塑性土壤破碎方法的比较

用改装的三轴剪切仪对拉伸、扭转、弯曲、直剪、切割和纯切割等基本加载方式进行了详细研究。结果表明,弯曲加载是需要最小力及最少能耗使塑性土壤破碎的一种有效的加载方式。     

削片机主轴的断裂与研制

削片机是木材废料和林区剩余物综合利用的重要机械设备,给林区带来了显著的经济效益和社会效益。黑龙江省友好木材综合加工厂Ⅱ号削片机,使用43个月后其主轴完全破断。本文在实地调查分析的基础上,对主轴进行了受力分析和断裂失效分析,研制了新主轴。投产一年来,通过对主轴的径向跳动测试和刀盘端面跳动测试表明,新主轴较原主轴的结构合理,工作正常,给工厂带来了较大的经济效益。     

A COMPARISON OF RADIOGRAPHY, COMPUTED TOMOGRAPHY, AND MAGNETIC RESONANCE IMAGING FOR THE DIAGNOSIS OF PALMAR PROCESS FRACTURES IN FOALS

The relative sensitivity of radiography, computed tomography, and magnetic resonance imaging for detecting palmar process fractures of the distal phalanx in foals was determined and the imaging findings were compared with histomorphologic evaluations of the palmar processes. Compared to radiography, computed tomography and magnetic resonance imaging did not improve the sensitivity for detection of palmar process fractures. Statistical agreement for palmar process fracture diagnosis was excellent among the three imaging modalities. Histomorphologic evaluations were more sensitive for diagnosis of palmar process fracture than any of the imaging modalities. Three-dimensional image reconstructions and volume measurements of distal phalanges and palmar process fracture fragments from computed tomography studies provided more complete anatomical information than radiography. Magnetic resonance imaging confirmed that the deep digital flexor tendon insertion on the distal phalanx is immediately axial to the site where palmar process fractures occur, and differentiated cartilage, bone, and soft tissue structures of the hoof.     

A RADIOGRAPHIC INVESTIGATION OF THIRD CARPAL BONE INJURY IN 42 RACING THOROUGHBREDS

A retrospective study of carpal radiographs from 42 racing thoroughbreds with carpal lameness was performed. Radiographs from 50 carpal examinations were available for review. The radiographic findings pertaining to the third carpal bone were described. Fractures and/or sclerosis occurred almost exclusively within the radial fossa. The occurrence of sclerosis without fracture in 20 of the 50 carpal examinations was higher than anticipated, occurring in both the right and left third carpal bone with equal frequency. The right third carpal bone was more frequently fractured and more severely affected than the left. The sclerotic changes seen in the radial fossa of the third carpal bone may be stress-induced, possibly preceding more serious changes in the joint such as cartilage damage or gross fracture. Earlier recognition of sclerosis of the third carpal bone may help prevent more serious changes from occurring.     

棒料塑性剪切过程中裂纹的形成及扩展行为

通过轴向压力作用下棒料塑性切口工试验，获取了剪切分离面上断裂区形态，结果表明：断裂区呈对称月牙状，断裂面积比率随轴向压力的增大而减小。结合理论分析，提示了剪切过程中裂纹首先产生于棒料上活动剪刃与固定剪刃交叉的两水平端点，并沿活动剪刃和固定剪刃刃口迹线扩展。裂纹为Ⅱ、Ⅲ型的混合型，其中Ⅲ型裂纹扩展速度对于断裂区形态起着决定作用。     

Fractures of the carpus in racing thoroughbreds of the Japan Racing Association: Prevalence, location, and current modes of surgical therapy

From 1985 through 1994 approximately 39,800 Thoroughbred horses competed in over 3,400 races each year conducted by the Japan Racing Association (JRA). During this time the prevalence of fractures incurred during racing was 1.99, and 0.09% during training. Of these, 0.32% of the horses during racing died or were humanely destroyed as a direct result of their injuries. During 1994, 1,837 fractures occurred. The cuboidal bones of the carpus and the distal end of the radius accounted for 33.5% of all recorded fractures, with 47.4% of these occurring during racing and 24.2% occurring during training. The most common sites of fracture within the carpus were the distal end of the radius, the third carpal bone, and the radial carpal bone accounting for 35.3, 35.2, and 29.5% of fractures, respectively. Of these, 86/7% of osteochondral fractures occurred on the dorsal aspect of the cuboidal bones. At racing speed, characteristic fractures of the carpus are relatively common in race horses.Since 1991 in Japan, arthroscopic surgery has been the treatment of choice for the removal of carpal joint osteochondral fragments. Of all horses having arthroscopic surgery (n=155), 68.4% of these horses returned to race 9 months after surgery. Of all horses having osteochondral fractures of the distal end of the radius, radial carpal, and third carpal bones treated with arthroscopic surgery in 1993 (n=97) 52.6%, 60.0%, and 55.6% respectively, returned to race and competed at the same level of competition or higher compared with pre-operative racing performance. Arthroscopic surgery, as adapted by the JRA, is a useful technique for the treatment of carpal bone fractures in race horses; however, following surgery some horses had chronic arthritic changes associated with the surgical site. This suggests that the surgical methods and post-operative training program have to be re-evaluated.The objectives of this paper are to describe the prevalence, location, post-operative complication and racing performance for horses having cuboidal carpal bone fractures in racing Throughbreds of JRA.     

Fixation of Cancellous Bone and Physeal Fractures in Dogs and Cats. A Comparison of the Use of Self-reinforced Biodegradable Devices to the Use of Metallic Devices and External Fixations

The use of self-reinforced biodegradable devices made of polyglycolide in the cancellous bone and physeal fractures of dogs and cats was compared to the use of metallic devices and external fixations on similar fractures. The series consisted of 64 dogs and 22 cats divided into 6 comparable groups. The patients in the 2 groups fixed with biodegradable devices started to use their operated limbs earlier than in the other groups. The same 2 groups also healed clinically (showed no lameness) earlier than the other groups. Radiographically there was no statistical difference between the 6 groups.On the basis of this study it may be concluded that the fixation with self-reinforced biodegradable devices is as suitable for the fixation of cancellous bone and physeal fractures of dogs and cats as the fixation with metallic devices or external fixation. This biodegradable technique has additional benefits allowing the patients to feel less pain in their operated limbs and making secondary operations to remove the devices unnecessary.     

Experimental use of polyamide bands in combination with intramedullary pinning for repair of oblique femoral fractures in rabbits

OBJECTIVE: To evaluate the use of polyamide bands, manufactured for securing electrical cables, for repair of oblique femoral fractures in rabbits. STUDY DESIGN: Experimental study. ANIMALS: Twelve nulliparous, 21-25-week-old, California female rabbits. METHODS: Rabbits were divided into 3 groups (n=4) and studied for 14, 28, or 56 days. A Z-shaped mid-diaphyseal femoral osteotomy was repaired with a 2.5 mm intramedullary pin and a polyamide 6.6 cerclage band. Healing was evaluated at intervals by physical examination, limb use, femoral radiographs, and callus histology. RESULTS: Rabbits had early limb use with good wound healing. From the 1st day, movement of the hip and stifle joints was satisfactory. Radiographically, fractures were healed at 28 days. Histologically, there was no foreign body reaction and bone healing was normal. CONCLUSION: Nylon cerclage band application was accomplished easily, maintained reduction, and resulted in good healing and limb use. CLINICAL RELEVANCE: Sterilized nylon bands, manufactured for electrical use, can be used for cerclage in rabbits.     

Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long-bone fracture model using a bone substitute

OBJECTIVE: To compare the mechanical properties of 4 stabilization methods for equine long-bone fractures: dynamic compression plate (DCP), limited contact-DCPlate (LC-DCP), locking compression plate (LCP), and the clamp-rod internal fixator (CRIF--formerly VetFix). STUDY DESIGN: In vitro mechanical study. SAMPLE POPULATION: Bone substitute material (24 tubes) was cut at 20 degrees to the long axis of the tube to simulate an oblique mid-shaft fracture. METHODS: Tubes were divided into 4 groups (n=6) and double plated in an orthogonal configuration, with 1 screw of 1 implant being inserted in lag fashion through the "fracture". Thus, the groups were: (1) 2 DCP implants (4.5, broad, 10 holes); (2) 2 LC-DCP implants (5.5, broad, 10 holes); (3) 2 LCP implants (4.5/5.0, broad, 10 holes) and 4 head locking screws/plate; and (4) 2 CRIF (4.5/5.0) and 10 clamps in alternating position left and right of the rod. All constructs were tested in 4-point bending with a quasi-static load until failure. The implant with the interfragmentary screw was always positioned on the tension side of the construct. Force, displacement, and angular displacement at the "fracture" line were determined. Construct stiffness under low and high loads, yield strength, ultimate strength, and maximum angular displacement were determined. RESULTS: None of the implants failed; the strength of the bone substitute was the limiting factor. At low loads, no differences in stiffness were found among groups, but LCP constructs were stiffer than other constructs under high loads (P=.004). Ultimate strength was lowest in the LCP group (P=.01), whereas yield strength was highest for LCP constructs (409 N m, P=.004). CRIF had the lowest yield strength (117 N m, P=.004); no differences in yield strength (250 N m) were found between DCP and LC-DCP constructs. Differences were found for maximum angular displacement at the "fracture" line, between groups: LPCfracture treatment. With respect to biomechanical properties, DCP, LC-DCP, and LCP constructs did not show critical differences so other factors may direct clinical selection of these implants. We prefer the LCP implants because of the high yield strength, high stiffness under high-load application, and the least movement at the fracture line.     

Treatment of a second carpal bone fracture by removal under ultrasonographic guidance in a horse

OBJECTIVE: To report an unusual 2nd carpal bone (C2) slab fracture and its treatment, using an ultrasonographically assisted, minimally invasive arthrotomy technique, for fragment removal. STUDY DESIGN: Case report. ANIMALS: An 11-year-old crossbred Warmblood gelding. METHODS: A bone fragment, spanning the height of C2, identified on the palmaromedial aspect of C2 was demarcated intraoperatively using ultrasonographically guided needles and removed by arthrotomy. RESULTS: Fracture fragment removal was achieved using a small, ultrasonographically guided arthrotomy. The horse has become sound after treatment and returned to the previous level of pleasure riding activity. CONCLUSIONS: Perioperative ultrasonography was used to delineate and facilitate removal of an unusual slab fragment of C2, through a minimally sized arthrotomy. Despite the presence of pancarpal osteoarthritis and partial involvement of the medial collateral ligament, the prognosis appeared to be satisfactory for this pleasure riding horse. CLINICAL RELEVANCE: Ultrasonographic guidance may be used to optimize the approach to C2 articular bony fragments that may not be observed using arthroscopy.