Terminology

• Distal femoral fractures include injuries within the Heim square, a square constructed using the maximal condylar width.
• This text will focus on open distal femur fractures in adults. For pediatric distal femur fracture considerations, further reading is advised at the AO surgery reference website.

^{Distal femoral zone as defined by the Heim square.}

Trauma mechanism

Open distal femur fractures are often the result of high-energy trauma and affect young, otherwise healthy patients. Typical mechanisms include motorcycle or car accidents (dashboard injuries) or falls from height.

The classic mechanism is a direct blow to a flexed knee. Axial load transmitted through the tibia drives the femoral condyles apart, producing a supracondylar intra- or extra-articular fracture pattern.

Several strong muscle groups contribute to the typical shortened, varus-aligned, and posteriorly angulated displacement seen on presentation:

• Shortening – the quadriceps and hamstrings pull in opposite directions.
• Varus angulation – the adductor magnus draws the distal fragment medially.
• Apex-posterior deformity – the gastrocnemius pulls the distal fragment posteriorly.

^{Shortening of femur caused by pulling of quadriceps and hamstrings muscles, and posterior dislocation of the the distal fragment caused by pulling of the gastrocnemius muscle}

Immediately posterior to the distal femur lies the popliteal neurovascular bundle. Due to this close relationship, markedly displaced or open injuries may compress, stretch, or lacerate the popliteal artery, potentially threatening the limb.

Management in the ER

General initial management principles apply.

Initial evaluation and management in open fractures in the ER

Specific points for open proximal tibia fractures are:

• Bloodloss - In open distal femoral fractures, blood loss can exceed 1000 mL, with a real risk of hemodynamic instability or shock.
• Realignment and temporary stabilization - Options include a Thomas's splint, a long-leg backslab, or an improvised splint using available firm materials, secured with bandages or strips of cloth while maintaining gentle traction. Whichever method is used, pad generously around the fibular neck to protect the common peroneal nerve.

^{Thomas’s splint.}

• Vascular status - Palpate the dorsalis pedis and posterior tibial pulses before and after realignment, and proceed to urgent surgical exploration if pulses remain absent.
• Skin status - Perform a thorough evaluation of the skin to assess the possibility of an open fracture.

Temporary stabilisation in the ER can also be achieved with an upper leg cast or skeletal traction using a proximal tibial pin.

Once the patient is hemodynamically stable, start imaging the entire limb, including the joints proximal and distal to the suspected injury. The distal femur is best visualised with anteroposterior and lateral views.

Fracture management plan

How to make an integrated open fracture treatment plan

Once the patient has been stabilised, a definitive fracture management plan should be made. The choice between non-operative treatment, immediate definitive fixation, or a staged approach should be carefully considered.

Nonoperative management

Non-operative management can be considered for stable, minimally displaced, non-articular distal femoral fractures. Always perform surgical debridement in case of open fractures. In low-resource settings, if non-operative management is used for displaced or unstable fractures, a limited functional outcome should be expected.

Operative management

In most cases, especially in high-resource settings, internal fixation is feasible at the first surgery as soon as the patient is stabilised. Alternatively, a two-stage approach can be chosen when soft tissues do not allow direct definitive internal fixation, or when the patient is hemodynamically unstable in a damage control setting. Apply a fracture-spanning external fixator for temporary stabilisation. If a plastic surgeon is available, early consultation and collaborative surgery is recommended.

Open reduction and internal fixation is, in acute open distal femur fractures, the gold standard using locked plate fixation and screws. Fractures without articular involvement can be managed with intramedullary nailing, as described in Open Femur Shaft fracture. Further reading on ORIF is advised at the AO surgery reference website. Open reduction and internal fixation should only be performed once the fracture has been:

• debrided and cleansed,
• when soft tissue coverage in the same early setting is achieved,
• when the environment is sufficiently sterile,
• and when resources and knowledge are available.

When these conditions cannot be met and referral isn't possible, external fixation can serve as definitive treatment.

