Patella Fractures — Tension Band Wiring

Patella fractures account for approximately 1% of all skeletal fractures and commonly occur following direct trauma to the anterior aspect of the knee or sudden contraction of the quadriceps muscle. The patella plays a crucial role in the knee extensor mechanism and increases the mechanical efficiency of the quadriceps muscle by acting as a lever arm.

Because the patella is embedded within the quadriceps tendon proximally and the patellar tendon distally, fractures of the patella can disrupt the extensor mechanism of the knee. Restoration of this mechanism is the primary goal of treatment.

Tension band wiring (TBW) is the most commonly used surgical technique for displaced transverse fractures of the patella. The tension band principle converts tensile forces generated by the quadriceps muscle into compressive forces at the fracture site during knee flexion.

The patella is the largest sesamoid bone in the body and is located within the quadriceps tendon. It articulates with the femoral trochlea and forms part of the knee joint.

• Triangular bone with base superior and apex inferior
• Posterior surface covered with thick articular cartilage
• Embedded within quadriceps tendon
• Patellar tendon attaches distally to tibial tuberosity

The patella improves the mechanical advantage of the quadriceps muscle and increases knee extension strength.

The patella receives blood supply from the genicular arterial network surrounding the knee joint.

• Superior genicular arteries
• Inferior genicular arteries
• Anterior tibial recurrent artery

Disruption of this blood supply may contribute to delayed union or nonunion following fractures.

Patella fractures typically occur through two mechanisms.

• Direct trauma such as fall onto the knee
• Indirect injury due to sudden quadriceps contraction
• Motor vehicle accidents
• Sports injuries

Direct trauma often produces comminuted fractures, whereas indirect injuries frequently produce transverse fractures.

Patella fractures may be classified based on fracture pattern.

• Anterior knee pain
• Swelling and bruising
• Difficulty extending the knee
• Palpable defect in patella
• Inability to perform straight leg raise

Loss of active knee extension indicates disruption of the extensor mechanism.

• AP knee radiograph
• Lateral knee radiograph
• Skyline (sunrise) view
• CT scan for complex fractures

Radiographs help determine fracture displacement and articular involvement.

The tension band principle converts tensile forces acting on the anterior surface of the patella into compressive forces at the fracture site during knee flexion.

• Two parallel K-wires placed across fracture
• Figure-of-eight stainless steel wire loop
• Compression generated during knee motion

• Midline anterior knee incision
• Fracture reduction
• Insertion of two parallel K-wires
• Application of figure-of-eight tension band wire
• Verification of fixation stability

Early mobilization is encouraged following stable fixation.

• Hardware irritation
• Nonunion
• Knee stiffness
• Post-traumatic arthritis
• Loss of knee extension strength

• Patella fractures account for about 1% of all fractures
• Tension band converts tensile forces into compression
• Loss of straight leg raise indicates extensor mechanism disruption
• TBW is standard treatment for transverse fractures