Calcific tendinitis of the biceps-labral complex: a rare cause of acute shoulder pain

Calcific tendinitis most commonly affects the rotator cuff and has not been previously reported affecting the biceps-labral complex. We report a case of calcific tendinitis of the biceps-labral complex attachment, a rare cause of acute, severe shoulder pain. Clinically, it can be misdiagnosed as supraspinatus tendinitis or septic arthritis of the shoulder joint. Non-operative treatment failed to resolve the symptoms. Arthroscopic debridement of the calcific deposit resulted in resolution of symptoms. Knowledge of this clinical condition and its imaging features is crucial for a correct diagnosis of this uncommon cause of shoulder pain.     

Acute acalculous cholecystitis in patients submitted to severe surgical stress

Acute acalculous cholecystitis in critically ill surgical patients is a clinical entity whose features are more and more clearly identified. Numerous conditions have been correlated with its onset (multiple transfusions, narcotic analgesics, total parenteral nutrition, mechanical ventilation with positive end pressure, major traumas and burns, dehydration and many more). The Authors reporting their experience in five cases envisage the multifactoriality of etiology, emphasize the significance of a timely suspicion and the role of ultrasonography as the most useful implements in the assessment of this disease.     

Biomechanical properties of the sacroiliac joint

The purpose of this study was to investigate the biomechanical properties of the bony and cartilagenous elements of the sacroiliac joint. The materials were obtained from human fresh cadavers en bloc, and they were analysed on cartilage thickness, dynamic viscoelasticity, static compressive strength, and bony trabecular structure. The results were as follows: Cartilage thickness of the joint was well correlated with viscoelasticity, and the results of viscoelasticity and static compressive strength were highly equivalent to the results of analysis of the trabecular bone. The values of viscoelasticity, static compressive strength and bone area were higher in the iliac side of the joint than in the sacral side, and markedly high values were obtained in the middle part of the iliac side. In conclusion, the middle part of the sacroiliac joint may play an important role in the support and transmission of the load.     

颈椎终板抗压强度分布规律的生物力学研究

[目的]研究颈椎终板不同位点抗压强度及其分布规律。[方法]选用5具成年男性新鲜颈椎标本(C3～7),共25个椎体50个终板。对终板平面49个测试点用直径1.5 mm的平底压头以12 mm/min的速度进行连续压缩加载试验,获得最大压缩力,进行统计分析。[结果](1)抗压强度自C3～7逐渐减小(P﹤0.05);(2)下终板抗压强度大于上终板(P=0.000);(3)椎间隙相邻面上一椎体下终板的抗压强度大于下一椎体上终板抗压强度(P<0.05);(4)随着压力点逐渐外移,抗压强度逐渐增大(P﹤0.05);(5)处于不同角度的压力点,其抗压强度存在差异(P=0.029);(6)终板后部强于前部(P=0.003)。上终板后部抗压强度大于前部(P=0.000)。[结论]颈椎终板抗压强度自C3～7逐渐减小,下终板强于上终板,外周大于中央,后部强于前部。椎间隙相邻面上一椎体下终板的抗压强度大于下一椎体上终板抗压强度。     

Biomechanical analysis of the foot and ankle for predisposition to developing stress fractures

Forty-seven subjects were studied to discover predisposing factors for their radiologically diagnosed metatarsal stress fractures. Biomechanics of the foot and ankle were introduced to help explain forefoot varus, abnormal rearfoot valgus, and dorsiflexion as intervening variables in metatarsal stress fracture development. Results concluded that subjects with forefoot varus and decreased dorsiflexion had 8.3: 1 and 4.6: 1, respectively, odds of developing a metatarsal stress fracture. Abnormal rearfoot valgus had no significant effect on predisposing the subjects to develop a stress fracture. J Orthop Sports Phys Ther 1985;7(3):96-101.     

