Anterior Tibial Load Research Articles

Diameter of Quadrupled Semitendinosus Autograft in Primary Anterior Cruciate Ligament Reconstruction Did Not Impact Early Revision Rate or Functional Outcome in a Large Cohort of Patients

To determine whether the diameter of the quadrupled semitendinosus tendon (ST) graft in primary anterior cruciate ligament reconstruction (ACLR) is related to the risk of revision ACLR within 2 years of primary ACLR, postoperative knee laxity and patient reported knee outcome. Furthermore, to investigate whether smaller graft than estimated is related to revision ACLR. Patients who underwent primary ACLR with a quadrupled ST autograft at our institution, from January 2005 to December 2017 were identified. Data from the Swedish National Knee Ligament Registry (SNKLR) were collected up to two years or until revision surgery was registered within two years after primary ACLR. Knee laxity was assessed, pre-operatively and at 6-months follow up using the KT-1000 arthrometer (134 N anterior tibial load). The Knee injury and Osteoarthritis Outcome Score (KOOS) were collected preoperatively and at two years postoperatively from SNKLR. Based on anthropometric measurements (body height and weight) and sex the estimated quadrupled ST graft diameter was calculated. A total of 4,519 patients who underwent ACLR with a quadrupled ST autograft were included. The mean graft diameter was 8.3 mm± 0.7 mm; 8.0 mm± 0.6 mm for women and 8.6 mm ± 0.7 mm for men. The quadrupled ST graft diameter was not significantly correlated to revision ACLR. There was no significant difference in the ST graft diameter regarding post-operative knee laxity. The correlations between ST graft diameter and KOOS were weak, except for the "Sport and Recreation" subscale (P=.012). The quadrupled ST graft diameter was not significantly related to the need for early revision ACLR nor was related to postoperative knee laxity or patient reported outcome except for the KOOS "Sport and Recreation" subscale. Smaller ST graft than estimated was not a risk factor for revision ACLR. The outcome after ACLR is multifactorial and ST graft diameter is of no significant importance.

The 45° and 60°of sagittal femoral tunnel placement in anterior cruciate ligament reconstruction provide similar knee stability.

The aim of the present study was to compare 45° and 60°of sagittal femoral tunnel angles in terms of anterior tibial translation (ATT), valgus angleand graft in situ force following anterior cruciate ligament reconstruction (ACLR). Ten porcine knees were subjected to the following loading conditions: (1) 89 N anterior tibial load at 35° (full extension), 60° and 90° of knee flexionand (2) 5 N m valgus tibial moment at 35° and 45° of knee flexion. ATTand graft in situ force of the intact anterior cruciate ligament (ACL) and ACLR were collected using a robotic universal force/moment sensor (UFS) testing system for (1) ACL intact, (2) ACL-deficient (ACLD) and (3) two different ACLR using different sagittal femoral tunnel angles (coronal 45°/sagittal 45° and coronal 45°/sagittal 60°). During the anterior tibial load, the femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° and 60° had significantly higher ATT than that of the ACL-intact knees at 60° of knee flexion (p < 0.05). The femoral tunnel angle of ACLR knees at coronal 45°/sagittal 60° had significantly lower graft in situ force than that of the ACL-intact knees at 60° and 90° of knee flexion (p < 0.05). During the valgus tibial moment, the femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° and 60° had significantly lower graft in situ force than that of the ACL-intact knees at all knee flexions (p < 0.05). The femoral tunnel angle of ACLR knees at coronal 45°/sagittal 45° provided similar ATT, valgus angleand graft in situ force to that of ACLR knees at coronal 45°/sagittal 60°. Therefore, both femoral tunnel angles could be used in ACLR, as the sagittal femoral tunnel angle does not appear to be relevant in post-operative knee stability. Not applicable.

Anterior cruciate ligament injury should not be considered a contraindication for medial unicompartmental knee arthroplasty: Finite element analysis.

