Titanium Alloy Gamma Nail versus Biodegradable Magnesium Alloy Bionic Gamma Nail for Treating Intertrochanteric Fractures: A Finite Element Analysis.

OBJECTIVE: To using finite element analysis to investigate the effects of the traditional titanium alloy Gamma nail and a biodegradable magnesium alloy bionic Gamma nail for treating intertrochanteric fractures. METHODS: Computed tomography images of an adult male volunteer of appropriate age and in good physical condition were used to establish a three-dimensional model of the proximal femur. Then, a model of a type 31A1 intertrochanteric fracture of the proximal femur was established, and the traditional titanium alloy Gamma nails and biodegradable magnesium alloy bionic Gamma nails were used for fixation, respectively. The von Mises stress, the maximum principal stress, and the minimum principal stress were calculated to evaluate the effect of bone ingrowth on stress distribution of the proximal femur after fixation. RESULTS: In the intact model, the maximum stress was 5.8 MPa, the minimum stress was -11.7 MPa, and the von Mises stress was 11.4 MPa. The maximum principal stress distribution of the cancellous bone in the intact model appears in a position consistent with the growth direction of the principal and secondary tensile zones. After traditional Gamma nail healing, the maximum stress was 32 MPa, the minimum stress was -23.5 MPa, and the von Mises stress was 31.3 MPa. The stress concentration was quite obvious compared with the intact model. It was assumed that the nail would biodegrade completely within 12 months postoperatively. The maximum stress was 18.7 MPa, the minimum stress was -12.6 MPa, and the von Mises stress was 14.0 MPa. For the minimum principal stress, the region of minimum stress value less than -10 MPa was significantly improved compared with the traditional titanium alloy Gamma nail models. Meanwhile, the stress distribution of the bionic Gamma nail model in the proximal femur was closer to that of the intact bone, which significantly reduced the stress concentration of the implant. CONCLUSION: The biodegradable magnesium alloy bionic Gamma nail implant can improve the stress distribution of fractured bone close to that of intact bone while reducing the risk of postoperative complications associated with traditional internal fixation techniques, and it has promising clinical value in the future.

Correlative factor analysis on the complications resulting from cement leakage after percutaneous kyphoplasty in the treatment of osteoporotic vertebral compression fracture.

STUDY DESIGN: The correlative factors for complications resulting from cement leakage were retrospectively reviewed in 71 patients who underwent percutaneous kyphoplasty. OBJECTIVE: To explore the correlative factors affecting the complications of percutaneous kyphoplasty in the treatment of osteoporotic vertebral compression fractures. SUMMARY OF BACKGROUND DATA: Over the past decade, percutaneous kyphoplasty has been increasingly used as treatment of choice for osteoporotic vertebral compression fractures. However, current literature contains less information about the correlative factors affecting the complications resulted from cement leakage. METHODS: In all, 71 patients with 171 vertebral compression fractures who were treated by percutaneous kyphoplasty in the department of spine surgery at our medical center were identified from the registry and were retrospectively reviewed. The treatment efficacy was determined by the assessment of change in vertebral body height, Cobb angle, visual analog scale and Oswestry functional score between preoperative, postoperative, and the latest follow-up. Complications were recorded and associated risk factors were determined and analyzed. RESULTS: All patients had immediate and significant improvement in back pain after being treated with percutaneous kyphoplasty. Cement leakage occurred in 17 (9.94%) out of 171 vertebral bodies, including 7 paravertebral leaks, 6 leaks into intervertebral space, 3 leaks into channel of needling insertion, and 1 spinal canal leak. Four patients (5.63%) developed pulmonary complications postoperatively, one of them with confirmed diagnosis of pulmonary embolism directly caused by cement leakage. During the follow-up, we found 9 recurrence vertebral fractures in 6 patients (8.45%), including 6 adjacent vertebral bodies. Univariate analysis revealed a significant difference in preoperative vertebral body height, injected cement volume, and vertebral body wall incompetence between the cement leakage group and no cement leakage group (P<0.05). In contrast, there is no significant difference in the preoperative Cobb angle, freshness of vertebral fracture, location of operative vertebrae, and operative approach between the 2 groups (P>0.05). Multiple logistic regression analysis showed that the injected cement volume and vertebral body wall incompetence were the predominant variables associated with the complications resulting from cement leakage. The patients who had a history of pulmonary diseases were prone to develop lung-related complications after the surgery. CONCLUSIONS: The cement viscosity, injected cement volume, vertebral body wall incompetence, and a history of pulmonary diseases were the factors affecting the complications resulting from cement leakage. The recognition of these risk factors is helpful in efforts to improve surgical technique to reduce the risk of complications after being treated by percutaneous kyphoplasty.

Application of labeled radioimmunoimaging tracing in detecting pulmonary embolism in rabbits after bone cement perfusion and relevant treatment effects.

BACKGROUND: During the process of bone cement joint replacement, some patients show a series of complications, such as a sudden drop in blood pressure or dyspnea. The cause of the complication is considered to be due to emboli caused by the femur prosthesis insertion. The purpose of the present study was to detect the pulmonary embolism in rabbits after bone cement perfusion by radioimmunoimaging, and to explore its protective measures. METHODS: Forty rabbits, 2.5 - 3.0 kg weight, were randomly assigned to four groups, with ten rabbits in each group. Group I (no intervention): Bone cement perfusion was done after medullary cavity reaming and pressurizing. Group II (epinephrine hydrochloride intervention): The medullary cavity was rinsed with a 1:10 000 normal saline-diluted epinephrine hydrochloride solution followed by bone cement perfusion after medullary cavity reaming and pressurizing. Group III (fibrin sealant intervention): The medullary cavity was precoated with fibrin sealant followed by bone cement perfusion after medullary cavity reaming and pressurizing. Group IV (blank control group): The medullary cavity was not perfused with bone cement after reaming. In each group, the rabbits underwent femoral head resection and medullary cavity reaming. Before bone cement perfusion, 2 ml of developing tracer was injected through the ear vein. Radionuclide imaging was performed at 60, 120, and 180 minutes after bone cement perfusion, and the pulmonary radioactivity in vivo was measured. The rabbits were immediately sacrificed, and the pulmonary tissue was removed and its radioactivity was measured in vitro. Pulmonary tissue was then fixed and the pulmonary embolism and the associated pathological changes were observed. RESULTS: The pulmonary radioactivity in vivo was measured at 60, 120, and 180 minutes after bone cement perfusion. The radioactivities of the four groups were 11.67 ± 2.16, 14.59 ± 2.92 and 18.43 ± 4.83 in group I; 8.37 ± 3.05, 10.35 ± 2.24 and 11.48 ± 2.96 in group II; 3.91 ± 1.19, 5.53 ± 2.95 and 7.25 ± 1.26 in group III; 1.04 ± 0.35, 1.14 ± 0.87 and 1.43 ± 0.97 in group IV. The radioactivities of groups I, II, III at 60, 120 and 180 minutes were significantly higher than group IV (P < 0.05). The pulmonary embolism could be detected. Pretreatment with epinephrine hydrochloride and fibrin sealant significantly decreased the pulmonary radioactivity in group II and group III, but it was still higher than in the group IV. CONCLUSIONS: Radioimmunoimaging is an alternative method for the dynamic observation of rabbit pulmonary embolism after bone cement perfusion. Radioimmunoimaging is the optional way to evaluate the effect of pretreatment with epinephrine hydrochloride or fibrin sealant on pulmonary embolism after bone cement perfusion.