Analysis of stress response distribution in patients with lateral ankle ligament injuries: a study of neural control strategies utilizing predictive computing models.

Background: Ankle sprains are prevalent in sports, often causing complex injuries to the lateral ligaments. Among these, anterior talofibular ligament (ATFL) injuries constitute 85%, and calcaneofibular ligament (CFL) injuries comprise 35%. Despite conservative treatment, some ankle sprain patients develop chronic lateral ankle instability (CLAI). Thus, this study aimed to investigate stress response and neural control alterations during landing in lateral ankle ligament injury patients. Method: This study recruited twenty individuals from a Healthy group and twenty CLAI patients performed a landing task using relevant instruments to collect biomechanical data. The study constructed a finite element (FE) foot model to examine stress responses in the presence of laxity of the lateral ankle ligaments. The lateral ankle ligament was modeled as a hyperelastic composite structure with a refined representation of collagen bundles and ligament laxity was simulated by adjusting material parameters. Finally, the validity of the finite element model is verified by a high-speed dual fluoroscopic imaging system (DFIS). Result: CLAI patients exhibited earlier Vastus medialis (p < 0.001) and tibialis anterior (p < 0.001) muscle activation during landing. The FE analysis revealed that with laxity in the ATFL, the peak von Mises stress in the fifth metatarsal was 20.74 MPa, while with laxity in the CFL, it was 17.52 MPa. However, when both ligaments were relaxed simultaneously, the peak von Mises stress surged to 21.93 MPa. When the ATFL exhibits laxity, the CFL is subjected to a higher stress of 3.84 MPa. Conversely, when the CFL displays laxity, the ATFL experiences a peak von Mises stress of 2.34 MPa. Conclusion: This study found that changes in the laxity of the ATFL and the CFL are linked to shifts in metatarsal stress levels, potentially affecting ankle joint stability. These alterations may contribute to the progression towards CLAI in individuals with posterolateral ankle ligament injuries. Additionally, significant muscle activation pattern changes were observed in CLAI patients, suggesting altered neural control strategies post-ankle ligament injury.

Strain imaging of the lateral collateral ligament using high frequency and conventional ultrasound imaging: An ex-vivo comparison.

Recent first attempts of in situ ultrasound strain imaging in collateral ligaments encountered a number of challenges and illustrated a clear need for additional studies and more thorough validation of the available strain imaging methods. Therefore, in this study we experimentally validated ultrasound strain measurements of ex vivo human lateral collateral ligaments in an axial loading condition. Moreover, the use of high frequency ultrasound (>20 MHz) for strain measurement was explored and its performance compared to conventional ultrasound. The ligaments were stretched up to 5% strain and ultrasound measurements were compared to surface strain measurements from optical digital image correlation (DIC) techniques. The results show good correlations between ultrasound based and DIC based strain measures with R2 values of 0.71 and 0.93 for high frequency and conventional ultrasound, subsequently. The performance of conventional ultrasound was significantly higher compared to high frequency ultrasound strain imaging, as the high frequency based method seemed more prone to errors. This study demonstrates that ultrasound strain imaging is feasible in ex vivo lateral collateral ligaments, which are relatively small structures. Additional studies should be designed for a more informed assessment of optimal in vivo strain measurements in collateral knee ligaments.

Biaxial quantification of deep layer transverse carpal ligament elastic properties by sex and region.

BACKGROUND: The transverse carpal ligament is a major component of the carpal tunnel and is an important structure in the etiology of carpal tunnel syndrome. The current study aimed to quantify biaxial elastic moduli of the transverse carpal ligament and compare differences between sex and region (Radial and Ulnar). METHODS: Biaxial testing of radial and ulnar samples from twenty-two (thirteen male, nine female) human fresh frozen cadaveric transverse carpal ligaments was performed. Elastic moduli and stiffness were calculated and compared. FINDINGS: Biaxial elastic moduli of the transverse carpal ligament ranged from 0.76MPa to 3.38MPa, varying based on region (radial and ulnar), testing direction (medial-lateral and proximal-distal) and sex. Biaxial elastic moduli were significantly larger in the medial-lateral direction than the proximal-distal direction (P<0.001). Moduli were significantly larger ulnarly than radially (P=0.001). No significant differences due to gender were noted. INTERPRETATION: The regional variations in biaxial elastic moduli of the transverse carpal ligament may help improve non-invasive treatment methods for carpal tunnel syndrome, specifically manipulative therapy. The smaller biaxial elastic moduli found in the radial region suggests that manipulative therapy should be focused on the radial aspect of the transverse carpal ligament. The trend where female transverse carpal ligaments had larger stiffness in the ulnar location than males suggests that that the increased prevalence of carpal tunnel syndrome in women may be related to an increased stiffness of the transverse carpal ligament, however further work is warranted to evaluate this trend.

