DISTAL FEMUR Fractures

EPIDEMIOLOGY

Distal femoral fractures account for about 7% of all femur fractures.

If hip fractures are excluded, one-third of femur fractures involve the distal portion.

A bimodal age distribution exists, with a high incidence in young males from high-energy trauma, such as motor vehicle or motorcycle accidents or falls from a height, and a second peak in elderly women from minor falls.

There is a 1:2 ratio of men to women.

Open fractures occur in 5% to 10% of all distal femur fractures.

ANATOMY

The distal femur includes both the supracondylar and condylar regions (Fig. 33.1).

The supracondylar area of the femur is the zone between the femoral condyles and the junction of the metaphysis with the femoral shaft. This area comprises the distal 10 to 15 cm of the femur.

The distal femur broadens from the cylindrical shaft to form two curved condyles separated by an

intercondylar groove.

The medial condyle extends more distally and is more convex than the lateral femoral condyle. This accounts for the physiologic valgus of the femur.

When viewing the lateral femur, the femoral shaft is aligned with the anterior half of the lateral condyle (Fig. 33.2).

When viewing the distal surface of the femur end on, the condyles are wider posteriorly, thus forming a trapezoid.

Normally, the knee joint is parallel to the ground. On average, the anatomic axis (the angle between the shaft of the femur and the knee joint) has a valgus angulation of 9 degrees (range, 7 to 11 degrees) (Fig. 33.3).

Deforming forces from muscular attachments cause characteristic displacement patterns (Fig. 33.4).

• Gastrocnemius: This flexes the distal fragment, causing posterior displacement and angulation.

• Quadriceps and hamstrings: They exert proximal traction, resulting in shortening of the lower extremity.

   

   

   

  MECHANISM OF INJURY

Most distal femur fractures are the result of a severe axial load with a varus, valgus, or rotational

force.

In young adults, this force is typically the result of high-energy trauma such as motor vehicle collision or fall from a height.

In the elderly, the force may result from a minor slip or fall onto a flexed knee.

CLINICAL EVALUATION

Patients typically are unable to ambulate with pain, swelling, and variable deformity in the lower thigh and knee.

Assessment of neurovascular status is mandatory. The proximity of the neurovascular structures to the fracture area is an important consideration. Unusual and tense swelling in the popliteal area and the usual signs of pallor and lack of pulse suggest rupture of a major vessel.

Compartment syndrome of the thigh is uncommon and is associated with major bleeding into the thigh.

Examination of the ipsilateral hip, knee, leg, and ankle is essential, especially in the obtunded or polytraumatized patient.

When a distal femoral fracture is associated with an overlying laceration or puncture wound, computed tomography (CT) scanning is the most accurate assessment of joint contamination. If the wound communicates with the joint, CT scanning of the knee will demonstrate free air.

RADIOGRAPHIC EVALUATION

Anteroposterior, lateral, and two 45-degree oblique radiographs of the distal femur may be obtained.

Radiographic evaluation should include the entire femur.

Traction views may be helpful to better determine the fracture pattern and intra-articular extension.

Contralateral views may be helpful for comparison and serve as a template for preoperative planning.

Complex intra-articular fractures and osteochondral lesions may require additional imaging with CT to assist in completing the diagnostic assessment and preoperative planning.

Magnetic resonance imaging may be of value in evaluating associated injuries to ligamentous or meniscal structures but not in the initial assessment.

Arteriography may be indicated with dislocation of the knee, as 40% of dislocations are associated with vascular disruption. This is due to the fact that the popliteal vascular bundle is tethered proximally at the adductor hiatus and distally at the soleus arch. By contrast, the incidence of vascular disruption with isolated supracondylar fractures is between 2% and 3%.

CLASSIFICATION

Descriptive

Open versus closed

Location: supracondylar, intercondylar, condylar

Pattern: spiral, oblique, or transverse

Articular involvement

Comminuted, segmental, or butterfly fragment

Angulation or rotational deformity

Displacement: shortening or translation

Neer Classification

Based on direction of displacement of distal fragments

Does not take into account intra-articular displacement

Orthopaedic Trauma Association Classification of Distal Femoral Fractures See Fracture and Dislocation Classification Compendium at http://www.ota.org/compendium/compendium.html.

TREATMENT

Nonoperative

Indications include nondisplaced or incomplete fractures, impacted stable fractures in elderly patients, severe osteopenia, advanced underlying medical conditions, or select gunshot injuries.

In stable, nondisplaced fractures, treatment is mobilization of the extremity in a hinged knee brace, with partial weight bearing.

In displaced fractures, nonoperative treatment entails a 6- to 12-week period of casting with acceptance of resultant deformity followed by bracing. The objective is not absolute anatomic reduction but restoration of the knee joint axis to a normal relationship with the hip and ankle. Potential drawbacks include varus and internal rotation deformity, knee stiffness, and the necessity for prolonged hospitalization and bed rest.

Operative

Most displaced distal femur fractures are best treated with operative stabilization.

Most of these fractures can be temporized in a bulky cotton dressing and a knee immobilizer; in significantly shortened fractures, tibial pin traction may be considered.

