2015 ISAKOS Biennial Congress ePoster #1328

Early Outcomes for a New Interference Fixation Technique to Salvage Femoral Posterior Wall Compromise in ACL Reconstruction

Geoffrey B. Higgs, MD, Richland, WA UNITED STATES
Kathryn Smith, PhD, Atlanta, GA UNITED STATES

Advanced Orthopaedics, Richmond, Virginia, USA

FDA Status Cleared

Summary: This study presents an method to salvage the biomechanical integrity of Anterior Cruciate Reconstruction when posterior wall compromise occurs during ACL reconstruction without compromising the ability to maintain aperture interference fixation.

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Abstract:

Early Outcomes for a new Interference Fixation Technique to Salvage Femoral Posterior Wall Compromise in ACL Reconstruction
Geoffrey Higgs MD, Kathryn Smith PhD

Introduction

In anterior cruciate ligament (ACL) reconstruction, aperture interference fixation is considered an advantageous approach as it provides a stiffer graft construct, reduced intra-tunnel motion, and soft tissue graft compression to promote direct contact healing. In an effort to recreate the native ACL footprint, the femoral tunnel is drilled with a thin posterior wall. However, the posterior wall can become compromised, or “blowout” during tunnel drilling, graft insertion or deployment of the fixation device, resulting in loss of aperture fixation. A suspensory fixation method is typically used to salvage the femoral fixation, but this sacrifices aperture fixation and graft compression, potentially compromising the quality of the ACL reconstruction. The goal of this study is to describe a new salvage technique that provides near aperture fixation and present early patient outcomes along with its biomechanical performance.

Methods

The new technique was performed in 6 patients (5 primary procedures, 1 revision) undergoing an ACL reconstruction where a posterior wall blowout resulted during initial preparation. Once determined that the posterior wall was compromised, a secondary tunnel was created by perforating the femoral tunnel at an obtuse angle 5mm from the tunnel entrance in the intercondylar notch. The tibial drill guide is used to create the tunnel with its entrance on the anterior lateral aspect of the lateral femoral condyle. The graft was fixated using the Exoshape Tibial ACL Fixation Device (MedShape Inc., Atlanta, GA, USA) per standard technique. This is an expandable PEEK sheath-and-bullet system that compresses and fixates the graft at aperture. Follow-up occurred at 10 days, 4, 8, 12, and 16-20 weeks. At these times, negative Lachman, pivot shift, and anterior drawer tests were performed. KT-1000 exams were performed at 3 and 6 months. To evaluate the utility of the fixation method with the expandable device, pullout testing was performed on graft-device constructs in porcine bone. Whip-stitched bovine tendons were fixated in porcine bone with the ExoShape device, a PEEK interference screw, or metal interference screw (all 9 mm) and pulled to failure at 50mm/min. Pullout strength was measured as the ultimate load to failure (n=10).

Results

There were no postoperative complications. All patients were satisfied with their outcome. All patients achieved excellent results with matched KT-1000 exams, negative Lachman, pivot shift and anterior drawer. All patients were able to return to prior level of athletic activity between 6-8 months. Biomechanical testing showed that the average ± standard deviation pullout strength of graft constructs fixated with the expandable PEEK device (1254±246N) was significantly higher than the PEEK screw (696±143N) and titanium interference screw (1024±102N) (p-value<0.05).

Conclusion

All patients showed improvement in the clinical scoring 6 to 12 months after surgery. Biomechanical testing indicated that the fixation approach with an expandable interference device provides superior fixation strength compared with traditional fixation approaches. These results demonstrate the potential utility of this technique to salvage a posterior wall blowout without compromising aperture fixation and graft compression.