Anatomy and biomechanics of hip joint

Anatomy and biomechanics of hip joint by Dr Bipul Borthakur

1. ANATOMY AND BIOMECHANICS OF HIP JOINT DR BIPUL BORTHAKUR PROFESSOR & HOD, DEPT OF ORTHOPAEDICS,SMCH

2. ANATOMY It is the largest joint of the human body. 2nd largest weight bearing joint of human body. 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 Descriptive planes: • Flexion/extension : sagittal plane • abduction/adduction : frontal plane • medial /lateral rotation : transverse plane (circumduction) 

3. ANATOMY - ACETABULUM Acetabulum is the depression or fossa where the femoral head articulates . It is positioned in downward and outward direction The rim of acetabulum is raised slightly by a fibro cartilaginous collar known as acetabular labrum. Inferiorly the labrum bridges across the acetabular notch as the transverse acetabular ligament and converts the notch into foramen The lunate surface of the acetabulum is covered by hyaline cartilage except for fovea Acetabular fossa is non articular . Formed mainly by ischium and contains loose connective tissue.

4. ANATOMY -FEMUR Head of femur is globular and forms 2/3 of a sphere. Covered by hyaline cartilage (except fovea) The femur connects to the head via femoral neck The angle of inclination is approximately 135 degrees The angle of anteversion or torsion is forward relationship of head and neck. The angle of torsion is normally in the 12-15 degrees

5. ANATOMY -CAPSULE Strong, thick MEDIALLY : attached to margin of acetabulum, transverse acetabular ligament, and adjacent margin of obturator foramen LATERALLY : attached to intertrochanteric line of femur, Just proximal to intertrochanteric crest on posterior surface. Femoral neck : intracapsular Greater and lesser trochanter: extracapsular 

6. ANATOMY –SYNOVIAL MEMBRANE  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 and lines the fibrous membrane of joint

7. ANATOMY –LIGAMENTS   The ligaments of the hip joint can be divided into two groups – E x tracapsular and In tracapsular 3 ligaments reinforce the external surface of fibrous membrane and stabilize the joint they are 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 the become taught when joint is extended. This stabilizes the joint and reduces the amount of muscle energy required to maintain a standing position.

8. ANATOMY –LIGAMENTS

9. ANATOMY –LIGAMENTS Intracapsular : Ligament of head of femur. It is a relatively small structure, which runs from the acetabular fossa to the fovea of the femur. – It encloses a branch of the obturator artery (artery to head of femur), a minor source of arterial supply to the hip joint. Transverse acetabular ligament. Acetabular labrum.

10. ANATOMY –LIGAMENTS   LIGAMENTUM TERES : Also known as Round Ligament or Ligament of Head of Femur or foveal ligament Triangular and Flat Ensheathed by synovial membrane. Transmits arteries to head of femur from acetabular branches of medial circumflex and femoral arteries.

11. ANATOMY –LIGAMENTS

12. ANATOMY –NERVE SUPPLY   Femoral nerve (anteriorly) Femoral nerve not only supplies hip joint via intermediate and cutaneous nerve of thigh, also supplies skin of front and medial side of thigh Anterior division of Obturator nerve (inferiorly) Nerve to Rectus femoris Nerve to Quadratus femoris (posteriorly) Sciatic nerve Superior gluteal nerve (superiorly and posteriorly) Posterior division of obturator nerve supplies both hip and knee joint. Therefore sometimes there is referred pain to knee joint.

13. ANATOMY –NERVE SUPPLY

14. ANATOMY –BLOOD SUPPLY The hip joint is supplied with blood from: The medial circumflex femoral and lateral circumflex femoral arteries, which are both branches of the deep artery of the thigh (profunda femoris) There is also a small contribution from the foveal artery , a small vessel in the ligament of the head of the femur which is a branch of the posterior division of the obturator artery The hip has two anatomically important anastomoses, the cruciate and the trochanteric anastomoses, the latter of which provides most of the blood to the head of the femur. These anastomoses exist between the femoral artery or profunda femoris and the gluteal vessel

15. ANATOMY –BLOOD SUPPLY

16. ANATOMY-MUSCLES OF HIP JOINT

17. ANATOMY-MUSCLES OF HIP JOINT

18. ANATOMY-MUSCLES OF HIP JOINT

19. ANATOMY –MOVEMENTS

20. BIOMECHANICS –HIP JOINT The hip joint, or coxofemoral joint, is the articulation of the acetabulum of the pelvis and the head of the femur Diarthrodial ball-and-socket joint There are three degrees of freedom: 1. flexion/extension in the sagittal plane . 2. abduction/adduction in the frontal plane . 3. medial/lateral rotation in the transverse plane.

