Ligament Bundles Research Articles

Using Video-Fluoroscopy and Multibody Modelling to Unveil the Influence of a Gradually Reducing Femoral Radius on Ligament Elongation Patterns Following Posterior Cruciate-Retaining Total Knee Arthroplasty

Stability in total knee arthroplasties (TKAs) is mainly provided by soft tissue structures and the implant geometry. Paradoxical anterior translation could be decreased with a gradually reducing femoral radius compared to a dual-radii design. However, the influence of the sagittal curvature of the femoral condyles on knee ligaments remains unclear. This study quantified the length change patterns of the medial and lateral collateral ligaments (MCL and LCL) and posterior cruciate ligament (PCL) in 15 subjects with a gradually reducing radius and 15 subjects with a dual-radii TKA. Kinematics obtained from video-fluoroscopy were used to drive personalised multibody knee models. The ligament lengths were analysed throughout complete cycles of level gait, stair descent, and sit-to-stand-to-sit activity. Regardless of the implant design, our results indicated flexion-dependent elongation patterns in all ligament bundles. Importantly, however, subjects with the dual-radii implant design exhibited higher ligament strains during the mid-flexion phase compared to those with gradually reducing designs. Our findings, therefore, emphasise the importance of the impact of subtle changes in implant geometry on the loading patterns of the knee soft tissues, which need to be acknowledged by implant manufacturers and orthopaedic surgeons.

Ex vivo evaluation of the soft tissue components of the equine stifle using 3 Tesla magnetic resonance imaging under flexion, extension, and loading.

High-field MRI of the equine stifle provides high-resolution information about soft tissues that is useful in the diagnosis of stifle lameness. The aim of this prospective anatomic study was to describe the appearance, position, size, and shape of the equine femorotibial ligaments, meniscal ligaments, and menisci using 3 Tesla MRI under extended, extended-loaded, and flexed conditions. Additionally, histologic examination of the collateral and cruciate ligaments (CLs) of a single stifle was performed to compare with MRI images. In extension, mild variations in MRI signal intensity were apparent in the CLs, and the cranial had two distinct longitudinal regions indicating two ligament bundles. Flexion had minor effects on CL signal intensity and altered the tibial angles of attachment. Histology indicated that both CLs were comprised of two fiber bundles. The collateral ligaments were the same low-signal intensity. The medial collateral ligament had a smaller cross-sectional area than the lateral, and flexion increased the length of the medial collateral ligament and the cross-sectional area of the lateral. Low loads in extension did not affect the MRI appearance of stifle soft tissues. Flexion of the stifle impacted cruciate ligament insertion angles and the size and shape of collateral ligaments. This study provides support for the use of MRI to understand the anatomy and function of stifle ligaments.

DIRECT POSTERIOR KNEE PORTALS USING NEEDLE ARTHROSCOPY: A TECHNICAL FEASIBILITY STUDY

Knee arthroscopy is typically approached from the anterior, posteromedial and posterolateral portals. Access to the posterior compartments through these portals can cause iatrogenic cartilage damage and create difficulties in viewing the structures of the posterior compartments. The purpose of this study was to assess the feasibility of needle arthroscopy using direct posterior portals as both working and visualising portals.For workability, the needle scope was inserted advanced from anterior between the cruciate ligament bundle and the lateral wall of the medial femoral condyle until the posterior compartments were visualised. For visualisation, direct postero-lateral and -medial portals were established. The technique was performed in 9 knees by two experienced researchers.Workability and instrumentation of the posteromedial compartment and meniscus was achieved in 56%. The posterior horns could not be visualised in four specimens as the straight lens could not provide a more medial field of view. Visualisation from the direct medial posterior portal allowed a clear view of the medial meniscus, femoral condyle and posterior cruciate ligament in all specimens. Workability and instrumentation of the posterolateral compartment was not possible with the needle scope.Direct posterior approaches for the posteromedial compartment access are challenging with the current needle scope options and could only be achieved in over 50%. The postero-lateral compartment was not accessible. An angled lens or a flexible Needle scope would be better suited for developing this technique further.

