Patellar Fractures

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Definition/Description

There are three types of patellar fractures. The first type is caused by direct violence and is called comminuted. These type of fractures are usually associated with a blow or a fall on a flexed knee. The second type is caused by muscle violence and is called transverse. These type of fractures are usually associated with rupture of the lateral expansions at the level of fracture. And the third type are minor marginal fractures. Approximately 1% of all skeletal injuries are patellar fractures. Maybe there is even a forth type of patellar fracture, the overuse injury or the stress fracture, mostly seen with long distance runners, military recruits and patients with cerebralpalsy.

Figure 1: example of a comminuted fracture

Figure 2: example of a transverse fracture 

Clinically Relevant Anatomy

The patella is the largest sesamoid bone in the body. It's a part of the articulatio patello-femoral. The patella has a triangular shape and on the anterior side of the patella we have: facies anterior, basis patellae and apex patellae. On the posterior side of the patella we have: facies articularis patellae, one lateral and one medial separated by a ridge. On the basis patellae is the insertion of the quadriceps tendon. On the apex patellae is the origin of the patellar ligament. The patella has the thickest articular cartilage of the body, the cartilage may be as thick as 1 cm. The patella is surrounded by several structures going from muscles to menisci. The two muscles that control the movement of the patella are the vastus medialis and the vastus lateralis. Then there are the ligaments, the cruciate ligaments and the two menisci. 

Characteristics/Clinical Presentation

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Differential Diagnosis

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Diagnostic Procedures

Sometimes the edges of the fracture can be felt through the skin. Normally one would also look for hemarthrosis, this is the swelling deep inside the joint. But there isn't some kind of specific test to identify a patellar fracture. We always need an X-ray to confirm the diagnosis. The X-ray can show front and side views of the fracture. 

Outcome Measures

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Examination

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Medical Management

Surgical treatment is usually used with a displaced fracture. Sometimes surgery is necessary because the thigh muscles are very strong and can pull the broken pieces out of place and apart from each other so callus cannot form and the healing with ossification is impossible. The type of procedure isn't always the same. It depends on the type of fracture you have. If you have a transverse fracture the most common procedure is to use pins and wires and 'a figue of eight' to press the pieces together. When you have a comminuted fracture, which is a type of fracture that is usually associated with a blow or a fall on a flexed knee, the small crushed pieces of the patella will be removed. When the kneecap is broken in its centre the doctor can use wires and screws to fix it. A patellectomy is the last treatment for a comminuted fracture. Nonsurgical treatment is indicated when the broken pieces of the patella aren't displaced. The patient need casts or splints to immobilize the fractured pieces so callus formation can take place. And you will also need crutches during the 6 to 8 weeks that the bone needs to heal completely. 

Physical Therapy Management

Treatment with heat and cold can be used to control pain and oedema. During the immobilization of the knee the patient is encouraged to train other leg muscles. After removing the cast or splint, and the fracture is considered healed, the therapy to regain range of motion starts.

There are instructions to prevent loss of motion and strength in adjacent joints. Ankle exercises are taught to promote circulation. 

The patients body decides the range of motion, strengthening, and proprioceptive exercises of the involved joint. 

Key Research

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Resources

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Clinical Bottom Line

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References

[Category:Bones]]