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<p><b>OBJECTIVE</b>To compare the biomechanical performances of different wires and cable fixation devices in posterior instrumentation for atlantoaxial instability, and test the effect of different fixation strengths and fixation approaches on the surgical outcomes.</p><p><b>METHODS</b>Six specimens of the atlantoaxial complex (C0-C3) were used to establish models of the normal complex, unstable complex (type II odontoid fracture) and fixed complex. On the wd-5 mechanical testing machine, the parameters including the strength and rigidity of anti-rotation, change and strength of stress, and stability were measured for the normal complex, atlantoaxial instability complex, the new type titanium cable fixation system, Atlas titanium cable, Songer titanium cable, and stainless wire.</p><p><b>RESULTS</b>The strength and rigidity of anti-rotation, change and strength of stress, stability of flexion, extension and lateral bending of the unstable atlantoaxial complex fixed by the new double locking titanium cable fixation system were superior to those of the Songer or Atlas titanium cable (P<0.05) and medical stainless wire (P<0.05). Simultaneous cable fastening on both sides resulted in better fixation effect than successive cable fastening (P<0.05). Better fixation effect was achieved by fastening the specimen following a rest (P<0.05).</p><p><b>CONCLUSIONS</b>The fixation effects can be enhanced by increased fastening strengths. The new type double locking titanium cable fixation system has better biomechanical performance than the conventional Songer and Atlas titanium cables. Fastening the unstable specimens after a rest following simultaneous fastening of the specimen on both sides produces better fixation effect.</p>
Subject(s)
Humans , Atlanto-Axial Joint , General Surgery , Biomechanical Phenomena , Bone Wires , Cadaver , Internal Fixators , Joint Instability , General Surgery , Orthopedic Fixation DevicesABSTRACT
<p><b>OBJECTIVE</b>To compare the anti-rotation biomechanical performances of wire and various cable fixation devices currently used in the posterior Brooks instrumentation for atlantoaxial instability.</p><p><b>METHODS</b>In this experiment,six specimens of the atlantoaxial complex (Occipital-C3) were used. The models of the normal complex,unstable complex (type II odontoid fracture) and fixed complex were established. On the WD-5 mechanics experimental machine,the parameters including the strength and rigidity of anti-rotation were quantified for the normal complex (group N),the atlantoaxial instability complex (group M), the new type Titanium cable (group A), Atlas titanium cable (group B), Songer Titanium cable (group C), stainless wire(group D).</p><p><b>RESULTS</b>The max strength of A, B, C, D groups was 12.5, 11.3, 11.52, 11.55 N x m respectively, the max rigidity was 58.81, 53.17, 54.11, 54.35 N x cm/deg respectively. The strength and rigidity of anti-rotation, compare to the unstable atlantoaxial complex which were fixed by the new double locking Titanium cable fixation system were superior to those of normal complex, instability complex, Songer or Atlas Titanium cable (P < 0.05).</p><p><b>CONCLUSION</b>Having been changed the locking method, the anti-rotation biomechanical characteristics of the new type double locking Titanium cable fixation system are superior or similar to the traditional Songer or Atlas Titanium cable.</p>
Subject(s)
Humans , Atlanto-Axial Joint , General Surgery , Biomechanical Phenomena , Bone Wires , Joint Instability , General Surgery , Orthopedic Fixation Devices , RotationABSTRACT
<p><b>AIM</b>Study on the relationship between the degraded spinal cord injuries and the changes of the motor evoked potentials (MEP) to prove the diagnosis and prognosis value of MEP.</p><p><b>METHODS</b>After injury at T8-T9 cord using modified Allen's weight-drop method, 27 male SD rats were divided randomly into control group (n = 5), group A (50 gcf, n = 8), group B (70 gcf, n = 8) and group C (100 gcf, n = 6). MEPs elicited by monopolar transcortical stimulation were recorded continuously before injury, just after injury, 15 minutes, 1 hour, 3 hours and 6 hours after injury. The rate of the size of the bleeding or necrosis area to the total cord was also calculated.</p><p><b>RESULTS</b>MEP had no significant change in the control group. The amplitude of MEP's early components in group A or group B decreased or even obliterated after SCI, and then partially recovered, while the late components were lost without any recovery signals. All animals in group C showed no MEP waves excepting 2 rats had recovery signals. The size of the cord injuries area increased according to the dropping force and was correlated significantly with the amplitude of the largest peaks of scMEP 1 hour after SCI (r = -0.821).</p><p><b>CONCLUSION</b>The scMEP changes after SCI are correlated with the injury forces and the pathological changes in the cord, which indicates that scMEP can be used as an objective index for the cord functional monitoring.</p>
