Effect of autocontrol micromotion intramedullary interlocking nail on fracture healing： an experimental study

Objective: To investigate the effect of autocontrol micromotion locking nail ( AMLN ) on experimental fracture healing and its mechanism. Methods: 16 goats undergoing both sides of transverse osteotomy of the femoral shafts were fixed intramedullary with AMLN and Gross-Kempf (GK) nail, respectively. The follow-up time was 7, 14, 28 and 56 days. Roentgenographic, biomechanical, histological, scanning electromicroscopic and biochemical analyses were done. Results: (1) The strength of anticompression, antiflexion and antitorsion in the fractural end in the AMLN-fixed group was higher than that of GK nail-fixed group; whereas, the rate of stress shelter in the fractured end decreased significantly (P<0.01). (2) The content of the total collagen, insoluble collagen, calcium and phosphate in the AMLN-fixed group was higher than that in the GK nail-fixed group (P<0.05). (3) Histological observation and quantitative analysis of calluses revealed that AMLN could promote the growth of bridge calluses and periosteum calluses. Hence the facture healing and remolding process achieved early, which was much better than traditional GK nail fixation. (P<0.05). (4) 7-14 days postoperation, the calluses of AMLN-fixed group was flourish and camellarly arranged and the collagen fibril formed constantly in the absorption lacuna of bone trabecula. 28-56 days postoperation, the collagen fibril was flourish around the absorption lacuna and was parallel to the bone's longitudinal axis. Active bony absorption and formation were seen, so was remolding and rebuilding. Haversian system was intact and the bony structural net was very tenacious because of the deposition of calcium salt. None of the above findings was observed in the GK nailfixed group. Conclusions: The design of AMLN accords well with the plastic fixation theory. As the geometry ametabolic system constituted by the intramedullary fixation instruments and the proximal and distal end of the fracture is very firm and stable, the disturbance to the physical stress distributed in the fractural end is light. The generation and conduct of the intermittent physical stress between the fractural parts could reach the balance between stress conduct and stress protection. The feature that the healing and remolding take place at the same time speeds up the fractural healing process.     

The mechanical and morphological properties of bone beneath internal fixation plates of differing rigidity

The internal fixation of diaphyseal fractures by bone plates is a well recognized treatment. The normal physiological stress of bone is reduced by plates that cause a negative balance of bone-remodeling processes. Many investigators have shown that the degree of stress protection is dependent on the rigidity of the plates. It was the aim of this study to quantify mechanical and morphological changes at different locations in a plated diaphyseal bone as a function of differing plate rigidity. Two types of plates with the same size but different materials were used. The stainless steel plates had a modulus of elasticity and bending stiffness 3.2 times higher than the carbon fiber reinforced carbon plates. Both types of plates were applied to the intact right and left femora of six foxhounds for 6 months. The stiffer stainless steel plates led to a significantly higher bone loss and correspondingly greater loss of mechanical properties. These effects were greatest directly beneath the plate and less with increasing distance from the plate.     

环指屈肌腱损伤吻接术前、后力学性能测试研究

研究正常环指屈肌腱拉伸力学性能和模拟屈肌腱损伤后吻接术后屈肌腱的力学性能,为临床提供生物力学参数。取10个手环指标本,解剖后暴露环指,将标本固定于电子万能试验机底座上,由钢丝绳吊钩沿屈肌腱纵行方向钩住、钢丝绳上端固定于试验机上夹头上,驱动机器,对标本进行拉伸实验,施加拉应力,直至屈肌腱断裂。对断裂后的屈肌腱模拟临床手术进行移位吻接,对10个标本做了腱与腱移位吻接。再对吻接后的标本进行拉伸实验。分别得出了正常组标本和吻接术后标本的拉伸最大载荷、应力、应变等数据。表明:屈肌腱腱与腱吻合组最大载荷、应力、应变均小于正常对照组,但模拟末端编织法吻接术腱与腱吻合组标本,仍具有较好的拉伸力学性能指标。     

全国细菌药敏试验的室间质量评价

目的：了解全国大中型医院细菌药敏试验（AST）状况，提高检测水平和质量。方法：定期向全国各参加评价实验室发放冻干标本，要求在规定时间内报告可疑感染的病原菌及其药敏结果，对回报结果给予数据统计、分析和评价。结果：2000年全国489个细菌室对常见耐药菌的检测正确率分别为：超广谱β－内酰胺酶63％（ESBLs)；苯唑西林敏感金黄色葡萄球菌（MSSA）74％；苯唑西林耐药凝固酶阴性葡萄球菌（MRSCoN)48％；对青霉素不敏感肺炎链球菌7％；氨基糖苷类高水平耐药肠球菌95％；产β－内酰胺酶流感嗜血杆菌正确率35％。结论：通过细菌药敏试验的室间质量评价反映出我国的细菌耐药性检测水平急待提高。     

不稳定型桡骨远端骨折的外固定器治疗

目的：探讨外固定器治疗不稳定型桡骨远端骨折的疗效。方法：对12例不稳定型桡骨远端骨折的患者采用改良AO外固定器治疗，术后随访5－8个月，根据骨折愈合情况和腕关节形态及功能情况，按Jakim评分结果评价治疗效果。结果：骨折愈合时间为6－8周，优良率为91％。结论：外固定器治疗不稳定型桡骨远端骨折具有良好的固定作用，能较好地防止骨折畸形愈合和保护腕关节功能。     

关节镜技术的历史与新进展

现代的关节镜从膀胱镜演变而来，创伤小，适用广泛。近年膝关节镜技术在半月板病变处理上有逆行全切法等新方法，交叉韧带重建、软骨移植成为研究热点；关节镜技术除应用于肩关节及其它小间隙关节，还开展治疗弹响髓等关节外应用；个性化康复锻炼提高了手术疗效。     

Surface movement errors in shank kinematics and knee kinetics during gait

The movement of surface mounted targets (SMT) on a shell at the mid-shank and of bone mounted targets attached to the distal shank using a Percutaneous Skeletal Tracker (PST) were simultaneously measured during free-speed walking of three adult subjects having different body types. Surface movement errors in shank kinematic estimates were determined by expressing the segmental motion derived from the SMT relative to the PST-based segment coordinate system (SCS) located at the segment center of gravity. The greatest errors were along and around the shank longitudinal axis, with peak magnitudes of 10 mm of translation and 8° of rotation in one subject. Estimates of knee joint center locations differed by less than 11 mm in each SCS direction. Differences in estimates of net knee joint forces and moments were most prominent during stance phase, with magnitudes up to 39 N in the shank mediolateral direction and 9 N.m about the mediolateral axis. The differences in kinetics were primarily related to the effect of segment position and orientation on the expression of joint forces and on the magnitude and expression of joint moments.     

Gait biomechanics and the evolution of total joint replacement

The history and evolution of total knee and total hip replacement has been influenced substantially by the knowledge obtained from gait analysis studies. Many of the mechanical problems associated with these devices have been analyzed and evaluated in terms of the mechanics of walking. The magnitude and pattern of the forces at the hip and knee joints derived from gait analysis studies have provided valuable input into the design criteria of both total hip and total knee replacements. Information generated from the gait analysis of patients with total joint replacements has provided objective criteria for assessing functional recovery following this procedure. In addition to providing a basis for design evaluation, the key to the analysis of function following joint replacement is the ability to identify functional adaptations specific to design features. Gait analysis provides a unique opportunity to obtain objective information that cannot be obtained through other clinical means and provides a means for evaluating current designs and future design modifications.