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Functional Anatomy and Biomechanics of the Lumbar Spine
McMinn RMH. Hutchings RT. Color Atlas of Human Anatomy 1985
Level 3 – Lower Quadrant Lenerdene Levesque BScPT, MClSc, FCAMPT
Typical Lumbar Vertebra
Primal Pictures Ltd. Interactive Spine 2010
Vertebral Body
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
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Vertebral Foramen
Primal Pictures Ltd. Rohen JW. Yokochi C Color Atlas of Anatomy 1988 Interactive Spine 2010
Lumbar Stenosis
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Posterior Elements
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
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Pars Interarticularis
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Lumbar Facets
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Zygapophyseal Joints
Superior articular process Ligamentum flavum
Inferior articular process
Posterior fibrous Multifidus capsule Taylor J.R.
Rohen JW. Yokochi C Color Atlas of Anatomy 1988
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Zygapophyseal Joints
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Orientation of Articular Facets
§ J or C shaped § curved or biplanar in the in the transverse plane § larger posterior part – sagittal plane § anterior part – coronal plane
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Functions of the Zygapophyseal Joints
§ Guide rails for sagittal & coronal plane movement § Restrain axial rotation and excessive translation § Protect disc from torsional and shearing strains
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How the facet orientation protects the lumbar disc
How the facet orientation protects the lumbar disc
Joint Angles
§ Angle formed by the SAP with the median plane shows an increase from L1-S1
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
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Which vertebral body is this?
McMinn RMH. Hutchings RT. Color Atlas of Human Anatomy 1985
Joint Tropism
§ Bilateral asymmetry is common § Most frequent at the lower 2 levels § 23% in asymptomatic individuals
Z Joint - Capsule
anterior capsule is formed by ligamentum flavum multifidus attaches to the posterior aspect of the capsule
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
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Intra-articular Structures
§ fat pads
§ connective tissue § adipose pad § fibro-adipose meniscoid Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Intra-articular Structures
Synovial fold
Taylor J.R.
Fat Pads
Enlarged fat pads may extend through mid joint of unstable segments.
Taylor J.R. L4-5 facet from an unstable segment in a 43 year old man
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Enlarged joint inclusions and capsular laxity
LF torn away from normal attachment
Posterior inclusion
Taylor J.R.
Lumbar Facet Joint
Subchondral bone
AC
Taylor J.R. The articular cartilages are supported by plates of compact subchondral bone – thickest in the anterior coronally oriented part.
Age Changes in Lumbar Facet Joints
§ Chondromalacia: in young adults in response to compressive loading in anterior (coronal) part of superior articular process (SAP)
§ Bony hypertrophy of facets: thickening & sclerosis in anterior coronal part of subchondral bone plate of superior articular process Increased size of facets with marginal osteophytes
§ Osteoarthrosis with cartilage loss
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Age Related Changes
thickened bone plate
chondromalacia
Taylor J.R. Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Age Related Changes
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Taylor J.R. Edition 1997 Cartilage loss in middle and later life affects the posterior part of the joint
LUMBAR FACET JOINT INJURIES
§ Soft tissue injury with heamarthrosis § Articular surface micro-fracture + haemarthrosis § Central vertical fracture to sup. articular process § Mamillary process fracture
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Facet Fractures
Central fracture through the SAP
Taylor J.R.
Undisplaced fracture
Fracture of the subchondral bone plate and articular cartilage with local haemorrhage
53F (MVA)
Taylor J.R.
Injury to the central articular cartilage in an 18 year old man
Taylor J.R.
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LUMBAR FACETS: Soft Tissue Injuries
Capsular tears Ligamentum flavum tears Articular cartilage (AC) separation AC “fracture” + haemarthrosis
Capsular Tear
Taylor J.R. Posterior fibrous capsule where it attaches to the posterior articular cartilage
Ligaments
McMinn RMH. Hutchings RT. Color Atlas of Human Anatomy 1985
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Major Ligaments
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Ligaments
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Ligamentum Flavum
Primal Pictures Ltd. Bogduk N. Clinical Anatomy of the Lumbar Interactive Spine 2010 Spine and Sacrum 3rd Edition 1997
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Iliolumbar Ligament
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Intervertebral Foramen
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Lumbar Spine Innervation
§ Pain Sensitive § Not Innervated § Outer 1/3rd annulus § Nucleus pulposus § Longitudinal ligaments § Articular cartilages § Facet posterior § Ligamentum flavum capsule and synovial
folds § Subchondral bone and vertebral periosteum § Anterior dura mater § ? Internal structure of the vertebra
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Innervation of the Z Joints
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Innervation
Direct supply from ventral ramus Dual innervation from medial branches from rami communicantes branches of the dorsal rami
Taylor J.R. Taylor J.R.
Intervertebral Disc
Annulus Fibrosus Nucleus Pulposus Vertebral End Plate
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
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Sagittal section of L3-4 adult disc
Cartilage Plate
NP AF
Taylor J.R.
Functions of the Nucleus
1. Fluidity permits formation of the mobile segment 2. Disperses pressure – allows even distribution of compression forces 3. Viscid gel – contributing to a dynamic hydraulic suspension system
Annulus Fibrosus
Outer annular lamellae ligamentous § unite vertebral rims & resist tensile forces. § low proteoglycan (PG) content
Inner annular lamellae cartilaginous Taylor J.R. § load-bearing role § high PG content
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Annulus
Bullough PG, O.Boachie-Adjei. Atlas of Spinal Diseases 1988
Functions of the Annulus
1. Chief structural unit between the vertebral bodies 2. Retains the nucleus 3. Restricts and regulates movement 4. Absorbs the shock of
compression forces Primal Pictures Ltd. Interactive Spine 2010
Vertebral End Plate
NP
Cartilage plate
Vertebral body
Taylor J.R.