Subject(s)
Animals , Male , Rats , Electric Stimulation , Evoked Potentials, Motor , Physiology , Rats, Sprague-Dawley , Spinal Cord Injuries , PathologyABSTRACT
Objective: To study the biocompatibility of CFR/PEEK composite in bone tissue after implanted in lumbar intervertebral space and to evaluate its role in the interbody fusion compared to the allograft bone. Methods: Thirteen beagles were chosen among which 7 were implanted with the disk-like CFR/PEEK composite in the lumbar intervertebral space and the other 6 were implanted with allograft bone. X-ray, QCT and histological examination were employed at 6, 12 and 24 months postoperatively. Results: The X-ray results of fusion segment were in conformity with the QCT's as well as that of histological results. All animals obtained a complete fusion at 24 months. Histological examination revealed that the anterior soft tissue to the implant exhibited a nonspecific foreign body reaction with connective tissue embed the biomaterials. Carbon fragment were seen in the surrounding tissue and some of the debric were phagocytosed by foreign body giant cell. Histological examination of bone and material revealed that new bone grew along the hole of CFR/PEEK implant. Conclusion: CFR/PEEK has an excellent biocompatibility to bone tissue.
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Objective: To study the biocompatibility of CFR/PEEK composite in bone tissue after implanted in lumbar intervertebral space and to evaluate its role in the interbody fusion compared to the allograft bone. Methods: Thirteen beagles were chosen among which 7 were implanted with the disk-like CFR/PEEK composite in the lumbar intervertebral space and the other 6 were implanted with allograft bone. X-ray, QCT and histological examination were employed at 6, 12 and 24 months postoperatively. Results: The X-ray results of fusion segment were in conformity with the QCT's as well as that of histological results. All animals obtained a complete fusion at 24 months. Histological examination revealed that the anterior soft tissue to the implant exhibited a nonspecific foreign body reaction with connective tissue embed the biomaterials. Carbon fragment were seen in the surrounding tissue and some of the debric were phagocytosed by foreign body giant cell. Histological examination of bone and material revealed that new bone grew along the hole of CFR/PEEK implant. Conclusion: CFR/PEEK has an excellent biocompatibility to bone tissue.
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Objective To probe the biological degradation of composite bone cement of calcium phosphate and cancellous bone granules,as well as its biophysical and solidifying characteristics.Methods The specimens of composite bone cement were determined by its solidification,which were made of 2.5g calcium phosphate cement mixed either with10%,15%,20%,25%,30%or 35%bone granules of 0.5～1.0mm diameter.The cylindrical specimens of 10mm diameter and18mm length were used for biomechnical test.Furthermore,the bone defect of 5mm?5mm?6mm in12canines were made in L 3 and L 4 verte bral body through anterolateral lumbar vertebral body approach,and composite bone cement with20%bone granules and calcium phosphate cement were filled into the bone defects respectively.The bone formation was evaluated by X-ray and histological examination.Results The composite bone cement with less than20%cancellous bone granules displayed excellent solidifying character,while with the diameter of 0.5～1.0mm and the content of 15%to20%cancellous bone granules,the maximal load and com pressive strength of the composite bone cement were of no significant difference with calcium phosphate ce ment ;but the biomech nical characteristics would decrease if the diameter was1.0～2.0mm despite of the content 15%to20%gran ules.New bone formation were observed in the center of composite bone cement 2months later,and com posite bone cement were replaced mostly by new bone at4months;while in calcium phosphate cement group,only slight degradation occurred at the interface of implant material and host bone at2and4months.Conclusion The composite bone cement of calcium phosphate with20%content and0.5～1mm di am eter of can cellous bone granules can provide the ability of rapid degradation and bone formation.The re sults of study present the basic data of the reparative materials with the composite bone cement for verte-broplasty clinically.