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Biomedical subjects

M K Wong

Publications and source records attributed to M K Wong.

At least 19 recordsLinked to original sources
PubMed2006

The use of computer navigation in performing minimally invasive surgery for intertrochanteric hip fractures--The experience in Singapore.

OBJECTIVE: Intertrochanteric hip fractures are very common and early mobilisation correlates with a better outcome. The ideal surgical procedure should protect the soft tissue envelope, thereby preserving blood supply and reducing blood loss. Furthermore, occupational exposure to fluoroscopy that is used in hip fracture fixation remains a concern amongst orthopaedic surgeons. Computer-aided surgery can help to reduce reliance on fluoroscopy. We therefore combined the principles of minimally invasive plate osteosynthesis (MIPO) and computer navigation to describe a new procedure. We also present our results using this technique of minimally invasive computer-navigated dynamic hip screw fixation (navMIS-DHS), and compare it to computer-navigated open DHS fixation (nav-DHS) and to conventional open DHS fixation (conv-DHS). MATERIALS AND METHODS: This paper has three parts. In the first part, we describe the procedure of navMIS-DHS in detail. In the second part, we present our initial retrospective pilot series of 35 cases. Amongst them we performed 5 navMIS-DHS, 3 nav-DHS and 27 conv-DHS. There were also two cases of conv-DHS deliberately performed with a mini-incision in an attempt to see if we could duplicate the 5 cm incision that we achieved with navMIS-DHS. All patients were followed up for a minimum of 6 months. In the third part, we performed a single surgeon prospective evaluation of navMIS-DHS versus conv-DHS involving 43 fractures in two arms. RESULTS: We were able to achieve reduction in fluoroscopy time. There was also reduction in opiate requirement post-operatively in the minimally invasive procedure. The incision sizes were also smaller. The prospective study also showed less wound-related complications in navMIS-DHS and a shorter time to ambulation. Implant positions were acceptable but we have also described how it may be improved. CONCLUSIONS: Navigated MIS-DHS, by virtue of less pain, better healing, earlier rehabilitation and potentially shorter hospital stay, would benefit both the patients and reduce the economic strain on the health care system. It is a safe and reproducible procedure. Technical difficulties are present and these need to be addressed with further modifications of technique, and instrumentation.

Aged↗
PubMed2006

Acute adverse reactions to magnetic resonance contrast media--gadolinium chelates.

The objective of this study was to evaluate the clinical safety of intravenous gadolinium-based contrast media used in patients who underwent MRI at a single institution. Acute adverse reactions to intravenous gadolinium-based contrast media used for MRI at the Princess Margaret Hospital, Hong Kong, SAR, from January 1999 to November 2004 were recorded in an incidence log book. The medical records of patients' demographics were retrospectively reviewed and the nature, frequency and severity of the adverse reactions were investigated and documented. The incidence of acute adverse reactions to intravenous gadolinium-based contrast media was 0.48% (45 patients with 46 adverse reactions). The severity of these adverse reactions were 96% mild, 2% moderate (one patient developed shortness of breath that required oxygen supplementation and intravenous steroidal management) and 2% severe (one patient developed an anaphylactoid reaction, but successfully recovered through timely resuscitation). No patients were recorded as having contrast extravasation and none died as a result of any adverse reaction. Among the 45 patients who developed adverse reactions, three patients (6.7%) had prior adverse reactions to iodinated contrast media, three (6.7%) had prior reactions to a different gadolinium-based contrast agent, one (2%) had asthma and nine (20%) had a history of drug/food allergy. Overall, 41% of the adverse reactions were not documented in the final MRI report or the clinical medical records. Gadolinium-based contrast media are safe and well tolerated by the vast majority of patients. In our study, the adverse reaction rate (0.48%) and the incidence of severe anaphylactoid reaction (0.01%) concur with those reported in the literature. Although most of the symptoms are mild and transient, these adverse reactions must be accurately documented and managed.

