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Biomedical subjects

S P Chow

Publications and source records attributed to S P Chow.

At least 19 recordsLinked to original sources
PubMed2006

Minimally invasive plate osteosynthesis in the treatment of proximal humeral fracture.

The management of fractures of the proximal shaft of the humerus has been evolving since the development of new techniques and new implants in recent years. It seems that this kind of fracture has an increasing incidence in the older, osteoporotic population. In the last 2 years, we have operated on 17 patients, with an average age of 65, who had proximal humeral shaft fractures treated by minimally invasive percutaneous osteosynthesis (MIPO) technique using the metaphyseal locking compression plate. Our study evaluated the surgical technique used and the outcome for these patients with regards to their range of movement and shoulder function. Our results showed that all the patients could achieve at least 140 masculine of shoulder abduction in the first 6 months after the operation, except for three patients who had shoulder impingement. These patients had an average Constant score of 76.8. All fractures had bony union at 6 months, except one, which was probably due to poor reduction in the initial operation. Another complication that we encountered was radial nerve neuropraxia. The ways to prevent these complications are discussed. In conclusion, MIPO fixation using the metaphyseal locking compression plate is a good option for the management of proximal humeral shaft fractures. It provides early functional recovery, but we had to pay special attention to some of the surgical details in order to minimise complications.

Adult↗
PubMed2006

Nano-structural bioactive gradient coating fabricated by computer controlled plasma-spraying technology.

The poor mechanical property of hydroxyapatite was the major problem for load bearing and implant coating in clinical applications. To overcome this weakness, a bioactive gradient coating with a special design composition of hydroxyapatite (HA), ZrO2, Ti, bioglass was developed. This 120 microm coating with an upper layer of 30-50 microm porous HA produced by computer controlled plasma spraying which maintained energy level of the plasma which ensure proper melting of powder. The crystal size of the coating was 18.6-26.2 nm. Transformation of t-ZrO2 to m-ZrO2 reduced the thermal stress that weakened the coating and lowered down interfacial strength of the coating and metal substrate. Thermal stress of sprayed coating was 16.4 MPa which was much smaller than the sample without thermal treatment of 67.1 MPa. Interfacial strength between the coating and metal substrate was 53 MPa which is much higher than conventional Hydroxyapatite coating. Based on XRD analysis crystallinity of HA approached 98%. Therefore, high temperature treatment improved long term stability of the coating through improved crystallinity of hydroxyapatite and reduced other impure calcium phosphate phase.

Aluminum Oxide↗
PubMed2006

Treating deep-seated mycobacterium marinum infection in the hand: a report of three cases.

We report three cases of an unusual aggressive type of Mycobacterium marinum infection of the hand which had been a nightmare both for us and the patient. These were the patients in which even after repeated thorough surgical debridement and appropriate (drug sensitive) medical treatment over a period had resulted in amputation or devastation of the soft tissues so extensively that almost only the neurovascular bundle, bone and the skin were the only structures left (cosmetic fingers - no function) at the last debridement after which the infection has not recurred. By presenting this article we want to stress on certain points pertaining to diagnosis, management, varied presentation and of course the dreadful complications of deep-seated M. marinum infection.

Adult↗
PubMed2006

Nicolau syndrome following intramuscular diclofenac administration: a case report.

Nicolau syndrome (livedoid dermatitis) is a rare adverse reaction of a still largely unidentified pathogenesis at the site of intramuscular drug injection. The typical presentation is pain around the injection site soon after injection, followed by erythema, livedoid patch, haemorrhagic patch, and finally necrosis of skin, subcutaneous fat, and muscle tissue. The phenomenon has been related to the administration of a variety of drugs, including non-steroidal anti-inflammatory drugs, corticosteroids, and penicillin. We report a case of Nicolau syndrome following an intramuscular injection of diclofenac. The large ulceration over the right buttock was positive for Pseudomonas aeruginosa, and histology revealed subcutaneous fat necrosis and non-specific inflammation with no evidence of malignancy or vasculitis. The lesion required multiple debridements and a partial-thickness skin graft. Subcutaneous injection, rather than intramuscular injection, was found to be a determining factor in this case. Clinicians must be cautious in the use of proper injection procedures, including appropriate needle length, in order to minimise complications.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Locking compression plate in the treatment of forearm fractures: a prospective study.

