Hip Joint Biomechanics Flashcards
Name 3 general aspects of the Lower Limb
1- adapted to bipedal locomotion
2- provide a stable platform for movement to occur
3- designed to support the entire weight of the trunk and upper extremities
Define “Plane”
Movement can be describe with reference to 3 imaginary planes passing through the center of gravity and being perpendicular to each other’s.
What are the different planes of motion ?
- sagittal (antero-posterior) plane : dividing the body in left and right parts
- frontal (coronal) plane : dividing the body in anterior and posterior parts
- transverse (horizontal) plane : dividing the body in superior and inferior parts
Define “Axis”
An imaginary line where a rotation can occur. Axis of motion can be defined as the intersection between 2 planes. They are perpendicular to the planes.
What are the different axis of motion
- Antero-posterior (sagittal) axis : passes from back to front and is the intersection between the sagittal and the transversal planes and is perpendicular to the frontal plane
- Transveral (frontal) axis : passes from left to right and is the intersection between frontal and transversal planes and is perpendicular to the sagittal plane
- Longitudinal (vertical) axis : passes from up to down and is the intersection between sagittal and frontal planes and is perpendicular to the transversal plane
What are the general hip joint features ?
- diarthrose
- powerful weight bearing ball and socket joint
- the acetabulum is concave while the femoral head is convex
- auricular surfaces are curved but the hip joint consists into 2 incongruent shapes : an arched acetabulum and a rounded femoral head
Which part of the acetabulum articulates with the head of the femur ?
Only the lunate surface of the acetabulum is covered with hyaline cartilage and articulates with the head of the femur
Describe the lunate surface
It is discontinuous as the inferior margin of the lunate is interrupted by the acetabular notch spanned by the transverse acetabular ligament that connects the 2 ends (and merges with the ligamentum teres)
Describe the orientation of the acetabulum
It is oriented inferiorly, laterally and anteriorly
How can you assess the orientation of the acetabulum ?
From radiographies, you can determine the angle of Wiberg and the angle of acetabular anteversion
Define the angle of Wiberg and what it measures
Is a way to determine the magnitude of inferior orientation of the acetabulum, using a line connecting the lateral rim of the acetabulum to the center of the femoral head. This line forms an angle with the vertical called angle of Wiberg.
It measures the the amount of inferior tilt of the acetabulum and also the amount of coverage of the femoral head.
What is the usual angle of Wiberg in Women and Men ?
- Women : 35°
- Men : 38°
What is the angle of acetabular anteversion
It measures the magnitude of anterior orientation of the acetabulum
What is the angle of acetabular anteversion in Women and Men ?
Women : 21,5°
Men : 18,5°
Give 3 features of the femoral head
- it is 2/3 of a sphere
- the fovea capitis is not covered by articular cartilage as this is where the ligamentum teres is attached
- is attached to the femoral neck
What is the orientation of the femoral head
The femoral head faces medially, superiorly and anteriorly
How can you define the angulation of the femur ?
Using radiographies to determine the angle of inclination and the angle of torsion
Define the angle of inclination
- Is the neck-to-shaft angle
- occurs in the frontal plane
- occurs between an axis through the femoral head and the femoral shaft
- ranging from 115° to 140° in adults (greater in infancy)
- decline in elderly
What pathologic aspects can be determined using the angle of inclination ?
Coxa Vara : pathologic decrease of the the angle of inclination of the femur
Coxa Valga : pathologic increase of the angle of inclination of the femur
What is the angle of torsion ?
- can be determined looking down the length of the femur
- using an axis through the femoral head and neck in the transverse plane making an angle with an axis through the femoral condyles
- average angle : 15° to 20° in adults
What pathologic aspects can be determined by the angle of torsion ?
- pathologic increase causes excessive anteversion
- pathologic decrease causes retroversion
What are the motions happening in the hip joints
As the hip joint is a ball and socket joint, the femur moves through 3 degrees of freedom :
- flexion/extension
- Abduction/adduction
- internal/external rotation
Describe hip joint flexion/extension (femoral on pelvic hip rotation)
Plane : sagittal Axis : frontal Flexion knee flexed : 140° Limited by : - posterior inferior capsule - gluteus Maximus resistance Extension : 15° Limited by : - posas major and rectus femoris resistance - illiofemoral ligament
Describe hip Abduction/Adduction
Plane : frontal Axis : sagittal Abduction : 40°-50° Limited by : - Pubofemoral ligament - Adductor brevis and adductor longus resistance Adduction : 20°-30° Limited by : - Piriformis, gluteus medius and TFL + illiotibial tract resistance
Describe external/internal hip rotation
Plane : transverse Axis : longitudinal Internal rotation : 35°-40° Limited by : - Piriformis resistance - ischiofemoral ligament External rotation : 45°-50° Limited by : - illiofemoral and pubofemoral ligaments
What are the different amplitudes of the hip flexion ?
- natural (knee bent) : 120°
- pressing the knee close to trunk (knee bent) : 145°
- leg straight : 90°
What are the extracapsular ligaments of the hip joint ?
- illiofemoral ligament
- ischiofemoral ligament
- pubofemoral ligament
Describe the illiofemoral ligament
- Y shaped with two portions : superior and inferior
- strongest ligament of the 3 composing the complex
- origin : AIIS
- insertion : inter trochanteric line
- prevents excessive posterior tilt of the pelvis
Describe the ischiofemoral ligament
Origin : ischium
Insertion : greater trochanter