69 - Joints of the Hip Complex Flashcards
Location of fat pad within hip joint
Intra-articular but extra-synovial
Name for socket of hip joint
Acetabulum
Where do the ileum, ischium and pubis join?
Within the acetabulum.
Two parts of the acetabulum
Weight bearing area (exterior, horseshoe shape)
Non-weight-bearing (acetabular notch and fossa, trabecular bone)
Role of fat pad
Spreads synovial fluid in joint, shock absorption
Two lumps of bone either side of anatomical neck of femur
Lesser and greater trochanters
Depression in the head of femur
Fovea
Role of fovea of femur
Ligament attaches to acetabulum of hip.
Name of holes around neck of femur
Vascular foraminae
Attachment of capsule on femur
Around area near greater and lesser trochanters anteriorly.
Posteriorly attaches more proximally.
Role of greater and lesser trochanters of femur
Traction epiphises, where tendons attach.
Intertrochanteric line
Area where capsule attaches to femur anteriorly
Pressure epiphysis of femur
Near head of femur.
Perthes’ disease
Avascular necrosis of head of femur from disruption of blood supply.
Leads to interruption of pressure epiphysis near head of femur.
Femoral head and neck
1
2
3
- Head of femur 2/3 of sphere – directed upwards, medially & anteriorly – therefore anterior part lies outside acetabulum, protected by (psoas) bursa
- Head of femur articulates with roof of acetabulum (area of thickest cartilage)
- Mid-region of femoral neck narrower than circumference of head – gives joint greater ROM without contacting rim of acetabulum
Bony architecture of proximal femur
1
2
•Trabecular system – 2 systems that intersect:
- Superior: medial & arcuate – Due to compression through head & neck from gravity
- Inferior: medial & lateral – Run between trochanters, in response to muscle pulls on greater & lesser trochanters
Area of relative weakness of femur
Mid-neck.
Where trabecular bones don’t align.
Fractures associated with falls in the elderly.
Normal angle between head of femur and body in adults (neck-shaft angle)
~135 degrees
Normal angle between head of femur and body in a newborn
Over 150 degrees
Role of neck-shaft angle of femur
Enables femur to swing free of pelvis in locomotion
Pathologically increased neck-shaft angle of femur
Coxa valga
Pathologically decreased neck-shaft angle of femur
Coxa vara
Angle of torsion of femur
About 15 degrees.
Angle between head of femur (tilted anteriorly) and body of femur.
Effect of increasing torsion angle of femur
Priority is to get the head of the femur back into the socket.
Can compensate with other joints, EG going pigeon toed, medially rotating femur
Effect of coxa vara in adolescence
Coxa vara increases stress on femoral neck.
Increased shear forces on femoral head can cause proximal femoral epiphysis to break off.
Leads to ‘slipped capital femoral epiphysis.’
During standing, where does the line of gravity pass, relative to the hip joint?
Passes behind hip
Position of greatest hip stability
Extension, abduction, medial rotation.
Ligamentous support of hip joint 1 2 3 4 5
- Capsule attaches at base of long neck
- 3 ligaments: strong iliofemoral ligament in front, weaker behind (pubofemoral & ischiofemoral) ligaments – latter blend with capsule not directly to femur). Lined by synovial membrane.
- Maximum stability in extension – due primarily to iliofemoral ligament - spirals & tightens with hip extension
- Lined internally by ring of fibres – ‘zona orbicularis’
- Posterior capsule does not extend as far distally –no limit to extension
Three ligaments supporting hip joint
Strong iliofemoral ligament in front Weaker behind (pubofemoral & ischiofemoral) ligaments latter blend with capsule not directly to femur). Lined by synovial membrane.
Why is the iliofemoral ligament the strongest of those supporting the hip?
Line of gravity passes behind hip joint, so iliofemoral (anterior) needs to be the strongest
What do pubofemoral and ischiofemoral ligaments attach to?
Blend with capsule of hip joint
Intra-articular surfaces of hip joint
Labrum – bridges acetabular notch, triangular, deepens cup & increases surface area - often torn in hip injury
*posterior dislocation
Ligament of head of femur – has no supporting role - directs branch of obturator artery to femoral head (regresses after puberty)
Role of labrum in hip joint
bridges acetabular notch, triangular, deepens cup & increases surface area
Injury in which labrum of hip joint is particularly vulnerable
Posterior dislocation
Role of ligament of head of femur
Has no supporting role - directs branch of obturator artery to femoral head (regresses after puberty)
Attachments of ligament of head of femur
Notch at front of acetabular region to fovea of femur.
Name for reflections of fibrous tissue from capsule of hip joint to femoral head
Retinacular fibres
What do retinacular fibres contain?
Retinacular vessels.
These are critical for blood supply to the head of the femur.
When are the retinacular vessels endangered?
Injury to neck of femur
Primary movements of hip joint
Flexion and extension
What is medial rotation of hip joint associated with?
Extension of hip joint (locks joint)
Primary hip flexor
Iliopsoas (combination of psoas major and iliacus)
Most powerful hip extensor
Gluteus maximus
Muscles involved in adducting femur
Adductor muscles
Role of gluteus medius and minimus
Abductors at hip.
Maintain position of pelvis in coronal plane (from below), by contracting on side of weight-bearing limb to prevent unsupported side of pelvis from dropping.
Movements from gluteus medius
Both flexion and extension
Name for gait from damage to gluteus medius and minimus
Trendellenberg gait.
Hilton’s law
Joint receives pain & proprioceptive fibres from branches to muscles that move the joint – also pass to overlying skin
Nerves innervating hip joint
1
2
3
Hip joint innervated by articular branches of femoral, obturator & gluteal nerves
Referred pain from hip
Knee or medial thigh (from compression of obdurator nerve)
Referred pain to hip
From lumbar spine
Blood supply of the hip joint
1
2
3
- Via anastomoses between branches of medial (primarily) and lateral femoral circumflex arteries (normally off profunda femoris)
- Small supply from artery of head of femur (regresses after puberty)
- Retinacular vessels pass across femoral neck, bound down by ‘retinacular’ fibres (from capsule)
Main role of femoral artery
Takes blood from pelvis to back of the knee
Two branches from femoral artery that supply hip joint
Medial and lateral femoral circumflex arteries
Posture of fractured neck of femur
Muscle spasm causes external rotation and shortening of limb
Structures along anterior of hip
Femoral artery
Structures along posterior of hip
Sciatic nerve, medial to head of femur
Structure endangered with a traumatic hip dislocation
Sciatic nerve (often associated with fractured posterior lip of acetabulum)
Why is early re-articulation of traumatic hip dislocation important?
Disruption of blood supply can lead to necrosis
Congenital hip dislocation
Shallow acetabulum (developmental dysplasia). If not treated, a false joint can form above the acetabulum
