A “Suture Staple” Knotless Anchor Technique for Fixation of Tibial Tubercle Avulsion Fractures in Pediatric Patients

Abstract

Tibial tubercle fractures are rare injuries most commonly seen in the pediatric population; more specifically the adolescent male population towards the end of peak longitudinal growth. Typically, tibial tubercle fractures are fixed with cannulated screws. However, there is a subsection of patients with tibial tubercle avulsion fractures in which the fracture fragment is small and attempts at screw fixation may lead to screw cut‐out and fragment damage. To address this, we describe a technique for small or thin tibial tubercle fractures using a tensionable knotless anchor construct with 2‐4 independent mattress sutures placed in a staple configuration. This method employs the biomechanical strength of knotless fixation while eliminating the potential single point of failure and hardware prominence seen with screws and knotted anchors.

Tibial tubercle fractures are rare injuries accounting for approximately 1% of physeal injuries with 0.4%‐2.7% being avulsion fractures. ¹ , ² , ³ , ⁴ These fractures occur most commonly in the adolescent population because of the structural changes that occur as the proximal tibial physis is closing. ⁴ Tibial tubercle fractures occur in patients aged 11 to 18 and are associated with sport activity. ⁵ , ⁶ Fractures occur due to eccentric contraction of the quadriceps with the knee in the flexed position such as during jumping. ⁷ , ⁸ Most often, cannulated screws are utilized for fixation of these fractures; however, use of Kirschner wires, tension bands, and staples have all been described. ⁶

Suture anchor fixation has been described for patellar sleeve avulsion fractures in which small fragments and comminution precluded typical fixation strategies. ⁹ Lee et al. described suture bridge fixation of a tibial tubercle avulsion fracture in an adult patient. ¹⁰ The knotless “suture staple” technique has primarily been used to repair damaged tendons, negating the need for knot tying, which can lead to soft tissue or cartilage damage, as well as the need for a second surgery for hardware removal. ¹¹

The senior author has seen 6 patients over the course of the past 2 years in which the fracture fragment was so small or thin, attempts at screw fixation would result in screw cut‐out or further fragmentation of the fracture fragment. Here, we describe a knotless suture staple technique that was utilized in these patients who had tibial tubercle avulsion fractures that were not amenable to screw fixation. All patients were between 12 and 15 years of age with injuries occurring during football, basketball, or running.

SURGICAL TECHNIQUE

Preoperative Evaluation

All patients presented following an acute injury. Commonly this included feeling a “pop” in their knee with sudden onset of pain while running or jumping. Physical examination revealed localized swelling to the anterior knee with some patients having associated joint effusion. Patients were unable to perform a straight leg raise and were very hesitant to attempt knee range of motion.

Radiographs showed small avulsion of distal aspect of tibial tubercle with proximal migration of fracture fragment. This was sometimes associated with patella alta (Figure 1). In some cases when radiographs were inconclusive a magnetic resonance imaging (MRI) was obtained for further evaluation. MRI further evaluated integrity of patellar tendon as well as providing cross sectional imaging of tibia to better evaluate fracture fragment size (Figure 2).

FIGURE 1.

This is a lateral radiograph of the right knee taken on initial presentation. The white arrow is pointing to the tibial tubercle fracture fragment which has migrated proximally. Also shown is patella alta. When this is seen, we suspect the patellar tendon is attached to this proximally migrated piece causing compromise of the patellar tendon.

FIGURE 2.

(A) Lateral radiograph of right knee showing small fracture fragment at distal aspect of tibial tubercle. (B) Sagittal T1 MRI image showing displaced tibial tubercle avulsion fracture with patellar tendon intact, attached to fracture fragment. (MRI, magnetic resonance imaging.)

Technique

The patient is placed in the supine position on the operating room table. Following induction of anesthesia, standard preoperative antibiotics are administered. A well‐padded tourniquet is placed on the operative thigh and the operative leg is prepped and draped in the usual sterile fashion. The patient's operative leg is placed on a BoneFoam ramp leg elevator. The tibial tubercle is marked and a roughly 5 cm incision over the patellar tendon is demarcated (Video 1).

VIDEO 1.

Download video file ^{(79.9MB, mp4)}

This surgical technique video describes a “Suture Staple” knotless anchor construct for fixation of tibial tubercle avulsion fractures in pediatric patients. It reviews preoperative imaging and indications for technique. Intraoperative video and images show approach, fixation, and closure. Finally, postoperative radiographs are included that show healing tibial tubercle fracture at 6 weeks. Video content can be viewed at https://doi.org/10.1002/atn2.70169.

A midline incision is made over the patellar tendon. The dissection is carried through the soft tissue, including the superficial patellar tendon until the fracture is visible. Hematoma in the fracture site is cleared from fracture site using a freer, rongeur, curette, and irrigation while preserving viable periosteum and peritenon (Figure 3). Two to four‐2.6 mm knotless FiberTak anchors (Arthrex, Naples, FL) are placed in the bony bed (Figure 4). A Kirschner wire is used to drill 2 to 4 small holes into the fragment and the sutures from the suture tack are shuttled through (Figure 5). The suture tacks are then sequentially tightened down by pulling the sutures which allow the sliding mechanism and the loop to create compression, slowly reducing the fragment into its anatomic location (Figure 6). Clinical pearls and pitfalls are provided in Table 1.

FIGURE 3.

With patient positioned in the supine position, operative extremity (in this case, right lower extremity) is prepped and draped. A midline incision is made over the tibial tubercle. Dissection is carried down through superficial tissues until tibial tubercle avulsion fracture fragment is visualized. This image shows the approach to visualize the fracture.

FIGURE 4.