颈脊膜脊髓受压的生物力学分析

本实验采用新鲜成年尸体完整脊柱７具，以小型压力传感器模拟颈椎外伤后颈脊膜脊髓受压，观察不同致压深度下颈脊膜脊髓的受压程度，并对脊髓受压状态下的应力分布和变化规律进行分析。结果表明。颈脊膜脊髓受压时脊髓承受复杂应力：受压产生的剪力在脊髓中央最大；压力主要局限于颈脊膜脊髓前部。椎板切除对来自脊髓前方的压迫无明显减压作用。     

腰骶椎终板生物力学特性的实验研究

目的:研究腰骶椎终板不同位点的生物力学特性及其分布规律。方法:选用成人新鲜尸体腰骶椎标本(L1～S1)5具,共30个椎体55个终板,应用电子万能实验机(型号CSS-2205)对终板平面49个测试点用直径1.5mm的平底压头以12mm/min的速度进行连续压缩加载实验,记录最大压缩力,并对数据进行统计分析。结果:(1)L1～S1上终板最大压缩力从68.81±8.12N增加至120.41±34.33N,各节段间差异有显著性(P<0.05);L1～L4下终板最大压缩力从78.66±5.57N增加至120.44±29.27,L5降为106.65±16.10N,各节段间差异有显著性(P<0.05)。(2)L1～S1上终板中央至外周最大压缩力从65.02±6.40N增加至110.61±10.63N,下终板中央至外周最大压缩力从68.09±9.43N增加至162.69±16.46N,差异有显著性(P<0.05);上终板前侧最大压缩力为87.30±6.42N,后侧为89.25±14.30N,下终板前侧最大压缩力107.63±4.84N,后侧最大压缩力109.82±18.66N,差异均无显著性(P>0.05)。(3)L3/4、L4/5上下终板的最大压缩力的差异均有显著性(P<0.05),余间隙差异无显著性。结论:L1～S1上终板强度逐渐增大;L1～L4下终板强度逐渐增大,L4～L5减小;腰骶椎上、下终板强度从中央至外周逐渐增大,前、后侧无差异;L3/4、L4/5间隙上位椎体下终板强度大于下位椎体上终板。     

Biomechanical properties of heat-treated bone grafts

Introduction A possible critical complication associated with banking bone is human immunodeficiency virus (HIV) infection. Recently, since the report of HIV infection in bone allografts from an HIV-seronegative donor, a more reliable method of sterilization for preserved bone graft has become necessary. Heat treatment of banking bone is one of the simple sterilization methods. This method is especially safe and practical for the prevention of HIV infection.Materials and methods We previously reported a biological study on heat-treated bone graft. In that study, we showed that revascularization and new bone formation of bone graft after heat treatment at 60°C was nearly the same as that of non-heat-treated bone graft, while at 100°C, revascularization and new bone formation showed a significant delay. This time, we examined the change of mechanical strength of heat-treated bone grafts after transplantation in an experiment. To eliminate the problem of antigenicity of grafted bone, we used autografts, not allografts. Two types of heat-treated autografts were employed: heat-treated at 60°C for 30 min and heat-treated at 100°C for 5 min; as a control, fresh autografts were replaced in the left femur of rabbits. A strength test was performed for both the transplanted bone and the untreated intact right femur with time after transplantation. The strength test consisted of a compression test and torsional test, and the strength was compared between transplanted bone and the untreated intact right femur.Results In the compression test, the grafts heat-treated at 60°C showed a strength ratio before transplantation of 97.3%. The strength ratio decreased to 63.5% at 18 weeks after transplantation. Then the strength ratio increased and recovered to 94.5% at 48 weeks after transplantation. However, the grafts heat-treated at 100°C showed unsatisfactory mechanical strength, at 48 weeks the strength ratio was 60.1%, which was significantly lower compared with controls. In the torsional test, the grafts heat-treated at 60°C showed almost the same strength observed in the compression test. However, the grafts heat-treated at 100°C showed unsatisfactory mechanical strength: at 48 weeks, the strength ratio was 57.3%.Conclusion Therefore, heat treatment at 60°C is a useful sterilization method, not only in biological but also mechanical terms.     

