Gilbert Chan and Lawrence Wells
DEFINITION
Tibial spine fractures are synonymous with an avulsion of the anterior cruciate ligament (ACL) with its attachment on the anteromedial portion of the tibial eminence.16,21 Some authors consider them to be equivalent to the midsubstance ACL injuries seen in the adult population.
This injury commonly occurs in the younger age group, particularly in those with open growth plates.
Tibial spine fractures occur in 3 per 100.000 children each year.18
Meyers and McKeever classified this fracture into three types based on the degree of displacement (FIG 1)14:
Type I is a nondisplaced fracture.
Type II is the hinged, partially displaced type.
Type III is a complete displacement of the fragment.
The classification proposed by Meyers and McKeever was later modified by Zaricznyj to include a fourth type, which would signify a comminuted fragment.22
ANATOMY
The tibial eminence is found lying in the intercondylar area of the tibia (FIG 2).
Two elevations are seen: a medial and a lateral. These elevations are triangular.
The medial elevation provides the attachment for the fibers of the ACL.
There are no structures that attach to the lateral portion of the eminence.
The ligamentous ends of the medial and lateral menisci likewise insert into the intercondylar eminence.
The tibial eminence also serves as an insertion for the posterior cruciate ligament (PCL); the fibers of the PCL typically arise from the posterior portion of the intercondylar eminence.14
In the younger child the majority of the anterior portion of the eminence is cartilaginous.14
PATHOGENESIS
Avulsion of the tibial eminence or tibial spine is usually traumatic in nature. It is more common in children, particularly those with incomplete ossification and open growth plates. The incompletely ossified tibial spine is primarily cartilaginous, which is weaker in resisting tensile forces.
The injury occurs because of a stretching of the ACL. The ACL is much stronger in resisting tensile forces than the immature osteochondral surface; this often results in failure and avulsion of the osteochondral attachment of the ACL.
The usual mechanism of injury is a forced valgus moment applied to the knee, which is coupled with external rotation forces. Other mechanisms reported include hyperextension of the knee coupled with rotational moments.
Different loading mechanisms are likewise implicated in the development of the injury. Experimental models have shown that rapid loading rates result in midsubstance ACL tears, whereas gradual loading results in tibial spine avulsion fractures.16,21
The inherent anatomy of the knee has likewise been implicated. Kocher and colleagues10 compared 25 skeletally immature knees with tibial spine fractures against 25 age-matched skeletally immature knees with midsubstance ACL tears and found a narrower notch width (intercondylar notch) in individuals who had sustained the midsubstance ACL tears.
PATIENT HISTORY AND PHYSICAL FINDINGS
Fractures of the tibial spine are usually precipitated by an acute traumatic event. The clinical presentation usually coincides with the severity of injury.
Usually a patient with a tibial spine injury will have a history of trauma or sports-related injury; the most common mechanism is usually a fall from a bicycle. Lately, sportsrelated injuries have been reported with increasing frequency. High-velocity trauma may also cause tibial spine injuries.
The patient will usually present with a painful swollen knee. Swelling is secondary to hemarthrosis from the intra-articular knee injury.
Knee joint laxity is present, as well as an inability to bear weight on the affected extremity.
The knee should also be carefully examined for any concomitant injury.
Gentle palpation and examination of the knee are under-taken. Most patients have some degree of swelling due to hemarthrosis secondary to the intra-articular fracture. Other superficial injuries are related to the degree and nature of the traumatic event.
FIG 1 • Meyers and McKeever classification. Type I has minimally displaced fragments. Type II has displacement through the anterior portion of the fracture with an intact posterior hinge. Type III has complete displacement of the fracture fragments.
FIG 2 • Axial view of the tibial plateau. A. The intercondylar eminence lies between the medial and lateral condyles. B. The medial portion serves as the attachment of the anterior cruciate ligament.
In the presence of a deficient ACL complex, during the pivot shift test the femur falls posteriorly in relation to the tibia as the leg is raised and rotated internally. The valgus force applied to the leg along with slight flexion of the knee results in the pivot shift phenomenon. The intact iliotibial band reduces the femur when the knee is brought into 20 to 30 degrees of flexion.
