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진공혼합방법이 골시멘트의 인장 및 피로강도에 미치는 영향에 관한 실험적 연구
백철수,박상원,손원영 고려대학교 의과대학 1994 고려대 의대 잡지 Vol.31 No.3
The most common complication of cemented total hip arthroplasty is aseptic loosening of prosthetic components. The failure of the cement mantle is the most common mode of aseptic loosening of cemented components. The large voids entrapped within the cement by current hand mixing technique may contribute to poor mechanical properties and early fatigue failure of bone cement. Two major methods including centrifugation and vacuum mixing had been studied to reduce porosity or voids and to improve mechanical properties of acrylic bone cements. A common method of reducing the viscosity of acrylic bone cements or of prolonging the period of lower viscosity state is to prepare of the bone cements using monomer that has been chilled to 0-4℃. The object of this experiment is to study the effect of vacuum mixing, and the effect of monomer chilling on the tensile and fatigue strength of acrylic bone cement. The bone cements used was Palacos R® (Schering-Plough International Inc. USA). The monomer of Palcos R® was kept at 4℃ and 21℃ prior to mixing. Two mixing methods were used hand stirring in the atmosphoric pressure and under a vacuum. Hand mixing method was prepared by mixing forty grams of polymer with twenty milliliters of monomer for fifty seconds at a stirring approximately 2 times at one second in an open plastic mixing bowel with a plastic spatula. For vacuum mixing, vacuum mixing system from Scientific Development Compony (Germany) was used. According to manufacturer's instruction, twenty milliliters of monomer and forty grams of polymer were mixed at the constant pressure of four hundred mmHg for fifty seconds. After preparation by a hand mixing method and a vacuum mixing method, all mixing cements poured into ASTM standard(KSB 0802) cylindric mold. Eighty molded specimens were made for experiments, and all specimens were tested at 21℃. Experiments were divided into 4 groups : Group 1 : Hand mixed specimens with monomer keeping at 21℃ Group 2 : Hand mixed specimens with monomer chilling at 4℃ Group 3 : Vacuum mixed specimens with monomer keeping at 21℃ Group 4 : Vacuum mixed specimens with monomer chilling at 4℃ Each experimental group was comprised of twenty specimens. Static tensile strength test was carried out on each group of ten specimens of 4 experimental groups using Instron Model 1127 testing machine at a strain rate of 5mm per minute with gauge length of 50mm. Fatigue strength test was carried out on each group of ten specimens of 4 experimental groups using MTS Model 810 at stress of 25MPa and a freguency of 2.5 hertz. The number of cycles to failure was recorded. Statistical analysis was done with the ANOVA method and the log rank test. The probability of survival of fatigue strength was analysed by gamma distribution. The results obtained were as follows : 1. The mean ultimate tensile strength of vacuum mixed specimens was increased more than hand mixed specimens regardless of prechilling of the monomer. The mean ultimate tensile strength of vacuum mixed specimens with monomer chilling at 4℃ increased thirty-two percentage greater than hand mixed specimens with monomer keeping at 21℃. 2. The ultimate tensile strength of hand mixed speciemns was not influenced by prechilling of the monomer. 3. The mean fatigue strength of vacuum mixed specimens was increased more than hand mixed specimens regardless prechilling of the monomer. The mean fatigue strength of vacuum mixed specimens with monomer chilling at 4℃ was 9.5 times greater than hand mixed specimens with monomer keeping at 21℃. 4. The mean fatigue strength of hand mixed specimens with monomer keeping at 21℃ was 1.7 times greater than hand mixed specimens with monomer chilling at 4℃, but it has no statistical difference. 5. The survival probability of fatigue strength at 3,000 cycles by gamma distribution showed longer fatigue life for vacuum mixed specimens than hand mixed specimens regardless of prechilling of monomer. 6. The scanning electromicrographic findings of fracture surface of specimens in 4 experimental groups showed a greater number and larger diameter of air voids in the hand mixed specimens than vacuum mixed specimens regardless of prechilling of the monomer. Above results suggest that vacuum mixed method with monomer chilling at 4℃ before mixing of cement increase tensile and fatigue strength of acrylic bone cement, and decrease larger or small voids, and improve the longevity of cemented total hip arthroplasty.
백철수,박상원 고려대학교 의과대학 1992 고려대 의대 잡지 Vol.29 No.3
The os calcis that is the largest tarsal bone has most frequent incidence of fracture than any other tarsal bones. Extra-articular fractures of the calcaneus can be expected to heal rapidly and leave the patients with mimimal morbidity. However, intra-articular fractures involving subtalar joint are associated with long term disability. There is a great deal of controversy regarding treatment of intra-articular fractures of the calcaneus involving subtalar joint. The object of this study is to know relationship between the fracture pattern. methods of treatment and clinical results. and especially to assess clinical significans of restoration of Bo¨hler angle in displaced intra-articular fractures of the calcaneus. From January 1985 to December 1990, forty-nine cases of calcaneal fracture in 43 patients who were treated at Department of Orthopaedic Surgery, Korea Universty Hospital were analyzed in clinical and radiologic aspects. The minimal follow up was one year. Twenty-nine patients were male and fourteen were female. The most common age distrbution was 5th and 6th decade in twenty-four patients (55.8%). The most common cause of injury was a fall from height in thirty-eight patients (88.4%). The most common associated injury was spine fracture in nine cases (18.4%) out of forty-nine cases. There were type 1 in one case. type 2 in two. type 3 in nine, type 4 in six and type 5 in thirty-one according to Rowe's classification. Among 31 cases of Row's type 5, there were tongue type in sixteen cases and joint depression type in fifteen according to Essex-Lopresti's classification. The methods of treatment were closed reduction and axial pinning in thirty-four cases. long leg cast immobilization in eleven. open reduction and internal fixation in three. and triple arthrodesis of the foot in one. The avarage Bo¨hler angles were changed from 20.5 degrees to 30.5 degrees in Rowe's type 4. from 1 degree to 23.5 degrees in tongue type and from 6.3 degrees to 24 degrees in joint depression type after operation. The results obtained were as follows : 1. The clinical results were excellent in twenty-one cases, good in thirteen, fair in thirteen, and poor in two by criteria of Salama et al. 2. The clinical results according to fractures type were excellent or good in all twelve cases of extra-articular fractures of Rowe's type 1,2 and 3, and excellent or good in twenty-two cases among thirty-seven cases of intra-aricular fractures involving subtalar joint of Rowe's type 4 and 5. 3. The clinical results according to methods of treatment were excellent or good in twenty-one cases among thirty-four cases treated with closed reduction and axial pin fixation, in nine cases among eleven cases with long leg cast immabitization, and in all four cases of open reduction or triple arthrodesis. 4. Better results were taken from tongue type contrast to joint depression type at closed reduction and axial pinning. 5. The avarage Bohler angle according to clinical results were 31.7 degrees in excellent, 26.2 degrees in good, 22.0 degrees in fair and 13.8 degrees in poor. 6. The most common complication was pain around the ankle joint in sixteen cases (32%).