Biomechanics of hip

1. BIOMECHANICS OF HIP JOINT
MODERATOR: DR SUNIL.G. KINI
PRESENTER: DR MAHESH RAWAT

2. # ANATOMY OF HIP JOINT
# BIOMECHANICS OF HIP JOINT
# HISTORY
# APPLIED BIOMECHANICS IN THA

3. HIP JOINT
• Articulation of acetabulum of pelvis and head of
femur .
• Diarthroidal ball and socket joint.
• Three degree of motion:
1- flexion and extension ( sagittal plane )
2-abduction and adduction (frontal plane)
3-rotation ( transverse plane)

4. • Primary function of hip joint is to support
weight of head , arms , trunk (HAT) both in
static erect posture and dynamic postures like
ambulation, running and stair climbing.

5. STRUCTURE OF HIP JOINT
ACETABULUM CENTRE EDGE ANGLE

6. ACETABULUM ANTEVERSION
15 DEGREE
ACETABULUM
INCLINATION
45 DEGREE

7. FEMUR

8. NECK SHAFT ANGLE

10. FEMORAL VERSION
15-20 DEGREE

12. ARTICULAR CONGRUENCRE

13. HIP JOINT CAPSULE

14. STUCTURAL ADAPTAION TO WEIGHT
BEARING

16. TRABECULAR SYTEM

17. ROM OF HIP

18. MOVEMENTS OF HIP

20. ABDUCTORS OF HIP

21. MOTION OF PELVIS OVER FEMUR
1. ANTERIOR AND POSTERIOR PELVIC TILT(SAGITTAL PLANE)

22. 2.LATERAL PELVIC TILT ( FRONTAL TILT)

23. 3.FORWARD AND BACKWARD PELVIC ROTATION
(TRANSVERSE PLANE )

24. HIP BIOMECHANICS

25. WHAT IS BIOMECHANICS?????
• BIO + MECHANICS
(ANATOMY+PHYSIOLOGY) (ENGENERNING)
• SCIENCE THAT EXAMINES FORCE ACTING UPON AND
WITHIN A BIOLOGICAL STUCTURE AND EFFECTS
PRODUCED BY SUCH FORCES

27. TYPES OF LEVER

29. HIP IS FIRST ORDER FULCRUM
BODY WEIGHT
ABDUCTOR MUSCLES

30. FORCES ACTING
ACROSS HIP JOINT
• BODY WEIGHT
• ABDUCTOR MUSCLE
PULL
• JOINT REACTION FORCE

31. TORQUE ( MOMENT) IS TENDENCY OF A FORCE TO
ROTATE A BODY AROUND AN AXIS
TORQUE (MOMENT)=FORCE X DISTANCE
1. Body weight moment = 3D × W
2. Abductor moment = W’ × D
• To level the pelvis
3D × W = W’ × D
so, hence W’ = 3W
• Force to balance pelvis on a single
leg stance. (Real ratio is around 2.5)

32. TO MAINTAIN STABLE HIP , TOURUE PRODUCE BY BODY
WEIGHT IS COUNTERED BY ABDUCTOR MUSCLES PULL

33. • M × a = K × b
as ,b>a so M>K
• joint forces range of
2.3–4.6 BW For one-
legged stance.

34. JOINT REACTION FORCE
FORCE GENERATED WITH IN THE JOINT IN RESPONSE TO THE
FORCE ACTING ON THE JOINT

35. BIPEDAL STANCE
• BW is equally
distributed across both
hips.
• No muscular forces
require to maintain
equilibrium
• Each hip carries one-
third of BW

36. SINGLE LEG STANCE
• Hip is assumed to be in
the resting position at
one-legged stance
• Only abductors acting at
30 degree are active.

37. -
-The weight supported in single leg stance = 5/6
(total body weight – weight of one lower limb).
-COG shifts to the non supportive leg and produce
downward force to tilt pelvis
-Supportive leg abductors exert downward counter
balancing force with hip joint acts as fulcrum

38. • For hip to remain static
the sum of forces should
be zero, so
• R’ – (M + K) = 0
(R’ is joint reaction force
acting at 30 degree)
- M=2.5k
• R’ = 3.5K
• R = R’/cos θ = R’/cos
30degree
(R is joint reaction force)
• R = 4K ≈ 4 BW

39. JOINT REACTION FORCE
COXA VALGA ( INCRESED) COXA VARA (DECRESED)

40. HISTORY

43. LOW FRICTION TORQUE ARTHROPLASTY

44. CLINICAL APPLICATION

45. FEATURES OF
FEMORAL
COMPONENT

46. DECREASE JOINT REACTION FORCE
Increase ratio of A/B (shift center of hip medially)
1.Acetabular component shifted medially
2.Femoral side:
-Increasing offset of femoral component
-Long stem prosthesis
-Varus neck shaft angle
-Lateralization of of greater trochanter

47. 3.PATIENT GAIT
Shifting body weight over
affected hip-REDUCING
THE LEVER ARM OF THE
BODY WEIGHT
(POSITIVE
TREDLENGBURG GAIT)

48. 4.CANE ON CONTRALATERAL HAND
FORCE IS TRANSFERED TO
WALKING STICK THROUGH THE
HAND:
1)EFFECTIVE LOAD OF BW
REDUCED
2)SO,TURNING MOMENT
AROUND FEMORAL HEAD IS
REDUCED –REDUCED
ABDUCTOR MUSCLES
DEMAND

49. 5. CARRYING LOAD IN IPSILATERAL HAND
• Additional downward moment on same side
of rotational point.

50. INCREASE JOINT REACTION FORCE
• Valgus neck shaft angle
- Reduces shear across the joint

51. TORSION

52. KINEMATICS AFTER T.H.R
• 5 FACTORS TO RESTORE THE GOALS:
(RESTORE THE FUNCTION BY RESTORING NORMAL ANATOMY)
-CENTRE OF ROTATION
-ANTEVERSION OF FEMORAL AND ACETABULAR COMPONENT
-FEMORAL OFFSET
-LEG LENGTH
-BEARING

53. INCRESED HEAD/NECK RATIO

54. JUMP DISTANCE:
Distance the head must travel to escape the rim
of the socket and is generally approximated to
be half the diameter of the head

55. 1.CENTRALIZATION OF FEMORAL HEAD BY DEEPENS THE
ACETABULUM – REDUCES BODY WEIGHT LEVER ARM
TO REDUCE JOINT REACTION FORCE
IN THA

56. 2.INCREASE IN NECK LENGTH AND LATERAL
ATTACHMENT OF TROCHANTER –INCREASE
ABDUCTOR LEVER ARM

57. TO REDUCE THE WEAR OF AMPLANT
LENGTHENED ABDUCTOR
LEVER ARM
DECREASE BW LEVER ARM

58. ADVANTAGES OF INCREASING OFFSET
• INCREASE ABDUCTOR
LEVER ARM
• DECREASE JRF
• LESS IMPINGMENT
• DECREASE WEAR
• INCREASE TORQUE ON
STEM

59. HOW TO INCREASE OFFSET
NECK-STEM ANGLE IS
REDUCED
NECK IS ATTACHED AT MORE
MEDIAL POSITION ON STEM

60. THANK YOU