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Distal femur fractures invole the distal metaphyseal-diaphyseal junction of the femur +/- intra-articular extention to the femoral condyles. Majority of distal femur fractures are treated operatively.
Fractures of the distal femur account for 7% of femur fractures. Like most fractures it has a bimodal distribution with high-energy mechanism is common in the young population while low-energy mechanism is more common in the elderly.
AO/OTA Classification of distal femur fracture
| Category | AO/OTA | AO/OTA |
|---|---|---|
| Bone | Femur | 3 |
| Location | Distal segment | 33 |
| Types | Extra-articular (A) | 33-A |
| Partial-articular (B) | 33-B (33 – B3 is a Hoffa fragment) | |
| Complete articular (C) | 33 – C |
- Anatomy
- Shaft of femur is aligned with anterior half of the lateral condyle
- There is a anatomic axis 9 degrees of valgus (7 – 11 degrees)
- On axial section teh distal femur is trapezoidal in shape which has implications for implant placement and the prominence of screws
- Mechanism of injury
- High-energy (significantly displaced)
- Motorvehicle accident
- Fall from height
- Low-energy (less displacement)
- Fall from standing height on flexed knee (in weakened bone)
- High-energy (significantly displaced)
- Deforming forces
- Shortening is caused by the quadriceps and hamstrings
- Apex posterior angulation and posterior displacement is caused by gastrocnemius (can obstruct the popliteal vessels)
- Varus angulation caused by hip adductors
- Associated injuries
- Open fracture (5 – 10%)
- Knee ligament injury (20%)
- Tibial plateau fracture
- Patella fracture
- Acetabular fracture
- Femoral neck fracture
- Femoral shaft fracture
- Signs and symptoms
- Inability to bear weight
- Pain of the distal femur
- Worse with knee movement
- Deformity of the distal thigh and knee
- Physical examination
- Tenderness
- Swelling
- Ecchymosis
- Neurovascular examination (potential injury to the popliteal artery)
- Investigations
- X-ray: AP and lateral views + joint above and below
- Double density on AP (Hoffa fragment)
- Paradoxical notch view on AP (articular fragment in recurvatum)
- CT-scan: to demonstrate intra-articular involvement, coronally oriented hoffa fragment and pre-operative planning
- Hoffa fracture in the coronal plane
- Separate osteochondral fragments int he area of the intervondylar notch
- Ankle-brachial index (ABI): to rule out vascular injury
- CT angiogram: Indicated if ABI is < 0.9
- X-ray: AP and lateral views + joint above and below
- Hoffa fragment
- A Hoffa fragment is an intra-articular distal femoral fracture in the coronal plane
- It occurs in 38% of distal femur fractures and is easy to miss on plain radiograph (missed 31% of the time)
- Affects the lateral condyle more than the medial condyle (80%)
- Treatment of distal femur fracture
- Resuscitation
- Splinting with a bohler-brown splint or thomas splint with a flexion device to minimize compression of the popliteal vessels
- External fixation
- Open reduction internal fixation (ORIF)
- Closed reduction and intramedullary fixation (IMN)
- Non-operative treatment with a long-leg cast followed by hinged knee brace (rare)
- Distal femur Arthroplasty
- Early range of motion exercises to prevent stiffness
- Non-weight bearing until evidence of fracture union
- Open reduction and internal fixation
- Anterior to posterior screw for Hoffa fragment
- Dynamic condylar screw (DCS) plate
- Lateral locked distal femur plates (31% rate of non-union)
- Intramedullary nail
- Indications for external fixation
- Temporary measure
- Unstable polytrauma
- Extensive soft tissue damage
- Contamination requiring multiple debridement
- Definitive measure
- Severe open and/or comminuted fracture
- Unstable for surgery
- Temporary measure
- Indications for arthroplasty
- Pre-existing osteoarthritis with amenable fracture pattern
- Indications for non-operative management (rare)
- Medical contraindication to surgery
- Non-ambulatory
- Non-displaced fracture
- Impacted, stable fracture
- Non-reconstructable fracture
- Severe osteopaenia
- Lack of experienced operative treatment, instruments or facilities
- Early complications of the distal femur fracture
- Injury to popliteal vessels and sciatic nerve
- Fat embolism
- Deep venous thrombosis and pulmonary embolism
- Late complications of distal femur fracture
- Knee pain and/or stiffness
- Post-traumatic osteoarthritis
- Malunion
- Non-union
- Implant failure
