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Biomedical subjects

P Q Chen

Publications and source records attributed to P Q Chen.

At least 19 recordsLinked to original sources
PubMed2001

Stress analysis of the distal locking screws for femoral interlocking nailing.

In femoral locked nailing, the distal locking screws are vulnerable to mechanical failure. Biomechanical studies have shown that the stress on these screws is substantially affected by the fit of the nail in the medullary canal. In this study, a "closed form" mathematical model based on elastic beam-column theory was developed to investigate how the nail-cortical contact, which was simulated by a linear elastic foundation, affected the stress on the distal locking screws. Providing data for the model was a construct of a fractured femur with an intramedullary locked nail loaded by an eccentric vertical load. The stress on the locking screw was analyzed as a function of the distance from the fracture to the locking screw in the distal fragment under two situations: with and without nail-cortical contact in the distal fragment. With nail-cortical contact, the screw stress decreased as the length of nail-cortical contact and the distance between the distal locking screw and the fracture site increased, but this stress contrarily increased when the nail reached the femoral region at which the screw length increased. The screw stress was much higher without nail-cortical contact than with contact and continued to increase as the nail was inserted further. The mathematical model developed here can be a convenient means of rapid stress evaluation and parametric analysis for locked femoral nailing. It may be used to improve the design of interlocking nails and surgical technique.

Biomechanical Phenomena↗
PubMed2001

[Gene typing of merozoite surface protein 1 of Plasmodium falciparum isolates from Hainan Province].

OBJECTIVE: To identify the genotype of merozoite surface protein 1 (MSP1) of Plasmodium falciparum isolates from Hainan Province. METHODS: Nested PCR was applied to amplify the MSP1 of Blocks 2 and 3 Plasmodium falciparum isolates from Hainan Province. Two allelic family representative gene fragments were sequenced. RESULTS: From 36 out of 39 blood samples from Plasmodium falciparum patients, 44 gene fragments of blocks 2 and 3 of the MSP1 were amplified, of which the MAD20-type allele was dominant(75%). followed by K1-type allele. No RO33-type allele was found. The mixed infection rate of the two different allelic type was 19.4%. Sequence analysis showed that the sequences of MAD20- and K1-type isolates from Hainan Province were highly homologous to that of the MAD20 and K1 allelic prototypes. CONCLUSION: Two principal allelic types of MSP1 gene, MAD20- and K1-type, exist in malaria endemic areas in Hainan Province, the MAD20-type being the dominant.

Alleles↗
PubMed2000

The oxidative metabolism of circulating phagocytes in ankylosing spondylitis: determination by whole blood chemiluminescence.

OBJECTIVE: Superoxide anion radicals within the human body are regarded as a major cause of inflammation. However, their role in the pathogenesis of ankylosing spondylitis (AS) has not been well identified. This study aimed at investigating the relation between AS and the oxidative metabolism of phagocytes in whole blood. METHODS: 24 patients with classic AS were examined to determine their clinical status; complete blood count, erythrocyte sedimentation rate (ESR), and C reactive protein (CRP) were determined, and levels of the superoxide anion radicals in the patients with AS and 21 healthy subjects were assessed by the ultraweak chemiluminescence method. Subsequently, the relation between this disease and phagocytes was examined by using N-formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol-12-myristate-13-acetate (PMA) stimulants. RESULTS: In clinical assessments, patients with AS had abnormally raised serum CRP (>10 mg/l) and ESR (>15 mm/1st h) levels. In contrast with healthy subjects, patients with AS had significantly increased rates of superoxide anion radical production in their whole blood either in the resting state or with either fMLP or PMA stimulation. In addition, chemiluminescence maximum light intensity was significantly higher in patients with AS than in healthy subjects after fMLP or PMA stimulation. CONCLUSIONS: Our results suggest that the phagocytes of patients with AS are partly activated in the resting state, and are sensitive to fMLP or PMA stimulation. The priming of phagocytes in the bloodstream is likely to be a causative factor in the onset of AS.

Adult↗
PubMed2000

Effects of dihydroartemisinin on fine structure of erythrocytic stages of Plasmodium berghei ANKA strain.

