Comparison of pullout strength of small-diameter cannulated and solid-core screws

The purpose of this study was to determine the difference in pullout strength between cannulated and solid-core small-diameter bone screws. Cannulated screws from different manufacturers were compared against solid-core screws with 2.0-mm, 2.4-/2.5-mm, and 3.0-mm diameters. A synthetic material made to simulate bicortical bone was used as the test medium. The screws were extracted under servohydraulic control. There was no statistically significant difference between any of the cannulated and solid-core 2.0-mm screws used in this study (P < .05). In the 2.4-/2.5-mm screw tests, both of the cannulated screw designs had a significantly higher pullout strength when compared with the solid-core screw (P < .05). In the testing of 3.0-mm screw test, 1 of the cannulated screw designs showed a significantly higher pullout strength than the other cannulated and solid-core screws that were tested (P < .05). The results of this study suggest that small-diameter cannulated bone screws are similar in mechanical pullout strength to solid-core screws.     

pQCT bone strength index may serve as a better predictor than bone mineral density for long bone breaking strength

Bone mineral density (BMD) is commonly used to predict osteoporotic fracture risk without considering the geometry of the bone. However, geometric parameters are also important in determination of bone strength. An index including both material and geometric properties may be therefore more relevant in prediction of fracture risk. We studied the correlation between parameters measured by noninvasive peripheral quantitative computed tomography (pQCT) and bone bending strength of the diaphysis of 45 fresh goat humeri and 27 femora. Multislice pQCT was used for measuring volumetric diaphyseal cortical BMD, total BMD, diaphyseal and cortical cross-sectional area (CSA), and cross-sectional moment of inertia (CSMI) and their derived bone strength indices (BSIs), including BSI_CSMI (cortical BMD × CSMI) and BSI_CSA (cortical BMD × cortical CSA). Conventional dual-energy absorptiometry (DXA) was also conducted to measure areal BMD of diaphysis for comparison. Ultimate fracture load was obtained via three-point bending test. Results showed that for femora, fracture load was correlated better with BSI_CSA (r = 0.697, P 0.001) than cortical BMD (r = 0.304, P 0.05) and total BMD (r = 0.387, P 0.05) measured using pQCT and areal BMD (r = 0.612, P 0.001) measured using DXA. For humeri, fracture load was also correlated with BSI_CSA (r = 0.579, P 0.001) but not with other pQCT parameters including cortical BMD and total BMD (r = 0.282 and 0.305, respectively; P 0.05, both). The best correlation was found with areal BMD measured by DXA (r = 0.760, P 0.001). In conclusion, pQCT noninvasive BSI_CSA derived from cortical BMD (material) and its cortical CSA (bone geometry or distribution) may serve as an important noninvasive index for predicting long bone bending strength. The bending strength was also predicted by bone mass (areal BMD) measured by DXA, an integration of bone mineral and geometry. Further clinical studies are needed to validate the predictive value of BSI in long bone osteoporotic fracture.     

Bone architecture and disc degeneration in the lumbar spine of mice lacking GDF-8 (myostatin).

GDF-8, also known as myostatin, is a member of the transforming growth factor-beta superfamily of secreted growth and differentiation factors that is expressed in vertebrate skeletal muscle. Myostatin functions as a negative regulator of skeletal muscle growth and myostatin null mice show a doubling of muscle mass compared to normal mice. We describe here morphology of the lumbar spine in myostatin knockout (Mstn(-/-)) mice using histological and densitometric techniques. The Mstn(-/-) mice examined in this study weigh approximately 10% more than controls (p<0.001) but the iliopsoas muscle is over 50% larger in the knockout mice than in wild-type mice (p<0.001). Peripheral quantitative computed tomography (pQCT) data from the fifth lumbar vertebra show that mice lacking myostatin have approximately 50% greater trabecular bone mineral density (p=0.001) and significantly greater cortical bone mineral content than normal mice. Toluidine blue staining of the intervertebral disc between L4-L5 reveals loss of proteoglycan staining in the hyaline end plates and inner annulus fibrosus of the knockout mice. Loss of cartilage staining in the caudal end plate of L4 is due to ossification of the end plate in the myostatin-deficient animals. Results from this study suggest that increased muscle mass in mice lacking myostatin is associated with increased bone mass as well as degenerative changes in the intervertebral disc.     

Prevention of hamstring strains in elite soccer: an intervention study

The purpose was to test the effect of eccentric strength training and flexibility training on the incidence of hamstring strains in soccer. Hamstring strains and player exposure were registered prospectively during four consecutive soccer seasons (1999-2002) for 17-30 elite soccer teams from Iceland and Norway. The first two seasons were used as baseline, while intervention programs consisting of warm-up stretching, flexibility and/or eccentric strength training were introduced during the 2001 and 2002 seasons. During the intervention seasons, 48% of the teams selected to use the intervention programs. There was no difference in the incidence of hamstring strains between teams that used the flexibility training program and those who did not [relative risk (RR)=1.53, P=0.22], nor was there a difference compared with the baseline data (RR=0.89, P=0.75). The incidence of hamstring strains was lower in teams who used the eccentric training program compared with teams that did not use the program (RR=0.43, P=0.01), as well as compared with baseline data for the same intervention teams (RR=0.42, P=0.009). Eccentric strength training with Nordic hamstring lowers combined with warm-up stretching appears to reduce the risk of hamstring strains, while no effect was detected from flexibility training alone. These results should be verified in randomized clinical trials.     

