Tendon graft fixation in ACL reconstructionIn vitro evaluation of bioabsorbable tenodesis screw

Abstract

Background Conventional ACL reconstruction requires sufficient tibial bone quality for secure graft fixation. We evaluated the mechanical characteristics of a supplemental tenodesis screw in cadaveric specimens.Material and methods One group of 7 specimens from 7-paired tibiae was randomly assigned to undergo tibialis anterior tendon graft-bone tunnel fixation with a bioabsorbable interference screw, using conventional ACL reconstruction techniques. The other group of 7 specimens underwent the same procedure supplemented with a bioabsorbable tenodesis screw. All specimens were subjected to pullout testing on a servo hydraulic device.Results Specimens in the supplemental fixation group had double the load to failure (tenodesis = 467 (SD 184) N, control group = 223 (SD 66) N, p = 0.02) and were also one-third stiffer (tenodesis = 31 (SD 13) N/mm, control group = 21 (SD 6) N/mm, p = 0.03) than the specimens in the conventional fixation group.Interpretation Supplemental bioabsorbable tenodesis screw fixation may be advantageous for primary reconstruction in patients with low tibial bone mineral density or during revision procedures. By providing secure soft tissue graft-tibia fixation during the early phase after ACL reconstruction, supplemental tenodesis fixation may enable patients to participate safely in more intense, early rehabilitation.

Tibial Fixation Properties of a Continuous-Loop ACL Hamstring Graft Construct with Suspensory Fixation in Porcine Bone

“…14 We chose to utilize an interference screw as the control based on multiple published studies of tibial graft fixation that have used interference screws. 21,[31][32][33] The diameters of grafts for interference screw fixation (range, 8-9 mm) were less than for suspensory fixation (range, 9-10 mm) in this study. This was based on the differences in graft construction in that grafts for interference screw fixation were doubled two-tendon constructs whereas grafts for suspensory fixation were quadrupled single-tendon constructs.…”

“…We chose to utilize tibial interference screw fixation as the control group consistent with multiple previous biomechanical studies. 21,[31][32][33] Our null hypothesis was that suspensory fixation of quadrupled continuous loop semitendinosus ACL graft constructs in tibial sockets will have biomechanical properties that are not significantly different from interference screw fixation of doubled semitendinosus-gracilis ACL graft constructs in tibial tunnels when tested ex vivo in porcine bone.…”

Hybrid Tibia Fixation of Soft Tissue Grafts in Anterior Cruciate Ligament Reconstruction

“…In 2 of these studies, the mean BMD of hybrid fixation specimens and control specimens was significantly different, although in 1 case this was by § design. 22,23 BMD in tested specimens varied widely and in many cases was far lower than reported values for young human tibial metaphysis.…”

“…§ Five used human cadaveric specimens. 22,29,47,50,52 One used both animal and human cadaveric bone. 34 Among studies using human cadaveric bone (n = 6), 3 used elderly specimens, 2 used middle-aged specimens, and 1 used elderly specimens reinforced with foam to approximate young human bone.…”

ACL Fixation Devices

“…The addition of an EndoButton to the RetroScrew increases the maximum failure strength at the tibial site from 679 to 1027 N. 35 Other potential augmentation devices which may be used in conjunction with an interference screw include the double spike plate, Biotenodesis screw, PLLA ball, cortical disc, cortical screw, and staple. [36][37][38][39][40] Graft laceration is a concern when metal interference screws are used with soft tissue grafts. Although the biodegradable screws are comparable to titanium screws for failure loads and stiffness, they cause less graft laceration.…”