AIM: The fine structural changes of Plasmodium berghei ANKA strain after treatment with the dihydroartemisinin (DATM) were observed. METHODS: DATM 180 mg.kg-1.d-1 was given ig to outbreed NIH mice infected with P. berghei ANKA strain. Blood samples were collected, embedded and examined by electron microscopy. RESULTS: In P. berghei ANKA strain, 1 h after drug administration, the parasites food vacuole membranes were destroyed, and the pigment grains showed some changes. The nucleus membrane, cytomembrane, and food vacuole membranes were stratified 2 h after administration. At the same time, swelling and separation of the outer and inner membrane or shrinking of the mitochondria were seen. Stripped nuclear and cytoplasm membrane were developed and vacuolizations were seen 4 h later. Eight hours after administration, a large number of parasite structures were destroyed except for a few parasite autophagic vacuoles. CONCLUSION: DATM was a fast-acting and effective antimalarial drug. Its primary target is the membrane system. No obvious resistant characteristics were found upto 24 generations after resistant induction test for 4 months.

Animals↗
PubMed1999

Oxidative injury induced by synthetic humic acid polymer and monomer in cultured rabbit articular chondrocytes.

Humic substance has been proposed as one of the causative factors of Kashin-Beck disease (KBD), an endemic osteoarthritic disorder with necrosis of chondrocytes widely prevalent in some regions of China. In order to exclude the complications of natural humic substance, here we prepared phenolic polymers of synthetic humic acid (SHA) by oxidation of phenolic monomer, the protocatechuic acid (PCA). The biological effects of SHA and PCA on primary culture of rabbit articular chondrocytes were investigated. We found that not only SHA but also PCA caused chondrocyte injury, as evidenced by the loss of cell viability measured with methylthiazol tetrazolium (MTT) assay and the increased release of intracellular lactate dehydrogenase (LDH). Both SHA and PCA could result in lipid peroxidation and glutathione (GSH) depletion in chondrocytes, indicating that oxidative stress may be involved in chondrocyte injury. Furthermore, a marked increase in intracellular calcium level ([Ca2+]i) occurred after chondrocytes treated with SHA or PCA. These results suggest that chondrocyte injury elicited by SHA or PCA may be mediated through the occurrence of oxidative stress and the disruption of intracellular Ca2+ homeostasis. Data also suggest that the monomeric phenolic acid may be considered one of the causative factors of KBD in addition to humic substance.

Animals↗
PubMed1999

Operative repair of symptomatic spondylolysis following a positive response to diagnostic pars injection.

From 1989 to 1996, 275 patients (245 male and 20 female) with back pain symptoms and spondylolysis of the lumbar spine were reviewed. All patients were evaluated by a protocol that included nonoperative treatment, bone scan, and pars injection. Only those whose symptoms failed nonoperative measures, showing negative bone scan and positive pars injection, were regarded as candidates for surgical management. Pars injection with Marcaine was done, and there were 93 cases with a positive response of reproducing symptoms and symptom relief. Patients then received autogenous bone grafting and internal fixation of the pars interarticularis defect. The internal fixation devices used included translaminar screws (AO 3.5 cancellous screw) for the most frequent level of L5, hook screws for levels above L4, and augmentation with wire for cases with concomitant spinal bifida occulta. The average age of the surgical group (85 male and 8 female) was 23 years (range: 19-35 years). After a follow-up averaging 30.4 months (range: 24-48 months), fusion results were 87%. Clinical results of 85 cases (91.3%) were excellent to good; 8 cases were fair; there were no poor cases. Direct repair of the pars defect by internal fixation and bone grafting was done to preserve involved motion segment and to prevent abnormal stresses at adjacent levels. These procedures seemed to be clinically effective.

Adolescent↗
PubMed1999

Dose findings of dihydroartemisinin in treatment of falciparum malaria.

Forty patients with uncomplicated P. falciparum malaria were respectively treated in an open randomized comparative study of dihydroartemisinin tablets given at total doses of 480 mg over 5 days and 640 mg over 7 days in a drug-resistant malaria endemic area in Hainan, China. The result showed that all patients were clinically cured. In 5-day and 7-day groups, the mean fever clearance times (FCT) were 26.1+/-10.2 and 21.1+/-11.8 hours respectively; the mean parasite clearance times (PCT) were 58.7+/-20.9 and 59.4+/-20.9 hours respectively, which showed no significant difference. 28-day follow-ups were accomplished on 39 and 37 cases respectively in two groups, the recrudescence rates were 20.5% (8/39) in 5-day group, while 2.7% (1/37) in 7-day group with significant difference (chi2=4.19, p<0.05). No clinical drug-related side effect was found in two groups during treatment.

