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Background: Persistent clinical instability after anterior cruciate ligament (ACL) reconstruction may be associated with injury to the anterolateral structures and has led to renewed interest in anterolateral extra-articular procedures. The influence of these procedures on knee kinematics is controversial. Purpose/Hypothesis: The purpose was to investigate the biomechanical properties of anatomic anterolateral ligament (ALL) reconstruction and a modified Lemaire procedure (lateral extra-articular tenodesis [LET]) in combination with ACL reconstruction as compared with isolated ACL reconstruction in the setting of deficient anterolateral structures (ALL and Kaplan fibers). It was hypothesized that both techniques would reduce tibial internal rotation when combined with ACL reconstruction in the setting of anterolateral structure deficiency. Study Design: Controlled laboratory study. Methods: A 6 degrees of freedom robotic system was used to assess tibial internal rotation, a simulated pivot-shift test, and anterior tibial translation in 10 paired fresh-frozen cadaveric knees. The following states were tested: intact; sectioned ACL, ALL, and Kaplan fibers; ACL reconstruction; and an anterolateral extra-articular procedure (various configurations of ALL reconstruction and LET). Knees within a pair were randomly assigned to either ALL reconstruction or LET with a graft tension of 20 N and a randomly assigned fixation angle (30° or 70°). ALL reconstruction was then repeated and secured with a graft tension of 40 N. Results: In the setting of deficient anterolateral structures, ACL reconstruction was associated with significantly increased residual laxity for tibial internal rotation (up to 4°) and anterior translation (up to 2 mm) laxity as compared with the intact state. The addition of ALL reconstruction or LET after ACL reconstruction significantly reduced tibial internal rotation in most testing scenarios to values lower than the intact state (ie, overconstraint). Significantly greater reduction in laxity with internal rotation and pivot-shift testing was found with the LET procedure than ALL reconstruction when compared with the intact state. Combined with ACL reconstruction alone, both extra-articular procedures restored anterior tibial translation to values not significantly different from the intact state with most testing scenarios (usually within 1 mm). Conclusion: Residual laxity was identified after isolated ACL reconstruction in the setting of ALL and Kaplan fiber deficiency, and the combination of ACL reconstruction in this setting with either ALL reconstruction or the modified Lemaire LET procedure resulted in significant reductions in tibiofemoral motion at most knee flexion angles, although overconstraint was also identified. ALL reconstruction and LET restored anterior tibial translation to intact values with most testing states. Clinical Relevance: ALL reconstruction and lateral extra-articular tenodesis have been described in combination with intra-articular ACL reconstruction to address rotational laxity. This study demonstrated that both procedures resulted in significant reductions of tibial internal rotation versus the intact state independent of graft tension or fixation angle, although anterior tibial translation was generally restored to intact values. The influence of overconstraint with anterolateral knee reconstruction procedures has not been fully evaluated in the clinical setting and warrants continued evaluation based on the findings of this biomechanical study. [ABSTRACT FROM AUTHOR] more...

