ANATOMY

The tibia is the primary weight-bearing bone of the knee joint. The most proximal aspect of the tibia is comprised of the medial and lateral tibial condyles. The articular surfaces of the condyles are the medial and lateral tibial plateaus, which articulate with the corresponding medial and lateral femoral condyles. The plateaus are separated by the intercondylar eminence, which serves as the site of attachment for the anterior and posterior cruciate ligaments and the fibrocartilaginous menisci.⁴ Specifically, the midpoint of the intercondylar eminence serves as the distal attachment of the ACL.

The mechanism of injury for tibial eminence fractures is similar to an ACL tear; however, it involves an avulsion fracture at the ACL insertion. The injury may be associated with valgus and external rotation. It is often seen in skiers and is related to a boot-induced injury after the skier lands on the tail of the ski or to the phenomenon referred to as a “phantom foot” injury, which involves forced internal rotation with knee flexion. Although seen frequently in skiers, it is also seen in other sports, bicycle accidents, motor vehicle accidents, and pedestrian versus motor vehicle injuries.

Tibial eminence fractures are seen in children usually between the ages of 8 and 15 years.^3,5,6 Although this fracture pattern is commonly associated with a childhood injury, it is also seen in adults.^2,7,8 It is theorized that this occurs more commonly in children because of the relative weakness of the incompletely ossified tibial eminence as compared with the fibers of the ACL. It has also been proposed that the injury occurs secondary to greater elasticity of the ligaments in younger people.⁹

PATIENT EVALUATION

Classification

Meyers and McKeever first described the classification scheme for tibial eminence fractures in 1959.² Their classification divides these fractures into three types based on displacement of the avulsed fracture fragment (Fig. 2-1). Type I represents a nondisplaced or minimally displaced fracture at the anterior margin. Type II fractures involve the anterior third or half of the avulsed bone displaced proximally, with an intact posterior hinge resembling a bird’s beak. Type III fractures have a completely displaced fracture. These have been further subdivided into IIIA and IIIB fracture classifications.¹⁰ Type IIIA fractures involve the ACL insertion only, whereas the IIIB type includes the entire intercondylar eminence. Some have labeled comminuted fractures as type IV.¹⁰

FIGURE 2-1 Meyers and McKeever classification of tibial intercondylar eminence fractures.

(Adapted from Lubowitz JH, Elson WS, Guttman D. Part II: Arthroscopic treatment of tibial plateau fractures: intercondylar eminence avulsion fractures. Arthroscopy. 2005;21:86-92.)

Associated injuries with fractures of the tibial eminence are common. Meniscus injuries are the most common injuries seen; however, these fractures may be associated with chondral and ligamentous injuries as well.^11,12 In an unpublished study, we found an interposed intermeniscal ligament in 80% of types II and III injuries. This has profound implications for treatment strategies. In addition, tibial eminence fractures are also seen with tibial plateau fractures, specifically Schatzker types V and VI fractures.¹³

TREATMENT

The goal for management of tibial eminence fractures should be no different than for any other intra-articular fracture. Anatomic reduction and rigid fixation that allow for early range of motion should be the treatment for these fractures. Debate has ensued over anatomic reduction versus overreduction. It has been proposed that overreduction may result in excessive tension of the ACL, which results in limited knee range of motion.¹⁴ Others have countered this by stating that plastic deformation of the ACL occurs prior to the avulsion fracture and thus overreduction would result in a better outcome.⁹ Numerous studies have documented residual laxity in well-reduced tibial eminence fractures, and most have concluded that the laxity is not symptomatic.^15–17 More studies are needed to answer the question of anatomic versus overreduction, but there is consensus that any displacement requires at least an anatomic reduction.

Management has been based on the Meyers and McKeever classification, with recommendations for immobilization in extension for type I fractures. Some controversy exists in regard to what degree the knee is to be extended for nonoperative management. Meyers and McKeever have recommended immobilization in 20 degrees of flexion.^2,8 Similarly, Beaty and Kumar have recommended immobilization in 10 to 15 degrees of flexion.¹⁸ Fyfe and Jackson based their recommendations of flexing the knee to 30 to 40 degrees because the ACL is taut in extension and, with some flexion, the tension on the avulsion fragment would be less.¹⁹ These authors favor immobilization in full extension to avoid a flexion contracture, which can occur if the knee is kept in a flexed position. We encourage straight leg raises and quadriceps isometrics and allow full weight bearing, as tolerated, in a brace locked in full extension. The knee should not be immobilized in hyperextension because extensive stretch on the popliteal artery may result in a compartment syndrome.¹³ Regardless of the position of immobilization, close follow-up with radiographs weekly for 4 weeks should help confirm maintenance of reduction.

