Clinical Presentations of Focal Choroidal Excavation and Results of Long-term Follow-up

PURPOSE: To evaluate the clinical presentations of focal choroidal excavation and to report long-term outcomes of cases without retinal disorders at the initial presentation. METHODS: A retrospective review of medical records was performed for patients diagnosed with focal choroidal excavation. Concomitant retinal disorders at the initial presentation were identified. In cases without retinal disorders, the development of retinal disorders during follow-up was also evaluated. RESULTS: Forty-five eyes in 45 patients were examined in this study. Focal choroidal excavation was accompanied with retinal disorders in 16 eyes (35.6%). In the remaining 29 eyes, only focal choroidal excavation was noted without any accompanying retinal disorders. The accompanying retinal disorders included choroidal neovascularization (n = 8), central serous chorioretinopathy (n = 4), epiretinal membrane (n = 1), macular hole (n = 1), branch retinal vein occlusion (n = 1), and uveitis (n = 1). Of the 29 eyes without retinal disorders, 22 were followed up for a mean period of 33.5 ± 18.2 months. Consequently, choroidal neovascularization was found to have developed in one eye at 59 months, and subretinal fluid had developed in two eyes at 17 and 28 months, respectively. CONCLUSIONS: Focal choroidal excavation was accompanied by retinal disorders in 35.6% of the included patients. In patients without retinal disorders, the development of a retinal disorder was noted in some eyes, suggesting the need for long-term regular follow-up in patients diagnosed with focal choroidal excavation.

The Clinical Characteristics of Spontaneous Separated Idiopathic Epiretinal Membrane

PURPOSE@#To investigate the clinical characteristics of spontaneous separation of idiopathic epiretinal membrane (ERM) patients without any surgical treatment.@*METHODS@#Retrospective medical records analysis was performed for patients with spontaneous separation of the idiopathic ERM without treatment. The patients' age, average time until ERM separation, best-corrected visual acuity (BCVA), refractive error, intraocular pressure (IOP), optical coherence tomography (OCT) data, central macular thickness (CMT), and the presence of posterior vitreous detachment (PVD) were evaluated and recorded.@*RESULTS@#Twenty-two eyes of 22 patients were included in the study. The mean age of patients was 52.0 ± 8.6 years, and the average time until ERM separation was 14.1 ± 16.2 months. The average BCVA (logMAR) was 0.12 ± 0.12 before separation and improved (p = 0.032) to 0.07 ± 0.08 after separation. The average CMT before separation was 386.1 ± 63.2 µm, after separation, the average CMT decreased (p < 0.001) to 299.1 ± 46.7 µm. The differences in IOP and refractive error before and after ERM separation were not statistically significant. Not all patients experienced PVD before ERM separation, however, they all showed PVD after the separation.@*CONCLUSIONS@#ERM patients of a relatively young age and without PVD showed spontaneous separation of the ERM and improved visual acuity with PVD, which suggests that ERM could be improved through conservative observation without surgery.

Evaluation of Stem Cell Components in Retrocorneal Membranes

The purpose of this study was to elucidate the origin and cellular composition of retrocorneal membranes (RCMs) associated with chemical burns using immunohistochemical staining for primitive cell markers. Six cases of RCMs were collected during penetrating keratoplasty. We examined RCMs with hematoxylin and eosin (H&E), periodic acid-Schiff (PAS) staining and immunohistochemical analysis using monoclonal antibodies against hematopoietic stem cells (CD34, CD133, c-kit), mesenchymal stem cells (beta-1-integrin, TGF-beta, vimentin, hSTRO-1), fibroblasts (FGF-beta, alpha-smooth muscle actin), and corneal endothelial cells (type IV collagen, CD133, VEGF, VEGFR1). Histologic analysis of RCMs revealed an organized assembly of spindle-shaped cells, pigment-laden cells, and thin collagenous matrix structures. RCMs were positive for markers of mesenchymal stem cells including beta-1-integrin, TGF-beta, vimentin, and hSTRO-1. Fibroblast markers were also positive, including FGF-beta and alpha-smooth muscle actin (SMA). In contrast, immunohistochemical staining was negative for hematopoietic stem cell markers including CD34, CD133 and c-kit as well as corneal endothelial cell markers such as type IV collagen, CD133 except VEGF and VEGFR1. Pigment-laden cells did not stain with any antibodies. The results of this study suggest that RCMs consist of a thin collagen matrix and fibroblast-like cells and may be a possible neogenetic structure produced from a lineage of bone marrow-derived mesenchymal stem cells.

