2015 ISAKOS Biennial Congress ePoster #1257

Kinematics and Contact Stress Comparison of All Epiphyseal and Complete Transphyseal ACL Reconstructions

Moira McCarthy, MD, New York, NY UNITED STATES
Hamid Jahandar, BS, New York, NY UNITED STATES
Peter D. Fabricant, MD, MPH, New York, NY UNITED STATES
Kyle Stone
James Boorman-Padgett, BS, New York, NY UNITED STATES
Daniel W. Green, MD, MS, New York, NY UNITED STATES
Carl W. Imhauser, PhD, New York, NY UNITED STATES
Frank A. Cordasco, MD, MS, New York, NY UNITED STATES

Hospital for Special Surgery, New York, New York, USA

FDA Status Not Applicable

Summary: All-epiphyseal ACL reconstruction restores stability to the ACL deficient knee and reduces the posterior joint contact stresses seen with ACL deficiency.



Introduction:Pediatric ACL reconstruction techniques can restore stability and contact pressures to the ACL deficient knee. The complete transphyseal (CT) reconstruction uses a vertical graft to minimize physeal trauma. The all-epiphyseal (AE) reconstruction avoids the physis completely. A direct comparison of the kinematics and contact stresses after AE and CT ACL reconstructions have not been studied.
Hypothesis:Both the AE and CT reconstructions will restore translational kinematics but the AE technique will better restore rotational kinematics. The AE reconstruction will more closely replicate the contact stresses of the ACL intact knee compared to the CT reconstruction because of the restoration of rotational stability.
Methods:Nine fresh-frozen human cadaveric knees were tested using a robotic manipulator. Each of the specimens was tested with the intact ACL, the deficient ACL, and after each reconstruction method. Reconstruction order was alternated from specimen-to-specimen. The AE utilized sockets oriented within the epiphyses. The CT had more central and vertical sockets in both the tibia and femur. Both reconstructions were fixed with identical suspensory cortical fixation devices using an all-inside technique and 10 mm diameter hamstring grafts. Anterior stability was assessed with 134N anterior force at 30 and 90° of knee flexion simulating the Lachman and anterior drawer exams, respectively. The pivot shift exam was simulated by applying a combined 8 Nm and 4 Nm of abduction and internal rotation, respectively, at 15 and 30° of knee flexion. Tibiofemoral motions were recorded and mean contact stresses generated within the tibiofemoral compartments were measured using contact stress transducers. Outcomes were compared across conditions of the ACL using generalized estimating equations.
Results:Both reconstructions had significantly decreased anterior translation, medial translation, and internal rotation compared to the ACL deficient knee (Figure 1) in response to a simulated pivot shift. However, internal rotation and medial translation remained elevated beyond ACL-intact levels following the CT reconstruction by 10.5% (P<0.05) and by 75.3% (P<0.05), respectively. During the simulated Lachman and anterior drawer tests, both reconstructions restored anterior translation to that of the ACL intact knee. In response to the pivot-shift, the AE reconstruction decreased lateral posterior contact stresses compared to the ACL-deficient knee. However, following CT reconstruction, they remained elevated compared to the ACL-competent knee (P<0.05). Both reconstruction techniques offloaded the posterior aspect of the medial tibial plateau compared to the ACL-deficient knee in response to anterior loading at 30 and 90° of knee flexion, but the AE had higher posterior contact stresses at 90 compared to the ACL-intact knee.
Conclusion:While both AE and CT reconstructions reduced anterior translations and posteromedial contact stresses in response to an anterior load, the AE technique more effectively reduced axial rotation and posterolateral contact stresses during a simulated pivot shift exam. These findings are likely due to the more oblique anatomic orientation of the AE graft, which makes it a more effective stabilizer to rotational and medial-lateral loads.