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October 16, 2019
6 min read
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15-year-old boy with history of knee pain

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A 15-year-old boy with no significant past medical history arrives to clinic for evaluation of left knee pain and swelling after sustaining a non-contact injury 2 days earlier while playing baseball. The patient states he was running from third base to home and felt a sudden sharp pain and a pop in his left knee when his foot struck the plate. He reports that his knee became significantly swollen the night of the injury. He has been able to bear weight for the last 2 days. When asked to localize his pain, he points to the anteromedial and anterolateral aspects of the left knee. The pain has subsided in the last day; however, he still has some discomfort and rates his pain as a two out of 10. The patient describes having a subjective feeling of instability. He denies a history of other injuries or surgeries to the left knee. Review of systems was negative aside from that stated above.

On exam, there is tenderness to palpation of the anterolateral aspect of the left knee. There is a moderate joint effusion with decreased range of motion of the knee compared to the right knee. The knee is stable to varus and valgus stress. A Lachman exam demonstrates 7 mm of anterior tibial translation with no firm endpoint, which is consistent with a 2b exam. McMurray test is negative, although there is some discomfort with the exam. The remainder of the patient’s exam is otherwise unremarkable.

Anterior-posterior (AP) and lateral radiographs taken in the clinic show the left knee (Figure 1). Representative images from MRI of the knee include coronal and sagittal cuts (Figure 2).

Treatment options are cast at full extension, cast in 30° flexion, arthroscopic fixation of the fragment or open fixation of the fragment.

How should this patient be managed?
See answer on the next page.

Figure 1. Preoperative lateral (a) and AP (b) radiographs of the left knee of a skeletally immature individual demonstrate a free fragment of bone in the anterior aspect of the femoral notch.
Figure 2. Preoperative MRI of the left knee shows a sagittal cut (a) and a coronal cut (b) that illustrate avulsion of the tibial attachment of the ACL with attached subchondral bone.

Source: Ralph E. Moore III, MD

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Anterior tibial spine avulsion injury

The history, examination and imaging are consistent with an anterior tibial spine avulsion fracture located at the tibial eminence that is part of the bony attachment of the ACL. Therefore, we proceeded with arthroscopic fixation of the fragment.

Operative treatment

After the risk and benefits of operative intervention were discussed with the patient and his parents, they elected for surgical treatment. An arthroscopic diagnostic examination of the knee was performed with standard lateral and medial parapatellar portals. A large bony avulsion of the ACL at the tibial footprint was encountered and was reducible to its native anatomic position. The fragment had an intact femoral attachment and sufficient bone stock to accommodate repair. Two #2 FiberWire sutures (Arthrex) were passed through the base of the ACL in a luggage tag configuration and then passed through the bony fragment from superior to inferior to prepare for anatomic reduction via transosseous tibial tunnels. Two separate transphyseal tibial tunnels were drilled using a tibial guide and 2.4-mm guide pin. The sutures were passed through the tibial tunnels and exited out an anteromedial incision. The knee was placed in 30° flexion. The two sutures were tensioned and tied over the anterior tibial bone bridge. Anatomic reduction of the tibial bony fragment in the tibial sulcus was confirmed under arthroscopic visualization.

Postoperatively, the patient was made weight-bearing as tolerated in a hinged knee brace locked in extension for 6 weeks.

Discussion

Tibial spine avulsions are fractures seen in skeletally immature patients who are typically aged 8 to 14 years. In this age group, the intercondylar eminence is not completely ossified making the cancellous bone more prone to failure than the ligamentous ACL. Classically, tibial spine injuries have been associated with hyperextension injuries of the knee. However, more recently they have been associated with non-contact rotational injuries, such as with traditional ligamentous ACL injuries.

The most commonly used classification of tibial spine fractures was developed by Meyers and McKeever and provides treatment guidance based on the degree of displacement. Type 1 fractures are nondisplaced. Type 2 fractures have superior displacement of the anterior aspect of the fragment with an intact posterior hinge.

