Applied Anatomy of Bones & Joints of Lower Limb
Understand the concepts & associated principles, functional & clinical applications of:
1. The site, mechanism and effects of:
(i)
fracture of neck of femur (with particular reference to the blood supply of head of
femur):
The following proximal femur fractures are commonly referred to as 'hip fractures':
Femoral head fracture denotes a fracture involving the femoral head. This is usually the result of
high energy trauma and a dislocation of the hip joint often accompanies this fracture.
Neck of Femur (NOF) fracture, denotes a fracture adjacent to the femoral head in the neck between
the head and the greater trochanter. These fractures have a propensity to damage the blood supply
to the femoral head.
Intertrochanteric fracture denotes a break in which the fracture line is between the greater and
lesser trochanter on the intertrochanteric line. It is the most common type of 'hip fracture' and
prognosis for bony healing is generally good if the patient is otherwise healthy.
Blood Supply:
The nutrient artery supplying the femoral head is not sufficient in adults to maintain bone health,
and the circumflex femoral arteries (which enter the femur lower down) are required to provide
adequate blood supply. The medial and lateral circumflex femoral arteries are usually branches of
the deep artery of the thigh, but may arise directly from the femoral artery. Articular arteries of the
hip joint come from branches of the medial and lateral circumflex femoral arteries that travel in the
retinacula (reflections of the capsule along the neck of the femur toward the head). These provide the
main blood supply to the hip joint. Hence if these circumflex arteries are lacerated during the
fracture, avascular necrosis may occur to the head of femur. This process will severely limit the
healing process.
Obturator Artery is a branch of the internal iliac artery, which helps the deep artery supply the
adductor muscles of the thigh. It passes through the obturator foramen to the thigh and then divides
into anterior and posterior branches that anastamose. The posterior branch gives of an acetabular
branch that supplies the head of the femur.
A notable complication of overt fractures of femoral neck or pelvis: pulmonary embolism and
pneumonia.
(ii) fracture of shaft of femur (noting the vessels endangered).
Subtrochanteric fracture involves the shaft of the femur immediately below the lesser trochanter
and may extend down the shaft of the femur.
A Shaft of Femur fracture can occur at any point down to the knee joint.
The deep femoral artery (or profunda femoris artery) branches off the lateral surface of the
femoral artery (gives rise to the femoral circumflex arteries). It supplies blood to the ventral and
lateral regions of the skin and deep muscles of the thigh, and is particularily subject to laceration as it
runs parallel to the shaft of femur. Significant blood loss (1-1.5L) can result into the large thigh
compartment.
2. The site, mechanism and effects of:
(i) fracture of shaft of tibia (noting why it is often compound)
Tibia fractures can occur at any point along the tibia, but are generally separated into three
categories based on the location of the fracture.
Tibial Shaft Fractures
Tibial shaft fractures are the most common type of tibia fracture and occur between the knee and
ankle joints. Most tibial shaft fractures can be treated in a long leg cast. However, some fractures
have too much displacement or angulation and may require surgery to realign and secure the bones.
Tibial Plateau Fractures
Tibial plateau fractures occur just below the knee joint. These fractures require consideration of the
knee joint and its cartilage surface.
Tibial Plafond Fractures
Tibial plafond fractures occur at the bottom of the shin bone around the ankle joint. These fractures
also require special consideration because of the ankle cartilage surface. Tibial plafond fractures are
also concerning because of potential damage to surrounding soft-tissues.
As the shin bone lies subcutaneously, it is prone to compound fractures. These are open fractures
where the fractured bone is open through the skin. These fractures are at especially high-risk of
developing an infection, and generally require surgical treatment in all cases.
(ii) fracture of shaft of fibula
The fibula is important as a site for the attachment of muscles that move the foot and toes. In
addition, the distal tip of the fibula extends lateral to the ankle joint. This fibular process, the lateral
malleolus, provides lateral stability to the ankle.
As it is not a weight bearing bone, it is less likely to be injured. If it is, it will usually heal quickly (912wks), except if the injury is to the distal portion where the fibula is involved in the ankle joint.
(iii) stress fracture of a metatarsal (noting why the second metatarsal is the most vulnerable).
Stress fractures are hairline fractures that develop in bones subjected to repeated shocks or impacts.
Stress fractures of the foot usually involve one of the metatarsal bones.
The second and third metatarsals are relatively fixed in position within the foot; the first, fourth, and
fifth metatarsals are relatively mobile. More stress is placed on the second metatarsals during
ambulation; thus, these bones are at increased risk for stress fractures.
Symptoms include:
Acute pain
Rapid swelling
Inability to weight bear
There may be deformity in the foot
3. The mechanism and diagnosis of congenital dislocation of the hip.
Infants with congenitally dislocated hips have a limited abduction of the hip of 20% or less,
compared to 90% bilateral abduction normally.
Congenital dislocation of the hip may be diagnosed by pushing and pulling the femur in relation to
the pelvis. With one hand, apply traction to the femur at the level of the knee. With the other hand,
stabilise the pelvis and place your thumb on the greater trochanter. It is possible to feel the greater
trochanter move distally when this pressure is applied, and when the femur is returned.
4. The Trendelenburg Test and the causes of a positive test.
The procedure is designed to evaluate the strength of the gluteus medius muscle. It is taken by
observing if the dimples overlying the PSIS, which should be level when the patient is bearing weight
evenly across both legs. When then asked to stand on one leg, the gluteus medius muscle on the
supported side should contract as soon as the leg leaves the ground, and should elevate the pelvis on
the unsupported side (negative Trendelenburg sign).
If the pelvis on the unsupported side remains in position or descends, the gluteus medius muscle on
the supported side is either weak of non-functioning (positive Trendelenburg sign).
5. The mechanism and structure endangered in posterior dislocation of the hip.
This dislocation occurs commonly in MVAs. As the femoral head is situated posterior to the
acetabulum, it is prone to dislocation during a MVA involving rapid deceleration. If the knees strike
the dashboard they can transmit the force through the femur to the hip. If the leg is extended and the
knee is locked, force can be transmitted from the floorboard though the entire lower and upper leg to
the hip joint.
Internal rotation and shortening of the leg is characteristic of posterior dislocation. The sciatic nerve
is particularily prone to injury (10% of cases). This should be assessed immediately, and if the
patient is unconscious then tendon reflexes should be tested.
6. Why pain in the knee may be due to hip joint pathology.
Hip joint pathology can refer pain above or below the site of injury if nerves are involved. This is
known as Hilton’s Law: ‘a nerve that innervates a joint also tends to innervate the muscles that move
the joint and the skin that covers the distal attachments of those muscles’. Pain can therefore be felt
in the knee. If the immediate site of injury cannot be located in a painful knee, then pain there should
be treated as referred from another structure, e.g. hip.