Improving the clinical efficiency of T2 mapping of ligament integrity

Current MR methods use T₂^? relaxation time as a surrogate measure of ligament strength. Currently, a multi-echo voxel-wise least squares fit is the gold standard to create T₂^? maps; however, the post-processing is time-intensive and serves as a stopgap for clinical use. The study objective was to determine if an alternative method could improve post-processing time without sacrificing fidelity of T₂^? values for eventual translational use in the clinic. Using a 6 echo FLASH sequence, three different methods were used to determine intact posterior cruciate ligament (PCL) median T₂^? Two of these methods utilized a voxel-wise method to establish T₂^? maps: (1) a current “gold standard” method using a voxel-wise 6 echo least-squares fit (6LS) and (2) a voxel-wise 2 echo point T₂^? determination (2MM). The third method used median ligament signal intensity and a single nonlinear least-squares fit (6LS_ROI) instead of a voxel-wise basis. The resulting median T₂^? values of the PCL and computational time were compared. The median T₂^? values were 42% higher using the 2MM compared to the 6LS method (p<0.0001). However, a strong correlation was found for the median T₂^? values between the 2MM and 6LS methods (R²=0.80). The median T₂^? values were not significantly different between the 6LS and 6LS_ROI methods (p=0.519). Using the 2MM (which provides a regional map) and the 6LS_ROI (which efficiently provides the median T₂^? value) methods in tandem would take only minutes of post-processing computational time compared to the 6LS method (~540 min), and hence would facilitate clinical application of T₂^? maps to predict ligament structural properties as a patient outcome measure.     

带线锚钉修复三角韧带损伤的效果及对患者踝关节功能的影响

目的:研究带线锚钉修复三角韧带损伤在踝关节骨折内固定治疗中的作用及对踝关节功能的影响。方法:回顾性分析2012年9月至2016年8月本院收治的72例裸关节骨折并三角韧带损伤患者并且行切开复位钢板置入内固定,及采取带线锚钉内固定方式修复三角韧带损伤视为观察组;另选取同期在本院进行踝关节骨折内固定治疗但不修复三角韧带的72例患者视为对照组。分析患者治疗前、治疗后1个月、3个月、6个月踝关节功能恢复情况,观察患侧内踝间隙和不良反应。结果:观察组在治疗后1个月、3个月、6个月的AOFAS评分显著高于对照组(P0.05)。观察组在治疗后6个月后的患侧内踝间隙显著小于对照组(P0.05)。结论:带线锚钉修复三角韧带损伤在踝关节骨折内固定治疗中,可明显降低患侧内踝间隙距离,可促进患者踝关节功能恢复,无严重不良反应,值得进一步广泛推广使用。     

Inter-session reliability and sex-related differences in hamstrings total reaction time,pre-motor time and motor time during eccentric isokinetic contractions in recreational athlete

The purposes were twofold: (a) to ascertain the inter-session reliability of hamstrings total reaction time, pre-motor time and motor time; and (b) to examine sex-related differences in the hamstrings reaction times profile. Twenty-four men and 24 women completed the study. Biceps femoris and semitendinosus total reaction time, pre-motor time and motor time measured during eccentric isokinetic contractions were recorded on three different occasions. Inter-session reliability was examined through typical percentage error (CV_TE), percentage change in the mean (CM) and intraclass correlations (ICC). For both biceps femoris and semitendinosus, total reaction time, pre-motor time and motor time measures demonstrated moderate inter-session reliability (CV_TE < 10%; CM < 3%; ICC > 0.7). The results also indicated that, although not statistically significant, women reported consistently longer hamstrings total reaction time (23.5 ms), pre-motor time (12.7 ms) and motor time (7.5 ms) values than men. Therefore, an observed change larger than 5%, 9% and 8% for total reaction time, pre-motor time and motor time respectively from baseline scores after performing a training program would indicate that a real change was likely. Furthermore, while not statistically significant, sex differences were noted in the hamstrings reaction time profile which may play a role in the greater incidence of ACL injuries in women.     

Biological aspects of orthodontic tooth movement: A review of literature

This review of literature describes the cellular and molecular biology of orthodontic tooth movement, including various theories and effect of chemical mediators on tooth movement. The better understanding of the tooth movement mechanism will inspire the clinicians to design and implement effective appliances that will result in maximum benefits and minimum tissue damage to the patients. This paper also emphasizes the applied aspect of different medication and hormones, during orthodontic treatment, on the signaling molecules which produce bone remodeling.     

In-vitro formation of a collagenous matrix upon previously diseased and experimentally treated cemental root surfaces

Summary A diseased and mechanically treated surface of root cementum is known, clinically, to favor periodontal regeneration. The present investigation was undertaken to test whether previously diseased and experimentally treated root surfaces can support the in-vitro formation of a new collagenous matrix. Three teeth extracted for advanced periodontitis were treated first with 5% sodium hypochlorite for 2 h to remove all organic material from the root surface. After the healthy, apical one third of the root was cut off, the roots were scaled with moderate pressure to remove visible calculus. Non-demineralized root discs were cut and placed on a co-culture of periodontal ligament- and alveolar bone-derived cells. After 7 weeks in culture, either one of two matrix types was found along the root surface. The most frequent matrix consisted of clusters of cells layered within densely aggregated collagen fibrils. The other, less frequent matrix consisted of loosely arranged collagen fibrils adjacent to the cemental surface. The findings support the notion that, in vitro, a collagenous matrix is formed in contact to diseased and experimentally treated root surfaces. However, the smooth, non-demineralized and scaled cemental surface does not appear to be a suitable substrate for interdigitation with newly produced collagen fibrils.     

