%0 Journal Article
%T Anterior Cruciate Ligament Graft Conditioning Required to Prevent an Abnormal Lachman and Pivot Shift After ACL Reconstruction: A Robotic Study of 3 ACL Graft Constructs
%A Brad Ashman
%A Frank R. Noyes
%A Lauren E. Huser
%A Michael Palmer
%J The American Journal of Sports Medicine
%@ 1552-3365
%D 2019
%R 10.1177/0363546519835796
%X Anterior cruciate ligament (ACL) graft conditioning protocols to decrease postoperative increases in anterior tibial translation and pivot-shift instability have not been established. To determine what ACL graft conditioning protocols should be performed at surgery to decrease postoperative graft elongation after ACL reconstruction. Controlled laboratory study. A 6 degrees of freedom robotic simulator evaluated 3 ACL graft constructs in 7 cadaver knees for a total of 19 graft specimens. Knees were tested before and after ACL sectioning and after ACL graft conditioning protocols before reconstruction. The ACL grafts consisted of a 6-strand semitendinosus-gracilis TightRope, bone每patellar tendon每bone TightRope, and bone每patellar tendon每bone with interference screws. Two graft conditioning protocols were used: (1) graft board tensioning (20 minutes, 80 N) and (2) cyclic conditioning (5∼-120∼ of flexion, 90-N anterior tibial load) after graft reconstruction to determine the number of cycles needed to obtain a steady state with no graft elongation. After conditioning, the grafts were cycled a second time under anterior-posterior loading (100 N, 25∼ of flexion) and under pivot-shift loading (100 N anterior, 5-N﹞m internal rotation, 7 N﹞m valgus) to verify that the ACL flexion-extension conditioning protocol was effective. Graft board tensioning did not produce a steady-state graft. Major increases in anterior tibial translation occurred in the flexion-extension graft-loading protocol at 25∼ of flexion (mean ㊣ SD: semitendinosus-gracilis TightRope, 3.4 ㊣ 1.1 mm; bone每patellar tendon每bone TightRope, 3.2 ㊣ 1.0 mm; bone每patellar tendon每bone with interference screws, 2.4 ㊣ 1.5 mm). The second method of graft conditioning (40 cycles, 5∼-120∼ of flexion, 90-N anterior load) produced a stable conditioned state for all grafts, as the anterior translations of the anterior-posterior and pivot-shift cycles were statistically equivalent (P < .05, 1-20 cycles). ACL graft board conditioning protocols are not effective, leading to deleterious ACL graft elongations after reconstruction. A secondary ACL graft conditioning protocol of 40 flexion-extension cycles under 90-N graft loading was required for a well-conditioned graft, preventing further elongation and restoring normal anterior-posterior and pivot-shift translations. There is a combined need for graft board tensioning and robust cyclic ACL graft loading before final graft fixation to restore knee stability
%K ACL reconstruction
%K ACL graft elongation
%K ACL graft fixation
%K semitendinosus-gracilis graft
%K bone每patellar tendon每bone graft
%U https://journals.sagepub.com/doi/full/10.1177/0363546519835796