14-01-05 Anatomy & Biomechanics Prepared by Michael Boni, PT, CAT(C), ATC, FCAMPT, CAFCI Boni ConsulAng Inc. The FuncAonal Pelvis • Supports & protects pelvic viscera • Supports lumbar spine (key stone) • Muscle & ligament aachment • Dynamic link b/w the spine and lower limbs • Reduces & absorbs torsional stress in gait by allowing gliding movements at SIJ & SP ‘The Sacred Bone’ Keystone of the pelvis Highly variable triangular wedged b/w innominates 1 14-01-05 Superior ArAcular Process Spinal Canal Sacral Ala Vertebral Body Sacral Promontory 2 ARTICULAR SURFACES Short Arm Long At S1 in C-C Arm plane At S2-3 in AP plane INNOMINATE Pubis • Forms the Inf/Med aspect Ishium • Forms the Inf/Lat 1/3 of the innominate • Ischial tuberosity site of strong mm & lig aachment 2 14-01-05 INNOMINATE Ilium • Fan like structure • SI arAcular surface is on the Post/Sup aspect • L-shaped arAcular surface • Surface is covered with grooves and ridges Sacroiliac Joint • Synovial joint • Sacral surface has hyaline carAlage • Ilium has fibrocarAlage • Capsule has 2 layers – outer fibrous layer – inner synovial layer • Capsule blends with deep interosseus lig post and periosteum inferiorly • Supported by lig & fascia LIGAMENTS 1. I.L ligament Sup fibres 1 2. I.L verCcal 2 fibres 3 3. Ventral S.I 4. Sacrotuberous 4 5. Inguinal 6 5 6. Sacrospinous 7. Superior Pubic 7 3 14-01-05 SI Ligaments Ventral SI Ligament • Weakest • Thickening of ant/inf parts of the joint capsule SI Ligaments Interosseous SI Lig • Very thick and strong • Fibres are mulAdirecAonal • Completely fills the space b/w the lateral sacral crest and the iliac tuberosity • Deep and superficial layers • Tightens with sacral nutaon SI Ligaments Long Dorsal Lig • AJaches to deep TDF, erector spinae apponeurosis, mulfidus and sacrotuberous lig • FuncAonal link b/w legs, spine, upper quadrant • ContracAon of lat dorsi and glut max muscles reduce tension (Vleeming 1997) • ContracAon of erector spinae & loading of the sacrotuberous lig will increase tension in the ligament (Vleeming 1997) • Source of pain in 88% of people with unilateral pelvic pain (Vleeming 1998) • Tightens with sacral counternutaon (Vleeming 1996) 4 14-01-05 SI Ligaments • AJaches to glut max. Sacrotuberous Lig biceps femoris, and deep MF 3 Bands Lateral – ischial tuberosity to PSIS, spans piriformis Medial – S3,4,5 , lower sacrum & coccyx, to IT Superior – connects coccyx & PSIS • Pierced by S2,3 cutaneous nn. • Tightens with sacral nutaon • AJaches medially to sacrum and coccyx, laterally to ischial spine • Blends with SIJ, thin and triangular • May be responsible for coccydinia, ? A degenerated part of coccygeus mm Iliolumbar Lig • Connects L4-L5 TP to ilium • Coronal and sagiJal stability of lumbosacral juncAon • Highly variable in number and form • Muscle to 3rd decade (post band = iliocostalis lumborum, ant = QL) • Calcifies aer 6th decade • Blends with QL, ventral SIJ, TLF (a) • 5 Bands 5 14-01-05 Sacral Ligaments Limits Nutaon Limits • Interosseous S.I lig Counternutaion • Sacrotuberous lig • Long Dorsal SI Lig • TDF: important in load transfer from trunk to LE • AJachments to TA, IO, G. max/med, LD, ES, MF, BF • Anterior :(thin, from QL to Lx TPs), • Middle: (Lx TPs to aponeurosis of TA), • Posterior: covers back mm, Lx SPs laterally to form lateral raphe with other facial layers Pubic Symphysis • Has a fibrocarAlaginous disk • Osseous surfaces covered by thin hyaline carAlage • Superior pubic lig • Inferior arcuate lig blends with the disk • Anterior / posterior pubic lig - ant blends with abdominals & adductor longus • EssenAal for pelvis stability 6 14-01-05 Sacrococcygeal Joint • Classified as symphysis but synovial joints found Ligaments: • Ventral / Dorsal / Lateral sacrococcygeal ligaments Myology 35 muscles aach to sacrum & innominate • Obturators • Hip adductors • Tensor Fascia Lata • Rectus femoris • Quadratus lumborum • Abdominals • Lassimus dorsi • Hamstrings Myology Muscle aaching directly to sacrum • Erector spinae • MulAfidus • Gluteals • Piriformis • Perineals • Gemelli • iliacus 7 14-01-05 Transversus Abdominis Anterior View: n Lower 6 costal carAlages, TLF, lateral inguinal lig., anterior iliac crest running transversely to linea alba and pubis n With MF, diaphragm & pelvic floor, it supports & propriocepve control for lumbo-pelvic area n Supports pelvic and abdominal contents Transversus Abdominis Posterolateral view n Fascial aachments n Acts to sAffen the spine through TLF n Acve in feed forward manner Sacroiliac Compression TA increases SIJ stability 8 14-01-05 MulAfidus Superficial Fibers Maintenance of lumbar lordosis Diaphragm Tonic acAon (never turns off) • turns on before limb movements (~TA) Contributes to spinal control by assisAng with: • pressurizaon and control of displacement of the