Anterior tibial spine fractures are rare, occurring with an incidence of 3 per 100,000 per year.1,2 Historically, this fracture has occurred more frequently in children,3-5 and was considered a condition of skeletal immaturity and the pediatric equivalent of an anterior cruciate ligament (ACL) rupture.6 However, recent literature indicates that this fracture is more common in the adult population than previously thought.7 The tibial spine is an attachment point for the ACL and an avulsion may produce ACL laxity,8 predisposing to further symptomatic laxity and premature osteoarthritis. Nearly 40% of these fractures are associated with concomitant injuries to surrounding structures.9
Meyers and McKeever10,11 originally classified these fractures into 3 groups on the basis of displacement. Type I fractures present with no significant displacement of the anterior margin, type II involve displacement and are hinged, while type III have complete displacement.10,11 More recently, a type IV fracture has been added, involving comminution of the displaced fragment. Nondisplaced fractures are commonly treated with immobilization in varying degrees of extension; this allows the femoral condyles to compress and to reduce the fracture while arthroscopic or open reduction is the preferred method for displaced fractures of the tibial spine.2,4,8,10
We report the case of an 11-year-old boy with a tibial spine fracture that failed conservative management. He developed a subsequent malunion with impingement anteriorly of the tibial spine on the notch, and residual instability of the ACL. The patient’s parents provided written informed consent for print and electronic publication of this case report.
Case Report
An 11-year-old Caucasian boy was referred to our office for evaluation of right knee injury. He sustained the injury approximately 3 months earlier, and it was determined that he had a tibial spine fracture. Conservative management with immobilization in extension and activity modification was undertaken; however, he was referred for further evaluation because of healing in a malreduced position and residual ACL laxity. Physical examination showed a grade 2A Lachman test (contralateral limb with negative Lachman examination), negative McMurray test, and pain with forced hyperextension; range-of-motion examination showed lack of the terminal 5º of extension. Magnetic resonance and computed tomography imaging from an outside facility showed a skeletally immature individual with a large tibial spine fracture that had healed in a malunited position with the fragment extended on a posterior hinge, creating a large prominence anteriorly (Figures 1A, 1B). Magnetic resonance imaging showed that the ACL fibers were likely to remain intact but would lack appropriate tension secondary to the displacement of the tibial insertion.
Because of healing in a displaced position, lack of terminal extension, ACL laxity, and subjective complaints of pain, we discussed surgery with the patient and his parents (Figures 2A, 2B). Four months after the initial injury, the patient underwent surgery for a right tibial spine malunion arthroscopic takedown and repair, as well as an intraoperative evaluation of the ACL. Standard arthroscopy was performed, using anterolateral and anteromedial arthroscopic portals, and an accessory medial peripatellar portal. During surgery, a large prominence was noted in the region of the anterior tibial spine (Figure 3A). The ACL fibers maintained a slack position secondary to the elevation of the tibial insertion point, and intraoperative Lachman examination showed anterior translation of the tibia on the femur as the slack was removed from the ACL. During surgery, impingement of the anterior tibial spine along the femoral notch was shown to be significant by taking the knee into near-full extension (Figure 3B). A cam-like effect was noted at the time of impingement with the posterior soft tissues relaxing to accommodate slight further extension.
Based on these findings, we chose to take down the malunited fracture and repair it (Figure 3C). PDS suture (Ethicon, Somerville, New Jersey) was temporarily placed along the intermeniscal ligament and anterior horns of the medial and lateral menisci, using a system of spinal needles to facilitate suture passage. Surgical clamps were hung from the suture to provide traction on the sutures throughout the case, allowing the intermeniscal ligament and menisci to recede anteriorly to improve working space and aid in preventing iatrogenic injury. These sutures were removed at the conclusion of the case. Using a combination of curettes, elevator, and small shaver, we were able to meticulously remove interposed malunited callus to allow for mobilization of the displaced fragment. After removal of the excess bone formation, a typical donor site was created, allowing the displaced spine fragment to be hinged into appropriate alignment (Figure 3D). We were able to maintain a posterior cortical hinge to facilitate this process.