A positive anterior drawer test indicates knee joint laxity. However, this is not as sensitive as the Lachman test in assessing for ACL deficiency.
A positive result on the Lachman test indicates deficiency of the ACL complex. The test has greater sensitivity and specificity for ACL tears.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Standard anteroposterior (AP) and lateral views of the knee are usually adequate in making the diagnosis. These views help to define and identify the extent of bony injury.
In lesions that are predominantly cartilaginous, these views may sometimes detect a small piece or a fleck of avulsed bone, which may be indicative of the avulsed osteochondral fragment (FIG 3).
MRI is a good imaging modality for suspected tibial spine injuries, especially in the immature knee, where the tibial spine is predominantly cartilaginous. It differentiates between a true midsubstance ACL injury and a true avulsion fracture of the tibial spine. It also helps to detect concomitant injuries around the knee joint.8
Computed tomography is helpful in the older age group and in cases of severe trauma, where the fracture configuration may be severely comminuted.
FIG 3 • AP and lateral radiographs of the knee showing a displaced tibial spine fracture (type III).
DIFFERENTIAL DIAGNOSIS
ACL tear
Osteochondral lesion
Meniscal injury
Other ligamentous injuries about the knee
NONOPERATIVE MANAGEMENT
Nonoperative management is reserved for nondisplaced type I fractures and reducible type II fractures.
Type II fractures may be reduced by first aspirating the hematoma and injecting a local anesthetic agent into the joint space.
The knee is extended in an attempt to reduce the fracture fragment. The mechanism is through direct pressure exerted by the lateral femoral condyle.
This maneuver may be effective for lesions that are large enough to include part of the tibial plateau.
In small lesions, the maneuver may not afford adequate reduction.
The reduction is assessed with radiographs and the knee is immobilized.
A long-leg cast is placed to immobilize the leg and maintain reduction.
There has been controversy about the optimal position for cast placement.
Previous authors have recommended varying degrees of flexion, ranging from 10 to 40 degrees.3,6,15 The arguments in favor of flexing the knee relate to the relative relaxation of the ACL in flexion.12
We recommend long-leg casting between 10 and 20 degrees of knee flexion.
The reduction should be checked after 1 week and at 2 weeks. Any loss of reduction warrants an operative reduction of the fracture.
SURGICAL MANAGEMENT
The general indications for surgical management of tibial spine fractures include:
Completely displaced tibial spine fractures (type III)
Type II tibial spine fractures with inadequate closed reduction
Preoperative Planning
Careful preoperative evaluation and preparation are always imperative to the success of treatment.
All imaging studies obtained before surgery should be reviewed.
FIG 4 • Position of the knee in the leg holder.
If the avulsed fragment has a relatively large osseous component, plain radiographs will usually suffice in determining treatment.
In lesions that are primarily cartilaginous, MRI may be required to determine the extent of the lesion. Any other lesion noted on imaging studies should likewise be addressed.
A thorough physical examination should be performed under anesthesia.
The choice of surgical treatment (open versus arthroscopic reduction) as well as the choice of fixation device largely depends on the preference and experience of the surgeon and the character of the lesion.
Larger lesions with an adequate osseous component, for example, may allow for screw fixation, whereas a lesion that is primarily cartilaginous may be better treated with suture fixation.
Inevitably, the final decision as to which fixation device is best is made intraoperatively.
The surgeon should be prepared to offer fixation techniques that will provide stable anatomic fixation by open methods or through arthroscopy.
Positioning
For arthroscopic procedures, the position largely depends on the surgeon's preference. A variety of positions can be used.
The leg can be placed on the operating table with the knee joint past the break in the table. This allows the knee to flex 90 degrees when the lower end of the table is dropped down, allowing the knee to dangle off the table. This position can be done with or without a leg holder (FIG 4A).
The leg can be placed supine on the operating table, with the hip flexed and the knee flexed 90 degrees. The knee is allowed to angle off the table as needed (FIG 4B,C).
For open reduction techniques, the patient is placed supine on the operating table, a tourniquet is placed on the thigh, and the knee is draped in a standard fashion. The leg is exsanguinated.