21. BIOMECHANICS –HIP JOINT THE NECK OF FEMUR : Angulated in relation to the shaft in 2 planes : sagittal & coronal Neck Shaft angle 140 deg at birth 120-135 deg in adult Ante version Anteverted 40 deg at birth 12-15 deg in adults

22. BIOMECHANICS –HIP JOINT ACETABULAR DIRECTION : long axis of acetabulum points forwards : 15-20 degree ante version 45 degree inferior inclination ante version

23. BIOMECHANICS –HIP JOINT 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 6-7 degrees

24. BIOMECHANICS –HIP JOINT First order lever fulcrum (hip joint) forces on either side of fulcrum i.e , body weight & abductor tension

25. BIOMECHANICS –HIP JOINT To maintain stable hip, torques produced by the body weight is countered by abductor muscles pull. Abductor force X lever arm1 = weight X leverarm2

26. BIOMECHANICS –HIP JOINT FORCES ACROSS THE HIP JOINT IN TWO LEG STANCE :   Lower Limb constitute 2/6 (1/6 + 1/6), and Upper Limb & trunk constitute 4/6 the total body weight Little or no muscular forces required to maintain equilibrium in 2 leg stance Body weight is equally distributed across both hips Each hip carries 1/3rd body weight (4/6 = 2/3 = 1/3 + 1/3)

27. BIOMECHANICS –HIP JOINT Single leg stance - Right Right Lower Limb supports the body weight & also the Left Lower Limbs i.e. 5/6th total body weight. Effective Centre of gravity shifts to the non-supportive leg (L) & produces downward force to tilt pelvis Right abductors must exert a downward counter balancing force with right hip joint acting as a fulcrum. 4/6 +1/6 =5/6 i.e. Body weight acts eccentrically on the hip and tends to tilt the pelvis in adduction ---- balanced by the abductors

28. BIOMECHANICS –HIP JOINT USE OF CANE / WALKING STICK It creates an additional force that keeps the pelvis level in the face of gravity's tendency to adduct the hip during unilateral stance. D ecreases the moment arm between the center of gravity and the femoral head(R) The cane's force must substitute for the hip abductors. Long distance from the Centre of hip to contralateral hand offers excellent mechanical advantage

29. BIOMECHANICS –HIP JOINT Cane and Limp Both decrease the force exerted by the body weight on the loaded hip Cane: transmits part of the body weight to the ground thereby decreasing the muscular force required for balancing Limping shortens the body lever arm by shifting the centre of gravity to the loaded hip

30. BIOMECHANICS –HIP JOINT TRENDELENBURG SIGN Stand on LEFT leg—if RIGHT hip drops, then it's a + LEFT Trendelenburg The contralateral side drops because the ipsilateral hip abductors do not stabilize the pelvis to prevent the drop.

31. BIOMECHANICS –HIP JOINT Biomechanics in neck deformities : Coxa valga : Increased neck shaft angle Greater Trochanter is at lower level Shortened abductor lever arm Body weight arm remains same Increased joint forces in hip during one leg stance Less muscle force required to keep pelvis horizontal

32. BIOMECHANICS –HIP JOINT Coxa Vara Decreased neck shaft angle Greater Trachanter is higher than normal Increased abductor lever arm Abductor muscle length is shortened Decreased joint forces across the hip during one leg stance Higher muscle force is required to keep pelvis horizontal

33. BIOMECHANICS –HIP JOINT Joint Reaction Force Forces generated within a joint in response to external forces (both intrinsic and extrinsic). Can reach 3 to 6 times body weight & is primarily due to contraction of muscles crossing the hip. Twice during SLRT 3 times in single leg stance 5 times in walking Upto 10 times while running Reduced to half upon using a cane

34. BIOMECHANICS –HIP JOINT

35. BIOMECHANICS –HIP JOINT Biomechanics of THR Principle – to decrease joint reaction force Centralization of femoral head by deepening of Acetabulum - decreases body weight lever arm Increase in neck length and Lateral reattachment of trochanter - lengthens abductor lever arm This decreases abductor force , hence joint reaction force, & so the wear of the implants.

36. BIOMECHANICS –HIP JOINT Joint reaction forces are minimal if hip centre placed in anatomical position Adjustment of neck length is important as it has effect on both medial offset & vertical offset

37. BIOMECHANICS –HIP JOINT OFFSETS: Vertical Height (offset) Determined by the Base length of the Prosthetic neck and length gained by the head Horizontal Offset (Medial offset) center of the head to the Axis of the stem IF…… Medial offset is inadequate -- shortens the moment arm -- limp, increase bony impingement Excessive medial offset – dislocation, increases stress on stem & cement -- stress fracture or loosening

38. BIOMECHANICS –HIP JOINT In regular THR , the Femoral component must be inserted in the same orientation as the femoral neck to achieve the rotational stability . Modular component in which stem is rotated independently of the metaphyseal portion Anatomical stems have a few degrees of ante version built into the neck

39. BIOMECHANICS –HIP JOINT Femoral components available with a fixed neck shaft angle 135º Restoration of the neck in ante version - 10-15º Increased ante version -- anterior dislocation Increased retroversion -- posterior dislocation Cup placed in 15 -20 degrees of ante version and 45 degrees of inclination

40. BIOMECHANICS –HIP JOINT HEAD DIAMETER : Large diameter head compared to Small head – Less prone for dislocation – Range of motion is more

41. THANK YOU