The research objective of this study is to use finite element analysis to investigate the impact of anterior cruciate ligament (ACL) injury on medial unicompartmental knee arthroplasty (UKA) and explore whether patients with ACL injuries can undergo UKA. Based on the morphology of the ACL, models of ACL with diameters ranging from 1 to 10mm are created. Finite element models of UKA include ACL absence and ACLs with different diameters. After creating a complete finite element model and validating it, four different types of loads are applied to the knee joint. Statistical analysis is conducted to assess the stress variations in the knee joint structure. A total of 11 finite element models of UKA were established. Regarding the stress on the ACL, as the diameter of the ACL increased, when a vertical load of 750N was applied to the femur, combined with an anterior tibial load of 105N, the stress on the ACL increased from 2.61 MPa to 4.62 MPa, representing a 77.05% increase. Regarding the equivalent stress on the polyethylene gasket, a notable high stress change was observed. The stress on the gasket remained between 12.68 MPa and 14.33 MPa in all models. the stress on the gasket demonstrated a decreasing trend. The equivalent stress in the lateral meniscus and lateral femoral cartilage decreases, reducing from the maximum stress of 4.71 MPa to 2.61 MPa, with a mean value of 3.73 MPa. This represents a reduction of 44.72%, and the statistical significance is (P < 0.05). However, under the other three loads, there was no significant statistical significance (P > 0.05). This study suggests that the integrity of the ACL plays a protective role in performing medial UKA. However, this protective effect is limited when performing medial UKA. When the knee joint only has varying degrees of ACL injury, even ACL rupture, and the remaining structures of the knee joint are intact with anterior-posterior stability in the knee joint, it should not be considered a contraindication for medial UKA.

The Effect of Lateral Extra-articular Tenodesis in an ACL-Reconstructed Knee With Partial Medial Meniscectomy: A Biomechanical Study

Background: Knee laxity increases with medial meniscectomy in anterior cruciate ligament (ACL)–reconstructed knees; however, the biomechanical effect of an additional lateral extra-articular tenodesis (LET) is unknown. Purpose/Hypothesis: The purpose of this study was to determine the kinematic effect of a LET in knees that underwent combined ACL reconstruction (ACL-R) and partial medial meniscus posterior horn (MMPH) meniscectomy. It was hypothesized that the addition of LET would reduce laxity in the ACL-reconstructed knee. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen human cadaveric knees (mean age, 41.5 years) were tested using a robotic system under 3 loads: (1) 89.0 N of anterior tibial (AT) load, (2) 5 N·m of internal rotation (IR) tibial torque, and (3) a simulated pivot shift—a combined valgus of 7 N·m and IR torque of 5 N·m—at 0°, 15°, 30°, 45°, 60°, and 90° of knee flexion. Kinematic data were acquired in 4 states: (1) intact, (2) ACL-R, (3) ACL-R + partial MMPH meniscectomy (MMPH), and (4) ACL-R + partial MMPH meniscectomy + LET (MMPH+LET). Results: In response to AT loading, there was a significant increase seen in AT translation (ATT) in the MMPH state at all knee flexion angles compared with the ACL-R state, with the highest increase at 90° of knee flexion (mean difference, 3.1 mm) (P < .001). Although there was a significant decrease in ATT at 15° of knee flexion with MMPH+LET (P = .022), no significant differences were found at other knee flexion angles (P > .05). In MMPH with IR torque, a significant increase was observed in IR at all knee flexion angles except 90° compared with the ACL-R state (range, 2.8°-4.9°), and this increase was significantly decreased at all flexion angles with the addition of LET (range, 0.7°-1.6°) (P < .05). Conclusion: Performing a partial MMPH meniscectomy increased ATT and IR in response to AT and IR loads compared with the isolated ACL-R state in a cadaveric model. However, when the LET procedure was performed after partial MMPH meniscectomy, a significant decrease was seen at all knee flexion angles except 90° in response to IR and torque, and a significant decrease was seen at 15° of knee flexion in response to AT load. Clinical Relevance: LET may be a useful adjunct procedure after ACL-R with partial MMPH meniscectomy to reduce knee laxity.

Augmenting ACL Repair With Suture Tape Improves Knee Laxity: A Biomechanical Study.

Anterior cruciate ligament (ACL) repair is an alternative to reconstruction; however, suture tape support may be necessary to achieve adequate outcomes. To investigate the influence of suture tape augmentation (STA) of proximal ACL repair on knee kinematics and to evaluate the effect of the 2 flexion angles of suture tape fixation. Controlled laboratory study. Fourteen cadaveric knees were tested using a 6 degrees of freedom robotic testing system under anterior tibial (AT) load, simulated pivot-shift (PS) load, and internal rotation (IR) and external rotation loads. Kinematics and in situ tissue forces were evaluated. Knee states tested were (1) ACL intact, (2) ACL cut, (3) ACL repair with suture only, (4) ACL repair with STA fixed at 0° of knee flexion, and (5) ACL repair with STA fixed at 20° of knee flexion. ACL repair alone did not restore the intact ACL AT translation at 0°, 15°, 30°, or 60° of flexion. Adding suture tape to the repair significantly decreased AT translation at 0°, 15°, and 30° of knee flexion but not to the level of the intact ACL. With PS and IR loadings, only ACL repair with STA fixed at 20° of flexion was not significantly different from the intact state at all knee flexion angles. ACL suture repair had significantly lower in situ forces than the intact ACL with AT, PS, and IR loadings. With AT, PS, and IR loadings, adding suture tape significantly increased the in situ force in the repaired ACL at all knee flexion angles to become closer to that of the intact ACL state. For complete proximal ACL tears, suture repair alone did not restore normal knee laxity or normal ACL in situ force. However, adding suture tape to augment the repair resulted in knee laxity closer to that of the intact ACL. STA with fixation at 20° of knee flexion was superior to fixation with the knee in full extension. The study findings suggest that ACL repair with STA fixed at 20° could be considered in the treatment of femoral sided ACL tears in the appropriate patient population.

