Tendon to bone healing: differences in biomechanical,structural, and compositional properties due to a range of activity levels

Little knowledge exists about the healing process of the tendon to bone insertion, and hence little can be done to improve tissue healing. The goal of this study is to describe the healing of the supraspinatus tendon to its bony insertion under a variety of loading conditions. Tendons were surgically detached and repaired in rats. Rat shoulders were then immobilized, allowed cage activity, or exercised. Shoulders that were immobilized demonstrated superior structural (significantly higher collagen orientation), compositional (expression of extracellular matrix genes similar to the uninjured insertion), and quasilinear viscoelastic properties (A = 0.30 +/- 0.10 MPa vs. 0.16 +/- 0.08 MPa, B = 17.4 +/- 2.9 vs. 15.1 +/- 0.9, and tau 2 = 344 +/- 161 s vs. 233 +/- 40 s) compared to those that were exercised, contrary to expectations. With this knowledge of the healing response, treatment modalities for rotator cuff tears can be developed.     

Glenohumeral contact forces in reversed anatomy shoulder replacement

A major requirement to design an implant is to develop our understanding of the applied internal forces during everyday activities. In the absence of any basic apparatus for measuring forces directly, it is essential to rely on modelling. The major aim of this study was therefore to understand the biomechanical function of subjects with the reversed anatomy Bayley?Walker prosthesis, using an inverse dynamic shoulder model. In this context, the muscle and joint forces of 12 Bayley–Walker subjects were compared to those of 12 normal subjects during 12 activities of daily living.Maximum glenohumeral contact forces for normal and Bayley–Walker subjects were found to be 77% (±15) and 137% (±21) body weight for lifting a 2 kg shopping bag, and the least forces 29% (±4) and 67% (±8) body weight for reaching to opposite axilla, respectively. For normal subjects, middle deltoid, supraspinatus and infraspinatus were found to be the most active muscles across the subjects and tasks. On the other hand, for implanted subjects with a lack of rotator cuff muscles, the middle deltoid and coracobrachialis muscles were found to be the most active. The biomechanical model can therefore be used in order to gain knowledge about the pathology as well as possible post surgical rehab for subjects with reversed shoulder replacement.     

Comparison of an EMG-based and a stress-based method to predict shoulder muscle forces

The estimation of muscle forces in musculoskeletal shoulder models is still controversial. Two different methods are widely used to solve the indeterminacy of the system: electromyography (EMG)-based methods and stress-based methods. The goal of this work was to evaluate the influence of these two methods on the prediction of muscle forces, glenohumeral load and joint stability after total shoulder arthroplasty. An EMG-based and a stress-based method were implemented into the same musculoskeletal shoulder model. The model replicated the glenohumeral joint after total shoulder arthroplasty. It contained the scapula, the humerus, the joint prosthesis, the rotator cuff muscles supraspinatus, subscapularis and infraspinatus and the middle, anterior and posterior deltoid muscles. A movement of abduction was simulated in the plane of the scapula. The EMG-based method replicated muscular activity of experimentally measured EMG. The stress-based method minimised a cost function based on muscle stresses. We compared muscle forces, joint reaction force, articular contact pressure and translation of the humeral head. The stress-based method predicted a lower force of the rotator cuff muscles. This was partly counter-balanced by a higher force of the middle part of the deltoid muscle. As a consequence, the stress-based method predicted a lower joint load (16% reduced) and a higher superior–inferior translation of the humeral head (increased by 1.2 mm). The EMG-based method has the advantage of replicating the observed cocontraction of stabilising muscles of the rotator cuff. This method is, however, limited to available EMG measurements. The stress-based method has thus an advantage of flexibility, but may overestimate glenohumeral subluxation.     

