Kemerovo, Kemerovo, Russian Federation
Kemerovo, Kemerovo, Russian Federation
The article deals with the production of bone cement, which is used in various fields of medicine. A new technology for producing medical cement mixtures is presented. Particular attention is paid to use of bone cement in the treatment of vertebral compression fractures associated with osteoporosis. The incidence rate of osteoporosis and its clinical manifestations is expected to increase four times in the next half-century due to the growth of population and the increase in life expectancy. Problems of contemporary medicine that are associated with obtaining granular mixtures of preset quality and composition are discussed. Information about the flowability of the components of cement mixtures is presented. The concept of a criterion of flowability is introduced for the first time for rationally choosing a mixing method according to the flowability of the components for preparing quality cement mixtures. Flowability data for cement mixture components have been obtained to optimize the mixing process. A dimensionless equation is set up to calculate the power requirement for the mixing process. The quality of the resulting granular compositions depends primarily on the physicomechanical properties of the materials being mixed. A continuous, centrifugal, bone cement mixing unit is described, and the principle of its operation is considered. The performance of continuous mixers has been evaluated in terms of output capacity, specific energy consumption, and heterogeneity coefficient. The new, centrifugal mixer has been demonstrated to be more efficient in bone cement production than the pulsating mixer.
vertebroplasty, centrifugal mixer, pulsating mixer, bone cement, polymethyl methacrylate, flowability, hydroxylapatite ceramic, tricalcium phosphate ceramic
INTRODUCTION
The problem of treating osteoporosis is a challenge for present-day health care, for this disease has become quite widespread among the elderly. Approximately 40% of the women and 13% of the men older than 50 years have had one bone fracture or more [8, 10].
It is predicted that the incidence rate of osteoporosis and its clinical manifestations, such as femoral neck fracture, will have increased four times within the next half-century because of the growth of population and the increasing life expectancy [5, 10].
Conventional methods of curing compression fractures of vertebral bodies involve use of analgesics and muscle relaxants, immobilization, bed rest, physiotherapy, and wearing a body jacket [2, 9].
These methods suffer from the following drawbacks: lengthy confinement to bed and the impossibility of early mobilization because of the marked pain syndrome lead to lack of appetite, to impaired glucose tolerance, and to development of hypostatic pneumonia, phlebothrombosis, and, as a consequence, pulmonary artery thromboembolism. In addition, the hypodynamia implied by the bed rest regime diminishes the density of bone tissue (by up to 2% per week), thus causing progress of osteoporosis [6, 7]. For this reason, vertebroplasty is being increasingly used in the symptomatic treatment of pathological compression fractures associated with osteoporosis and osteopenia.
The results of clinical application of vertebroplasty, analyzed by many authors, demonstrated the high effectiveness of this technique in restoring the supporting ability of vertebral column segments affected by tumor-induced osteolysis. This method is primarily indicated for those oncological patients who cannot be subjected to radical surgery for some reason.
Application of vertebroplasty to patients with metastatic spinal injuries would shorten the bed rest period, extend the patient mobilization period, prevent the progress of the pain syndrome, and reduce the risk of neurological complications. Vertebroplasty, a minimally invasive procedure, would make it possible to shorten the hospital stay time. In combination with less frequent use of analgesics, it would reduce the cost of the hospital treatment of this category of patients.
Vertebroplasty is widely used abroad in the treatment of pain syndrome and pathological fractures that are due to metastatic injuries of the vertebral column and osteoporosis. The largest number of vertebroplastic manipulations in the world have been carried out in the United States and Western Europe; among the countries of the Commonwealth of Independent States, the leaders in this field are the Russian Federation and Ukraine [1, 2, 4, 11].
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