The Role of Primary Repair in Pediatric Anterior Cruciate Ligament Injuries

Fig. 22.1

This schematic drawing of the knee with the ACL shows the different ACL tear locations. The green zones indicate the location of tears on MRI that have a high chance of repairable tears, orange zones indicate a medium chance for repairable tears, and the red zone indicates a low chance of a tear that is repairable. Using these tear locations, a preoperative assessment can be made for the eligibility of primary repair of the ligament

MRI can be effectively used to make a preoperative assessment of the tear types, although the final decision for eligibility of repair is made during arthroscopy. We have recently performed a MRI study in which we assessed the distribution of the different tear types using this classification system and found substantial interobserver and substantial to nearly perfect intra-observer reliability [47]. In approximately 350 MRIs of adult patients with acute ACL tears, we have found that 16% had type I tears, 23% had type II tears, and only 2% had distal type V bony or soft tissue tears. In our unpublished data on pediatric patients, we have noted that femoral bony avulsion tear types are very rare, as we have not encountered this tear type in over 250 pediatric MRIs. Furthermore, it was noted that nearly all acute ACL tears were distal bony avulsion in pediatric patients of ≤10 years of age. In children aged 11–14, we noted that approximately 20% had type I avulsion tears and 20% had type V bony avulsions, while in patients aged 15–17, the pattern of tear type distribution was similar to adults [47]. Although these numbers may provide a rough estimation for the eligibility of a patient for primary repair, the final decision is still made during arthroscopy when the ligament is directly assessed. In adults, for example, it was noted that 90% of the type I tears on MRI were indeed eligible for repair (green zone, Fig. 22.1), whereas this was only 50% for type II tears (orange zone, Fig. 22.1) and 14% for type III tears (red zone, Fig. 22.1). It should therefore be emphasized that MRI can be used to make a preoperative assessment but that the final decision is made during arthroscopy. The most important criteria for eligibility for primary repair are (I) that sufficient tissue length is present to tension the remnant to the femoral or distal insertion and (II) sufficient tissue quality to hold stitches is present.

Timing

Traditionally, primary repair was performed in the acute setting, as ligament retraction and absorption were reported to already occur after only a few weeks [17, 18]. As a result, several studies used strict time criteria, such as performing surgery within the first week [27]. However, when reviewing the recent case series on arthroscopic primary repair in pediatric patients, it can be noted that the days from injury to surgery ranged from 7 days to 123 days [4, 12]. Generally, surgery should not be performed in the first week after injury if the soft tissue swelling and inflammatory response in the knee are severe. With regard to delay, it is our belief that the tissue length and tissue quality are more important than the days of delay. The senior author has performed arthroscopic primary repair in patients that had a delay between injury and surgery of 4–11 years after injury [48], because these patients had sufficient tissue length and tissue quality. In cases such as these, it is most often in the case that the ACL has reattached to the PCL there by maintaining the tissue quality. Generally, however, the surgery is performed between 1 week and 3 months, as this has a lower risk for arthrofibrosis, while sufficient tissue length and quality are still present.

Advantages in the Pediatric Population

There are several advantages of primary repair for pediatric patients. Conservative treatment is sometimes performed in this population, but there is a high risk of meniscal and cartilage damage with conservative treatment [49, 50]. Primary repair is a minimally invasive surgery in which no tunnels (when using suture anchors) or only small tunnels (when tying over button) need to be drilled, no grafts harvested, and the procedure is relatively quick. Furthermore, the native tissue is preserved and the proprioception is maintained [51, 52]. As a result, in our practice, patients generally only need to use pain medication for 1 or 2 days, return to work or school within a week, return to full range of motion and can walk without a limp within 10 days to 2 weeks, and have a much quicker return to sports. In patients with previous contralateral ACL reconstruction, they describe that the repaired knee feels more normal and that the pain experienced and difficulty of recovery are significantly less, and they say that the knee feels better when compared to the other side. Finally, because high failure rates with ACL reconstruction are seen in pediatric patients [7, 8], surgeons should consider the impact of revision surgery [53]. Following failed primary repair, revision surgery is similar to a primary ACL reconstruction, as no or only small tunnels have been drilled and no graft has been harvested. Following failed ACL reconstruction, however, tunnels have been drilled, and there may be problems with widening of the tunnels, malpositioning of hardware, and harvesting of more graft tissue [54–56]. As a result, the outcomes of revision reconstruction surgery have been inferior to primary reconstruction [57–59].