Vascular endothelial growth factor enhances tendon-bone healing by activating Yes-associated protein for angiogenesis induction and rotator cuff reconstruction in rats

Local angiogenesis following rotator cuff reconstruction is crucial for tendon-bone healing. The current research on the mechanism underlying angiogenesis that promotes tendon-bone healing is scarce. This study investigates the mechanism underlying vascular endothelial growth factor (VEGF)-Hippo signaling pathway's involvement in tendon-bone healing following rotator cuff reconstruction. Verteporfin, the inhibitor of the Yes-associated protein (YAP), was used to mechanically test and analyze two groups of tensile-failure loads following rotator cuff reconstruction and to detect collagen and angiogenesis-related marker expressions in the tendon. The interaction mechanism of the VEGF-Hippo signaling pathway was assessed using human umbilical vein endothelial cells (HUVECs). The diameter of the supraspinatus tendon reduced following verteporfin treatment. Mechanical tests revealed that verteporfin significantly reduces the tensile-failure load of the supraspinatus tendon. Verteporfin significantly reduces collagen 1 (Col 1), Col 3, Angiopoietin 2, CD31, Von Willebrand factor, CTGF, and CYR61 expressions. In HUVECs, VEGF activates VEGF receptors and inhibits LATS and YAP phosphorylation. YAP is then transferred to the nucleus to further activate downstream pathways. Therefore, verteporfin can inhibit VEGF-induced YAP pathway activation by inhibiting YAP activity. Angiogenesis in tendon-bone healing following rotator cuff reconstruction requires VEGF-Hippo signaling pathway synergy.     

Trunk-Pelvis motions and spinal loads during upslope and downslope walking among persons with transfemoral amputation

Larger trunk and pelvic motions in persons with (vs. without) lower limb amputation during activities of daily living (ADLs) adversely affect the mechanical demands on the lower back. Building on evidence that such altered motions result in larger spinal loads during level-ground walking, here we characterize trunk-pelvic motions, trunk muscle forces, and resultant spinal loads among sixteen males with unilateral, transfemoral amputation (TFA) walking at a self-selected speed both up (“upslope”; 1.06 ± 0.14 m/s) and down (“downslope”; 0.98 ± 0.20 m/s) a 10-degree ramp. Tri-planar trunk and pelvic motions were obtained (and ranges-of-motion [ROM] computed) as inputs for a non-linear finite element model of the spine to estimate global and local muscle (i.e., trunk movers and stabilizers, respectively) forces, and resultant spinal loads. Sagittal- (p = 0.001), frontal- (p = 0.004), and transverse-plane (p < 0.001) trunk ROM, and peak mediolateral shear (p = 0.011) and local muscle forces (p = 0.010) were larger (respectively 45, 35, 98, 70, and 11%) in upslope vs. downslope walking. Peak anteroposterior shear (p = 0.33), compression (p = 0.28), and global muscle (p = 0.35) forces were similar between inclinations. Compared to previous reports of persons with TFA walking on level ground, 5–60% larger anteroposterior and mediolateral shear observed here (despite ∼0.25 m/s slower walking speeds) suggest greater mechanical demands on the low back in sloped walking, particularly upslope. Continued characterization of trunk motions and spinal loads during ADLs support the notion that repeated exposures to these larger-than-normal (i.e., vs. level-ground walking in TFA and uninjured cohorts) spinal loads contribute to an increased risk for low back injury following lower limb amputation.     

Sub-regional activation of supraspinatus and infraspinatus muscles during activities of daily living is task dependent

The supraspinatus and infraspinatus muscles each have multiple sub-regions that may activate differentially in activities of daily living. Awareness of these differential demands critically informs rehabilitation of rotator cuff muscle following injury, particularly if centered on recovering and strengthening the rotator cuff to perform daily tasks. This study quantified muscle activation of supraspinatus and infraspinatus sub-regions during the performance of six activities of daily living. Twenty-three participants (mean: 22.6 ± 2.6 years) completed the following tasks: opening a jar, reaching at shoulder height, overhead reaching, pouring water from a pitcher, eating with a spoon, and combing hair. Indwelling electromyography was collected from the anterior and posterior supraspinatus and superior, middle, and inferior infraspinatus. Tasks requiring high arm elevations (e.g. reaching at shoulder and overhead height) activated anterior supraspinatus between 21 and 28% MVC. The posterior supraspinatus consistently activated between 10 and 30% MVC across all tasks. All sub-regions of infraspinatus activated highly (between 18 and 25% MVC) in tasks requiring high arm elevations in flexion. These findings may be leveraged to define effective measures to increase rotator cuff function in daily tasks.     

