Original article
Initial Biomechanical Properties of Staple–Anchor Achilles Tendon Allograft and Interference Screw Bone–Patellar Tendon–Bone Autograft Fixation for Anterior Cruciate Ligament Reconstruction in a Cadaveric Model

https://doi.org/10.1016/j.arthro.2006.08.004Get rights and content

Purpose: Anterior cruciate ligament (ACL) reconstruction is a common procedure that has a fairly high success rate. Despite such success, controversy exists with regard to fixation and graft type. The purpose of this study was to quantify the maximum load to failure for staple–anchor freeze-dried Achilles tendon allograft fixation compared with interference screw bone–pattelar tendon–bone autograft fixation at the time of insertion for ACL reconstruction. Methods: Eleven pairs of cadaveric knees were prepared for ACL reconstruction by disarticulation before graft insertion. The tibia and femur were mounted separately onto an MTS machine and were loaded to failure in line with the tunnels. Femoral fixation for the allograft was provided by a staple anchor; tibial fixation was provided by a suture anchor. Titanium interference screws on the femoral and tibial sides provided autograft fixation. A paired t test was performed to compare mechanical testing results in the 2 groups. Results: Mean maximum load to failure for the allograft was 58.7 N (range, 32.3 to 92.6 N) and 119.6 N (range, 82 to 165.9 N) for the femur and the tibia, respectively, compared with 228.2 N (range, 74.2 to 352 N) and 232.9 N (range, 65.1 to 553.1 N) for the autografts. This difference was statistically significant (P < .001) for femoral fixation, but it was not statistically significant for tibial fixation (P = .186). Conclusions: Soft tissue Achilles tendon allograft with staple fixation is a significantly weaker fixation construct when compared with autograft bone–patellar tendon–bone with interference screw fixation. Clinical Relevance: This study shows significantly weaker fixation in the staple-alograft construct and yet this construct has had at least equivalent results over a 5-year time frame, indicating that rigid femoral fixation may not be a critical factor in long-term results.

Section snippets

Methods

Eleven matched pairs of fresh frozen cadaveric knees were used in this study. Bone density measures of the metaphyseal bone of the tibia and femur were obtained through quantitative computed tomography scanning (Norland/Stratec XCT 3000A; Stratec Medizintechnik GmbH, Pforzheim, Germany). For preparation of the autograft, the central third of the patellar tendon, along with 25-mm bone plugs from the patella and the tibia, was harvested. Remaining soft tissues were removed for preparation of the

Results

The average age of the cadaveric specimens was 75.4 years. No statistical difference was found in average bone density between the right and left sides of the specimens. One of the specimens, along with its matched pair, was removed from analyses because the ultimate strength of the femoral interference screw was greater than 2 standard deviations above the mean (Table 1). Mean ultimate strength for the femoral staple was 58.7 N (±19.4; range, 32.3 to 92.6 N) compared with 228.2 N (±101.7;

Discussion

Successful reconstruction of the ACL depends on several factors, including graft selection, accurate placement of the tibial and femoral tunnels, and stable fixation that allows early functional rehabilitation.5, 10, 11, 12, 13 Graft selection has been debated throughout the literature for many years.5, 6, 14 ACL reconstruction with a BPTB autograft fixed with interference screws is a widely used procedure because of the reliable characteristics of the graft during bone-to-bone healing and the

Conclusions

Soft tissue Achilles allograft with staple fixation of the femur is a significantly weaker fixation method when compared with autograft BPTB with interference screw fixation in a cadaveric model.

Acknowledgment

The authors thank Arthrex, Instrument Makar/Smith & Nephew, Orthofix, and the Musculoskeletal Transplant Foundation for donating materials and supplies for this study, and Annemarie Johnson, CMI, for Figure 2.

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    The authors report no conflict of interest.

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    Copyright © 2006 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.