Subtrochanteric fractures are fractures of the hip below the greater and lesser trochanters. They are essentially fractures of the shaft of the femur up to 5 centimeters or less below the lesser trochanter. They account for up to 30 percent of fractures of the hip and can occur at many different age levels. This injury is already subjected to high forces from standing or walking on the leg.
The bone is highly compressed already, especially in the medial and posterior-medial parts of the femur. The bone has few blood vessels in this area so it tends to heal more slowly with a higher risk of nonunion than with other parts of the femur. There are several muscles which attach to this area that cause the fracture to deform when broken. This includes the gluteus muscle, the short rotator muscles and the psoas muscle.
The mechanisms of injury include low energy injuries in which the elderly person sustains a minor fall and breaks a weakened bone. High energy impacts can cause fractures in young people. This includes motor vehicle accidents, gunshot wounds, and falls from a great height. Pathological fractures from metastatic cancer or Paget’s disease cause up to 35 percent of all subtrochanteric fractures.
Evaluation of Subtrochanteric Fractures
Fractures occurring because of major trauma need a full trauma evaluation because of the high risk of other injuries. This includes a pelvic x-ray, a c-spine x-ray, and a chest x-ray as well as evaluation of airway, breathing, and circulation. Patients with this type of fracture cannot walk and have a painful hip. There can be swelling of the upper thigh. The area needs to be evaluated for open fractures and other soft tissue injury. Compartment syndrome can occur, which can affect circulation and nerve function to the lower leg. Hypovolemic shock can occur from excessive bleeding.
The thigh should be splinted until a definitive treatment can be undertaken. After splinting, the area should be evaluated for neurovascular compromise. X-ray of the front and side view of the leg should be taken and should show the fracture. The knee and the pelvis should be x-rayed at the same time as these can be injured as well. Other areas of possible injury should be x-rayed at the same time. In highly comminuted fractures, an scanogram of the opposite side should be done so the doctor can compare one femur length to another.
Classification of Subtrochanteric Fractures
There is a Fielding classification system that is based on the location of the fracture when compared to the lesser trochanter. The further away from the lesser trochanter, the higher the type of Fielding fracture up to type III, which is 2.5-5 cm below the lesser trochanter.
The Sensheimer classification system is based upon the displacement of the fracture and the number of fragments found within the fracture zone. The Russell-Taylor classification was once used but is obsolete.
Treatment of Subtrochanteric Fractures
Historically, subtrochanteric fractures were treated with traction followed by casting or bracing. The risk of malunion and nonunion were high with much shortening and rotation of the leg. Now, almost all subtrochanteric fractures are treated with surgery.
Choices of surgery include:
- An interlocking nail—these are used if there is a fracture in the subtrochanteric region with the area between the trochanters intact.
- A 95 degree fixed angle device—these are used when both trochanters are fractured. Screws are used as well as plate along the length of the femur.
- Sliding hip screw—this type of screw doesn’t work very well for these types of fractures
- Bone grafting—if this is used, it is slid in between the bony fragments at the fracture site before applying a plate to affix the fracture fragments.
- For open fractures—these are almost always caused by a motor vehicle accident. Surgical debridement and bony stabilization are recommended.
Complications of Subtrochanteric Fractures
Implant failure can occur with plate and screw device, and with interlocking nail devices. If this occurs, the hardware needs to be removed with the application of plates and or screws/nails with bone grafting.
Nonunion can occur, even with surgical intervention. The patient is unable to bear weight after 4-6 months and there is pain upon trying to bear weight. Nonunion usually involves fracture deformity of the leg. If nonunion happens when an intramedullary nail is placed and, when this happens, another intramedullary nail is introduced with reaming out of the bone again so that the nail fits better.
There may be leg length discrepancy, typical of malunion of the fracture. The leg can be rotated, even with surgery, if the surgeon is not aware of the potential for rotation of the leg at the time of surgery.
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