Dynamic Effect of Quadriceps Muscle Activation on Anterior Tibial Translation After Single-Bundle and Double-Bundle Anterior Cruciate Ligament Reconstruction.

PURPOSE: To examine differences in anterior tibial translation in 3 groups: single-bundle anterior cruciate ligament (ACL)-reconstructed, double-bundle ACL-reconstructed, and ACL-intact knees under gradual dynamic quadriceps muscle activation. METHODS: Thirty male patients underwent successful single-bundle (n = 15) and double-bundle (n = 15) ACL reconstructions; 15 healthy controls were included in the study. Anterior tibial translation was assessed at 30° of knee flexion in the resting position (0% quadriceps activation) and under 50% and 100% of maximum quadriceps concentric contraction using an isokinetic dynamometer with the KT-2000 arthrometer securely attached to the participants' knees. RESULTS: The 2 ACL-reconstructed groups were similar regarding International Knee Documentation Committee (IKDC), Knee Injury and Osteoarthritis Score (KOOS), Tegner, and Lysholm scores and preliminary isokinetic evaluation (P = .38). Quadriceps activation significantly affected anterior tibial translation (P = .001, α = 0.98). In all 3 study groups, anterior tibial translation was significantly higher under 100% quadriceps activation compared with 0% contraction (P = .01) and 50% quadriceps activation (P = .047). There were no between-group differences in anterior tibial translation with 0%, 50%, or 100% quadriceps activation (P = .46). CONCLUSIONS: Under quadriceps muscle activation, anteroposterior knee laxity in ACL-intact and ACL-reconstructed knees is gradually increased. Single-bundle and double-bundle ACL-reconstructed knees show a similar increase in anterior tibial translation under gradual quadriceps contraction. When comparing different ACL reconstruction techniques in the experimental setting, dynamic, in addition to static, testing is advised to reach a comprehensive assessment of anteroposterior knee stability. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Effect of fatigue on tibial rotation after single- and double-bundle anterior cruciate ligament reconstruction: a 3-dimensional kinematic and kinetic matched-group analysis.

BACKGROUND: Fatigue is an extrinsic factor adversely affecting joint proprioception and neuromuscular response, thereby increasing anterior cruciate ligament (ACL) strain and injury risk. The effectiveness of the single- and double-bundle techniques for ACL reconstruction to control residual rotational knee laxity under fatigue has not been examined. HYPOTHESIS: Fatigue results in a significant increase in tibial rotation angles and moments in both ACL-intact and single- and double-bundle ACL-reconstructed knees. The 2 groups with ACL-reconstructed knees will show no significant differences in tibial rotation angles and moments either pre- or postfatigue. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-four male patients who underwent successful single-bundle (n = 12) or double-bundle (n = 12) ACL reconstructions and 10 matched healthy controls were subjected to a standard lower limb muscle fatigue protocol using an isokinetic dynamometer. Three-dimensional motion analysis was used to measure tibial rotation and rotational knee moments in the pre- and postfatigue states, during a swinging maneuver on the weightbearing leg from a standing position with the knee in extension. RESULTS: Tibial rotation of the single-bundle group significantly increased postfatigue (prefatigue 22° ± 10° vs 29° ± 15° postfatigue, P = .015). In contrast, the double-bundle group showed similar tibial rotation values pre- and postfatigue (16° ± 6° vs 18° ± 4°, P = .22). The double-bundle group showed a trend toward decreased tibial rotation values pre- and post-fatigue compared with controls (22 ± 4 and 23 ± 4) (P = .065 and .08, respectively). In the prefatigue state, rotational moments (N·mm/Kg) of the single-bundle (339 ± 148) and double-bundle (317 ± 97) groups were significantly lower than that of controls (465 ± 134) (P = .05 and .03, respectively). In the postfatigue state, an increase was observed in rotational moments of the single-bundle (388 ± 131) and double-bundle (408 ± 187) groups compared with prefatigue values, whereas a decrease was noted in the control group (411 ± 117). CONCLUSION: Single-bundle ACL-reconstructed knees demonstrate a reduced ability to resist rotational loads under fatigue. Double-bundle reconstructed knees had significantly better control of tibial rotation when fatigued. However, they demonstrate an excessive, yet not significant, reduction in tibial rotation compared with the intact knee, suggesting a possible overcorrection in rotational laxity.