Experimental Studies

Over the last decade, the research group of Murray has performed many experimental studies on primary repair, and some of these studies focused on the skeletally immature [60–63]. In these studies, they performed primary repair in which they used a biological scaffold around the repair that should protect the healing clot against the joint fluid. Murray et al. first assessed the role of skeletal maturity on ACL healing in Yucatan minipigs and found that a better healing response and better restoration of kinematics were seen in skeletally immature minipigs when compared to skeletally mature minipigs [60]. Furthermore, other studies from this group also showed that more growth factors, larger number of capillaries, and more fibroblast activity in the ACL were present in the skeletally immature pigs when compared to the mature pigs [61–63]. Interestingly, in another study with Yucatan minipigs, they found that following primary repair less posttraumatic osteoarthritis occurred when compared to ACL reconstruction [64]. This is especially of interest for pediatric patients, as ACL reconstruction changes the contact pressures in the knee [10, 65] resulting in high incidence of osteoarthritis (up to 78% after 14 years) [11, 66], which could be problematic for these young patients.

Femoral Bony Avulsions

Outcomes in Literature

Femoral bony avulsions are very uncommon in the pediatric and adult population [67]. In our MRI study in which we assessed the incidence of different tear types [47], we noted that no femoral bony avulsion tears occurred in 353 adult patients and in over 250 pediatric patients. In the literature, only a handful of case reports on femoral bony avulsions have been reported. Most of these tears had osteochondral avulsions [68–71], whereas a few cases had cartilaginous avulsions [72, 73]. These cases have been treated with transosseous repair , but the follow-up is generally short [68, 71, 74, 75]. Systematic reviews or multicenter studies are necessary to assess outcomes of these injuries. The surgical technique with transosseous repair will be explained in the next section of proximal soft tissue avulsions.

Proximal Soft Tissue Avulsion Tears

Surgical Technique

We will discuss the surgical technique here briefly as it has been more extensively described in the recent literature [44, 48, 76]. It should be noted that in most of these patients, an internal bracing of #2 FiberTape is added to these patients in order to protect the ligament, as we have learned from the reconstruction literature that these patients are a high-risk population [7, 8]. We describe the surgical technique with the case of a 14-year-old girl.

A 14-year-old skeletally immature girl came in the clinic, as she suffered a twisting injury during a cheerleading contest 2 months ago. MRI revealed a subacute complete proximal tear that appeared to be attached to the PCL (Fig. 22.2). Physical examination revealed full ROM and a grade 2B Lachman and 2+ pivot shift in an otherwise stable knee. She was taken to the operating room, and it was agreed that primary repair would be performed in case of sufficient tissue length and quality, and otherwise an augmented repair [43, 44] or reconstruction would be performed.

Fig. 22.2

MRI images of a left knee of a 14-year-old girl. (a) Sagittal T1-weighted image shows a complete ACL tear with only a few proximal fibers on the femoral wall (arrowhead) and distal fibers reattached to the PCL (arrow). (b) Sagittal T2-weighted image shows a proximal type I tear with indeed almost no fibers on the femoral wall (arrowhead) and a proximal tear with sufficient tissue length (arrow)

During arthroscopy, it was noted that the ACL was indeed reattached to the PCL and an empty wall sign was present (Fig. 22.3). First the ACL was freed from the PCL. Starting distally, the anteromedial bundle was then sutured in an alternating, interlocking Bunnell-type pattern using a Scorpion suture passer (Arthrex, Naples, FL) with #2 FiberWire suture (Arthrex, Naples, FL). Approximately 3–4 stitches were made before the final pass exited at the avulsed end of the ligament toward the femur (Fig. 22.4a). Then, a similar process was performed for the posterolateral bundle using #2 TigerWire suture (Arthrex, Naples, FL) (Fig. 22.4b).

