Distal femur fractures occur when the thighbone (femur) breaks just above the knee joint.
These types of fractures occur most commonly in older people whose bones are weak. When they occur in younger patients it is often the result of a high-energy injury such as a car crash. In both of these cases, the breaks may extend into the knee joint and may shatter the bone into several pieces.
The knee is the largest weight bearing joint in the body. The distal femur makes up the top part of the knee joint. The upper end of the tibia (shinbone) supports the bottom part of the knee joint. The ends of the femur are covered in a smooth surface called articular cartilage which protects and cushions the bone and helps it glide as the knee is bent and straightened.
Types of Distal Femur Fractures
Distal femur fractures can be categorised in the way in which the bone breaks and the severity of the break.
Causes Of Distal Femur Fractures
Fractures of the distal femur most commonly occur for two different reasons in two patient types; younger patients (under 50) and the elderly.
When these types of fractures occur in younger patients it is usually caused by a high-energy injury such as a fall from a significant height or a car accident. Due to the forceful nature of these fractures often the fracture will be accompanied by other injuries.
When distal femur fractures occur in the elderly, it is generally a result of degenerative bone quality that have become weak and fragile. A lower force injury such as a fall from standing can cause a distal femur fracture in an older person.
Distal Femur Fracture Signs and Symptoms
In most cases the symptoms will be felt around the knee joint but they may also extend to the thigh area. The most common symptoms of compound distal femur fractures include:
A distal femur fracture is confirmed with x-rays to assess the severity of the injury and any associated injuries.
Surgery is recommended as the best course of action following a compound distal femur fracture in order to both stabilise the bone and joint and to minimise the risk of infection.
Complex fractures require open reduction and internal fixation.
The internal fixation methods include:
Both of these methods can be performed using one large incision or several smaller ones depending on the type of fracture and its severity.
If the fracture has broken the bone into many small pieces above the knee joint, it is generally not pieced back together but rather a plate or rod will be fixed at both ends of the fracture without touching the multiple small pieces. This method keeps the overall shape and length of the bone in its natural form while it heals. As it heals, the individual pieces will then grow into the new bone which forms a callous.
In cases where the fracture may be slow to heal, such as when the patient is elderly with poor bone quality, a bone graft may be used to help facilitate the callous forming. Bone grafts can be obtained from the patient themselves (usually taken from the pelvis) or cadaver bone taken from a tissue or bone bank. Alternatively artificial bone fillers can be used.
In extreme cases where the fracture is too complicated and the bone quality too poor to fix, the fragments are removed ant the bone is replaced with a knee replacement implant.