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Biomedical subjects

C K Cheng

Publications and source records attributed to C K Cheng.

At least 37 records · Page 2Linked to original sources
PubMed1998

Cementless Roy-Camille femoral component.

From 1984 to 1987, a complete, single-layered, porous-coated femoral component (Roy-Camille type) was used for primary cementless total hip replacement in 80 patients. Seventy-two patients (77 hips) with a minimal follow-up of 5 years (mean 7.2 years) were assessed clinically and radiographically. Thigh pain occurred in 4 hips. Osteolysis appeared in 5 hips. Cortical thinning around the femoral component was significant at the proximal and middle levels. In total, 6 femoral components failed, which led to reoperation due to aseptic loosening (4 hips) and septic loosening (2 hips). The hip rating score (modified d'Aubigne and Postel rating system) in the surviving hips progressed from 9.0 (range 6-10) preoperatively to 16.3 (range 12-18) points at the latest follow-up. From this study, we found that the complete, single-layered, porous-coated stem had a low loosening rate after 5 years. Bone ingrowth into the porous coating was found in most of the cases. A lower stress shielding effect in comparison with the complete, multi-layered, porous-coated prosthesis was also noted.

Adult↗
PubMed1998

Comparison of muscle strength of posterior cruciate-retained versus cruciate-sacrificed total knee arthroplasty.

One of the most controversial issues in total knee arthroplasty is whether to retain or sacrifice the posterior cruciate ligament (PCL). Investigators have used various methods to evaluate the influence of the PCL after total knee arthroplasty, but muscle strength evaluation has not been reported. The purpose of this study is to compare the long-term effects of PCL retention or sacrifice on muscle strength. Isokinetic testings and isometric testings were studied in patients with three different types of prosthesis design: total condylar, low contact stress rotating platform (both sacrifice PCL), and low contact stress meniscal bearing (retains PCL). The results showed that in all testing conditions, the hamstring to quadriceps ratios did not significantly differ among the three prosthetic designs (P > .05) even after long-term (6-13 years) functional adaptation.

Aged↗
PubMed1998

Influences of walking speed change on the lumbosacral joint force distribution.

To more understand the influence of the walking speed on the spinal joint force distribution, a three-dimensional biomechanical model was used to estimate the spine loads during human gait with three different walking speeds. This previously developed and validated model included a dynamic external model and an internal model with forces of disc, 8 major muscles, 2 ligaments and 2 facet joints at L5/S1 level. A linear optimization method was used to solve the internal model to estimate the L5/S1 spinal joint force distribution. The results of five young male subjects showed that the mean peak L5/S1 disc compressive forces on the slow, preferred and fast speeds were 2.28, 2.53, 2.95 body weight, respectively. The peak forces happened right after the heel strike and before completely toe off. The facet joint forces were generally increased with the walking speed increase, too. To reduce the loads on the spine, the slow walking is then recommended for the patients with low back pain or after spinal surgery.

Acceleration↗
PubMed1998

The first case of the p phenotype in a Gurkha Nepalese.

A serum sample from a Gurkha Nepalese soldier, residing in Hong Kong, was found to cause hemolysis of reagent ABO red cells (RBCs) in the reverse blood grouping test. Subsequent follow-up studies revealed that he was of the p phenotype, with potent anti-PP1Pk that was strongly hemolytic both at room temperature and 37 degrees C. The anti-PP1Pk was composed of IgG and IgM, and its various components were separable.

Journal Article↗
PubMed1998

Gain of muscle torque at low and high speed after isokinetic knee strengthening program in healthy young and older adults.

Low-speed isokinetic exercise has been recommended to exert a maximal contraction and produce greater muscle torque than high-speed exercise in young adults. The purpose of this study was to compare the effectiveness of low- and high-speed isokinetic exercise programs for increasing muscle torque in young and elderly people. Twenty healthy elderly and 20 young subjects participated. The elderly subjects were divided into two groups. One group performed high-speed (300 degrees/s) isokinetic exercise training three times a week for the dominant-side knee extensor and low-speed (60 degrees/s) exercise for the non-dominant side for 6 weeks. The other group was trained using the reverse exercise regime. The training program for the young subjects was the same as that for the elderly groups. All subjects had their knee extensor torque evaluated with an isokinetic test before and at 2-week intervals during the training program. For young and elderly groups, both high- and low-speed isokinetic exercise training increased extensor torque in low- and high-speed tests. For the young group, low-speed exercise effectively improved muscle torque at low and high speeds. The improvement in slow muscle torque was significantly greater than that in fast muscle torque. For the elderly subjects, high-speed isokinetic exercise produced the greatest muscle torque at high speed in the first 2 weeks of training, and demonstrated a sharp increase in muscle torque in the final 2 weeks. Low-speed exercise frequently caused knee stress and the inability of some elder subjects to continue the exercises with maximal effort. Our findings indicate that high-speed exercise may be more appropriate for the elderly, and low-speed exercise may be more appropriate for younger people.

