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Biomedical subjects

C W Cha

Publications and source records attributed to C W Cha.

8 recordsLinked to original sources
PubMed2000

Quantitative analysis of ultrahigh molecular weight polyethylene (UHMWPE) wear debris associated with total knee replacements.

The size and morphology of particulate wear debris retrieved from tissues around 18 failed total knee replacements (TKR) were characterized. Interfacial membranes from nine cemented and nine uncemented TKR were harvested from below the tibial components during revision surgery. Wear debris were extracted using papain and potassium hydroxide digestion. Ultrahigh molecular weight polyethylene (UHMWPE) particles from around cemented or uncemented TKR were similar in size and morphology. The mean size was 1.7 +/- 0. 7 microm with a range of 0.1-18 microm. Thirty-six percent of the particles were less than 1 microm and 90% were less than 3 microm. Morphologically the particles were predominantly spherical with occasional fibrillar attachments and flakes. Particles from TKR were greater than threefold larger than previously characterized particles from total hip replacements, which were 0.5 microm in mean size. Differences in joint conformity and wear patterns between the hip and knee articulations may explain the disparity in size of the wear debris. Since particle size represents an important variable influencing the magnitude of the biological response, it is possible that in vivo the larger TKR debris results in a diminished mediator release, which in turn may account for the lower incidence of osteolysis and aseptic loosening in some designs of TKR.

Aged↗
PubMed1998

Failure of total hip arthroplasty with a precoated prosthesis. 4- to 11-year results.

A series of early femoral component failures prompted a detailed retrospective clinical and radiographic review of 176 hybrid cemented total hip arthroplasties using a polymethyl-methacrylate coated femoral prosthesis. All surgeries were performed using third generation cement techniques. Average length of followup was 6.3 years (range, 3-12 years). Twenty-one patients died, and one underwent revision surgery because of sepsis. Of the remaining 154 total hip arthroplasties, 23 (15%) of the femoral components failed (21 revised, two definitely loose). The average time to revision was 3.9 years. None of the acetabular components failed. Comparison between the failure and nonfailure groups revealed that poor cement mantles (Grades C or D) with distal cement mantle deficiencies were statistically significant predictors of femoral failure. The most common mechanism of failure was progressive, circumferential cement-bone interface osteolysis with relative preservation of the cement-metal interface. Debonding of the cement column from the prosthesis was a late finding and occurred in only 45% of failed cases. Incorporating the techniques of centralization and centrifugation significantly improved clinical results. Strengthening of the cement-prosthesis interface may magnify the deleterious effects of a poor cement mantle and predisposes the cement-bone interface to failure.

Aged↗
PubMed1996

Biomechanical consequences of replacement of the anterior cruciate ligament with a patellar ligament allograft. Part II: forces in the graft compared with forces in the intact ligament.

Seventeen fresh-frozen knee specimens from cadavera were instrumented with a load-cell attached to a mechanically isolated cylinder of subchondral bone containing the tibial insertion of the anterior cruciate ligament. The forces in the intact anterior cruciate ligament were recorded as the knee was passively extended from 90 degrees of flexion to 5 degrees of hyperextension without and with several constant tibial loads: 100 newtons of anterior tibial force, ten newton-meters of internal and external tibial torque, and ten newton-meters of varus and valgus moment. The anterior cruciate ligament was resected, and a bone-patellar ligament-bone graft was inserted. The knee was flexed to 30 degrees, and the graft was pre-tensioned to restore normal anterior-posterior laxity. The knee-loading experiments were repeated at this level of pre-tension (laxity-matched pre-tension) and at a level that was forty-five newtons greater than the laxity-matched pre-tension (over-tension). During passive extension of the knee, the forces in the graft were always greater than the corresponding forces in the intact anterior cruciate ligament. Over-tensioning of the graft increased the forces in the graft at all angles of flexion. At full extension, the mean force in the anterior cruciate ligament was fifty-six newtons; the mean force in the graft at laxity-matched pre-tension was 168 newtons, and it was 286 newtons in the over-tensioned graft. Greater pre-tensioning may be required when the knee demonstrates apparent tightening of the graft in flexion. The mean forces in the graft generated during all constant loading tests were greater than those for the intact anterior cruciate ligament over the range of flexion. When the graft was over-tensioned, the forces generated by the anterior tibial force and by varus and valgus moment increased but those generated by internal and external tibial torque did not. There was no significant change in the mean tibial rotation as a function of the angle of flexion of the knee after insertion of the graft; normal tibial rotation of the knee during passive extension (the so-called screw home mechanism) was eliminated.

Anterior Cruciate Ligament↗
PubMed1993

An outbreak of Heinz body positive hemolytic anemia in chronic hemodialysis patients.

During the four month period, from December 1988 to March 1989, there was an outbreak of Heinz body positive hemolytic anemia in 34 patients undergoing hemodialysis in a 500-bed hospital, Seoul, Korea. The episodes of hemolysis were not reduced by changing the charcoal column and reverse osmosis system, or by adding ascorbic acid to the dialysate. The concentrations of nitrate, copper, aluminum and zinc in the treated water were all within the standards for hemodialysis. The chloramine concentration of the treated water was over 0.6 mg/L, markedly exceeding the allowable level of 0.1 mg/L. This high level of chloramine was proved to be due to the contamination of the water source by raw sewage. After we changed the source of water supply to another, no more episodes of hemolytic anemia occurred. It is concluded that chloramine is one of the major contaminants causing dialysis-induced hemolytic anemia and regular determinations are necessary, especially during winter and dry seasons.

Anemia, Hemolytic↗
PubMed1987

A study on the effect of garlic to the heavy metal poisoning of rat.

When garlic (Allium sativum) was administered to rat per os simultaneously with cadmium, methylmercury and phenylmercury to detect the protective effect against the heavy metal poisoning, accumulation of heavy metals in liver, kidneys, bone and testes were decreased, and histopathological damages and the inhibition of serum alkaline phosphatase activities by heavy metals were reduced. Such effect of garlic was not shown in the 1.7% garlic treated group and most remarkable in the 6.7% garlic treated group. The protective effect of garlic was superior to those of 2,3 dimercapto-1-propanol (BAL) and D-penicillamine (PEN), and nearly similar to those of 2,3-dimercaptosuccinic acid (DMSA) and N-acetyl-DL-penicillamine (APEN), the current remedies, while garlic was not effective as a curative agent for heavy metal poisoning. The excretion of cadmium was enhanced, more through feces than urine by garlic but the effect to the urinary excretion of cadmium was not significant comparing with DMSA or APEN when cadmium was ip injected in the first 3 days during the 12 days of oral administration of DMSA, APEN or garlic.

Animals↗
PubMed1984

Occupational burns.

Certain occupations cause particular kinds of burn. Minor burns are usually neglected. Observation of industrial workers during routine annual medical examination found many workers with minor occupational burns and their sequalae. Some were so characteristic that they can be regarded as occupational marks.

Burns↗