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

Abstract

Background: Transphyseal anterior cruciate ligament (ACL) reconstruction remains the most commonly used technique for pubescent patients. The transtibial (TT) drilling technique creates vertical and central femoral tunnels to minimize the physeal area of injury at the expense of a nonanatomic femoral tunnel. The hybrid TT (HTT) technique offers the potential of an anatomic femoral position with tunnel geometry similar to that using the TT technique.

Purpose/hypothesis: The purpose was to perform a radiographic comparison of the HTT technique with TT and anteromedial portal (AM) techniques in adolescent patients undergoing transphyseal ACL reconstruction. It was hypothesized that femoral tunnels created during HTT would be similar to TT tunnels but significantly more vertical and central than AM tunnels.

Study design: Cohort study; Level of evidence, 3.

Methods: We retrospectively screened primary transphyseal ACL reconstructions performed in adolescents at our institution between 2013 and 2019. The youngest 20 eligible patients were selected from each technique cohort: TT, AM, and HTT. Postoperative radiographs were assessed for the coronal femoral tunnel angle, as well as the location of the tunnel-physis penetration on the anteroposterior and lateral views. Physeal lesion surface area was calculated. Data were compared among the 3 groups using 1-way analysis of variance followed by pairwise comparisons.

Results: Included were 47 patients with a mean ± SD age of 14.3 ± 1.2 years (n = 9 with TT, 18 with AM, and 20 with HTT techniques). The coronal tunnel angle was significantly more vertical in the TT (60.7° ± 7.2°) and HTT (54.4° ± 5.7) groups as compared with the AM group (48.8° ± 5.9; P = .0037 and P = .02, respectively). There was no significant difference between the TT and HTT groups (P = .066). The only significant finding regarding femoral tunnel location was that the HTT tunnels (28.9% ± 4.8%) penetrated the physis more centrally than did the AM tunnels (20.0% ± 5.1%; P = .00002) on lateral radiographs.

Conclusion: The HTT technique presents an option for transphyseal ACL reconstruction, with femoral tunnel obliquity and estimated physeal disruption similar to that of the TT technique and significantly less than that of the AM technique. The HTT technique also results in the most central physeal perforation of all techniques, predominantly in the sagittal plane.

Keywords: ACL; anatomy; pediatric sports medicine; physis.

Figure 1.

CONSORT flow diagram of the patient selection process. *Exclusion criteria based on group can be found in Table 1. ACLR, anterior cruciate ligament reconstruction; AM, anteromedial portal; HTT, hybrid transtibial; postop, postoperative; TT, transtibial; XR, radiograph.

Figure 2.

Pathfinder guide for hybrid transtibial drilling technique.

Figure 3.

Measurement on anteroposterior radiograph for (A) the femoral tunnel angle with respect to the physis (FTA) and (B) the location of the tunnel on the anteroposterior (LTAP), recorded in percentages as the distance from the center of the femoral tunnel as it passes through the physis to the lateral cortex (thick solid line) divided by the entire width of the distal femur along a line parallel to the distal femoral condyles (dashed line). (C) Measurement on lateral radiograph for the location of the tunnel on the lateral (LTL) view, recorded in percentages as the distance between the center of the femoral tunnel as it passes through the physis and the posterior cortex (thick solid line) divided by the entire anteroposterior dimension of the lateral condyle along a line parallel to the physis (dashed line). For the measurements in panels B and C, a smaller number represents a more peripheral tunnel location.

Figure 4.

The quadrant method.

Figure 5.

Femoral tunnel angle by drilling technique. Values are presented as median (horizontal line), interquartile range (box), and 95% CI (vertical line). AM, anteromedial portal; HTT, hybrid transtibial; TT, transtibial.

Figure 6.

(A) Location of tunnel on the anteroposterior (AP) radiograph. The values are reported as percentiles along the width of the femoral physis. Lower values represent more lateral locations, and higher values represent more medial locations, with 50 representing the midpoint of the femoral physis. (B) Location of tunnel on the lateral radiograph. The values are reported as percentiles along the width of the femoral physis. Lower values represent more posterior locations, and higher values represent more anterior locations, with 50 representing the midpoint of the femoral physis. Values are presented as median (horizontal line), interquartile range (box), and 95% CI (vertical line). AM, anteromedial portal; HTT, hybrid transtibial; TT, transtibial.

Figure 7.

Using the formula for an ellipse, we calculated the cross-sectional surface area of physeal disruption for each drilling technique based on various hypothetical reamer sizes. The black hatches at the top of each bar represent the magnitude of error. Values are presented as median (horizontal line), interquartile range (box), and 95% CI (vertical line). AM, anteromedial portal; HTT, hybrid transtibial; TT, transtibial.