The Specific Anatomical Morphology of Lateral Ankle Ligament: Qualitative and Quantitative Cadaveric based Study.

The accurate understanding in morphological features of the lateral ankle ligaments is necessary for the diagnosis and management of ankle instability and other ankle problems. The purpose of this study was to evaluate the anatomical morphology and the attachment areas of lateral ligament complex of ankle joint based on the cadaveric study. Fifty-four fresh frozen cadaveric ankles were dissected to evaluate the lateral ankle ligaments. Each ligament was separated into two or three small bundles. In the investigated footprint areas, acrylic colors were used as a marker point to locate specific areas of ligament bundle attached to the bone. The Image J software was used to measure and analyze the sizes of the specific footprint areas to achieve descriptive statistical analysis. The double bands of anterior talofibular ligament (ATFL) were found as a major type in the present study with 57.41% (31 of 54 ankles) while the single band of ATFL was observed in 42.59% (23 of 54 ankles). The attachment sizes of the ATFL, posterior talofibular ligament (PTFL) and calcaneofibular ligament (CFL) were evaluated into two areas; proximal and distal attachments. The average of proximal or fibular part of ATFL, PTFL and CFL were 85.06, 134.27, 93.91 mm2 respectively. The average of distal part of ATFL, PTFL and CFL were 100.07, 277.61, 249.39 mm2 respectively. Considering the lateral ankle ligament repaired or reconstruction especially using arthroscopy, the precise understanding in specific detail of the lateral ankle ligament may help both diagnose and select the appropriate treatment for solving the ankle problems. These observations may help the surgeon to perform the surgical procedure for determining the appropriate techniques and avoid complication to patients.

Medial stability and lateral flexibility of the collateral ligaments during mid-range flexion in medial-pivot total knee arthroplasty patients demonstrates favorable postoperative outcomes.

The objectives of the present study were to investigate the length change in different bundles of the superficial medial collateral ligament (sMCL) and lateral collateral ligament (LCL) during lunge, and to evaluate their association with Knee Society Score (KSS) following medial-pivot total knee arthroplasty (MP-TKA). Patients with unilateral MP-TKA knees performed a bilateral single-leg lunge under dual fluoroscopy surveillance to determine the in-vivo six degrees-of-freedom knee kinematics. The contralateral non-operated knees were used as the control group. The attachment sites of the sMCL and LCL were marked to calculate the 3D wrapping length. The sMCL and LCL were divided into anterior, intermediate, and posterior portions (aMCL, iMCL, pMCL, aLCL, iLCL, pLCL). Correlations between lengths/elongation rate of ligament bundles from full extension to 100° flexion and the KSS were examined. The sMCL and LCL demonstrated relative stability in length at low flexion, but sMCL length decreased whereas LCL increased with further flexion on operated knees. The sMCL length increased at low flexion and remained stable with further flexion, while the LCL length decreased with flexion on the contralateral non-operated knees. The lengths of aMCL, iMCL, and pMCL showed moderate (0.5 < r < 0.7, p < 0.05) negative correlations with the KSS, and the lengths of aLCL, iLCL, and pLCL were positively correlated with the KSS at mid flexion on operated knees (p < 0.05). The elongation rates of aLCL, iLCL, and pLCL were negatively correlated with the KSS at high flexion on operated knees (p < 0.05). However, no significant correlations between the length of different bundles of sMCL or LCL with KSS were found on contralateral non-operated knees. The elongation pattern of sMCL/LCL on MP-TKA knees showed differences with contralateral non-operated knees. The sMCL is tense at low to middle flexion and relaxed at high flexion, while LCL is relaxed at low to middle flexion and tense at high flexion following MP-TKA. Medial stability and proper lateral flexibility during mid flexion were associated with favorable postoperative outcomes in MP-TKA patients. In contrast, lateral relaxation at deep flexion should be avoided when applying soft-tissue balancing in MP-TKA. Level III.

An atypical anatomical variation of the petrosphenoidal ligament in a newborn cadaver.

