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Biomedical subjects

K M Cheung

Publications and source records attributed to K M Cheung.

At least 19 recordsLinked to original sources
PubMed2006

The Toronto Western Hospital catheter: one center's experience and review of the literature.

BACKGROUND: We report our center's experience with the Toronto Western Hospital (TWH) catheter, and discuss our catheter survival and complication rates. METHODS: Retrospective chart review of patients receiving peritoneal dialysis therapy via a TWH catheter. Catheter complication rates of peritonitis, exit site infection, obstruction, leak, and malfunction were assessed. A catheter was considered failed if removed because of exit site infection, obstruction, or malfunction. All other catheters, even if removed for other reasons, were considered censured. Survival was defined as the period from insertion to failure or censure date, and reported using Kaplan Meier analysis. RESULTS: 192 patients with a total of 208 TWH catheters (4,845.3 catheter months) were analyzed. Our overall 1- and 3-year catheter survival rates were identical at 0.9182. Our catheter complication rates (expressed as number of catheter months per event) were 31.3 for peritonitis, 42.9 for exit site infection, 72.3 for obstruction, 538.4 for malfunction, and 969.1 for catheter leak. Our findings were similar to those reported in the literature for TWH and other peritoneal catheters.

Catheters, Indwelling↗
PubMed2006

Nissen fundoplication and gastrostomy in severely neurologically impaired children with gastroesophageal reflux.

OBJECTIVES: To study the effect of Nissen fundoplication and gastrostomy in severely neurologically impaired children. DESIGN: Prospective observational study. SETTING: Developmental Disabilities Unit of a regional medical centre in Hong Kong. PATIENTS: Children with severe neurological impairment and gastroesophageal reflux who were institutionalised between 1999 and 2004 inclusive. MAIN OUTCOME MEASURES: Incidence of vomiting, gastro-intestinal bleeding, and pneumonia in the baseline year and consecutive years following surgery; 24-hour oesophageal pH monitoring; recurrence rate (determined by 24-hour oesophageal monitoring); body weight; complications of surgery; and mortality. RESULTS: Twenty children, with a mean age at surgery of 8.5 (standard deviation, 3.5) years, were recruited. Nissen fundoplication was performed in nine children and 11 children underwent laparoscopic fundoplication. Children were monitored for 1.3 to 5.7 years (median, 3.5 years) after surgery. The incidence of vomiting and gastro-intestinal bleeding was significantly decreased following surgery (P < 0.001 and P = 0.001, respectively; Friedman's test). There was no difference between the preoperative and postoperative incidence of pneumonia (P = 0.973, Friedman's test). The median reflux index was reduced from 5.7% to 0.15% after surgery but six (30%) patients had recurrent gastroesophageal reflux. The mean body weight was 17.4 kg (standard deviation, 4.7 kg) at baseline and 22.8 kg (standard deviation, 4.4 kg) at the end of follow-up (P < 0.05, Student's t test). One patient had mild dumping syndrome soon after fundoplication. One patient had one episode of intestinal obstruction. Four patients died 1.9 to 5.0 years following surgery due to respiratory disease. CONCLUSION: Our results indicate that in severely neurologically impaired children with gastroesophageal reflux, vomiting, gastro-intestinal bleeding, and reflux indices based on 24-hour oesophageal pH monitoring were significantly reduced following fundoplication and gastrostomy. The incidence of pneumonia was unchanged. The recurrence rate of reflux was 30% and mortality rate was 20%.

Adolescent↗
PubMed2001

Bioactive bone cement as a principal fixture for spinal burst fracture: an in vitro biomechanical and morphologic study.