Repair of Ramp Lesions of the Medial Meniscus With ACL Reconstruction Can Better Restore Knee Stability: A Cadaveric Study.

Ramp lesions of the medial meniscus have an impact on joint stability in anterior cruciate ligament (ACL)-deficient knees, but the impact of lesion length and repair is unclear. The purpose of this cadaveric study was to evaluate the effect of medial meniscal ramp lesion repair on the biomechanics of ACL-deficient knee joints. It was hypothesized that (1) ramp lesions will increase the anterior tibial translation (ATT), internal rotation (IR), and external rotation (ER) in ACL-deficient knee joints; (2) increasing the length of the ramp lesion will further increase the ATT, IR, and ER; and (3) repairing the ramp lesion will reduce the ATT, IR, and ER after ACL reconstruction. Controlled laboratory study. Included were 9 fresh-frozen cadaveric specimens (4 left knees, 5 right knees; 6 males and 3 females; mean age, 60 years [range, 40-73 years]). The specimens were tested on a biomechanical rig. Two external loading conditions were applied: a 134-N anterior tibial load and 5-N·m internal/external tibial torque with the knee at full extension and at 15°, 30°, 60°, and 90° of flexion. ATT was tracked via a high-speed video camera. The following knee states were tested: intact; ACL-deficient; ACL-deficient combined with a 5-, 10-, 15-, or 20 mm-long ramp lesion of the medial meniscus; ACL reconstruction; and ACL reconstruction combined with ramp lesion repair. The ATT, IR, and ER at all knee angles were analyzed by 1-way analysis of variance. The ATT, IR, and ER were significantly increased after cutting of the ACL (P < .05). The ATT, IR, and ER continued to increase when ACL deficiency was combined with ramp lesions of 5 to 20 mm in length (P < .05). The ATT, IR, and ER significantly decreased after ACL reconstruction and ACL reconstruction combined with ramp lesion repair (P < .05). The laxity of knees with ACL deficiency combined with a ramp lesion of the medial meniscus increased more obviously as the ramp lesion increased in length. In a cadaveric model, ACL reconstruction combined with ramp repair improved knee joint stability.

Hourglass-shaped grafts are superior to conventional grafts for restoring knee stability and graft force at knee flexion angle of 30° following anterior cruciate ligament reconstruction: A finite element analysis.

Background: Anterior cruciate ligament reconstruction (ACLR) using a generally columnar graft is considered the gold standard for treating anterior cruciate ligament ruptures, but such grafts cannot replicate the geometry and mechanical properties of the native anterior cruciate ligament. Purpose: To evaluate the effectiveness of an innovative hourglass-shaped graft versus a traditional columnar graft for restoring joint stability and graft force, while avoiding notch impingement following anterior cruciate ligament reconstruction. Methods: Finite element models of a human knee were developed to simulate ① An intact state, ② anterior cruciate ligament reconstruction using columnar grafts with different diameters (7.5-12mm in 0.5mm increments), ③ anterior cruciate ligament reconstruction using columnar grafts with different Young's moduli (129.4, 168.0 and 362.2MPa) and ④ anterior cruciate ligament reconstruction using hourglass-shaped grafts with different Young's moduli. The knee model was flexed to 30° and loaded with an anterior tibial load of 103N, internal tibial moment of 7.5Nm, and valgus tibial moment of 6.9Nm. The risk of notch impingement, knee stability and graft forces were compared among the different groups. Results: This study found that columnar grafts could not simultaneously restore knee stability in different degree of freedoms (DOFs) and graft force to a level similar to that of the intact knee. The anterior tibial translation and graft force were restored to a near-normal condition when the internal tibial rotation was over-restrained and valgus tibial rotation was lax. A graft diameter of at least 10mm was needed to restore knee stability and graft force to physiological levels, but such large grafts were found to be at high risk of notch impingement. In contrast, the hourglass-shaped graft was able to simultaneously restore both knee stability and graft force at knee flexion of 30° while also having a much lower risk of impingement. Conclusion: Under knee flexion angle of 30°, an hourglass-shaped graft was better able to restore joint stability and graft force to a near-physiological level than columnar grafts, while also reducing the risk of notch impingement.

