Traumatic injury of the knee extensor mechanism in skeletally immature patients: Outcome and classification

Background: The literature is limited on the etiology and outcome of acute traumatic knee extensor mechanism injuries in skeletally immature patients with lack of a reliable classification system. Methods: Data on patients who sustained an acute traumatic injury of the knee extensor mechanism were reviewed with a minimum of 12-month follow-up. Functional outcome was evaluated regarding knee active range of motion. Functional outcome was described using the Knee Society Score (KSS). Data were expressed as mean +/- standard deviation. Results: Seventy-two patients with 74 knee extensor mechanism injuries were identified. The age at the time of injury was 13.9 +/- 1.9 years. They included 59 injuries with tibial tubercle avulsion fracture, six injuries with patellar tendon avulsion without bone injury, six injuries with combined patellar tendon avulsion with tibial tubercle fracture, two injuries with sleeve fracture, and one injury with quadriceps tendon avulsion. According to our classification, type IB1 injury was the commonest injury (79.7%). The time to return to sports was 5.23 +/- 2.98 months. The flexion was 128.7 degrees +/- 13.3 degrees. A mean terminal extension lag of 5.6 degrees was detected in three patients (4.1%). The KSS was 94.8 +/- 8.1 and the functional outcome was graded excellent in 64 patients (88.9%), good in seven patients (9.7%), and fair in one patient (1.4%). Conclusions: Traumatic injuries of the knee extensor mechanism in skeletally immature patients represent a wide variety of injuries including bony injuries in 82,4% of cases reviewed, tendinous injuries in 9.5%, and both bone and tendinous injuries in 8.1%. Our proposed classification system provides a more precise description of the injury pattern. (C) 2019 Elsevier B.V. All rights reserved.