STUDY DESIGN: An in vitro biomechanical and radiographic study to evaluate the properties of a newly developed bioactive bone cement for stabilization of the fractured spine, suitable for minimally invasive application. OBJECTIVES: To determine the mechanical stability of the fractured spine after injection of the newly developed bioactive bone cement under quasi-static and cyclic loading regimens. SUMMARY OF BACKGROUND DATA: Bone cement injection has been reported as a potentially useful, minimally invasive technique for treating vertebral body fracture or stabilizing osteoporosis. However, potential problems associated with the use of polymethylmethacrylate (PMMA) have prompted the search for alternative solutions. The use of bioactive bone cement as a potential replacement for PMMA has been reported. METHODS: Biomechanical and radiographic analyses were used to test the mechanical stability of the fractured spine. The cement used was formed from hydroxyapatite powder containing strontium and bisphenol A diglycidylether dimethacrylate (D-GMA) resin. Twenty-six fresh porcine spine specimens (T10-L1) were divided into three groups: pilot, intact, and cemented. Spinal stiffness and failure strength were recorded in the intact group with the specimens flexed at 10 degrees. Uniform injuries were created in all specimens of the cemented group, and compressive loading was applied with 10 degrees of flexion until a fracture occurred. The bone cement was injected into the fractured spine, and stiffness was evaluated after 1 hour. Failure strength was also recorded after 3000 and 20,000 fatigue load cycles. Morphology of the specimens was observed and evaluated. RESULTS: Results from a cell biocompatibility test indicated that the new bioactive bone cement was favorable for cell growth. Spinal stiffness significantly decreased after fracture (47.5% of intact condition). Instant stiffness of the spine recovered to 107.8% of the intact condition after bone cement injection. After 3000 and 20,000 cycles of fatigue loading, stiffness of the cemented spine was found to be 93.5% and 94.4% of intact stiffness, respectively (P < 0.05). Average failure strength of the spine was 5056 N (after 3000 cycles) and 5301 N (after 20,000 cycles) after bone cement injection and fatigue loading. Radiographs and cross-sectional observations indicated a good cement-bone bonding and fracture fill. CONCLUSIONS: A new bioactive bone cement without cytotoxic effect has been developed. Results show that minimally invasive techniques to apply this cement to porcine spines results in augmentation of mild burst fractures such that the original stiffness and strength of the vertebra are recovered. This new cement therefore shows potential as an augmentation to traditional instrumentation in the surgical management of vertebral fractures. The potential for further clinical applications is currently under investigation.

Animals↗
PubMed2001

Evaluation of various evoked potential techniques for spinal cord monitoring during scoliosis surgery.

STUDY DESIGN: This prospective study compared the outcomes of different evoked potential (EP) techniques for intraoperative spinal cord monitoring. OBJECTIVES: To evaluate the reliability of different EP techniques administered during scoliosis surgery. SUMMARY OF BACKGROUND DATA: A number of different methods of intraoperative spinal cord monitoring are available. Because each has its own advantages and limitations, multimodal spinal cord monitoring has been proposed to improve monitoring reliability. MATERIALS AND METHODS: Cortical somatosensory-evoked potential (CSEP), cortical motor-evoked potential (CMEP), spinal somatosensory-evoked potential (SSEP), and spinal cord-evoked potential (SCEP) were applied simultaneously to 30 patients undergoing surgical correction for spinal deformity. The presence of the EP waveforms and their reproducibilities over separate tests were compared. In addition, the monitoring outcomes were evaluated with the clinical results. RESULTS: Of the 30 patients, CSEP waveforms were successfully recorded in 28 cases (93%), SCEP in 25 cases (83%), CMEP in 24 cases (80%), and SSEP in 21 cases (70%). Latencies of each EP technique showed no significant variability. However, amplitudes showed significant differences between different techniques. SCEP and CMEP showed clearer waveforms of greater amplitude that could be detected faster than CSEP and SSEP waveforms. SCEP and SSEP waveforms were more easily influenced by the surgical procedure. CONCLUSION: CSEP and CMEP are recommended for routine monitoring, so that both ascending and descending tracts are monitored. If adequate signals for either of these proposed monitoring methods cannot be easily obtained, SSEP can substitute for CSEP, whereas SCEP can substitute for CMEP.

Adolescent↗
PubMed2001

Pancreatitis associated with Henoch-Schonlein purpura.

A 7-year-old Chinese boy presented with acute pancreatitis. The characteristic rash of Henoch-Schonlein purpura (HSP) did not develop until nine days later, together with painful scalp swelling and calf pain. Acute pancreatitis has only rarely been reported in association with HSP and never before as the sole presenting feature.

Acute Disease↗
PubMed2001

Correction method for determining anteroposterior diameter of the cervical spinal canal on lateral radiographs.

SUMMARY: Measurement of the anteroposterior diameter of the cervical spinal canal may prove unreliable because of the rotatory effect of degenerative disease. Nevertheless, this measuring error may be corrected by performing dual midpoint measurements between the posterior vertebral body and spinolaminar line when less than 10 degrees of rotation is present.