Definitive fixation with an External fixator

Where resources allow, a proximal tibial pin is the preferred site for tibial skeletal traction (e.g. Perkin's traction). Keep the leg in slight flexion to relax the gastrocnemius and reduce posterior displacement, and continue traction for 6–12 weeks with gradual weight-bearing once union is visible on radiographs. If surgical resources become available, patients treated initially non-operatively should be reassessed for possible conversion to definitive fixation.

_{Early active knee mobilization after the acute phase in Perkin's traction.}

Not all distal femoral fractures are suitable for Perkin's traction

^{Fracture patterns suitable and unsuitable for Perkin's traction}

If surgical resources become available, patients treated initially non-operatively should be reassessed for possible conversion to definitive fixation.

Non-Operative Management of open fractures

Amputation

Above-knee amputation should be discussed with the patient for severe intra-articular fractures with vascular injury, or extensive soft-tissue necrosis. Limb salvage in these cases often means a long, complication-prone rehabilitation; amputation with good prosthetic fitting can offer a shorter, more predictable recovery and, for some patients, a better quality of life.

External fixator for a distal femoral fracture

General principles of external fixation apply:

Applying a temporary external fixator

When applying an external fixator for a distal femoral fracture, follow some specific considerations:

• Safe zones - Keep femoral and tibial pins within recognised safe zones, avoiding the common peroneal nerve, deep peroneal nerve, and popliteal artery, and out of the joint. This means maintaining a (antero)lateral approach femorally, and staying in the midsagittal plane tibially.

• Construct choice - In extra-articular fractures with a large enough distal femoral fragment for two firm pins, a non-bridging fixator can be used instead, as described for Open Femur Shaft fracture. In all other distal femur fractures, the frame must bridge the knee.
• Knee-bridging - Place femoral pins (antero)laterally into the midshaft, one proximal and one distal in the same coronal plane. Place tibial pins just below the anterior tibial tubercle in the midsagittal plane, ≥15 mm distal to the joint line, one proximal and one distal in the same plane.

Adding stability
For the distal femur, the standard bar-to-bar construct is not always stable enough. Depending on the fracture pattern, consider to:

1 Add a neutralisation bar from the distal femoral pin to the proximal tibial pin;

2 Maximise pin spread within each bone segment;

3 Use the thickest pins (6 mm) and bars the system allows;

4 If needed, add a medial accessory frame to resist varus forces, through an open approach with great attention to the femoral artery and other nearby neurovascular structures.

Technical considerations

• Reduction - Closed reduction via ligamentotaxis is usually adequate; control with fluoroscopy if available.
• Knee position - If open reduction is performed, keep the knee neutral or slightly flexed (~10°), never hyperextended.
• Drill guide - The thick soft-tissue envelope around the femur makes a tissue protector essential when drilling.
• Interconnecting bar - Keep it clear of the skin over the knee.
• Duration - A knee-bridging frame immobilises the joint; minimise the time it stays in place to limit stiffness.

Soft tissue management

The reconstructive ladder is helpful in deciding your strategy. Start with the simplest effective option, but do not oversimplify.

Soft tissue management in open fractures

For small to medium-sized defects with exposed bone, local transposition or rotation flaps may provide reliable coverage. For larger defects of the distal femur some locoregional options include:

• Vastus medialis perforator flap (knee)
• Medial and lateral gastrocnemius flap

Aftercare

1  Pin-site care – pins loosen more easily in the softer metaphyseal bone, and an infected pin near the knee risks septic arthritis; careful pin-site care and monitoring are essential.

2  Mobilisation – knee mobility is inevitably limited while the frame is in place; encourage movement of all other joints, ideally with a physiotherapist, and begin knee range-of-motion exercises after frame removal. Counsel patients that some residual knee stiffness should be expected after an intra-articular distal femur fracture treated with external fixation.

3  Follow-up – close clinical follow-up is essential; functional recovery can continue for up to a year, particularly in complex cases, with physiotherapy central to regaining knee range of motion.

Complications of fracture management in open fractures