BIOMECHANICS OF HIP JOINT

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

9. FEMORAL VERSION 15-20 DEGREE

10. ARTICULAR CONGRUENCRE

11. HIP JOINT CAPSULE

12. STUCTURAL ADAPTAION TO WEIGHT BEARING

13. TRABECULAR SYTEM

14. ROM OF HIP

15. MOVEMENTS OF HIP

16. ABDUCTORS OF HIP

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

18. 2.LATERAL PELVIC TILT ( FRONTAL TILT)

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

20. HIP BIOMECHANICS

21. 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

22. TYPES OF LEVER

23. HIP IS FIRST ORDER FULCRUM BODY WEIGHT ABDUCTOR MUSCLES

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

25. 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)

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

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

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

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

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

31. - - 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

32. 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

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

34. HISTORY

35. LOW FRICTION TORQUE ARTHROPLASTY

36. CLINICAL APPLICATION

37. FEATURES OF FEMORAL COMPONENT

38.   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

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

40. 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

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

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

43. TORSION

44. 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

45. INCRESED HEAD/NECK RATIO

46. 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

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

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

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

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

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

52. THANK YOU