Analysis of Variance↗
PubMed2001

Back muscle contraction patterns of patients with low back pain before and after rehabilitation treatment: an electromyographic evaluation.

The aims of this study were to conduct a comparative investigation of muscle function between patients with low back pain (LBP) and healthy persons, and to determine whether intensive rehabilitation can change back muscle contraction synergy. Twenty healthy persons and 20 patients with chronic LBP were asked to perform symmetrical and asymmetric tasks. The patients with LBP were tested in the weeks immediately before and after 12 weeks of LBP rehabilitation. Tasks include "carrying" weights up and down and with a 45 degrees left rotation. Eight-channel surface electromyographic electrodes were placed on the surface of paraspinal muscles over the lumbar region. Correlations between the right and left corresponding muscles and between values before and after treatment were determined. Lifting capacity for patients with LBP were also measured before and after treatment. Results from electromyographic profiles showed that the muscle activity strategies varied between healthy persons and patients with LBP. The correlation coefficients for spinal muscles have shown very reproducible intrasubject muscle contraction synergies. Unbalanced electromyographic patterns found in patients with LBP given symmetrical tasks were not affected by rehabilitation treatment.

Adult↗
PubMed2001

Clinical efficacy of proton pump inhibitor therapy in neurologically impaired children with gastroesophageal reflux: prospective study.

OBJECTIVE: To study the effects of proton pump inhibitors in reducing vomiting, gastrointestinal bleeding, and chest infections in institutionalised neurologically impaired children with gastroesophageal reflux. DESIGN: Prospective study. SETTING: A regional hospital, Hong Kong. PATIENTS: Neurologically impaired children with refractory gastroesophageal reflux. MAIN OUTCOME MEASURES: Episodes of vomiting, gastrointestinal bleeding, and pneumonia in the baseline and proton pump inhibitor treatment periods. RESULTS: Nine children received proton pump inhibitor therapy for a median duration of 81 days. Mean reflux index was 9.3% (standard deviation, 5%). Dosage of omeprazole used was 1.0-2.3 mg/kg/d. Vomiting was reduced significantly with proton pump inhibitor treatment (median vomiting index [baseline]=0.4, median vomiting index [proton pump inhibitors]=0.2; P<0.05). No significant decrease in gastrointestinal bleeding or chest infection was observed. CONCLUSION: Proton pump inhibitors significantly reduced vomiting episodes in neurologically impaired children with gastroesophageal reflux.

Child↗
PubMed2000

A novel injectable bioactive bone cement for spinal surgery: a developmental and preclinical study.

The injection of bone cement by minimally invasive techniques for the treatment of vertebral body fractures or for stabilization of an osteoporotic vertebral body is regarded as promising in spinal surgery. The purpose of this study was to develop a novel injectable bioactive bone cement to address such concerns. The cement was composed mainly of strontium-containing hydroxyapatite (Sr-HA) filler and Bisphenol A Diglycidylether Dimethacrylate (D-GMA) resin. The Sr-HA filler was prepared by precipitation and calcination, then analyzed with Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns. Samples of strontium-containing hydroxyapatite cement (SrHAC) were formed by a combination of powder filler and resin matrix, with the setting time and peak temperature recorded. Cell relative growth rate (RGR), Tetrazolium bromide (MTT), and haemolysis tests were used to detect initial in vitro biocompatibility of the new cement. In vitro spinal biomechanical testing and morphological observation after bone cement injection were performed on pig spines. Results indicate that the setting time and peak temperature of the cement was 15 min and 55 degrees C, respectively. Cytotoxicity of the cement was class 1 (no cytotoxicity) and haemolysis was 1% (no haemolysis). Stiffness after cement injection and fatigue loading were 112% and 95% of the intact bone, respectively, which is similar to that of natural bone. Radiopacity of SrHAC allowed easy radiographic imaging. The use of SrHAC cement is, thus, promising in spinal surgery.

Animals↗
PubMed1998

Assessment of scoliosis correction in relation to flexibility using the fulcrum bending correction index.