Acute Disease↗
PubMed2006

Recurrent pneumothorax in pregnancy: what should we do after placing an intercostal drain.

Recurrent pneumothorax is rare during pregnancy. We describe a Chinese woman, with a history of spontaneous pneumothorax managed with an intercostal drain, who developed a recurrent pneumothorax during her 32nd week of pregnancy. There is no consensus on management in this situation. We review the literature and discuss different management approaches. Thirty-six cases of antepartum pneumothorax have been reported in 31 case reports. An intercostal drain only (n=11) or surgeries (thoracotomy, n=9; or video-assisted thoracoscopy, n=2) were common treatment options with no surgical complications reported. Twenty-two (61%) patients progressed to a normal vaginal delivery, while the rest required forceps delivery (22%) or Caesarean section (14%). No single treatment option outweighed the others. There were no maternal or foetal complications reported in those who underwent antepartum surgical intervention. Surgical management of recurrent pneumothorax during pregnancy is well tolerated.

Adult↗
PubMed2004

Lymphoepithelioma-like carcinoma of the lung: experience with ten cases.

OBJECTIVE: Lymphoepithelioma-like carcinoma of the lung (LELC) is a rare form of non-small cell lung cancer predominantly affecting young non-smoking Asians, and there has been only limited experience in its palliative chemotherapy and radiotherapy. We investigated tumour response, time to progression and survival of LELC patients who received such treatment. DESIGN: We prospectively recruited patients with confirmed advanced LELC who were treated with chemoradiotherapy in our unit, a regional tertiary referral centre for lung cancer treatment. RESULTS: There were 10 patients (five males, age 47 +/- 9.8 years, median follow-up 22 months) with advanced LELC (respectively 1, 4, and 5 patients at TNM stage IIIA, IIIB and IV) who received systemic chemotherapy and radiotherapy. The primary chemotherapy regimen consisted of 5-fluorouracil/leucovorin/cisplatin. The response rates to 5-fluorouracil/leucovorin/cisplatin were 60% partial response, 10% stable disease, and 30% progressive disease. Eight patients were also given local radiotherapy. Five patients received salvage chemotherapy when disease progressed after primary chemotherapy. The overall median survival was 23.4 +/- 4.7 months. CONCLUSION: The encouraging response to combination chemotherapy with 5-fluorouracil/leucovorin/ cisplatin, although empirical, supports its use with radiotherapy in unresectable lymphoepithelioma-like carcinoma of the lung.

Adult↗
PubMed2002

Osteoporotic hip fractures in Singapore--costs and patient's outcome.

INTRODUCTION: Little data are available on costs and outcome associated with osteoporotic hip fractures in Singapore. MATERIALS AND METHODS: A retrospective study was carried out on 280 consecutive hip fractures in patients older than 60 years admitted over a 3-year period. RESULTS: The mean age of patients was 80 years. Sixty-eight per cent were female and 58% were intertrochanteric fractures. Two hundred and sixty-four patients (95%) were operated upon. The mean total hospitalisation period was 17 days. Seventy-six per cent were staying in their own homes prior to the hip fracture while 22% were admitted from nursing homes. After surgery, 63% of patients returned to their homes while 26% needed nursing home care. The index admission mortality rate was 5.7%. Mortality was 26% at 1 year. Of those alive at 1 year, ambulatory status was: 28% were walking without aids, 39% were walking with aids, 24% were wheelchair bound and 9% were bedridden. Poor ambulatory function at discharge was related to increased mortality at 1 year. The average cost incurred was S$7367. The average government subsidy amounted to 82%. Ninety-one per cent of patients were warded in subsidized beds. Breakdown of cost was as follows: hospital stay, 42.6%; surgery, 36.5%; ward treatment, fee 9%; laboratory and X-ray investigations, 4.4%; implant costs, 3.5%; drugs, 1.6% and rehabilitation, 1.1%. Multivariate analysis showed that the cost is significantly related to days spent awaiting surgery, preoperative sepsis, operative complications and cerebrovascular accidents. Young age, good American Society of Anesthetists (ASA) status and endoprosthesis replacement were factors that allowed for early ambulation and lower costs. CONCLUSION: The mortality rates and functional outcome are not very different from published studies in the West. More of our patients returned to their own homes after hospitalisation. Early surgery, close involvement of the medical social worker and intensive physiotherapy or provision of outpatient therapy facilities may help cut cost of treatment.

