Hybrid Transtibial Femoral Preparation for Transphyseal Anterior Cruciate Ligament Reconstruction: A Radiographic Comparison to Transtibial and Anteromedial Portal Techniques

BACKGROUND: Transphyseal anterior cruciate ligament (ACL) reconstruction remains the most commonly used technique for pubescent patients. The principles of creating vertical and central femoral tunnels are well accepted to minimize physeal area of injury and are typically accomplished with a transtibial (TT) technique. This, however, may come at the expense of a non-anatomic tunnel. The hybrid transtibial (HTT) technique offers the potential of combining an anatomic femoral position with tunnel geometry similar to the TT technique but has never been assessed in a clinical cohort. HYPOTHESIS/PURPOSE: We hypothesized that tunnels created by a HTT technique would be similar in orientation and physeal location to TT tunnels, but significantly more vertical and central than tunnels created with an anteromedial portal (AM). METHODS: We retrospectively screened all ACL reconstructions performed in children aged 10 to 16 years, at our institution between 2013 to 2019, with the requirements of having a transphyseal reconstruction and an available post-operative radiographs. Radiographs were then assessed for the coronal femoral tunnel angle (FTA), as well as the location of the tunnel-physis penetration on the AP (LTAP) and lateral (LTL) views. Physeal lesion surface area was calculated. Data were compared between the three groups using ANOVA. RESULTS: Forty-seven patients met eligibility criteria with 9 TT, 18 AM, and 20 HTT patients. Mean patient age was 14.3 +/- 1.2 years. The FTA was significantly more vertical in the TT (60.7(o) +/-7.2) and HTT (54.4(o) +/- 5.7) groups as compared to the AM group (48.8(o) +/- 5.9); p = 0.0037 and p = 0.02 respectively. There was no significant difference between the TT and HTT groups ( p = 0.066). The LTAP was not significantly different between groups (p = 0.097). The LTL demonstrated that the HTT tunnels penetrated the physis at a more central location in the sagittal plane (28.9% +/- 4.8%) than the AM tunnels (20.0% +/- 5.1%, p = 0.00002), but was statistically indistinguishable from the TT (24.4%+/- 4.0%, p= 0.066) tunnels. CONCLUSION: The hybrid transtibial technique presents an option for transphyseal ACL reconstruction, with femoral tunnel obliquity and estimated physeal disruption similar to the TT technique, significantly less than the AM technique. The HTT also results in the most central physeal perforation of all techniques, predominantly in the sagittal plane. With the known ability of the HTT technique to recreate an anatomic femoral footprint, this may represent the “best of both worlds” for transphyseal ACL reconstruction. TABLES/FIGURES: