Biomechanical Values Research Articles

Comparative effects of monopolar radiofrequency energy and conservative management of mechanical properties of elongated lateral collateral ligament in rabbits: an experimental study

Objective. We examined the biomechanical effects of shrinkage in elongated rabbit lateral collateral ligament. Design. This study was designed in an attempt to evaluate the energy effects of monopolar radiofrequency on strained but not ruptured ligaments. Background. In treatment of ligament injuries difficulty in reducing increased laxity after trauma and recurrence of instability are important factors for failure. Methods. Ligament elongation and laxity were achieved in operating room by applying varus stress for multiple times. In Group C ( n=8), elongated lateral collateral ligaments were treated only with above-knee cast, while in Group S ( n=8), they were treated with shrinkage and above-knee casts. The un-operated sides were labeled as control groups. At the 12th week after surgery the animals were sacrificed and hind limbs were disarticulated. Removing the other soft tissues around knee, only lateral collateral ligaments were left intact. Biomechanical analyses of the effects of two different treatment methods were compared by performing a pulling-out test. Results. Considering maximum load and stiffness, conservatively treated ligaments were stronger and stiffer than shrunken ligaments ( P<0.05). Conclusion. Biomechanical values were altered by both treatment methods. Reflecting an alteration in intra-molecular structure, the main alteration was the decrease of strength in shrunken ligaments. In ligament injuries, we concluded shrinkage not to be superior to conservative treatment. Relevance The treatment methods are not efficient enough to prevent the strained and treated ligaments from laxity increasing with time because of creep response.

Age and ovariectomy impair both the normalization of mechanical properties and the accretion of mineral by the fracture callus in rats

The impact of age and ovariectomy on the healing of femoral fractures was studied in three groups of female rats at 8, 32 and 50 weeks of age at fracture. In the two older groups, the rats had been subjected to ovariectomy or sham surgery at random at 26 weeks of age. At fracture, all rats received unilateral intramedullary pinning of one femur and a middiaphyseal fracture. Rigidity and breaking load of the femora were evaluated at varying times up to 24 weeks after fracture induction by three-point bending to failure. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. In the youngest group, 8-week-old female rats regained normal femoral rigidity and breaking load by 4 weeks after fracture. They exceeded normal contralateral values by 8 weeks after fracture. In the middle group, at 32 weeks of age, fractures were induced, and the femora were harvested at 6 and 12 weeks after fracture. At 6 weeks after fracture there was partial restoration of rigidity and breaking load. At 12 weeks after fracture, only the sham-operated rats had regained normal biomechanical values in their fractured femora, while the fractured femora of the ovariectomized rats remained significantly lower in both rigidity and breaking load. In contrast, for the oldest group of rats, 50 weeks old at fracture, neither sham-operated nor ovariectomized rats regained normal rigidity or breaking load in their fractured femora within the 24 weeks in which they were studied. In all fractured bones, there was a significant increase in BMD over the contralateral intact femora due to the increased bone tissue and bone mineral in the fracture callus. Ovariectomy significantly reduced the BMD of the intact femora and also reduced the gain in BMD by the fractured femora. In conclusion, age and ovariectomy significantly impair the process of fracture healing in female rats as judged by measurements of rigidity and breaking load in three-point bending and by accretion of mineral into the fracture callus.

An in vitro biomechanical comparison of an interlocking nail system and dynamic compression plate fixation of ostectomized equine third metacarpal bones.