To report an atypical anatomical variation of the petrosphenoidal ligament in a newborn cadaver and to discuss its clinical significance. During a study of ten newborn cadavers, the skull base was dissected to reveal the anatomy of the petrosphenoidal ligament and its relationship with the abducens nerve. An atypical anatomical variation was observed, and this is described. The length of the right and left ligaments to the point where it splits into two arms, the joint length of the two ligaments at the junction of the clivus, the length of the ligament proceeding to the posterior clinoid process, and the abducens nerve's diameter as it passes below the ligament were measured on ImageJ software. The petrosphenoidal ligaments were y-shaped, and the attachment of the proximal ligaments was bifid. In the midline above the clivus, some ligament bundles joined the contralateral petrosphenoidal ligament, whilst another group of bundles originated at the posterior clinoid process. At the entry to Dorello's canal, the abducens nerve had a diameter of 0.59mm on the left and 0.65mm on the right. The part of the ligaments converging on the clivus in the midline after dividing into two arms was 10.68mm. We think that this case report will provide useful information for surgical procedures to the petroclival region, transnasal surgical approaches, and surgical interventions involving the carotid artery.

Methodology to identify optimal subject-specific laxity tests to stretch individual parts of knee ligaments.

Laxity tests are performed to diagnose ligament injuries or to estimate subject-specific ligament properties. While the current laxity tests are easy to perform, they are not optimized to isolate specific ligament bundles. Therefore, we developed a methodology to identify optimal laxity tests to either stretch specific ligaments relatively more than other ligaments or maximally stretch a specific ligament within the boundaries of maximally applied loads to the knee. The method was applied to a subject-specific knee model and the identified optimal laxity tests compared against standard tests. For the laxity tests isolating the stretch in a specific ligament, we found laxity tests that performed better for all ligament bundles except a few where neither the optimal nor standard laxity tests could isolate the ligament. We found force ratios, between the force change in the ligament of interest compared to the maximal force change in the other ligaments, of over 2.0 for six ligament bundles with the optimized load cases whereas the standard laxity tests only resulted in one bundle over 2.0. For the tests to maximally load the ligament of interest, increased force changes were seen for all optimal load cases and force changes of over 200 N were seen for six ligament bundles whereas only one bundle had a force change over 200N with the standard laxity tests. Our results show that there is a potential to develop better laxity tests than those performed today and emerging laxity test equipment enable implementation of such tests.

Load Bearing Simulation of Knee Ligament Fiber Bundles Attachment States

In this study, we developed a knee simulation model considering the attachment area of the knee joint cruciate ligament bundles. 3D geometry extraction of the femur, tibia, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) from CT images of the knee joint. In addition, the stress-strain curves of ligaments were derived from uniaxial tensile tests. A finite element analysis model of the knee joint was created based on the above conditions. The state of ligament bundle attachment was reproduced by dividing the attachment area of the ACL and PCL to the femur and tibia. As a result, although the behavior of the ligament during compression remained to be an issue, similar tendencies to those of ligament desmotomy studies were obtained.

Ideal Combination of Anatomic Tibial and Femoral Tunnel Positions for Single-Bundle ACL Reconstruction.

Background:Anatomic anterior cruciate ligament reconstruction (ACLR) is preferred over nonanatomic ACLR. However, there is no consensus on which point the tunnels should be positioned among the broad anatomic footprints.Purpose/Hypothesis:To identify the ideal combination of tibial and femoral tunnel positions according to the femoral and tibial footprints of the anteromedial (AM) and posterolateral (PL) anterior cruciate ligament bundles. It was hypothesized that patients with anteromedially positioned tunnels would have better clinical scores, knee joint stability, and graft signal intensity on follow-up magnetic resonance imaging (MRI) than those with posterolaterally positioned tunnels.Study Design:Cohort study; Level of evidence, 3.Methods:A total of 119 patients who underwent isolated single-bundle ACLR with a hamstring autograft from July 2013 to September 2018 were retrospectively investigated. Included were patients with clinical scores and knee joint stability test results at 2-year follow-up and postoperative 3-dimensional computed tomography and 1-year postoperative MRI findings. The cohort was divided into 4 groups, named according to the bundle positions in the tibial and femoral tunnels: AM-AM (n = 33), AM-PL (n = 26), PL-AM (n = 29), and PL-PL (n = 31).Results:There were no statistically significant differences among the 4 groups in preoperative demographic data or postoperative clinical scores (Lysholm, Tegner, and International Knee Documentation Committee subjective scores); knee joint stability (anterior drawer, Lachman, and pivot-shift tests and Telos stress radiographic measurement of the side-to-side difference in anterior tibial translation); graft signal intensity on follow-up MRI; or graft failure.Conclusion:No significant differences in clinical scores, knee joint stability, or graft signal intensity on follow-up MRI were identified between the patients with anteromedially and posterolaterally positioned tunnels.

