Patellar Fracture Flashcards

Study Notes

Patellar Fracture Overview

A patella (kneecap) fracture is a traumatic injury resulting from direct impact or rapid contraction of the quadriceps with a flexed knee.

Mechanism of Injury (MOI)

Can occur from direct impact injury or indirect eccentric contraction; rapid knee flexion against contracted quadriceps is common.
In pediatric cases, patellar sleeve fractures may occur.

Associated Injuries

High-energy dashboard injuries may be linked with:
- Femoral neck fractures
- Posterior wall acetabular fractures
- Knee dislocations

Soft Tissue Attachments

Quadriceps tendon and fascia lata attach at the anterosuperior margin.
Quadriceps tendon consists of:
- Superficial layer: Rectus femoris (RF)
- Middle layer: Vastus medialis (VM) and vastus lateralis (VL)
- Deep layer: Vastus intermedius (VI)
Patellar tendon connects to the inferior margin.

Blood Supply

The patella receives its blood supply from an anastomotic ring formed by geniculate arteries.
Most crucial blood supply is located at the inferior pole of the patella.

Fracture Classification

Fractures classified as:
- Nondisplaced
- Displaced: defined by step-off >2-3mm or fracture gap >1-4mm
- Types: transverse, pole or sleeve (upper or lower), vertical, marginal, osteochondral, comminuted (stellate).

Physical Examination Findings

Palpable defects in the patella.
Significant hemarthrosis (blood in joint).
Inability to perform a straight leg raise indicates extensor mechanism failure.
Perform a saline load test to rule out open fractures.

Recommended Workup

X-rays in the anteroposterior (AP), lateral, and tangential views are important for assessment.

X-Ray Findings

Degree of fracture displacement correlates with retinacular disruption.
Patella alta indicates disruption of the patellar tendon (IS ratio >1).
Patella baja indicates a ratio of 2mm.
A displaced patellar fracture is characterized by displacement >3mm.
Patellar sleeve fractures are particularly noted in children.
Preservation of the patella is essential, avoiding patellectomy unless absolutely necessary.

Complications

Anterior knee pain is commonly reported after open reduction and internal fixation (ORIF).
Symptomatic hardware may occur in up to 50%, particularly in open fractures due to compromised soft-tissue.
Hardware migration associated with tension band wiring utilizing K-wires.
Weakness is more prevalent after partial or total patellectomy.
Loss of reduction occurs in 22%, especially in osteoporotic bone cases.
Nonunion of the fracture can also occur.

Description

Test your knowledge about patellar fractures with these flashcards. This quiz covers definitions, mechanisms of injury, and associated injuries related to patellar fractures, making it an excellent resource for medical students and orthopedic practitioners alike.