Practice Essentials
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. [1, 2] This fracture most often is an isolated injury related to pushoff or landing while jumping as the quadriceps eccentrically contracts to support the individual's weight.
The fracture tracks through the proximal tibial epiphysis and may extend into the anterior portion of the knee joint. The proximal tibial 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 with internal fixation (ORIF) is recommended because reduction is difficult to maintain against the pull of the quadriceps muscle.
An extended classification system was developed that included types I, II, III, IV, and V. Types I, II, and III were described by Watson-Jones; these were further divided into A, B, and C subtypes, with A indicating displacement, B indicating comminution, and C (added by Frankl) indicating associated patellar ligament avulsions. For classification of more extensive injury, type IV was introduced by Ryu and type V by Mckoy. [3]
For all fracture types, ice therapy, splint immobilization, and elevation should be initiated to avoid significant swelling. Type I fractures generally can be treated with cast immobilization; often, percutaneous or open reduction can be performed to maintain motion within the knee. Types IB, II, and III tibial tubercle fractures require ORIF. In type III injuries, exploration of the knee joint is necessary to address intra-articular comminution and possible meniscal pathology.
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.
Anatomy
The proximal tibia physis progressively closes from posterior to anterior. The tibial tubercle is vulnerable to injury during the transitional phase of closure.
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.
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. [4]
Epidemiology
Tibial tubercle avulsion fractures are commonly seen in athletic males aged 14-16 years who engage in sporting activities that involve jumping, sprinting, or both (eg, basketball). [5, 6] These fractures account for approximately 3% of all proximal tibia fractures and fewer than 1% of physeal fractures. [7] Their incidence in children, though still low, appears to be increasing, possibly because of greater participation in high-level athletics. [8] Bilateral tibial tubercle avulsion fractures may occur but are quite rare. [9]
Prognosis
With appropriate surgical treatment and postoperative therapy, a complete recovery without residual symptoms is expected. [7] A return to sports may be expected once the strength of the affected lower extremity reaches 90% of that of the unaffected extremity (usually 4-6 mo after injury).
In a systematic review of the English-language literature on pediatric tibial tubercle fractures from 1970 to 2013, Pretell-Mazzini et al examined treatment outcomes (functional and radiologic) and complications. [10] Clinical outcomes were evaluated on the basis of qualitative assessment, return to preinjury activity, and range of motion (ROM) in the knee. Fracture healing, associated injuries, compartment syndrome, and complications were assessed as well.
In this study, 98% of surgical cases were treated with ORIF. [10] Fracture consolidation was accomplished in 99.4% of cases, and 98% of patients, regardless of fracture type, were able to return to preinjury activity and regain knee ROM. The overall complication rate was 28.3%, with the most frequent complication being removal of an implant because of bursitis (55.8%), followed by tenderness/prominence (17.9%) and refracture (6.3%). The incidence of compartment syndrome was 3.57%. The authors noted the need for longer follow-up to determine long-term outcomes.
In a retrospective study of 10 male adolescents (age < 18 y; median age, 15 y) treated for tibial tubercle avulsion fractures (TTAFs), Lima et al evaluated knee ROM, pain, return to sports, overall satisfaction, functional outcomes, and complications. [11] Nine patients were treated surgically with reduction and fixation with cannulated screws or K-wires, along with treatment of associated injuries. Eight patients were able to regain their previous level of sports activity. Mild recurvatum developed in one patient, and minor decreased knee flexion was noted in two.
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Diagrammatic view of tibial tubercle avulsion classification types I, II, and III.
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Type III tibial tubercle avulsion. Note intra-articular fracture extension and anterior elevation.
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Anteroposterior view of a type II tibial tubercle avulsion. The injury could be missed if a lateral view is not obtained.
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Intraoperative view after open reduction and internal fixation of a type III tibial tubercle avulsion.
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Extended classification system for tibial tubercle avulsion injury.
