biomechanics of hip joint

1. BIOMECHANICS
OF HIP
Moderator : Dr Adarsh
Presenter : Dr Hisham
JSS Medical College
Mysore

2. “Biomechanics is the science that examines forces
acting upon and within a biological structure and
effects produced by such forces “
- Jim Hay

3. History
• Term coined by Nikolai Bernstein
( soviet neurophysiologist)
• From ancient Greek word
bios – life
mechanike - mechanics

4. Introduction
to orthopaedic
biomechanics
• Orthopaedic surgery is the branch of medicine
that deals with congenital and developmental,
degenerative and traumatic conditions of the
musculoskeletal system.
• Mechanics is the science concerned with loads
acting on physical bodies and the effects
produced by these loads.
• Biomechanics is the application of mechanics to
biological systems.
• Therefore, orthopaedic biomechanics is about
the effects of loads acting on the
musculoskeletal system only or with the
associated orthopaedic interventions.

5. • Statics is concerned with the effects of loads
without reference to time. Static analysis is
applied when the body is stationary or at one
instant in time during dynamic activity.
• Dynamics addresses the effects of loads over
time. It is further divided into two main subjects:
Kinematics describes motion of a body over
time and includes analyses such as
displacement, velocity and acceleration.
Kinetics is the study of forces associated with
the motion of a body.
Biomechanics - is
divided into two main
domains

7. IMPORTANCE
• To study injury mechanism
• In methods of treatment – conservative and operative for more
dynamic stability
• Analysis of complications
• Performance during sports and daily activity
• Design of orthotics and prosthotics

8. Hip Joint anatomy
• It is the largest and most stable joint.
• Hip joint is a synovial articulation
between head of femur and
acetabulum
• Type: Multiaxial ball and socket type
of synovial joint
• Hip joint is designed for stability over
a wide range of movements

9. Joint
Capsule
• Strong fibrous capsule
• Anteriorly– along the acetabular labrum and
intertrochanteric crest, more thicker
• Posteriorly –across femoral neck partially
• Capsule has longitudinal and circular fibers
• The circular fibers form a collar around the
femoral neck called the zona orbicularis.
• The longitudinal retinacular fibers travel along
the neck and carry blood vessels.

10. Synovial
Membrane
• Extensive membrane – lines the capsule
• Attached over the margins of articular surface
• Lines the intracapsular portion of neck of
femur and both surfaces of acetabular labrum,
transverse ligament and fat in acetabular fossa.
• Forms a tubular covering around the ligament
of head of femur

11. • 3 ligaments reinforces and stabilize the
joint-
• 1) iliofemoral ligament
• 2) pubofemoral ligament
• 3) ischiofemoral ligament
• Fibers of all three ligaments are oriented
in a spiral fashion around the hip joint so
that they become taught when joint is
extended.
Ligaments Of
Hip Joint

12. Iliofemoral Ligament
• Ligament of Bigelow
• One of the strongest ligament in the body
• Triangular , Y-shaped
• Apex attached to Anterior inferior iliac spine
• Base to intertrochanteric line
• Reinforces joint anteriorly
• Prevents over extension while standing
• Prevents trunk from falling backwards while standing

13. Pubofemoral
Ligament • Support the joint inferomedially
• Triangular in shape
• Attachment:-
• Superiorly, attached to the iliopubic
eminence, the obturator crest
• Inferiorly, merges with the capsule
and lower band of iliofemoral
ligament
• It limits extension & abduction

14. Ischiofemoral
Ligament
• Reinforces posterior aspect of
Fibrous membrane.
• Medially: attached to ischium, Just
posteroinferior to acetabulum
• Laterally: to greater Trochanter deep
to the iliofemoral Ligament.
• Limits flexion

15. Ligamentum
Teres • Round Ligament/ Ligament of Head of Femur
• Triangular and Flat
• Apex – fovea capitis
Base to acetabular notch & transverse
ligament.
• Ensheathed by synovial membrane.
• Transmits arteries to head of femur

16. • Fibro-cartilaginous rim
• Attached to the acetabular margin
• Triangular in cross section
• Deepens the socket
• Grasps the femoral head
• It enhances joint stability by acting as a seal to maintain
negative intra-articular pressure
Acetabular Labrum

17. • Extends across acetabular notch
• Blends with base of lig. of head of femur
• Represents part of labrum without cartilage
cells
Transverse Acetabular
Ligament

18. Anterior Compartment
• Sartorius
• Illiopsoas
• Quadriceps femoris
MUSCLES AROUND HIP JOINT

19. • Pectineus
• Adductor longus
• Adductor brevis
• Adductor magnus
(Adductor portion)
• Gracilis
Adductor m
(Adductor p
Adductor
(Hamstring
agnus
ortion)
magnus
portions)
Medial compartment

