Fractures of the distal femur may be extraarticular or have an intraarticular component. Mismanagement of any of these fractures can result in abnormalities of alignment of the load-bearing axis of the lower limb and/or rotational deformities. These can have profound biomechanical consequences.
Additionally, the intraarticular fractures can result in joint irregularities leading to degenerative joint disease.
Treatment is based on sound bone healing with full restoration of the biomechanical axes and of the joint surfaces.
Accurate diagnosis and categorization of the injury anatomy leads to a full understanding of the repertoire of treatment methods, wise surgical decision making and improved outcomes.
2. General comments regarding distal femoral fractures
Distal femoral fractures generally fall into one of two groups:
Fractures which result from high energy trauma in young adults and which may be associated with significant articular injury, extensive devitalization of the fracture site and potential ligamentous disruption of the knee.
Fractures which result from low energy trauma, or falls, in the elderly osteoporotic patient and which are characterized by comminution in the metaphyseal area and articular injuries which may be so severe as to render them potentially unreconstructable.
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 these 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.
3. Pathological fractures
Occasionally, fracture severity may be worse than anticipated or the fracture may have been sustained after relatively trivial trauma. The surgeon should make sure that a pathological fracture has not occurred. An example of a pathological fracture would be a giant cell tumor of bone, as illustrated here.
Careful inspection of radiographs is imperative. Further imaging, such as CT scans, or MRI, is useful before fracture fixation is attempted. If the fracture looks unusual at the time of fixation a preliminary biopsy must be taken. It may be necessary to screen the patient for metabolic bone disease, or a primary malignancy at a remote site.
4. Example of a pathological fracture: chondrosarcoma
In this pathological fracture of the distal femur, note the lucency in the region of the fracture, the periosteal destruction and elevation of the periosteum. A biopsy of this lesion showed it to be a chondrosarcoma. This pathological fracture should be referred to a orthopedic surgeon with special expertise in oncology, tumor surgery and skeletal reconstruction.