Tibial Tubercle Avulsion

Etiology

Tibial tubercle fractures are most frequently seen in sports that involve jumping activities. Injury may be caused by quadriceps contraction during knee extension such as initiating a jump. Damage can also take place during landing when the quadriceps contracts and the knee flexes to absorb the impact of landing.[2] The patellar ligament inserts on the secondary ossification center, which places the tibial tubercle at risk for an avulsion injury.[1]

Epidemiology

Tibial tubercle avulsion fractures occur most commonly in adolescents. The average age of the patient sustaining a tibial tubercle avulsion fracture is 14.6 years old at the time of injury.[3] Closure and union of the secondary ossification center occur in girls around 10 to 15 years of age and boys at approximately 11 to 17 years of age.[2] Tibial tubercle avulsion fractures occur almost exclusively in boys and are postulated to occur due to increased quadriceps strength.[4] Other causes that are thought to contribute to the incidence of tibial tubercle avulsion fractures in adolescent males are the increased sports participation among male adolescents and the later age at bony fusion.[2] The tibial tubercle apophysis closes from posterior to anterior, medial to lateral, & proximal to distal.[5]

History and Physical

Patients with tibial tubercle avulsion fractures often present with pain in the anterior knee, knee effusion, and hemarthrosis.[2] Patients with a small tibial tubercle avulsion fracture may still have an intact extensor mechanism due to intact retinacular structures. Patients with more extensive tibial tubercle avulsion fractures may have impaired extensor function.[6] A comprehensive physical examination is crucial in the pediatric patient as the history may not be as reliable as in the adult patient. A detailed neurovascular exam is also a requirement as there is a risk of developing compartment syndrome with tibial tubercle avulsion fractures, as discussed below.

Evaluation

The standard evaluation of tibial tubercle avulsion fractures includes AP and lateral radiographs of the knee. As the tubercle is not directly midline on the tibia, slight internal rotation of the tibia will bring the tubercle perpendicular to the cassette and provide a better evaluation of the injury. Patella alta can also be visualized on lateral radiographs.[1][2]

Treatment / Management

The Ogden classification is a modification of the original Watson-Jones classification and is commonly used to describe tibial tubercle avulsion fractures. The following types are subject to revision with an “A” signifying non-displaced fractures and “B” signifying displaced fractures:[6]

• Type I - fracture through the secondary ossification center
• Type II - fracture extends to an area between secondary and primary ossification centers
• Type III - fracture crosses through the secondary and primary ossification centers
• Type IV - fracture through the proximal tibial physis
• Type V - extensor mechanism avulsion

Goals for treatment include the restoration of the articular surface and function of the extensor mechanism.

Clinicians can attempt closed reduction and immobilization for minimally displaced or extra-articular tibial tubercle avulsion fractures. After achieving satisfactory reduction, the leg should undergo immobilization with the knee in extension in a long leg cast or cylinder cast. The cast should include a mold above the patella to aid in the immobilization of the extensor mechanism.[2] Soft tissue injury, including disrupted periosteum, may block efforts at closed reduction and may necessitate conversion to open reduction.[4] Open reduction internal fixation is the treatment method of choice for displaced or intra-articular tibial tubercle avulsion fractures.[2]

Differential Diagnosis

When diagnosing tibial tubercle avulsion fractures, it is important to distinguish between an acute tibial avulsion fracture and Osgood-Schlatter disease, or tibial tubercle apophysitis, which is a chronic condition. At this time, there is no clear consensus regarding whether Osgood-Schlatter disease is or is not a predisposing factor for tibial tubercle avulsion fractures.[2]

Prognosis

A systematic review of the literature by Pretell-Mazzini et al. revealed that prognosis after sustaining tibial tubercle avulsion fractures is excellent, regardless of fracture type.[7] Most patients heal quickly, and function is restored, leading to satisfactory outcomes.[2][8]

Complications

The most devastating complication of tibial tubercle avulsion fractures is compartment syndrome due to injury to the anterior tibial recurrent artery. Injury to this artery leads to filling of the anterior compartment with blood.[9] The classic symptoms of compartment syndrome including pain, pallor, paresthesia, pain with passive stretch, and paresis.[10][11] In children, compartment syndrome may not manifest in the same fashion as in adults. Signs of impending compartment syndrome in the pediatric patient include increasing narcotic requirement, increased anxiety, and restlessness or agitation.[11]

Recurvatum is the most common deformity to occur after tibial tubercle avulsion fractures.[12] This deformity typically presents in younger patients where there is premature closure of the anterior physis while growth continues to occur from the posterior physis.[2]

The most common complication following surgical fixation of tibial tubercle avulsion fractures is bursitis due to painful or prominent orthopedic hardware.[7]