20. Posterior
compartment
• Hamstring muscles:
• Biceps femoris.
• Semitendinosus.
• Semimembranosus.

21. Muscles of the Gluteal Region
•
•
•
•
•
•
•
•
•
Gluteus maximus
Gluteus medius
Gluteus minimus
Tensor fascia lata
Piriformis
Superior Gemellus
Inferior Gemellus
Obturator internus
Quadratus femoris

22. • The hip joint has a wide range of movement but
less than the shoulder joint
• Flexion/extension : sagittal plane
• abduction/adduction : frontal plane
• medial /lateral rotation : transverse plane
Movements And
Mechanisms

23. Ranges of passive joint motion typical of the hip joint
• Flexion 90° with the knee
extended and 120° when the
knee is flexed
• Extension 10° to 20°
• Abduction 45° to 50°
• Adduction 20° to 30°
• Internal and External
rotations of the hip the
typical range is 42° to 50°

25. STRUCTURE OF THE HIP
JOINT
• Proximal Articular Surface ( Acetabulam )
• Distal articular surface ( Head of the femur )

26. STABLE JOINT
Strong bones Powerful muscles Strongest ligaments Tremendous degree of
forces acting around
Mobile as well as
stable

27. The primary function of the hip joint is to support the weight of
the head, arms, and trunk (HAT) both in static erect posture and in
dynamic postures such as ambulation, running, and stair climbing.
Also provides pathway for transmission of forces between Pelvis
& Lower Extremities

28. • innominate bone with contributions from the
ilium (approximately 40% of the acetabulum),
ischium (40%) and the pubis (20%) .
Acetabulum is directed laterally ,inferiorly and
anteriorly
Acetabular axis forms an angle of 30 degree to
40 degree with horizontal – acetabulum
overhangs femoral head
ACETABULUM

29. Acetabular depth can
be measured as The
center edge angle of
Wiberg
• Men = 380
• Women = 350
• Smaller CE angle
(more vertical) = ↓
coverage of head
of femur, ↑ risk
superior
dislocation of
femoral head

30. Acetabular Direction
• Long axis of acetabulum points
• Forwards : 15-200 Anterior Version
• 450 Inferior Inclination
ante version

31. • Anteversion of the acetabulum exists when the
acetabulum is positioned too far anteriorly in the
transverse plane
• Retroversion exists when the acetabulum is
positioned too far posteriorly in the transverse plane

32. Femur
• There are two angulations made by the head
and neck of the femur in relation to the shaft
Angle of Inclination( NECK-SHAFT)occurs
in the frontal plane between an axis through
the femoral head and neck and the
longitudinal axis of the femoral shaft
Angle of Torsion(FEMORAL VERSION)
occurs in the transverse plane between an
axis through the femoral head and neck and
an axis through the distal femoral condyles

33. ANGLE OF
INCLINATION OF
FEMUR
• The angle of inclination of the
femur approximates 125°
• Normal range from 120° to
135° in the unimpaired adult
• A pathological increase in the
medial angulation between the
neck and shaft is called coxa
valga
• A pathological decrease is
called coxa vara

35. ANGLE OF TORSION OF
THE FEMUR
• The angle of torsion of the femur can best be
viewed by looking down the length of the
femur from top to bottom
• An axis through the femoral head and neck in
the transverse plane will lie at an angle to an
axis through the femoral condyles, with the
head and neck torsioned anteriorly (laterally)
with regard to an angle through the femoral
condyles

36. Axis of lower limb
Mechanical axis line passes between center of hip joint
and center of ankle joint.
Anatomic axis line is between tip of greater trochanter to
center of knee joint.
Angle formed between these two is around 60

37. STRUCTURAL
ADAPTATIONS TO WEIGHT
BEARING
• In standing or upright weight bearing
activities, at least half the weight of the
HAT (the gravitational force) passes
down through the pelvis to the femoral
head, whereas the ground reaction force
(GRF) travels up the shaft.