Administration, Oral↗
PubMed1997

In vitro and in vivo mechanical evaluations of plasma-sprayed hydroxyapatite coatings on titanium implants: the effect of coating characteristics.

This study was undertaken to evaluate the effect of coating characteristics on the mechanical strengths of the plasma-sprayed HA-coated Ti-6Al-4V implant system both in vitro and in vivo. Two types of HA coatings (HACs) with quite different microstructures, concentrations of impurity-phases, and indices-of-crystallinity were used. In vitro testings were done by measuring the bonding-strength at the Ti-6Al-4V-HAC interface, with HACs that had and had not been immersed in a pH-buffered, serum-added simulated body fluid (SBF). The shear-strength at the HAC-bone interface was investigated in a canine transcortical femoral model after 12 and 24 weeks of implantation. The results showed a bonding degradation of approximately 32% or higher of the original strength after 4 weeks of immersion in SBF, and this predominantly depended on the constructed microstructure of the HACs. After the push-out measurements, it was demonstrated that the HACs with higher bonding-strength in vitro would correspondingly result in significantly higher shear-strength at each implant period in vivo. Nevertheless, there were no substantial histological variations between the two types of HACs evaluated. The most important point elucidated in this study was that, among coating characteristics, the microstructure was the key factor in influencing the mechanical stability of the HACs both in vitro and in vivo. As a consequence, a denser HAC was needed to ensure mechanical stability at both interfaces.

Adhesiveness↗
PubMed1997

Triple innominate osteotomy and rotational acetabular osteotomy in the treatment of congenital hip dysplasia.

Congenital hip dysplasia is a developmental disease which predisposes patients to osteoarthritis of the hip. We compare the results and complications of triple innominate osteotomy and rotational acetabular osteotomy in the treatment of this disease. Between 1984 and 1992, 27 patients with 30 dysplastic hips received reconstructive procedures at National Taiwan University Hospital. Fourteen patients (16 hips) with a median age of 18 years were treated by triple innominate osteotomy. Nine of 16 hips had concomitant femoral osteotomy. Another 13 patients (14 hips) with a median age of 24 years were treated by rotational acetabular osteotomy. We compared the radiologic and functional results, complications and satisfaction of the patients in these two groups. Patients who underwent rotational osteotomy showed more correction in roof obliquity than patients who had triple innominate osteotomy. The functional results when evaluated by Harris scores, were better in patients who had triple innominate osteotomy than rotational osteotomy. Complications included one resubluxation of the hip in each group as well as one perforation of the hip joint and one pin break and nonunion at the osteotomy site in the rotational osteotomy group. Patients who had triple innominate osteotomy were more satisfied with the results. With proper selection of patients and accurate performance of the procedure, both triple innominate osteotomy and rotational osteotomy may be used effectively for the treatment of congenital hip dysplasia. However, in our study, patients who underwent rotational osteotomy had better anatomic correction, while those who underwent triple innominate osteotomy had better functional results.

Acetabulum↗
PubMed1996

Management of rigid post-traumatic kyphosis.