Approach
The standard arthroscopic portals used for ACL reconstruction are used (FIG 5).
For open reduction and internal fixation (ORIF), the knee is approached through a limited parapatellar approach.
FIG 5 •The standard portals used for anterior cruciate ligament reconstruction are the same ones commonly used for arthroscopic treatment of tibial spine fractures.
TECHNIQUES
ARTHROSCOPY-ASSISTED TIBIAL SPINE REPAIR
Arthroscopic Fixation
An anterolateral portal is made for visualization, a superomedial portal is used as an outflow tract, and an anteromedial portal is made for instrumentation.
The hemarthrosis is removed to allow for direct inspection and evaluation of the knee joint.
Any concomitant injuries are identified.
The base of the fracture fragment is débrided using shavers and curettes and the fracture hematoma is carefully removed.
A posterior force is applied to the leg and an attempt is made to reduce the fracture fragments (TECH FIG 1).
TECH FIG 1 • A. Arthroscopic image taken of a type III tibial spine fracture. B. Arthroscopic image showing anatomic reduction of the fracture fragments.
TECH FIG 2 • Arthroscopic screw fixation. A. The fracture fragment is maintained using cannulated guidewires. B,C. A cannulated screw is inserted under fluoroscopic guidance. D,E. AP and lateral radiographs showing the tibial spine fracture fixed with a single cannulated screw with washer. Care should be taken to avoid crossing the physis with the screw.
If any interposing structure is found preventing reduction, it should be carefully retracted and sutured or repaired if necessary.
Midpatellar tendon portals may be added to allow the use of accessory probes and instruments.
Screw Fixation
Once anatomic reduction of the fracture has been achieved, a guide pin is passed through the fracture fragment (TECH FIG 2A,B).
The position of the guide pin is checked under fluoroscopy to ensure proper placement and to avoid traversing the growth plate.
A second pin may be introduced, depending on the stability of the fracture reduction, to maintain the fragments in place.
A screw of appropriate size and length is chosen.
A 3.5-mm or 4.0-mm cannulated, self-drilling selftapping screw is used. The screw size is largely dependent on whether the fracture fragments will accommodate the screw.
One or two screws may be placed, depending on the size of the fragment.
With reduction maintained, the screw is gradually advanced under fluoroscopic guidance, making sure that the growth plate is not traversed.
Once adequate fixation has been obtained, the guide pins are removed.
The knee is gently flexed and extended while the stability of the reduction is checked under direct vision.
AP and lateral radiographs of the knee are taken to document appropriate positioning of the screw and to document the fixation before closure (TECH FIG 2C–E).
Once satisfactory reduction is documented, the instruments are removed and the arthroscopic portals closed.
The knee is placed in a cylinder cast in 5 to 10 degrees of flexion.
Suture Fixation
Two 1-0 PDS sutures are placed at the base of the ACL proximal to its insertion on the tibial spine (TECH FIG 3).
An incision is made 1 to 2 cm medial to the tibial tubercle to allow for placement of the ACL tibial guide.
Two parallel 2-mm transphyseal tunnels are made.
A suture passer is passed through each tunnel and the suture ends are retrieved.
TECH FIG 3 • Suture fixation. Two 1-0 PDS sutures are passed through the base of the anterior cruciate ligament. A suture passer is used to grab the suture ends through a transphyseal tunnel and the suture ends are tied in the anteromedial border of the tibia.
The tibial spine is reduced in its own bed and the suture ends are tied over a bone bridge in the anteromedial portion of the tibia.
The reduction is checked under direct visualization. If reduction is found to be inadequate, fixation may be augmented with percutaneous Kirschner wires or cannulated screws as needed.
Once adequate reduction had been achieved, gentle flexion and extension of the knee is performed to check for stability of reduction.
When satisfactory reduction of the fracture is obtained and documented, then the instruments are removed and the arthroscopic portals are closed.
The knee is placed in a cylinder cast in 5 to 10 degrees of flexion.
Kirschner Wire Fixation and Percutaneous Pinning
After adequate reduction of the fracture is obtained, the fracture fragment is held in reduction.