Activities of Daily Living↗
PubMed2001

Asymmetric epoxidation of olefins catalyzed by chiral iminium salts generated in situ from amines and aldehydes.

[reaction: see text] A new approach for catalytic asymmetric epoxidation of olefins was developed that utilized chiral iminium salts, generated in situ from chiral amines and aldehydes, as catalysts. Epoxidation reactions can be conducted with 20 mol % of amines and aldehydes. The enantioselectivity of epoxides can be up to 65%. This modular approach obviates the difficulties inherent in the preparation and isolation of unstable exocyclic iminium salts.

Journal Article↗
PubMed2001

Plasminogen activator inhibitor-1 regulates tumor growth and angiogenesis.

Elevated expression of plasminogen activator inhibitor-1 (PAI-1) in tumors is associated with a poor prognosis in many cancers. Reduced tumor growth and angiogenesis have also been reported in mice deficient in PAI-1. These results suggest that PAI-1 may be required for efficient angiogenesis and tumor growth. In the present study, we demonstrate that PAI-1 can both enhance and inhibit the growth of M21 human melanoma tumors in nude mice and that this appears to be due to PAI-1 regulation of angiogenesis. Quantitative analysis of angiogenesis in a Matrigel implant assay indicated that in PAI-1 null mice angiogenesis was reduced approximately 60% compared with wild-type mice, while in mice overexpressing PAI-1, angiogenesis was increased nearly 3-fold. Furthermore, addition of PAI-1 to implants in wild-type mice enhanced angiogenesis up to 3-fold at low concentrations but inhibited angiogenesis nearly completely at high concentrations. Together, these data demonstrate that PAI-1 is a potent regulator of angiogenesis and hence of tumor growth and suggest that understanding the mechanism of this activity may lead to the development of important new therapeutic agents for controlling pathologic angiogenesis.

Animals↗
PubMed2001

Kinetic resolution of acyclic secondary allylic silyl ethers catalyzed by chiral ketones.

Kinetic resolution of acyclic secondary allylic silyl ethers by chiral dioxiranes generated in situ from chiral ketones (R)-1 and (R)-2 and Oxone was investigated. An efficient and catalytic method has been developed for kinetic resolution of those substrates with a CCl(3), tert-butyl, or CF(3) group at the alpha-position. In particular, high selectivities (S up to 100) were observed for kinetic resolutions of racemic alpha-trichloromethyl allylic silyl ethers 7 and 9-15 catalyzed by ketones (R)-2. Both the recovered substrates and the resulting epoxides were obtained in high enantiomeric excess. On the basis of steric and electrostatic interactions between the chiral dioxiranes and the racemic substrates, a model was proposed to rationalize the enantioselectivities and diastereoselectivities in the chiral ketone-catalyzed kinetic resolution process.

Journal Article↗
PubMed2001

Soluble recombinant endostatin purified from Escherichia coli: antiangiogenic activity and antitumor effect.

Endostatin is a potent and specific antiangiogenic protein capable of inhibiting the growth of murine and xenotransplanted human tumors. Thus far, however, recombinant endostatin prepared from Escherichia coli is insoluble after purification and therefore inappropriate for clinical settings. A soluble form of endostatin is available from a yeast system with relatively low yield and high cost, which has made it difficult to produce endostatin in quantities sufficient for extensive clinical evaluation. In this study, we developed a protocol to generate soluble recombinant murine endostatin from E. coli at a yield of 150 mg/liter-culture and 99% purity. The in vivo antiangiogenic and antitumor activities of the soluble recombinant endostatin are equally as potent as those of the previously published insoluble form. A similar protocol may be used to produce soluble human endostatin.