STUDY DESIGN: Rigid post-traumatic kyphosis after fracture of the thoracolumbar and lumbar spine represents a failure of initial management of the injury. Kyphosis moves the center of gravity anterior. The kyphosis and instability may result in pain, deformity, and increased neurologic deficits. Management for symptomatic post-traumatic kyphosis always has presented a challenge to orthopedic surgeons. OBJECTIVES: To evaluate the surgical results of one stage posterior correction for rigid symptomatic post-traumatic kyphosis of the thoracolumbar and lumbar spine. SUMMARY OF BACKGROUND DATA: The management for post-traumatic kyphosis remains controversial. Anterior, posterior, or combined anterior and posterior procedures have been advocated by different authors and show various degrees of success. METHODS: One vertebra immediately above and below the level of the deformity was instrumented posteriorly by a transpedicular system (internal fixator AO). Posterior decompression was performed by excision of the spinal process and bilateral laminectomy. With the deformed vertebra through the pedicle, the vertebral body carefully is removed around the pedicle level, approximating a wedge shape. The extent to which the deformed vertebral body should be removed is determined by the attempted correction. Correction of the deformity is achieved by manipulation of the operating table and compression of the adjacent Schanz screws above and below the lesion. RESULTS: Thirteen patients with post-traumatic kyphosis with symptoms of fatigue and pain caused by slow progression of kyphotic deformities received posterior decompression, correction, and stabilization as a definitive treatment. The precorrection kyphosis ranged from 30-60 degrees, with a mean of 40 degrees +/- 10.8 degrees. After correction, kyphosis was reduced to an average of 1.5 degrees +/- 3.8 degrees, with a range from -5 degrees to 5 degrees. The average angle of correction was 38.8 degrees +/- 10.4 degrees, with a range from 25 degrees to 60 degrees. Significant difference was found between pre- and post-operative kyphosis measures (P < 0.001). The follow-up period for all patients was 2 years, and the average kyphosis angle measured at the moment was 3.8 degrees +/- 3 degrees with a range from -3 degrees to 8 degrees. Substantial overall improvement was achieved in the 13 patients. CONCLUSION: This method provides single-stage posterior decompression, correction, and stabilization on as definitive management for post traumatic kyphosis of the thoracolumbar and lumbar spine.

Adult↗
PubMed1996

Magnetic resonance imaging of vertebral compression fractures.

In this study, magnetic resonance imaging (MRI) was used to analyze the signal intensity and vascularity of compression fractures of vertebrae in 74 patients. The possibility of nonunion was assessed according to the specific image findings and clinical presentation. All patients had chronic back pain for more than 3 months and compression fractures of the vertebrae initially demonstrated by plain radiography. Pre-enhanced T1 and T2*-weighted images (*multiplaner gradient recall sequence) and postenhanced MRI were obtained. Images were divided into three categories according to the signal intensity of the fractured vertebrae such as hyperintensity (n = 35), hypointensity (n = 24) on T1-weighted image and necrotic type compression fractures of the vertebrae (n = 15). Of the 15 necrotic-type cases, 13 disclosed "fluid"-containing space at the collapsed vertebrae and two showed "air"-containing space at the vertebral body. We believe that these findings are pathognomonic signs of nonunion of the collapsed vertebrae. Surgical specimens were obtained from the four patients whose vertebrae showed necrosis and granulation tissue. After posterior spinal instrumentation, the collapsed vertebral body regained the height and presence of the open end-plate of the vertebra on postoperative lateral radiography. The superior capabilities of MRI offers useful criteria that make the diagnosis of nonunion in compression fractures of the spine possible. Thus, a space with "fluid" or "air" collection at the anterior aspect of a collapsed vertebra as well as strong enhancement with Gd-DTPA at the posterior aspect of the collapsed vertebra may be considered to be pathognomonic signs of nonunion of the fractured vertebra.

Aged↗
PubMed1995

The center of ground reaction force during lifting.

The center locations of the ground reaction force were estimated when subjects assumed upright and bending postures as well as when they lifted at low and high speeds. Ten subjects participated in this study and were instructed to assume two postures and to perform two liftings sequentially in a random order. The center locations of the ground reaction force were calculated using a Computerized Dyno Graphic system (INFOTRONIC). The center of the ground reaction force in the full bending posture had a more anterior location than it did in the upright standing posture. When measured during the lifting activity, the center of the ground reaction force shifted forward and then backward during the whole activity. The center location shifted to a more anterior location during high-speed lifting than it did during low-speed lifting.

Adult↗
PubMed1994

The infectivity of gametocytes of Plasmodium falciparum from patients treated with artemisinin.

Twenty-seven patients with gametocytes of Plasmodium falciparum (PF) were divided into groups A, B, and C. A daily dose of 1200 mg artemisinin was given for 5 days to group A, a state dose of 750 mg of mefloquine to group B and a single dose of 750 mg mefloquine combined with 45 mg primaquine to group C. After treatment, the gametocyte count was taken daily, and infectivity of the gametocytes to Anopheles dirus via membrane feeding was also studied. Results showed that in group A, the density of gametocyte and infectivity were significantly reduced on days 4, 7, 14 and 21 after treatment; In group B, the gametocytes were significantly reduced on days 7, 14 and 21 and infectivity was significantly cut down on days 14 and 21 after medication. In group C, gametocytes disappeared in 5 out of 9 patients with failure of infecting mosquitoes in all 9 patients on day 4 after treatment. These indicate that artemisinin can effectively influence the infectivity of gametocytes of PF. Artemisinin is much better in blocking the transmission of PF malaria than mefloquine.

