The basics – NOF Anatomy
The hip joint is a ball-and-socket joint between the femur and the pelvis (See diagram below). The upper (rounded) end of the femur is called the head, which is connected to the shaft of the femur by the neck. At the base of the neck are two bony lumps, the Greater Trochanter and Lesser Trochanter (for muscle attachments) The socket component of the joint known as the acetabulum which surrounds about 2/3rd the head of the femur.
Trauma to the hip
The most common cause is usually a minor stumble or fall in an elderly patient, although it is possible to fracture a femoral neck as part of more serious multiple trauma. The hip joint is similar to the shoulder joint, although not as mobile. However, it can withstand much greater stresses than the shoulder and is more stable and it takes a lot of force to dislocate it. Hence the neck is more likely to break than the joint is to dislocate, especially in elderly patients where the bones are weakened through degenerative changes such as osteoporosis. Another interesting fact I was told is that it is possible to cut all the ligaments and muscles connecting the femur with the pelvis and the joint would still stay in place!
Signs & symptoms
The symptoms are usually of pain in the groin area, worse on moving the hip joint or trying to weight-bear. I was told that the classic appearance of shortening and external rotation of the leg is not very common and only shows on a thin patient with a displaced fracture. The doctor did go through the mechanics of how this classic appearance occurs but lost me half way through his explanation! So I went to the clinical library & here are my findings for those purists who desperately want to know:
The shortening and external rotation is the result of abnormal pull of the muscles round the hip. The Iliopsoas muscle comes from the inside of the pelvis, crosses the front of the hip and pulls on the lesser trochanter which is slightly round the back of the medial side of the upper femur. Normally this flexes the hip joint because the whole femur moves in one piece. If the neck of the femur is broken the muscle just pulls the lesser trochanter forwards and twists the femoral shaft into external rotation. The short stabilizing Gluteus Medius and Gluteus Minimus muscles, from the outer pelvis to the greater trochanter, pull up on the now free femoral shaft, resulting in shortening.
Types of NOF Fractures
Fractures of the femoral head occur in one of three sites:
(1) Subcapital fracture which is across the neck of the femur immediately below the head.
The most common cause is usually a minor stumble or fall in an elderly patient, although it is possible to fracture a femoral neck as part of more serious multiple trauma. The hip joint is similar to the shoulder joint, although not as mobile. However, it can withstand much greater stresses than the shoulder and is more stable and it takes a lot of force to dislocate it. Hence the neck is more likely to break than the joint is to dislocate, especially in elderly patients where the bones are weakened through degenerative changes such as osteoporosis. Another interesting fact I was told is that it is possible to cut all the ligaments and muscles connecting the femur with the pelvis and the joint would still stay in place!
Signs & symptoms
The symptoms are usually of pain in the groin area, worse on moving the hip joint or trying to weight-bear. I was told that the classic appearance of shortening and external rotation of the leg is not very common and only shows on a thin patient with a displaced fracture. The doctor did go through the mechanics of how this classic appearance occurs but lost me half way through his explanation! So I went to the clinical library & here are my findings for those purists who desperately want to know:
The shortening and external rotation is the result of abnormal pull of the muscles round the hip. The Iliopsoas muscle comes from the inside of the pelvis, crosses the front of the hip and pulls on the lesser trochanter which is slightly round the back of the medial side of the upper femur. Normally this flexes the hip joint because the whole femur moves in one piece. If the neck of the femur is broken the muscle just pulls the lesser trochanter forwards and twists the femoral shaft into external rotation. The short stabilizing Gluteus Medius and Gluteus Minimus muscles, from the outer pelvis to the greater trochanter, pull up on the now free femoral shaft, resulting in shortening.
Types of NOF Fractures
Fractures of the femoral head occur in one of three sites:
(1) Subcapital fracture which is across the neck of the femur immediately below the head.
(2) Trans-cervical fracture which usually about halfway down the neck. Like the subcapital fracture, if this fracture is displaced, the head of the femur is likely to lose its blood supply and results in necrosis and crumbling of the head later on. For this reason, a lot of these fractures are treated by replacement of the head by a metal implant, rather than trying to put together a fracture which will not heal and then collapse.
(3) Inter-trochanteric fracture which runs diagonally between the two trochanters. The area has an excellent blood supply and fractures here are unlikely to affect the viability of the head. They are usually treated by internal fixation, often with very good results.
Any of the above fractures may be undisplaced, grossly displaced or impacted. Apparently, injury to nerves and vessels is usually very rare.
So there you have it the first week is over but stayed tuned……..
So there you have it the first week is over but stayed tuned……..
1 comment:
Well done - great post giving lots of good background info. Emma
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