Objectives: Lateral extra-articular tenodesis (LET) reduces ACL graft failure rates two years after surgery when performed as an adjunct to ACL reconstruction (ACLR). Interestingly, previous biomechanical studies have shown that LET may reduce tibial rotation beyond that of the intact knee, while others found no such kinematic overconstraint. Parameters of ligament engagement have proven useful in characterizing the biomechanical function of the ACL and the anterolateral ligament; however, they have not been used to describe the biomechanics of LET. In this study, we compared engagement parameters (engagement point, in situ stiffness, and tissue force at peak applied load) of an LET-reconstructed knee compared to the native lateral tissues in response to an internal rotation torque at 0°, 30°, 60°, and 90° of knee flexion. Methods: Seven cadaveric knees (mean age: 39 ± 12; range: 28-54; 4 male) were mounted to a robotic manipulator. The robot applied an internal rotation torque of 5 Nm while monitoring the resulting internal tibial rotation (ITR) (in degrees). Each knee was tested following a bone-patellar tendon-bone ACL reconstruction with intact lateral tissues (consisting of the anterolateral ligament and Kaplan fibers) and after sectioning these tissues and performing LET (modified Lemaire technique). Resultant forces carried by the native lateral tissues and the LET were determined via superposition. The parameters of engagement were determined for both the native lateral tissues and the LET and compared via two-way repeated measures ANOVA (p < 0.05). Results: During an internal rotation test at full extension (0° of flexion), both the LET-reconstructed and native lateral tissues did not engage. At 30°, 60°, and 90° knee flexion, the native lateral tissues exhibited more in situ slack than the LET-reconstructed lateral tissues. Specifically, the native lateral tissues had 8° (p < 0.001), 13° (p < 0.001), and 14° (p < 0.001) more in situ slack than the LET-reconstructed lateral tissues at 30°, 60°, and 90° knee flexion, respectively. At 30° of flexion, the LET-reconstructed lateral tissues were 9° (p < 0.001) and 10° (p < 0.001) more slack than at 60° and 90° knee flexion. Across all three tested knee flexion angles (30°, 60°, and 90°), the LET-reconstructed lateral tissues had greater in situ stiffness than the native lateral tissues. The LET carried greater force at the peak applied internal rotation torque by 29 N at 30° of flexion (p = 0.006), but no statistical differences were identified at the other flexion angles. Conclusions: LET creates a supraphysiologic restraint to the native lateral tissues by engaging with less internal tibial rotation than the native lateral tissue at all flexion angles tested but full extension. The LET also carried greater force at the peak applied load and had a greater in situ stiffness at 30° of flexion than the native lateral tissues. On the whole, LET is a supraphysiological restraint to internal tibial rotation at 30° of flexion. The engagement point of LET may be modified surgically by altering the flexion angle, degree of tibial rotation at which the tenodesis is fixed, and/or the tension applied. Thus, discrepancies between previous biomechanical studies may arise from variations in one or more of these modifiable surgical parameters. Figure 1. Mean tissue force versus internal tibial rotation response of the LET and native lateral tissues with applied internal rotation torque at 0,30,60, and 90° of knee flexion. Whiskers represent one standard deviation. Engagement point denoted in yellow. Tissue force at peak applied internal tibial rotation torque denoted in blue. [ABSTRACT FROM AUTHOR] more...

Objectives: Increased posterior tibial slope (PTS) has been identified as a risk factor for both short-term and long-term failure after anterior cruciate ligament (ACL) reconstruction. Correction of PTS may improve outcomes after revision ACL reconstruction. Conflicting reports demonstrate the most accurate way to measure the PTS on standard short knee radiographs versus longstanding lateral radiographs including the entire tibia. Many reports advocate short knee radiographs as adequate for the evaluation of posterior tibial slope and deciding surgical treatment. The purpose of this study was to compare posterior tibial slope measurements between standard short segment knee (SSK) and longstanding lateral knee radiographs (LSL) in a failed ACL cohort. We hypothesize that there is high variability in SSK measurements compared to LSL. Our secondary hypothesis is that our series of surgical deformity corrections for failed ACL reconstructions with increased PTS includes a significant number of biplanar deformities requiring altered technique to completely address all deformities. Methods: The medial and lateral PTS were measured on 35 consecutive patients with failed ACL reconstructions using SSK and LSL using previously published techniques. Coronal plane deformity was assessed by the tibiofemoral angle on AP long standing films. All measurements were made by two trained independent observers at two different times separated by one month for calculation of inter- and intra-observer reliability using intra-class correlation coefficients (ICCs). Measurements recorded by the observer with the higher intra-observer ICC for the SSK and LSL were used for calculation. Paired t-tests were used for direct comparison of tibial slope measurements between the SSK and LSL conditions. P-values less than 0.05 were considered statistically significant. Results: There was a statistically significant difference in average lateral plateau PTS between standard short knee lateral and longstanding lateral radiographs (11.0 degrees versus 12.2 degrees, P =0.031). More importantly, 66.6% of the absolute measurements differed by at least 3 degrees, with variability as high as 7 degrees in our series as shown in Figures 1 and 2. 20/35 patients (57.1%) also had varus or valgus deformity > 2 degrees. Twelve patients underwent posterior slope correction as part of their revision ACL reconstruction. 8/12 of those patients (66.7%) had varus/valgus deformity > 2 degrees, and 41.7% (5/12) of patients required biplanar proximal tibial osteotomy correction to adequately address their multiplanar deformity. Conclusions: Long segment radiographs more completely evaluate the complex deformities of posterior tibial slope associated with failed ACL reconstruction, with less variability than standard short knee radiographs. In our series, a high percentage of patients needed biplanar correction, and we recommend obtaining long segment anteroposterior and lateral radiographs as essential imaging in these patients. [ABSTRACT FROM AUTHOR] more...