Angiogenesis Inhibitors↗
PubMed2001

Temporal stride and force analysis of cane-assisted gait in people with hemiplegic stroke.

OBJECTIVE: To understand the underlying biomechanics of temporal stride and force in people with hemiplegic stroke during cane-assisted walking. DESIGN: Three forceplates, 6 cameras, and an instrumented cane were integrated to analyze the cane-assisted gait of people with hemiplegic stroke. Temporal-stride parameters, and peak vertical, anterior (propulsive), posterior (braking), and lateral shear forces, as well as propulsive-breaking impulses were analyzed. SETTING: Chang Gung Memorial Hospital, Medical Center, Taiwan. PARTICIPANTS: Twenty people with hemiplegic stroke. MAIN OUTCOME MEASURES: Temporal-stride and force parameters. RESULTS: All patients walked at a relatively slow speed, ranging from 4.2 to 35.8cm/s. The triple and double support occupied most of the gait cycle (GC), whereas the single support occupied only 10% of GC. The applied vertical, propulsive, braking, and lateral shear forces on either foot and the cane were 89.7% to 97.6%, 2.2% to 4.8%, 2.9% to 3.9%, and 5.5% to 6.7% body weight (BW), respectively. Patients applied less than 25% BW of peak vertical forces on the cane. They applied greater peak propulsive forces and impulses on the sound foot, while applying greater peak braking forces and impulses on the affected foot and cane. CONCLUSIONS: The cane provided support and a braking function for people with hemiplegic stroke. People with stroke walking with cane assistance rely mostly on the sound limb for propulsion, while using the affected limb and cane for braking. Data provided could be useful in assessing the nature of cane assistance and in planning therapeutic strategies for people with stroke.

Adult↗
PubMed2001

Tai Chi Chuan training to enhance microcirculatory function in healthy elderly men.

OBJECTIVE: To evaluate cutaneous microcirculatory function in geriatric Tai Chi Chuan (TCC) practitioners. DESIGN: Case-control study. SETTING: Community setting. PARTICIPANTS: Ten elderly male TCC practitioners (mean age, 69.9 +/- 1.5 yr) and 10 sedentary men with matched age and body size (mean age, 67.0 +/- 1.0 yr). INTERVENTION: The TCC group had practiced TCC for 11.2 +/- 3.4 years (mean +/- standard error of the mean), with an exercise frequency of 5.1 +/- 1.8 times weekly. Each session included 20 minutes of warm-up, 24 minutes of TCC practice, and 10 minutes of cool down. MAIN OUTCOME MEASURES: A graded exercise test with gas analysis was conducted on a bicycle ergometer for each subject. Skin blood flow (SkBF), cutaneous vascular conductance, and skin temperature were measured at rest and during exercise testing. Plasma nitric oxide metabolite was analyzed before and immediately after exercise. RESULTS: The TCC group had a 34% higher VO(2)peak than the control group; it also had a higher SkBF, cutaneous vascular conductance, and skin temperature than the control group at rest and during exercise; and it also had a higher level of plasma nitric oxide metabolite than the sedentary group at rest and after exercise. CONCLUSION: Older TCC practitioners had higher cutaneous microcirculatory function during exercise than did their sedentary counterparts. Moreover, this change may be partially mediated by enhancement of nitric oxide release.

Aged↗
PubMed2001

Laribacter hongkongensis gen. nov., sp. nov., a novel gram-negative bacterium isolated from a cirrhotic patient with bacteremia and empyema.

