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At least 235 records · Page 13Linked to original sources
PubMed1995

[An experimental study of the effects of stress-relaxation plate on bone remodeling].

An ideal bone plate would provide rigid fixation to ensure stabilization of bone fragments at the early stage after fracture, while at the late stage osteoporosis induced by stress shielding effect of the plate should be prevented. However, there is no report of such a plate that could meet with all these requirements. Twenty-eight adult New Zealand rabbits were used in this experiment. Ordinary stainless-steel plate (no washer plate) and similar plate padded with ultrahigh molecular polyethylene washers in its screw holes (washer plate) were fixed respectively on mid-shelf of each side of tibiae. The animals were killed at 2, 4, 8, 12, 16, 20 and 24 weeks after operation, and the fixed bone segments of both tibiae were removed for light microscopy, polarized light microscopy and fluoroscopy. The results showed that the tibiae fixed with plate fixation both appeared bone resorption, but there was more severe resorption in bone with no washer plate fixation than that with washer plate fixation. Cancelization of cortical bone was seen in the former but not in the latter at 12 weeks postopertively. This demonstrated that the washer might creep and damage with fixation time, resulting in gradual decrease in the rigidity of the plate-screw system and thus reducing bone resorption as caused by stress shielding.

Animals↗
PubMed1995

[Influence of stress-relaxation plate on bone geometrics and mechanical property: an experimental study].

In order to maintain the effective fixation effect of rigid bone plate in the early stage of fracture and to prevent osteoporosis induced by stress shielding effect of rigid plate in later stage of fixation, a washer made of viscoelastic material was placed between the screw and the screw hole of plate to form a stress-relaxation plate system. Both in vitro and in vivo experiments demonstrated that there was no statistical difference between the stress shielding effect of padded and unpadded plate groups. The washer showed significant deformation and damaged 8 weeks after implantation, and 10 weeks after implantation the stress shielding rate of the padded plate group was significantly lower than that of the unpadded group (P < 0.05). As a consequence, the degree of osteoporosis of the tibia in the padded group was significantly milder than the unpadded group, and 20 weeks after implantation, the diameter of the tibia medullary cavity of the padded group was significantly smaller than that of the unpadded group. The thickness of cortical bone and the bending strength of the tibia of padded group were significantly larger than those of the unpadded group (P < 0.05-0.01). These results showed that the stress-relaxation plate system can effectively maintain the stability of fracture fixation at the similar level of rigid plate during the early stage of fracture and can gradually lower down the stress shielding rate so as to prevent severe osteoporosis and reduction of bone mechanical property in the later stage of fixation.

Animals↗
PubMed2001

[Post-discectomy cervical fusion. Clinico-radiological study comparing iliac crest bone graft, anterior cervical plate with bone graft and cage-plate GD].

OBJECTIVE: To compare clinical and radiologically three methods of cervical arthrodesis after anterolateral one-level discectomy for non-traumatic disk disease. MATERIALS AND METHODS: Three groups of patients were studied retrospectively. In group 1 (20 patients) a tricortical autologous iliac crest bone interbody graft was used. In group 2 (10 patients) the bone graft was associated to an anterior cervical plate (Stryker). In group 3 (10 patients) a cage-plate filled with iliac crest trabecular bone was implanted (plate-cage GD). Clinical and radiological parameters were recorded preoperatively and 6-9 months postoperatively. RESULTS: There was a significant clinical improvement in all three groups, with similar complications and hospitalization time. There were not hard-ware failures. There was a significant increase in the disc height in group 3 when compared with group 1 and a significant correction of the preoperative kyphosis in group 3 in relation to both group 1 and 2: There was a significant increase in postoperative radiological stability rate and also in the operative time in groups 2 and 3 when compared with group 1. CONCLUSIONS: Cervical arthrodesis after discectomy is an useful method for treatment of cervicobrachialgia. Arthrodesis with internal fixation achieves best clinical and radiological results and it has some other advantages in relation to bone graft artrhodesis. GD cage-plate minimizes the surgical and clinical problems associated with use of bone graft and cervical plate and reaches the best radiological performances.

Adult↗
PubMed2000

Mechanical analysis of the bone to plate interface of the LC-DCP and of the PC-FIX on human femora.

