title: One- and two-incision anterior cruciate ligament reconstruction: a biomechanical comparison including the effect of simulated closed-chain exercise.
abstract: The purpose of this study was to evaluate the effect of simulated closed-chain exercise on anterior translation in the anterior cruciate ligament (ACL) reconstructed knee comparing patellar tendon grafts secured with endoscopic and two-incision techniques. ACL reconstructions, were performed on five matched pairs of fresh frozen cadaver lower extremities. One of each pair had endoscopic (inside-out) placement of the femoral interference screw and other had outside-in femoral screw placement. A model for closed-chain exercise was developed to simulate half squat exercises using a custom apparatus on the Material Testing machine with a 356 N (80 lb) axial load and 40 N (9 lb) static hamstring force. Knee motion from near full extension to 60 degrees flexion was achieved by varying the quadricep force. One thousand squats were performed, and KT-1000 arthometry was done before and after cycling each specimen. The femur-graft-tibia constructs were then stressed to failure. Closed-chain cycling resulted in no significant change in anterior translation in either group. The mean maximum load to failure of the femur-graft-tibia construct was 340.4N in the one-incision group and 434.2 N in the two-incision group. P=.048 was considered statistically significant. Anterior translation did not increase after 1,000 simulated half knee bends in either the one- or two-incision groups. Shallow knee bends are an important part of aggressive rehabilitation programs, and our data support the position that these closed-chain exercises do not deleteriously affect the graft. Though the maximum strength to failure differed significantly between the one- and two-incision groups, both techniques offered sufficient strength to withstand an aggressive simulated rehabilitation protocol.
authors.affiliation: Department of Orthopaedic Surgery, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: P G
authors.initials: PG
authors.lastname: Dalldorf
authors.forename: J
authors.initials: J
authors.lastname: Alexander
authors.forename: D M
authors.initials: DM
authors.lastname: Lintner
mesh_terms: D000368:Aged; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001182:Arthroscopy; D001863:Bone Screws; D002102:Cadaver; D004724:Endoscopy / Q000379:methods; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D016059:Range of Motion, Articular; D013314:Stress, Mechanical; D013710:Tendons / Q000637:transplantation*