STUDY DESIGN: A prospective study on adolescent idiopathic scoliosis to assess a new method of describing frontal plane correction. OBJECTIVE: To assess the difference between using the correction rate and using the new fulcrum bending correction index when describing scoliosis correction. SUMMARY OF BACKGROUND DATA: A description of the outcome of scoliosis surgery based on the correction rate does not take into account the curve's flexibility. METHODS: The fulcrum bending correction index is calculated by dividing the correction rate by the fulcrum flexibility (based on the fulcrum bending radiograph) and is expressed as a percentage. The fulcrum bending correction index was compared with the correction rate in 35 patients with adolescent idiopathic scoliosis undergoing surgical correction. These patients were divided into a stiff and a flexible group based on a fulcrum flexibility of 50% to show the advantage of the fulcrum bending correction index over the correction rate. RESULTS: The difference in correction rate between the flexible (66%) and the stiff group (45%) was significant (P < 0.05). The difference in the fulcrum bending correction index between the flexible (96%) and the stiff group (107%) was not significant (P = 0.2). CONCLUSIONS: The fulcrum bending correction index takes into account the curve flexibility and is therefore better than the correction rate for comparing curve correction and use of instrumentation systems between different series of patients. A fulcrum bending correction index of close to 100% suggests that the instrumentation has taken up all the flexibility revealed by the fulcrum bending radiograph. It is recommended that the fulcrum bending correction index be used in the future as part of the postoperative assessment of frontal plane correction in cases of thoracic scoliosis.

Adolescent↗
PubMed1998

Intra-articular injection of ketorolac in the rat knee joint: effect on articular cartilage and synovium.

We have investigated the effects of intra-articular (i.a.) administration of ketorolac in the rat knee joint. Thirty Sprague-Dawley rats were given 0.25 ml of a standard preparation of ketorolac trometamol (10 mg ml-1) by injection into the right knee joint and 0.25 ml of 0.9% physiological saline solution by injection into the left knee as a control. Ten rats were killed at 24 h, 10 at 48 h and 10 at 5 days after injection. The joints were prepared and sectioned for histological examination. There was significantly more inflammation in those knees that had received i.a. ketorolac at all times of examination, with the most severe changes occurring 5 days after injection. A further group of 10 rats were given 0.25 ml of 10% w/v ethanol in physiological saline (similar to the vehicle for parenteral ketorolac) injected into the knee joint, with a 0.9% saline control injected in the other knee. These rats were then killed at 5 days (as this was the time interval after which we found the maximum inflammatory response in the earlier phase of our study). The joints were prepared and examined histologically. We feel that the absence of inflammatory changes in these joints make it unlikely that ethanol was responsible for the inflammation produced by ketorolac injection.

Analgesics↗
PubMed1997

Radiographic assessment of pedicle hook placement.

STUDY DESIGN: A cadaveric study of the changes in the radiographic morphology of the thoracic pedicle with vertebral rotation. OBJECTIVE: To study the effect of vertebral rotation on the assessment of pedicle hook placement by determining the radiographic anatomy of the pedicle and its relation to the pedicle hook. SUMMARY OF BACKGROUND DATA: It is commonly assumed that the oval pedicle shadow seen on spine radiographs is formed by the waist of the pedicle. The postoperative assessment of pedicle hook position is based on this assumption. METHODS: Thoracic cadaveric vertebrae between T5 and T8 were studied, with wire markers placed at the waist, the pedicle-facet junction, and the pedicle-body junction. Thoracic pedicle hooks were placed in the correct position and offset to one side. Radiographs of the vertebral body were taken from 0 degree to 30 degrees of rotation with reference to the sagittal plane. RESULTS: The radiographic morphology of the pedicle changes with vertebral rotation; it also differs between the concave and the convex side of a scoliotic spine. With rotation of less than 20 degrees, the pedicle shadow is formed by the waist on both sides. With 30 degrees of rotation, the concave pedicle shadow is formed by the pedicle-facet junction, whereas on the convex side, it is over-lapped by the transverse process shadow. A laterally misplaced hook on the convex side and a medially misplaced hook on the concave side can appear correctly located with vertebral rotation. CONCLUSION: The oval pedicle shadow is not simply represented by the waist of the pedicle. An understanding of the changes in radiographic morphology with rotation is necessary for the assessment of thoracic pedicle hook location after surgery.

Adult↗
PubMed1997

Characterization of a recombinant pea 5-aminolevulinic acid dehydratase and comparative inhibition studies with the Escherichia coli dehydratase.

