Successful repair of an isolated osteochondral fracture of the patella presenting with locking of the knee

Abstract

A 15-year-old boy presented with a locked knee after a football injury. Sudden valgus impact to the planted right leg caused a patellar osteochondral fracture diagnosed by magnetic resonance imaging. The 2.5-cm fragment had avulsed off the medial facet without damage to the medial retinaculum or the medial patellofemoral ligament. The fracture was stabilised with headless compression screws. It had healed at 8 weeks, with the patient being able to bear full weight, and with a full range of active knee movement. At 4 months, he had returned to playing football for his school team. Normally, such a fracture occurs due to sheering force on the patella against the femur during the relocation phase of an acute patellar dislocation. In this case, the patella may have subluxed and then reduced spontaneously, without causing a true dislocation or damage to the medial soft tissue restraints. The energy dissipated at contact with the femur would however be sufficient to sheer the fragment off the patella. We believe this is the first report of successful repair of an osteochondral patellar fracture sustained by this mechanism.

A successful technique to repair an osteochondral patellar fracture composed of largely primary articular cartilage

“…2,3 Shearing forces across the knee cause patellar dislocation, forcing the medial facet to crash into the lateral femoral condyle with damage to the patella as well as the lateral condyle of the femur. 4 Additionally, this shearing process usually disrupts the medial patellofemoral ligament as well as the medial retinaculum and forms a haemarthosis of the joint. 4,5 In this case, it would appear that the patella was dislocated and during relocation, caused impaction on the lateral femoral condyle which fractured the patella and produced an OC fragment made up of primarily articular cartilage.…”

“…1,2 In this case, fixation was successful where others may have not been successful, partly due to the early surgical intervention, the technique used in surgery, as well as the fact that the fragment was large enough to reattach to the patella. Khan et al 4 reported a successful surgical intervention using a different technique, whereby K wires temporarily held the fragment in place which was then fixed rigidly with three headless compression scews buried deep to the cartilage. In our case, there was a very thin sliver of osteochondral bone attached to a large piece of articular cartilage.…”

“…4 Additionally, this shearing process usually disrupts the medial patellofemoral ligament as well as the medial retinaculum and forms a haemarthosis of the joint. 4,5 In this case, it would appear that the patella was dislocated and during relocation, caused impaction on the lateral femoral condyle which fractured the patella and produced an OC fragment made up of primarily articular cartilage.…”

“…Khan et al. 4 reported a successful surgical intervention using a different technique, whereby K wires temporarily held the fragment in place which was then fixed rigidly with three headless compression scews buried deep to the cartilage. In our case, there was a very thin sliver of osteochondral bone attached to a large piece of articular cartilage.…”