Unusual fracture dislocation of the craniovertebral junction.
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Atlanto-Axial Joint↗
Biomedical subjects
K C Cheung
Publications and source records attributed to K C Cheung.
Halo vest versus spinal fusion for cervical injury: evidence from an outcome study.
The indications for surgical fusion, as opposed to halo fixation, in the management of cervical spine injury are still unclear. At St. Louis University Medical Center a conservative protocol has been adopted to treat almost all cervical spine fractures with halo fixation. To determine what factors have contributed to failure of halo fixation, the records and radiographs of all patients with cervical spine injuries who were treated at that institution between 1984 and 1986 were reviewed. During this interval, 124 patients were treated, consisting of 93 men and 31 women between 6 and 94 years old. Of these, 15 (12%) had cervical fusion without preoperative halo device application. This group included eight patients with old injuries and delayed diagnosis, three with nonreducible locked facets, and four with miscellaneous indications. The remaining 109 patients were treated with halo vests. Four died before completing the 3-month standard treatment. Of those completing the treatment, 48 had C1-2 level injuries and 57 had C3-T1 level injuries. Sixteen patients (15%) failed their halo treatments and required surgical fusion: eight while still in halo fixation and eight after they had completed treatment with a halo device. Failure of halo treatment was indicated by recurrent dislocation in 13 patients and increased neurological deficit in three. Thirteen of the patients who failed treatment had C3-T1 injuries and three had C1-2 injuries. Of 27 patients with odontoid fractures, only two (7.4%) failed halo fixation. There were no failures in 11 patients with hangman's fractures. Of the 57 patients with C3-T1 injuries, 13 (23%) failed treatment, nine of whom had locked or "perched" facets. The factors causing failure of halo fixation were analyzed. The overall success rate was 85%, suggesting that the halo vest can be used to treat most patients with cervical spine injuries. Under certain circumstances (in the presence of old injuries, difficult reduction, or locked or "perched" facets), surgery may be indicated to avoid unnecessary delay in definitive management.
Adolescent↗
Risk assessment of heavy metal contamination in shrimp farming in Mai Po Nature Reserve, Hong Kong.
An ecological survey was carried out to determine the sediment concentrations of nutrients and heavy metals and bioaccumulation of heavy metals in fish and shrimp including tilapia (Oreochromis mossambicus x O. nilotica), grey mullet (Mugil cephalus), gei wai shrimp (Metapenaeus ensis) and caridean shrimp (Macrobrachium nipponensis) in the traditional tidal shrimp ponds (gei wais) of Mai Po Nature Reserve, Hong Kong. The sediments collected from the landward sites contained higher nutrient contents, as well as zinc (Zn), chromium (Cr), copper (Cu), nickel (Ni) and cadmium (Cd) than those collected from the seaward sites, but vice versa for lead (Pb) and mercury (Hg). However, the concentrations of all metals were exceptionally high in the two sites located outside the reserve, suggesting that waters from Deep Bay might be the possible source of metal contamination affecting the reserve. All metals studied seemed to accumulate in the viscera of fish. Body size was the determining factor for the accumulation of heavy metals in caridean shrimp and gei wai shrimp but not fish. Concentrations of the metals studied in tissues of grey mullet and gei wai shrimp were found to be safe for human consumption. Concentrations of Cr in tilapia whole body (0.68-1.10 mg kg(-1) wet weight) were close to or over the guideline value of 1 mg kg(-1) set by the Food Adulteration (Metallic Contamination) Regulations of Hong Kong. Tilapia flesh and small caridean shrimp collected from gei wais were contaminated by Cr and Pb but still fit for human consumption. Caution is required if large caridean shrimp is to be consumed in large amounts continuously because the concentration of Pb exceeded the maximum permitted concentration (6 mg kg(-1)). The rather high Cr concentrations in tilapia whole body should not be overlooked as the fish will serve as a food source for migratory birds visiting the site.
Animals↗
Kinetic studies on phosphorus sorption by selected soil amendments for septic tank effluent renovation.
A systematic kinetic study of phosphorus (P) sorption by various materials in the soil infiltration system of septic tanks was undertaken by following the time course of P sorption by sorbents in contact with various P solutions over periods up to 360 days. Uptake of P seemed to consist of two distinct stages. Initial uptake was very rapid and this phase was completed in 4 days or less. A slower removal stage followed for some materials over many months. Phosphorus sorption during the fast reaction stage appeared to be associated with the soluble Ca content of the materials. The fast reaction of calcareous materials accounted for the bulk (>70%) of the total P removed. Merribrook loamy sand exhibited the highest proportion of P sorption during the slow phase. It should be noted, however, that for solution P concentrations in the range found in typical effluents (approximately 20 mg L(-1)) the fast reaction phase seemed to be responsible for virtually all P removed. None of the six kinetic formulae examined possessed the sophistication and detail needed to portray accurately the time course of P sorption for all the sorbents investigated. The Elovich equation and the kinetic modification of the Freundlich isotherm expression appeared to provide a reasonable fit of the experimental data.
Absorption↗
Assessment of contamination by percolation of septic tank effluent through natural and amended soils.
Fly ash has been found to be a potential material for the treatment of municipal and industrial wastewater, and may be useful in the treatment of septic tank effluent. Laboratory columns (30 cm) were used to determine the sorption capacity and hydraulic properties of lagoon fly ash, loamy sand, sand, and sand amended by lagoon fly ash (30 and 60%) and red mud gypsum (20%). The removal of chemical oxygen demand (COD) was high in all column effluents (71-93%). Extent of nitrification was high in Spearwood sand, Merribrook loamy sand and 20% red mud gypsum amended Spearwood sand. However, actual removal of nitrogen (N) was high in columns containing lagoon fly ash. Unamended Spearwood sand possessed only minimal capacity for P sorption. Merribrook loamy sand and red mud gypsum amended sand affected complete P removal throughout the study period of 12 weeks. Significant P leakage occurred from lagoon fly ash amended sand columns following 6-10 weeks of operation. Neither lagoon fly ash nor red mud gypsum caused any studied heavy metal contamination including manganese (Mn), lead (Pb), zinc (Zn), cadmium (Cd) and chromium (Cr) of effluent. It can be concluded that Merribrook loamy sand is better natural soil than Spearwood sand as a filter medium. The addition of lagoon fly ash enhanced the removal of P in Spearwood sand but the efficiency was lower than with red mud gypsum amendment.
Adsorption↗