BACKGROUND:
Adolescent tibial tubercle fractures are uncommon, complex, high-energy injuries. The use of lateral radiographs in isolation to diagnose and treat these injuries is the standard of practice. However, with a single 2-dimensional (2D) view, there may be a risk that the degree of injury can be underestimated. This study was performed to report on the outcomes of tibial tubercle fractures operatively treated, determine the utility of a single lateral x-ray to accurately document injury severity and pattern, delineate the role of advanced imaging and intraoperative arthroscopy/arthrotomy in injury treatment, and propose a new classification system of tibial tubercle fractures that accounts for the complex 3D nature of proximal tibial physeal closure, and recognizes the importance of intra-articular extension, providing guidance for intervention.

METHODS:
A retrospective review of operatively treated tibial tubercle fractures at our institution from 2003 to 2010 was performed. Child age, weight, mechanism of injury, Ogden classification (x-ray), advanced imaging results [computed tomography (CT)/magnetic resonance imaging (MRI)] including intra-articular fracture patterns, surgical techniques, intraoperative articular findings, and postoperative complications were collected. In addition, we classified all of our patients into a new classification system (type A--tubercle youth, type B--physeal, type C--intra-articular, type D--tubercle teen) based on a combination of plain radiograph (anteroposterior and lateral), advanced imaging (CT/MRI), and intraoperative arthrotomy/arthroscopy findings.

RESULTS:
We found 41 tibial tubercle fractures in 40 children (all of whom were male) with a mean age of 15.0 ± 1.1 years, and mean weight of 80.3 ± 23.4 kg. Injuries mostly occurred during jumping activities. At initial presentation, compartment syndrome or vascular compromise was seen in nearly 10% of patients, all of whom had type B--physeal injuries under our new classification system. Fifty percent of injuries were underestimated and/or not appreciated by lateral x-ray alone. In patients with intra-articular involvement, consistent 3D fracture patterns were seen on CT including anterior fragments (sagittal plane), lateral fragments (coronal plane), and anterolateral fragments (axial plane). Our new 4 part classification system was able to classify all fractures: type A (2 patients, mean age, 12.7 ± 0.2 y), type B (13 patients, mean age, 14.8 ± 0.7 y), type C (22 patients, mean age, 15.3 ± 1.1 y), and type D (2 patients, mean age, 15.5 ± 0.1 y). All fractures achieved radiographic union with 2 patients (type A--tubercle youth and type B--physeal) requiring additional procedures due to premature physeal closure.

CONCLUSIONS:
Tibial tubercle fractures represent high-energy injuries with potentially devastating complications such as compartment syndrome and/or vascular compromise. Intra-articular involvement is often missed with the use of plain x-ray and drastically underestimates injury severity. The use of preoperative CT scan or MRI should be utilized as adjunct to plain lateral radiograph. If intra-articular involvement is recognized preoperatively, arthroscopy or open arthrotomy should be utilized at the time of surgery. Our new classification system is rooted in the development of the proximal tibia, accounts for intra-articular involvement, and provides guidance for treatment.

LEVEL OF EVIDENCE:
Level III--diagnostic study.



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