A bacterium was isolated from the blood and empyema of a cirrhotic patient. The cells were facultatively anaerobic, nonsporulating, gram-negative, seagull shaped or spiral rods. The bacterium grows on sheep blood agar as nonhemolytic, gray colonies 1 mm in diameter after 24 h of incubation at 37 degrees C in ambient air. Growth also occurs on MacConkey agar and at 25 and 42 degrees C but not at 4, 44, and 50 degrees C. The bacterium can grow in 1 or 2% but not 3, 4, or 5% NaCl. No enhancement of growth is observed with 5% CO(2). The organism is aflagellated and nonmotile at both 25 and 37 degrees C. It is oxidase, catalase, urease, and arginine dihydrolase positive, and it reduces nitrate. It does not ferment, oxidize, or assimilate any sugar tested. 16S rRNA gene sequencing showed that there are 91 base differences (6.2%), 112 base differences (7.7%), and 116 base differences (8.2%) between the bacterium and Microvirgula aerodenitrificans, Vogesella indigofera, and Chromobacterium species, respectively. The G+C content (mean and standard deviation) is 68.0% +/- 2.43%, and the genomic size is about 3 Mb. Based on phylogenetic affiliation, the bacterium belongs to the Neisseriaceae family of the beta-subclass of Proteobacteria. For these reasons, a new genus and species, Laribacter hongkongensis gen. nov., sp. nov., is proposed, for which HKU1 is the type strain. Further studies should be performed to ascertain the potential of this bacterium to become an emerging pathogen.

Bacteremia↗
PubMed2001

Heart rate responses and oxygen consumption during Tai Chi Chuan practice.

Tai Chi Chuan (TCC) is a popular Chinese conditioning exercise, however, its exercise intensity remains controversial. The objective of this study was to determine the exercise intensity of Yang TCC by measuring heart rate (HR) responses and oxygen consumption (VO2) during practice. Fifteen men aged 39.9 +/- 9.5 yrs (range 26-56 yrs) participated in this study. Subjects had practiced classical Yang TCC for 5.8 +/- 2.4 years. HR responses and VO2 were measured during practice of TCC by using a K4 telemetry system. Blood lactate was measured before and immediately after TCC practice. Additionally, breath-by-breath measurement of cardiorespiratory function and sequential determination of blood lactate were performed during the incremental exercise of leg cycling. Measurements obtained during the TCC practice and exercise testing were compared to determine the exercise intensity of TCC. While performing TCC, the mean HR of subjects was 140 +/- 10 bpm, and the mean VO2 was 21.4 +/- 1.5 mL x kg(-1) min(-1). Compared with the data of the exercise test, the HR during practice was 58% of the heart rate range. Meanwhile, the VO2 during TCC practice was 55% of the VO2peak. Additionally, the level of blood lactate immediately after TCC practice was 3.8 mM, which reflected the level of lactate during TCC, approximated the onset of blood lactate accumulation (OBLA). The results demonstrate that TCC is an exercise with moderate intensity, and is aerobic in nature.

Adult↗
PubMed2001

Effects of task goal and personal preference on seated reaching kinematics after stroke.

BACKGROUND AND PURPOSE: Current theories of motor control in rehabilitation focus on how the nervous system responds to many types of external and internal constraints to execute motor behavior to accomplish a task. However, the dynamic interplay between these 2 constraints remains unclear. This study examined the impact of some aspects of internal and external constraints on motor performance in persons with stroke. METHODS: Twenty-seven persons with stroke used the uninvolved arms to perform an upper-extremity reaching task under 4 experimental conditions, formed by the crossing of functional goals and personal preferences. For the higher level of a functional goal, subjects took a drink from a can of beverage. For the lower level of a functional goal, subjects brought the can to the mouth without drinking. The level of personal preferences was determined, by interview, by the degree of predilection for particular beverages. RESULTS: Significant and large effects of functional goals and personal preference were found in the variables of movement time and reaction time. However, the data trend of the 4 testing conditions varied according to presence of visuospatial neglect and side of lesion. CONCLUSIONS: Offering choices for the treatment activities and incorporating functional goals to therapeutic tasks might enhance response rate or movement efficiency, depending on the side of the lesion and presence of visuospatial neglect. The findings suggest that the consideration of the neglect phenomenon is a necessity when rehabilitative treatment planning incorporates constraint factors.