PURPOSE: To evaluate the use of locking compression plates (LCPs) in diaphyseal forearm fractures. METHODS: 9 women and 23 men (mean age, 35; range, 12-70 years) with 45 forearm fractures were treated by open reduction and internal fixation with 3.5-mm stainless steel LCPs. All patients were followed up monthly until union; the mean duration being 20 months. Radiographic assessment was performed at 3, 6, 12, and 18 months. Clinical assessments regarding pain and function were undertaken at the final follow-up. RESULTS: Two patients had delayed union but none had nonunion. There was no deep infection and only one superficial infection. Two refractures occurred after implant removal, both were of simple transverse type and at the sites of the original fractures. 33% of the fractures were reduced anatomically. 56% of the fractures healed with no or minimal callus formation and 44% with moderate callus formation. In total, 13% of the anatomically reduced fractures had moderate or abundant callus formation. 22 patients opted for removal of the implants (29 LCPs), after a mean of 16 (range, 9-21) months. CONCLUSION: The LCP is an effective bridging device used for treating comminuted fractures, but for treating simple fractures its superiority over conventional plating is yet to be proven.

Adolescent↗
PubMed2005

A novel artificial prosthetic replacement for the proximal interphalangeal joint of the hand--from concept to prototype.

This article describes the development of a proximal interphalangeal (PIP) joint prosthesis based on the principles of replicating anatomical surface components, the use of macrolocking intramedullary stem and the use of a cobalt-chrome alloy material. The design features are intended to obtain an optimal range of motion while retaining stability and longevity. The final prototype, for which a patent has been filed, is described.

Chromium Alloys↗
PubMed2003

Effect of torsion on microarterial anastomosis patency.

All kinds of technical faults must be prevented in microvascular anastomosis for successful reconstructive microsurgery. Torsion at the anastomosis site is one of the most basic technical errors. In this study, we investigate the effect of different degrees of microarterial torsion on patency and its physical changes on anastomosis in a rat model. A total of 144 microanastomosis were performed in 72 Sprague-Dawley rats. They were divided into 9 groups. The anastomosis was performed at 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, 315 degrees, and 360 degrees of torsion randomly. Patency rates and the narrowest point of the artery after the anastomosis were recorded after 1 hour for each group. In the second stage of the study, the 9 groups were divided into 2 groups for patency rates and histopathological sampling at the second and seventh days postoperatively. The femoral arteries in all groups were all patent at the end of 1 hour. Only 5 microanastomosis were thrombosed (one in the 45 degrees group, one in the 225 degrees group, one in the 270 degrees group, and two in the 315 degrees group) at the second day of exploration. Only two arteries were thrombosed (one in the 45 degrees group and one in the 315 degrees group) at the seventh day of exploration. The patency rate was 96.8% in experimental groups excluding the control group. Different degrees of torsion had no statistically significant effect on the patency rates of microvascular anastomosis. Torsional repair of the femoral artery in the rat has no significant histopathologic changes, but alternately, endothelial integrity was affected by excessive degrees of torsion. Different degrees of torsion at the anastomosis site do not affect patency rates and cross sectional histology of rat femoral arteries. In clinical practice, minor torsion can be tolerated, however, factors affecting patency such as tension, diameter disproportion, and tight closure can affect the final result of anastomosis. We observed that torsional force of the vessel is distributed along the artery to the weakest point.

Anastomosis, Surgical↗
PubMed2003

Effect of torsion on microvenous anastomotic patency in a rat model and early thrombolytic phenomenon.

Torsion at the microanastomosis site is a basic fault and should be avoided. In this study, we investigate the effects of different degrees of microvenous torsion on patency and its physical changes on anastomoses in a rat model. One hundred anastomoses were performed at different degrees of torsion, using femoral veins of Sprague-Dawley rats. Anastomoses were performed at 0 degrees, 45 degrees, 90 degrees, 135 degrees, and 180 degrees of torsion randomly. Patency tests immediately, 1 h, and 1 week after the anastomoses were checked, using the refill test. Measurements of external diameter were recorded at three points: one at the anastomosis site, and the others 2 mm proximal and distal to the anastomotic site. Finally, histopathologic and scanning electron microscopy studies were performed. Subsequently, because of the peculiar phenomenon of early recannulation of the thrombosed vessels, 20 vessels were also explored on the first and the third days postoperatively. The data demonstrate that torsion at 180 degrees, compared with 0 degrees, 45 degrees, and 90 degrees, impaired patency significantly (P < 0.005). In the subsequent study of 20 veins that were thrombosed on the first day, all became patent on the third day and remained so. In conclusion, rotation of a microvenous anastomosis begins to affect the patency rate at 90 degrees of torsion, and at 180 degrees has a patency rate of only 25%. However, all become patent again from the third day onwards. Thrombosis of rat femoral veins without chronic obstruction results in rapid lysis of thrombus and transient proliferative changes.

Anastomosis, Surgical↗
PubMed2003

Palmar plate fixation of AO type C2 fracture of distal radius using a locking compression plate--a biomechanical study in a cadaveric model.