Adult↗
PubMed1997

Change in protein kinase C activity on day 5 of decidualization in pseudopregnant rats.

The specific activities of protein kinase C (PKC) and protein tyrosine kinase (PTK) were determined in the decidualized uterine tissue of pseudopregnant rat on day 5 of decidualization. We found that the activity of the cytosolic PKC was significantly lower in decidualized uterine tissue as compared with that of the controlateral untreated uterine tissues (1.5 +/- 1.4 versus 57.5 +/- 4.1 pmol 32P/min/mg, P < 0.001), while the PKC activity in particulate fraction was not significantly different (124.8 +/- 14.5 versus 236.8 +/- 88.6 pmol 32P/min/mg) concerning protein concentration. The reduced expression of the cytosolic PKC activity was observed on all five individual rats. In contrast, the decidualized uterine tissue showed similar cytosolic PTK activity as compared with the controlateral untreated uterine tissues (20.1 +/- 3.0 versus 20.6 +/- 3.2 pmol 32P/min/mg protein), and similar in particulate PTK activity (42.5 +/- 9.0 versus 36.8 +/- 5.1 pmol 32P/min/g protein). These results indicate that cytosolic PKC activity may be involved in modulation of decidual growth.

Animals↗
PubMed1997

A cellular automata model of diffusion in aqueous systems.

A cellular automata model of a solute diffusing in water has been created and studied for the influential attributes. The results with this model are in agreement with experimental results; that is, that lipophilic solutes diffuse faster than do polar solutes. The model reveals that a solution composed of a relatively lipophilic solute permits a greater extent of diffusion of another solute. This observation is in agreement with the model showing a diffusion preference of a solute between two solutions made up of differing polarities. The solute diffuses farther into the lipophilic solution. A temperature-lipophilicity phase diagram shows the influence of these two attributes on the rate of diffusion. A model of diffusion through solutions containing stationary ingredients reveals a faster rate when the ingredient is lipophilic. We are led to a conclusion that the relative lipophilicity of solutes or stationary ingredients in a solution has a direct influence on the rates of diffusion of other solutes in their midst.

Diffusion↗
PubMed1997

The effect of electrode arrangement on spectral distance measures for discrimination of EMG signals.

The proper electrode placement in applying cepstral coefficients for electromyogram (EMG) signature discrimination was investigated. We measured EMG signals of different motions with two electrode arrangements simultaneously. Electrode pairs were located separately on dominant muscles (S-type arrangement) and closely in the region between muscles (C-type arrangement). The application of the cepstral method to signals derived from a C-type arrangement did not achieve the same discrimination as with a S-type arrangement. We used a simplified model to elucidate the poor performance in C-type signals. The bandwidth of signals obtained from S-type placement is wider than that from C-type. Narrower bandwidth decreases the importance of the more discriminative parts for both autoregressive (AR) and cepstral methods. The cepstral method is more sensitive to such variation, so the degradation in performance is more serious for the cepstral method. Second, the amplitude of C-type signal is lower than the S-type; therefore, the C-type signal is more sensitive to the disturbance of noise, especially in the high-frequency band. As high-frequency noise increases, the spectral difference between different EMG signals is gradually dominated by the low-frequency part, which is more informative. Thus, the performances of both methods are improved with increasing high-frequency noise. The improving rate of the AR method is faster than the cepstral method; therefore, its discriminative efficiency may exceed the cepstral method with C-type arrangement.

Adult↗
PubMed1997

The relation between standing balance and walking function in children with spastic diplegic cerebral palsy.

To establish and compare the relationship between standing balance and walking performance, eight children with spastic diplegic cerebral palsy (CP) and 16 non-disabled, age- and sex-matched children were studied. The results showed that the children with CP had worse static balance stability in various sensory environments and dynamic balance (rhythmic shifting ability) than the non-disabled children. Moreover, the children with CP walked at a slower speed but at a greater physiological cost than the non-disabled children. In the children with CP, dynamic balance significantly correlated with walking function. It is suggested that rhythmic weight-shift training should be encouraged to improve the walking performance of children with CP.

Adolescent↗
PubMed1997

A neuro-control system for the knee joint position control with quadriceps stimulation.