To compare the mechanical properties of two stabilization methods for ostectomized equine third metacarpi (MC3): (1) an interlocking nail system and (2) two dynamic compression plates. Animal or Sample Population-Ten pairs of adult equine forelimbs intact from the midradius distally. Ten pairs of equine MC3 were divided into two test groups (five pairs each): caudocranial four-point bending and torsion. Interlocking nails (6 hole, 13-mm diameter, 230-mm length) were placed in one randomly selected bone from each pair. Two dynamic compression plates one dorsally (12 hole, 4.5-mm broad) and one laterally (10 hole, 4.5-mm broad) were attached to the contralateral bone from each pair. All bones had 1 cm mid-diaphyseal ostectomies. Five construct pairs were tested in caudocranial four-point bending to determine stiffness and failure properties. The remaining five construct pairs were tested in torsion to determine torsional stiffness and yield load. Mean values for each fixation method were compared using a paired t-test within each group. Significance was set at P<.05. Mean (+/-SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite, respectively, in four-point bending were: composite rigidity, 3,454+/-407.6 Nm/rad and 3,831+/-436.5 Nm/rad; yield bending moment, 276.4+/-40.17 Nm and 433.75+/-83.99 Nm; failure bending moment, 526.3+/-105.9 Nm and 636.2+/-27.77 Nm. There was no significant difference in the biomechanical values for bending between the two fixation methods. In torsion, mean (+/-SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite were: composite rigidity, 124.1+/-16.61 Nm/rad and 262.4+/-30.51 Nm/rad; gap stiffness, 222.3+/-47.32 Nm/rad and 1,557+/-320.9 Nm/rad; yield load, 94.77+/-7.822 Nm and 130.66+/-20.27 Nm, respectively. Composite rigidity, gap stiffness, and yield load for double plate fixation were significantly higher compared with interlocking nail fixation in torsion. No significant differences in biomechanical properties were identified between an interlocking nail and double plating techniques for stabilization of ostectomized equine MC3 in caudocranial four-point bending. Double plating fixation was superior to interlocking nail fixation in torsion.

Intradermal Injection of Autologous Dermal Fibroblasts Improves Wound Healing in Irradiated Skin

Background. Despite its well-recognized benefits in the management of several solid tumors, the use of radiotherapy prior to surgery is associated with a high incidence of significant surgical wound healing complications. Radiation-induced damage to dermal fibroblasts has been proposed as an important cause. We hypothesized that the introduction of normal, unirradiated fibroblasts into previously irradiated skin would enhance healing of the subsequent surgical wound.Materials and methods. Four groups of wounds were examined in female Wistar rats: (1) unirradiated skin (n = 10), (2) irradiated skin injected with tissue culture medium alone (n = 17), (3) irradiated skin injected with autologous dermal fibroblasts (n = 17), and (4) irradiated skin injected with irradiated autologous dermal fibroblasts (n = 7). Wounds were evaluated biomechanically and histologically.Results. The biomechanical values of breaking load, ultimate tensile strength, elastic modulus, and toughness were significantly greater in the irradiated wounds injected with fibroblasts than those injected with medium only. These cell-injected wounds did not perform as well biomechanically as those in unirradiated skin. Irradiating the cells prior to injection resulted in biomechanical results no better than those in medium-injected wounds.Conclusions. These results demonstrate that injection of normal, unirradiated fibroblasts significantly improves healing of the irradiated surgical wound. These cells are likely better able to respond to the proliferative, migratory, and synthetic demands of the wound healing environment, as injection of irradiated cells has an equivalent effect on healing as injection of medium alone.

Outgrowing trends in the lower extremities of children

The authors present an overview of the changing biomechanical values in the growing child. They discuss a technique of evaluating total genu varum and genu valgus. A simple tread mat technique is presented.

大腿骨頚部ｆｉｂｒｏｕｓ ｄｙｓｐｌａｓｉａの治療経験

Fibrous dysplasia of the femoral neck is a serious clinical problem because structural stability is destroyed.We experienced treating four patients with monostotic fibrous dysplasia of the femoral neck. One of the patients was male and three were female, whose ages were 16 to 41 years. Two patients were treated with curettage of lesions of fibrous dysplasia and autogenous cancellous bone-grafting, together with vascular bundle transpla ntation. One patient was treated with curettage and cortical bone-grafting, and the other with corrective osteotomy for coxa vara after a pathological fracture.In the treatment of symptomatic fibrous dysplasia several surgical approaches have been uesd with varying success. Curettage and autogenous cancellous bone-grafting are used primarily as a means of filling small defects and inducing bone formation. But radical excision is being abandoned, since it is now recognized that removal of all dysplastic tissue is not needed to achieve a satisfactory result. So autogenous cortical bone is chosen for reconstructing large defects that require strength and is used primarily as supporting struts. When a symptomatic deformity is continued, corrective osteotomy is indicated to obtain normal biomechanical values of the hip.Our treatment plans are as follows;1) prevention of deformity and fracture2) corrective osteotomy for a symptomatic deformity