Several series have shown that transphyseal ACL reconstruction using soft tissue grafts, usually hamstring autograft, in postpubescent adolescents is safe with no angular deformities or leg length discrepancies and excellent outcomes [14–16]. However, there is concern that transtibial drilling techniques may produce a vertical graft orientation and place less of the graft in the central aspect of the femoral footprint than accessory medial portal drilling techniques [17].

Independent femoral tunnel drilling can be done with either accessory medial portal drilling, 2 incision outside-in drilling, or outside-in drilling using a retrograde drilling technique [17, 18]. Unfortunately, these techniques, when used in the typical adult manner, will produce a very oblique tunnel through the lateral physis of the distal femur that potentially damages a larger portion of the physis and also potentially the perichondral ring. However, the retrograde inside-out drilling can also be done safely with proper intraoperative imaging guidance to avoid the physis (Fig. 15.3).

Transphyseal tibial drilling is thought to be safer than trans-femoral physeal drilling in these skeletally immature patients for several reasons. First, the tunnel is more central and can be modified to be more vertical. Placing the tunnel more vertical in the tibia allows the tunnel to be more central in the tibial physis and to be more circular and therefore create a smaller hole in the physis. In addition, the tibial proximal physis produces less longitudinal growth than the distal femoral physis and therefore is less risky for producing a leg length discrepancy. By drilling through the physis, more graft is able to be placed on the tibia side and this allows for the potential for more ingrowth and also for a variety of distal fixation techniques. It is the authors’ opinion that this technique is also less technically demanding than an all-inside reconstruction technique especially for surgeons who are familiar with traditional drilling techniques.

Hybrid reconstruction has been described previously in the literature with good results although the previous hybrid technique involved an “over-the-top” femoral position of the graft. The “over-the-top” femoral position allows the femoral physis to be completely avoided but does place the graft in a nonanatomic position. Lipscomb and Anderson reported on 24 skeletally immature patients with a mean age of 13 that underwent a hybrid ACL reconstruction using hamstring autograft, “over-the-top” femoral position and a transphyseal tibial tunnel [19]. Eighty-three percent of patients returned to preoperative activity levels and one patient had a leg length discrepancy of 2 cm with a mean follow-up of 35 months. Andrews et al. studied eight adolescent patients (mean age of 13.5) who had undergone hybrid reconstruction with fascia lata or Achilles allograft with an “over-the-top” femoral fixation and had 87.5% good to excellent results with no growth disturbances at mean follow-up of 58 months [20]. Lo et al. reported on five patients (mean age 12.9 years) using a hybrid reconstruction technique with an over-the-top femoral placement of a soft tissue autograft and transtibial drilling [21]. They utilized 6 mm or smaller tunnels on the tibia and had no evidence of limb length discrepancies at mean follow-up of 7.4 years.

The author prefers the use of a hybrid ACL reconstruction technique using a femoral physeal sparing retro-drilling technique with a transtibial transphyseal technique for young athletes around a bone age of 12 with at least 2 years of growth remaining. Once preoperative family discussion, preoperative imaging, and subjective outcome measures have been completed, outpatient arthroscopic surgery is scheduled. A discussion about preoperative nerve block(s) including their risks is also included.

The lead author (MDM) prefers a flat OR table utilizing an arthroscopy post for assistance with medial compartment visualization. Alternatively, the senior author (CWN) prefers an arthroscopy leg holder with a dropped foot of the bed. The flat OR table set up allows for more traditional fluoroscopic views. It also allows for easier figure-4 positioning if a lateral meniscus repair is necessary. Its disadvantage includes a more difficult access for posteromedial approaches if a medial meniscal repair is required. The lead author utilizes a Spider arthroscopic holder (Smith & Nephew, Andover, Mass.) in standard ACL reconstructions where hyperflexion is needed during accessory medial portal drilling. However, hyperflexion is not needed during femoral physeal sparing retro-drilling. A thigh tourniquet is applied prior to post or leg holder placement. An examination under anesthesia and compared to the contralateral knee is essential to correctly understand the knee’s ligamentous integrity.

Diagnostic arthroscopy is done first in a standard fashion. Examination should include the patellofemoral compartment, both medial and lateral gutters, medial and lateral compartments, intracondylar notch, and possibly the posteromedial and posterolateral recesses. Anteromedial portal is made under direct visualization. If meniscal or chondral pathology is found, then its treatment is carried out first prior to ACL reconstruction. The author prefers inside-out meniscal repair using 2-0″ Fiberwire meniscal repair needles (Arthrex, Naples, Florida) for most meniscal tears. All-inside repair with 360° Fast-Fix meniscal repair devices (Smith & Nephew, Andover, Mass.) are sometimes utilized for smaller tears.

Once the ACL tear has been confirmed arthroscopically and associated pathology treated, ACL remnants are debrided and a notchplasty may be done depending on the narrowness of the intracondylar notch. Soft tissue grafts are used universally for physeal sparing ACL reconstruction techniques. A quadrupled gracilis and semitendinosis is usually utilized for this technique. Alternatively a quadrupled single tendon semitendinosis graft can also be used (Fig. 15.4). A small amount of tissue may be left on the femoral ACL footprint to assist in placing the femoral tunnel in the center of the native footprint. The arthroscope can be switched to the anteromedial portal for the femoral tunnel drilling. The Flipcutter pediatric ACL femoral guide (Arthrex, Naples, Florida) is utilized at a setting of about 90°. The targeting guide is directed to the center of the ACL femoral footprint. Increasing attention is now paid to the lateral starting point. The percutaneous lateral starting point should be below the femoral physis but also avoid iatrogenic injury to the femoral insertion sites for the LCL and popliteus. There is a very small area posterior to their insertions that also avoids iatrogenic injury to the posterior femoral articular cartilage. Therefore, the author prefers a lateral starting point anterior to the LCL and popliteus insertion. This is usually in line with the mid aspect of the femoral shaft on a perfect lateral of the distal femur on the fluoroscopic view. This still allows for a posterior intra-articular exit point in the center of the ACL footprint. A smaller 2.4 mm guide pin is drilled first and checked on the AP fluoroscopic view to make sure the tunnel will be below the distal femoral lateral physis (Fig. 15.5). Once this is confirmed, the pin is replaced through the drill guide with the appropriate sized Flipcutter for the autologous hamstring autograft (Fig. 15.6). Once the retro-drill has been fully inserted into the notch, it is then deployed and then retro-drilled for a tunnel of at least 20 mm. This can be drilled all the way to the lateral epiphysis cortex. A suture is placed through the tunnel after the drill has been removed for later graft passage.