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Biomedical subjects

A Nather

Publications and source records attributed to A Nather.

At least 19 recordsLinked to original sources
PubMed2006

Mechanical properties of articular cartilage covered by the meniscus.

OBJECTIVE: To investigate the mechanical properties and morphological characteristics of articular cartilage on the tibial plateau of human knees, including the region covered by the meniscus. DESIGN: Using a 1-mm diameter flat-ended cylindrical probe to apply a constant load (0.6 MPa) at specific sites on the tibial plateau, the mechanical properties of articular cartilage were studied using seven cadaver knees. Comparison was made between data obtained by the cartilage covered by the meniscus and that not covered. This was done for both the medial and lateral plateaus. Histological sections of the articular cartilage were also performed to study differences between cartilage from these regions of the tibial plateau. RESULTS: Compared to cartilage that was not covered by the meniscus, the articular cartilage beneath the meniscus showed a significantly (P<0.05) larger modulus by as much as 70%, and was less thick by about 40%. Also, the subchondral bone quantity and calcified layer thickness were observed to be significantly lesser in the regions covered by the meniscus. CONCLUSIONS: Our findings revealed a significant difference between the mechanical properties and associated structures of articular cartilage in the region covered by the meniscus compared with the articular cartilage not covered by the meniscus.

Aged↗
PubMed2005

Pyogenic vertebral osteomyelitis: a review of 14 cases.

PURPOSE: To review and evaluate the management of 14 patients with pyogenic vertebral osteomyelitis at National University Hospital, Singapore between 1998 and 2001. METHODS: Demographic pattern, predisposing factors, clinical presentation, co-morbidities, microbiology, treatment, and complications of 14 patients were retrospectively reviewed. RESULTS: The mean age at presentation was 62.5 years and the male to female ratio was 6:1. The mean follow-up duration was 12.5 months. The most common predisposing condition was diabetes mellitus (n=5). The most common site of infection was the lumbar spine (n=8), followed by the thoracic (n=4) and cervical (n=2) spine. Staphylococcus aureus was the most common causative organism isolated (n=9), followed by methicillin-resistant S aureus (n=3), Pseudomonas pseudomallei (n=1), and Streptococcus agalactiae (n=1). 12 patients were treated surgically: 8 by an anterior approach, 3 by a posterior approach, and one by a combination of the 2. The mean period of antibiotic use was 11.4 weeks. One patient with melioidosis involving the T9 to T11 vertebrae caused by P pseudomallei died of empyema and septicaemia 22 months after presentation. CONCLUSION: Pyogenic vertebral osteomyelitis is not uncommon in the elderly, especially those with predisposing conditions such as diabetes mellitus. Computed tomography-guided needle biopsy is recommended to investigate causative microorganisms. Aggressive surgical debridement and prolonged antibiotic therapy were necessary in patients with methicillin-resistant S aureus, P pseudomallei, and S agalactiae.

Adult↗
PubMed2004

Biomechanical strength of deep-frozen versus lyophilized large cortical allografts.

OBJECTIVE: To compare biomechanical strength of deep-frozen versus lyophilized large cortical allografts. DESIGN: In vivo transplantation studies performed in tibia of adult cats using 4 cm deep-frozen and lyophilized, gamma-irradiated allografts to bridge large cortical defect model. BACKGROUND: Bridging large cortical bone defect is a challenging problem. Options include autografts, allografts, bioceramics and prostheses. Allografts provide a suitable option. METHODS: Forty mature cats were used. A large defect (4 cm) was created in mid-diaphysis of right tibia. In 16 cats, cortical defect was reconstructed using deep-frozen allografts (-80 degrees C) with intra-medullary rodding. In another 16 cats, lyophilized, gamma-irradiated allografts were used. Observation periods include 8, 12, 16 and 24 weeks. The specimens were procured together with unoperated legs as controls. Mechanical testing was performed using a materials testing machine with torsion test device of up to 500 Nm at speed of 0.18 rpm. Parameters studied included maximum torque, torsional stiffness and energy of absorption. RESULTS: Deep-frozen allografts did not reach 100% strength, achieving only 64% at 6 months. In marked contrast, lyophilized allografts were significantly weaker with only 12% maximum torque strength at 6 months. Lyophilized allografts were significantly weaker than deep-frozen allografts in all observation periods (p < 0.05). CONCLUSION: Deep-frozen allografts did not reach 100% normal strength and were significantly weaker than non-vascularised autografts. Lyophilized allografts were significantly weaker than deep-frozen allografts. RELEVANCE: For the reconstruction of massive cortical bone defects, only deep-frozen cortical allografts should be used. Lyophilized allografts are not suitable.