The scope of this analysis was to evaluate the mechanical behaviour of newly developed plates at the junction between plate and bone (friction between plate and bone) for the limited contact dynamic compression plate (LC-DCP) and the point contact fixator (PC-Fix) under simulated physiological load and using the tension band principle on the human femur. The intact human cadaveric femora were plated on the lateral aspect according to the tension band principle (AO) and subjected to a load which simulated careful physiological load in single stance. Five strain gauges were glued around the bones, parallel to the bone axis, at five levels, whereby three of them had to be covered by a bone plate and the two others were just outside the plate location. The cross-sectional geometry had been obtained at these levels using computed tomography. One side was plated using the conventional compression plate LC-DCP and the contralateral side using the internal fixator PC-Fix. The LC-DCP was affixed using screws tightened at different torque values and the PC-Fix at a standard torque value. Motion (slippage) between the plate and the bone was indicated by a hysteresis of the strain reading during loading and unloading. Slippage was more important for the LC-DCP than for the PC-Fix, particularly at the proximal end of the plate and when the screws were insufficiently tightened on the LC-DCP. As expected, better stability was obtained with the PC-Fix.

Animals↗
PubMed1979

[Importance of the friction between plate and bone in the anchoring of plates for osteosynthesis. Determination of the coefficient of metal-bone friction in animal in vivo].

In mechanical devices in general the friction plays an important role in force transmission. To find out about the magnitude of frictional forces between internal fixation plate and bone in vivo, simultaneous strain recording in plated bone and instrumented plate were performed. After 3 weeks of implantation the torque applied to a single plate-screw was set to definite levels. Thus it could be determined at what level of screw compression and at what tangential load of the related surface bone-plate, gliding occurred. The coefficient of friction was found to be 0.2 +/- 0.09 (x +/- Sx). It can be concluded that in vivo friction produced at the plate-bone contact surface is able to guarantee stability of fixation.

Animals↗
PubMed1993

Anterior cervical spine fusion: struts, plugs, and plates.

Bone grafting in the cervical spine is an expanding and rapidly changing area. Its success depends on the presence of bone formation, bone incorporation, and ongoing adaptive remodeling to mechanical loads. The evaluation of anterior cervical spine grafts requires a basic understanding of bone graft physiology, its clinical applications, and its postoperative appearances. The roles of routine radiography, polydirectional tomography, computed tomography, and magnetic resonance imaging in the assessment and follow-up of the postoperatively grafted cervical spine will be discussed. The main focus of this paper is to review current surgical procedures utilized for stabilizing the cervical spine as well as to discuss the radiologist's role in the imaging of this region.

Bone Plates↗
PubMed1992

Effect of animal species and age on plate-induced vascular damage in cortical bone.

Plates used for fracture fixation produce vascular injury to the underlying cortical bone. During the recovery of the blood supply, temporary osteoporosis is observed as a result of Haversian remodeling of the necrotic bone. This process temporarily reduces the strength of the bone. We tackled the postulate that quantitative differences exist between animal species, and in different bones within the same species, due to variations in the relative importance of the endosteal and periosteal blood supplies. Using implants scaled to the size of the bone, we found comparable cortical vascular damage in the sheep and in the dog, and in the tibia and femur of each animal. We observed a significant reduction in cortical vascular damage using plates that had a smaller contact area with the underlying bone. No significant difference in cortical vascular damage was noted in animals of different ages.

Age Factors↗
PubMed1992

Holding power of metallic screws in cancellous bone and metallic plates in cortical bone. An experimental study on rabbits using polymethylmethacrylate and bone graft as supporting material.

The holding power of metallic screws in cancellous bone and metallic plates in cortical bone was tested in sixty rabbits (n = 60). These metallic devices were fixed either without support or with the support of plastic material or autogenous bone graft. The fixation firmness was studied radiographically and by a test of the bonding strength. After six weeks, the mean value of the holding power of screws in cancellous bone without support was 440 N, and that of screws supported by polymethylmethacrylate 674 N and by bone graft 540 N. Corresponding values after twelve weeks were 436 N, 664 N, and 616 N. Fixation with polymethylmethacrylate was better than either fixation without support (P < 0.001, t-test) or fixation with bone graft (P < 0.01), whereas fixation with bone graft was better than fixation without support (P < 0.07). The best fixation was achieved by polymethylmethacrylate according to group mean values. Our investigation of the holding power of plates in cortical bone did not reveal any statistically significant differences between the methods used.

Animals↗
PubMed1985

Bone atrophy after plate fixation. Computed tomography of femoral shaft fractures.

Twelve patients with previous femoral shaft fracture treated by rigid plate fixation were examined by computed tomography (CT) scanning 1 or 2 days after plate removal. In the previously plated segment an average reduction in cortical density of 11 per cent was found, and the reduction was most pronounced in the cortex directly beneath the plate. No reduction in cortical thickness of the plated bone occurred. Proximal and distal to the site of the plate, and in the ipsilateral tibial shaft, a slight reduction in cortical density and thickness averaging 2-3 per cent was found.

Adolescent↗