Tibial Tubercle Fractures
- Tibial tubercle fractures result from eccentric loading of the knee extensor mechanism or resisted jumping
- Tibial tubercle fractures frequently require ORIF
- Three dimensional imaging may help guide treatment but is not always necessary
- Compartment syndrome following tibial tubercle fractures may be caused by injury to the anterior tibial recurrent artery
Description:The tibial tubercle is the secondary ossification center of the proximal tibia. The primary ossification center is the tibial epiphysis, and the tibial tubercle extends distally from the anterior aspect of the proximal epiphysis and serves as the point of attachment of the patellar tendon. The tubercle often appears fragmented on radiographs during its development and the ossification centers eventually coalesce in the mid-teen years. Tibial tubercle fractures commonly occur in adolescent boys near the end of their growth. Physeal closure occurs from posterior to anterior and proximal to distal in the tubercle apophysis. Concurrently, it is closing from medial to lateral in the coronal and axial planes.
Epidemiology:Tibial tubercle fractures most commonly occur in adolescent boys aged 12-16 years. They account for only 1% of pediatric fractures (Pandya, 2012).
Clinical Findings:Patients usually have a history of injury and pain in the anterior knee. There may or may not be associated deformity. Hemarthrosis may be present in more severe fractures with intraarticular involvement. An extensor lag or extensor deficiency is present in more severe injuries. It is important to appreciate the amount of soft tissue damage and periosteal stripping that can be associated with these injuries (Wiss, 1991). Compartment syndrome and vascular injury can occur after a tibial tubercle fracture; therefore, a careful physical exam, including detailed neurovascular exam, is essential. Extended observation is frequently recommended to ensure a compartment syndrome does not develop.
Imaging Studies:The initial work up for a suspected tibia tubercle fracture includes AP and lateral radiographs of the knee. Three dimensional imaging (CT and MRI) may be utilized to better characterize these fractures and provide the treating surgeon with information that may alter the surgical approach, including the need for concomitant arthroscopy or open arthrotomy (Pandya, 2012). CT or MRI may also be useful in the diagnosis of Type 1 fractures, especially in those patients with pre-existing Osgood-Schlatter's disease.
Treatment:Nondisplaced fractures may be treated in extension with a brace, cylinder cast, or a long leg cast for 4-6 weeks. Displaced fractures require operative treatment, with screw fixation of the fragment to the tibial metaphysis, although suture fixation via drill holes or suture anchors may be necessary if there is substantial fragment comminution. With displaced fragments, open reduction and internal fixation is required to obtain an anatomic reduction. With greater displacement, the patellar tendon insertion and extensor retinaculum can also be disrupted, and additional soft tissue repair may be necessary.
With intraarticular involvement, an open reduction with an arthrotomy or arthroscopy is performed in order to assess joint congruity, soft tissue entrapment, and to address any associated intraarticular pathology (eg. meniscal tears). Postoperatively, patients are usually treated in a long leg cast or knee immobilizer for 4-6 weeks with restricted weight bearing and activity, allowing progressive knee flexion based upon fracture characteristics and fixation stability.
Complications:There is a high risk of compartment syndrome due to the potential for avulsion of branches of the anterior tibial recurrent artery at the level of patellar tendon insertion (Pape, 1993). Frequent serial examinations should be performed, and if there is a high suspicion for compartment syndrome, then compartment pressures should be measured and/or a fasciotomy performed. Failure to properly diagnose and treat compartment syndrome can result in severe permanent disability and sometimes amputation. Rates of compartment syndrome have been reported as high as 20% in tibial tubercle fractures (Frey, 2008). Prophylactic fasciotomy at the time of internal fixation may be performed at the discretion of the surgeon.
Because most patients with this injury are approaching skeletal maturity, complications related to subsequent growth are rare. However, genu recurvatum is possible and monitoring with serial radiographs of the knee beyond fracture healing should be considered. This may occur due to arrest of the anterior proximal tibial physis as the posterior physis continues to grow, thus decreasing the tibial slope (Hresko, 1989).
Other complications include symptomatic, prominent implants that may require hardware removal. Failure to adequately reduce an intra-articular component of the fracture may lead to post-traumatic arthritis. Knee stiffness may occur following this injury and may be exacerbated by prolonged immobilization.
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