Constitutive modeling of the anterior cruciate ligament bundles and patellar tendon with full-field methods

Anterior cruciate ligament (ACL) injury rates are rising, and there is little consensus about what puts someone at risk for an ACL injury. Finite element models provide an effective platform for systemically determining the effect of possible injury risk factors on ACL strain concentrations. However, the accuracy of a finite element model relies on the accuracy of the material models used in its construction. Standard material characterization methods require an assumption of both deformation and material homogeneity, but our recent work has demonstrated that structural features like the shape of the ligament–bone attachment (enthesis) and collagen fiber splay (material direction heterogeneity) create unavoidable deformation heterogeneity. Hence, in this study, full-volume, full-field, finite deformation methods were used to build material models for the ovine ACL bundles and patellar tendon. Specifically, displacement-encoded magnetic resonance imaging (MRI) was used to measure five full-volume deformation fields of each ligament (n=5 specimens of each) under tension, and the virtual fields method (VFM) was used to determine material model parameters with these data. This method accounts for strain heterogeneity, principal material direction heterogeneity (fiber splay), and enthesis shape. While most constitutive parameters were consistent among all specimen groups, parameters describing the degree of anisotropy, or collagen fiber alignment, showed statistically significant differences between groups. This work demonstrates that (when strain heterogeneity and structural properties are accounted for) ligament material properties are deterministic and ligament material microstructure is detectable with mesoscale measures of mechanical function.

Epicardial ablation of recurrent left atrial macroreentrant tachycardia from Bachmann's bundle region after endocardial ablation

Bachmann's bundle is a common site of possible epicardial connection in addition to coronary sinus, Marshall ligament and septopulmonary bundle. Hereby, we presented the image of epicardial ablation for recurrent perimitral macroreentry after endocardial ablation. Endocardial mapping revealed discontinuous activation pattern. Epicardial mapping demonstrated highly fragmented signals at the opposite site of presumed endocardial isthmus. Epicardial mapping and ablation may improve procedural success in selected patients with accurate definition of reentrant circuit despite effective endocardial lesion formation. This article is protected by copyright. All rights reserved.

WraptMor: Confirmation of an Approach to Estimate Ligament Fiber Length and Reactions With Knee-Specific Morphology.

Knee ligament length can be used to infer ligament recruitment during functional activities and subject-specific morphology affects the interplay between ligament recruitment and joint motion. This study presents an approach that estimated ligament fiber insertion-to-insertion lengths with wrapping around subject-specific osseous morphology (WraptMor). This represents an advancement over previous work that utilized surrogate geometry to approximate ligament interaction with bone surfaces. Additionally, the reactions each ligament imparted onto bones were calculated by assigning a force-length relationship (kinetic WraptMor model), which assumed that the insertion-to-insertion lengths were independent of the assigned properties. Confirmation of the approach included comparing WraptMor predicted insertion-to-insertion length and reactions with an equivalent displacement-controlled explicit finite element model. Both models evaluated 10 ligament bundles at 16 different joint positions, which were repeated for five different ligament prestrain values for a total of 80 simulations per bundle. The WraptMor and kinetic WraptMor models yielded length and reaction predictions that were similar to the equivalent finite element model. With a few exceptions, predicted ligament lengths and reactions agreed to within 0.1 mm and 2.0 N, respectively, across all tested joint positions and prestrain values. The primary source of discrepancy between the models appeared to be caused by artifacts in the finite element model. The result is a relatively efficient approach to estimate ligament lengths and reactions that include wrapping around knee-specific bone surfaces.