Treatment of type II fractures has been controversial. Closed reduction may be attempted by aspiration of the hemarthrosis and knee extension performed to allow the femoral condyles to help reduce the fracture.²⁰ Anteroposterior and lateral radiographs should be taken to verify reduction and, with difficult visualization, CT or MRI should be performed. Often, anatomic reduction is not achieved secondary to interposition of the medial meniscus, lateral meniscus, or intermeniscal ligament. Persistent displacement, despite attempted reduction maneuvers, warrants arthroscopic evaluation and treatment. Many reports have identifed associated soft tissue injuries, including chondral, meniscal, and ligamentous structures. The need for anatomic reduction of these fractures to allow for postoperative stability and motion, combined with the need to identify and treat these associated injuries, make arthroscopic evaluation necessary for successful treatment of most type II and all type III fractures.^16,21–24 These authors also think that most, if not all, type II fractures were likely a type III level of displacement at the time of disruption. Based on that, we take an aggressive operative approach to most type II injuries.

Closed reduction may be attempted for type III injuries, but anatomic reduction and maintenance of reduction are difficult. Most experts agree that type III fractures require reduction and fixation.^13,25,26 Arthroscopic reduction and fixation of these injuries have become the standard of care and has made open reduction and internal fixation a treatment that is infrequently necessary or used.

Techniques involving the use of cannulated screws or suture have been described and the results with either method have been excellent. Risks of cannulated screw placement involve comminuting the fracture fragment, crossing the physis with a screw, hardware impingement necessitating removal, and posterior neurovascular injury. Repair using nonabsorbable suture fixation provides the benefit of eliminating these risks and still maintaining an excellent reduction and result.

Arthroscopic Technique

General or epidural anesthesia may be used. The leg is secured in an arthroscopic leg holder and the foot of the bed is flexed. The contralateral leg is supported with a foam pad and abducted to the side to allow fluoroscopy of the involved extremity in both anteroposterior and lateral projections. A tourniquet is placed around the thigh, but is not routinely used. After prepping and draping, an superomedial portal is established. A fluid pump is used to promote hemostasis and adequate visualization. Care is taken to keep pressure relatively low to avoid fluid extravasation. This has not been found to be a problem nor have elevated compartment pressures. An anterolateral portal is established for the arthroscope. The hematoma is evacuated until reasonable visualization is possible. Once pathology can be visualized, an anteromedial portal is established after localization with a spinal needle. An arthroscopic probe is then used to dislodge any clotted blood or debris at the site of fracture (Fig. 2-2).

FIGURE 2-2 A probe is used to hold the fracture site open to débride the clot, intermeniscal ligament, or other debris.

A synovial resector (4.5 mm) is used to débride the region further and to remove any debris from the fracture bed. Once the fracture site has been débrided, the probe is used to attempt a reduction. Interposition of the intermeniscal ligament or the menisci requires use of the probe to hold the soft tissue structures out of the way while attempting to reduce the fragment with an ACL guide or probe. An accessory medial portal is created 1.5 to 2.0 cm medial to the anteromedial portal for the probe. In patients in whom the intermeniscal ligament prevents reduction and also cannot be mobilized, resection is performed. Once the fracture has been reduced, a 0.062-inch Steinmann pin is placed percutaneously from a medial parapatellar position to hold the fracture reduced (Fig. 2-3).

FIGURE 2-3 A probe and Steinmann pin are used to reduce the fracture anatomically.

If there is a large fragment and the piece is large enough to consider placing a cannulated screw, fixation is achieved by using one or two 4.0-mm cannulated screws (Synthes USA, Paoli, Pa). If the Steinmann pin that is holding the reduction is in good position, it may be used as the guide pin for the cannulated screw. If not, a second wire may be placed under fluoroscopic control. The goal is to have the pin(s) just penetrate the posterior cortex of the tibia. Frequent use of fluoroscopy is recommended to ensure accurate placement of the wire and screw and also to make sure that the wire is not being advanced as the screw is placed.

Suture fixation should be used when the fracture is small or comminuted, or in the presence of open growth plates. Some have advocated using the suture methods for all patients because these result in less risk (neurovascular bundle) and less secondary procedures (hardware removal) ^25,26 These authors favor the suture technique in all cases. After the fracture is reduced and held in position with the Steinmann pin, the ACL tibial tunnel guide is used to pass a 2.4-mm guide pin through the anteromedial tibial metaphysis, entering the joint on the medial side of the fragment (Fig. 2-4). A second wire is passed starting 1 to 2 cm lateral to the first hole on the tibial cortex, entering the knee at the lateral side of the fragments (Fig. 2-5). The first wire is removed and, immediately after removal, a Hewson suture passer (Smith & Nephew Endoscopy, Andover, Mass) is passed up the hole and two Ultrabraid sutures (Smith & Nephew Endoscopy) are delivered into its loop through the anteromedial portal and pulled out the anteromedial tibia (Fig. 2-6). The second wire is taken out and the Hewson suture passer is immediately placed into the joint (Fig. 2-7). The opposite end of the ULTRABRAID suture(s) are delivered into its loop and pulled out the tibia (Fig. 2-8). A crochet hook or blunt probe is passed into the subcutaneous tissue through one of the suture holes, hooking the opposite sutures, and pulling them out the same hole. A knot is tied and passed through the skin puncture hole and subcutaneous tissue and is secured tightly to the tibial cortex. Each suture is tied and secured individually (Fig. 2-9). This provides firm fixation of the fracture fragment and can be visualized directly.