3D FSE Cube and VIPR-aTR 3.0 Tesla magnetic resonance imaging predicts canine cranial cruciate ligament structural properties.

Estimation of cranial cruciate ligament (CrCL) structural properties in client-owned dogs with incipient cruciate rupture would be advantageous. The objective of this study was to determine whether magnetic resonance imaging (MRI) measurement of normal CrCL volume in an ex-vivo canine model predicts structural properties. Stifles from eight dogs underwent 3.0 Tesla 3D MRI. CrCL volume and normalized median grayscale values were determined using 3D Fast Spin Echo (FSE) Cube and Vastly under-sampled Isotropic PRojection (VIPR)-alternative repetition time (aTR) sequences. Stifles were then mechanically tested. After joint laxity testing, CrCL structural properties were determined, including displacement at yield, yield load, load to failure, and stiffness. Yield load and load to failure (R(2)=0.56, P <0.01) were correlated with CrCL volume determined by VIPR-aTR. Yield load was also correlated with CrCL volume determined by 3D FSE Cube (R(2)=0.32, P <0.05). Structural properties were not related to median grayscale values. Joint laxity and CrCL stiffness were not related to MRI parameters, but displacement at yield load was related to CrCL volume for both sequences during testing (R(2)>0.57, P <0.005). In conclusion, 3D MRI offers a predictive method for estimating canine CrCL structural properties. 3D MRI may be useful for monitoring CrCL properties in clinical trials.

Achilles tendons from decorin- and biglycan-null mouse models have inferior mechanical and structural properties predicted by an image-based empirical damage model.

Achilles tendons are a common source of pain and injury, and their pathology may originate from aberrant structure function relationships. Small leucine rich proteoglycans (SLRPs) influence mechanical and structural properties in a tendon-specific manner. However, their roles in the Achilles tendon have not been defined. The objective of this study was to evaluate the mechanical and structural differences observed in mouse Achilles tendons lacking class I SLRPs; either decorin or biglycan. In addition, empirical modeling techniques based on mechanical and image-based measures were employed. Achilles tendons from decorin-null (Dcn(-/-)) and biglycan-null (Bgn(-/-)) C57BL/6 female mice (N=102) were used. Each tendon underwent a dynamic mechanical testing protocol including simultaneous polarized light image capture to evaluate both structural and mechanical properties of each Achilles tendon. An empirical damage model was adapted for application to genetic variation and for use with image based structural properties to predict tendon dynamic mechanical properties. We found that Achilles tendons lacking decorin and biglycan had inferior mechanical and structural properties that were age dependent; and that simple empirical models, based on previously described damage models, were predictive of Achilles tendon dynamic modulus in both decorin- and biglycan-null mice.

Anterior cruciate ligament biomechanics during robotic and mechanical simulations of physiologic and clinical motion tasks: a systematic review and meta-analysis.

Investigators use in vitro joint simulations to invasively study the biomechanical behaviors of the anterior cruciate ligament. The aims of these simulations are to replicate physiologic conditions, but multiple mechanisms can be used to drive in vitro motions, which may influence biomechanical outcomes. The objective of this review was to examine, summarize, and compare biomechanical evidence related to anterior cruciate ligament function from in vitro simulations of knee motion. A systematic review was conducted (2004 to 2013) in Scopus, PubMed/Medline, and SPORTDiscus to identify peer-reviewed studies that reported kinematic and kinetic outcomes from in vitro simulations of physiologic or clinical tasks at the knee. Inclusion criteria for relevant studies were articles published in English that reported on whole-ligament anterior cruciate ligament mechanics during the in vitro simulation of physiologic or clinical motions on cadaveric knees that were unaltered outside of the anterior-cruciate-ligament-intact, -deficient, and -reconstructed conditions. A meta-analysis was performed to synthesize biomechanical differences between the anterior-cruciate-ligament-intact and reconstructed conditions. 77 studies met our inclusion/exclusion criteria and were reviewed. Combined joint rotations have the greatest impact on anterior cruciate ligament loads, but the magnitude by which individual kinematic degrees of freedom contribute to ligament loading during in vitro simulations is technique-dependent. Biomechanical data collected in prospective, longitudinal studies corresponds better with robotic-manipulator simulations than mechanical-impact simulations. Robotic simulation indicated that the ability to restore intact anterior cruciate ligament mechanics with anterior cruciate ligament reconstructions was dependent on loading condition and degree of freedom examined.