The stability of palmar plate fixation using a locking compression T-plate was compared with that of a conventional palmar T-plate and a dorsal T-plate in a cadaveric model of an AO type C2 fracture of distal radius. The wrist axial load transmission through the radius was tested for each fixation. The results show that, under 100N axial load, the palmar locking compression T-plate restores stability comparable to that of the intact radius, and is superior to conventional palmar or dorsal T-plates.

Biomechanical Phenomena↗
PubMed2003

Biomechanical evaluation of plate osteosynthesis for AO type C2 fracture of the distal radius--a cadaver study.

An AO type C2 distal radius fracture was simulated in a cadaver model by creating a metaphyseal defect of 5 mm and an intra-articular defect of 2 mm. Five different methods of plate osteosynthesis were tested biomechanically in each of six fresh cadaveric hands. Biomechanical testing suggested that cement augmented plating plus screws in the distal fragment was the strongest. Dorsal and volar plating plus screws on both sides of the distal fragment had the same effect of restoring stiffness and load transmission pattern as fixation with double plating plus volar screws alone. Fixation with plating plus dorsal screws was significantly weaker than these three methods, and double buttress plating with no screws in the distal fragments was the weakest.

Analysis of Variance↗
PubMed2001

Experimental study of multiple level compression of the spinal cord in the rat.

A rat model study was performed to evaluate the effects of compression of the thoracic spinal cord. Dorsal screw compression of the thoracic spinal cord up to 50% canal diameter was created at T5 (Group A), T5 and T11 (Group B), and T5 and T8 (Group C). Clinical grading (Tarlov criteria), sensory evoked and motor evoked potentials, horse raddish peroxidase neural transport, and microangiography were studied. Single level compression had little effect. For double compression, there were marked detrimental effects both clinically and electrophysiologically, especially when the compression was close together. Neutral transport was affected in all groups, but the difference was not significant between them.

Journal Article↗
PubMed2001

Vascularized peripheral nerve trunk autografted in the spinal cord: a new experimental model in adult rats.

OBJECTIVE: To investigate the effect of vascularized peripheral nerve trunk autografted in spinal cord. METHODS: With modern microsurgical technique, vascularized peripheral median and ulnar nerve trunk autografted in the upper thoracic region of the spinal cord were established in 20 female adult rats. The origin and the termination of axons in the graft were studied by retrograde neuronal labeling with horseradish peroxidase (HRP). Cord, nerve grafts and some normal median an d ul nar nerves in the right upper limb were removed and sectioned for Bielschowsky's silver stain and haematoxylin and eosin (H&E) stain. Light and electron microscopic examination and electrophysiological examination were applied. RESULTS: The grafts were innervated by many new fibers. Studies with HRP indicated that new axons in graft were originated from intrinsic cent ral nervous system (CNS) neurons with their cell bodies from brain stem to s acral segments of spinal cord. Other axons arose from dorsal root ganglia at the level of graft and at least 19 distal segments to them. Together with electron microscopy, electrophysiological examination, silver and H&E stain, the results demonstrated that vascularized peripheral nerve trunk grafted in spinal cord attracted many neurons to grow into the nerve grafts. CONCLUSIONS: The findings implicate that CNS is able to regenerate much better in vascularized nerve autografted in spinal cord.

Animals↗
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↗
PubMed2000

Biomechanical properties of thin skin flap after basic fibroblast growth factor (bFGF) administration.

This study is designed to examine the effects of basic fibroblast growth factor (bFGF) administration on the biomechanical properties of thin skin flap healing. A total of 42 rats were used in this study, and skin flaps 10 cm long by 3 cm wide were raised in 28 rats. One injection of bFGF was applied at three different times (immediately postoperatively, and 24 h and 48 h postoperatively) between the flap and wound bed of 14 rats (the bFGF treated group), while the other 14 rats with flaps had the same tissue culture medium treatment but without bFGF (the untreated group). The remaining 14 rats without flaps constituted the control group (normal group). The rats were killed 10 days postoperatively, and 1. 0 cm x 6.0 cm sections of the skin flap taken for mechanical and histological testing. The load, deformation and tensile strength at failure were recorded. The average flap survival area in the bFGF treated group was 27 cm(2), significantly higher (P< 0.001) than that seen in the untreated group. The average elastic stiffness of the skin flap in the bFGF treated group was also observed to be higher than in the untreated group although this difference was not significant. The mean tensile strength of the bFGF treated group (61 N) was significantly higher than the untreated group (38 N, P< 0.01) however. Despite this, the tensile strengths at failure of both of these groups were found to be significantly lower than that of normal skin (101 N, P< 0.01). A relaxation in load of about 8% was seen in specimens from the normal group and the bFGF treated group, while the untreated group showed a relaxation of about 15%.

Animals↗