Two Kirschner wires are inserted percutaneously under fluoroscopic guidance 0.5 cm proximal to the tibial tuberosity on the medial and lateral side of the patellar tendon.
The Kirschner wires are withdrawn gradually in a retrograde manner until the tips are flush with the surface of the tibial spine (TECH FIG 4A).
Proper placement of the Kirschner wires is documented radiographically and arthroscopically.
The stability of reduction is checked with gentle passive flexion and extension of the knee.
The Kirschner wires are bent and cut at the level of the skin.
The instrumentation is removed and the arthroscopic portals are closed.
Adequate padding is applied over and beneath the pins to allow for support before cast immobilization.
A cylinder cast is applied to the knee in 5 to 10 degrees of flexion (TECH FIG 4B,C).
TECH FIG 4 • A. Arthroscopic image showing threaded Kirschner wires introduced in a retrograde fashion, maintaining reduction of the fracture fragments. Postoperative AP (B) and lateral (C) radiographs show adequate fixation and maintenance of reduction using Kirschner wires.
OPEN REDUCTION AND INTERNAL FIXATION
Exposure
The procedure begins with a standard median parapatellar approach. The skin incision may be parapatellar or midline.
The median parapatellar incision is started at the inferior pole of the patella and follows the medial border of the infrapatellar tendon down to the level of the tibial tubercle. The incision can be extended as needed (TECH FIG 5).
When performing the medial parapatellar skin incision, care should be taken to avoid inadvertent transection of the infrapatellar branch of the saphenous nerve; if a branch is cut it should be buried in fat to decrease the risk of developing a neuroma.
The skin incision is carried down to the fascia. The skin and subcutaneous tissues are retracted and reflected.
TECH FIG 5 • A. Median parapatellar approach to the knee can be done through a straight midline incision. B. The parapatellar incision is carried through to the knee joint and the patella is reflected laterally.
Dissection is carried through the medial border of the patellar retinaculum, making sure to retain at least a 2- to 3-mm cuff of soft tissue to allow for adequate closure, and down along the medial border of the patellar tendon.
The patella and patellar tendon are retracted laterally to allow for direct visualization of the ACL and tibial spine fracture.
Fracture Fixation
Once complete exposure of the knee joint is achieved, the fracture fragments as well as any concomitant injuries are identified.
The leg is held in the posterior drawer position by the assistant to allow for an easier reduction.
Fixation materials used to hold the fragment in place, including sutures, screws, and Kirschner wires, are similar to those described in the arthroscopic technique.
Once fixation of the fracture has been achieved, stability is tested by gentle flexion and extension of the knee.
Any concomitant injuries about the knee joint are addressed.
Copious washing of the knee joint is done before closure to clear the knee joint of any remaining debris.
Meticulous hemostasis and layer-by-layer closure are performed.
The knee is placed in a cylinder cast in 5 to 10 degrees of flexion.
POSTOPERATIVE CARE
Postoperatively the knee is immobilized in 5 to 10 degrees of flexion. If adequate fixation is obtained, then the extremity may be placed in full extension; hyperextension should always be avoided.
Radiographs are taken to document adequate reduction of the fracture fragment.
Early range of motion may be started at 1 to 2 weeks when the swelling has subsided and if good fixation of the fracture fragment is obtained.
In more severe cases, where stability may be in question, range-of-motion exercises are generally instituted once adequate healing of the fracture can be ascertained; this is usually 4 to 6 weeks after surgery.
OUTCOMES
Residual laxity of the knee is commonly seen, even with anatomic reduction of the fracture, and is due to the inherent stretch of the ACL before the tibial spine fails. Excellent functional outcomes have been reported despite the residual laxity with both closed management and operative treatment of tibial spine fractures, as long as reduction is maintained.2,11,19,20
Good to excellent outcomes have been reported with ORIF as well as arthroscopic reduction with suture fixation,1,5,11 arthroscopic reduction with screw fixation,9,17 and arthroscopic reduction and percutaneous pin fixation.13
Hunter and Willis7 found similar outcomes with both screw and suture fixation. In 10 cases they found interposition of the intermeniscal ligament that required retraction or resection to allow for adequate reduction.
