Transcript Biomechanics of hip - THAAI PHYSIO CLINIC.

Biomechanics of the hip
Prof. Sung-Jae, Lee Ph.D
Inje Univ.
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Introduction
Anatomical considerations
The Acetabulum
The Femoral Head
The Femoral Neck
Kinematics
Range of Motion
Surface joint Motion
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Kinetics
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Statics
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Dynamics
Effect of External Support on Hip Joint Reaction Force
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Introduction
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One of the largest and most stable joint:
The hip joint
Rigid ball-and-socket configuration
(Intrinsic stability)
Anatomy
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Composed of :
Head of femur
Acetabulum of pelvis
18 16 7 9
Wide range of motion
Walking, sitting, squatting
Anatomy
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Surrounding large, strong muscles
Acetabulum
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Concave component of ball
and socket joint
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Cover with articular
cartilage
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Provide with static stability
Acetabulum
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Facing obliquely forward, outward and
downward
Acetabulum
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Labrum: a flat rim of
fibro cartilage
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Transverse acetabular ligament
Acetabulum
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Unload: small diameter
region
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in vitro Load distribution
The femoral head
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Femoral head : convex component
Two-third of a sphere
Cover with cartilage
Rydell (1965) suggested : most load
superior quadrant
The femoral neck
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Frontal plane (the neck-to-shaft angle)
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Transverse plane (the angle of anteversion)
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Neck-to-shaft angle :
125º, vary from 90º to 135º
Effect : lever arms
Neck-to-shaft angle & Abductor muscle force
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Angle of anteversion :12º
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Effect : during gait
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>12º :internal rotation
<12º :external rotation
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Femoral neck :Cancellous bone,
medial and lateral trabecular
system
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*Joint reaction force parallels the
medial trabecular system
Joint reaction force
medial trabecular system
Frankel, 1960
Femoral Intertrochanteric Fractures
*The femur neck is the most common fracture site in elderly persons
Kinematics
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Hip motion takes place in all three planes:
sagittal (flexion-extension)
frontal (abduction-adduction)
transverse (internal-external rotation)
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Muscle, ligament and configuration…
asymmetric
Kinematics
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0~140
Rang of motion : sagittal, frontal, transverse
0~15
0~30
0~25
0~90
0~70
Kinematics
Frontal plane
35 to 40°
Transverse plane
One gait cycle
Toe-off
Kinematics
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Murray and coworkers (1969) studied the walking
patterns of 67 normal men of similar weight and height
ranging in age from 20 to 87 years and compared the
gait patterns of older and younger men
Kinematics
Old man : shorter strides
 Decrease:
Rang of hip flexion,
extension
Plantar flexion of ankle
Heel-floor angle
Old man
Young man
Kinematics
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hip flexion of at least
120°
Abduction and
external rotation of at
least 20 °
Surface Joint Motion
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Surface motion in the hip joint can be considered as
gliding of the femoral head on the acetabulum.
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Center of rotation:
estimated at the center of the femur head
Kinetics
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Forces acting on the hip joint : must be understood
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Prostheses design
Fixation devices
Osteotomy operation
Rehabilitation
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STATICS and DYNAMICS
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Statics
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Two-leg stance : without muscle contraction,
stabilization by joint capsule and capsular ligament
Calculation of the joint reaction force becomes
simple
Two-leg to single-leg stance : gravity line change
Two methods : the simplified free-body technique
& mathematical method
Single-leg
Neutral position
Shoulders tilted opposite
Shoulders are tilted max.
over supporting hip joint
Pelvis sags from support
Solvent
(1) Free-body for coplanar forces (three force member)
Solvent
(2) free-body for equilibrium equation
equilibrium equation (moment)
It’s necessary to know b, c
for solving A
equilibrium equation(x,y force)
Dynamics
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Loads on the hip joint during dynamic activities
HS
TO
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Several factors :
a wider female pelvis
a difference in the inclination of the femoral
neck-to-shaft angle
a difference in footwear
and differences in the general pattern of gait
In vivo measurement of force:
From prosthesis
An increase in muscle
activity at the faster
cadence resulted in higher
force on the prosthesis.
Nail plate :
osteotomy or neck
fracture
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Thank you !