椎体成形术中骨水泥量对椎体机械性能的实验研究

目的探讨聚甲基丙烯酸甲酯(PMMA)和自固化磷酸钙骨水泥(CPC)的不同用量对骨质疏松性椎体强度和硬度的影响,明确恢复椎体强度及硬度所需的最小骨水泥用量。方法取5具老年女性(65～73岁)48个脊椎标本(T6～L3),分解后压缩并测量其强度和硬度,将3、5、7ml PMMA和CPC注入压缩后的椎体,再测其强度和硬度,并与原来的强度和硬度进行比较。结果所有椎体注入骨水泥后强度都得到恢复,注入5ml、7ml骨水泥后强度明显增加;注入PMMA后硬度都得到恢复,而注入CPC 5ml、7ml才能恢复椎体硬度。结论骨质疏松性椎体骨折后,注入骨水泥可有效恢复椎体的强度和硬度,此结果可有利于指导椎体成形术的临床应用。     

CONTRALATERAL EFFECTS OF DISINHIBITORY TENS ON QUADRICEPS FUNCTION IN PEOPLE WITH KNEE OSTEOARTHRITIS FOLLOWING UNILATERAL TREATMENT

Background:

Quadriceps activation failure is common in patients with tibiofemoral osteoarthritis (TFOA) and has been reported to occur bilaterally following acute and chronic knee injuries. Sensory transcutaneous electrical stimulation (TENS) applied to the knee has increased ipsilateral quadriceps activation, yet it remains unknown if repeated sensory TENS treatments affect activation in the contralateral quadriceps.

Objective:

To determine the effects of unilateral TENS treatment to the involved leg, in conjunction with 4-weeks of therapeutic exercise, on volitional quadriceps activation in the contralateral leg.

Methods:

Thirty-three patients with radiographically diagnosed TFOA were randomly assigned to the TENS, placebo, and the control groups. The involved leg was defined as the knee with highest degree of radiographically assessed TFOA. All participants completed a supervised 4-week lower extremity exercise program for the involved leg only. TENS and placebo TENS were worn throughout the rehabilitation sessions as well as during daily activities for those groups on the involved leg. Quadriceps central activation ratio (CAR), a measure of volitional muscular activation, was assessed in the uninvolved leg at baseline, 2-weeks and 4-weeks following the initiation of the intervention.

Results:

There were no differences between groups for quadriceps CAR (P=0.3).

Discussion:

Although significant differences were not found, strong to moderate within group effect sizes were calculated for the TENS group at 2 (d = .87) and 4 weeks (d = .54), suggesting that significant differences may be found in a larger population.

Conclusions:

Contralateral quadriceps CAR was not affected following a 4-week unilateral disinhibitory intervention in this sample.     

The effects of sodium fluoride on bone breaking strength

The therapeutic use of sodium fluoride has been recommended in a variety of osteopenic bone diseases. The recommendations are based mainly on the known osteosclerotic effects of sodium fluoride and little information is available as to its effect on bone strength. The influence of various concentrations of sodium fluoride on bone strength in growing rats on high and low calcium diets was studied. The administration of sodium fluoride increased bone diameter, indicating stimulation of periosteal bone formation, but bone strength was reduced or not affected by fluoride ingestion.

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Zusammenfassung Die therapeutische Verwendung von Natriumfluorid ist für eine Anzahl von Knochenmangel-Krankheiten empfohlen worden. Die Empfehlungen basieren hauptsächlich auf den bekannten osteosklerotischen Wirkungen von Natriumfluorid; über dessen Effekt auf die Knochenstärke ist wenig bekannt. In dieser Arbeit wurde der Einfluß verschiedener Konzentrationen von Natriumfluorid auf die Knochenstärken von wachsenden Ratten mit hoher und niederer Calciumeinnahme untersucht. Die Verabreichung von Natriumfluorid erhöhte den Knochendurchmesser, was auf eine Stimulierung der Periostbildung hinwies, die Knochenstärke wurde jedoch durch Fluorideinnahme herabgesetzt oder nicht beeinflußt.