39. MOTION OF
PELVIS ON
THE
FEMUR
• Whenever the hip joint is weight-bearing,
the femur is relatively fixed, and motion of
the hip joint is produced by movement of
the pelvis on the femur

40. Anterior and Posterior Pelvic Tilt
 In the normally aligned pelvis, the anterior
superior iliac spines (ASISs) of the pelvis
lie on a horizontal line with the posterior
superior iliac spines and on a vertical line
with the symphysis pubis
 Anterior and posterior tilting of the pelvis
on the fixed femur produce hip flexion and
extension

41. • Hip extension through posterior tilting of the pelvis
Hip flexion through anterior tilting of the pelvis

42. Centre of
gravity
• Weight of the objects
act through the centre
of gravity.
• In humans  just
anterior to S2

43. • If centre of gravity or line of weigh transmission is posterior to hip
and anterior to knee - stable position
• If weight transmission is anterior – patient falls backwards and vise
versa

44. Lever System
Definition:-
A rigid bar resting on pivot used to move a
heavy or firmly fixed load with one end when effort is
applied to other end

45. Hip abductor
mechanism
First Order Lever

46. • Fulcrum – Centre of hip
• Load -body weight
• Effort -Abductor tension

47. To maintain stable hip,
torques produced by the
body weight is countered by
abductor muscles pull.
Abductor force X lever arm A = Body weight X leverarm B

48. • Forces acting
across hip joint
 Body weight
 Abductor muscles
force
 Joint reaction force

49. Joint reaction force
Defined as “force generated within a joint in response to forces acting on the
joint’’
In the hip, it is the result of the need to balance the moment arms of the body
weight and abductor tension
Maintains a level pelvis

51. Joint reaction force
-2W during SLR
- 3W in single leg stance
-5W in walking
-10W while running

53. Hip disorders • Management of painful hip disorders – The
aim is to reduce joint reaction force
• JRF= Body weight + Abductor force
Strategies to reduce JRF are achieved via
• Reducing body weight or its moment arm
• Help abductor force or its moment arm

54. A. Reducing body weight or its
moment arm

55. B. Trendelenburg gait
to decrease the BW
moment arm
• The patient sways the body
weight over, towards the
affected side
• This lateral motion decreases
the body weight moment arm (
the functional demands on the
abductors are decreased ) and
hence the joint reaction force
JRF

56. C. Help abductor
force-Provide
additional support
1.Walking stick in opposite hand
Walking stick exert upward force,
thus helping the abductors by
reducing the weight
Small abductor force leads to
reduced JRF
2.Suitcase in ipsilateral hand

57. Incorrect use of walking aids in patients with hip
pathology
hip int journal , A J sheperd
• A study was performed to assess if patients with hip pathology are
using their walking aids in the correct hand
• A questionair was given to patients
• Concluded that 47 % of patients were using the aid in incorrect hand
• Poorly educating the patient

58. D. Increase
abductor lever
arm
• Increase offset
• Osteotomy
• Greater trochanter lateral transfer
• Varus placement of THR

59. Bi-pedal stance
• Body weight is equally distributed
across both hips
• L.L constitute 2/6 (1/6 + 1/6), and
U.L & trunk constitute 4/6 the total
body wt.
• Little or no muscular forces
required to maintain equilibrium in
2 leg stance
• Body wt. is equally distributed
across both hips
• Each hip carries 1/3rd body wt.
BW
R R

61. Biomechanics in Femoral
neck deformities
COXA VALGA
• Increased neck shaft angle
• GT is at lower level
• Shortened abductor lever arm
• Tremendous force required to keep the pelvis in line
• Body wt arm remains same
• Increased joint forces in hip during one leg stance

62. • Decreased neck shaft angle
• GT is higher than normal
• Increased abductor lever arm
• Abductor muscle becomes inefficient as it is stretched beyond its
physiological limit
• Decreased joint forces across the hip during one leg stance
COXA VARA

63. Cane & Limp
• Both decrease the force exerted by the BW on
the loaded hip
• Cane transmits part of BW to the ground and
also provides a counter acting force thereby
decreasing the muscular force required for
balancing
• Limping shortens the body lever arm by
shifting the centre of gravity to the loaded hip

64. Compensatory Lateral Lean of the
Trunk
• the compensatory lateral lean of the
trunk toward the painful stance limb
will swing the line of gravity closer to
the hip joint, thereby reducing the
gravitational moment arm
• It does reduce the gravitational torque

65. Use of a Cane Ipsilaterally
Body weight passes mainly through cane

66. TRENDELENBURGSIGN
• Standon LEFTleg—ifRIGHThip drops, then it's
a + LEFTTrendelenburg
• Thecontralateral side drops becausethe ipsilateral
hip abductors do notstabilizethe pelvis to prevent
the droop.

67. normal
affected
1 2

68. COMPENSATED
TRENDELEBERG GAIT
• The patient sways the body weight over towards the affected side.
• This lateral motion decreases the body weight moment arm (the
functional demand on the abductors are decreased, and so is the
Joint reaction force.

71. THANKYOU

72. References
• Campbell – operative orthopaedics
• Tureks
• Joint structure and function – a comprehensive analysis
• Biomechanics in orthopaedics made easy