COMPLICATIONS
Nonunion
Malunion
Arthrofibrosis4
Residual laxity
Implant-related complications
Growth disturbance
Loss of motion
REFERENCES
1. Ahn JH, Yoo JC. Clinical outcome of arthroscopic reduction and suture for displaced acute and chronic tibial spine fractures. Knee Surg Sports Traumatol Arthrosc 2005;13:116–121.
2. Baxter MP, Wiley JJ. Fractures of the tibial spine in children: an evaluation of knee stability. J Bone Joint Surg Br 1988;70B:228–230.
3. Beaty JH, Kumar A. Fractures about the knee in children. J Bone Joint Surg Am 1994;76:1870–1880.
4. Berg EE. Comminuted tibial eminence anterior cruciate ligament avulsion fractures: failure of arthroscopic treatment. Arthroscopy 1993;9:446–450.
5. Binnet MS, Gurkan I, Yilmaz C, et al. Arthroscopic fixation of intercondylar eminence fractures using a 4-portal technique. Arthroscopy 2001;17:450–460.
6. Fyfe IS, Jackson JP. Tibial intercondylar fractures in children: a review of the classification and the treatment of malunion. Injury 1981;13:165–169.
7. Hunter RE, Willis JA. Arthroscopic fixation of avulsion fractures of the tibial eminence: technique and outcome. Arthroscopy 2004;20:113–121.
8. Ishibashi Y, Tsuda E, Sasaki T, et al. Magnetic resonance imaging aids in detecting concomitant injuries in patients with tibial spine fractures. Clin Orthop Relat Res 2005;434:207–212.
9. Kocher MS, Foreman ES, Micheli LJ. Laxity and functional outcome after arthroscopic reduction and internal fixation of displaced tibial spine fractures in children. Arthroscopy 2003;19:1085–1090.
10. Kocher MS, Mandiga R, Klingele K, et al. Anterior cruciate ligament injury versus tibial spine fracture in the skeletally immature knee: a comparison of skeletal maturation and notch width index. J Pediatr Orthop 2004;24:185–188.
11. Mah JY, Adili A, Otsuka NY, et al. Follow-up study of arthroscopic reduction and fixation of type III tibial-eminence fractures. J Pediatr Orthop 1998;18:475–477.
12. McLennan JG. Lessons learned after second-look arthroscopy in type III fractures of the tibial spine. J Pediatr Orthop 1995;15:59–62.
13. McLennan JG. The role of arthroscopic surgery in the treatment of fractures of the intercondylar eminence of the tibia. J Bone Joint Surg Br 1982;64:477–480.
14. Meyers MH, McKeever FM. Fracture of the intercondylar eminence of the tibia. J Bone Joint Surg Am 1959;41A:209–222.
15. Meyers MH, McKeever FM. Fracture of the intercondylar eminence of the tibia. J Bone Joint Surg Am 1970;52A:1677–1684.
16. Noyes FR, DeLucas JL, Torvik PJ. Biomechanics of anterior cruciate ligament failure: an analysis of strain-rate sensitivity and mechanisms of failure in primates. J Bone Joint Surg Am 1974;56:236–253.
17. Reynders P, Reynders K, Broos P. Pediatric and adolescent tibial eminence fractures: arthroscopic cannulated screw fixation. J Trauma 2002;53:49–54.
18. Skak SV, Jensen TT, Poulsen TD, et al. Epidemiology of knee injuries in children. Acta Orthop Scand 1987;58:78–81.
19. Wiley JJ, Baxter MP. Tibial spine fractures in children. Clin Orthop Relat Res 1990;255:54–60.
20. Willis RB, Blokker C, Stoll TM, et al. Long-term follow-up of anterior tibial eminence fractures. J Pediatr Orthop 1993;13:361–364.
21. Woo SL, Hollis JM, Adams DJ, et al. Tensile properties of the human femur-anterior cruciate ligament–tibia complex: the effects of specimen age and orientation. Am J Sports Med 1991;19:217–225.
22. Zaricznyj B. Avulsion fracture of the tibial eminence treated by open reduction and pinning. J Bone Joint Surg Am 1997;59A:1111–1114.