Fig. 22.3

Arthroscopic view of the left knee of the same 14-year-old girl. (a) The ACL (arrowhead) is reattached to the PCL and the femoral footprint is empty (arrow). There seems to be sufficient tissue quality, characterized by the fibers running in the same direction in intact fashion. (b) A more proximal view of the ACL shows again an empty femoral footprint (arrowhead) and ACL reattachment to the PCL

Fig. 22.4

Arthroscopic view of the left knee of the same 14-year-old girl. (a) #2 FiberWire sutures are passed through the anteromedial bundle (black arrowhead), and the footprint is further visualized (white arrowhead). (b) #2 TigerWire sutures are passed through the posteromedial bundle (black arrowhead), with again the empty footprint visualized (arrow). (c) A suture anchor with the posterolateral bundle stitches (asterisk) is deployed in the posterolateral origin of the femoral footprint. Note the relatively low position of the posterolateral suture anchor. The sutures of the anteromedial bundle are visualized (arrowhead). (d) A suture anchor with the anteromedial bundle sutures (black arrowhead) is deployed in the anteromedial origin of the femoral footprint (white arrowhead). The already inserted posterolateral bundle can be seen (asterisk). The internal brace can be visualized (black arrows). (e) After the repair is complete (black arrowhead), the internal brace (asterisk) needs to be channeled down. A nitinol wire (white arrowhead) is passed through the tibia to retrieve the internal brace. (f) The primary repair with internal bracing is complete. The internal brace is now tensioned and disappears in the distal part of the ACL (arrowhead)

At this point, the sutured ligament can either be repaired with suture anchor fixation, which is the preference of the senior author due to the aperture fixation and minimal morbidity, or with transosseous fixation, which can also be performed for the aforementioned femoral bony avulsions.

In this case, suture anchor fixation was chosen, and although fluoroscopy was not used because the physes were mostly closed, it can easily be used to ensure safe placement of the anchors. Initially, an accessory inferomedial portal is made to facilitate access to the ACL femoral footprint. Through this portal a hole was tapped in the posterolateral origin of the femoral footprint with the knee flexed to about 115°. Using a 4.75 mm Vented BioComposite SwiveLock suture anchor (Arthrex, Naples, FL), the sutures were then deployed in the femoral wall, while the repaired ligament was tensioned to the wall (Fig. 22.4c). The same process was then repeated for the anteromedial bundle with two differences being that the knee is flexed to 90° and that the anteromedial suture anchor was preloaded with TigerTape (Arthrex, Naples, FL) (Fig. 22.4d). After the repair was complete (Fig. 22.4e), the internal brace was fixed distally. A pin was drilled up from the anteromedial cortex of the tibia to the anteromedial footprint. This was then switched for a straight Micro SutureLasso (Arthrex, Naples, FL) (Fig. 22.4e), and its nitinol wire was used to pass the TigerTape along the ACL substance anteriorly and down through the tibia where it was fixed with another suture anchor with the leg held near full extension after cycling the knee. The suture anchor ACL primary repair with internal brace was then completed (Fig. 22.4f).

If transosseous fixation is chosen, antegrade or retrograde parallel drill holes are made at the origin of the anteromedial and posterolateral bundles. A separate lateral incision is necessary to facilitate drilling and retrieval of the sutures out the lateral cortex of the femur. Suture passage can be accomplished either antegrade or retrograde according to surgeon preference. If the femoral physis is still open, then fluoroscopy can be helpful to stay in the epiphysis with the drill holes. Once the sutures are retrieved laterally, then they can be tensioned and tied over a ligament button.

The girl recovered quickly, which is typically seen with proximal repairs, and had ROM of 0– 110° after 3 days and full ROM within 2 weeks. She used pain medication for a few days, and her leg felt “pretty normal” after 2 weeks. Lachman examination was negative with good endpoint, and pivot shift was negative and remained so throughout her course. She returned to basic maneuvers with the cheer team after 3 months and joined competitive cheerleading at national competition after 4 months using a brace. At 9-month follow-up, the knee was completely stable and had been competing on a national level for 5 months, and the patient and her parents were satisfied with the procedure.

