lsp & pelvis spinal mechanics Flashcards
spine as a spring
The s shape of the spine is the spring
-The plasticity (multiple directions and multiple forces) of the column lies in its make-up, that is multiple components superimposed on one another and interlinked by ligaments and muscles.
-A conical column with curves becomes a spring which has both compressive and tensile strength qualities, leading to great tolerance of ground force reaction forces, gravitational forces, multi vector movements.
-It is both a support (trunk), and suspends (LEXX’s).
-Spiralling of tissues- the spring is 3D
fryet’s law
=side bending rarely happens without rotation
-Reason why scoliosis develops as it does- starts with a sidebend- to get eyes back to horizon and correct, rotation is added
spinal curves
Scoliosis (idiopathic- developmental in teenage years, Para spinal musculature creates a sidebend) = lateral deviation
Scheurmans kyphosis (developmental condition in teenage. Increased thoracic flexion. Ap deviation) = thoracic kyphosis leading to flattened lumbar or hyperextended neck
centre of gravity and lateral plumb line
Vertbrae C2, L2, L5, greater trochanter
Cervical spine= lies central to plumb line to support the head
Thoracic spine= lies posterior to plumb line to make room for internal organs
Lumbar spine= lies central to plumb line to support weight of the trunk
Intervertebral disc- composition and innervation
-The discs separate the vertebra as part of a functional segmental unit acting in concert with the facet joints.
-The intevertebral disc makes up approximately 20-25% total length of spinal column.
-Usually the disc has no nerve supply, except for the peripheral posterior aspect innervated by sinuvertebral nerve. Lateral aspect innervated peripheraly by branches of ant and grey rami communicants.
-The pain sensitive structures are the ALL, PLL, vertebral body, nerve root and cartilage of facet joint.
intervertebrak disc
-Water is a non-compressible fluid, allowing a state of ‘preloading’ to occur.
-This allows a greater resistance to compressive forces.
-The fluid nature of water allows for resistance to lateral flexion.
-The layering of the annulus allow tolerance to asymmetrical loading, especially torsion.
-20 alternating orientation of layers of annulus allow for multiple vectors of movement.
-The annulus and nucleus become a functional couple reliant on the structural intergrity of each other.
-This becomes a mechanism for self-stabilisation.
-The combination of a gel filled nucleus pulposus and the fibrous nature of annulus.
-Semi fluid quality of disc accommodates the variation in angle between veterbrae to accommodate the changes in lordotic to kyphotic curves
pathological processes
-Degenerative- spondylosis
-Developmental- scoliosis/ scheurmans
-Rheumatological- ankylosing spondylitis
-Traumatic- spondylolythesis
-Nutritional- osteoporosis
sequence of spondylotic changes
Definition: Spondy – Spine, Osis – degeneration
Structures involved: Vertebrae, discs, facets, capsules, muscle and ligaments.
Initial phase: degeneration of disc leading to reduced disc height.
This leads to approximation of facets ad ligamentous laxity.
Resulting in acute episodes of pain and muscle spasm.
Middle stage: segment instability due to, ligamentous laxity. Chronic muscle fatigue, hypoxia and microtrauma due increased stabilising effort from muscles. Resulting in constant low grade ache.
Late stage: Osteophyte formation around facets and vertebral bodies leads to more episodes of acute pain along with constant acute from overuse of paraspinal musculature
form/ force closure pelvis
Form closure= when structures have congruent shapes and these come together and create a stable structure
Force closure= when soft tissue structures around bony structures (muscles, ligaments and capsules hold the structure together)–> sacroiliac joint ligaments contracts and hold the bones together for stability
weight bearing forces (bilateral stance)
In standing / upright weight bearing (WB) activities, at least half the weight of head, arms, trunk (HAT) passes down through the pelvis to the femoral head.
Whereas the ground reaction force (GRF) travels up the shaft of femur to pelvis
force coupling
=pivot point where multiple forces pull in opposing directions so that it creates rotation
A=pivot point around facet joint B= pivot point around acetabulum
Key muscle groups affecting pelvis in this:
-Lumbar erector spinae
-Quadratus lumborum
-Hamstrings
-Hip flexors
-Psoas
-Abdominal wall