Animals↗
PubMed2004

Musculoskeletal tissue banking in Singapore: 15 years of experience (1988-2003).

PURPOSE: To report 15 years' experience of musculoskeletal tissue banking by the National University Hospital Tissue Bank. METHODS: This study describes the development of Singapore's national bone bank since its establishment in 1988. The bone bank's protocol follows guidelines recommended by the American Association of Tissue Banks and the European Association of Tissue Banks using strict donor selection criteria. Informed consent is obtained from all potential donors for tissue procurement and laboratory tests. Detailed medical history, thorough clinical examination, and chart review is performed for consenting donors. Suitable donors are subjected to tests for hepatitis B, hepatitis C, syphilis, and culture/sensitivity test of tissue for aerobic and anaerobic organisms. For living donors, repeat testing for AIDS and hepatitis C is performed at least 180 days after procurement. Tissue procurement is performed under sterile conditions. Small tissues are procured using the 'sterile double jar technique' and long bones using the 'sterile triple wrap technique', both developed by the author. Deep-frozen bones are gamma irradiated at 25 kilograys. Morsellised bones are lyophilised and gamma irradiated. Meticulous preparation for grafts is performed during transplantation. Antibiotic prophylaxis is used for 2 weeks. RESULTS: The bank maintains a good quality control. In January 2003, it was accredited ISO 9001 status. Up to June 2003, it has procured 440 bones from 440 living donors and 1055 allografts from 63 deceased donors. 854 musculoskeletal transplantations have been performed using tissues processed by the bank. Complication rate encountered was only 2.2%. CONCLUSION: The tissue bank provides high-quality allografts for safe tissue transplantations.

Bone Transplantation↗
PubMed2003

IAEA/NUS Distance Learning Diploma Training Course for Tissue Bank Operators - Past, Present and Future.

National University Hospital (NUH) Tissue Bank as the Regional Training Centre for Asia Pacific Region provided National University of Singapore (NUS) Diploma Course in Tissue Banking - a long distance diploma course since 1997. To date, five batches have participated - 94 tissue bank operators. Sixty-three tissue bank operators have convocated with NUS Diploma in Tissue Banking.From Regional Co-operative Agreement (RCA) Project, RAS 7/008 technology transfer was effected to Latin America and to Africa.A Memorandum of Understanding has been signed between International Atomic Energy Agency (IAEA) and NUS in July 2002 making Singapore the International Training Centre. An Internet NUS Diploma Course in Tissue Banking has been developed by IAEA and NUS. The first on-line diploma course will be launched in 2003.

Journal Article↗
PubMed2002

A study of non-closure of the peritoneum at vaginal hysterectomy.

The aim of this case-controlled study was to determine whether non-closure of the peritoneum is detrimental in vaginal hysterectomy. 233 patients who underwent total vaginal hysterectomy (TVH) or laparoscopically assisted vaginal hysterectomy (LAVH) at the University of Vienna/Austria were analyzed. Cohorts of patients were formed according to their peritonealization status (open, n=117, vs closed peritoneum, n=116) and further stratified according to the type of surgical procedure: simple TVH ( n=115), TVH with concurrent vaginal repair and/or urinary incontinence surgery ( n=91) and LAVH ( n=27). No significant differences could be observed in analyzed surgical outcome (operation time, blood loss and analgesia). Complications (fever, infection, hemorrhage or revision) were similar whether the peritoneum was closed or not. After simple TVH, resumption of bowel function took place earlier in patients with open peritoneum than in those where it had been sutured (1.9 vs 2.4 days, P=0.001). No readmission for prolapse of the vaginal vault was recorded. Non-closure of the peritoneum at vaginal hysterectomy appears to be safe. Omission of peritoneal closure reduces the potential risk of injury and has a beneficial effect on bowel function.