Articular fractures require anatomic reconstruction of the joint surface and fixation with interfragmentary lag screws.

The articular segment is then fixed to the proximal segment, in an effort to restore the normal anatomic relationships. These should encompass all angular, translational, and rotational relationships.

In elderly patients with severe osteopenia or those with contralateral amputation, length may be sacrificed for fracture stability and bony contact.

With the advent of more biologic techniques of fracture stabilization, the necessity for bone grafting has diminished.

Polymethylmethacrylate cement or calcium phosphate cement may be utilized in extremely osteoporotic bone to increase the fixation capability of screws and/or fill bony voids.

Implants

Screws alone: In most cases, screws are used in addition to other fixation devices. In noncomminuted, unicondylar fractures in young adults with good bone stock, interfragmentary screws alone can provide adequate fixation in partial articular patterns.

Plates: To control alignment (particularly varus and valgus) of the relatively short distal articular segment, a fixed angle implant is most stable.

• A 95-degree condylar blade plate: This provides excellent fracture control but is technically demanding.

• Dynamic condylar screw (DCS): This is technically easier to insert than a condylar blade

  plate, and interfragmentary compression is also possible through its lag screw design. Disadvantages of the DCS are the bulkiness of the device and the poorer rotational control than with the blade plate.

• Locking plates (with fixed angle screws): The development of locking plates made the nonlocking periarticular plate relatively obsolete. Locking plates are an alternative to the DCS and blade plate. Like the DCS and the blade plate, locking plates are fixed angle devices. The screws lock to the plate and therefore provide angular stability to the construct.

• Nonlocking periarticular plates (condylar buttress plates): These are virtually obsolete.

Intramedullary (IM) nails

• Antegrade inserted IM nail: It has limited use owing to the distal nature of the fracture. It is best used in supracondylar type fractures with a large distal segment.

• Retrograde inserted IM nail: It has the advantage of improved distal fixation. The

  disadvantages are the further insult to the knee joint and the potential of knee sepsis if the nailing is complicated by infection. Retrograde nails should bypass the isthmus proximally.

External fixation

• In patients whose medical condition requires rapid fracture stabilization or in patients with major soft tissue lesions, spanning external fixation allows for rapid fracture stabilization while still allowing access to the limb and patient mobilization.

• Definitive external fixation, although rarely used, can be in the form of a unilateral half-pin fixator or a hybrid frame.

• Problems include pin tract infection, quadriceps scarring, delayed or nonunion, and loss of

  reduction after device removal.

  Associated Vascular Injury

The incidence is estimated to be about 2% in distal femoral fractures.

If arterial reconstruction is necessary, it should be done following temporary stabilization and before definitive skeletal stabilization.

Definitive fracture management can proceed after the vascular procedure if the patient’s condition allows.

Fasciotomy of the lower leg should be performed in all cases.

Supracondylar Fractures Above a Total Knee Replacement

These are classified according to fracture extent and implant stability.

These are increasing in incidence and are related to osteopenia, rheumatoid arthritis, prolonged corticosteroid usage, anterior notching of the femur, and revision arthroplasty.

Treatment is based on the status of the arthroplasty implants (well fixed or loose) and the patient’s preinjury function.

Surgical options include:

• Retrograde IM nailing: Open box designs, dependent on the amount of bone distally

• Plate fixation: Allows for treatment of most fractures, especially if no access through femoral component

• Revision arthroplasty: For implants that are aseptically loosened with associated fractures

  Postoperative Management

The injured extremity may be placed on a continuous passive motion device in the immediate postoperative period if the skin and soft tissues will tolerate. No study has demonstrated efficacy.

Physical therapy consists of active range-of-motion exercises and non–weight bearing or touchdown weight bearing with crutches 2 to 3 days after stable fixation may be allowed.

A brace may be used to diminish varus and valgus forces.

Weight bearing may be advanced with radiographic evidence of healing (6 to 12 weeks).

Healing in the elderly may be delayed beyond 12 weeks.

COMPLICATIONS

Fixation failure: This is usually a result of one of the following: nonunion, poor bone stock, patient noncompliance with postoperative care, or inadequate surgical planning and execution.

Malunion: This usually results from malalignment at the time of surgery. Varus is the most common deformity. Malunion with the articular surface in extension may result in relative hyperextension of the knee, whereas malunion in flexion may result in a functional loss of full extension. Malunion resulting in functional disability may be addressed with osteotomy.

Nonunion: This is infrequent because of the rich vascular supply to this region and the predominance of cancellous bone. There is a greater incidence in the elderly.

Posttraumatic osteoarthritis: This may result as a failure to restore articular congruity, especially in younger patients. It also may reflect chondral injury at the time of trauma.

Infection: Open fractures require meticulous debridement and copious irrigation (serial, if necessary) with intravenous antibiotics. Open injuries contiguous with the knee necessitate formal irrigation and debridement to prevent knee sepsis.

Loss of knee motion: This is the most common complication as a result of scarring, quadriceps damage, or articular disruption during injury. If significant, it may require lysis of adhesions or quadricepsplasty for restoration of joint motion. It is best prevented by anatomic reduction, early range of motion, and adequate pain control.