Any athlete who tears their ACL is at risk to tear their opposite knee ACL. This risk can be higher than re-tearing the original graft. Paterno et al. report a 30% re-tear rate within 2 years after an ACLR in young patients, with 70% being the opposite knee tear, and 30% being ipsilateral knee graft failure. Ho et al. found that contralateral ACL tore in 8% of pediatric patients versus 9.6 ipsilateral graft tears [2]. Rehab of a reconstructed ACL should include the contralateral uninjured ACL. Systematic reviews of ACL prevention programs usually find a positive effect, but this is controversial [14, 15].

Meniscal tears are common among the very young athletes who sustain an ACL tear. Almost all meniscal tears in the young should be candidates for a meniscal repair. Many tears are bucket handle tears and these often involve capsular detachment of the whole meniscus and run from the anterior to the posterior horn (Fig. 19.3). Inside-out repair technique using high strength 2-0 sutures is recommended due to the high number of sutures needed for the extensive meniscal repair. All inside suture devices may not be optimal with bucket handle repair due to the high number of implants necessary which can overpopulate the meniscus with the nonabsorbable end toggles of each implant. Peripheral menisco-capsular tears cannot be sewn together with an all-inside suture device that is for intra-meniscal tears. These peripheral tears must anchor the meniscus down to the capsule. Root avulsions, root tears, complex tears, radial tears, and in folded parrot beak tears can be reduced and sutured, but require advanced meniscal suturing techniques. Outside-in technique is particularly helpful for anterior horn tears. In a review of 30 patients with all-epiphyseal ACL reconstruction, there were four re-tears of bucket handle meniscal repair, so the author recommends multiple high strength nonabsorbable sutures that grab a big bite of the meniscus and repair it to the joint capsule. Kocher et al. also noted four meniscal re-tears in their series of 44 intra/extra-articular physeal sparing ACL reconstructions in very young patients [5]. Any meniscal tear, whether virgin or a re-tear of a previously repaired meniscus should raise suspicion of a lax or unstable ACL graft. Carefully check Lachman’s and pivot shift tests in the operating room, along with inspection of the ACL graft.

Overgrowth can be more common than undergrowth in young children and physeal sparing techniques do not completely eliminate all risk of a growth disturbance after ACL reconstruction in the skeletally immature [16, 17]. The authors suspect that overgrowth may be due to periosteal stimulation near a growth plate, similar to femur overgrowth in femur fractures, and the Cozen phenomenon seen after minor proximal tibia fractures as Chotel et al. suggested [18]. Leg lengths and leg alignment should be measured/inspected at each pre-op and post-op visit until the patient is skeletally mature (Fig. 19.4). If there is a trend toward overgrowth, manifested as an increasing limb length discrepancy or an angular knee deformity, a minimally invasive percutaneous epiphysiodesis can be performed to correct the overgrowth or angulation, as long the patient has adequate growth remaining [19].

Cases of growth arrest causing limb shortening or angulation have been sporadically reported in the literature [18, 20–22]. These can be caused by bony bar formation across the growth plate, or by the tether effect of hardware such as an interference screw, a staple, a suture loop suspensory device, or even sutures placed across a growth plate. Anderson et al. mentioned that they found no growth disturbance in 50 cases using his all-epiphyseal technique . They recommend drilling the smallest tunnels that will accommodate the patient’s hamstring graft diameter. They minimized the suture bulk of the graft by sewing the semitendinosis and gracilis tendon ends together with a single suture [23, 24]. Most importantly, a well tensioned and firmly anchored soft tissue graft placed across the growth plate can also cause a growth arrest due to the tether effect. The traditional mantra for transphyseal tunnels is to drill vertical tunnels that are ≤6–8 mm diameter [21, 25]. Unfortunately recent studies have shown that vertical tunnels can lead to persistent rotary instability despite good anteroposterior stability and that graft size (in adults) ≤8 mm is associated with increased graft failure.

In animal studies almost every well tensioned and well fixated graft placed across a wide open growth plate can cause a growth arrest [26–31]. Un-tensioned and poorly anchored grafts that violate over 7% of the growth plate’s cross-sectional area can also cause a growth arrest [32, 33]. One unique advantage of all-epiphyseal techniques of ACL reconstruction in the skeletally immature is that the theoretical risks of growth arrest from both drilling though the growth plate and from the tether effect are eliminated. Anatomic transportal techniques for drilling a transphyseal femoral tunnel will ream out a much larger swath of the distal femoral growth plate due to their oblique trajectory verses a trans-tibial drilled tunnel. Anatomic transphyseal techniques should be avoided in patients with wide open growth plates. A transverse all-epiphyseal tunnel or a physeal sparing intra/extra-articular technique is preferred in the very young athlete [5, 34].

Stiffness can complicate 8% of ACL reconstructions in young patients [35]. The author rehabilitates his immature patients identical to adults with immediate weight bearing as tolerated without any limits on motion. Patients may remove their post-op knee immobilizers at any time, and are instructed to remove it by post-op day #3 for slow gentle knee extension and flexion. It should be totally discontinued by post-op day #7. Swimming is encouraged to start on post-op #7. Formal physical therapy is started on about post-op day #7. Crutches are discontinued at about 3 weeks post-op when the physical therapist deems the patient safe for unassisted ambulation.

The author performs a 2–3 mm lateral and anterior notchplasty , especially when inserting a quintupled hamstring graft (tripled semitendinosis, doubled gracilis) which often measures 8.5–10 mm diameter. The author also places a tibial tunnel aperture as medial as possible with the tibial guide pin touching the lateral edge of the PCL. With an anatomic femoral tunnel the graft can impinge along the lateral wall of the notch especially at flexion angles >45° and can lead to stiffness and require manipulation under anesthesia and revision notchplasty in rare cases. If by 4–6 weeks postoperative the patient has greater than 10 degrees of full extension or cannot flex past 90 degrees then the author considers manipulation under anesthesia. The author uses an extension board starting at the first post-op visit (POD#7) if the patient has unusual stiffness. Serial extension casting (without surgery) can also be effective for mild to moderate knee flexion contracture in the first 6 weeks after surgery [36].