Non-invasive estimation of the diastolic elastic and viscoelastic properties of the left ventricle

The present study applies a non-invasive method to the quantitative evaluation of left ventricular stiffness in normal subjects and in patients with ischaemic heart disease (IHD). We have studied 20 patients with IHD and 25 healthy subjects. The third heart sound (S3) was detectable in all patients. We have correlated the energy spectrum of S3, divided into 15 Hz bands, with a series of echocardiographic parameters. The existence of a significant correlation between the spectrum energy and the diameter and thickness of the left ventricle at the moment of S3 allowed us to explore the possibility of interpreting the origin of S3 based on a mathematical model. Our hypothesis has been that, once the left ventricle starts vibrating, it behaves as a simple physical model composed of a mass and an elastic element. To this purely elastic model one can add a factor accounting for viscosity, with a damping effect, to obtain a more complex viscoelastic model. The stiffness coefficient 'k' was computed in both models from the peak frequency of S3 and the left ventricular mass at the moment of S3. Furthermore, in the viscoelastic model, the damping element 'c' was also computed. Both parameters--k and c--were significantly increased in the group with IHD compared with the control group. Although a simplification of the vibrating system, these models make it possible to obtain non-invasively information on the characteristics of the left ventricle through the combined use of echocardiography and spectral analysis of S3.     

The attachments of the anteromedial and posterolateral fibre bundles of the anterior cruciate ligament

The tibial attachments of the individual anteromedial (AM) and posterolateral (PL) fibre bundles and the entire attachment of the anterior cruciate ligament are described, relating them to consistent bony landmarks; 55 fresh-frozen specimens were measured. The fibre bundles were separated and excised at their attachments and their peripheries marked with a pen. High-resolution scaled digital photographs were taken of each dissected specimen and transferred onto a computer for analysis. A wide variation was found when using the posterior tibial axis, the anterior tibial surface and the medial tibial spine as reference points. The most consistent measurements used the tibial interspinous “over-the-back” ridge as a datum. The attachments of the PL and AM bundles were centred 10 ± 1 mm (mean ± SD) and 17 ± 2 mm anterior to the over-the-back ridge. They were 4 ± 1 and 5 ± 1 mm, respectively, lateral to the medial tibial spine border. The positions of 6 mm circles in the posterior-medial limits of the fibre bundles (representing tunnels in a double-tunnel reconstruction) were measured. The overall dimensions of the tibial plateaux correlated significantly with many measurements. The results from this study could be used to guide ACL reconstruction techniques.     

A quantitative analysis of valgus torque on the ACL: a human cadaveric study.

The loads needed to elicit a positive pivot shift test in a knee with an anterior cruciate ligament (ACL) rupture have not been quantified. The coupled anterior tibial translation (ATT), coupled internal tibial rotation (ITR), and the in situ force in the ACL in response to a valgus torque, an inherent component of the pivot shift test, were measured in 10 human cadaveric knee specimens. Using a robotic/universal force-moment sensor testing system, valgus torques ranging from 0.0 to 10.0 Nm were applied in nine increments on the intact and ACL-deficient knee in flexion ranging from 0 degrees to 90 degrees. At 15 degrees of knee flexion, the coupled ATT and ITR were significantly increased in the ACL-deficient knee when compared to the intact knee. Coupled ATT increased a maximum of 291% (6.7 mm, p<0.05), while coupled ITR increased a maximum of 85% (5.1 degrees, p<0.05). At 30 degrees, the increases in coupled ATT and ITR were significant at valgus loads of 3.3 Nm and greater with a maximum increase in coupled ATT of 137% (6.3 mm, p<0.05) and a maximum increase in coupled ITR of 38% (3.6 degrees, p<0.05). At 45 degrees, coupled ATT increased significantly (maximum of 69%, 4.4 mm, p<0.05), but only at torques > or =6.7 Nm. The in situ force in the ACL was less than 20 N for all flexion angles when a torque between 3.3 and 5.0 Nm was applied. Low valgus torque elicited tibial subluxation in the ACL-deficient knee with low in situ ACL forces, similar to a positive pivot shift test. Thus, application of a valgus torque may be suitable to evaluate ACL-deficient and ACL-reconstructed knees, since subluxation can be achieved with minimal harm to the ACL graft. This work is important in understanding one load component needed for the pivot shift examination; further studies quantifying other load components are essential for better comprehension of the in vivo pivot shift examination.     