Type 1 fractures are treated nonoperatively in a long leg cast at 0° to 20° flexion. They require follow-up to ensure the fragment does not displace. Type 2 fracture treatment remains controversial concerning any attempt to manage them with closed reduction or surgically. The closed reduction technique has been described as intra-articular aspiration of hematoma, injection of local anesthetic for pain control and reduction by bringing the knee into full extension. Theoretically, extension reduces tension on the anteromedial ACL bundle, providing an opportunity for anatomic reduction. If acceptable reduction is obtained, the leg is cast in that position.

Some argue that a successful reduction is rare. Therefore, type 2 fractures should always be operatively treated. Failed closed management occurs because reduction may be blocked by entrapment of the anterior horn of the medial meniscus or inter-meniscal ligament. A non-anatomic reduction may not be recognized on standard radiographs. Type 3 fractures are completely displaced from the tibia. Type 3 fractures are treated with surgery.

Figure 3. Shown is an intraoperative image of the in situ tibial spine avulsion fragment after hematoma evacuation as seen from the medial parapatellar portal (a). Reduction of this fragment with the arthroscopic shaver is demonstrated (b). Luggage tag capture of the base of the ligamentous ACL with FiberWire suture is illustrated (c). Passage of the free ends of the suture through the subchondral avulsion fragment is demonstrated (d). The exit point of the lateral transtibial drill tunnel where the lateral suture will be shuttled is shown (e). The final repaired suture construct of the tibial spine avulsion is shown from the lateral parapatellar portal (f).
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Historically, operative fixation involved an open procedure. Arthroscopic fixation is the now gold standard of treatment. Studies have shown improved outcomes of arthroscopic intervention compared to traditional open procedures. Another reason arthroscopic intervention is now preferred is it allows improved visualization of other intra-articular injuries and management of associated soft-tissue injuries.

Arthroscopic fixation is obtained with a screw or traFnsosseous suture configuration. Fixation depends on the fragment and the surgeon. There are no randomized controlled trials comparing these methods. Screw fixation typically involves cannulated, partially threaded screws which ideally do not cross the physis, although transphyseal screws may be required for adequate purchase. Complications of screw fixation include anterior impingement, damage to the articular surface and possible further fragmentation of a comminuted fracture. Therefore, screws are often removed once the fracture is healed, particularly if they are transphyseal. Other considerations are to use a headless variable-compression screw to avoid impingement complications. As for suture fixation, suture is passed through the base of the ACL and shuttled through tibial tunnels for anatomic trans-osseous fixation. This technique does not require a second surgery for hardware removal and can achieve a more desirable reduction in comminuted fractures.

Selection of screw vs. suture fixation is largely surgeon- and fracture-dependent. Clinical studies have failed to show difference between the two methods. Furthermore, there has not been any difference noted in strength of suture vs. screw fixation.

Recent literature raises concerns for intrinsic ACL damage with tibial spine avulsions that can lead to residual ACL laxity and predispose patients to delayed rupture or subjective instability. This argument alludes to stretching and plastic deformation of the native ligamentous ACL at the time of injury leading to residual laxity despite anatomic fixation and healing. The incidence of patients with a history of tibial spine avulsions undergoing delayed ACL reconstruction for re-rupture or instability has been cited at 19%, which is double the quoted failure rate after ACL reconstruction (9%). Despite these failures, considerations need to be made in this unique adolescent population regarding risk of physeal damage and relative ease of revision in the setting of a failed ACL repair as compared to failed reconstruction. Our recommendation for tibial spine avulsion fractures is for nonoperative management of type 1 injuries, closed reduction attempt with low threshold for arthroscopic intervention with type 2 injuries, and arthroscopic fixation with screw or suture fixation in type 3 injuries.

Disclosures: Moore, Teske and Trammell report no relevant financial disclosures.