Hip fracture

Overview
A hip fracture is a fracture in the proximal end of the femur (the long bone running through the thigh), near the hip joint.

The term "hip fracture" is commonly used to refer to four different fracture patterns and is often due to osteoporosis; in the vast majority of cases, a hip fracture is a fragility fracture due to a fall or minor trauma in someone with weakened osteoporotic bone. Most hip fractures in people with normal bone are the result of high-energy trauma such as car accidents.

The mortality following a hip fracture is between 20% and 35% within one year in patients aged 82 ± 7 years old, of which 80% were women.

Types
Many subtypes of fractures about the hip joint are colloquially known as 'hip fractures'. Although a true hip fracture involves the joint, the following four proximal femur fractures are commonly referred to as 'hip fractures'. The differences between them are important because each is treated differently.
 * 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.
 * Femoral neck fracture (sometimes Neck of Femur  (NOF), subcapital, or intracapsular 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, potentially causing avascular necrosis.
 * 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.
 * Subtrochanteric fracture actually involves the shaft of the femur immediately below the lesser trochanter and may extend down the shaft of the femur.

Incidence
Approximately 320,000 hospitalizations occur each year due to hip fractures in the US.

Pathogenesis/risk factors
Most hip fractures occur as a result of low-energy falls in elderly patients. Falls are uncommon in young adults due to better balance and strength and when they do occur, they usually do not cause the "hip fracture" pattern of injury that is commonly seen in the elderly. It was formerly thought, but Harvard medical scientists disproved, that benzodiazepine use increased the risk. A person with normal hips will not fracture following a fall from standing. Hip fracture following a fall is likely to be a pathological fracture. The most common causes of weakness in bone are:


 * Osteoporosis. Hip fractures are one of the most serious complications of osteoporosis; in fact a measure of success or failure of treatment of osteoporosis is the proportion of patients who sustain a hip fracture. There was a 43% reduction in hip fractures by vitamin D and calcium supplementation, and vitamin D defiency being a common problem [].
 * Homocysteine, a toxic 'natural' amino acid linked to the cause of heart disease, stroke and bone fractures, reduced by B-vitamins in this study, it reduced the amount of hip fractures by 80% after 2 years. This was despite no differences in bone density and in the number of falls between the vitamin and the placebo groups.
 * Other metabolic bone diseases such as Paget's disease, osteomalacia, osteopetrosis and osteogenesis imperfecta. Stress fractures may occur in the hip region with metabolic bone disease.
 * Benign or malignant primary bone tumours are rare causes of hip fractures.
 * Metastatic cancer deposits in the proximal femur may weaken the bone and cause a pathological hip fracture.
 * Infection in the bone is a rare cause of hip fracture.

Another element in the risk of sustaining a hip fracture is the risk of falling. Fall prevention is an area if interest with concerns in the area of providing a safe environment for people at risk, custodial care, walking aids, medication issues etc. Hip protectors are padded plastic shields that can be placed over the trochanters of people at risk of falling or of sustaining a fragility fracture. However, they are not effective in reducing the likelihood of a hip fracture and compliance is poor.

Natural history
Hip fractures are very dangerous episodes especially for elderly and frail patients. The risk of dying from the stress of the surgery and the injury in the first few days is about 10%. If the condition is untreated the pain and immobility imposed on the patient increase that risk. Problems such as pressure sores and chest infections are all increased by immobility. The prognosis of untreated hip fractures is very poor.

Clinical features
The classic clinical presentation of a hip fracture is an elderly patient who sustained a low-energy fall and now has pain and is unable to bear weight. On examination, the affected extremity is often shortened and externally rotated.

Investigations
X-rays of the affected hip usually make the diagnosis obvious; AP and lateral views should be obtained.

In situations where a hip fracture is suspected but is not obvious on x-ray, a CT scan with 3D reconstruction may be helpful. MRI has gained importance in the diagnosis of occult fractures of the femoral neck. Within 24 hours changes can be seen on MRI. Bone scan is less useful because it may take up to 1 week to demonstrate changes especially in the elderly.

As the patients most often require an operation, full pre-operative general investigation is required. This would normally include blood tests, ECG and chest x-ray.

Femoral neck fracture
Femoral neck fractures involve the narrow neck between the round head of the femur and the shaft. This fracture often disrupts the blood supply to the head of the femur.

Garden classified this fracture into four types:
 * Type 1 is a stable fracture with impaction in valgus.
 * Type 2 is complete but non-displaced.
 * Type 3 is displaced (often rotated and angulated) with varus displacement but still has some contact between the two fragments.
 * Type 4 is completely displaced and there is no contact between the fracture fragments.

The blood supply of the femoral head is much more likely to be disrupted in Garden types 3 or 4 fractures.

Surgeons may treat these types of fracture by replacing the fractured bone with a prosthesis arthroplasty. Alternatively the treatment is to reduce the fracture (manipulate the fragments back into a good position) and fix them in place with three metal screws.

A serious but common complication of a fractured femoral neck is avascular necrosis. The vasculature to the femoral head is easily disturbed during fractures or from swelling inside the joint capsule. This can lead to strangulation of the blood supply to the femoral head and death of the bone and cartilage.

Intertrochanteric fracture
Intertrochanteric fractures occur between the greater and lesser trochanters. They are usually fixed with a sliding hip screw and plate. Healing is usually good when the patient is healthy.