session 2 Flashcards
The hip The gluteal region The posterior thigh
Name the three main extracapsular ligaments of the hip joint and state their function
Iliofemoral – prevents hyperextension of the hip in the standing position.
Pubofemoral–prevents excessive abduction and extension of the hip
Ischiofemoral – prevents excessive internal rotation of the hip
All three ligaments provide stability to the hip joint by pulling the femoral head into the acetabulum.
Why, anatomically, is hip extension limited to only about 15°?
Because the anteriorly-placed, very strong, iliofemoral ligament becomes taught in extension of the hip joint and thereby prevents hyperextension beyond 15°.
Describe the anatomical attachments of the capsule of the hip joint
Proximally, the capsule of the hip joint it attaches to the edge of the acetabulum, 5-6mm outside the acetabular labrum. Distally, it attaches to the intertrochanteric line of the femur anteriorly and the femoral neck posteriorly.
Why does a displaced intracapsular fracture of the femoral neck carry a high risk of avascular necrosis?
Displaced intracapsular fractures are likely to tear the ascending cervical (retinacular) branches of the medial femoral circumflex artery. Due to the inability of the artery of the ligamentum teres to sustain the metabolic demand of the femoral head, there is a high risk of avascular necrosis of the bone.
Why is the risk of avascular necrosis of the femoral head much lower for an intertrochanteric fracture than for an intracapsular fracture?
An intertrochanteric fracture is external to site of attachment of the capsule, leaves the retinacular arteries undisturbed and therefore does not disrupt the blood supply of the femoral head.
What are the functions of the Gluteus Maximus muscle
Glut max is the main extensor of the thigh and also assists with lateral (external) rotation. As a powerful extensor of the hip joint, the glut max is suited to powerful lower limb movements such as stepping onto a step, climbing or running but is not used much during normal walking. Glut max and the hamstrings work together to extend the trunk from a flexed position by tilting the pelvis backwards, for example standing up from a sitting position. The superior fibres of the glut max can assist in extension of the knee through their attachment to the iliotibial tract.
What are the functions of the Iliotibial tract?
The iliotibial tract is a specialised condensation of the fascia lata which extends from the iliac crest to the lateral tibial condyle just below the knee. Traction on the iliotibial tract in the standing position helps to stabilise the hip joint in extension and, by ‘hoisting’ the iliotibial tract and fascia lata upwards, it also helps to stabilise the knee joint (by steadying the femoral condyles on the articular surfaces of the tibia).
Which ligaments convert the greater and lesser sciatic notches into foramina?
What is the role of these ligaments in the erect posture (standing upright)?
- Sacrospinous and sacrotuberous ligaments.
- In the erect position, these ligaments limit rotation of the inferior part of the sacrum during transmission of weight of the body down the vertebral column.
What bony landmarks are used to determine the course of the sciatic nerve i) as it leaves the pelvic cavity, and ii) as it enters the thigh? iii) Which traumatic injury to the hip joint is most likely to damage the sciatic nerve?
i) The sciatic nerve emerges horizontally from the pelvic cavity mid-way between the posterior superior iliac spine and the ischial tuberosity.
ii) It then descends into the thigh vertically at the mid-point between the ischial tuberosity and the greater trochanter.
iii) Posterior dislocation of the femoral head from the acetabulum (usually sustained in a road traffic collision when the knee impacts on the dashboard) can stretch the sciatic nerve.
Define Right-sided positive Trendelenburg sign
When the patient weight-bears on his right leg and lifts his left foot off the floor, the left side of his pelvis will tilt inferiorly
Why would damage to the superior gluteal nerve cause a positive Trendelenburg sign?
In normal function, the pelvis is held stable in horizontal alignment by gluteus medius and minimus acting as abductors of the weight-bearing hip.
The superior gluteal nerve supplies gluteus medius and minimus. If these muscles are weak, the pelvis will droop on the unsupported side. This is a positive Trendelenburg sign.
Why doesn’t damage to the inferior gluteal nerve cause a positive Trendelenburg sign?
The inferior gluteal nerve supplies gluteus maximus. This muscle is a powerful extensor of the hip joint during activities such as brisk walking, running and standing up from a seated position; it is not an abductor of the hip.
Where do the gluteal nerves originate from? What are their root values?
The superior and inferior gluteal nerves originate from the sacral plexus.
- superior gluteal nerve: L4, L5, S1
- inferior gluteal nerve: L5, S1, S2
What course do the gluteal nerves follow to reach the muscles they innervate?
They both leave the pelvis via the greater sciatic foramen. The superior gluteal nerve passes superior to the piriformis muscle to innervate gluteus medius and minimus, whilst the inferior gluteal nerve passes inferior to the piriformis muscle to innervate gluteus maximus.
What types of activities are most likely to result in a pulled hamstring?
A pulled hamstring tends to occur during sudden muscular exertion that results in stretching of the posterior thigh muscles e.g. jumping, sprinting and lunging. It is relatively common in footballers and athletes, especially if proper warm-up exercises have not been performed beforehand.