Aged↗
PubMed2001

Open reduction and temporary rigid internal fixation of Lisfranc fracture-dislocations.

AIM: To review the results of open reduction and temporary rigid screw fixation of Lisfranc fracture-dislocations performed in Singapore General Hospital (SGH) from 1996 to 1998. METHODS: A retrospective review of II cases of Lisfranc injuries treated with temporary rigid internal screw fixation with a minimum follow up of six months was carried out. Radiological assessment was made at follow up to ascertain the anatomical reduction achieved and complications such as post-traumatic arthritis. In addition, the patients were evaluated with a functional assessment with relation to pain, interference to usual activities and the time to resumption of work. RESULTS: Anatomical reduction was achieved in all cases. None of the cases showed loss of reduction at follow up after the temporary implants were removed. No longitudinal arch collapse or other deformities were seen. All the patients had good or excellent functional outcomes. CONCLUSIONS: Results of treatment of Lisfranc injuries are related to anatomical correction. Temporary screw fixation allows rigid internal fixation with stability to allow anatomical correction. Screws also maintain their stability longer, allowing ligamentous injuries the longer period necessary for healing. In conclusion, temporary rigid screw fixation of Lisfranc fracture maintains anatomical reduction and gives excellent functional outcomes for the patients.

Adolescent↗
PubMed2001

Body weight, serum uric acid and lipid profile one year after spinal cord injury.

BACKGROUND: Survey of the serum lipoprotein profile, uric acid levels and body weight in Chinese patients with spinal cord injury (SCI) one year after injury, and to report the data of patients with SCI at different levels. METHODS: Seventy-seven Chinese patients with SCI categorized into cervical SCI, thoracic SCI, and lumbar SCI groups were enrolled in the study. The serum uric acid and lipoprotein profiles of these patients were evaluated one year after injury. All of the data in those different groups of SCI patients were compared with normal levels. Body weight before and after injury were also evaluated. RESULTS: Serum uric acid was within normal limits in all three SCI groups. A similar lower in serum high density lipoprotein cholesterol (HDL-C) level was observed in all three groups of SCI patients. Higher serum levels were observed in total cholesterol (TC) in the lumbar SCI group, triglyceride and very low density lipoprotein cholesterol in the thoracic and lumbar SCI group, and TC/HDL-C ratio in all three SCI groups. Decrease of body weight were noted in cervical and thoracic SCI patients. CONCLUSION: Further long-term follow up was necessary to determine the serum lipid and body weight change in patients with SCI at different levels.

Adult↗
PubMed2000

Inhibition of angiogenesis in vivo by plasminogen activator inhibitor-1.

The process of angiogenesis is important in both normal and pathologic physiology. However, the mechanisms whereby factors such as basic fibroblast growth factor promote the formation of new blood vessels are not known. In the present study, we demonstrate that exogenously added plasminogen activator inhibitor-1 (PAI-1) at therapeutic concentrations is a potent inhibitor of basic fibroblast growth factor-induced angiogenesis in the chicken chorioallantoic membrane. By using specific PAI-1 mutants with either their vitronectin binding or proteinase inhibitor activities ablated, we show that the inhibition of angiogenesis appears to occur via two distinct but apparently overlapping pathways. The first is dependent on PAI-1 inhibition of proteinase activity, most likely chicken plasmin, while the second is independent of PAI-1's anti-proteinase activity and instead appears to act through PAI-1 binding to vitronectin. Together, these data suggest that PAI-1 may be an important factor regulating angiogenesis in vivo.

Allantois↗