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Résumé L'utilisation thérapeutique de fluorure de sodium a été recommandée dans le traitement de diverses maladies osseuses ostéopéniques. Cet emploi est basé principalement sur les effects ostéosclérotiques bien connus du fluorure de sodium, mais on connait mal son effet sur la force de résistance osseuse. L'influence de diverses concentrations de fluorure de sodium sur la force de résistance osseuse de jeunes rats soumis à des régimes riches et pauvres en calcium a été étudiée. L'administration de fluorure de sodium augmente le diamètre osseux, indiquant une stimulation de la formation de l'os périosté, mais la force de résistance osseuse est réduite ou non modifiée par l'ingestion de fluor.

     

提高铸造陶瓷全冠粘接强度的研究

为考察不同粘接剂对Ｐｌａｔ－Ⅱ型铸造陶瓷全冠粘接于牙体后的整体强度的影响，选用Ｐａｎａｖｉａ２１树脂粘接剂和Ｐｏｒｃｅｌｉｔｅｄｕａｌｃｕｒｅｃｅｍｅｎｔ树脂粘接剂，分别检测粘接后试件的破坏载荷。结果表明：Ｐａｎａｖｉａ２１粘接的破坏载荷（８４５．８±１３７．１Ｎ）高于Ｐｏｒｃｅｌｉｔｅ粘接的破坏载荷（５３４．０±５８．７Ｎ），两者间有显著性差异（Ｐ＜０．０５），且超过咀嚼过程中产生的正常牙合力值。提示临床可用Ｐａｎａｖｉａ２１粘接Ｐｌａｔ－Ⅱ型铸造陶瓷全冠。     

Three-dimensional surfaces for human muscle kinetics

Summary Torque, angular velocity and angular position data were collected on six subjects performing maximum knee extensions at 11 speeds. Three-dimensional (3-D) surfaces were drawn for each subject and for the normalised, averaged data. For each subject, the moment arms of knee extensor and patella excursion were determined from radiographs and averaged across subjects. These data were then used to convert the angular data to linear force, velocity and information on muscle length. Surfaces were plotted for these data and evaluated. Results indicate a major difference between the knee positions for production of peak force or torque. Peak linear force was found to occur at an average of 75° of flexion, while peak torque was found at 57°. It was also suggested that 3-D surfaces provide more information than the traditional methods of presenting dynamic strength results.Currently on leave of absence from the University of Otago     

A comparison of five tibial-fixation systems in hamstring-graft anterior cruciate ligament reconstruction

The weak point in an ACL reconstruction immediately after surgery is the tibial fixation of the graft. This factor will often limit the return to load-inducing activities. Many new hamstring-graft fixation devices have been introduced for cruciate ligament reconstruction, but there is little comparative data on their performance. This work tested the hypotheses that some of these devices will resist graft slippage under cyclic loads better than others, and that some will have higher ultimate strength than others. Five devices were tested: WasherLoc, Intrafix fastener; and RCI, Delta Tapered, and Bicortical interference screws. Cyclic loads representing normal walking activity (1000 cycles from 70 to 220 N) and ultimate strength tests were done, using calf tibiae (similar bone density to young human tibiae) and four-strand tendon grafts, with eight tests of each device for each of cyclic and ultimate tensile strength tests. A series of graft creep tests under cyclic loads was also done. The results showed that there was no significant difference in graft construct elongation under cyclic loads (range 0.7–1.3 mm) after allowing for 0.4 mm mean graft creep. The WasherLoc gave the highest ultimate strength (945 N, p <0.001, range 490–945 N). We concluded that all devices performed well under cyclic loads that represented normal walking activity, but the ultimate strengths differed. The performance under cyclic load was better than has been published for conventional interference screws. This evidence suggests that it may now be safe to mobilise younger patients less cautiously immediately after hamstring-graft ACL reconstruction.     

