AVULSIONS OF THE DISTAL FEMUR AND PROXIMAL TIBIA: RARE LIGAMENTOUS INJURIES IN CHILDREN AND ADOLESCENTS
Authors: Willimon S. Clifton , Perkins Crystal , Popkin Charles A. , Pennock Andrew , Polousky John D. , Algan Sheila 
Published: March 2019

Background: Avulsion fractures around the knee can occur as isolated injuries or in association with additional ligamentous knee injuries. Adolescents are particularly susceptible to avulsion injuries because of their relatively weak apophyses and numerous soft tissue attachments to the femur, tibia, and fibula. Avulsions around the knee can be easily overlooked or misdiagnosed. The consequences of delayed treatment can result in instability and long-term sequelae. Very little literature exists on the treatment and outcomes of proximal tibia and fibula and distal femur avulsions. The purpose of this study is to describe distal femoral and proximal tibia and fibula avulsions in adolescents, with a focus on injury patterns, treatment, and outcomes. Methods: The PRISM Multiligament Knee Research Interest group performed a multicenter retrospective review of consecutive pediatric patients treated for ligament and tendon avulsions from the distal femur [medial collateral ligament (MCL), fibular collateral ligament (FCL), and popliteus] and proximal tibia and fibula (MCL, FCL, biceps femoris, popliteus, and iliotibial band). Inclusion criteria were age less than 21 years and diagnostic imaging evidence of the avulsion. A chart review was performed to gather demographic, injury, treatment, and clinical follow-up data. Patients with less than 3 months of follow-up did not have clinical outcome data available, but were kept in the cohort for assessment of injury characteristics. Results: Thirty-two patients, 21 distal femoral avulsions and 11 proximal tibia and fibula avulsions, met inclusion criteria. The distal femoral avulsions occurred in 17 males and 4 females with an average age of 13.9 years (range 11 – 17 years). There were 11 MCL avulsions, 5 popliteus avulsions, 2 FCL avulsions, and 3 combined FCL and popliteus avulsions. Nine distal femoral avulsions also had an associated ACL tear (43%). The most common mechanisms of injury were football (9 patients, 43%), falls (5 patients, 24%), and soccer (4 patients, 19%). Average time from injury to presentation to orthopaedics was 7 days (range 0 – 20 days). Physes were open in 18 patients (86%). Thirteen patients were treated operatively and 8 patients were treated non-operatively. Of the operatively treated patients, 4 (31%) had surgery for their associated ACL or meniscal injury but non-operative treatment of the distal femoral avulsion. Treatment of the avulsions included repair in 7 patients, ORIF of the avulsion in 1 patient, and ligament reconstruction in 1 patient. Average time from injury to surgery was 36 days (range 7 – 62 days). Eleven patients (52%) had sufficient follow-up (mean 20 months, range 3 – 47 months) to document clinical outcome measures. Of these, all had full range of motion and returned to sports, and 10 (91%) had no varus or valgus instability at final follow-up. One patient (9%) had residual varus instability following FCL and popliteus repair. All proximal tibia and fibula avulsions occurred in males, with a mean age of 15.4 years (range 12 – 20 years). There was 1 FCL avulsion, 1 popliteus avulsion, 1 iliotibial band avulsion, 2 biceps femoris avulsions, 3 combined FCL/biceps avulsions, 1 combined FCL/biceps/iliotibial band avulsion, and 2 MCL avulsions. Associated injuries included 3 ACL tears, 2 midsubstance FCL tears, 2 medial tibial plateau fractures, 1 PCL tear, and 1 peroneal nerve neuropraxia. Mechanisms of injury included sports (football, baseball, basketball, track, and skating) in 8 patients (73%) and high-energy trauma (pedestrian vs auto and fall from height) in 3 patients (27%). Average time from injury to presentation to orthopaedics was 5 days (range 0 – 15 days). Physes were open in 7 patients (64%). Six patients were treated operatively and 5 patients were treated non-operatively. Surgery included repair of the biceps and FCL avulsions in all patients. Average time from injury to surgery was 15 days (range 12 – 22 days). Six patients had sufficient follow-up (mean 14 months, range 3 – 52 months) to document clinical outcome measures. One operatively treated FCL and biceps femoris avulsion had residual grade 2 varus laxity and one non-operatively treated MCL avulsion had residual grade 1 valgus laxity at final follow-up. All patients had full range of motion. Conclusions: Ligament and tendon avulsion fractures of the distal femur and proximal tibia and fibula in adolescents are uncommon injuries previously described only as case reports. In this multicenter case series we describe these injuries in 33 patients. The majority of injuries occurred in adolescents with open physes 13 – 16 years of age in association with sports or high-energy trauma. It is important for physicians to scrutinize radiographs of the knee in skeletally immature patients to potentially diagnose and treat these injuries in a timely fashion. The heterogeneity of the treatment and outcomes of these complete injuries highlights the importance of the development of an algorithmic approach to the diagnosis, treatment, and outcomes assessment and will be a future endeavor of this research interest group.