Children and adolescents are increasingly involved in competitive sporting activities, and as such, there continues to be a need to understand the sport-related injuries affecting the pediatric age population. Tibial spine fractures (also known as tibial eminence fractures) are a type of knee injury that most commonly occur in children and adolescents. Tibial spine fractures are best described as a bony avulsion of the anterior cruciate ligament (ACL) from its insertion on the intercondylar eminence of the tibia. Although these type of fractures have a low prevalence in the general population (incidence of approximately 3 per 100,000 per year¹⁾, they have been estimated to represent 2% to 5% of knee injuries in children and adolescents presenting with a knee effusion.²,³ Inadequately treated tibial spine fractures can have deleterious effects on the function, quality of life, and health of the pediatric patient.

In this chapter, we provide an overview of tibial spine fractures and we present a technique for arthroscopic internal fixation using screw fixation. The method presented in this text is one method used by the senior author for the treatment of this condition.

The tibial spines are bony prominences in the middle of the proximal tibia. The medial spine structure serves as the attachment site of the ACL. The broad attachment of the ACL fans out from the tibial spine and confluences with anterior horn of the medial and lateral meniscus.⁴,⁵,⁶

Epidemiologic studies suggest that motor vehicle and sporting accidents (fall during skiing and fall from bike) are the most common causes of the index injury in the pediatric population.⁷,⁸ The mechanism of injury for tibial spine avulsion fractures is thought to be similar to that for intrasubstance ACL tears where patients hyperextend the knee with a valgus or rotational force.⁹,¹⁰ However, in children, tibial spine avulsion fractures occur because the tibial plateau has an incompletely ossified tibial plateau and because the ACL is stronger than its bony attachment; the bone is the point of failure when a pathophysiologic tensile load is applied. Some authors have postulated that prior to bone failure, an in situ stretch phenomenon can occur on the ACL, thereby resulting in some ligamentous laxity of the ACL even after appropriate fracture fixation.¹¹

In this chapter, we discuss this unique injury for the pediatric and adolescent population; however, it should be noted that tibial spine fractures are being increasingly recognized in the adult population. One prior study proposed a higher prevalence of tibial spine fractures in the adult population than had been previously recognized.¹² There has since been continuing recognition of this fracture entity in the adult population.¹³ Among adults, tibial spine fractures appear to be more common in women.¹⁴ As such, one proposed mechanism for the occurrence of tibial spine fractures in adults is that osteopenic bone quality in adults leads to a similar injury pattern as is found in children and thus failure occurs at the bone with pathophysiologic load application on the ACL.

As with any patient encounter, a thorough history and physical is a critical first step in evaluating the patient presenting with possible tibial spine fracture. Tibial spine fractures should be suspected in a skeletally immature individual presenting to clinic with painful knee hemarthrosis, decreased range of motion (ROM), and difficulty with weight bearing. History will likely be positive for a sporting or traumatic maneuver in which the leg is forcefully loaded often with a valgus stress. As with
ACL injuries, these patients will similarly feel a “popping” sensation; however, unlike ACL disruption, the “pop” is the breach of the tibial spine integrity and the ACL pulling the tibial spine away from the tibia. Physical examination should also include a thorough examination of the knee, being careful to detect any associated injury.

Radiographic assessment of the knee should include standard anteroposterior (AP), lateral, and tibial tunnel views of the knee (Figs. 32.1 and 32.2). Lateral views of the knee are useful in determining the degree of displacement of the fracture fragment and tibial tunnel views can assist in further defining subtle fractures in the AP plane (see Fig. 32.2). Contralateral view of the knee may be helpful as a comparison not only to define normal anatomy in this region but also to disaggregate tibial spine fractures from fractures of the inferior pole of the patellar or femoral condyle.

Some may choose to get additional diagnostic studies such as a computed tomography (CT) scan, which has been shown to have some use in better defining fracture characteristics as well as degree of comminution.¹⁵ CT studies, however, are not part of the routine workup of tibial spine fractures at our institution. A high rate of concomitant injury with tibial spine fractures has been reported in the literature.¹⁶,¹⁷ As such, magnetic resonance imaging (MRI) for further radiographic assessment of tibial spine injuries is recommended. MRI is useful in preoperative planning for assessing the structural integrity of the knee and ruling out interstitial injury of the ACL. Furthermore, MRI defines the fracture fragment compared to soft tissue structures (Fig. 32.3). This information is informative regarding potential obstacles to fracture reduction. One prior study reported on the MRI findings associated with tibial spine fractures.¹⁶ Associated injuries include intrasubstance ACL and posterior cruciate ligament injuries, medial collateral ligament tears, posterior lateral corner injury, and meniscal tears—specifically meniscal entrapment within the spine fracture segment.

Tibial spine avulsion fractures are most commonly classified based on an algorithm devised by Meyers and McKeevers.¹⁸ The classification scheme relies on the degree of displacement of the avulsed fragment from the fracture base. In this fracture scheme, tibial spine fractures are classified from types I to III, with type I being the least displaced and type III the most.