Perceived exertion and maximal quadriceps femoris muscle strength during dynamic knee extension exercise in young adult males and females

The objectives of the present study were to: (1) examine perceived exertion across different target voluntary-contraction intensities; (2) compare perceived exertion ratings with actual target intensities, and (3) compare perceived exertion ratings between males and females. Subjects for this study included 30 healthy, college-aged male (n=15) and female (n=15) volunteers. All subjects were free of orthopedic, cardiopulmonary, systemic and neurological disease. Subjects were evaluated for their one-repetition maximum (1-RM) during inertial knee extension exercise. All subjects then completed, in a random order, two sub-maximal inertial contractions at 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of their 1-RM. Perceived exertion was measured by asking subjects to provide a number that corresponded to the feelings in their quadriceps after completion of the two repetitions, by viewing a modified category-ratio (CR-10) scale. The results showed that males lifted a significantly greater absolute (P<0.05) and relative (P<0.05) amount of mass than females; allometric-modeled strength values also demonstrated significant sex differences. The results revealed a significant intensity main effect (P<0.001) but no significant gender main effect (P=0.97) nor intensity-by-gender interactions (P=0.50) for the perceived exertion responses. The findings demonstrated that perceived exertion was significantly (P<0.05) lower than the specific expected values on the CR-10 scale from 10% to 60% of 1-RM, but was not different from 70% to 90% 1-RM. The results revealed that the increase in perceived exertion was fit to both linear and quadratic trends, and that the exponent of the power function was found to be 1.437 (SD 0.22) for the males, and 1.497 (0.295) for the females. The major findings demonstrate that although males were able to lift more absolute and relative mass than females, the perceptual response to relative load was similar between genders. The increase in perceived exertion, as a function of relative load, showed a strong linear trend; however, enhanced perceptual sensitivity at high contraction intensities was evident from the positively accelerating power function. Electronic Publication     

中央传动轴表面淬火的研究

本文对不同热处理的手扶拖拉机中央传动轴的机械性能、淬硬层深度和显微组织作了研究。结果表明,当最终热处理由原来的高频感应加热淬火改为中频感应加热淬火时,能在不改变材料和大小的情况下,提高抗扭强度和抗弯强度,从而满足了发动机功率提高20％的使用要求。     

GI—Ⅱ型粉浆涂塑渗透陶瓷试件的弯曲强度测试

本研究对GI-Ⅱ型镧系、铈系玻璃料渗透Vita In-Ceram氧化铝以后渗透陶瓷试件的三点弯曲强度进行了测试,并与GI-Ⅰ型及Vita In-Ceram玻璃料渗透同种氧化铝的情况进行了对比研究.结果表明:四种玻璃渗透的渗透陶瓷,三点弯曲强度均在366～409MPa.单因素方差分析四组的强度值差异不具有显著性;玻璃成分中以铈部分取代镧是成功的;在玻璃和氧化铝两个影响渗透陶瓷强度的因素中,氧化铝的影响更为关键.     

Effects of isometric strength training on quadriceps muscle properties in over 55 year olds

Changes in strength, speed and size of the quadriceps muscle have been investigated in elderly men and women after 6 months of isometric strength training. We have also indirectly investigated the role of metabolites as a stimulus for muscle hypertrophy by studying two training protocols. One thigh was trained using short, intermittent contractions (IC), while the other trained using long, continuous contractions (CC). This meant that there should be a greater metabolite change in the muscle performing CC, as the blood flow is occluded for longer. Nine subjects [eight women, mean (SE) age, 71.8 (2.9) years] were measured for contractile properties and strength before and after training, and compared to nine age-matched controls [71.5 (2.1) years]. The training group increased quadriceps strength by 48.7 (9.1)% (P < 0.005) and 53.1 (11.3) % (P < 0.005) following the IC and CC protocols, respectively. There was no change in muscle strength in the controls. Both muscles showed significant slowing after training as measured by the relaxation times and the force-frequency ratio. There were non-significant decreases in muscle fatigability after training. The control group also showed some significant decreases in fatigability and muscle speed. The training group showed significant increases in muscle (and bone) cross-sectional area of 4.0 (1.7)% and 4.9 (1.3)% following the CC and IC protocols, respectively. These increases were significantly different from the decrease observed in the control group. These findings suggest that people over the age of 55 still have the capacity to increase muscle strength and size, and that the training causes slowing of the muscle. Muscle hypertrophy does not seem to be strongly influenced by metabolite changes in this age group, as there were no differences in measurements observed between protocols.