Tibial tubercle fractures are a relatively uncommon pediatric fracture and account for less than 1% epiphyseal injuries. Of all proximal tibial fractures, approximately 3% are tibial tubercle avulsion fractures.  There are four stages of tibial tubercle development: cartilaginous, apophyseal, epiphyseal, and bony union. The cartilaginous stage exists before the development of a secondary ossification center. The apophyseal stage occurs when a secondary ossification center appears, at approximately 8 to 14 years of age. The apophysis coalesces with the proximal tibial epiphysis during the epiphyseal phase. In the final stage, bony union and closure of the physis occur during years 10 to 15 in girls and 11 to 17 in boys.
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. The patellar ligament inserts on the secondary ossification center, which places the tibial tubercle at risk for an avulsion injury.
Tibial tubercle avulsion fractures occur most commonly in adolescents. The average age of the patient sustaining a tibial tubercle avulsion fractures it 14.6 years old at the time of injury. 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. Tibial tubercle avulsion fractures occur almost exclusively in boys and are postulated to occur due to increased quadriceps strength.  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. The tibial tubercle apophysis closes from posterior to anterior, medial to lateral, & proximal to distal.
Patients with tibial tubercle avulsion fractures often present with pain in the anterior knee, knee effusion, and hemarthrosis.  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.  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.
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.
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:
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 immobilization of the extensor mechanism. Soft tissue injury, including disrupted periosteum, may block efforts at closed reduction and may necessitate conversion to open reduction. Open reduction internal fixation is the treatment method of choice for displaced or intra-articular tibial tubercle avulsion fractures.
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.
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. The classic symptoms of compartment syndrome including pain, pallor, paresthesia, pain with passive stretch, and paresis. In children, compartment syndrome may not manifest in the same fashion as adults. Signs of impending compartment syndrome in the pediatric patient include increasing narcotic requirement, increased anxiety, and restlessness or agitation.
Recurvatum is the most common deformity to occur after tibial tubercle avulsion fractures. 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.
The most common complication following surgical fixation of tibial tubercle avulsion fractures is bursitis due to painful or prominent orthopedic hardware.
Maintaining a proper, healthy weight and consuming a balanced diet rich in calcium and vitamin D is vital for bone health. Additional information for patients and their families regarding tibial tubercle avulsion fractures is on the website for McLane Children’s Baylor Scott & White.
Treating the pediatric patient with a tibial tubercle avulsion fracture is a multidisciplinary effort that involves coordination between pediatric hospitalists, orthopedic surgeons, nursing staff, physical and occupational therapists as well as child life staff. Each member of the healthcare team is essential in educating the patient and family regarding the patient's condition. It is critical that nursing staff understand the signs of impending compartment syndrome in pediatric patients and have early communication with physicians when concerns arise. If a staffing member has a concern regarding compartment syndrome, the patient should always be evaluated in a timely fashion. [Level 3] Monitoring, communication, and treatment of this severe potential complication are essential in the management of tibial tubercle fractures.
In summary, the diagnosis and management of tibial tuberosity avulsion injuries require an interprofessional team approach, including physicians, specialists, specialty-trained nurses, physical therapists, and pharmacists, all collaborating across disciplines to achieve optimal patient results. [Level V]
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