In Vivo Elongation Patterns of the Collateral Ligaments in Healthy Knees During Functional Activities.

Improved knowledge of in vivo function of the collateral ligaments is essential for enhancing rehabilitation and guiding surgical reconstruction as well as soft-tissue balancing in total knee arthroplasty. The aim of this study was to quantify in vivo elongation patterns of the collateral ligaments throughout complete cycles of functional activities. Knee kinematics were measured using radiographic images captured with a mobile fluoroscope while healthy subjects performed level walking, downhill walking, and stair descent. The registered in vivo tibiofemoral kinematics were then used to drive subject-specific multibody knee models to track collateral ligament elongation. The elongation patterns of the medial collateral ligament varied distinctly among its bundles, ranging from lengthening of the anterior fibers to shortening of the posterior bundle with increases in the knee flexion angle. The elongation patterns of the lateral collateral ligament varied considerably among subjects. It showed an average 4% shortening with increasing flexion until 60% to 70% of the gait cycle, and then recovered during the terminal-swing phase until reaching its reference length (defined at heel strike). The observed nonuniform elongation of the medial collateral ligament bundles suggests that single-bundle reconstruction techniques may not fully restore healthy ligament function. Moreover, the observed ligament elongation patterns indicate greater varus than valgus laxity in the loaded knee. Through providing key knowledge about the in vivo elongation patterns of the collateral ligaments throughout complete cycles of functional activities, this study offers in vivo evidence for benchmarking ligament reconstruction and soft-tissue balancing in total knee arthroplasty.

In vivo kinematics and cruciate ligament forces in bicruciate-retaining total knee arthroplasty

We analyzed the effects of bicruciate-retaining total knee arthroplasty (BCR-TKA) on knee kinematics and cruciate ligament forces. Patients (N = 15) with osteoarthritis (OA) and an intact anterior cruciate ligament (ACL) underwent magnetic resonance imaging and single-plane fluoroscopy to measure tibiofemoral kinematics during two deep knee bend activities before and after BCR-TKA: (1) weight-bearing squat; (2) non-weight-bearing cross-legged sitting. Forces in ligament bundles were calculated using VivoSim. The dynamic range of varus-valgus angulation decreased from 3.9 ± 4.4° preoperatively to 2.2 ± 2.7° postoperatively. Preoperatively, the medial femoral condyle translated anteriorly from 10° to 50° of flexion, and posteriorly beyond 50° of flexion. Postoperatively, the medial and lateral femoral condyles translated posteriorly throughout flexion in a medial pivot pattern. ACL forces were high in extension and decreased with flexion pre- and postoperatively. PCL forces increased with flexion preoperatively and did not change significantly postoperatively. Preoperatively, ACL forces correlated with anteroposterior translation of the femoral condyles. Postoperatively, PCL forces correlated with anteroposterior translation of the lateral femoral condyle. BCR-TKA altered knee kinematics during high flexion activity which correlated significantly with changes in cruciate ligament forces.

Anatomical study of the proximal tibiofibular ligaments using ultrasound

ObjectivesNo description of the proximal tibiofibular (PTF) ligaments by means of high ultrasound has yet been reported in the literature. The purpose of this study was to assess whether ultrasound may allow the assessment of these ligaments.MethodsThis study was initially undertaken in three cadaveric knees, followed by an ultrasound study performed by two musculoskeletal radiologists working in consensus of 52 patients without history of trauma or surgery of the knee, and without lateral knee pain. The visibility, echogenicity, length and thickness of the PTF ligaments were assessed.ResultsRegarding the anterior PTF ligament, the superior bundle and the upper and lower middle bundles were clearly seen in 42.3%, 100% and 75% of the knees, respectively. Regarding the posterior PTF ligament, the superior and middle bundles were clearly seen in 88.4% and 51.9% of the knees, respectively. The echo-anatomy of these ligaments and the probe positioning allowing their best depiction were described in this study.ConclusionMost of the PTF ligaments can be visualized by means of ultrasound. This possible assessment may have clinical applications, particularly in patients with lateral knee pain.

