Working Diagnosis:
PCL Avulsion Fracture, medial femoral condyle osteochondral fracture, loose body, and anterior horn medial meniscus tear

Treatment:
Diagnostic arthroscopy, PCL Repair, Medial Meniscus Repair

Outcome:
Successful PCL repair and medial meniscus repair

Intraoperative Photos: Posterior sag and posterior drawer Case Photo #5 Case Photo #6

Return to Activity:
0-3 weeks: Cast and non-weight-bearing in wheelchair.
3-6 weeks: Hinged knee brace with 0-90 degrees allowed, toe-touch weight-bearing, PT with PCL and meniscus repair protocol.
6-12 weeks: Full weight-bearing, continue PT, avoid running and jumping.
12-16 weeks: Brace removed.
16 weeks: Returned to full activities without restriction.

Author's Comments:
Posterior cruciate ligament (PCL) avulsion fracture is a rare variant of PCL tears. There is a wide range of reported incidence of general PCL injuries, between 3-38% of acute knee injuries, which may be due to variable clinical presentations and asymptomatic cases. In pediatric patients, the diagnosis can often be delayed or missed because examination of the knee can be non-specific and there may be a low suspicion of injury due its rarity. Most injuries are seen in motorcycle or car accidents when posterior forces are placed on the tibia with the knee flexed. They are also seen in athletes who jump and land on a plantarflexed foot with the knee in flexion. Since most PCL injuries occur in young, active patients, it is generally recommended that a displaced avulsion fracture should be reduced and fixed in a timely fashion to stabilize the joint and prevent nonunion.

Editor's Comments:
The PCL or posterior cruciate ligament and prevents posterior displacement of the tibia in relation to the femur. It is less commonly injured than the ACL and often occurs with other ligament injuries, although isolated PCL injuries occur.

PCL injuries are uncommon in children. When an injury to the PCL occurs in children, they are more likely to have an avulsion fracture of either the tibial or femoral attachment sites rather than an injury to the ligament itself. This is a typical injury pattern throughout the body in prepubescent children. It is proposed that the open physis predisposes the osteochondral structures to injury rather than the ligament itself. A high degree of suspicion is imperative as missed injuries could increase the risk of nonunion, malunion, PCL insufficiency, and knee instability.

Commonly cited mechanisms for PCL complex injuries include a direct blow to anterior tibia,
hyperflexion, and rarely hyperextension. Isolated injuries to the PCL are often mild with minimal limitation; however, instability can be problematic both acutely and chronically. In contrast, avulsion fractures of the attachments of the PCL present with more acute disability. These patients commonly have an effusion, limited range of motion, and pain. Physical exam may be limited by guarding; however, special tests that will test the PCL integrity include posterior drawer, posterior sag, posterior Lachman, quadriceps active test, and the dial test. It is critical to evaluate for additional injuries.

Imaging: Avulsion fractures may be visualized on plain films; however, these injuries can be occult, especially in the setting of skeletal immaturity. MRI can help detect occult fractures and assess for additional injuries. In skeletally immature patients, x-rays of the contralateral knee can be helpful to look for asymmetry in the physis.

As this is a rare injury, management guidelines are lacking. Both successful non-operative and operative management have been described. At this time, most seem to favor operative management for young and active individuals. However, a recent literature review by Hurni discussed a successful case of non-operative management. The article further discusses that patient selection is essential when opting for non-operative management. Non-operative management should only be utilized for nondisplaced or minimally displaced isolated fractures. The degree of activity and sport participation is also an important consideration. These recommendations are inspired by and similar to the more robust literature for ACL avulsion fractures. In cases of failure of non-operative management, surgical fixation is recommended.

An area of necessary further research includes optimal surgical fixation and investigation of what degree of displacement is amenable to non-operative management in a pediatric population.

References:
Hurni Y, et al. Pediatric Posterior Cruciate Ligament Avulsion Fracture of the Tibial Insertion: Case Report and Review of the Literature. Surg J (N Y). 2017;3(3):e134-e138.

Wegmann H, et al. Surgical Treatment of Posterior Cruciate Ligament Lesions Does Not Cause Growth Disturbances in Pediatric Patients. Knee Surg Sports Traumatol Arthrosc. 2019;27:2704-2709.

Katsman A et al. Posterior Cruciate Ligament Avulsion Fractures. Curr Rev Musculoskelet Med. 2018;11:503-509.

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