abdominal contents Therefore • allows TA to increase tension in the TLF & generate IAP • helps to increase rigidity of the spine Pelvic Floor Levator ani muscle 1. Puborectalis 2. Pubococcygeus 3. Iliococcygeus • Ischiococcygeus 3 2 1 9 14-01-05 Pelvic Floor Pubococcygeus § From post. pubis and fascia of obturator internus to midline raphe § Laterally compresses the visceral canals § Minimal influence on SIJ § AcAvates with TA to compress symphysis pubis Pelvic Floor Puborectalis § Posterior symphysis, uniAng with other side around back of rectum § Blends with Pubococcygeus § Tightens external anal sphincter to aid in voluntary retenAon of feces § FuncAons with RA Pelvic Floor Ischio / Iliococcygeus § From ischial spine, sacrospinous ligament and fascia of obturator internus to S3 & coccyx § Same plane as piriformis § Pull coccyx forward following defecaon § Sacral counternutaon § Early research shows that they funcAon with oblique abdominals 10 14-01-05 Pelvic Floor Funcon • Supports pelvic viscera/abdominal contents • Assists with closure of visceral openings • ContracAon facilitates TA acAvity • Force couple with mulfidus to control the posiAon of the sacrum • Ilio / Ischiococcygeus counternutate the sacrum – Avoid by peri-urethral vs. peri-anal contracAon • Achieve a beJer contracAon of pelvic floor / TA, in neutral ASIS, or slight anterior Alt ArAcular Neurology • ArAcular neurology has both direct and reflex influences on muscle tone locally and globally • ArAcular afferent input contributes to percepAon of posture and moAon • dorsal SI ligaments supplied by lateral divisions of the dorsal rami of L5, S1, S2, & S3 spinal nerves • Pubic Symphysis innervated by pudendal & genitofemoral nerves ArAcular Neurology • Joint mechanoreceptors help to coordinate joint posiAon, mobility, and stability to improve biomechanical efficiency • Central effects include: reflex, perceptual, and pain suppression 11 14-01-05 Anterior Neurology • Innervaon variable– branches of the ventral rami L5-S3 Posterior • Lateral divisions of dorsal rami of L5-S3 • Variety of pain paerns with SI dysfuncAon • Pain referred to buJocks, groin, and lower quadrant but not usually below the knee • Pelvic girdle muscles supplied efferently via the spinal nerve roots from T12-S4 Blood Supply 1. Median sacral artery supplies sacrum coccyx & rectum 2. Internal iliac artery gives off the lateral sacral 1 artery which 2 anastomose with the median sacral artery They will supply the cauda equina and sacrum Later join with the post. gluteal arteries PELVIS BIOMECHANICS 12 14-01-05 The SIJ’s do move! 1. Flexion/extension in sagiJal plane on forward/ backward bending 2. Sideflexion in coronal plane in sidebending 3. Axial rotaon in coronal transverse plane during twisAng of trunk 4. A combinaon of all moAons occurs during gait. Studies by Sturesson and Jacob and Kissling found 2.5° of innominate rotaon and 0.5-1.6mm of translaon Kinemacs of Lumbo-Pelvic Region Flexion coupled with PA translaon about a dynamic coronal axis, with 1-3mm of anterior translaon. • Inferior arAcular processes of superior vertebra (L5) glide superiorly and anteriorly Sideflexion coupled with ipsilateral rotaon and mediolateral translaon. • Ipsilateral inferior arAcular process of superior vertebra (L5) glides inferiorly and posterior Extension coupled with AP translaon. • Inferior arAcular processes of the superior vertebra (L5) glide inferiorly and posteriorly Osteokinemacs of SIJ Work through moAon of innominate, sacrum and L5, relave to each other in: • Trunk flexion • Trunk extension • Trunk sideflexion • Trunk rotaon • Standing hip flexion 13 14-01-05 Osteokinemacs of SIJ Trunk Flexion • Innominate – Flexion relave to femur – Posteriorly rotated relave to sacrum • Sacrum – Remains nutated relave to innominate • L5 – Flexes and translates anterior on the sacrum (confirmed by research) Osteokinemacs of SIJ Trunk Extension • Innominate – extension relave to femur – Posteriorly rotated relave to sacrum • Sacrum – Remains nutated relave to innominate • L5 – Extends and translates posterior on the sacrum (confirmed by research) Osteokinemacs of SIJ Trunk Right Side Flexion • Innominate – Right innominate anterior rotaon – Lej innominate posterior rotaon – Lej translaon • Sacrum – Sacral base rotates lej (right sacral base nutated) • L5 – Right side flexes and rotates ??? (clinical hypothesis) 14 14-01-05 Osteokinemacs of SIJ Trunk Right RotaCon • Innominate – Right innominate posteriorly rotates – Lej innominate anteriorly rotates • Sacrum – Sacral base rotates right • L5 – Rotates right, conjunct rotaon ???? (clinical hypothesis) Osteokinemacs of SIJ Right Hip Flexion • Innominate – Right innominate posteriorly rotates relave to sacrum – The right PSIS moves down – Femur flexes relave to innominate