Biomedical subjects

Kwok-Sui Leung

Publications and source records attributed to Kwok-Sui Leung.

9 recordsLinked to original sources

PubMed2006

Virtual reality techniques. Application to anatomic visualization and orthopaedics training.

Surgical training systems using virtual reality simulation techniques offer a cost-effective alternative to traditional training methods. In this sense, techniques for interactive visualization and virtual reality surgery have been one of the very important research areas. We describe various techniques we have used in developing a virtual reality system for anatomic visualization and training arthroscopic knee surgeons. Virtual models used in our systems are constructed from the Visible Human Project and Chinese Visible Human data sets. We present our various developments in segmentation, personal-computer-based real-time volume visualization, soft tissue deformation with topological change in real-time using finite element analysis, and soft tissue cutting with tactile feedback.

Arthroscopy↗

PubMed2006

Age-associated decrease of type IIA/B human skeletal muscle fibers.

Elderly individuals often fall because of poor muscle strength and reduced balancing ability related to muscle aging. However, it is unclear whether changes in muscle fiber types contribute to poor strength or imbalance. We studied age- associated changes in human skeletal muscle fibers using muscle biopsy specimens taken from 65 male and female Chinese patients aged 17-96 years. The muscle specimens were cryosectioned with alkaline triphosphatase staining at pH 4.4, followed by image analysis. We analyzed morphologic observations and performed quantitative analyses of the number, size, and area percentage of different types of skeletal muscle fibers and connective tissues. Types IIA and IIB muscle fibers decreased with age in the area percentage, fiber number percentage, and mean fiber area, whereas Type I fibers increased in area and number but not in size. Morphologically, Type II fibers appeared smaller and flatter. Our findings suggest deterioration in muscle quality and balancing coordination in elderly patients. We provide data to help determine treatments for reversing muscle fiber changes and reducing the number of falls and related fractures in patients.

Accidental Falls↗

PubMed2005

Delayed stimulatory effect of low-intensity shockwaves on human periosteal cells.

We investigated the effect of shockwaves on cells explanted from normal human periosteum to study the potential mechanisms of their responses and to determine suitable treatment settings. The cells were subjected to one shockwave treatment with systematic combinations of energy intensities (range, 0.05-0.5 mJ/mm) and number of shocks (range, 500-2000) whereas control cells received no treatment. The immediate effect on cell viability and the long-lasting effect on proliferation, viable cell number at Day 18, and mineralization at Day 35 were assessed. We observed an immediate dose-dependent destructive effect of shockwaves. Energy intensity and number of shocks contributed equally to viability. Total energy dose (intensity x number of shocks) was a better reference for determining the shockwave effect. We also found a long-term stimulatory effect on proliferation, viable cell number, and calcium deposition of human periosteal cells. At the same total energy dose, low-intensity shockwaves with more shocks (0.12 mJ/mm at 1250 shocks) were more favorable for enhancing cellular activities than high-intensity waves with fewer shocks (0.5 mJ/mm at 300 shocks). These findings document some of the biochemical changes of periosteal cells during shockwave treatments.

Cell Proliferation↗

PubMed2005

A primary falls prevention programme for older people in Hong Kong.

This study describes the development and implementation of a large-scale primary fall and fracture prevention programme in Hong Kong and its effect on increasing the awareness and knowledge of fall and fracture prevention among older people. The effect of promotion of community participation is also investigated in the implementation of this primary prevention programme. The programme includes educational seminars, a train-the-trainers programme and a staff training programme. The effect of the educational seminars is shown by the increase in the knowledge and awareness of fall and fracture prevention among these participants (p < 0.01), while that of the train-the-trainers programme and staff-training programme is confirmed by the continuous expansion and continuation of the fall and fracture prevention programme in the community. The experience from this primary prevention programme has given us direction for future implementation of a more comprehensive prevention programme in our community.

Accidental Falls↗

PubMed2004

Correlations of calcaneal QUS with pQCT measurements at distal tibia and non-weight-bearing distal radius.

Quantitative ultrasound (QUS) is used for prediction for risks of osteoporotic fractures at various skeletal sites, irrespective of weight-bearing or non-weight-bearing skeletons. In the current study, we investigated the correlation between calcaneal QUS measurements (BUA, VOS, and Soundness) and volumetric trabecular, cortical, and its integral bone mineral density (tBMD, cBMD, and iBMD) using peripheral quantitative computed tomography (pQCT) of the weight-bearing distal tibia and non-weight-bearing distal radius in 198 healthy Chinese women between 40 and 62 years of age. Results showed that BUA, VOS, and Soundness measured by calcaneal QUS were significantly correlated with tBMD, cBMD, and iBMD of both distal tibia and distal radius (r = 0.210-0.447; all P < 0.01). The correlation coefficients of all the individual parameters between calcaneus and distal tibia were correspondingly higher (r = 0.214-0.447; all P < 0.01) than that of distal radius (r = 0.210-0.368; all P < 0.01). QUS Soundness showed the highest correlation (r = 0.447; P < 0.01) with tBMD of distal tibia when comparing with all other parameters between these two measurement devices. Stronger "within-device" correlations (r = 0.640-0.764; all P < 0.01) were found in pQCT measurements between distal tibia and radius. In addition, the largest and significant age-related decline was found in tBMD of the distal radius measured by pQCT and Soundness of the QUS measurement in the postmenopausal group. In conclusion, heel QUS measurement demonstrated slightly better correlation with trabecular bone of the weight-bearing skeleton than that of the non-weight-bearing skeleton measured by pQCT.