The Role of the Medial Meniscus in Anterior Knee Stability.

Few studies have compared the force distribution between the anterolateral, posterolateral, and medial structures of the knee. To investigate the important structures in an intact knee contributing to force distribution in response to anterior tibial load. Controlled laboratory study. Nine fresh-frozen cadaveric knee specimens underwent robotic testing. First, 100 N of anterior tibial load was applied to the intact knee at 0°, 15°, 30°, 60°, and 90° of knee flexion. The anterior cruciate ligament (ACL), anterolateral capsule, lateral collateral ligament, popliteal tendon, posterior root of the lateral meniscus, superficial medial collateral ligament, posterior root of the medial meniscus (MM), and posterior cruciate ligament were then completely transected in sequential order. After each transection, the authors reproduced the intact knee motion when a 100-N anterior tibial load was applied. By applying the principle of superposition, the resultant force of each structure was determined based on the 6 degrees of freedom force/torque data of each state. At every measured knee flexion angle, the resultant force of the ACL was the largest of the tested structures. At knee flexion angles of 60° and 90°, the resultant force of the MM was larger than that of all other structures with the exception of the ACL. The MM was identified as playing an important role in response to anterior tibial load at 60° and 90° of flexion. In clinical settings, the ACL of patients with a poorly functioning MM, such as tear of the MM posterior root, should be monitored considering the large resultant force in response to an anterior tibial load.

Finite Element Analysis and Experimental Validation of the Anterior Cruciate Ligament and Implications for the Injury Mechanism.

This study aimed to establish a finite element model that vividly reflected the anterior cruciate ligament (ACL) geometry and investigated the ACL stress distribution under different loading conditions. The ACL’s three-dimensional finite element model was based on a human cadaveric knee. Simulations of three loading conditions (134 N anterior tibial load, 5 Nm external tibial torque, 5 Nm internal tibial torque) on the knee model were performed. Experiments were performed on a knee specimen using a robotic universal force/moment sensor testing system to validate the model. The simulation results of the established model were in good agreement with the experimental results. Under the anterior tibial load, the highest maximal principal stresses (14.884 MPa) were localized at the femoral insertion of the ACL. Under the external and internal tibial torque, the highest maximal principal stresses (0.815 MPa and 0.933 MPa, respectively) were mainly concentrated in the mid-substance of the ACL and near the tibial insertion site, respectively. Combining the location of maximum stress and the location of common clinical ACL rupture, the most dangerous load during ACL injury may be the anterior tibial load. ACL injuries were more frequently loaded by external tibial than internal tibial torque.

Graft Diameter Should Reflect the Size of the Native Anterior Cruciate Ligament (ACL) to Improve the Outcome of ACL Reconstruction: A Finite Element Analysis.

The size of the anterior cruciate ligament (ACL) often varies between individuals, but such variation is not typically considered during ACL reconstruction (ACLR). This study aimed to explore how the size of the ACL affects the selection of a suitable graft diameter. A finite element model of a human knee was implanted with intact ACLs of different dimensions (0.95, 1 and 1.05 times the size of the original ACL) and with grafts of different diameters, to simulate ACLR (diameter 7.5–12 mm in 0.5 mm increments). The knee models were flexed to 30° and loaded with an anterior tibial load of 103 N, internal tibial moment of 7.5 Nm, and valgus tibial moment of 6.9 Nm. Knee kinematics (anterior tibial translation (ATT), internal tibial rotation (ITR) and valgus tibial rotation (VTR)) and ligament forces were recorded and compared among the different groups. The results showed that, compared with the intact knee, a graft diameter of 7.5 mm was found to increase the ATT and VTR, but reduce the graft force. Increasing the graft diameter reduced knee laxity and increased the graft force. A 10% increase in the size of the ACL corresponded to a 3 mm larger graft diameter required to restore knee stability and graft force after ACLR. It was concluded that the graft diameter should be selected according to the dimensions of the native ACL, for better restoration of knee functionality. This study may help to improve the clinical treatment of ACL ruptures.

Arthroscopic centralization reduces extrusion of the medial meniscus with posterior root defect in the ACL reconstructed knee.