Growth-plate cartilage metabolic response to mechanical stress

An in vitro study assessing the metabolic response of growth-plate cartilage explants to mechanical stress was performed. Cultured explants were exposed to two types of stress: (a) single high-compressive force (SHC), and (b) multiple intermittent low-compressive force (MILC). Proliferative activity and matrix synthesis were determined with liquid scintillation counting after explants were labeled with [3H]thymidine and [35S]-sulfate. Our in vitro findings suggest that too high a force, even acting for a short time, may result in permanent injury of growth plate cartilage. Hence, we hypothesized that there might be an unknown pathogenetic mechanism of Salter's fifth-type epiphyseal injury. We report the results of our study.     

Podocytes respond to mechanical stress in vitro

Glomerular capillary pressure is thought to affect the structure and function of glomerular cells. However, it is unknown whether podocytes are intrinsically sensitive to mechanical forces. In the present study, differentiated mouse podocytes were cultured on flexible silicone membranes. Biaxial cyclic stress (0.5 Hz and 5% linear strain) was applied to the membranes for up to 3 d. Mechanical stress reduced the size of podocyte cell bodies, and processes became thin and elongated. Podocytes did not align in the inhomogeneous force field. Whereas the network of microtubules and that of the intermediate filament vimentin exhibited no major changes, mechanical stress induced a reversible reorganization of the actin cytoskeleton: transversal stress fibers (SF) disappeared and radial SF that were connected to an actin-rich center (ARC) formed. Epithelial and fibroblast cell lines did not exhibit a comparable stress-induced reorganization of the F-actin. Confocal and electron microscopy revealed an ellipsoidal and dense filamentous structure of the ARC. Myosin II, alpha-actinin, and the podocyte-specific protein synaptopodin were present in radial SF, but, opposite to F-actin, they were not enriched in the ARC. The formation of the ARC and of radial SF in response to mechanical stress was inhibited by nonspecific blockade of Ca(2+) influx with Ni(2+) (1 mM), by Rho kinase inhibition with Y-27632 (10 microM), but not by inhibition of stretch-activated cation channels with Gd(3+) (50 microM). In summary, mechanical stress induces a unique reorganization of the actin cytoskeleton in podocytes, featuring radial SF and an ARC, which differ in protein composition. The F-actin reorganization in response to mechanical stress depends on Ca(2+) influx and Rho kinase. The present study provides the first direct evidence that podocytes are mechanosensitive.     

The influence of mechanical properties on wall stress and distensibility of the dilated ascending aorta

OBJECTIVES: We sought to determine how intrinsic mechanical properties of dilated ascending aorta influence in vivo distensibility and wall stress, potential contributing factors to the risk of aortic rupture and dissection. METHODS: Fresh tissue from patients undergoing ascending aortic replacement for Marfan syndrome (n = 8, age 38 +/- 14 years), bicuspid aortic valve with associated aneurysm (n = 20, age 55 +/- 12 years), or idiopathic degenerative aneurysm (n = 7, age 64 +/- 9 years) was analyzed for elastic properties and circumferential residual stress. Histologic specimens were graded for elastin fragmentation, cystic changes, fibrosis, and necrosis. Distensibility and wall stresses were predicted with a cylindrical mathematical model of the aorta. RESULTS: Elastic properties of aortic tissue were nonlinear and extensibility decreased with age. Moderate or severe elastin fragmentation was prevalent in tissue from patients with the Marfan syndrome and more common in tissue from younger patients. Model-predicted mean circumferential stress did not vary significantly with age or patient group, but increased with aortic lumen diameter and systolic blood pressure. Model-predicted distensibility decreased with age in bicuspid aortic valve and degenerative aneurysm groups. Differences in distensibility were correlated with differences in elastic properties. CONCLUSIONS: The age dependence of elastic properties of dilated ascending aorta is consistent with that of normal aorta observed in previous studies. Increases in mean circumferential stress with blood pressure and diameter support the clinical importance of blood pressure control and serial evaluation of aortic diameter. Declining wall strength with age may increase the risk of rupture or dissection.     