A neuro-control system was designed to control the knee joint to move in accordance with the desired trajectory of movement through stimulation of quadriceps muscle. This control system consisted of a neural controller and a fixed parameter proportional-integral-derivative (PID) feedback controller, which was designated as a neuro-PID controller. A multilayer feedforward time-delay neural network was used and trained as an inverse model of the functional electrical stimulation (FES)-induced quadriceps-lower leg system for direct feedforward control. The training signals for neural network learning were obtained from experimentation using a low-pass filtered random sequence to reveal the plant characteristics. The Nguyen-Widrow method was used to initialize the neural connection weights. The conjugate gradient descent algorithm was then used to modify these connection weights so as to minimize the errors between the desired outputs and the network outputs. The knee joint angle was controlled with only small deviations along the desired trajectory with the aid of the neural controller. In addition, the PID feedback controller was utilized to compensate for the residual tracking errors caused by disturbances and modeling errors. This control strategy was evaluated on one able-bodied and one paraplegic subject. The neuro-PID controller showed promise as a position controller of knee joint angle with quadriceps stimulation.

Adult↗
PubMed1997

Weight bearing influence on knee joint bony contact movements: an in vivo video-fluoroscopy study.

In order to understand the effects of body weight-bearing on knee joint bony contact movements, a video-fluoroscopic digitizing system with in vivo human knee extension-flexion motions of 12 healthy adults under body weight-bearing and non-weight-bearing conditions was studied. These 12 subjects were equally separated into two groups consisting of a body weight-bearing group and a non-weight-bearing group. Video-fluoroscopic images were digitized to get three parameters from the knee joint bony geometry. These three parameters were the radius of rotation, the are length of rotation, and the contact point of the tibiofemoral joint, and they were used to decide the knee joint bony contact status of the sliding, spinning and rocking motions. The results showed that the knee bony contact movements under body weight-bearing conditions had about 4 times the incidence rate of the sliding motion under non-weight-bearing conditions. The incidence rate of the sliding motion was greatest when the knee flexion was less than 30 degrees. The knee bony contact movements under non-weight-bearing conditions had a larger spinning motion incidence rate and smaller rocking motion incidence rate than they did under weight-bearing conditions. The larger spinning motion incidence rate when the knee joint flexion was greater than 60 degrees. In conclusion, the body weight-bearing factor should be considered in studying knee joint bony contact movements.

Adult↗
PubMed1996

The altered activity of membrane-bound protein kinase C in human liver cancer.

The activity of protein kinase C (PKC) in human liver cancer and adjacent normal liver tissue was determined. It was found that the activity of the membrane-bound PKC was significantly decreased in cancer tissue compared with that of the adjacent normal tissues (245.3 +/- 49.3 versus 396.9 +/- 82.4 pmol 32P/min per mg, P < 0.05); while the PKC activity in the cytosolic fraction was not significantly different (50.6 +/- 11.3 versus 40.0 +/- 6.6 pmol 32P/min per mg) concerning protein concentration. The reduced expression of membrane-bound PKC activity was observed at least in 8 of 9 patients. Moreover, the cancer tissue showed a significant decrease in total membranous PKC activity compared with the adjacent normal tissue of each patient (163.1 +/- 38.8 versus 433.8 +/- 92.4 pmol 32P/min per g tissue; P < 0.005) and no difference in total cytosolic PKC activity (285.9 +/- 58.8 versus 311.6 +/- 44.0 pmol 32P/min per g tissue). These results indicate that the progression of the human liver cancer might be associated with the decrease of membrane-bound PKC activity.

Adult↗
PubMed1996

A comparative analysis of various EMG pattern recognition methods.

Identification of motions of the neck and shoulders using the electromyographic (EMG) signal was investigated in this study. Three discrimination methods, the Euclidean distance measure (EDM), the weighted distance measure (WDM) and the modified maximum likelihood method (MMLM), were used to compare the conventional autoregressive (AR) and cepstral coefficients with closely positioned (C-type) and separately located (S-type) electrode arrangements. Surface electrodes were bilaterally located on and between the sternocleidomastoid and the upper trapezius muscles. The EMG signals obtained during 20 repetitions of 10 motions were analyzed for each subject. Results from nine subjects showed that the mean recognition rate of the cepstral coefficients was at least 5% better than that of the AR coefficients for the S-type signals, while the improvement was less obvious for the C-type signals. The MMLM obtained the best discrimination results of the three discrimination methods. The S-type signals achieved higher recognition rates than the C-type signals in most cases. Among the various combinations of feature sets, classifiers and electrode arrangements proposed in this study, the combination of the cepstral coefficients and the MMLM with the S-type arrangement achieved the best discrimination efficiency. The proper choice of five of 10 motions raised the recognition rate to more than 97%.

Adult↗
PubMed1996

Real-time implementation of electromyogram pattern recognition as a control command of man-machine interface.