The purpose of this study was to evaluate the effects of arthroscopic meniscal centralization reinforcement for a medial meniscus (MM) posterior root defect on knee kinematics and meniscal extrusion in the anterior cruciate ligament reconstructed (ACLR) knee. The hypothesis was that the medial meniscus centralization would reduce extrusion and anterior laxity in ACLR knee with a medical meniscal defect. Fourteen fresh-frozen human cadaveric knees were tested using a six-degrees-of-freedom robotic system under the following loading conditions: (a) an 89.0N anterior tibial load, (b) 5.0 Nm internal and external rotational torques, (c) a 10.0Nm valgus and varus loadings, and (d) a combined 7.0Nm valgus moment and then a 5.0Nm internal rotation torque as a static simulated pivot shift. The tested knee states included: (1) anatomic single-bundle cruciate ligament reconstruction with intact medial meniscus (MM Intact), (2) anatomic single-bundle cruciate ligament reconstruction with medial meniscus posterior root defect (MM Defect), (3) Anatomic single-bundle cruciate ligament reconstruction with medial meniscus arthroscopic centralization (MM Centralization). Medial meniscus arthroscopic centralization was performed using 1.4mm anchors with #2 suture. The MM extrusion (MME) was measured using ultrasound under unloaded and varus loading conditions at 0° and 30° of flexion. Anterior tibial translation (ATT) increased significantly with MM posterior root defect compared to MM intact at all flexion angles. With MM centralization, ATT was not significantly different from the intact meniscus at 15° and 30° of flexion. Meniscus extrusion increased significantly with the root defect compared to intact meniscus and decreased significantly with meniscal centralization compared to the root defect at both flexion angles. In ACL reconstruction, cases involving irreparable medial meniscal posterior root tears, applying arthroscopic centralization for avoiding the meniscal extrusion should be considered. Clinically, in ACL reconstruction cases with irreparable medial meniscal posterior root tears, applying arthroscopic meniscal centralization for avoiding the meniscal extrusion should be considered. Meniscal centralization decreases the extrusion of the MM and offers improvements in knee laxity.

No Difference in Knee Kinematics Between Anterior Cruciate Ligament-First and Posterior Cruciate Ligament-First Fixation During Single-Stage Multiligament Knee Reconstruction: A Biomechanical Study.

Background:For combined reconstruction of both the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), there is no consensus regarding which graft should be tensioned and fixed first.Purpose:The purpose of this study was to determine which sequence of graft tensioning and fixation better restores normal knee kinematics. The hypothesis was that ACL-first fixation would more closely restore normal knee kinematics, graft force, and the tibiofemoral orientation in the neutral (resting) position compared with PCL-first fixation.Study Design:Controlled laboratory study.Methods:A total of 15 unpaired human cadaveric knees were examined using a robotic testing system under the following 4 conditions: (1) 89.0-N anterior tibial load at different knee angles; (2) 89.0-N posterior tibial load at different knee angles; (3) combined rotational 7.0-N·m valgus and 5.0-N·m internal rotation load (simulated pivot shift) at 0°, 15°, and 30° of flexion; and (4) 5.0-N·m external rotation load at 0°, 15°, and 30° of flexion. The 4 evaluated knee states were (1) intact ACL and PCL (intact), (2) ACL and PCL deficient (deficient), (3) combined anatomic ACL-PCL reconstruction fixing the ACL first (ACL-first), and (4) combined anatomic ACL-PCL reconstruction fixing the PCL first (PCL-first). A 9.0 mm–diameter quadriceps tendon autograft was used for the ACL graft, tensioned with 40.0 N at 30° of flexion. A 9.5 mm–diameter hamstring tendon autograft (gracilis and semitendinosus, quadrupled loop, and augmented with an additional allograft strand if needed), tensioned with 40.0 N at 90° of flexion, was used for the PCL graft.Results:There were no statistically significant differences between ACL-first and PCL-first fixation regarding knee kinematics. ACL-first fixation restored anterior tibial translation to the intact state at all tested knee angles, while PCL-first fixation showed higher anterior tibial translation than the intact state at 90° of flexion (9.05 ± 3.05 and 5.87 ± 2.40 mm, respectively; P = .018). Neither sequence restored posterior tibial translation to the intact state at 30°, 60°, and 90° of flexion. At 15° of flexion, PCL-first fixation restored posterior tibial translation to the intact state, whereas ACL-first fixation did not.Conclusion:There were no differences in knee laxity between ACL-first and PCL-first fixation with the ACL graft fixed at 30° and the PCL graft fixed at 90°.Clinical Relevance:This study showed that there was no evidence to support the use of one tensioning sequence over the other in single-stage multiligament knee reconstruction.

Remnant-Preserved Single-Bundle Anterior Cruciate Ligament Augmentation in Multi-ligamentous Knee Reconstruction.