The Study of Characteristics of Acellular Porcine Cornea Using Freezing-Thawing-Centrifugation

PURPOSE: To develop a new decellularization technique of porcine cornea using freezing-thawing-centrifugation (FTC) and to examine the characteristics of acellular porcine cornea (APC) for xenograft material. METHODS: Two-hundred micrometer thickness porcine corneas were decellularized with DNase/RNase, followed by 3 freezing-thawing-centrifugations (FTC, group 1), lyophilized FTC-APC (group 2), and chemical enzyme treated APC (CE-APC, group 3). Histologic evaluation to examine cells and collagen matrix, comparison of transparency, and cultivation to determine the viability of stromal cells was performed in fresh porcine cornea and 3 experimental groups. RESULTS: Decellularization occurred successfully in all experimental groups. Decellularization was confirmed by H&E staining and cultivation. Transparency of group 1 was similar to the normal porcine cornea but transparency of group 2 and group 3 was decreased. Collagen fibers of CE-APC (group 3) were not as well arrayed as FTC-APC (group 2). CONCLUSIONS: Acellularity of porcine cornea was successfully achieved by the FTC method with preservation of the cornea stroma. Novel decellularized porcine cornea can be considered as xenogeneic material for corneal transplantation.

A Congruous Superior Quadrantanopsia Following a Junctional Scotoma Induced by Asperogillosis

A 69-year old man presented to us with decreased vision in his right eye and a relative afferent pupillary defect. Under the presumption that he was suffering from retrobulbar optic neuritis or ischemic optic neuropathy, visual field tests were performed, revealing the presence of a junctional scotoma. Imaging studies revealed tumorous lesions extending from the sphenoid sinus at the right superior orbital fissure, with erosion of the right medial orbital wall and optic canal. Right optic nerve decompression was performed via an endoscopic sphenoidectomy, and histopathologic examination confirmed the presence of aspergillosis. The patient did not receive any postoperative antifungal treatment; however, his vision improved to 20 / 40, and his visual field developed a left congruous superior quadrantanopsia 18 months postoperatively. A junctional scotoma can be caused by aspergillosis, demonstrating the importance of examining the asymptomatic eye when a patient is experiencing a loss of vision in one eye. Furthermore, damage to the distal optic nerve adjacent to the proximal optic chiasm can induce unusual congruous superior quadrantanopsia.

Diagnosis and Treatment for Delayed Pseudoaneurysm of Deep Femoral Artery: A Case Report / 대한정형외과학회잡지

Post-traumatic arterial injuries are often reported in crushing or penetrating gun-shot injuries that include massive soft tissue damage. In most cases, the injured arteries are treated with early repair or reconstruction surgery. When there is a delayed in diagnosis, a pseudoaneurysm might be detected several weeks or months after the trauma. Pseudoaneurysms after femoral fracture are usually detected in the superficial femoral arteries, but rarely in the very deep femoral arteries, which are protected by the vastus medialis. There are many reports on post-traumatic pseudoaneurysms, most of which are in the superficial femoral arteries, and there are few reports with normal findings in an early angiogram. We report a pseudoaneurysm of the deep femoral artery with a normal angiogram in the early stage that was diagnosed and treated 4weeks after the trauma.