The article presents a study that investigates the kinematic differences between anatomic single-bundle (aSB) and anatomic double-bundle (aDB) posterior cruciate ligament reconstructions (PCLR) at the time of surgery compared with the native and complete PCL sectioned states. The study explores if an aSB or aDB PCLR technique would be most effective in restoring native knee kinematics. It hypothesizes that an aDB PCLR would more closely restore native knee kinematics compared with an aSB PCLR. more...

The article presents a study that determines the primary biomechanical function of the isolated posteromedial bundle, anterolateral bundle, and the intact posterior cruciate ligament (PCL) between 0° and 120°of knee flexion. The study explores the role of PCL's functional bundles through the full range of knee flexion. It suggests a codominant relationship between the two bundles based on their ability to resist posterior tibial translation. more...

Background: The anterior cruciate ligament (ACL) has been well defined as the main passive restraint to anterior tibial translation (ATT) in the knee and plays an important role in rotational stability. However, it is unknown how closely the ACL and other passive and active structures of the knee constrain translations and rotations across a set of functional activities of increasing demand on the quadriceps.Hypothesis: Anterior tibial translation and internal rotation of the tibia relative to the femur would increase as the demand on the quadriceps increased.Study Design: Controlled laboratory study.Methods: The in vivo 3-dimensional knee kinematics of 10 adult female patients (height, 167.8 ± 7.1 cm; body mass, 57 ± 4 kg; body mass index [BMI], 24.8 ± 1.7 kg/m2; age, 29.7 ± 7.9 years) was measured using biplane fluoroscopy while patients completed 4 functional tasks. The tasks included an unloaded knee extension in which the patient slowly extended the knee from 90° to 0° of flexion in 2 seconds; walking at a constant pace of 90 steps per minute; a maximum effort isometric knee extension with the knee at 70° of flexion; and landing from a height of 40 cm in which the patient stepped off a box, landed, and immediately performed a maximum effort vertical jump.Results: Landing (5.6 ± 1.9 mm) produced significantly greater peak ATT than walking (3.1 ± 2.2 mm) and unweighted full extension (2.6 ± 2.1 mm) (P < .01), but there was no difference between landing and a maximum isometric contraction (5.0 ± 1.9 mm). While there was no significant difference in peak internal rotation between landing (19.4° ± 5.7°), maximum isometric contraction (15.9° ± 6.7°), and unweighted full knee extension (14.5° ± 7.7°), each produced significantly greater internal rotation than walking (3.9° ± 4.2°) (P < .001). Knee extension torque significantly increased for each task (P < .01): unweighted knee extension (4.7 ± 1.2 N·m), walking (36.5 ± 7.9 N·m), maximum isometric knee extension (105.1 ± 8.2 N·m), and landing (140.2 ± 26.2 N·m).Conclusion: Anterior tibial translations significantly increased as demand on the quadriceps and external loading increased. Internal rotation was not significantly different between landing, isometric contraction, and unweighted knee extension. Additionally, ATT and internal rotation from each motion were within the normal range, and no excessive amounts of translation or rotation were observed.Clinical Relevance: This study demonstrated that while ATT will increase as demand on the quadriceps and external loading increases, the knee is able to effectively constrain ATT and internal rotation. This suggests that the healthy knee has a safe envelope of function that is tightly controlled even though task demand is elevated. [ABSTRACT FROM PUBLISHER] more...