提高斜形损伤肌腱缝合强度的实验研究

目的探讨提高斜形肌腱损伤修复强度的有效方法。方法40根猪跖深屈肌腱按照切割方向及两端缝合距离随机分为4组:第1组肌腱为横形损伤,中心缝合边距为10mm;第2、3、4组肌腱为45°斜形损伤,中心缝合边距分别为4mm、7mm、10mm,10根肌腱,各组均采用改良Kessler法缝合。分别检测缝合肌腱的2mm间隙形成负荷、最大抗张强度及最大功耗,并采用ANOVA法进行统计分析。结果肌腱斜形损伤修复的强度显著低于用等长距离(20mm)缝合的横行损伤修复的强度(P<0.01),当其短边的缝合边距由4mm增大到7mm时,其修复的强度显著增大(P<0.01),但当短边的缝合边距增大到10mm时,其抗张强度与短边的缝合边距7mm相比增加不显著。结论在肌腱斜形损伤时,延长中心缝合边距是一种有效的提高肌腱修复强度的方法。     

亚麻籽胶的胶凝性质

采用流变学法测定了亚麻籽胶溶液的胶凝点、熔化点，并采用质构仪、扫描电镜和原子力显微镜等手段研究了影响亚麻籽胶凝胶强度的因素，结果表明亚麻籽胶具有胶凝性，它能形成一种热可逆的冷致凝胶，亚麻籽胶溶液的胶凝点低于其凝胶的熔化点，且亚麻籽胶溶液的胶凝点及其凝胶的熔化点均随冷却的起始温度的升高而升高。亚麻籽胶浓度、溶解温度、pH、NaCl、CaCl2及复合磷酸盐能影响亚麻籽胶的凝胶强度，亚麻籽胶的凝胶强度随着浓度的增加及溶解温度的升高而增强；在pH6～9的范围内，亚麻籽胶的凝胶强度达到最大；NaCl和复合磷酸盐可以降低亚麻籽胶的凝胶强度，低浓度（〈0．3％）的CaCl2可以增强亚麻籽胶的凝胶强度，而高质量分数（〉0．3％）的CaCl2能降低亚麻籽胶的凝胶强度。     

Magnitude of Deformity Correction May Influence Recovery of Quadriceps Strength After Total Knee Arthroplasty

Background

Malalignment of the lower extremity is commonly seen in patients with severe osteoarthritis undergoing total knee arthroplasty (TKA) and is believed to play a role in quadriceps strength loss. Deformity correction is typically achieved through surgical techniques to provide appropriate ligamentous balancing. Therefore, this study examined the influence of change in lower extremity alignment on quadriceps strength outcomes after TKA.

Grip strength in children after non-severe burn injury

PurposeTo characterise grip strength in children with non-severe burn injury, and further understanding of how demographic and clinical variables impact musculoskeletal recovery.MethodsA retrospective, cross-sectional audit of routinely collected clinical data was performed. Standardised protocols were used to measure height, weight and grip strength. Demographic and clinical information was collected from patient medical records. Grip strength comparisons were made against normative data using paired t-tests. General linear regressions with backwards elimination were performed to assess impact of clinical, demographic and physical variables on grip strength.ResultsChildren who were right hand (RH) dominant had reduced RH (18.9 ± 9.9 kg, p = 0.001) and left hand (LH)(17.6 ± 9.3 kg, p = 0.027) grip strength compared to age, sex and hand-dominance matched norms (RH, 20.0 ± 10.0 kg; LH, 18.4 ± 9.5 kg). Children who were assessed closer to the time of their injury, and those who were burnt at a young age were more likely to score grip strength values below the norm (p < 0.001 for all analyses). In particular, females appeared to be at a higher risk of low grip strength scores if burnt at a young age (p < 0.001).ConclusionsChildren with non-severe burn injury struggle to recover musculoskeletal strength, with those who were assessed closer to the time of injury or burnt at a young age especially at risk of impaired grip strength performance. Grip strength does not appear to be influenced by any other clinical variables or burn injury characteristics.     

社区老年高血压患者衰弱的动态列线图风险预测模型构建

目的 构建动态列线图预测模型,分析社区老年高血压患者衰弱的影响因素,为制定针对性的干预措施提供参考。方法 从中国健康与养老追踪调查随访数据库中提取高血压患者信息,以7∶3比例随机分为训练集(n=1 160)与验证集(n=494)。采用Lasso法筛选最佳预测变量,使用logistic回归模型分析高血压患者衰弱影响因素,并构建动态列线图。使用ROC曲线的曲线下面积、Hosmer-Lemeshow检验、校准曲线和决策曲线分析评估列线图的预测性能。结果 共筛选出1 654例老年高血压患者,其中560例(33.86%)并发衰弱。受教育程度、握力、BMI、抑郁、认知障碍、自评健康、代谢性疾病、心脑血管疾病、呼吸系统疾病、胃肠道疾病10个变量纳入预测模型。预测模型在训练集和验证集的ROC曲线下面积分别为0.883(95%CI为0.863～0.903)和0.887(95%CI为0.857～0.916);Hosmer-Lemeshow检验值分别为P=0.825和P=0.410;校准曲线显示预测值和实际值之间存在显著一致性。决策曲线分析显示该模型具有良好的净效益和预测准确性。结论 动态列线图具有良好预测...