Summary
During transphyseal anatomic Anterior Cruciate Ligament (ACL) reconstruction in patients with open growth plates, physeal damage should be minimized. This 3D MRI simulation model study identified that the maximum distal femoral physis (DFP) and proximal tibial physis (PTP) damage was obtained when drilling larger and less vertical tunnels at ACL anatomical reconstruction.
Abstract
Purpose
During transphyseal anatomic Anterior Cruciate Ligament (ACL) reconstruction in patients with open growth plates, physeal damage should be minimized. The orientation of tunneling that minimizes distal femoral physis (DFP) and proximal tibial physis (PTP) damage has been a topic of discussion. The objective of this study was to describe the physeal damage depending on the tunnel orientation in a three-dimensional (3D) model of transphyseal anatomic ACL reconstruction.
Methods
Eighty magnetic resonance images (MRI) from patients aged 10 to 17 were obtained and randomly sampled from the institutional database, with a homogeneous distribution of age and sex. A de novo software was developed to obtain 3D models of the distal femur, DFP, proximal tibia and PTP. In each model, the femoral and tibial ACL footprints were determined as established in cadaveric and imaging studies by previous authors. Drillings were simulated using 7-, 8-, 9- and 10-mm drills, starting from the ACL footprint point at every possible angle within a 90° cone. The angles were defined considering the zero vector (0°, 0°) as perpendicular to the ACL footprint. Physeal injury for each pair of angles and each drill size was determined. Damage was expressed as a percentage of the total growth plate volume. The segmentation, measurement, and statistical analysis were developed in MATLAB software. Statistical analysis was conducted using Student’s t test, one-way ANOVA, Mann Whitney and Kruskal-Wallis test. Statistical significancy p<0.05.
Results
A total of 43 knees with open tibial growth plates were obtained, with a mean age of 12.7 [SD 1.7], 40% women. A total of 52 knees with femoral open growth plate were obtained, with a mean age of 13.1 [SD 2], 44% women. Maximum DFP damage was obtained when drilling more horizontally (15° cephalic and 70° anterior) with a 10-mm drill, 14.6% [SD 3.9]. The maximum femoral physeal injury was statistically different between drill sizes (p < 0.001) and sexes (p < 0.001). There were no differences considering age (p = 0.29). Less than 7% femoral DFP damage was obtained with a more vertical tunnel (>15° cephalic and <70° anterior). Maximum PTP damage was obtained when drilling more obliquely (45° medially and 10° anterior) with a 10-mm drill 5.5% [SD 2.4], statistically different between drill sizes (p < 0.01) and ages (p = 0.002). There were no differences considering sex (p = 0.75). PTP damage had a more homogeneous behavior within the transphyseal limits, and more than 7% of mean tibial physeal damage was not obtained, regardless of the diameter or direction evaluated.
Conclusions
This MRI simulation model study identified that the maximum DFP and PTP damage was obtained when drilling larger tunnels, and in case of the DFP when drilling less vertical tunnels, regardless of age. DFP tunnels damage a larger volume. If more vertical tunnels are made, less than 7% of femoral growth plates are damaged, regardless of the diameter of the tunnel.