A Case of Ocular Surface Reconstruction Using Nasal and Oral Mucosa Autograft

PURPOSE: To report a case of ocular surface reconstruction using nasal and oral mucosa auto grafts on a man whose ocular surface was deformed by a chemical burn. CASE SUMMARY: A 48-year-old man was injured when his right eye was exposed to alkali solution. He underwent fifteen operations, including amniotic membrane auto grafts and fornix reconstructions. However, his right eye still suffered from symble pharon, drying, corneal neovascularization, and erosion. We performed ocular surface reconstruction with free autologous nasal and oral mucosal transplantation and amniotic membrane graft. By one month after surgery, his eye showed no evidence of symble pharon or fibrovascularization recurrence on the cornea or conjunctiva. By six months after surgery, his ocular surface had stabilized. CONCLUSIONS: Ocular surface reconstruction with free autologous nasal and oral mucosal transplantation is a useful method on eyes that are injured by chemical burns.

The Results of Treatment of Planovalgus Deformity by Modified Grice-Green Procedure / 대한족부족관절학회지

PURPOSE: The author modified the technique of Grice-Green, for managing flexible flat foot, with severe hindfoot valgus and possible dorsiflexion more than 15 degrees. The purpose of this study was to evaluate the efficacy and results of this modified technique. MATERIAL AND METHODS: Total of 6 patients, 11 cases of pes planovalgus were operatively managed with Modified Grice-Green procedure from Nov. 1996 to April 2002. Total 11 cases in 6 patients were managed; 9 cases in 5 males, 2 cases in one female. The average age of the patients were 7.3 years (5.1-13.3 years). Average follow up period was 3.9 years (1.2-6.7 years). Patients were evaluated preoperatively and at last follow up radiologically and clinically. Radiologic evaluation were done by measuring the talocalcaneal and talo-1st metatarsal angles with the anteroposterior view; and by measuring the talo-1st metatarsal angles with the lateral view. The clinical outcome were rated by subjective and objective improvement level. RESULTS: On follow up, 9 cases were complete satisfied, 2 cases were satisfied with minor reservation and no case had major reservations or dissatisfaction. Objective results were rated as excellent in 9 cases, good in 2 cases. Average preoperative talo-calcaneal and talo-1st metatarsal angles on anteroposterior radiograms were 34.4 degrees (16-40 degrees) and 32 degrees (8-48 degrees) respectively; which postoperatively on last follow up were 20 degrees (3-37 degrees) and 15.6 degrees (3-34 degrees) respectively. Average Preoperative talo-1st metatarsal angle on lateral radiogram was 18.4 degrees (6-30 degrees); which postoperatively on last follow up was 6.7 degrees (-6-17 degrees). CONCLUSION: Modified Grice-Green operative procedure is effective and satisfactory procedure for planovalgus deformity in children. but for more accurate results, more patients and further follow up period are needed.

Relationship of Risser Sign with Chronological Age, Menarche in Elementary, Middle, and High School Students in Korea / 대한정형외과학회잡지

PURPOSE: This study was undertaken to investigate the relationship between the Risser sign and chronological age and menarche in elementary, middle, and high school students, and to investigate the reliability of the Risser sign. MATERIALS AND METHODS: We reviewed 1, 870 spine standing AP X-rays, which included the iliac crest. We tried to identify a correlationbetween the Risser stage and chronological age, and between Risser stage and menarche. In addition, we investigated inter-observer error in the determination of Risser stage. RESULTS AND CONCLUSION: The mean ages of Risser 1, 2, 3 and 4 female students were 12.9, 13.3, 13.6, and 14.3 years, and the mean ages of Risser 1, 2, 3 and 4 male students were 14.0, 14.3, 14.5, and 15.6 years (Spearman's rho=0.560, p<0.01). The mean menarchal age of female students were 12 years 4 months, which is 7 months earlier than the mean chronological age of Risser 1 in female students. Wefound that it takes 24 months to progress from menarche to iliac crest maturation (Risser 4) (Spearman's rho=0.571, p<0.01). The percentage of agreement in the determination of Risser stage by three orthopaedic surgeons was 73.3%, showing good reliability with a Kappa value of 0.739-0.783.