Animals↗
PubMed1994

[The infectivity of gametocytes of Plasmodium falciparum from patients treated with artemisinine].

27 patients with gametocytes of P. falciparum were divided into groups A, B and C. 1,200 mg of artemisinine was given as a daily dose for 5 days to group A, 750 mg of mefloquine plus 45 mg of primaquine as a single dose to group C. After medication, gametocyte count was observed daily in addition to the infectivity of gametocytes of P. falciparum to Anopheles dirus. In group A, the density of gametocytes and the infectivity were significantly reduced on days 4, 7, 14 and 21 during the study. In group B, the density of gametocytes was significantly reduced on days 7, 14 and 21 and the infectivity was obviously lowered on days 14 and 21 after medication. In group C, gametocytes disappeared in 5 out of 9 patients with the failure of infection to mosquitoes on day 4 after treatment. This indicates that artemisinine can effectively influence the infectivity of gametocytes of P. falciparum. Artemisinine is superior to mefloquine in blocking the transmission of P. falciparum malaria.

Animals↗
PubMed1992

Experimental structural scoliosis in rabbits.

Structural scoliosis was produced by purely posterolateral mechanical tethering of the spine with ligation of the scapula to the opposite pelvic bone in rabbits during the growing period. It is a simple and easy method without direct trauma to the spine. When the tethering force occurred discontinuously or only in the coronal plane by drawing of the scapula to the ipsilateral pelvic bone in 17 rabbits, spinal deformity could not be produced. The model provided evidence of biplanar deformity as one of the initial factors for the development of structural scoliosis.

Animals↗
PubMed1991

Gait analysis after total knee replacement for degenerative arthritis.

Using quantitative gait analysis and clinical evaluation, the functional results of 18 total knee replacement (TKR) in 13 patients who had osteoarthritis were evaluated. Nine knees each were replaced by Insall-Burnstein (I/B) posterior stabilized design or Miller-Galante (M/G) prosthesis. The former was fixed by cement and needed to sacrifice posterior cruciate ligament (PCL), while the latter was inserted without cement, and PCL could be reserved. The follow-up period ranged from 21 to 77 months. At the final follow-up, the overall functional knee score was 94.1 points (I/B 95.0 versus M/G 92.2). The average active knee flexion was 109.7 degrees (I/B 116.4 degrees versus M/G 102.9). For gait analysis, three cameras synchronized with 2 AMTI force plates were connected to the VICON system to provide kinetic and kinematic data during level walking. The data were compared with the non-operated side; and with younger subjects as normal control. They were supposed to possess normal knee functions. In patients after knee prosthesis, they tended to have slower velocity, shorter step length and less cadence. They also showed shorter swing and longer stance phases. In the M/G knee ground, the duration for double-limb support was longer, but shorter for single-limb support. The angles of knee flexion-extension of both prosthetic groups became narrower. Their ground reaction forces in both vertical and medio-lateral directions were larger than in the control groups, probably due to quadriceps dysfunction and subtle imbalance of the soft tissue-prosthesis complex around the joint.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Plate fixation for anterior cervical interbody fusion.

From April 1989 to April 1990, 13 patients with cervical spinal fracture/dislocation, spondylosis or metastasis were treated at the respective hospitals. There were 4 women and 9 men whose ages ranged from 25 to 70 years (mean 45 years). All of them were treated with neural decompression, bone grafting and anterior spinal interbody fusion. All iliac crest or fibular bone grafts were anchored to the vertebral bodies with plates and screws. The clinical outcomes were evaluated retrospectively. The results showed that all had improvement of neurological symptoms and signs. The radiographic evaluation revealed satisfactory alignment and sound union of the cervical spine in all 13 patients. No serious complications were found except screw loosening in two instances without impairment of clinical results. We concluded that anterior cervical plates provide effective stabilization which is essential for good results. Furthermore, from this study and a review of the literature, we advocated that it was not necessary for the tip of the screws to reach or even penetrate the posterior cortex of the vertebral body.

Adult↗