§ Hyaline cartilage, 1mm thick § Attached to vertebral body by thin calcified layer, which is penetrated by small vascular buds § Pathway for diffusion of nutrients to disc § Barrier between avascular proteoglycan rich nucleus and vascular spongiosa of vertebra
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Function of the Disc
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Age Related Changes
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Central disc height is usually maintained – central expansion in an osteoporotic spine
Age Related Changes
Nucleus becomes more solid, dry and granular – less well differentiated
Bullough PG, O.Boachie-Adjei. Atlas of Spinal Diseases 1988
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Age Related Changes
Radial Fissure
Circumferential fissuring
Age Related Changes
1. Fibrillation and subsequent loss of articular cartilage of the Z joints 2. Laxity of the capsules and attenuation of the ligaments 3. Fracture of the articular process with strain deformation of the neural arch 4. Circumferential annular tears into a radial fissure / herniation of nucleus progressing to internal disruption of the disc, loss of disc height, resorption 5. Sclerosis of adjacent vertebral bodies
Kirkaldy-Willis WH. 1978
Muscles
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Muscles
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Thoracolumbar Fascia
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Abdominals
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Biomechanics of the Lumbar Spine
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Flexion
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Flexion
2 components § Anterior sagittal rotation ◦ 8 – 13 degrees
§ Anterior translation ◦ 1 – 3 mm translation
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
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Flexion
Anterior sagittal rotation resisted by Z joint capsule 39% Ligamentum flavum 13% Supraspinous / interspinous ligaments 19% Disc 29%
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Flexion
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Extension
2 components § Posterior sagittal rotation § Posterior translation ◦ 1.1 - 1.7 mm. § Limited when the inferior articular processes are forced against the laminae of the vertebra below
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
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Extension
IAP L4 Dense staining of adult pars interarticularis indicates its SAP L5 response to loading
pars
Rotation
After 3 degrees of rotation, the axis shifts to the impacted Z joint.
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Rotation
§ Contralateral facet compressed § Ipsilateral facet gapped § Disc strained by torsion and lateral shear
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Rotation
Resisted by § I.V.D. 35% § Posterior elements 65% Articular facets Neural arch Ligaments
Torsional Injuries
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Torsional Injuries
Peripheral tears in the annulus
Kirkaldy-Willis WH. 1978
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Side Flexion
Lee D. Lee LJ. The Pelvic Girdle 4th Edition 2011
Complex motion coupled with rotation Translation – same direction as side flexion
Lateral Flexion
Involves complex and variable combination of lateral bending and rotary movements of the interbody joints and Z joints
L1 to L4 lateral flexion associated with contralateral rotation (Pearcy & Tibrewal 1984) In flexion or extension??
L5 S1 - ipsilateral side flexion and rotation
Coupling
Should consider side flexion / rotation as a single motion about an oblique axis Direction of coupling may vary Dependant upon Segmental level Starting position Muscle recruitment Individual movement patterns Pathomechanics – disc, Z joint, ligament, muscle
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Axial Compression
Both the annulus fibrosus and the nucleus bear the load and transmit it to the vertebral end plates End plates are the weakest component and fail first Z joints participate in resisting compression in prolonged standing and with a lordotic spine
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition 1997
Axial Compression Injury
Taylor J.R. Disc injury may be associated with an end plate # or vertebral wedge #. The fracture is visible on x-ray but the disc injury may not be visible.
Compression Loading
Adams 2001
Hairpin bending of posterior annulus after specimen was subjected to repetitive mechanical loading in backwards bending and compression Nucleus appears normal – M – 39, L2-3
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Schmorl’s Node
Quiz – Test your Knowledge
Quiz
1. List the functions of the zygapophyseal joints. 2. Name the 3 components of the intervertebral disc and describe the mechanism of weight transmission. 3. What are the consequences of a failure to sustain a compression load? 4. Describe the biomechanics of flexion and rotation at the L3/L4 segment. 5. What resists axial rotation?
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Quiz
6. What is the biomechanical significance of the shape of the Z joints? 7. How does the disc receive its nutrition? 8. What is the function of ligamentum flavum and what is characteristic of this ligament? 9. What is the function of multifidus? 10. What is the significance of the shape of the vertebral canal in the lumbar spine and how does it differ from other regions?
Thanks for Listening!
References
Adams MA, Spinal Dysfunction and Pain: Recent Advances in Basic Science World Congress on Low Back and Pelvic Pain 2001 Bogduk N, Clinical Anatomy of the Lumbar Spine and Sacrum 3rd Edition Churchill Livingstone New York1997 Taylor JR, Twomey LT - several articles, slides and text, 1972 – 1999 McMinn RMH. Hutchings RT. Color Atlas of Human Anatomy Year Book Publishers Inc. Chicago 1985 Bullough PG. Boachie-Adjei O. Atlas of Spinal Diseases J.B. Lippincott Company Philadelphia 1988 Lee D. Lee LJ. The Pelvic Girdle 4th Edition Churchill Livingstone Elsevier 2011 Kirkaldy-Willis WH. Pathology and pathogenesis of lumbar spondylosis and stenosis. Spine 1978;3:319 Pearcy M. Tibrewal SB. Axial rotation and lateral bending in the normal lumbar spine measured by 3-dimensional radiography. Spine 1984;9:582 Primal Pictures Ltd. Interactive Spine 2011 Rohen JW. Yokochi C. Color Atlas of Anatomy Igaku-Shoin New York Tokyo 1988
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