Reconsidering Reciprocal Fundation of Anterior Cruciate Ligament Bundles During In Vivo Gait

Some cadaveric studies have indicated that the anterior cruciate ligament (ACL) consists of anteromedial (AM) and posterolateral (PL) bundles that function reciprocally with motion. However, several in vivo imaging studies have indicated that ACL subdivisions elongate during knee extension. Whether the ACL is a single structure or consists of different bundles with distinct function is debated. We hypothesized that both the AM and PL ACL subdivisions would undergo relative elongation with knee extension during gait. In 6 healthy subjects, 3D models of the femur, tibia and associated ACL attachment sites were created via segmentation of magnetic resonance (MR) images. The footprints of the AM and PL bundles were estimated and the bone models were registered to high-speed biplanar radiographs in order to reproduce the in vivo positions of the knee throughout gait. The overall length of the ACL was measured as the distance between ACL attachment site footprint centroids for each knee position. 1000 simulated ACL bundles were generated for each subject by randomly sampling locations on the ACL attachment site surfaces, and measuring the distances between each pair of locations. Spearman rho rank correlations were used to determine relationships between simulated bundle lengths and the overall ACL lengths in flexion and extension. Simulated bundle lengths and overall ACL length were highly correlated (rho = 0.91±0.04, mean±standard deviation across subjects, P < 5×10-5, Figure 1). The lengths of the bundles that originated and terminated in the AM footprints were positively correlated (rho=0.81±0.09, P < 5×10-5) with the lengths of the bundles that originated and terminated in the PL footprints. Lengths of all ACL subdivisions were highly positively correlated with overall ACL length throughout gait, suggesting absence of reciprocal bundle function.

Knee biomechanics during squat rising with patella alta and after distal transfer of tibial tubercular surgery

Patella alta has commonly seen in prior adolescent cerebral palsy population with crouch gait pattern. Unfortunately, for the treatments of PA and crouch gait, the outcomes of physical therapy, orthotic and surgical treatments are highly questionable. The purpose of this study is to investigate the effects of patella alta on knee biomechanics and to analyze the benefits of distal transfer of tibial tubercule (DTTT) during dual limb knee squat extension. A three-dimensional dynamic knee model comprising patellofemoral and tibiofemoral joints was developed. Patellar tendon length was increased 25% and 50% of its original length to simulate the patology. Tibiofemoral and patellofemoral contact forces, loads on ligament bundles, tibial rotations and quadriceps efficiencies were compared for patology, normal and after DTTT surgery (DTTTS). The results showed that patella alta, increases the tibiofemoral and patellofemoral compressive force, alters the neutral tension of ligament bundles, reduces the medio-lateral knee stability and increases the efficiency of the quadriceps muscle during squat rising. Even though DTTTS normalized some of the biomechanical alterations, internal rotation in higher flexion angles, valgus-varus rotation of the tibia and the tension of aACL and PCL remained different than normal. These alterations may play a contributory role to develop cartilage degeneration on tibiofemoral and patellofermoral joints. Inadequate quadriceps force and abnormal loading pattern on some of the ligaments may also contribute to the recurrence mechanism of crouch gait after DTTTS surgery.

In Vivo Mechanical Function of the Distal Radial Ulnar Ligaments During Rotation of the Wrist

The purpose of this study was to investigate changes in length of the volar and dorsal radioulnar ligaments (VRULs and DRULs), and the distal radioulnar joint (DRUJ) space during unweighted and weighted rotation of the wrist using magnetic resonance imaging and biplanar fluoroscopy. Fourteen wrists in 7 normal adult volunteers were imaged to define the 3-dimensional geometry of the DRUJ and the insertion sites of the superficial and deep bundles of the VRULs and DRULs. Subjects were imaged at 10 positions of forearm rotation ranging from full pronation to full supination, with or without a 5-pound weight. Lengths of the superficial and deep VRUL and DRUL bundles and DRUJ space were measured (in millimeters) at each position to evaluate ligament function and DRUJ stability. In the unweighted and weighted trials, maximal elongation of both deep and superficial VRUL bundles occurred in supination and maximal lengths of the deep and superficial DRUL bundles occurred in pronation. Maximum DRUJ space occurred during pronation and a minimum occurred in 30° of supination. In weighted trials, there was a significant increase in deep and superficial VRUL bundle length at positions between 30° of pronation and 30° of supination; however, there was no effect of weight on DRULs length. In weighted trials, there was a significant increase in DRUJ space at positions between full pronation and 15° of supination. This study demonstrates elongation of the VRULs in supination and the DRULs in pronation. There was no evidence of reciprocal loading of superficial/deep ligament bundles on either the dorsal or the volar aspects of the DRUJ. The effect of loading the wrist during rotation was apparent primarily in the VRULs, but not the DRULs. The DRUJ space was lowest at approximately 30° of supination. These results add information to the literature regarding the complicated biomechanics of the triangular fibrocartilage complex and DRUJ. Future work should evaluate changes in biomechanics caused by triangular fibrocartilage complex tears to determine how tear severity and location relate to clinical symptoms.