Measuring dynamic in-vivo glenohumeral joint kinematics: technique and preliminary results

Rotator cuff tears are a common injury that affect a significant percentage of the population over age 60. Although it is widely believed that the rotator cuff's primary function is to stabilize the humerus against the glenoid during shoulder motion, accurately measuring the three-dimensional (3D) motion of the shoulder's glenohumeral joint under in-vivo conditions has been a challenging endeavor. In particular, conventional motion measurement techniques have frequently been limited to static or two-dimensional (2D) analyses, and have suffered from limited or unknown in-vivo accuracy. We have recently developed and validated a new model-based tracking technique that is capable of accurately measuring the 3D position and orientation of the scapula and humerus from biplane X-ray images. Herein we demonstrate the in-vivo application of this technique for accurately measuring glenohumeral joint translations during shoulder motion in the repaired and contralateral shoulders of patients following rotator cuff repair. Five male subjects were tested at 3-4 months following arthroscopic rotator cuff repair. Superior-inferior humeral translation was measured during elevation, and anterior-posterior humeral translation was measured during external rotation in both the repaired and contralateral shoulders. The data failed to detect statistically significant differences between the repaired and contralateral shoulders in superior-inferior translation (p=0.74) or anterior-posterior translation (p=0.77). The measurement technique overcomes the limitations of conventional motion measurement techniques by providing accurate, 3D, in-vivo measures of glenohumeral joint motion during dynamic activities. On-going research is using this technique to assess the effects of conservative and surgical treatment of rotator cuff tears.     

丹参酮IIA磺酸钠对烧伤植皮创面愈合及瘢痕形成的影响

目的:探讨丹参酮IIA磺酸钠注射液对烧伤患者植皮创面愈合及瘢痕形成情况的影响。方法:选取2014年3月至2014年12月我院收治的烧伤植皮患者62例,根据临床用药分为试验组(使用丹参酮IIA磺酸钠注射组)与对照组(未使用丹参酮IIA磺酸钠注射液)。比较两组创面愈合情况,术后植皮成活率及愈合后瘢痕形成情况。结果:1经治疗,两组创面均愈合,试验组患者植皮成活率为(97.12±1.89)%,高于对照组(89.96±1.86)%,差异具有统计学意义(P0.01);试验组愈合时间较对照组短,试验组创面愈合时间为10.1±1.9天,对照组为14.3±2.3天,两组比较差异具有统计学意义(P0.001);瘢痕形成评价试验组均优于对照组,差异具有统计学意义,其中血肿面积(1.50±0.03 vs.3.04±0.08,P0.01)、畸形率[2(6.45)vs.8(25.81),P0.05]、感染率[2(6.45)vs.9(29.03),P0.05]。结论:丹参酮IIA磺酸钠注射液对于烧伤植皮创面的患者,能够提高植皮成活率,促进创面愈合,减轻瘢痕形成,改善创面愈合质量。     

Characteristics and Stimulation Potential with BMP-2 and BMP-7 of Tenocyte-Like Cells Isolated from the Rotator Cuff of Female Donors

Tendon bone healing of the rotator cuff is often associated with non-healing or recurrent defects, which seems to be influenced by the patient’s age and sex. The present study aims to examine cellular biological characteristics of tenocyte-like cells that may contribute to this impaired rotator cuff healing. Moreover, a therapeutic approach using growth factors could possibly stimulate tendon bone healing. Therefore, our second aim was to identify patient groups who would particularly benefit from growth factor stimulation. Tenocyte-like cells isolated from supraspinatus tendons of female donors younger and older than 65 years of age were characterized with respect to different cellular biological parameters, such as cell density, cell count, marker expression, collagen-I protein synthesis, and stem cell potential. Furthermore, cells of the donor groups were stimulated with BMP-2 and BMP-7 (200 and 1000 ng/ml) in 3D-culture and analyzed for cell count, marker expression and collagen-I protein synthesis. Female donors older than 65 years of age showed significantly decreased cell count and collagen-I protein synthesis compared to cells from donors younger than 65 years. Cellular biological parameters including cell count, collagen-I and –III expression, and collagen-I protein synthesis of cells from both donor groups were stimulated with BMP-2 and BMP-7. The cells from donors older than 65 years revealed a decreased stimulation potential for cell count compared to the younger group. Cells from female donors older than 65 years of age showed inferior cellular biological characteristics. This may be one reason for a weaker healing potential observed in older female patients and should be taken into consideration for tendon bone healing of the rotator cuff.     