Outcomes in Literature

In 2010, Frosch et al. performed a systematic review on the outcomes of open primary repair in pediatric patients and found a rerupture rate of 2.9% (2/69) and no growth disturbances (0/69) [9]. Most of these studies indeed treated proximal tears but were historical studies using an open approach [9]. Over the last 2 years, three studies reported the outcomes of primary repair of proximal tears [4, 12, 13], of which one study reported long-term outcomes of an open technique [13]. Smith et al. were the first to report on arthroscopic primary repair of proximal tears in pediatric patients with additional internal bracing [4]. They reported excellent outcomes in two patients aged 5 and 7 at clinical follow-up, and the ACL appeared healed with re-arthroscopy at 3 months, when they removed the internal brace. Bigoni et al. recently reported the first case series on five patients treated with arthroscopic primary repair of type I tears [12]. They found excellent outcomes at 3.6-year follow-up with a mean Lysholm score of 93.6 and a negative Lachman test in four patients and 1+ Lachman test in the fifth patient. Both of these studies used transosseous fixation for their patients. In very young patients, it may be preferable to use transosseous fixation, as with anchor fixation the suture anchors can endanger the growth plate due to the small epiphysis.

Distal Soft Tissue Avulsion Tears

Surgical Technique

Distal soft tissue avulsion tears are relatively uncommon in children, but distal bony avulsions are frequently seen in patients younger than 12 years [45]. Open or arthroscopic reduction with internal fixation (ORIF or ARIF) of these fractures remains outside the scope of this chapter and is discussed in another chapter in this book. Comminuted type IV McKeever tibial spine fractures or distal soft tissue avulsion tears cannot be fixed with these techniques, but they can be treated with primary repair. With this technique, the principles are similar to proximal tears, but then in an inverted manner. We describe the technique with the case of a 14-year-old boy.

He came in the clinic with a twisting injury 2 weeks prior during a lacrosse game. Physical examination revealed full ROM, grade 2B Lachman, and 2+ pivot shift. The MRI revealed a type V distal soft tissue avulsion tear (Fig. 22.5), and the patient was taken to the operating room 6 weeks after the injury.

Fig. 22.5

MRI images of the left knee in a 14-year-old boy. (a) Sagittal T1-weighted image shows a complete ACL tear around the distal insertion (arrowhead) with an intact proximal remnant with excellent tissue quality (arrow). (b) Sagittal T2-weighted image also shows a distal ACL tear (arrowhead) with a few fibers attached to the tibia and an intact proximal remnant with excellent tissue quality (arrow)

During arthroscopy, the distal avulsion was confirmed (Fig. 22.6). First, the distal avulsed ligament and tibial footprint were roughened as the tear was already 6 weeks old. Then, #2 TigerWire sutures were passed in the anteromedial bundle from proximal to distal, and the same technique was repeated for the posterolateral bundle using #2 FiberWire sutures (Fig. 22.7a and 22.6b). Both sutures were then exited at the distal end at the locations of the anteromedial and posterolateral footprint locations (Fig. 22.7b). Then, using a cannulated drill, two small tunnels were drilled transphyseally from the anteromedial tibial cortex to the anatomic footprints of the anteromedial and posterolateral bundles. In this case, fluoroscopy was not used, but it can be used to guide the drilling. Both sutures were then exited through the drilled tunnels (Fig. 22.7c) and were tied distally over a button after the knee was cycled. The distal repair was then complete (Fig. 22.7d).

Fig. 22.6

Arthroscopic view of the left knee of the same 14-year-old boy. (a) The ACL is torn distally (arrow) with intact anteromedial (AM) and posterolateral bundles continuing proximally. (b) The ACL can be lifted proximally off the tibial footprint (arrowhead) and fixation is needed. Note that this is a soft tissue avulsion (arrow)

Fig. 22.7

Arthroscopic view of the left knee of the same 14-year-old boy. (a) #2 TigerWire sutures are passed through the anteromedial bundle using a suture passer (arrowhead) starting distally (arrow). (b) The last pass of the anteromedial bundle suture is exited at the avulsed site of the ligament using the suture passer (arrow). (c) After drill holes are made in the anteromedial and posterolateral origins of the tibial footprint, the anteromedial #2 TigerWire suture (white arrow) and the posterolateral #2 FiberWire suture (black arrow) are channeled through the tibia. The white arrowhead indicates the sutures advancing through the proximal part of the posterolateral bundle. (d) The distal repair is complete

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