Quantifying extensibility of rotator cuff muscle with tendon rupture using shear wave elastography: A cadaveric study

Surgical repair for large rotator cuff tear remains challenging due to tear size, altered muscle mechanical properties, and poor musculotendinous extensibility. Insufficient extensibility might lead to an incomplete reconstruction; moreover, excessive stresses after repair may result in repair failure without healing. Therefore, estimates of extensibility of cuff muscles can help in pre-surgical planning to prevent unexpected scenarios during surgery. The purpose of this study was to determine if quantified mechanical properties of the supraspinatus muscle using shear wave elastography (SWE) could be used to predict the extensibility of the musculotendinous unit on cadaveric specimens. Forty-five fresh-frozen cadaveric shoulders (25 intact and 20 with rotator cuff tear) were used for the study. Passive stiffness of 4 anatomical regions in the supraspinatus muscle was first measured using SWE. After detaching the distal edge of supraspinatus muscle from other cuff muscles, the detached muscle was axially pulled with the scapula fixed. The correlation between the SWE modulus and the extensibility of the muscle under 30 and 60 N loads was assessed. There was a significant negative correlation between SWE measurements and the experimental extensibility. SWE modulus for the anterior-deep region in the supraspinatus muscle showed the strongest correlation with extensibility under 30 N (r = 0.70, P < 0.001) and 60 N (r = 0.68, P < 0.001). Quantitative SWE assessment for the supraspinatus muscle was highly correlated with extensibility of musculotendinous unit on cadaveric shoulders. This technique may be used to predict the extensibility for rotator cuff tears for pre-surgical planning.     

YAP regulates periodontal ligament cell differentiation into myofibroblast interacted with RhoA/ROCK pathway

During orthodontic tooth movement (OTM), periodontal ligament cells (PDLCs) receive the mechanical stimuli and transform it into myofibroblasts (Mfbs). Indeed, previous studies have demonstrated that mechanical stimuli can promote the expression of Mfb marker α-smooth muscle actin (α-SMA) in PDLCs. Transforming growth factor β1 (TGF-β1), as the target gene of yes-associated protein (YAP), has been proven to be involved in this process. Here, we sought to assess the role of YAP in Mfbs differentiation from PDLCs. The time-course expression of YAP and α-SMA was manifested in OTM model in vivo as well as under tensional stimuli in vitro. Inhibition of RhoA/Rho-associated kinase (ROCK) pathway using Y27632 significantly reduced tension-induced Mfb differentiation and YAP expression. Moreover, overexpression of YAP with lentiviral transfection in PDLCs rescued the repression effect of Mfb differentiation induced by Y27632. These data together suggest a crucial role of YAP in regulating tension-induced Mfb differentiation from PDLC interacted with RhoA/ROCK pathway.     

Three-dimensional Orthotropic Viscoelastic Finite Element Model of a Human Ligament

Ligaments undergo finite strain displaying hyperelastic behaviour as the initially tangled fibrils present straighten out, combined with viscoelastic behaviour (strain rate sensitivity). In the present study the anterior cruciate ligament of the human knee joint is modelled in three dimensions to gain an understanding of the stress distribution over the ligament due to motion imposed on the ends, determined from experimental studies. A three dimensional, finite strain material model of ligaments has recently been proposed by Pioletti in Ref. [2]. It is attractive as it separates out elastic stress from that due to the present strain rate and that due to the past history of deformation. However, it treats the ligament as isotropic and incompressible. While the second assumption is reasonable, the first is clearly untrue. In the present study an alternative model of the elastic behaviour due to Bonet and Burton (Ref. [4]) is generalized. Bonet and Burton consider finite strain with constant modulii for the fibres and for the matrix of a transversely isotropic composite. In the present work, the fibre modulus is first made to increase exponentially from zero with an invariant that provides a measure of the stretch in the fibre direction. At 12% strain in the fibre direction, a new reference state is then adopted, after which the material modulus is made constant, as in Bonet and Burton's model. The strain rate dependence can be added, either using Pioletti's isotropic approximation, or by making the effect depend on the strain rate in the fibre direction only.

A solid model of a ligament is constructed, based on experimentally measured sections, and the deformation predicted using explicit integration in time. This approach simplifies the coding of the material model, but has a limitation due to the detrimental effect on stability of integration of the substantial damping implied by the nonlinear dependence of stress on strain rate. At present, an artificially high density is being used to provide stability, while the dynamics are being removed from the solution using artificial viscosity. The result is a quasi-static solution incorporating the effect of strain rate. Alternate approaches to material modelling and integration are discussed, that may result in a better model.     

Computational and Experimental Study of Performance of an Artificial Ligament: DacronTM yarn

Abstract

The success rate of reconstructing the Anterior Cruciate Ligament (ACL) with prosthetic ligaments is currently low both in humans and animals. The stress distribution in prosthetic ligaments that causes failure is very complex and not yet understood. Therefore, we have begun to develop a Finite Element Model of a prosthetic ACL. Here we describe the normal and contact stresses in Dacron^TM yarn (a multi-fibrillar structure) using input data based on experimental measurements of the load and strain of six designed yarns.

The results show that the normal and contact stresses in the fibres of the ACL yarn are directly proportional to the yam strains. Increasing the twisting length (transverse deformation) of the yarn increases the normal stress in the fibres and the yarn modulus, but decreases the contact stresses between the fibres. The structural properties of a yarn are dependent on the specific arrangement of various filament types. Increasing the distance between the longitudinal (symmetry) axes of the filaments and the axis of symmetry of the yarn decreases the stresses.