Quadrupedal locomotion in squirrel monkeys (Cebidae: Saimiri sciureus): a cineradiographic study of limb kinematics and related substrate reaction forces

Quadrupedal locomotion of squirrel monkeys on small-diameter support was analyzed kinematically and kinetically to specify the timing between limb movements and substrate reaction forces. Limb kinematics was studied cineradiographically, and substrate reaction forces were synchronously recorded. Squirrel monkeys resemble most other quadrupedal primates in that they utilize a diagonal sequence/diagonal couplets gait when walking on small branches. This gait pattern and the ratio between limb length and trunk length influence limb kinematics. Proximal pivots of forelimbs and hindlimbs are on the same horizontal plane, thus giving both limbs the same functional length. However, the hindlimbs are anatomically longer than the forelimbs. Therefore, hindlimb joints must be more strongly flexed during the step cycle compared to the forelimb joints. Because the timing of ipsilateral limb movements prevents an increasing amount of forelimb retraction, the forelimb must be more protracted during the initial stance phase. At this posture, gravity acts with long moment arms at proximal forelimb joints. Squirrel monkeys support most of their weight on their hindlimbs. The timing of limb movements and substrate reaction forces shows that the shift of support to the hindlimbs is mainly done to reduce the compressive load on the forelimb. The hypothesis of the posterior weight shift as a dynamic strategy to reduce load on forelimbs, proposed by Reynolds ([1985]) Am. J. Phys. Anthropol. 67:335-349; [1985] Am. J. Phys. Anthropol. 67:351-362), is supported by the high correlation of ratios between forelimb and hindlimb peak vertical forces and the range of motion of shoulder joint and scapula in primates.     

Gait mechanics of lemurid primates on terrestrial and arboreal substrates

Aspects of gait mechanics of two lemurid species were explored experimentally. Substrate reaction forces were recorded for three animals each of L. catta and E. fulvus walking and running at voluntary speeds either on a wooden runway with an integrated force platform or on elevated pole supports with a section attached to the force platform. The average height of the back over these substrates and fluctuations in this height were evaluated using video-analysis. Animals preferred walking gaits and lower speeds on the poles, and gallops and higher speeds on the ground. At overlapping speeds, few adjustments to substrate types were identified. Hind limb peak forces are usually lower on the poles than on the ground, and the caudal back is closer to the substrate. This suggests that greater hind limb flexion and reduced limb stiffness occurred on the poles. The support phases for both limbs at higher speeds are slightly elongated on the poles. Forelimb peak forces are not lower, and the trajectory of the caudal back does not follow a smoother path, i.e., not all elements of a compliant gait are present on the simulated arboreal substrates. The horizontal, rigid poles, offered as substitutes for branchlike supports in the natural habitat, may not pose enough of a challenge to require more substantial gait adjustments. Across substrates, forelimb peak forces are generally lower than hind limb peak forces. The interlimb force distribution is similar to that of most other primates with more even limb lengths. Walking gaits present a greater divergence in fore- and hind limb forces than galloping gaits, which are associated with higher forces. The more arboreal E. fulvus has higher forelimb forces than the more terrestrial L. catta, unlike some anthropoid species in which the arborealists have lower forelimb forces than the terrestrialists. As in other primate and nonprimate quadrupeds, the major propulsive thrust comes from the hind limbs in both lemurs. While our data confirm certain aspects of primate gait mechanics (e.g., generally higher hind limb forces), they do not fully support the notion of greater limb compliance. Neither a compliant forelimb on branchlike supports, nor a negative correlation of forelimb force magnitudes with degree of arboreality were observed. Increasing forelimb-to-hind-limb-force-ratios with increasing speed and force magnitudes are also not expected under this paradigm.     

