In diagnosis of a distal femur fracture it must first be determined whether or not there is an articular injury. In order to determine this, traction radiographs and/or CT scans with 3D reconstruction are helpful. In a nonarticular injury, the key challenges will be reduction against deforming forces and fixation of the distal femoral block (particularly in osteoporosis).
If it is determined that there is an articular injury, such an injury must be further characterized. A partial articular injury may be associated with significant ligamentous injury. MRI is helpful to investigate this. Other challenges with partial articular injuries include surgical access (eg, posterior Hoffa fractures) and fixation of relatively small osteochondral fragments.
In the complete articular fracture, the surgeon must ask additional questions: is the intraarticular involvement simple, or multifragmentary? If the articular involvement is multifragmentary, where is that involvement (eg, medial or lateral Hoffa/frontal plane fracture)? Challenges with the complete articular fractures include obtaining appropriate surgical access to the articular injury while preserving the natural healing capacity of the metaphyseal zone. Additionally, fixation of short distal segments in osteoporosis presents further challenges.
2. Patient assessment
The distal femoral fractures have two age groups which it commonly occurs in.
The young healthy high energy trauma patient
The elderly osteoporotic low energy trauma patient who fell
These two patients present I very different ways. The young healthy patient often has an open fracture with high energy comminution in good bone while the elderly patient presents with a comminuted fracture with very osteoporotic bone.
The young healthy patient needs to be completely worked up as a trauma patient and cleared as a trauma patient before surgery.
The elderly patient often will need a complete medical workup because of many geriatric medical issues.
The young healthy patient may have a distal neurovascular compromise while the elderly patient usually would not.
The young healthy patient will often present with open fractures which requires antibiotics, while the elderly patient would not need antibiotics but need medical support.
3. Physical exam
Distal neurovascular status must carefully be tested. Generally, the low energy trauma patient will have no problems with function, but the high energy trauma patient may have loss of vessel or nerve integrity. If this is the case, then a CT angiogram is the test of choice for determining vascular integrity.
If a patient has a distal femur fracture, it is very difficult to assess for ligamentous knee injury until after the fracture has been stabilized.
4. X-ray images
The distal femur is best visualized with AP and lateral distal femoral images.
The young trauma patient with a high energy distal femur fracture may also have other associated injuries such as patella, femoral neck, and acetabular fractures.
The distal femur fracture in the elderly patient may be an insufficiency fracture which is part of a previous history of multiple
presentations for other osteoporotic injuries.
5. CT images
All distal femur fractures require CT images as up to 20% will have intra articular extension creating a need for multiple approaches and fixation techniques.
The Hoffa fractures are commonly missed on plain imaging but is picked up on the CT scan.