Paediatric Patella Injuries

Patella Fractures

Two major patterns:

Osteochondral low-energy injuries
Adult pattern high-energy injuries.

Osteochondral low energy injuries are more common and occur when the child athlete plants the ipsilateral foot and pivots to the contralateral side, thereby increasing valgus and lateral translational forces across the patellofemoral joint. As the patella dislocates, the medial facet strikes the edge of the lateral femoral condyle, causing an osteochondral fracture of the patella or condyle. Osteochondral fractures occur in association with approximately 5% of patellar dislocations in children.

Most often, the dislocation spontaneously reduces when the child falls to the ground. If not, it can easily be reduced by gently extending the knee and relaxing the quadriceps.

Treatment of osteochondral fractures

Treatment is based on the size and origin of the fragment. Most osteochondral fragments, either from the patella or from the femoral condyle, associated with patellar dislocation can be removed
arthroscopically.

Fragments >1cm in diameter from weight-bearing surfaces should be replaced and fixed in place.

True adult type patella fractures are rare in children and follow high energy trauma.

Treatment is similar to adult patella fractures.

Patella sleeve fracture

Acute patellar ligament avulsion fractures may occur either proximally or distally, correlating with their chronic counterparts, Sinding-Larson-Johannsen and Osgood Schlatter conditions. When avulsions occur proximally, a large piece of articular cartilage is pulled off the patella with a small fragment of bone, hence the term "sleeve fracture." These fractures occur in younger children who are playing and contract their quadriceps against a partially flexed knee when suddenly the knee buckles.

Radiographs are deceptive because the patellar fragment is very small. However, the lack of active extension combined with effusion, palpable deficiency in the patellar mechanism, and patella alta is diagnostic.

Treatment of Patella sleeve fracture

Surgical repair, usually the medial and lateral retinaculum are also found to be torn. Due to the small size of the fragment, rigid fixation is not possible, and therefore suture and possibly cerclage wiring supplemented by casting is required, with protection for 4 to 6 weeks.

References

JBJS- A 84:2288-2300 (2002) The Operative Management of Pediatric Fractures of the Lower Extremity; John M. Flynn, David Skaggs, Paul D. Sponseller, Theodore J. Ganley, Robert M. Kay and K. Kellie Leitch