Ⅱ型浮膝损伤术后膝关节功能康复

目的:总结Ⅱ型浮膝损伤患者的治疗方法和手术后膝关节功能康复疗效。方法:回顾分析经治的68例患者,男57例,女11例;年龄17~60岁。68例共74侧肢体的Ⅱ型浮膝损伤-膝关节内骨折病例,其中双侧肢体Ⅱ型浮膝骨折6例。根据患者骨折类型、是否存在开放性损伤、软组织损伤程度分别采用内固定(髓内钉、解剖钢板)和支架外固定方法,术后均采用统一、系统的康复治疗。术后对治疗结果采用Karlstrom和Olerud的浮膝损伤治疗标准进行评价;使用χ2检验对两种固定方法治疗后膝关节功能康复效果差别进行显著性分析。结果:所有病例均得到1~4年的随访,平均24个月。内固定组优良率64.29%,支架外固定组优良率80.43%。内固定组与支架外固定组比较,膝关节活动受限度指标有统计学差异(P<0.05),说明Ⅱ型浮膝损伤应当注重对关节内骨折的复位和减少对膝关节周围软组织的破坏。结论:①早期功能恢复期支架组优于内固定组;②牵引后及术后早期系统的康复治疗有利于膝关节功能恢复和减少并发症;③伸膝功能锻炼应当在牵引治疗后即开始,膝关节屈伸功能锻炼在手术后3d进行。     

The effect of ionic strength on the kinetics of rigor development in skinned fast-twitch skeletal muscle fibres

 Recent atomic 3-D reconstructions of the acto-myosin interface suggest that electrostatic interactions are important in the initial phase of cross-bridge formation. Earlier biochemical studies had also given strong evidence for the ionic strength dependence of this step in the cross-bridge cycle. We have probed these interactions by altering the ionic strength (Γ/2) of the medium mainly with K⁺, imidazole⁺ and EGTA^2– to vary charge shielding. We examined the effect of ionic strength on the kinetics of rigor development at low Ca²⁺ (experimental temperature 18–22°C) in chemically skinned single fast-twitch fibres of mouse extensor digitorum longus (EDL) muscle. On average the delay before rigor onset was 10 times longer, the maximum rate of rigor tension development was 10 times slower, the steady-state rigor tension was 3 times lower and the in-phase stiffness was 2 times lower at high (230 mM) compared to low (60 mM) ionic strength. These results were modelled by calculating ATP depletion in the fibre due to diffusional loss of ATP and acto-myosin Mg.ATPase activity. The difference in delay before rigor onset at low and high ionic strength could be explained in our model by assuming a 15 times higher Mg.ATPase activity and a threefold increase in K _m in relaxing conditions at low ionic strength. Activation by Ca²⁺ induced at different time points before and during onset of rigor confirmed the calculated time course of ATP depletion. We have also investigated ionic strength effects on rigor development with the activated troponin/tropomyosin complex. ATP withdrawl at maximum activation by Ca²⁺ induced force transients which led into a ”high rigor” state. The peak forces of these force transients were very similar at low and high ionic strength. The subsequent decrease in tension was only 10% slower and steady-state ”high rigor” tension was reduced by only 27% at high compared to low ionic strength. Addition of 10 mM phosphate to lower cross-bridge attachment strongly suppressed the transient increases in force at high ionic strength and reduced the steady-state rigor tension by 17%. A qualitatively similar but smaller effect of phosphate was observed at low ionic strength where steady-state rigor force was reduced by 10%. The data presented in this study show a very strong effect of ionic strength on rigor development in relaxed fibres whereas the ionic strength dependence of rigor development after thin filament activation was much less. The data confirm the importance of electrostatic interactions in cross-bridge attachment and cross-bridge-attachment-induced activation of thin filaments. Received: 3 September 1997 / Received after revision and accepted: 12 December 1997     

