamina ofthe posterior layer of the thoracolumbar fascia and theaponeurosis of the erector spinae (ESA).6/14/2013 dnbid71@gmail.com 14
  15. 15. • The sacrospinous ligaments connect the ischial spinesto the lateral borders of the sacrum and coccyx.• The sacrotuberousligaments connect the ischialtuberosities to the posterior spines at the ilia and thelateral sacrum and coccyx.• The sacrospinous ligament forms the inferior border ofthe greater sciatic notch; the sacrotuberous ligamentforms the inferior border of the lesser sciatic notch.6/14/2013 dnbid71@gmail.com 15
  16. 16. Symphysis Pubis Articulation• The symphysis pubis is a cartilaginous joint locatedbetween the two ends of the pubic bones.• The end of each pubic bone is covered with a layer ofarticular cartilage and the joint is formed by afibrocartilaginous disk that joins the hyaline cartilage-covered ends of the bones.• The disk has a thin central cleft, which in women mayextend throughout the length of the disk.• The three ligaments that are associated with the joint arethe superior pubic ligament, the inferior pubic ligament,and the posterior ligament.6/14/2013 dnbid71@gmail.com 16
  17. 17. • The superior ligament is a thick and dense fibrous bandthat attaches to the pubic crests and tubercles andhelps support the superior aspect of the joint.• The inferior ligament arches from the inferior rami onone side of the joint to the inferior portion of the ramion the other side and thus reinforces the inferioraspect of the joint.• The posterior ligament consists of a fibrous membranethat is continuous with the periosteum of the pubicbones.6/14/2013 dnbid71@gmail.com 17
  18. 18. • The anterior portion of the joint is reinforcedby aponeurotic expansions from a number ofmuscles that cross the joint (Fig. 4-49).• Kapandji described the muscle expansions asforming an anterior ligament consisting ofexpansions of the transversusabdominis, rectus abdominis, internalobliquus abdominis, and adductor longus.6/14/2013 dnbid71@gmail.com 18
  19. 19. 6/14/2013 dnbid71@gmail.com 19
  20. 20. 6/14/2013 dnbid71@gmail.com 20
  21. 21. Function of the Sacral Region• Kinematics• The SIJs permit a small amount of motion that varies amongindividuals.• Both the amount and type of motion available at these jointshas been and continues to be a matter of controversy.• At most, it appears as if the motion available is very slightand not easily defined.• The SIJs are linked to the symphysis pubis in a closedkinematic chain, and therefore any motion occurring at thesymphysis pubis is accompanied by motion at the SIJs andvice versa.6/14/2013 dnbid71@gmail.com 21
  22. 22. • The smooth SIJ surfaces in early childhood permitgliding motions in all directions, which is typical of asynovial plane joint.• However, after puberty, the joint surfaces change theirconfiguration and, according to Walker, motion in theadult is restricted to a very few millimeters oftranslation and or rotation.• However, a considerable amount of controversy existswith regard to both the type and amount of motionavailable at the SIJs.6/14/2013 dnbid71@gmail.com 22
  23. 23. • Nutation is the term commonly used to refer to movementof the sacral promontory of the sacrum anteriorly andinferiorly while the coccyx moves posteriorly in relation tothe ilium (Fig. 4-50A).• Counternutation refers to the opposite movement, inwhich the anterior tip of the sacral promontory movesposteriorly and superiorly while the coccyx movesanteriorly in relation to the ilium (see Fig. 4-50B).• The change in position of the sacrum during nutation andcounternutation affects the diameter of the pelvic brim andpelvic outlet.6/14/2013 dnbid71@gmail.com 23
  24. 24. • During nutation, the anteroposterior diameter ofthe pelvic brim is reduced and theanteroposterior diameter of the pelvic outlet isincreased.• During counternutation, the reverse situationoccurs.• The anteroposterior diameter of the pelvic brimis increased, and the diameter of the pelvic outletis decreased.6/14/2013 dnbid71@gmail.com 24
  25. 25. • These changes in diameter are of particular importanceduring pregnancy and childbirth, and it is possible thatthe most motion that occurs at the SIJs may occur inpregnancy and childbirth, when the joint structures areunder hormonal influence and ligamentous structuresare softened.• Accurate descriptions of the SIJs and the motions thatoccur at these joints have been difficult to obtainbecause the planes of the joint surfaces are oblique tothe angle of an x-ray beam used to make a standardanteroposterior radiograph of the pelvis.6/14/2013 dnbid71@gmail.com 25
  26. 26. 6/14/2013 dnbid71@gmail.com 26