Pea 5-aminolevulinic acid dehydratase (ALAD) was purified 200-fold from a recombinant overproducing strain of Escherichia coli, yielding an octameric enzyme with a specific activity of 280 units mg-1. Divalent metal ions were essential, Mg2+, Mn2+, and Co2+ ions all supporting activity, whereas Zn2+ ions could not. Equilibrium dialysis and atomic absorption studies revealed two Mg2+ ion binding sites per subunit. Pea ALAD bound the substrate 5-aminolevulinic acid covalently through a Schiff base at the P-site, electrospray mass spectrometry of the reduced enzyme-ALA Schiff base complex showing the presence of one P-site per subunit. The amino acid residue modified by ALA was identified by MALDI-MS and Edman sequencing as Lys-293, analogous to the active site Lys-247 of E. coli ALAD and Lys-252 of mammalian ALAD. Comparative studies of pea ALAD with E. coli ALAD using the inhibitors 3-acetyl-4-oxoheptane-1,7-dioic acid (AOHD) and succinylacetone (SA) indicated similar modes of inhibition, with the formation of a Schiff base complex between the inhibitors and the active site lysine. Studies with the ALA homolog, 4-amino-3-oxobutanoic acid (AOB), revealed that it is specific for the A-site of both the pea and E. coli ALADs. An interesting difference exists between the enzymes, however, pea ALAD being far more susceptible to inhibition with AOB than the E. coli enzyme. AOB bound 10 times better to the A-site of pea ALAD compared to the substrate, ALA. Despite the 2000 times lower Ki of AOB for pea ALAD, no abortive Schiff base intermediate, between enzyme-bound ALA at the P-site and AOB bound at the A-site, could be demonstrated.

Amino Acid Sequence↗
PubMed1997

Developing the interview protocol for video-recorded child sexual abuse investigations: a training experience with police officers, social workers, and clinical psychologists in Hong Kong.

A series of training programs which focused on culturally relevant questioning skills and video-recorded interviews in child sexual abuse cases were designed for social workers, police officers, and clinical psychologists in Hong Kong. An interview protocol was developed with four stages: rapport building, free narrative of account, questioning, and closure. The content analysis of 74 role-played interviews of video-recorded investigation revealed 119 questions and statements that were rated by these professionals and their instructor as helpful techniques in interviewing children suspected of having been sexually abused. Although each professional interviewed child victims with a unique style, they all found that maintaining a balanced perspective to play their roles in protecting the child, assessing the child, and collecting evidence was the most important aspect in an investigative process.

Child↗
PubMed1997

Prediction of correction of scoliosis with use of the fulcrum bending radiograph.

We used a new method to assess spinal flexibility in thirty patients who were to be managed operatively for adolescent idiopathic scoliosis. The method involves placing the patient in the lateral decubitus position and bent over a fulcrum (a radiolucent padded cylinder) so that the spine is passively hinged open. For thoracic curves the fulcrum is centered under the rib corresponding to the apex of the curve, and for lumbar curves the fulcrum is placed directly under the apex. The preoperative workup for the thirty patients included an anteroposterior radiograph made with the patient standing, a lateral-bending radiograph made with the patient supine, and the new fulcrum bending radiograph. All patients were treated with posterior spinal arthrodesis with segmental spinal instrumentation. The degree of flexibility obtained with the traditional and new methods was compared with the degree of correction observed on the radiograph made, with the patient standing, one week after the operation. Preoperatively, the mean Cobb angle was 58 degrees on the anteroposterior radiograph made with the patient standing, 31 degrees on the lateral-bending radiograph made with the patient supine, and 24 degrees on the fulcrum bending radiograph. The mean angle was 25 degrees on the anteroposterior radiograph made one week postoperatively, so the mean correction was 57 per cent. The difference between the mean angle on the lateral-bending radiograph and that on the postoperative radiograph was significant (p < 0.001); however, the mean angle measured on the preoperative fulcrum bending radiograph and the postoperative angle were almost identical. We found the fulcrum bending radiograph to be more predictive of the degree of flexibility and correctability than the lateral-bending radiograph in this group of patients who had segmental spinal instrumentation for correction of idiopathic scoliosis.

Adolescent↗
PubMed1995

Closed avulsion of both flexor tendons of the ring finger.

Closed avulsion of both flexor digitorum profundus and superficialis from the same finger is rare. Only ten cases have been described in the literature. The majority were treated with a two stage reconstruction of the flexor digitorum profundus. We describe a case in which primary repair of both tendons was performed.

Adult↗