屈膝过程中的胫股运动特性分析

本文采用三维位移测量方法，测试１０例离体人膝标本的胫股关节三维运动特性。发现屈膝过程中，胫股运动也具有典型的三维运动特点。其中在屈膝初期的３０°内，胫骨内旋最明显并伴有胫骨内翻现象，平均内旋８°，内翻６－７ｍｍ，膝关节完全伸直时胫股扣锁使膝关节稳定，屈曲时胫股“解锁”使膝关节松弛，具重要的临床意义，同时提示，在解释传统的胫股扣锁现象时不应遗漏伴随发生的胫骨内／外翻现象。     

350例膝关节镜检查分析

自1981年以来进行了350例膝关节镜检查。明确诊断340例(97.1%),纠正诊断52例(14.7%),补充诊断47例(13.4%)。关节镜检查不仅有助于确定临床诊断,而且提高了手术的准确性。     

MR imaging evaluation of knee collateral ligaments and related injuries: Comparison of T1-weighted,T2-weighted,and fat-saturated T2-weighted sequences—correlation with clinical findings

The objectives of this study were to compare the ability of T1-weighted (T1W), proton density/T2-weighted (PD/T2W), and fat saturation (FS) PD/T2W magnetic resonance (MR) sequences for depiction of the knee collateral ligaments and related injuries, and to compare MR findings with clinical findings. Ten subjects with normal knee ligaments and 64 patients with suspected collateral ligament injuries underwent coronal T1W, PD/T2W, and FS PD/T2W imaging. Abnormalities ranged from edema surrounding the collateral ligaments (grade I) to complete disruption of ligamentous fibers (grade III). FS PD/T2W images improved definition of the medial collateral ligament (MCL) and lateral collateral ligament (LCL) compared with other sequences in 78% and 81% of patients, respectively. While the apparent grade of collateral ligament injury was similar with all pulse sequences in most patients, depiction of such injury was usually most conspicuous on FS PD/T2W images (MCL, 92% of patients; LCL, 38% of patients). In no patients were clinically diagnosed collateral ligament injuries undetected or understaged with MR imaging. MR findings indicated higher-grade MCL and LCL injuries than did clinical examination in 24 and 15 patients, respectively.     

Arthroscopic all-inside repair techniques of lateral meniscus anterior horn tear: a technical note

Although the conventional outside-in technique is especially useful for repairing tears in the anterior portion of the meniscus, it has a disadvantage of making an additional 1–2 cm sized skin incision and tying knots subcutaneously over the capsule. Therefore we devised two all-inside repair techniques of lateral meniscus anterior horn tear according to the site of meniscal tear, meniscosynovial junction or red–red zone. Because these techniques are modified methods of the outside-in meniscal repair using a spinal needle, they are as simple as conventional outside-in technique. In addition they have advantages of vertical mattress suture, which is an important characteristic of the all-inside repair, and no additional incision. We recommend these techniques as an alternative method for repairing an anterior horn tear of the lateral meniscus.     

后交叉韧带损伤MRI诊断指标的评价

目的评价后交叉韧带(PCL)损伤各种MRI征象的诊断价值。资料与方法分析32例经关节镜或临床诊断的PCL损伤患者MRI资料,并与57例非PCL损伤病例对照,总结PCL损伤直接和间接征象,依据各征象建立回归模型。结果正常PCL可分为"弓"形、"U"形、和"打结"形3种形态。根据PCL损伤征象建立的回归模型,其诊断的重要程度依次为PCL消失、不连续,PCL信号异常,内侧副韧带损伤,PCL增粗,三角间隙积液以及骨挫伤。结论MRI是诊断PCL损伤的重要手段。PCL损伤各征象对诊断的重要性不同,以此建立的回归模型有较强的预测能力。