The fracture bed and fracture fragment are then cleaned and prepared for fixation. Fracture fragment, highlighted by the black arrow, is pulled out of the way using an Alice clamp, as shown here. Suture anchors, highlighted by the white arrow, are placed into the fracture bed.

FIGURE 5.

In this image, sutures have been passed through the fracture fragment. The fixation suture strands are being crossed into the contralateral shuttle sutures to reduce and secure the fracture fragment.

FIGURE 6.

The fracture is slowly reduced and secured into final position by tightening sutures.

TABLE 1.

Surgical Technique Pearls and Pitfalls

Pearls	Pitfalls
Fully debride the base of the tibial tubercle fracture to ensure no interposed tissue	Failure to adequately prepare the donor site or the fragment may prevent proper reduction and eventual fragment healing
Confirm that the fracture fragment can be easily reduced to its bed anatomically before placing suture anchors	Not confirming that the fragment can be reduced to its bed before fixation can lead to nonunion or malunion
Place the suture anchors into cortical bone just outside of the fracture bed	Placing the suture anchors into the cancellous fracture bed can lead to anchor pullout
Shuttle all sutures through the fracture fragment and patellar tendon	Shuttling only the fixation suture (blue) through the fracture fragment/patellar tendon can lead to a jam in the knotless mechanism
Sequentially tighten all sutures to form the staple construct with the fragment reduced, taking out all slack before final tightening	Only tightening one of the limbs fully before the others can lead to anchor pullout or fragment malreduction

Appropriate positioning is confirmed using direct visualization and fluoroscopy (Figures 7 and 8). The wound is then irrigated and viable peritenon is repaired using 0 Vicryl. 2‐0 Vicryl and 4‐0 Monocryl are then used to close the skin. The incision is dressed with Steri‐Strips, gauze, Kerlix, ice cuff, and Ace wrap, and the patient is placed into a range of motion knee brace locked in extension.

FIGURE 7.

This image shows the final fixation construct with suture staple prior to wound closure.

FIGURE 8.

Intraoperative fluoroscopy image showing satisfactory reduction of fracture fragment.

Postoperative Protocol

Immediately postoperatively, patients receive cold therapy and are instructed to keep the range of motion knee brace on at all times. Patients are seen for first follow up in the clinic 2‐5 days postoperative for wound check. At this visit, patients are allowed to begin touchdown weight bearing with crutches for 4 weeks. The knee brace is modified to allow range of motion from 0 to 30° for 2 weeks, followed by 0 to 60° for 2 weeks, and finally, 0 to 90° for 2 weeks for a total of 6 weeks of limited range of motion. Physical therapy begins at 1‐week postoperative with the use of blood flow restriction if available. No active quadriceps exercises are allowed until 4 to 6 weeks after surgery, when interval bony healing of the fracture has been shown (Figure 9).

FIGURE 9.

Lateral radiograph of right knee at 6 week postoperative visit showing bony healing and integration.

DISCUSSION

Tibial tubercle avulsion fractures are uncommon; however, when they do occur, surgical treatment is often necessary to restore function to the extensor mechanism. Tibial tubercle fractures were originally described by Watson‐ Jones, and this classification was modified by Ogden to the classification system most commonly used today. ¹² , ¹³ Fracture fixation with screws is often the treatment of choice when the fracture fragment is large enough. However, as we have seen, there is a subset of patients in which the fracture fragment is too small and attempts at screw fixation would be unsuccessful. It is this subset of patients that we believe would benefit from our described technique. A full list of advantages and disadvantages are provided in Table 2.

TABLE 2.

Advantages and Disadvantages

Advantages	Disadvantages
No prominent hardware	Lower pull‐out strength vs screw fixation (but screws would destroy these small fracture fragments)
Load sharing between anchors	Anchors need to be placed in cortical bone because easier to pull out of cancellous bone (bony bed of tubercle fracture)
Multiple limbs of suture staple construct spread the compressive force across the fracture fragment/patellar tendon

Suture anchors have been used for a variety of soft tissues including tendon and labral repairs. The development of knotless suture anchors has allowed for the expansion of their use with elimination of the side effects caused by suture knots without impact on biomechanical strength. Lacheta et al. compared knotless all‐suture anchors with knotted all‐suture anchors and found similar biomechanical strength for first failure load, ultimate load, and stiffness. ¹⁴ Hartigan et al. described two techniques for abductor tendon repair using knotless suture staple repair. By eliminating the suture knots, postoperative trochanteric pain is reduced. ¹⁵ The suture staple technique described here is based on the technique described by Ratner et al. in which they used suture staples to perform capsulotenodesis for anterior shoulder instability. ¹⁶ Expanding the use of suture fixation, Samitier et al. explored a one‐stage osteochondral repair technique using knotless anchors and crossing suture sliding loops and found it to be suitable for different anatomic locations such as the patella, condyle, or trochlea. ¹¹ Lee et al. described using a suture bridge technique in an adult patient with poor bone quality who sustained tibial tuberosity avulsion fracture. ¹⁰

Our technique allows for appropriate reduction and fixation of tibial tubercle avulsion fractures when the fracture fragment is too small to allow for screw fixation. This can also be used in combination with screw fixation in the setting of a comminuted fracture with a large fracture fragment as well as smaller fracture fragments. The authors have used both single and double suture staples depending on fracture characteristics. The use of knotless suture anchors eliminates the complications associated with prominent suture knots or screw heads. Because of the superficial location of the tibial tuberosity, prominent suture knots and screws heads often cause irritation, and therefore, patients may request that they be removed which requires an additional surgery.

There are limitations to the use of this technique. This technique may be best suited in the pediatric population in which the suture staple provides temporary stabilization which allows the fracture to heal. This may not be feasible in the adult population. Further biomechanical testing of this technique is required to better understand the strength of the repair.