27: Operative Treatment of Fractures of the Patella

PROCEDURE 27 Operative Treatment of Fractures of the Patella

Randy Mascarenhas, James Vernon, Chris Graham

image

image Operative treatment of displaced patella fractures is the standard of care due to the increased incidence of nonunion and loss of extensor mechanism strength associated with nonoperative treatment and prolonged knee immobilization (Chen et al., 1998).
image Current techniques include open reduction and internal fixation with screws or various forms of anterior tension band techniques and partial or total patellectomy.
image Several studies have found that biodegradable materials or strong sutures yield similar clinical and biomechanical results when compared to traditional wire tension band techniques (Bostman et al., 1983; Hung et al., 1985; Jakobsen et al., 1985).

Indications

image Open fractures of the patella
image A fracture gap greater than 3 mm
image An articular step greater than 2 mm
image Extensor mechanism disruption

Controversies

• The acceptable size of articular gaps and steps in the patella has been extrapolated from other joints in the body.

Examination/Imaging

PHYSICAL EXAMINATION

image Open knee wounds should be examined thoroughly to determine if they communicate with the fracture site or the knee joint.
image Testing for active knee extension contributes to the decision to proceed with surgery.
image Full active or passive range of motion of the affected knee should be avoided until imaging has been obtained due to the potential for further injury to the patellar retinaculum or further fracture displacement.
image Ligamentous examination of the knee is paramount to exclude concurrent injuries.
image The adjacent joints—the hip and ankle—should also be thoroughly examined.

Treatment Options

• Lag screw technique
• Anterior tension band
image Cannulated screws
image Kirschner wires
• Patellectomy
image Full
image Partial

IMAGING STUDIES

image Anteroposterior, lateral, and sunrise views of the affected patella should be obtained (Fig. 1A and 1B).
• A lateral radiograph helps gauge fracture displacement and congruity of the articular surface.
• Patella alta may be a sign of patellar tendon rupture, while patella baja may indicate injury to the quadriceps tendon.
image Magnetic resonance imaging may be used to identify marginal patella fractures or free osteochondral fragments. It may also help to identify concurrent ligamentous injuries.
image Computed tomography may be used for evaluation of associated distal femoral or proximal tibial fractures.
image A bone scan may help in the identification of stress fractures of the patella.
image

FIGURE 1

Surgical Anatomy

image The patella is a subcutaneous bone with minimal soft tissue covering. It is the largest sesamoid bone of the body and lies within the fascia lata and the fibers of the quadriceps tendon.
image The upper three fourths of the posterior surface of the patella is covered with articular cartilage that is divided into major medial and lateral facets.
image The patella is served by both extraosseous and intraosseous vascular systems.
• The primary blood supply to the patella is from branches of the geniculate anastomotic system around the knee (Fig. 2A).
♦ The superior portion of this vascular ring passes anterior to the quadriceps tendon, whereas the inferior portion passes posterior to the patellar ligament through the fat pad.
• The primary intraosseous blood supply of the patella enters the bone through the middle of the anterior portion of the body of the patella and through the distal pole (Fig. 2B).
♦ This relationship is important to understand and relate to the development of osteonecrosis secondary to a patella fracture.
image The patella is surrounded and anchored by a strong retinaculum derived from the deep fibers of the tensor fascia lata in combination with fibers from the vastus medialis, vastus lateralis, iliotibial tract, and patellofemoral ligaments (Fig. 3).
• The retinaculum inserts directly into the proximal tibia and serves as an auxiliary extensor of the knee along with the iliotibial band.
image The patellar tendon originates at the apex of the patella and inserts onto the tibial tubercle, blending with the patellar retinaculum and the iliotibial tract fibers (see Fig. 3).
image

FIGURE 2

image

FIGURE 3

PEARLS

• Flex the knee before inflation of the tourniquet.
• Place a bump under the ipsilateral hip.

PITFALLS

• Ensure the leg is draped free for easy flexion/extension.
• Intraoperative fluoroscopy access can be difficult if adequate planning is not done.

Positioning

image The procedure is performed with the patient in the supine position on a radiolucent table with a tourniquet on the proximal thigh (Fig. 4A and 4B).
image Prior to tourniquet inflation, gentle traction on the quadriceps/patellar fragment will keep the tendon nearer to anatomic length prior to reduction.
image A bump should be placed under the ipsilateral hip to help internally rotate the knee to a neutral position.
image The leg must be free draped to allow easy flexion/extension of the knee throughout the surgery (Fig. 4C).
image The leg is prepped from the lower leg to the upper part of the thigh.
image

FIGURE 4

PEARLS

• Consider subsequent procedures when planning the incision.
• Exposure of the retinacula is important to aid in repair.

PITFALLS

• The incision must not be carried deep into the patellar tendon or quadriceps tendon.
• Expose the retinacular tear in order to repair it.

Portals/Exposures

image A straight midline or medial parapatellar vertical incision is commonly used (Fig. 5A).
image It is important to consider any subsequent procedures when planning the incision.
• For example, exposure may be needed for a total knee arthroplasty.
image Medial and lateral full-thickness flaps are developed and exposure of both retinacula is obtained (Fig. 5B).
image Tagging sutures are placed in each retinaculum to aid with retraction (Fig. 5C).
• These sutures can subsequently be used for repair at the end of the case.
image

FIGURE 5

Instrumentation

• Self-retainers aid in exposure when placed both proximally and distally (Fig. 6).
• Rakes and skin hooks can be used for additional retraction.
image

FIGURE 6

Controversies

• The traditional surgical approach has been a transverse incision over the midportion of the patella to give access to the retinaculum without developing flaps.
image This does not take into consideration the incision needed for total knee arthroplasty in the future.

Procedure: Irrigation and Débridement of Open Fractures

image Open fractures should be treated as a surgical emergency.
image Due to the risk of bone and intra-articular infections, irrigation and débridement of the fracture should be performed within 6–8 hours.

STEP 1

image The surgical incision should ideally incorporate the open wound.
image All nonviable tissue and bone fragments should be resected with the exception of large osteochondral fragments, which may need to be retained.

PEARLS

• Open fractures are a surgical emergency.
• The wound may require repeat irrigation and débridement before definitive fixation.
• Nonviable tissue and bone fragments should be discarded.

STEP 2

image Gross contamination of the wound and patient medical status may delay rigid fixation.

Related posts:

16: Perilunate Injuries 29: Proximal Tibia Fractures: Intramedullary Nailing 11: Open Reduction and Internal Fixation of Olecranon Fractures 48: Treatment of Open Fractures 2: Glenoid Fracture 44: Anterior Approaches to the Acetabulum

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Jun 7, 2016 | Posted by in ORTHOPEDIC | Comments Off on 27: Operative Treatment of Fractures of the Patella

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