FIGURE 2-4 The ACL tibial tunnel guide is used to pass a 2.4-mm wire on the medial side of the fragment.

FIGURE 2-5 A second wire is passed on the lateral side of the ACL.

FIGURE 2-6 The medial 2.4-mm wire is withdrawn, a suture passer is placed in the hole, and two Ultrabraid sutures (Smith & Nephew Endoscopy, Andover, Mass) are passed.

FIGURE 2-7 The lateral 2.4-mm wire is removed, the Hewson suture passer (Smith & Nephew Endoscopy) is passed, and the other ends of the sutures are brought out of the tibial cortex.

FIGURE 2-8 The suture has been passed through both tibial holes. It now holds the ACL and its fracture fragment reduced.

FIGURE 2-9 The sutures are tied through one of the wire holes, leaving no incision along the tibia.

PEARLS& PITFALLS

PEARLS

• Intra-articular fractures result in more bleeding and larger, more painful effusions than ligament or cartilage injuries. Therefore, when an acute knee trauma presents with a tense effusion, look carefully for an intra-articular fracture.

• Intermeniscal ligament interposition occurs in a high percentage of types II and III injuries. Left unattended, this will preclude reduction and healing.

• Meyers and McKeever type II injuries underwent more displacement at the time of injury and were likely type III in most cases.

• Indications for arthroscopic intervention are the presence of radiographic or MRI displacement or pathologic laxity of an examination.

• Hold reduction with a Steinmann pin placed percutaneously from a medial parapatellar position; use fluoroscopy.

• Suture fixation is the preferred method in the skeletally immature and with comminuted or small fragments.

• When passing the sutures through the anteromedial portal to secure the avulsion, using a small (5.5-mm) cannula for suture passage will eliminate the chance of entrapping subcutaneous and capsule tissues.

• If having difficulty pulling sutures out through the puncture created by the 2.4-mm guide pin, make a small longitudinal incision between the two guide pin puncture wounds, retrieve all sutures through this incision, and tie each suture individually.

PITFALLS

• Failure to remove debris from the fracture site will result in nonanatomic reduction and more laxity.

• Poor placement of Steinmann pins or screws may result in injury to the neurovascular structures; use fluoroscopy for all fixation pins and screws.

• Screw fixation may cause physeal arrest; be aware of open physes.

POSTOPERATIVE MANAGEMENT

Patients are placed in a hinged knee brace locked in 0 degrees of flexion for the first 4 weeks and allowed to perform passive or active-assisted range of motion exercises in the prone position through an arc of 0 to 90 degrees. Patients may bear weight as tolerated, with the brace locked at 0 degrees. Crutches are generally discontinued by postoperative day 10. At 4 weeks, the brace is removed, and closed-chain quadriceps exercises are begun. At 8 weeks, easy straight-ahead running is initiated and pivot-twist maneuvers are avoided until at least 12 weeks after surgery.

COMPLICATIONS

Although a good outcome is usually expected for fractures of the tibial eminence, complications do occur. Residual laxity after fixation is commonly found after arthroscopic reduction and fixation. Although multiple studies have reported results verifying positive Lachman tests and a difference in laxity from the contralateral uninjured extremity, most patients have functional stability and are not adversely affected.^7,15-17,27 Evidence of clinical instability warrants revision with ACL reconstruction.

Arthrofibrosis is a potential complication, but is rare if the patient undergoes arthroscopic reduction with fixation, because the goal of the operation is to promote early range of motion. Development of arthrofibrosis warrants aggressive therapy and possible manipulation under anesthesia, with arthroscopic lavage and débridement of adhesions. Loss of full extension can be avoided by immobilization in full extension and attention to quadriceps and hamstring strengthening.

Painful or symptomatic hardware is common with the use of cannulated screws. Loss of full knee extension can occur secondary to scar tissue or a prominent screw in the intercondylar notch. It has been demonstrated that at the time of hardware removal, soft tissue interposition is the rule, and that excision combined with implantation removal results in excellent outcomes.²⁸

CONCLUSIONS

Arthroscopy is a safe and preferable alternative to closed management of types II and III tibial eminence fractures. The arthroscopic examination, reduction, and fixation can be accomplished in almost all patients. In addition, this technique provides superior reduction and fixation when compared with closed or open methods. Almost all patients return to sports at their previous level when treated with arthroscopic reduction and internal fixation, which further supports this as the approach that best predicts a good result.