Reduction in Diameter of Hamstring Autograft With Additional Circumferential Preconditioning During ACL Reconstruction in a Pediatric Population

Abstract

Background: Over 130,000 anterior cruciate ligament (ACL) reconstructions (ACLRs) are performed annually in the United States. Previous studies have shown that circumferential preconditioning reduces the diameter of fresh-frozen allografts, but no studies have described the effect in ACL autografts used during ACLR. Purpose: To characterize the changes in the hamstring autograft diameter as a result of preparatory circumferential preconditioning. Study Design: Case series; Level of evidence, 4. Methods: A total of 135 patients with ACLR, with a median age of 15 years (interquartile range, 14-16 years; 50.4% boys), were identified in 2 pediatric hospitals. Three orthopaedic surgeons recorded hamstring autograft diameters at 2 time points during graft preparation. Hamstring tendons were prepared using a standardized procedure, tensioned to 15 to 20 lbs, and measured using cylindrical sizing guides. The graft was left with passive compression in the smallest initial rigid sizing guide for 10 minutes on both the tibial and femoral sides and then measured again immediately before implantation. Tunnels were drilled based on the second measurement of graft size. Comparisons were made between the graft diameter before and after circumferential preconditioning. A random-effects regression model and a linear regression model were performed to capture any unexplained variance on the linear predictor scale and determine correlations between demographics and graft characteristics. Results: The median initial diameter for both femoral and tibial sides was 9.5 mm. After longitudinal tension and circumferential preconditioning, the median autograft diameter of both sides decreased by 1 mm ( P < .001) to 8.5 mm. In the random-effects model, decreased patient height was a significant predictor of greater reduction in graft diameter. Increased height was a significant predictor for greater initial graft diameter (average beta coefficient = 3.08; P < .01). No intraoperative complications were noted with implantation of the preconditioned grafts in smaller diameter tunnels. Conclusion: The median diameter of hamstring ACL autografts decreases by 1 mm after circumferential preconditioning within standard cylindrical sizing guides. This allowed for drilling of tunnels that were an average of 1 mm smaller without any noted intraoperative complications with graft insertion.