This study was conducted to present remnant-preserving anterior cruciate ligament (ACL) augmentation as a useful option for partial ACL injury in multiligament knee injury (MLKI) cases, which may also contribute to conserving graft resources. The present study involved patients diagnosed with MLKI at our institute from Spring 2006 to February 2021. A total of 71 MLKI cases were provided surgery due to knee instability and disability. For every patient, an arthroscopic diagnostic was performed to ensure that ACL tear and a remnant were present. When the ACL remnant was classified into group 2, 3, or 4 of Nakamae's classification, remnant-preserved single bundle ACL augmentation was performed. Graft selection and the combination of injured ligaments were evaluated. The side-to-side difference under an anterior tibial load of 134 N with an arthrometer and the leg symmetry index at 60 degrees/s were measured. The present procedure was performed for five cases (male/female: 4/1, mean age: 33.6 years). The mean follow-up period was 26.4 months. The combination of torn ligaments was as follows: 3 cases of ACL + medial collateral ligament, one case of ACL + posterior cruciate ligament, and one case of ACL + posterolateral corner. An ACL augmentation graft was performed using an ipsilateral gracilis tendon in 2 cases, a contralateral full semitendinosus tendon in 2 cases, and the ipsilateral distal 1/2 of the semitendinosus tendon in 1 case. The mean side-to-side difference was 1.07 ± 0.4 mm. The mean leg symmetry index was 82.6 ± 12.2% in knee extension and 96.3 ± 9.9% in knee flexion. Although the present study was a small case series, the remnant-preserved single-bundle ACL augmentation for MLKI surgery provided good clinical outcome and conserved the graft resource. Even in the MLKI case, this technique is one of the useful surgical options. The level of evidence of this study is level IV (case series).

Biomechanical effects of cross-pin's diameter in reconstruction of anterior cruciate ligament – A specific case study via finite element analysis

For anterior cruciate ligament reconstruction (ACL-R), one of the crucial aspects of treatment is the fixator selection that could provide initial graft fixation post-operatively. Literature on biomechanical stabilities of different sizes of fixators as femoral graft fixation is limited. Therefore, this study aims to analyse the influence of different diameters of cross-pins on the stability of graft fixations after ACL-R via finite element analysis (FEA). In the methodology, three-dimensional (3D) models of three different diameters of cross-pins were developed, of which anterior tibial loads (ATL) were applied onto the tibia. From the findings, the cross-pin with a smaller diameter (4 mm) provided optimum stability than larger diameter cross-pins, whereby it demonstrated acceptable stresses at the fixators (both cross-pin and interference screw) with a different percentage of 28%, while the stresses at the corresponding bones were favourable for osseointegration to occur. Besides, the strains of the knee joint with 4 mm diameter cross-pin were also superior in providing a good biomechanical environment for bone healing, while the recorded strain values at fixators were comparable with a larger diameter of cross-pins without being inferior in terms of deformation. To conclude, the cross-pin with 4 mm diameter depicted the best biomechanical aspects in graft fixation for ACL-R since it allows better assistance for the osseointegration process and can minimise the possibility of the breakage and migration of fixators. This study is not only useful for medical surgeons to justify their choices of pin diameter to treat patients, but also for researchers to conduct future studies.

Sequential damage assessment of the posterolateral complex of the knee joint: a finite element study

BackgroundThe posterolateral complex (PLC), which consists of the popliteus tendon (PT), lateral collateral ligament (LCL), and popliteofibular ligament (PFL), is an indispensable structure of the knee joint. The aim of this study was to explore the functionality of the PLC by determining the specific role of each component in maintaining posterolateral knee stability.MethodsA finite element (FE) model was generated based on previous material property data and magnetic resonance imaging of a volunteer’s knee joint. The injury order of the PLC was set as LCL, PFL, and PT. A combined compressive load of 1150 N and an anterior tibial load of 134 N was applied to the tibia to investigate tibial displacement (TD). Tibial external rotation (TER) and tibial varus angulation (TVA) were measured under bending motions of 5 and 10 Nm. The instantaneous axis of rotation (IAR) of the knee joint under different rotation motions was also recorded.ResultsThe TD of the intact knee under a combined compressive load of 1150 N and an anterior tibial load of 134 N matched the values determined in previous studies. Our model showed consistent increases in TD, TVA, and TER after sequential damage of the PLC. In addition, sequential disruption caused the IAR to shift superiorly and laterally during varus rotation and medially and anteriorly during external rotation. In the dynamic damage of the PLC, LCL injury had the largest effect on TD, TVA, TER, and IAR.ConclusionsSequential injury of the PLC caused considerable loss of stability of the knee joint according to an FE model. The most significant structure of the PLC was the LCL.