Austria↗
PubMed2002

Continuous vs interrupted sutures for single-layer closure of uterine incision at cesarean section.

In a non-randomized cohort study, we compared continuous with interrupted sutures for the closure of the lower uterine segment at cesarean section. Eighty-two women, who underwent cesarean section at the Department of Obstetrics at the University Hospital of Vienna between January and May 2000, were included in the study. Thirty-eight patients had single-layer closure of the lower uterine segment and 43 patients had closure with interrupted sutures. There were significant differences in total operating-time (32 min vs 40 min, P=0.001) and in the pre- and postoperative maternal hemoglobin (DeltaHb 0.6 g/dl vs 1.1 g/dl, P<0.01), but there was no significant difference in sonographically diagnosed hematomas (32% vs 21%, P=0.27). No woman had fever, the median hospitalization time was 6 days, and there were no re-admissions. In both groups, the median need for analgesics was 150 mg diclofenac ( P=0.22). Continuous single-layer closure of the lower uterine segment at cesarean section saves operating time, reduces blood loss, and introduces less foreign material into the wound.

Adult↗
PubMed2002

A case report of neurologically unstable fracture of the lumbosacral spine in a patient with ankylosing spondylitis.

INTRODUCTION: Fracture/dislocation is uncommonly reported in ankylosing spondylitis involving the lumbosacral spine. CLINICAL PICTURE: We report an 18-month follow-up of a case of neurologically unstable traumatic fracture of the lumbosacral spine in ankylosing spondylitis. TREATMENT/OUTCOME: Posterior decompression, alar-transverse fusion and instrumentation were performed. Anterior diskectomy and fusion were done 6 weeks later. There was solid bony fusion on follow-up and the patient had improvement of 2 Frankel grades and was able to ambulate. CONCLUSION: Combined approaches and longer fixations to stabilise the spine may be required. In the lumbosacral spine, this poses a problem vis-à-vis limited levels of fixation in the sacrum.

Accidental Falls↗
PubMed2001

[Non-closure of peritoneum at cesarean section. Results from repeat cesarean sections].

OBJECTIVES: A number of publications advocate the short-term advantages of peritoneal nonclosure at cesarean section. However, currently there are no hard data available about long-term results and the repeat cesareans. MATERIAL AND METHODS: The study group of this retrospective analysis consisted of 30 women who underwent a repeat cesarean delivery, after a previous cesarean without closure of the visceral and parietal peritoneum. The control group (n = 31) had undergone peritoneal closure at the primary operation. All cesareans were performed at the same institution between 04/01/1997 and 12/31/1998 (first operation), and 01/01/1999 and 06/30/2000 (repeat operation). RESULTS: The mean operation time was 38.9 (+/- 11.6) minutes in the study group and 44.2 (+/- 13.6) minutes in controls (p = 0.05). The mean incision-delivery time was 6.7 (+/- 3.2) minutes in the study group and 9.1 (+/- 3.9) minutes in controls (p < 0.01). No difference in intraoperative blood loss was observed between the two groups. In each cohort one case with significant intraabdominal adhesions was observed. CONCLUSION: Our results indicate that nonclosure of the peritoneum at primary cesarean section does not promote intraabdominal adhesions. This appears to be beneficial for the repeat cesareans.

Abdomen↗
PubMed2001

Biological Healing of Large Diaphyseal Deep-frozen Allograft Transplants.

The biological healing of large, deep-frozen, diaphyseal allografts was studied in 24 cats. Deep-frozen allograft stored at -80 degrees C was used to replace a large defect, at least two-thirds of the cat's tibial diaphysis. Intra-medullary rod fixation was used. The healing was studied at observation periods of 4, 6, 8, 12, 16, 24 and 36 weeks. Biological parameters studied included microangiography for revascularisation and fracture healing, bone resorption, new bone formation and callus encasement. Deep-frozen allografts united without difficulty by 12 weeks. However, minimal revascularisation of the allograft occurred even at 9 months. Likewise, minimal biological repair activity was seen even at 9 months as shown by the parameters of bone resorption, cortical new bone formation and 'callus encasement'. Biologically, deep-frozen cortical allografts remained inert for a long period of time in the adult cat.

