Abstract
Background:
Anterior cruciate ligament (ACL) graft conditioning protocols to decrease postoperative increases in anterior tibial translation and pivot-shift instability have not been established.
Purpose:
To determine what ACL graft conditioning protocols should be performed at surgery to decrease postoperative graft elongation after ACL reconstruction.
Study Design:
Controlled laboratory study.
Methods:
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–patellar tendon–bone TightRope, and bone–patellar tendon–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.
Results:
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–patellar tendon–bone TightRope, 3.2 ± 1.0 mm; bone–patellar tendon–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).
Conclusion:
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.
Clinical Relevance:
There is a combined need for graft board tensioning and robust cyclic ACL graft loading before final graft fixation to restore knee stability.
Keywords
Get full access to this article
View all access options for this article.