Biomechanical Evaluation of Modified ACL Reconstruction with Over-the-Top Augmentation Technique.

Modified ACL reconstruction with over-the-top augmentation technique (OA-ACLR) was designed to allow one-stage revision regardless of tunnel conditions as well as to offer firm stability by hybrid double-fixation. Thus, the purpose of the study is to biomechanically evaluate its effect on knee stability by comparing it with single-bundle ACL reconstruction (SB-ACLR). Ten porcine knees were sequentially tested using a custom testing system for intact ACL, ACL deficiency, SB-ACLR and OA-ACLR. First, 134-N anterior tibial load was applied, and anterior tibial translation was measured at 30°, 60°, and 90°. Then, anterior tibial translation and relative tibial rotation were measured in a combined rotatory load of 5-Nm of internal tibial torque and 10-Nm of valgus torque. Under anterior tibial load or combined anterior and rotatory loads, SB-ACLR and OA-ACLR resulted in no significant increase in anterior tibial translation at all flexion angles compared with an intact ACL group, and no significant difference was noted in anterior tibial translation between the two ACL reconstruction groups. In combined rotatory load, OA-ACLR resulted in enhanced rotational stability compared with SB-ACLR, and it more closely restored relative tibial internal rotation to the intact ACL group. Our study showed that modified ACL reconstruction with over-the-top augmentation technique resulted in enhanced rotational stability compared to the conventional single-bundle ACL reconstruction, especially at lower flexion angle in a porcine model. Therefore, with several potential advantages as well as biomechanical superiority, our new technique could be clinically applicable in primary and revision ACL reconstruction. Experimental.

The Femoral Tunnel Drilling Angle at 45° Coronal and 45° Sagittal Provided the Lowest Peak Stress and Strain on the Bone Tunnels and Anterior Cruciate Ligament Graft.

Purpose: The aims of this study were to 1) investigate the effects of femoral drilling angle in coronal and sagittal planes on the stress and strain distribution around the femoral and tibial tunnel entrance and the stress distribution on the graft, following anterior cruciate ligament reconstruction (ACLR), 2) identify the optimal femoral drilling angle to reduce the risk of the tunnel enlargement and graft failure. Methods: A validated three-dimensional (3D) finite element model of a healthy right cadaveric knee was used to simulate an anatomic ACLR with the anteromedial (AM) portal technique. Combined loading of 103.0 N anterior tibial load, 7.5 Nm internal rotation moment, and 6.9 Nm valgus moment during normal human walking at joint flexion of 20° was applied to the ACLR knee models using different tunnel angles (30°/45°/60° and 45°/60° in the coronal and sagittal planes, respectively). The distribution of von Mises stress and strain around the tunnel entrances and the graft was calculated and compared among the different finite element ACLR models with varying femoral drilling angles. Results: With an increasing coronal obliquity drilling angle (30° to 60°), the peak stress and maximum strain on the femoral and tibial tunnel decreased from 30° to 45° and increased from 45° to 60°, respectively. With an increasing sagittal obliquity drilling angle (45° to 60°), the peak stress and the maximum strain on the bone tunnels increased. The lowest peak stress and maximum strain at the ACL tunnels were observed at 45° coronal/45° sagittal drilling angle (7.5 MPa and 7,568.3 μ-strain at the femoral tunnel entrance, and 4.0 MPa and 4,128.7 μ-strain at the tibial tunnel entrance). The lowest peak stress on the ACL graft occurred at 45° coronal/45° sagittal (27.8 MPa) drilling angle. Conclusions: The femoral tunnel drilling angle could affect both the stress and strain distribution on the femoral tunnel, tibial tunnel, and graft. A femoral tunnel drilling angle of 45° coronal/ 45° sagittal demonstrated the lowest peak stress, maximum strain on the femoral and tibial tunnel entrance, and the lowest peak stress on the ACL graft.

Sex-specific biomechanics and morphology of the anterior cruciate ligament during skeletal growth in a porcine model.

