| Objective: The fracture-healing is the reaction of complex repairing process between fragments of the bone. The final result is that recovery the normal structure and biomechanical function of injuring bone tissue. Intermittent soft-tissue pneumatic compression devices have been widely used for the treatment of a variety of condition in which blood circulation is altered. The device have proven to be effective for prevention of postoperative deep venous thrombosis as well as for treatment of venous ulcers, lymphedema, venous insufficiency, and arterial occlusive disease. Mechanical effects of intermittent pneumatic compression on muscles and blood vessels include a decrease in venous stasis with a subsequent decrease in venous pressure, an increase in arterial blood flow, and an increase in interstitial fluid return to circulation. Biochemical effects of intermittent pneumatic compression (IPC) on blood vessels include an increase in the synthesis of nitric oxide, prostacyclin, and tissue plasminogen activator, and a decrease in plasmiongen activator inhibitor. Little or no information is available on the effect of intermittent pneumatic compression on bone-healing. Sudden application of a uniform external pressure to the low extremity impose a change in its structure and hemodynamics, accelerating blood flow and effectively facilitating venous emptying and preventing stasis. The improved emptying of lower extremity veins, with a subsequent decrease in venous pressure, leads to an increase in the arterial venous pressure gradient, ultimately resulting in an increase in the arterial blood flow. Blood circulation, especially arterial blood, is recognized as an important factor in fracture healing. Therefore, an increase in arterial blood flow to the fracture site, especially in the lower limb may improve healing. The purpose of the present study was to evaluate the effect of intermittent pneumatic compression on fracture-healing in animal model. Methods: Thirty female, skeletally mature (twelve to fifteen monthes old) New Zealand White rabbits, ranging in weight from 4.1-4.5kg, received a transverse mid-tibia open osteotomy in the left limb with use of a standardized technique. All animals were maintained in accordance with a protocol approved by the raising-animal plant. A 3mm gap between the bone fragments was created, and the osteostomy site was stabilized with a four-pin double-bar external fixator. In order to cause venous stasis and create the soft-tissue edema that is commonly seen with acute tibia fracture, the left deep femoral vein was ligated in all animals. The animals were then divided into two groups: the study group, consisting of fifteen animals treated with one hour of intermittent sequential pneumatic soft-tissue compression of the distal part of the calf daily,starting on the fourth postoperative day, for a period of twenty-five days, and the control group, consisting of fifteen animals that did not receive intermittent pneumatic compression. Anteroposterior radiographs were made every two weeks to confirm alignment of the osteostomized bone fragments. The healing process was evaluated biweekly with single pholon absorptiometry(SPA), which was employed because it allows progressive, quantitive evaluation of fracture-healing, including callus development(area, mineral content, and density)at the fracture site. At eight weeks, the animals were killed and both tibiae were transected through the proximal and distal metaphyses to provide a 7.0cm diaphyseal segment. The ends of each segment were embedded in blocks of polymethylmethacrylate. Special care was taken to embed the pin holes within the polymethylmethacrylate to avoid stress concentration during torsional testing. The specimens were then mounted on a torsional testing apparatus. A torsion-to-failure test was performed at a rate of 270o/min. the torsional parameters of each osteotomized tibia were normalized as a percentage of the value for the contralateral, intact tibia to minimize interanimal variability associated with animal size. After the index procedure, the specimens were harvested to histological examination. Results: At 2, 4, 6 and 8 weeks after operation, the X-ray showed that at osteotomy site in the study group more consolidated and callus more abundantly than in the controlgroup. The result of single pholon absorptiometry examination demonstrated progressive increase in bone mineral content, callus area and bone mineral density at the osteotomy site in the study group and control group. At the second week of after operation, the bone mineral content, callus area and bone mineral density of the study group was 1.42±1.14, 8.12±3.52, 15.15±8.52, respectively. Those value of the control group was 1.18±1.04, 6.91±3.61, 13.87±6.85, respectively. There were no difference between the study group and the control group. (P>0.05) After 4 weeks, the bone mineral content, callus area and bone mineral density of the study group was 32.33±11.16, 59.84±12.76, 44.71±4.55, respectively. That of the control group was 24.28±8.29, 47.62±17.30, 38.20±4.32, respectively. There were difference in two group. (P<0.05) Up to 6 weeks postoperatively, the bone mineral content, callus area and bone mineral density of the study group was 70.36±10.51, 108.54±11.72, 52.45±5.15,respectively. Those value of the control group was 51.62±12.35, 92.16±19.74, 46.13±4.89, respectively. Those were significant difference in two groups. (P<0.05) By the end of the 8th postoperative week, when the treatment was discontinued, the study group had mineral content, callus area and bone mineral density at the osteostomy site that was 81.61±4.82,114.74±10.32, 57.55±2.14 greater, respectively, than those in the control group (67.02±8.61, 102.82±18.66, 53.69±2.06, respectively.), there were significant difference in two groups. (P<0.05) By six and eight weeks, there weresignificant difference in two group. By the end of 8th postoperative week, all animals were killed. The specimens were harvested, then they were mounted on a torsional testing apparatus. ( CSS-44020c type) The torsional parameters of each osteotomized tibia were normalized as a percentage of the value for the contralateral, intact tibia to minimize inter animal variability associated with animal size. The values for all four torsional parameters tested were significantly higher in the study than in the control group. The maximum torque, stiffness, angular displacement at maximum torque and energy to failure of specimens in the study group were 61.3±18.4, 80.9±23.5, 90.4±17.3, 57.2±19.8 higher, respectively, than those in the control group (41.2±15.1, 61.7±22.8, 66.9±15.8, 26.5±12.4, respectively.), there were significant difference in two groups. (P<0.05) After biomechanical testing, the specimens were harvested to histological examination. The microscopic appearance of the callus at the osteotomy site was full of new woven bone and some of them turned into lamellar bone, and showed larger diameter trabeculae, around new woven bone, abundant osteoblast can be show and active in study group. Then in control group, the trabeculae were sparse, irregular and narrow of the width. Conclusion: 1 Intermittent pneumatic soft-tissue compression on fracture-heaing significantly enhanc bone callus area, bone mineral content and bone mineral density. 2 IPC improved the biomechanical properties of a healing osteotomy...
|
PDF Full Text Request