Substrate alters forelimb to hindlimb peak force ratios in primates

It is often claimed that the walking gaits of primates are unusual because, unlike most other mammals, primates appear to have higher vertical peak ground reaction forces on their hindlimbs than on their forelimbs. Many researchers have argued that this pattern of ground reaction force distribution is part of a general adaptation to arboreal locomotion. This argument is frequently used to support models of primate locomotor evolution. Unfortunately, little is known about the force distribution patterns of primates walking on arboreal supports, nor do we completely understand the mechanisms that regulate weight distribution in primates. We collected vertical peak force data for seven species of primates walking quadrupedally on instrumented terrestrial and arboreal supports. Our results show that, when walking on arboreal vs. terrestrial substrates, primates generally have lower vertical peak forces on both limbs but the difference is most extreme for the forelimb. We found that force reduction occurs primarily by decreasing forelimb and, to a lesser extent, hindlimb stiffness. As a result, on arboreal supports, primates experience significantly greater functional differentiation of the forelimb and hindlimb than on the ground. These data support long-standing theories that arboreal locomotion was a critical factor in the differentiation of the forelimbs and hindlimbs in primates. This change in functional role of the forelimb may have played a critical role in the origin of primates and facilitated the evolution of more specialized locomotor behaviors.     

Comparison between line and surface mesh models to represent the rotator cuff muscle geometry in musculoskeletal models

Accurate muscle geometry (muscle length and moment arm) is required to estimate muscle function when using musculoskeletal modelling. In shoulder, muscles are often modelled as a collection of independent line segments, leading to non-physiological muscles trajectory, especially for the rotator cuff muscles. To prevent this, a surface mesh model was developed and validated against 7 MRI positions in one participant. Mean moment arm errors was 11.4% for the line vs. 8.8% for the mesh model. While the model with independent lines led to some non-physiological trajectories, the mesh model gave lower misestimations of muscle lengths and moment arms.     

Architectural properties of distal forelimb muscles in horses,Equus caballus

Articular injuries in athletic horses are associated with large forces from ground impact and from muscular contraction. To accurately and noninvasively predict muscle and joint contact forces, a detailed model of musculoskeletal geometry and muscle architecture is required. Moreover, muscle architectural data can increase our understanding of the relationship between muscle structure and function in the equine distal forelimb. Muscle architectural data were collected from seven limbs obtained from five thoroughbred and thoroughbred-cross horses. Muscle belly rest length, tendon rest length, muscle volume, muscle fiber length, and pennation angle were measured for nine distal forelimb muscles. Physiological cross-sectional area (PCSA) was determined from muscle volume and muscle fiber length. The superficial and deep digital flexor muscles displayed markedly different muscle volumes (227 and 656 cm3, respectively), but their PCSAs were very similar due to a significant difference in muscle fiber length (i.e., the superficial digital flexor muscle had very short fibers, while those of the deep digital flexor muscle were relatively long). The ulnaris lateralis and flexor carpi ulnaris muscles had short fibers (17.4 and 18.3 mm, respectively). These actuators were strong (peak isometric force, Fmax=5,814 and 4,017 N, respectively) and stiff (tendon rest length to muscle fiber length, LT:LMF=5.3 and 2.1, respectively), and are probably well adapted to stabilizing the carpus during the stance phase of gait. In contrast, the flexor carpi radialis muscle displayed long fibers (89.7 mm), low peak isometric force (Fmax=555 N), and high stiffness (LT:LMF=1.6). Due to its long fibers and low Fmax, flexor carpi radialis appears to be better adapted to flexion and extension of the limb during the swing phase of gait than to stabilization of the carpus during stance. Including muscle architectural parameters in a musculoskeletal model of the equine distal forelimb may lead to more realistic estimates not only of the magnitudes of muscle forces, but also of the distribution of forces among the muscles crossing any given joint.     

Predicting Rotator Cuff Tears Using Data Mining and Bayesian Likelihood Ratios

Objectives

Rotator cuff tear is a common cause of shoulder diseases. Correct diagnosis of rotator cuff tears can save patients from further invasive, costly and painful tests. This study used predictive data mining and Bayesian theory to improve the accuracy of diagnosing rotator cuff tears by clinical examination alone.