Pediatric anterior cruciate ligament (ACL) injuries are on the rise, and females experience higher ACL injury risk than males during adolescence. Studies in skeletally immature patients indicate differences in ACL size and joint laxity between males and females after the onset of adolescence. However, functional data regarding the ACL and its anteromedial and posterolateral bundles in the pediatric population remain rare. Therefore, this study uses a porcine model to investigate the sex-specific morphology and biomechanics of the ACL and its bundles throughout skeletal growth. Hind limbs from male and female Yorkshire pigs aged early youth to late adolescence were imaged using magnetic resonance imaging to measure the size and orientation of the ACL and its bundles, then biomechanically tested under anterior-posterior drawer using a robotic testing system. Joint laxity decreased (p < 0.001) while joint stiffness increased (p < 0.001) throughout skeletal growth in both sexes. The ACL was the primary stabilizer against anterior tibial loading, while the functional role of the anteromedial bundle increased with age (p < 0.001), with an earlier increase in males. ACL and posterolateral bundle cross-sectional area and ACL and anteromedial bundle length were larger in males than females during adolescence (p < 0.01 for all), while ACL and bundle sagittal angle remained similar between sexes. Additionally, in situ ACL stiffness versus cross-sectional area regressions were significant across skeletal growth (r2 = 0.75, p < 0.001 in males and r2 = 0.64, p < 0.001 in females), but not within age groups. This study has implications for age and sex-specific surgical intervention strategies and suggests the need for human studies.

Tibiofemoral bony morphology impacts the knee kinematics after anterolateral capsule injury and lateral extraarticular tenodesis differently than intact state

Anterolateral capsule injury, often concomitant with anterior cruciate ligament (ACL) injuries, may result in high-grade rotatory instability. Lateral extraarticular tenodesis (LET) is sometimes added to ACL reconstruction to address this instability. However, LET is a non-anatomic procedure and concerns regarding increased tibiofemoral contact pressure and reduced internal rotation exist for some individuals which may be due to their tibiofemoral bony morphology. Therefore, the objective of this study was to analyze the effect of bony morphology on knee kinematic and contact pressure before and after anterolateral capsule injury and LET. A (1) 134-N anterior tibial load with 200-N axial compression and (2) a 7-Nm internal torque with a 200-N axial compression were applied to cadaveric knees (n = 8) using a 6 degree-of-freedom robotic testing system. Tibiofemoral bony morphology was captured with computed tomography scans and analyzed using 3D statistical shape modeling. Kinematics at each state were correlated with the results from the statistical shape model. Two femoral and three tibial modes of variation correlated with kinematic and contact pressure data before and after anterolateral capsule injury and LET. A decreased lateral tibial plateau elevation correlated with greater internal rotation and anterior tibial translation after anterolateral capsule deficiency and LET. Decreased notch width correlated with decreased contact area after anterolateral capsule deficiency and LET demonstrating it as a risk factor for ACL injury. The results of this study demonstrate that bony morphology if properly understood, could help improve the efficacy of LET procedures and that bony morphology has different effects after injury and repair.

Arthroscopic Centralization for Lateral Meniscal Injuries Reduces Laxity in the Anterior Cruciate Ligament–Reconstructed Knee

Background: A lateral meniscal (LM) disorder is one factor that causes rotational laxity after anterior cruciate ligament (ACL) reconstruction (ACLR). There are different types of irreparable meniscal disorders, one of which is a massive meniscal defect. Hypothesis/Purpose: The purpose of this study was to evaluate the kinematic effects of arthroscopic centralization on an irreparable LM defect. The hypothesis was that arthroscopic centralization for an irreparable LM defect with concomitant ACLR would improve knee rotational stability. Study Design: Controlled laboratory study. Methods: A total of 14 fresh-frozen human cadaveric knees were tested in 4 states: (1) intact ACL and intact lateral meniscus, (2) reconstructed ACL and intact lateral meniscus, (3) reconstructed ACL and lateral meniscus defect, and (4) reconstructed ACL and centralized lateral meniscus. Anatomic ACLR was performed using an 8 mm–diameter hamstring tendon graft. An LM defect (20% of the anteroposterior length) was created arthroscopically, and arthroscopic centralization was performed. Kinematics were analyzed using a 6 degrees of freedom robotic system under 4 knee loads: (1) an 89.0-N anterior tibial load, (2) a 5.0-N·m external rotation tibial torque, (3) a 5.0-N·m internal rotation tibial torque, and (4) a simulated pivot-shift load with a combined 7.0-N·m valgus and 5.0-N·m internal rotation tibial torque. Results: LM centralization reduced anterior tibial translation similar to that of the ACLR intact LM state under anterior tibial loading (~2 mm at 30° of flexion) and showed 40% to 100% of tibial displacement in the 4 knee states under simulated pivot-shift loading. The procedure overconstrained the knee under internal rotation tibial torque and simulated pivot-shift loading. Conclusion: Arthroscopic centralization reduced knee laxity after ACLR for a massive LM defect in a cadaveric model. Clinical Relevance: In cases involving irreparable LM injuries during ACLR, consideration should be given to arthroscopic centralization for reducing knee laxity. However, the procedure may overconstrain the knee in certain motions.