The Residual Forefoot Adduction after Clubfoot-Surgery / 대한정형외과학회잡지

PURPOSE: To analyze the incidence and influencing factors of residual forefoot adduction after clubfoot-surgery. MATERIALS AND METHOD: A total of 133 clubfeet of 94 patients that had been surgically treated more than 3 years ago were followed up. For comparison purposes, we divided them into 3 groups. The first group was treated using a one-stage posteromedial release (PMR, 84 feet), the second group by posterolateral release (PLR, 34 feet), and the third group by medial release and lateral column shortening (Lichtblau, 34 feet). The forefoot adduction was characterized by Bleck's method and the effects of influencing factors, such as sex, laterality, methods of operation, and age at the time of operation were examined. Preoperative and postoperative calcaneocuboidal angles were also measured. RESULT: 40.2% of residual forefoot adduction was observed. Persistent grade 2 calcaneocuboidal malalignment showed 81.4% residual forefoot adduction. Forefoot adduction was unlikely to persist following posteromedial release procedure in the 1 to 2 year old age group. CONCLUSION: Age at the time of operation and the correction of calcaneocuboidal malalignment were significant factors for the development of residual forefoot adduction.

Osteofibrous Dysplasia of the Tibia in Children / 대한정형외과학회잡지

PURPOSE: To define the natural history and treatment of osteofibrous dysplasia, we compared the clinical courses of two groups: one group with a surgical treatment and the other group with a conservative treatment. MATERIALS AND METHODS: Seven cases (4 male, 3 female) were followed for more than two years (average f/u: 7 years 2 months). Four cases conservatively and three cases operatively by curettage and bone graft. Were treated the clinical and radiological findings of the two groups were compared. RESULTS: Two of three cases that received surgical treatment had been diagnosed with lesion recurrence by radiography, which showed expansion of the cortical shell, resorption of grafted bone, and reactive bone formation. One other case exhibited shrinkage and confinement of the lesion to the anterior cortex. Two cases, which were treated conservatively, showed shrinkage of the lesion and an other two cases showed no change in the size in radiogram. CONCLUSION: Asymmetrical intra-cortical osteolytic lesion of the tibia in children should be suspected as osteofibrous dysplasia and carefully observed until skeletal maturity, unless the structural integrity is seriously endangered.

Wear rate of polyethylene in hybrid Total Hip Arthroplasty / 대한정형외과학회잡지

PURPOSE: Articles reporting on the wear rate of polyethylene cup in hybrid THA are rare. So, we now report the results of wear rate of polyethylene in cementless Harris-Galante acetabular components and cemented Harris precoat femoral stem. MATERIALS AND METHODS: The cementless Harris-Galante acetabular components and cemented Harris precoat femoral stem of one-hundred hips in 71 patients were followed up for 2.5 ~ 7.5 years (mean 4.7 year) . The clinical results were evaluated by Harris hip score (HHS) and wear rates were measured using Livermore technique. RESULTS: The most recent follow-up of HHS was improved from 52 to 91 in average. The mean linear wear rate in cemetless acetabular component was 0.17 0.06mm/yr (range 0.05 ~ 0.35) . Two femoral components were revised for aseptic loosening and one acetabular component revised for aseptic loosening. Wear rate in the revision group was higher than mean wear rate. In chronological change of wear rate according to final follow up period, there was decreasing tendency for mean wear rate with time. There was no correlation found between mean wear rate and body weight. There was a decreasing tendency on mean wear rate with acetabular cup shell size and increasing tendency with level of activity. CONCLUSION: We concluded that cemented femoral stem was the reason for the trend in lower wear rate of polyethylene cup than which had been previously reported in cementless THA, but further follow-up studies will be needed to confirm that.