  27. 27. • During pregnancy, relaxin,a polypeptide hormone isproduced by the corpus luteum and decidua.• This hormone is thought to activate the collagenolyticsystem, which regulates new collagen formation andalters the ground substance by decreasing the viscosityand increasing the water content.• The action of relaxin is to decrease the intrinsicstrength and rigidity of collagen and is thought to beresponsible for the softening of the ligamentssupporting the SIJs and the symphysis pubis.6/14/2013 dnbid71@gmail.com 27
  28. 28. • Consequently, the joints become more mobileand less stable, and the likelihood of injury tothese joints is increased.• The combination of loosened posteriorligaments and an anterior weight shift causedby a heavy uterus may allow excessivemovement of the ilia on the sacrum and resultin stretching of the SIJ capsules.6/14/2013 dnbid71@gmail.com 28
  29. 29. • The SIJs and symphysis pubis are closely linkedfunctionally to the hip and joints and thereforeaffect and are affected by movements of thetrunk and lower extremities.• For example, weight shifting from one leg toanother is accompanied by motion at the SIJs.• Fusions of the lower lumbar vertebrae have beenfound to cause compensatory increases in motionat the SIJs.6/14/2013 dnbid71@gmail.com 29
  30. 30. • The joints of the pelvis are linked to the hip and vertebralcolumn in non–weight-bearing as well as in weight-bearingpostures.• Hip flexion in a supine position tilts the ilia posteriorly inrelation to sacrum.• This pelvic motion causes nutation at the SIJs, whichincreases the diameter of the pelvic outlet.• During the process of birth, the increase in the diameter ofthe pelvic outlet facilitates delivery of the fetal head.6/14/2013 dnbid71@gmail.com 30
  31. 31. • Counternutation is brought about by hipextension in the supine position and enlargesthe pelvic brim.• Therefore, a hip-extended position is favoredearly in the birthing process to facilitate thedescent of the fetal head into the pelvis,whereas the hip-flexed position is used duringdelivery.6/14/2013 dnbid71@gmail.com 31
  32. 32. • Kinetics• Stability of the SIJs is extremely importantbecause these joints must support a large portionof the body weight.• In normal erect posture, the weight of head,arms, and trunk (HAT) is transmitted through thefifth lumbar vertebra and lumbosacral disk to thefirst sacral segment.• The force of the body weight creates a nutationtorque on the sacrum.6/14/2013 dnbid71@gmail.com 32
  33. 33. • Concomitantly, the ground reaction forcecreates a posterior torsion on the ilia.• The counter-torques of nutation andcounternutation of the sacrum and posteriortorsion of the ilia are prevented by theligamentous tension and fibrous expansionsfrom adjacent muscles that reinforce the jointcapsules and blend with the ligaments.6/14/2013 dnbid71@gmail.com 33
  34. 34. • In one study, Pool-Goudzwaard and colleaguesinvestigated the role that the iliolumbarligaments played in stabilizing the SIJs.• These authors demonstrated that the ililolumbarligaments have a significant role in stabilizing theSIJ as well as the lumbosacral junction.• The ventral band of the iliolumbar ligament is ofparticular importance in restricting sagittal planeSIJ mobility.6/14/2013 dnbid71@gmail.com 34
  35. 35. • Also, tension developed in the sacrotuberous,sacrospinous, and anterior sacroiliac ligamentscounteracts the nutation of the sacrum, although thesacrotuberous and sacrospinous ligaments have notbeen found to play a major role in pelvic stability.• However, the sacrotuberous and interosseousligaments compress the SIJ during nutation.• The long dorsal sacroiliac ligament is under tension incounternutation and relaxed in nutation.• The interosseous sacroiliac ligament binds the ilia tothe sacrum.6/14/2013 dnbid71@gmail.com 35
  36. 36. • Surface irregularities and texture of the SIJs alsocontribute to stability of the joint in the adult.• In a study of SIJs, the highest coefficients offriction were found in sample joints with ridges,depressions, and coarse-textured cartilage.• Sample joints with ridges, depressions, andsmooth cartilage showed higher coefficients offriction than did samples without ridges anddepressions.6/14/2013 dnbid71@gmail.com 36
  37. 37. • These findings suggest that thecomplementary ridges and depressions as wellas the coarse surface textures found in theadult reflect a dynamic, normal developmentof the SIJs.• Vertical load-bearing is facilitated by thesechanges, but motion is limited by the changes.6/14/2013 dnbid71@gmail.com 37
  38. 38. • Shearing forces are created at the symphysis pubisduring the single-leg-support phase of walking, as aresult of lateral pelvic tilting.• In a normal situation, the joint is capable of resistingthe shearing forces, and no appreciable motion occurs.• If, however, the joint is dislocated, the pelvis becomesunstable during gait, with increased stress on thesacroiliac and hip joints as well as the vertebralcolumn.6/14/2013 dnbid71@gmail.com 38
  39. 39. Thank you……..,,,End of Part - 66/14/2013 dnbid71@gmail.com 39