Elongation Patterns of the Posterior Cruciate Ligament after Total Knee Arthroplasty.

This study aimed to understand the ability of fixed-bearing posterior cruciate ligament (PCL)-retaining implants to maintain functionality of the PCL in vivo. To achieve this, elongation of the PCL was examined in six subjects with good clinical and functional outcomes using 3D kinematics reconstructed from video-fluoroscopy, together with multibody modelling of the knee. Here, length-change patterns of the ligament bundles were tracked throughout complete cycles of level walking and stair descent. Throughout both activities, elongation of the anterolateral bundle exhibited a flexion-dependent pattern with more stretching during swing than stance phase (e.g., at 40° flexion, anterolateral bundle experienced 3.9% strain during stance and 9.1% during swing phase of stair descent). The posteromedial bundle remained shorter than its reference length (defined at heel strike of the level gait cycle) during both activities. Compared with loading patterns of the healthy ligament, postoperative elongation patterns indicate a slackening of the ligament at early flexion followed by peak ligament lengths at considerably smaller flexion angles. The reported data provide a novel insight into in vivo PCL function during activities of daily living that has not been captured previously. The findings support previous investigations reporting difficulties in achieving a balanced tension in the retained PCL.

Anterior cruciate ligament bundle insertions vary between ACL-rupture and non-injured knees.

The present study aimed to investigate the three-dimensional topographic anatomy of the anterior cruciate ligament (ACL) bundle attachment in both ACL-rupture and ACL-intact patients who suffered a noncontact knee injury and identify potential differences. Magnetic resonance images of 90 ACL-rupture knees and 90 matched ACL-intact knees, who suffered a noncontact knee injury, were used to create 3D ACL insertion models. In the ACL-rupture knees, the femoral origin of the anteromedial (AM) bundle was 24.5 ± 9.0% posterior and 45.5 ± 10.5% proximal to the flexion-extension axis (FEA), whereas the posterolateral (PL) bundle origin was 35.5 ± 12.5% posterior and 22.4 ± 10.3% distal to the FEA. In ACL-rupture knees, the tibial insertion of the AM-bundle was 34.3 ± 4.6% of the tibial plateau depth and 50.7 ± 3.5% of the tibial plateau width, whereas the PL-bundle insertion was 47.5 ± 4.1% of the tibial plateau depth and 56.9 ± 3.4% of the tibial plateau width. In ACL-intact knees, the origin of the AM-bundle was 17.5 ± 9.1% posterior (p < 0.01) and 42.3 ± 10.5% proximal (n.s.) to the FEA, whereas the PL-bundle origin was 32.1 ± 11.1% posterior (n.s.) and 16.3 ± 9.4% distal (p < 0.01) to the FEA. In ACL-intact knees, the insertion of the AM-bundle was 34.4 ± 6.6% of the tibial plateau depth (n.s.) and 48.1 ± 4.6% of the tibial plateau width (n.s.), whereas the PL-bundle insertion was 42.7 ± 5.4% of the tibial plateau depth (p < 0.01) and 57.1 ± 4.8% of the tibial plateau width (n.s.). The current study revealed variations in the three-dimensional topographic anatomy of the native ACL between ACL-rupture and ACL-intact knees, which might help surgeons who perform anatomical double-bundle reconstruction surgery. III.