Lipid Profile in Patients with Osteonecrosis of the Femoral Head / 대한정형외과학회잡지

PURPOSE: Many articles have proposed that osteonecrosis of the femoral head (ONFH) is caused by fat embolism or intravascular coagulation linked to hyperlipidemia. To determine whether hyperlipidemia is an associated factor for ONFH, serum lipid levels were measured. MATERIALS AND METHODS: Nighty-eight patients presenting with ONFH and 110 controls were investigated. We compared the average value of serum lipid levels and the incidence of hyperlipidemia of the two groups. RESULTS: ONFH group showed generalized increase in lipid level and statistically significant difference in the average value of total cholesterol (P=0.0001), HDL-cholesterol (P=0.0261) and phospholipid (P=0.0465) compared with the control. The incidence of hyperlipidemia of the two groups showed statistically significant difference in HDL-cholesterol (P=0.019) and triglyceride (P=0.024). CONCLUSION: Hyperlipidemia seems to be associated with pathogenesis of ONFH. We speculated that hyperlipidemia might be a contributing factor of ONFH. Hyperlipidemia may play a role as a triggering factor in the pathogenetic process that results in osteonecrosis. However, it can not be ruled out that secondary hyperlipidemia might be a finding following ONFH.

Physeal Injuries in Association with Severe Osteoporosis / 대한정형외과학회잡지

The physeal injuries in children occur result of trauma, infection, metabolic or ischemic disease, and these conditions cause significant problems, such as growth disturbance, deformity and premature closure of physis. The authors experienced 7 cases of children who had angular deformity of knee and limb shortenings, but no history of obvious causes of physeal injury. All of these cases had severe osteoporosis and underlying disease, which were osteogenesis imperfecta, fibrous dyplasia and long term steroid therapy. The purpose of this study are evaluation of pathomechanism of physeal injuries in severe osteoporotic children. Patients were range of age from 4 to 9 years and had common clinical features, which were angular deformities of knee, limb shortening. Also they had common radiographic findings, that were severe porosis, metaphyseal sclerosis and in some cases, pop corn like calcification around physis. At this, we supposed that chronic mechanical stress in osteoporotic bone make physis be damaged due to loss of capillary circulation and this event appear to result from collapse of bone plate, through which epiphyseal vessel penetrate. In conclusion, the children with severe osteoporosis should be observed carefully about physeal injuries, which pathomechanism are perhaps deprivation of capillary circulation through bone plate. Therefore, We should try to protect bone plate by being conscious of its existence.

The Significance of Teardrop Changes in Developmental Dislocation of the Hip / 대한정형외과학회잡지

Prediction of acetabular development after reduction in treatment of developmental dysplasia of thc hip (DDH) is earlier, the hetter results because it would help ensure optimal timing of additional procedure if necessary. In this respect, authors reviewed retrospectively the radiographs of the hips of 35 children with DDH who had unilateral involvement and treated hy senior author (S.H.Lee) from the heginning with single successful attempt of reduction. The radiographs which were made at the time of initial diagnosis, one, two year nfter reduction und final follow up were assessed of teardrop figures. The results of treatment were classified as satisfactory group(CE > 10degrees ) and unsatisfactory group(CE < 10degrees) judged hy center-edge angle(CE degrees) at final follow-ups. 1. The teardrop figures were classifiable into 4 distinct groups as i)absent. ii)V-shaped, iii)Ushaped, iv) inverted D-shaped. 2. The teardrop figures in normal sides of hip were all U-shaped. 3. In dislocated but with satisfactory result group(24 cases), absent at 2 cases(8%), U-shaped teardrop was seen at 13 cases(54%), V-shaped in 9 cases(38%), and inverted 2-shaped in 0 case at I year after reduction. 4. In dislocated but with unsatisfactory result group( 11 cases), they were mostly of V-shaped(7 cases, 64%). The rest were of ahsent in 4 cases(36%) . hut none of U-shaped and inverted 2-shaped. In conclusions, teardrop figures appeared as significant predictor of future development of hip joint. Teardrop figure which stay as V-shaped at one year after reduction seems suggestive of insufficient reduction of DDH, therehy calls for early additional procedure.