Journal Article↗
PubMed2000

Biomechanical Strength of Large Diaphyseal Deep-frozen Allografts.

The aim of this paper is to study the biomechanical strength of deep-frozen allografts as they heal. Twenty-eight adult cats were used with the tibia as the experimental model site. Deep-frozen allografts stored at -80 degrees C were used to reconstruct a large tibial defect (at least two-thirds of the diaphysis). An intra-medullary rod was used for fixation. The healing was studied by X-ray at observation periods of 4, 6, 8, 12, 16, 24 and 36 weeks. Post-transplantation biomechanical testing was performed using the Shimadzu Universal Testing Machine DCS series with a torsion test device of 50 kg force metre. Parameters studied included maximum torque, torsional stiffness and energy of absorption. The transplanted grafts were compared to the mechanical properties of the internal controls of the normal opposite tibia of each cat. The results of the mechanical tests demonstrated that deep-frozen allografts did not regain normal strength. At nine months, only about 60% of normal torque strength and about 80% of normal torsional stiffness was achieved. Clinically, it is important to employ strong and rigid internal fixation using intra-medullary nailing rather than plating to allow for immediate mobilisation and reduce the rate of graft fracture.

Journal Article↗
PubMed2000

Peripheral quantitative CT of the forearm: scanner cross-calibration using patient data.

Bone density measurements by peripheral quantitative CT (pQCT) of the distal radius in 87 women (age 38.4 +/- 12.3 years) were obtained on a both a Stratec XCT 900 and an updated version XCT 1400. Axial area, and total and trabecular bone mineral density (BMD) results from both scanners were compared for all patients using linear regression analysis. To achieve scanner calibration we used the intercept and slope of the patients' correlations. The correlations of the patients' values were good for area (r = 0.83) as well as total BMD (r = 0.90) and excellent for trabecular BMD (r = 0.97). The cross-calibration approach in our study provided compatibility of pQCT for trabecular and total ROIs, the clinically mostly utilized volumes of measurement.

Adult↗
PubMed1999

Use of allografts in spinal surgery.

This is a review of 118 patients operated between January 1989 and February 1999, 78 for posterior fusions and 40 for anterior spinal reconstructions. For posterior fusion, meticulous preparation of the fusion bed was essential. The author strongly advocated using autografts from spinous processes for achieving facet joint fusion. Deep frozen allografts were used as a 50% allograft-autograft mixture. Good results were achieved -- no infection in all cases and implant failure with clinical non-union in only 5 cases. Massive anterior spinal reconstruction following corpectomy was performed in 34 cases. Allografts used included 15 femoral cortical rings, 11 tibial rings and 3 humeral cortical rings. The author advocated the use of an allograft-autograft composite by packing the medullary canal of the allograft with autografts. Deep-frozen cortical rings have been used (25 cases). Recently, more freeze-dried cortical rings made available were used (9 cases). The results of massive reconstructions were good. There was no infection and no implant failure in all cases. Both deep-frozen and freeze-dried cortical allografts were strong enough to withstand loads taken by the reconstructed spine.

Adolescent↗
PubMed1995

Morbidity and mortality for elderly patients with fractured neck of femur treated by hemiarthroplasty.

Patients above the age of 60 with displaced femoral neck fractures are treated by hemiarthroplasty in Singapore because of our low life expectancy. This study evaluates the morbidity and mortality of 110 such patients operated on in our department between January 1990 and December 1992. It has clinical significance because of the rapidly ageing population of Singapore. The mean age was 78 years with a female preponderance of 5:1. They were predominantly Chinese. None of the patients were Malay. This is the first study showing that such fractures are rare among Malays. Most fractures were due to trivial trauma. Fifty-eight per cent had co-existing illness(es). The mean hospitalization stay was 20 days. There were considerable and local complications in 15 patients. Twenty-five patients died. Of the remaining patients, 17 (20 per cent) were unable to regain independent ambulation. The mortality rate at 3, 6 and 12 months was 6.4 per cent, 9.1 per cent and 15 per cent respectively. Males showed a significantly higher mortality rate than females. Also, patients living in government-built high rise flats had a significantly higher mortality rate than those residing in privately owned homes.

Aged↗