Methods

In this retrospective study, 169 patients who had a preliminary diagnosis of rotator cuff tear on the basis of clinical evaluation followed by confirmatory MRI between 2007 and 2011 were identified. MRI was used as a reference standard to classify rotator cuff tears. The predictor variable was the clinical assessment results, which consisted of 16 attributes. This study employed 2 data mining methods (ANN and the decision tree) and a statistical method (logistic regression) to classify the rotator cuff diagnosis into “tear” and “no tear” groups. Likelihood ratio and Bayesian theory were applied to estimate the probability of rotator cuff tears based on the results of the prediction models.

Results

Our proposed data mining procedures outperformed the classic statistical method. The correction rate, sensitivity, specificity and area under the ROC curve of predicting a rotator cuff tear were statistical better in the ANN and decision tree models compared to logistic regression. Based on likelihood ratios derived from our prediction models, Fagan''s nomogram could be constructed to assess the probability of a patient who has a rotator cuff tear using a pretest probability and a prediction result (tear or no tear).

Conclusions

Our predictive data mining models, combined with likelihood ratios and Bayesian theory, appear to be good tools to classify rotator cuff tears as well as determine the probability of the presence of the disease to enhance diagnostic decision making for rotator cuff tears.     

Mechanical,histological, and functional properties remain inferior in conservatively treated Achilles tendons in rodents: Long term evaluation

Conservative treatment (non-operative) of Achilles tendon ruptures is suggested to produce equivalent capacity for return to function; however, long term results and the role of return to activity (RTA) for this treatment paradigm remain unclear. Therefore, the objective of this study was to evaluate the long term response of conservatively treated Achilles tendons in rodents with varied RTA. Sprague Dawley rats (n = 32) received unilateral blunt transection of the Achilles tendon followed by randomization into groups that returned to activity after 1-week (RTA1) or 3-weeks (RTA3) of limb casting in plantarflexion, before being euthanized at 16-weeks post-injury. Uninjured age-matched control animals were used as a control group (n = 10). Limb function, passive joint mechanics, tendon properties (mechanical, histological), and muscle properties (histological, immunohistochemical) were evaluated. Results showed that although hindlimb ground reaction forces and range of motion returned to baseline levels by 16-weeks post-injury regardless of RTA, ankle joint stiffness remained altered. RTA1 and RTA3 groups both exhibited no differences in fatigue properties; however, the secant modulus, hysteresis, and laxity were inferior compared to uninjured age-matched control tendons. Despite these changes, tendons 16-weeks post-injury achieved secant stiffness levels of uninjured tendons. RTA1 and RTA3 groups had no differences in histological properties, but had higher cell numbers compared to control tendons. No changes in gastrocnemius fiber size or type in the superficial or deep regions were detected, except for type 2x fiber fraction. Together, this work highlights RTA-dependent deficits in limb function and tissue-level properties in long-term Achilles tendon and muscle healing.     

Proteomics Perspectives in Rotator Cuff Research: A Systematic Review of Gene Expression and Protein Composition in Human Tendinopathy

Background

Rotator cuff tendinopathy including tears is a cause of significant morbidity. The molecular pathogenesis of the disorder is largely unknown. This review aimed to present an overview of the literature on gene expression and protein composition in human rotator cuff tendinopathy and other tendinopathies, and to evaluate perspectives of proteomics – the comprehensive study of protein composition - in tendon research.

Materials and Methods

We conducted a systematic search of the literature published between 1 January 1990 and 18 December 2012 in PubMed, Embase, and Web of Science. We included studies on objectively quantified differential gene expression and/or protein composition in human rotator cuff tendinopathy and other tendinopathies as compared to control tissue.

