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Delta screw versus RetroScrew tibial fixation for ACL reconstruction
Peter C Rhee1, Diane L Dahm, Michael J Stuart
1Department of Orthopedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
Purpose:
The purpose of this study is to determine whether the RetroScrew tibial fixation system offers a biomechanical advantage over the Delta screw for anterior cruciate ligament (ACL) reconstruction in cadaveric tibias with low bone mineral density (BMD).
Methods:
Ten matched pairs of osteoporotic cadaveric tibiae underwent simulated ACL reconstruction using quadrupled hamstring grafts with one of the two tibial fixation constructs. Group 1 was fixed with the Delta screw (DS; 35-mm antegrade biointerference screw), and group 2 was fixed with the RetroScrew system (RSS; 20-mm retrograde and 17-mm antegrade biointerference screws). Each construct was cyclically loaded (50-200 N, 1 Hz, 500 cycles) and subsequently loaded to failure (20 mm/s).
Results:
All specimens were osteoporotic without significant segmental (proximal, middle, and distal) BMD differences between groups by quantitative computed tomography (P = n.s.). A trend was noted for more construct failures due to graft slippage in the DS group (n = 3) over the RSS group (n = 1). There were no significant differences in cyclic displacement (P = n.s.), maximum cyclic stiffness (P = n.s.), maximum load at failure (P = n.s.), or pullout stiffness (P = n.s.) between groups.
Conclusions:
In an osteoporotic cadaveric model, there was no significant biomechanical advantage of the RetroScrew system versus the Delta screw for tibial fixation in soft tissue graft ACL reconstruction. However, a trend toward lower graft fixation failure to cyclic loading was noted with the RetroScrew system.