Biomechanical properties of the plantar flexor muscle–tendon complex 6 months post‐rupture of the achilles tendon

We compared the effects of a non‐weight bearing protocol (NWB) and a weight bearing (WB) protocol on energy stored, stiffness, and shock absorption in the plantar flexor muscle–tendon unit of patients managed non‐operatively following an Achilles tendon rupture. Thirty‐eight subjects were randomized to a WB cast fitted with a Bohler iron or a traditional non‐weight‐bearing cast. At a 6‐month follow‐up, a biomechanical assessment utilizing an isokinetic dynamometer allowed measurement of peak passive torque, energy stored, shock absorption, and stiffness. The WB group had greater peak passive torque (～20%). Irrespective of group, peak passive torque in unaffected legs was greater (～26%) than affected legs. Across the groups, energy stored in the NWB group was 74% of the WB group. The energy stored in affected legs was 80% of that in unaffected legs. Shock absorption was not significantly different across legs or groups. Irrespective of group, affected legs had significantly less stiffness (20–40%). While the augmentation of plaster with a Bohler iron to allow increased weight bearing had positive effects, deficits in affected compared to unaffected legs irrespective of group were notable, and should be addressed prior to participation in vigorous physical activities. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1469–1474, 2013     

Biomechanical properties of splint materials while curing

Many studies have evaluated splint strength at maturity with multiple splint materials, methods, and configurations but none have analyzed splints as they cure. The purpose of this study is to evaluate the properties of different splint materials immediately following activation and as they mature.Splints were dipped for three seconds in two temperatures of water and an additional group of fiberglass with no water was tested as well. Splint weight was taken as an additional measurement to assure homogenous groups. All splints were tested in three-point bending at a constant displacement.The generalized linear model (GLM) including all time frames showed differences in yield load and ultimate loads after three minutes. All ultimate loads occurred at greater than 20° of angulation. Plaster had a much lower displacement at its yield load at all times after 3 min. Plaster had a higher stiffness at 1° of angulation at all time points after six minutes. The GLM that excluded the three-day time showed that the higher temperature increased initial stiffness in the splints at three and six minutes.Fiberglass has a higher yield point and ultimate load when compared to plaster. However, these loads were measured at significant splint angulation for the fiberglass, suggesting that plaster is acting as a true splint. Fiberglass is stronger and faster to cure than plaster. In situations where the surgeon desires the strongest splint, fiberglass may be preferable. However, the initial stiffness of plaster is superior to fiberglass.     

Biomechanical effects of stress shielding of the rabbit patellar tendon depend on the degree of stress reduction

A rabbit model was used to discover whether the effects of stress shielding on the mechanical properties of the patellar tendon depend on the degree of stress reduction. Ninety mature female Japanese White rabbits were divided into three groups: completely stress-shielded, partially stress-shielded, and shamoperation and contralateral controls. In the experimental groups, tension applied to the patellar tendon was 0%, approximately 30%, and 100%, of the normal tension, respectively, with a polyester artificial ligament. Tensile tests were carried out on patella-patellar tendon-tibia complexes harvested 1, 2, 3, 6, or 12 weeks after surgery. The tensile strength decreased in comparison with the sham-operation group to 50.2, 13.5, 9.7, and 20.7% in the completely stress-shielded group and to 75.2, 57.6, 59.6, 57.3, and 72.9% in the partially stress-shielded group. The tensile strength in the completely stress-shielded group was significantly less than that in the partially stress-shielded group at 1, 2, 3, and 6 weeks. The cross-sectional area of the patellar tendon significantly increased to 132, 206, 237, and 136% in the completely stress-shielded group and to 136, 170, 175, 155, and 127% in the partially stress-shielded group, compared with the sham-operation group. The cross-sectional area of the completely stress-shielded tendon was significantly larger than that of the partially stress-shielded tendon at 1, 2, and 3 weeks. This study demonstrated that effects of stress shielding on the mechanical properties of the patellar tendon were dependent on the degree of stress shielding.