The purpose of this study was to develop a real-time electromyogram (EMG) discrimination system to provide control commands for man-machine interface applications. A host computer with a plug-in data acquisition and processing board containing a TMS320 C31 floating-point digital signal processor was used to attain real-time EMG classification. Two-channel EMG signals were collected by two pairs of surface electrodes located bilaterally between the sternocleidomastoid and the upper trapezius. Five motions of the neck and shoulders were discriminated for each subject. The zero-crossing rate was employed to detect the onset of muscle contraction. The cepstral coefficients, derived from autoregressive coefficients and estimated by a recursive least square algorithm, were used as the recognition features. These features were then discriminated using a modified maximum likelihood distance classifier. The total response time of this EMG discrimination system was achieved about within 0.17 s. Four able bodied and two C5/6 quadriplegic subjects took part in the experiment, and achieved 95% mean recognition rate in discrimination between the five specific motions. The response time and the reliability of recognition indicate that this system has the potential to discriminate body motions for man-machine interface applications.

Case-Control Studies↗
PubMed1996

A cellular automata model of enzyme kinetics.

We have developed a cellular automata model of an enzyme reaction with a substrate in water. The model produces Michaelis-Menten kinetics with good Lineweaver-Burk plots. The variation in affinity parameters predicts that, in general, hydrophobic substrates are more reactive with enzymes, this attribute being more important than the relationship between enzyme and substrate. The ease of generation and the illustrative value of the model lead us to believe that cellular automata models have a useful role in the study of dynamic phenomena such as enzyme kinetics.

Automation↗
PubMed1996

Muscle strength after successful total knee replacement: a 6- to 13-year followup.

This study investigated the long term results of muscle strength of the knee joint after total knee replacement. Isokinetic testings of 120 degrees and 180 degrees per second and isometric testings at 30 degrees and 60 degrees knee flexion were studied on 1 healthy group and 3 groups of patients 6 to 13 years after total knee arthroplasty with prosthesis designs of total condylar, low contact stress meniscal bearing, or low contact stress rotating platform. The total condylar and low contact stress rotating platform prostheses were designed for use with a cut posterior cruciate ligament, whereas the low contact stress with meniscal bearing type was designed for use with a retained posterior cruciate ligament The muscle strength ratios of hamstring to quadriceps were compared among the prosthetic designs and there were no statistical differences among patient groups. Whether the posterior cruciate ligament was cut or retained did not affect the relative muscle strength of the quadriceps and hamstring. All hamstring to quadriceps ratios from the isokinetic testings of these 3 prostheses design groups were greater than those of the healthy group, but were quite close to those of patients with cut anterior cruciate ligaments or with lower levels of daily activity. The hamstring to quadriceps ratios after successful total knee replacement were not the same as those of the healthy group even after long term (6-13 years) functional adaptation.

Aged↗
PubMed1996

Intravitreal sustained release corticosteroid-5-fluoruracil conjugate in the treatment of experimental proliferative vitreoretinopathy.

PURPOSE: Proliferative vitreoretinopathy (PVR) remains the most common cause of failed retinal detachment (RD) surgery. The authors compared the effectiveness of two intraocular sustained-release codrugs in suppressing PVR in a rabbit model a surgically implantable pellet releasing 5-fluorouracil (FU) and dexamethasone (DX) for 1 week and an injectable intravitreal sustained-release suspension releasing 5-FU and triamcinolone acetonide for 1 month. METHODS: Sustained-release devices and suspensions were prepared to deliver equimolar quantities of corticosteroid and 5-FU. In group 1, devices were implanted surgically into the vitreous of the right eye of 10 New Zealand White rabbits. Ten control rabbits received surgical implantation of the suture only. In group 2, drug suspension was injected into the vitreous of the right eye of 10 New Zealand White rabbits. Ten control rabbits received injection of the vehicle only. One day later, each rabbit was injected intravitreally with 250,000 homologous rabbit dermal fibroblasts. Severity of PVR was graded clinically by two masked observers on days 3, 7, 10, 14, 21, and 28. RESULTS: In group 1, clinical severity of PVR was less in the experimental group than in the control group at all time points, this was only statistically significant on day 10 (P = 0.04). Six eyes developed moderate to severe tractional RD or bullous RD in the control group by day 10 compared with none in the experimental group (P = 0.01). In group 2, the median clinical grading of eyes in the experimental group was significantly less than that in the control group at all time points through day 21 (P < or = 0.01). CONCLUSIONS: Both the intravitreal sustained-release dexamethasone-5-FU device and the triamcinolone-5-FU suspension effectively inhibit the progression of PVR in a rabbit model. Simultaneous delivery of 5-FU and corticosteroid may target different components of the wound-healing process in this disease.

Animals↗