Results

We identified 2199 studies, of which 54 were included; 25 studies focussed on rotator cuff or biceps tendinopathy. Most of the included studies quantified prespecified mRNA molecules and proteins using polymerase chain reactions and immunoassays, respectively. There was a tendency towards an increase of collagen I (11 of 15 studies) and III (13 of 14), metalloproteinase (MMP)-1 (6 of 12), -9 (7 of 7), -13 (4 of 7), tissue inhibitor of metalloproteinase (TIMP)-1 (4 of 7), and vascular endothelial growth factor (4 of 7), and a decrease in MMP-3 (10 of 12). Fourteen proteomics studies of tendon tissues/cells failed inclusion, mostly because they were conducted in animals or in vitro.

Conclusions

Based on methods, which only allowed simultaneous quantification of a limited number of prespecified mRNA molecules or proteins, several proteins appeared to be differentially expressed/represented in rotator cuff tendinopathy and other tendinopathies. No proteomics studies fulfilled our inclusion criteria, although proteomics technologies may be a way to identify protein profiles (including non-prespecified proteins) that characterise specific tendon disorders or stages of tendinopathy. Thus, our results suggested an untapped potential for proteomics in tendon research.     

What humeri are suitable for comparative testing of suture anchors? An ultrastructural bone analysis and biomechanical study of ovine,bovine and human humeri and four different anchor types

For testing of fixation devices such as suture anchors used in rotator cuff repair often animal bones are used. They are easily obtained, inexpensive and some have been found to be similar to human bone. But can we rely on the results drawn from these studies in our daily surgical practice?The purpose of this study was to compare the trabecular bone mineral density, the trabecular bone volume fraction and the cortical layer thickness in the greater tubercle in different species to evaluate their influence on primary stability of suture anchors under a cyclic loading protocol representing the physiologic forces placed on rotator cuff repairs in vivo.Bovine and ovine humeri are not suitable for suture anchor testing. The statistical significances for pullout forces between the anchors varied from species to species. Therefore, no very applicable information can be obtained from testing suture anchors in ovine or bovine humeri with regard to ultimate failure loads in human humeri. The ultimate failure load seems to depend mainly on the cortical thickness and on the subcortical trabecular bone quality.     

肩袖间隙影像解剖及常见病变的研究进展

肩袖间隙在解剖学上是肩关节的一个复合区域,在维持肩关节稳定性和保护肱二头肌长头肌腱功能起重要作用。对肩袖间隙解剖结构及功能的深入认识有助于肩袖间隙损伤性病变、挛缩性病变等的及时诊断和合理治疗。影像学检查尤其是磁共振逐步成为肩袖间隙疾病最主要的检查方法,包括常规扫描、直接及间接性磁共振肩关节造影、增强扫描等。本文将就肩袖间隙的影像解剖及常见病变的相关研究进行综述。     

Not so fast: Speed effects on forelimb kinematics in cercopithecine monkeys and implications for digitigrade postures in primates

Terrestrial mammals are characterized by their digitigrade limb postures, which are proposed to increase effective limb length (ELL) to achieve preferred or higher locomotor speeds more efficiently. Accordingly, digitigrade postures are associated with cursorial locomotion. Unlike most medium‐ to large‐sized terrestrial mammals, terrestrial cercopithecine monkeys lack most cursorial adaptations, but still adopt digitigrade hand postures. This study investigates when and why terrestrial cercopithecine monkeys adopt digitigrade hand postures during quadrupedal locomotion. Three cercopithecine species (Papio anubis, Macaca mulatta, Erythrocebus patas) were videotaped moving unrestrained along a horizontal runway at a range of speeds (0.4–3.4 m/s). Three‐dimensional forelimb kinematic data were recorded during forelimb support. Hand posture was measured as the angle between the metacarpal segments and the ground (MGA). As predicted, a larger MGA was correlated with a longer ELL. At slower speeds, subjects used digitigrade postures (larger MGA), however, contrary to expectations, all subjects used more palmigrade hand postures (smaller MGA) at faster speeds. Digitigrade postures at slower speeds may lower cost of transport by increasing ELL and step lengths. At higher speeds, palmigrade postures may be better suited to spread out high ground reaction forces across a larger portion of the hand thereby potentially decreasing stresses in hand bones. It is concluded that a digitigrade forelimb posture in primates is not an adaptation for high speed locomotion. Accordingly, digitigrady may have evolved for different reasons in primates compared to other mammalian lineages. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.