An Experimental Study about the Effects of Parathyroid Hormone on Strength of Vertebra and Bone Density of Proximal Tibia in Ovariectomized Rats / 대한정형외과학회잡지

Parathyroid hormone (PTH) has not been studied as extensively as therapeutic agents of osteoporosis, but the anabolic effect of parathyroid hormone on the skeleton has been demonstrated in several studies. The current study was undertaken to assess the effect of parathyroid hormone on bone mass and its biomechanical competence using ovariectomized rat model. Fifty female Sprague Dawley rats of 3 months old were randomized into five groups, 10 in number for each groups. Group I: sham-operation, Group II: ovariectomy (OVX) plus saline injection, Group III: OVX plus PTH 20ug/kg, Group IV: OVX plus PTH 40ug/kg, Group V: OVX plus PTH 80ug/kg. Treatment regimens were initiated 8 weeks after ovariectomy and continued for 4 weeks thereafter. Bone mineral density was measured in proximal one-third level of tibia by dual energy X-ray absorptiometry (QDR-2000, Hologic, U.S.A). Biomechanical competence was assessed in lumbar vertebral body by universal testing machine (Instron-4467, U.S.A). The average of bone mineral density in sham operated group was 0.088+/-0.0084g/cm (2), and in control group (OVX +/- saline)was 0.065+/-0.0095g/cm (2). Bone mineral density decreased in control group significantly. The average of bone mineral densities in Group III, IV, V (OVX + PTH) were 0.071+/- 0.0089, 0.081+/-0.0086 and 0.084+/-0.0093g/cm (2), respectively. This showed that parathyroid hormone injected groups had significantly higher bone mass than control group (p<0.0#5), and the increment was in proportion to the amount of parathyroid hormone in the range (p<0.05). The average of biomechanical competence of lumbar vertebral body in sham operated group was 30.036.24 MPa and was 25.11+/-5.69 MPa in control group. In Group III, IV,V they were 25.74+/-6.77, 27.96+/-5.17 and 29.83+/-5.79 MPa, respectively. Above results seem supportive of the phenomenon that parathyroid hormone exert anabolic effect on osteoporotic bones in certain experimental condition.

Treatment of the Pyogenic Arthritis of Hip in Neonates and Infants / 대한정형외과학회잡지

Septic arthritis of hip is a serious problem. Delay in diagnosis and treatment can results in crippling. From September 1983 to May 1993, we have experienced 17 cases of pyogenic arthritis of the hip in neonates and infants. Ten cases were under the age of 1 month old, four were from 1 month to 2 months, and the rest of 3 cases were 11 months old with depicting high incidence in neonates within 1 month. Laboratory findings according to lag periods were as follows; The patients group (n=9) who visited within 3 days after symptom onset manifested high fever (over 38oC) in 2 cases only and 7 cases revealed normal or mild fever. The patients group (n=8) being seen later than 3 days showed high fever in most of cases. Leukocytosis was mostly unspecific in both groups. The average WBC counts tested on admission were 16,052/mm3, ESR 38.3mm/hr,and WBC count dropped to 11,264/mm3, ESR to 27.3 mm/hr after operation. Microbial culture was positive in 10 cases (58.8%), of which 4 were staphylococcus, 5 were streptococcus and 1 was ancinetobacter. Surgical drainage was done through the posterior approach. Long term follow up showed no recurrence and severe complications such as dislocation of head, avascular necrosis and osteomyelitis of proximal femoral metaphysis In conclusion, pyogenic arthritis of hip occurred more common in neonates less than month old and laboratory findings were not always accompanied by fever and hematologic changes especially when the symptom onset was less than 3 days.

