Patellar Fracture Flashcards

Questions and Answers

What is a patella (kneecap) fracture?

A traumatic injury caused by direct trauma or rapid contracture of the quadriceps with a flexed knee.

Describe the mechanism of injury (MOI) for patellar fractures.

Direct impact injury, or indirect eccentric contraction (rapid knee flexion against contracted quadriceps muscle, or patellar sleeve fracture in pediatrics).

What are associated injuries with a patellar fracture?

High-energy dashboard injuries are associated with femoral neck fracture, posterior wall acetabular fracture, or knee dislocation.

What are the soft tissue attachments of the patella?

Quadriceps tendon and fascia lata attach to the anterosuperior margin; the quadriceps tendon consists of a superficial layer from the rectus femoris (RF), middle from vastus medialis (VM) and vastus lateralis (VL), and a deep layer known as vastus intermedius (VI); the patellar tendon attaches to the inferior margin. Signup and view all the answers

What is the blood supply of the patella?

Derives from the anastomotic ring originating from geniculate arteries; the most important blood supply to the patella is located at the inferior pole. Signup and view all the answers

How do you classify patellar fractures?

Nondisplaced, displaced (step-off >2-3mm or fracture gap >1-4mm), transverse, pole or sleeve (upper or lower), vertical, marginal, osteochondral, and comminuted (stellate). Signup and view all the answers

What do you expect on physical examination (PE) for a patellar fracture?

Palpable patellar defect, significant hemarthrosis, inability to perform a straight leg raise indicating failure of the extensor mechanism, and perform a saline load test to rule out an open fracture. Signup and view all the answers

What is the recommended work-up for a patellar fracture?

X-rays (AP, lateral, tangential views). Signup and view all the answers

What are findings on X-rays for a patellar fracture?

Fracture displacement, degree of # displacement correlates with degree of retinacular disruption, patella alta (IS ratio >1 indicates disruption of patellar tendon), patella baja (IS ratio 2mm), displaced patella # >3mm, patella sleeve fractures in children. Signup and view all the answers

What are the complications of a patellar fracture?

Anterior knee pain, symptomatic hardware (up to 50%), hardware migration, weakness more common with partial or total patellectomy, loss of reduction (22%) increased in osteoporotic bone, nonunion. Signup and view all the answers

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.