Tibial Tubercle Avulsion
- Author: Janos P Ertl, MD; Chief Editor: Carlos J Lavernia, MD, FAAOS more...
Background
A tibial tubercle avulsion fracture is usually an injury to the knee occurring in adolescence, during the transitional phase of physeal closure just prior to completion of growth. This fracture most often is an isolated injury related to push-off or landing while jumping as the quadriceps eccentrically contracts to support the individual's weight. See the images below.
Diagrammatic view of tibial tubercle avulsion classification types I, II, and III. 
Anteroposterior view of a type II tibial tubercle avulsion. The injury could be missed if a lateral view is not obtained. 
Type III tibial tubercle avulsion. Note intra-articular fracture extension and anterior elevation. The fracture tracks through the proximal tibial epiphysis and may extend into the anterior portion of the knee joint. The proximal tibia physis closes from posterior to anterior, and the fracture pattern is dependent on the amount of physeal closure present at the time of injury. Some authors consider this injury to be a variant of a Salter-Harris III fracture pattern. Open reduction and internal fixation is recommended, as reduction is difficult to maintain against the pull of the quadriceps muscle.
Problem
The difficulty with this fracture is in maintaining a satisfactory reduction against the proximal pull of the quadriceps muscle. The patient usually is very close to the end of growth, and fixation of the fragment should not affect remaining growth. In the rare instance in which this fracture occurs in a younger individual, suturing of the periosteum and retinaculum and temporary smooth Kirschner wire (K-wire) fixation may be performed.
Tibial tubercle avulsions have been classified as types I, II, and III. See the image below.
Diagrammatic view of tibial tubercle avulsion classification types I, II, and III. Type I injuries demonstrate minimal displacement and often can be treated with cast immobilization. Type II lesions maintain an intact superior contact between the avulsed portion of the tibial tubercle and the remaining portion of the tibial epiphysis. The articular surface of the knee is not disrupted. In type III injuries, the fracture extends through the articular surface of the knee with occasional meniscal disruption. Type II and III injuries require stabilization of the extensor mechanism through an open technique to replace the fragment and to remove any interposed periosteum. In type III injuries, exploration of the knee joint is necessary to address intra-articular comminution and meniscal pathology.
Epidemiology
Frequency
Tibial tubercle avulsion fractures are commonly seen in athletic males (frequently basketball players) aged 14-16 years.[1] These fractures account for 1-3% of physeal injuries.
Etiology
The mechanism of injury usually is an indirect force caused by sudden contraction of the quadriceps muscle. During sudden acceleration and deceleration forces, the quadriceps mechanism forcefully contracts against the patellar tendon insertion. When the force is greater than the strength of the tibial tubercle physis, a fracture is created, leading to avulsion of the tibial tubercle. Additional predisposing factors include patella baja, tight hamstrings, preexisting Osgood-Schlatter disease, and disorders involving physeal abnormalities.[2]
Pathophysiology
The tibial tubercle physis is in continuity with the tibial plateau. The physis progressively fuses from posterior to anterior, making it most vulnerable to avulsion in adolescents aged 13-16 years.
Presentation
The physical examination reveals swelling and tenderness over the anterior tibia. A palpable bone fragment and hemarthrosis may be present. With severe displacement, a high riding patella and loss of active knee extension are present.
Indications
Although a type I fracture may not be displaced, it is difficult to maintain this reduction against the pull of the quadriceps muscle. Close observation in the first 2 weeks is necessary. Often, percutaneous or open reduction can be performed to maintain motion within the knee.
Displaced types II and III avulsion fractures require operative fixation because of loss of the extensor mechanism length, tension, and continuity.[3, 4, 5] See the images below.
Anteroposterior view of a type II tibial tubercle avulsion. The injury could be missed if a lateral view is not obtained. Type III tibial tubercle avulsion. Note intra-articular fracture extension and anterior elevation. 
Intraoperative view after open reduction and internal fixation of a type III tibial tubercle avulsion. Type III fractures may demonstrate articular comminution and possible meniscal disruption requiring meniscal repair.
Relevant Anatomy
The proximal tibia physis progressively closes from posterior to anterior. The tibial tubercle is vulnerable to injury during the transitional phase of closure.
Contraindications
Type I fractures are minimally displaced and may be treated with cast immobilization. However, close observation is required.
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