Addition of the Sartorius Tendon Improves Biomechanics of a Four-Strand Hamstring Anterior Cruciate Ligament Autograft

Smaller Width Quadriceps Tendon Grafts Maintain Advantageous Biomechanical Properties for ACL Reconstruction

Background

Despite clinical evidence of risks in knee arthrofibrosis and graft impingement with larger grafts, the optimal size for quadriceps tendon (QT) autografts in anterior cruciate ligament reconstruction (ACLR) has not been established.

Purpose/Hypothesis

This study aimed to evaluate the mechanical properties of full-thickness 6-mm and 8-mm wide QT grafts compared with 10-mm patellar tendon (PT) and 10-mm QT grafts. The hypothesis was that both the 6- and 8-mm QT grafts would exhibit similar or superior ultimate tensile strength compared with the 10-mm PT graft.

Study Design

Controlled laboratory study.

Methods

A total of 18 matched pairs of cadaveric knees were used in this study. From each pair, a 10-mm wide full-thickness QT was harvested from 1 knee. Based on randomization, a 6-mm wide or 8-mm wide full-thickness QT along with a 10-mm wide PT were harvested from the contralateral knee. Each tendon was clamped, tensioned, and cycled on a servohydraulic testing machine before final loading to failure.

Results

The ultimate failure load was 1286 ± 237.3 N for the 10-mm QT, 1056 ± 226.7 N for the 8-mm QT, 935.1 ± 283.8 N for the 6-mm QT, and 816 ± 192.7 N for the 10-mm PT. Ultimate tensile strength differed significantly between the 10-mm and 8-mm QT (P = .004), 10-mm and 6-mm QT (P < .001), 10-mm QT and 10-mm PT (P < .001), and 8-mm QT and 10-mm PT grafts (P < .001), but not between the 6-mm QT and 10-mm PT grafts (P = .152).

Conclusion

The 8-mm QT had higher ultimate tensile strength than the 10-mm PT, and the 6-mm QT was comparable to the 10-mm PT. Full-thickness QT grafts <10 mm in width may maintain sufficient tensile strength for ACLR.

Clinical Relevance

Given these biomechanical properties, smaller QT graft sizes may be advantageous in minimizing arthrofibrosis risk while maintaining graft strength.

Estimation Failure Risk by 0.5-mm Differences in Autologous Hamstring Graft Diameter in Anterior Cruciate Ligament Reconstruction: A Meta-analysis

BACKGROUND

Because grafts are made in 0.5-mm increments clinically for anterior cruciate ligament (ACL) reconstruction, it is important to clarify how the failure rate decreases as the diameter increases. Moreover, it is important to know whether even a slight increase in the graft diameter decreases the risk of failure.

HYPOTHESIS

The risk of failure decreases significantly with each 0.5-mm increase in hamstring graft diameter.

STUDY DESIGN

Meta-analysis; Level of evidence, 4.

METHODS

The systematic review and meta-analysis have estimated the diameter-specific failure risk for each 0.5-mm increase in ACL reconstruction using autologous hamstring grafts. We searched for studies describing the relationship between graft diameter and failure rate published before December 1, 2021, in leading databases, such as PubMed, EMBASE, Cochrane Library, and Web of Science, according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. We included studies using single-bundle autologous hamstring grafts to investigate the relationship between failure rate and graft diameter of 0.5-mm intervals with >1-year follow-up. Then, we calculated the failure risk caused by 0.5-mm differences in autologous hamstring graft diameter. Assuming Poisson distribution for the statistical model, we employed an extended linear mixed-effects model in the meta-analyses.

RESULTS

Five studies containing 19,333 cases were eligible. The meta-analysis revealed that the estimated value of the coefficient of diameter in the Poisson model was -0.2357 with a 95% CI of -0.2743 to -0.1971 (P < .0001). With every 1.0-mm increase in diameter, the failure rate decreased by 0.79 (0.76-0.82) times. In contrast, the failure rate increased by 1.27 (1.22-1.32) times for each 1.0-mm decrease in diameter. The failure rate significantly decreased with each 0.5-mm increase in graft diameter in the range of <7.0 to >9.0 mm from 3.63% to 1.79%.

CONCLUSION

The risk of failure decreased correspondingly with each 0.5-mm increase in graft diameter in the range of <7.0 to >9.0 mm. Failure is multifactorial; however, increasing the graft diameter as much as possible to match each patient's anatomic space without overstuffing is an effective precaution that surgeons can take to reduce failures.

Editorial Commentary: Addition of the Sartorius Tendon to Small-Diameter Hamstring Anterior Cruciate Ligament Autografts May Improve Outcomes in Pediatric and Revision Cases

Graft selection in anterior cruciate ligament reconstruction can have a pivotal role in a successful outcome. One of the major concerns with hamstring autograft is the variability of the diameter of each tendon, and grafts with a diameter of less than 8 mm may result in an increased failure rate. The addition of the sartorius tendon as a fifth strand in small-diameter hamstring autografts increases graft strength and diameter. This may improve outcomes in pediatric and revision cases.