Adult↗

PubMed2004

Complex tibial fracture outcomes following treatment with low-intensity pulsed ultrasound.

A clinical study was conducted to investigate the effect of low-intensity pulsed ultrasound (US) stimulation (LIPUS) on the healing of complex tibial fractures. Thirty complex tibial fractures were randomly assigned to the treatment with LIPUS (n = 16) or by a dummy machine (sham-exposed: n = 14). The fractures were immobilized by either internal or external fixations according to the clinical indications. LIPUS was given 20 min/day for 90 days. Fracture healing was monitored by clinical, radiological, densitometric and biochemical assessments. The LIPUS-treated group showed statistically significantly better healing, as demonstrated by all assessments. Complications were minimal in the LIPUS group. There were two cases of delayed union, with one in each group. There were two cases of infection in the control group. The delayed-union cases were subsequently treated by LIPUS and the infection cases were treated with standard protocol. Fracture healing in these patients was again treated by LIPUS.

Adult↗

PubMed2004

Effect of weightbearing on bone formation during distraction osteogenesis.

The effect of weightbearing on the bone formation during distraction osteogenesis was studied with 24 goats after standardized osteotomy and distraction. Twelve goats were allowed to bear weight immediately and 12 were not allowed to bear weight. With the pattern of weightbearing documented, the formation of bone was monitored with serial radiographs and the bone forming activity was studied with histologic examination and immunohistochemical study of transforming growth factor-beta 1 expression. The results of the study showed that the bone formation as depicted by radiologic assessment of callus width and mineralized tissue was significantly better in the weightbearing group. Histologic study showed more bone formation qualitatively and quantitatively in the weightbearing group. This study confirmed the beneficial effect of weightbearing activity during distraction osteogenesis. Distraction provides pulsed form stimulation by tension stress across the osteotomy site and initiates osteogenesis while the compression stress exerted by the weightbearing is continuous in daily activities and enhances new bone formation. The clinical practice of early weightbearing during distraction osteogenesis should be reinforced.

Animals↗

PubMed2004

Lack of efficacy of low-intensity pulsed ultrasound on prevention of postmenopausal bone loss evaluated at the distal radius in older Chinese women.

A within-subject, randomized, and prospective intervention trial was done to evaluate the potential effect of low-intensity pulsed ultrasound on prevention of postmenopausal bone loss. Twenty healthy postmenopausal women between the ages of 51-81 years met the inclusion criteria. The treatment hand was randomly selected, and the contralateral site served as a control. Integral and trabecular bone mineral density were measured using highly precise multilayer peripheral quantitative computed tomography at the bilateral distal radius at baseline, 3 months after daily low-intensity pulsed ultrasound treatment, and 3 months after discontinuing treatment. Results showed that the rate of bone change (trabecular bone mineral density and integral bone mineral density) did not significantly differ between the site treated with low-intensity pulsed ultrasound and the contralateral control at either followup. Also, during the followup, bone mineral density did not change significantly in the contralateral control site. This was the first prospective and randomized study to show that low-intensity pulsed ultrasound at the current regime did not have significant effects on intact bone for prevention of postmenopausal bone loss in the distal radii of older Chinese women.

Aged↗

PubMed2002

Sustained expression of transforming growth factor-beta1 by distraction during distraction osteogenesis.

Distraction osteogenesis is a well-established clinical treatment for limb length discrepancy and skeletal deformities. In our previous studies, we have shown that the tension at the distraction gap correlated with the plasma bone specific alkaline phosphatase activity during distraction. Transforming growth factor-beta1 (TGF-beta1) has been shown to have a regulatory role in alkaline phosphatase activity during fracture healing. This study is to investigate the expression of TGF-beta1 during distraction as a biological response to mechanically stimulated osteoblastic activity by immunohistochemistry. The expression of TGF-beta1 in the distraction callus was compared with that in the fracture callus. During the distraction phase, the osteoblasts and osteocytes expressed a high level of TGF-beta1. Moderate expression of TGF-beta1 was observed in fibroblast-like cells in the fibrous zone of the distraction callus. After the distraction stopped, the expression of TGF-beta1 in different cell types decreased. In fracture healing, the strong expression of TGF-beta1 declined after the first week. Our results showed that the mechanical force induced and sustained TGF-beta1 expression in osteoblasts and fibroblasts-like cells of the distraction callus. Transforming growth factor-beta1 may play a role in transducing mechanical stimulation to biological tissue during in distraction osteogenesis.

Animals↗