Patella Sleeve Fracture in Children

Introduction

The patella is a sesamoid bone that is considered a part of the quadriceps extensor mechanism. Ossification of the immature patella begins during 3 to 6 years of age. Patella sleeve fracture is uncommon in skeletally immature children. Radiographs may not show the fracture because only a tiny bone is visible. This article provides a brief review of patella sleeve fractures in children.

What Is a Patella Sleeve Fracture?

Small bone pieces from the distal pole of the patella that are separated from the patella's main body with articular cartilage, retinaculum, and periosteum are known as patella sleeve fractures. It is a rare injury seen in children between 8 and 12 years of age when patellar ossification nears completion. It accounts for less than 1 % of all pediatric fractures.

Adolescents are more susceptible to patella sleeve fracture because of rapid growth, increased sports activity, and patella instability. In this fracture, the cartilage sleeve gets separated from the ossified patella. The condition is also called a break in the child’s kneecap. The fractured bone parts may move out of line or break through the skin. Patella sleeve fracture is more predominant in males than females.

Patella sleeve fractures are classified based on the location as any segment of the patella periphery can be involved and are:

1. Superior Pole Fracture: It is the less common fracture.

2. Inferior Pole Fracture: It is the most common fracture.

What Causes Patella Sleeve Fracture?

The fracture develops from indirect injury caused by the powerful contraction of the quadriceps muscle applied to the flexed knee. It usually happens when the child is jumping, during a fall, or while participating in sports.

What Are the Signs and Symptoms of Patella Sleeve Fracture in Children?

The child experiences pain when the fractured knee is touched or when moving the leg. Additionally, swelling and bruising around the knee develops. Knee hemarthrosis is a common condition. The child will not be able to bear weight on the affected leg. Raising the affected knee when the child is lying down becomes difficult. Disruption of the extensor mechanism is indicated by a high-riding patella or a palpable gap at the distal end of the patella. Extending the knee against opposition becomes more challenging when the kneecaps are damaged.

Two vital signs of patella sleeve fracture are a palpable gap at the lower pole of the patella and patella alta (high-riding patella).

How Is a Patella Sleeve Fracture Diagnosed?

Healthcare providers will take history to understand the injury and examine the child. On examination, children with patella sleeve fractures present with a limp, tenderness to palpation during extensor mechanism, effusion, and extensor lag (inability to actively move a joint to its passive limit). They will look for bones that might have pierced the skin.

• Patella sleeve fracture is analyzed by taking lateral X-ray radiographs of the knee. It helps analyze the fracture type and compare the knee caps with another leg. The X-ray reveals swelling at the lower pole of the patella and some degree of patella alta. There are visible little avulsed bone fragments.

• A CT (computed tomography) or MRI (magnetic resonance imaging) scan shows fractures or other injuries. A contrast media can be administered to the child to visualize the kneecap better. It is a crucial imaging procedure for identifying chondral injury and extensor mechanism damage.

• A bone scan helps doctors to visualize knee fractures and visualize any infections. A radioactive liquid called a tracer is administered through a vein. Images are obtained once the tracer gathers inside the child's bone.

Large bone fragment avulsion fractures are visible in X-ray. However, the fracture may not be seen when only small fragments are avulsed.

What Is the Differential Diagnosis for Patella Sleeve Fracture in Children?

The differential diagnosis is:

• Sinding-Larsen-Johansson disease: It is a chronic disease.

• Jumper’s knee: It is a chronic condition seen in adults.

• Patella fracture.

• Quadriceps tendon fracture.

• Osgood-Schlatter Disease: A persistent disorder that impairs the patellar tendon's inferior attachment.

How Is Patella Sleeve Fracture Treated?

Treatment depends on how the kneecap breaks.

• Non-displaced fractures with intact extensor mechanisms are treated with cylindrical casting for six weeks. Additionally, a brace, cast, or splint can also be utilized. It prevents the kneecap from moving and helps it to heal. The child will need crutches to help them move around.

• Medications provide pain relief and prevent infections from developing. The child will also require a TT (tetanus vaccine) if the bone has pierced the skin to prevent tetanus.

• Displaced fractures with disrupted extensor mechanisms need operative treatment, such as open reduction and internal fixation. It is recommended for kneecap fractures more than 2 to 3 mm displaced. Surgery places the broken bones back in the correct position. Wires, pins, screws, or bands hold the bones in proper place. Surgery is conducted to remove part or completely damaged kneecaps.

• Following treatment, physical therapy is advised to assist the kid regain strength and mobility and relieve pain.

How to Care for Children With Patellar Fractures at Home?

• The child must rest their leg or knee as instructed by doctors. They can begin using crutches when doctors recommend them. When the child walks, the crutches give the injured limb rest and support.

• The application of ice can reduce pain and swelling in the affected area. Ice packs must be applied for 15 to 20 minutes every hour for two days.

• The child’s knee must be elevated above their heart level to decrease swelling and pain.

What Are the Complications Due to Patella Sleeve Fracture?

Complications are:

• Limitation in knee flexion.

• Transient ischemic changes.

• Extensive ectopic bone development within the knee.

• Avascular necrosis.

• Malunion.

• Nonunion.

What Is the Prognosis for Children With Patella Sleeve Fractures?

Correct diagnosis and proper intervention can produce excellent results where the knee returns to complete functional activity with no extensor lag and full flexion. Inadequate diagnosis can cause permanent disability where the child develops patella alta and subsequent knee instability, extensor lag, quadriceps wasting and weakness, and patella pain associated with osteochondral damage. Therefore, it causes ossification in the stretched patella tendon, resulting in patella magna or duplicate patella.

Conclusion

In early children, patella sleeve fractures are uncommon but are prevalent in adolescents. Acute knee injury must warrant suspicion of patella sleeve fracture, especially when no contact but massive force is involved, as the clinical signs and radiography might not always be diagnostic. Prompt diagnosis and treatment enable complete functional recovery.