The hip- Palastanga Flashcards
Classification
Synovial ball and socket
Direction of articular surfaces
Consequences?
Acetabulum- lat ant and inf
Hear of femur- med ant and sup
Loss of coincidence of articular surfaces- anterosuperior aspect of femoral head is not contained within acetabulum but exposed
What is the acetabular notch?
A deficiency in the acetabular rim, anteriorly, compensated for by the transverse ligament
How is congruency of the joint increased?
Acetabular labrum (wedge shaped fibrocartilage)
Where on the femoral head is the cartilage thickest and why?
Superior surface as sustains greatest pressure during loading
(Cartilage is almost spherical in an unloaded femur
Describe the joint capsule
Very strong and thickest anteriorly
Attaches to the margins of the acetabulum and the transverse ligament
Attaches to the intertrochanteric line ant and neck of the femur post
What are the capsular ligaments
Iliofemoral (strong and triangular, anteriorly)
Pubofemoral (blends with inf band of above, sits anteroinferiorly)
Ischiofemoral (less well defined, spirals laterally and upwards)
Role of the capsular ligaments
Limit extension, relax under flexion and are moderately taut during stance
Intracapsular sturctures
Transverse ligament
Labrum
Ligamentum teres (thin band of connective tissue attaching to the fovea of the head of the femur)
How does the hip receive its blood supply?
Lateral and medial circumflex femoral arteries, obturator artery and gluteal arteries form a peri-articular anastamosis
Stability
Articular surfaces fit well together however as transfers weight to lower limb peri-articular muscles (esp those crossing transversely) are essential to maintain stability
What happens to the femoral shaft during embryo and post-natally
Becomes adducted and medially rotated angulating the the head and neck against the shaft in both the frontal and lateral plains
What is the angle of inclination in an adult
Around 125 degrees
What is the angle of anteversion in an adult
About 10 degrees
Difference in mechanical axis to vertical
Difference in anatomical axis to mechanical axis
Difference in anatomical axis to vertical
3 degrees
3 degrees
6 degrees
What occurs during hip dislocation
Most commonly posterior displacement of femoral head
Limb is shortened, adducted and medially rotated
What is the position of the limb during hip fracture
Shortened and laterally rotated
Limits to flexion of the hip
Is free
Limited by contact with the body wall when knee flexed
Limited by tension in hamstrings when knee extended
Range of hip flexion
120 degrees without assistance
145 degrees with pulling in
Limits to extension
Shape of the articular surfaces and associated ligaments
Range of extension
20 degrees without assistance
30 degrees if leg pulled on
Abduction and adduction are?
Free
Greatest with the hip flexed
Some 45 degrees each
Limited by tension in opposite muscles
Rotation occurs around what axis?
The mechanical axis of the femur
not the shaft
Range of lateral rotation
60 degrees
the freer and more powerful movement
Limits to lateral rotation
The medial rotators of the thigh
Iliofemoral and pubofemoral ligaments
Range of medial rotation
30 degrees
Limits to medial rotation
Thigh lateral rotators
Ischiofemoral ligament
Estimation of hip joint forces during one-legged standing
1.8 to 3 times body weight
Estimation of hip joint forces during stance phase of walking
3.3 to 5.5 times body weight
What do trabeculae do?
Minimise bending and shear stresses
What are the trabecular systems of the pelvis
2, arising from the inferior and superior auricular articular surface of SI joint, coursing through the pelvis where they cross over and continue into the femoral head via the acetabulum
(So that from sup auricular surface becomes inf femoral and vice versa)
Describe the accessory trabecular patterns of the (top of the) femur
Trochanteric bundle arising from the cortical layer of the medial aspect of the shaft (so essentially in the middle)
Second bundle entirely with the greater trochanter
What happens to the joint contact area under increasing load
It increases
What happens if load-bearing area of femoral head is decreased? e.g. due to deformity
The rest of the load bearing cartilage is under greater stress (non-physiological) and may degenerate at a higher rate
Muscles extending the hip joint
Gluteus maximus
Hamstrings
Muscles abducting the hip joint
Gluteus minimus and medius mainly
Gluteus maximus and tensor fascia lata assist
Muscles adducting the hip joint
Adductors magnus, longus and brevis
Gracilis
Pectineus
Muscles flexing the hip joint
Iliopsoas
Pectineus
Rectus femoris
Sartorius
Muscles medially rotating the hip joint
Gluteus medius and minimus (anterior parts)
Tensor fascia lata and iliopsoas assist
Muscles laterally rotating the hip joint
Gluteus maximus Piriformis Obturators internus and externus The gemelli (sup and inf) Quadratus femoris
Describe nutation
Rotates forwards
- forwards movement and lowering of the scaral promontory (so cocyx moves back and elevates)
- separation of the ischia
- decreases pelvic inlet dimensions
- increases pelvic outlet dimensions
Describe counternutation
Vertical integration of the sacrum (rotates backwards)
- backward movement and elevation of the sacral promontory (so cocyx moves forward and lowers)
- increases pelvic inlet dimensions