A Case of Spondylometaphyseal Dysplasia ( Kozlowski type ) / 대한정형외과학회잡지

Spondylometaphyseal dysplasia (SMD) is an extremely rare, which affects the spine and metaphy-ses of the tubular bones on terms of enchondrogenesis. Children who had Kozlowski dwarfism, type of SMD are not recognized until they reach school age since they have normal clinical feature, weight and size in early childhood. Authors experienced a typical case of Kozlowski type of SMD in a 10 years old male who had i) generalized platyspondyly with anterior tapering of vertebrae ii) generalized metaphyseal dysplasia iii) minimal changes in the carpal and tarsal bones. This case is to be reported with review of references.

An Experimental Study about the Effects of Parathyroid Hormone on Osteoblasts / 대한정형외과학회잡지

Authors concluded an experimental study in order to find out what the effects of parathyroid hormone on cells derived from human Trabecular bone in vitro are on terms of proliferation of cells, adenylate cyclase activity and production of small substances such as osteocalcin and collagen type I. The results were as follows; 1. 3H-thymidine incorporation into cultured osteoblast was initially low (day 1–2), increased by exponential curve from day 3 till day 11. The uptakes of 3H-thymidine by osteoblasts, when bovine parathyroid hormone was added, increased dose-dependently. Greater increments were seen at concentrations of bovine PTH higher than 5.0 X10-8 mole. 2. Intracellular c-AMP accumulation was stimulated by bovine PTH in a dose-dependent manner and greater production was seen at concentrations of bovine PHT higher than 5.0 X10-8 mole. Maximal stimulation was observed at 1 X10-7 mole of bovine PTH. The concentrations of c-AMP were observed significantly higher in the presence of bovine PTH in a dose-dependent manner when compared to those of bovine PTH-absent culture condition. 3. Treatment with bovine parathyroid hormone of cultured osteoblasts resulted in increase of alkaline phophatase activity and synthesis of osteocalcin in the cultured media in a dose-dependent manner. Greater productions were observed at concentrations of bovine PTH higher than 5.0 X10-8 mole. 4. Synthesis of type I collagen by cultured osteoblasts in bovine PTH-added media was inversely proportional to their concentration, whereas control group showed minimal increments of no significance. These in vitro findings may suggest that PTH has a stimulatory effect on proliferation of osteoblast, c-AMP production and alkaline phosphatase activity in a direct manner.

An Experimental Study of the Effect of Vacuum Mixing on Fatigue Characteristics of Acrylic Bone Cement / 대한정형외과학회잡지

Contemporary cementing techniques improved the longevity of the cemented total hip replacement. The mechanical strength of acrylic bone cement can be changed by different handling techniques with reduction of the porosity of acrylic bone cement. The greatest improvement of the mechanical properties with reducing the porosity is that of the fatigue strength. We investigated the mechanical properties of the specimens of high viscosity, Palacos R(Merk, Darmstadt, FRG) bone cement with two mixing methods, hand and vacuum mixing. Vacuum mixing improved the ultimate tensile strength by 22.4% compared to hand mixing in previous study. For the uniaxial tension fatigue test, the specimens were cyclically loaded at a maximum stress of 25 MPa at a frequency of 2.5 Hz and to investigate the porosity, scanning electromicroscopic examination was taken in each hand mixed and vacuum mixed specimens. Scanning electromicrogram showed the vacuum mixed specimens to be the more uniform and free of small voids compared with the hand mixed specimens. The results of the fatigue test were analized using Weibull distribution of survival probability, the average number of cycles to failure was 1459±924 cycles in hand mixed specimens, in vacuum mixed specimens, 21491±14956 cycles. The average fatigue life of the vacuum mixed specimens was 15 times loanger than that of the hand mixed specimens by Weibull mean, this differene exists stastically within 95% confidence interval. We could suggest vacuum mixing technique as a method eliminating porosity in a chilled acrylic bone cement and thereby markedly improving the mechanical properties. In cemented joint replacement surgery, a vacuum mixing technique are recommended as a method of preparation of acrylic bone cement