Techniques and Complications of Transphyseal Anterior Cruciate Ligament Reconstruction in the Skeletally Immature Patient

Introduction

In general, the treatment of anterior cruciate ligament (ACL) injuries in adults has been extensively analyzed. However, this does not stand true for skeletally immature patients. The increasing incidence of such injuries, as well as the substantial spectrum and gravity of secondary complications, highlights the necessity for more in-depth research in this field.

Injuries in pediatric and adolescent athletes have dramatically increased. Midsubstance ACL tears in children, once thought to be rare, have nowadays increased considerably, especially in contact sports involving cutting, pivoting, and collision. Recent studies report a higher incidence of ACL ruptures in young female athletes. Stanitski et al. reported that nearly one out of two preadolescent athletes presenting with acute knee hemarthrosis is suffering from an acute ACL rupture.

Besides isolated ACL ruptures, additional injuries such as damage to collateral ligaments and associated meniscal tears may occur. The prevalence of such additional injuries is mostly double-digit, ranging up to 100% depending on the study.

Since this patient group is characterized by the presence of an open physis, ACL ruptures provoke some controversy regarding optimal treatment strategy. This controversy is further exacerbated by the scarcity of data regarding long-term sequelae. To protect the open physis, conservative treatment as well as different ACL reconstruction techniques, including physeal-sparing, all-epiphyseal, partial, or complete-transphyseal reconstruction techniques, have been developed.

Transphyseal Anterior Cruciate Ligament Reconstruction

Historically conservative treatment of ACL ruptures in children was state of the art to avoid the risk of causing growth disturbances by surgery. However, poor results were reported by most of the studies dealing with conservative treatment of isolated ACL ruptures. Patients demonstrated instability, lower Tanner activity level and Lysholm scores, and developed radiological signs of joint degeneration. Rationale for operative treatment of children with isolated ACL injuries is to treat intra-articular injuries requiring surgical intervention and prevent further damage to the knee joint (meniscal tears, cartilage lesions) due to instability and therefore possible development of osteoarthritis. Reconstruction of a torn ACL in these patients always carries the risk of damaging the open growth plates, consecutively affecting the longitudinal or axial growth of the lower extremity either on the femoral or the tibial side and leading to leg-length discrepancy and axial deformities. Since 65% of the leg length leads from the distal femur and the proximal tibia, transphyseal reconstruction techniques are regarded with concern in patients with open growth plates.

The technique involves a tunnel being drilled across both the tibial and femoral physes. The positioning of the graft is anatomical, while the fixation is transphyseal. The technique has always been approached with skepticism due to the possibility of growth disturbance, leading to leg-length discrepancy and axial deformities. Analyzing the causes of growth disturbance in 15 patients, Kocher et al. reported that the most important reason for growth arrest (12 out of 15) was the presence of staples or screws of bone plugs, passed across the physes, thus acting as a mechanical block. Similar results were also presented by Lipscomb et al. and Koman et al. On the contrary, Guzzanti et al. and Stadelmaier et al. demonstrated that the presence of a graft traversing the physes blocks the formation of a bony-bridge, thus preventing growth arrest. Due to the previously mentioned complications, ACL reconstruction in skeletally immature patients should only be carried out by specialist surgeons with expertise in both arthroscopic reconstruction of the ACL and children’s injuries, in dedicated units with appropriate facilities for rehabilitation. Additionally, strict compliance with certain technical rules is required when using this technique for this specific group of patients: (1) tunnel diameter must not exceed a diameter of 8 mm and the tunnels must be as vertical and as central as possible in order to minimize the percentage of growth-cartilage surface area exposed to the damage, and (2) strut bone grafts or interference screws bridging the physes should be avoided. Cortical fixation at the femoral side and fixation using a resorbable screw no longer than 25 mm combined with a staple at the tibial side represent safe techniques for graft fixation in this population. However, to successfully reconstruct the ACL of a skeletally immature patient, the orthopaedic surgeon must always assess the following issues before the operation: (1) patient’s skeletal maturity, (2) time of reconstruction, (3) graft type, and (4) possible complications.

Assessment of Skeletal Maturity

Skeletal age on skeletally immature patients can be assessed with various techniques, including radiological evaluation through reference atlases, comparison of patients’ height with those of their family, and sexual maturity. In most of the recent studies, the Tanner staging system has been widely applied.

Older studies recommended physeal-sparing techniques or all-epiphyseal techniques for patients with Tanner stages I and II. However, more recent literature data support that transphyseal ACL reconstruction represents a relatively safe technique for Tanner I and II patients. Kaeding et al., in their systematic review, stated that transphyseal technique was safe in Tanner stages II and III. However, they noted a lack of sufficient evidence to support transphyseal reconstruction for Tanner I patients. Later on, Frosch et al., showed low rates of complications in this specific patient group. Recent data published by Liddle et al. and Nikolaou et al. reported no growth or axis disturbances for Tanner I and II patients. Kumar et al., in their study of 32 Tanner I and II patients with transphyseal ACL reconstruction, found only one patient with re-rupture and one with a mild valgus deformity without any functional disturbance. Of the 15 patients comprising the authors’ study group (mainly Tanner II and III), no re-ruptures were noted, while one patient developed a progressive valgus deformity of the distal femur due to harmed posterolateral epiphyseal plate leading to an early localized growth stop. In the systematic review of Moksnes et al., four studies with the highest methodological scores reported a good functional outcome after reconstruction and a low rate of growth disturbance. However, Vavken et al., in a recent systematic review, documented that in this population, functional outcomes following ACL reconstruction correlate with the experience of the surgeons performing the technique.