Biomedical subjects

A Nawab

Publications and source records attributed to A Nawab.

4 recordsLinked to original sources

PubMed2000

Mechanical properties of compacted morselized cancellous bone graft using one-dimensional consolidation testing.

Failures of orthopaedic procedures that use morselized cancellous bone (MCB) graft for load bearing are often due to gross displacement within the graft material. For this reason the mechanical behavior of MCB must be better understood. Our purpose is to present a detailed testing methodology for the mechanical characterization of MCB, and to illustrate how this methodology can be used to study the influence of water and fat content. Complete one-dimensional consolidation testing was performed on bovine cancellous bone processed to represent MCB typically used in surgery (52% water, 31% fat). The one-dimensional consolidation strain under a stress of 1.09MPa was 30.9% and the confined modulus was 8.0MPa. The coefficient of consolidation (rate of consolidation) was 2. 2x10(-5)cm(2)/s and the coefficient of secondary strain (steady-state creep rate) was 1.9%. While reducing the water content alone had some influence on properties, reducing the fat content improved both the static and dynamic behavior. A sample of MCB which had fat intentionally minimized and a lower overall moisture content (56% water, 5% fat) demonstrated 23.1% strain, a confined modulus of 9.6MPa, a coefficient of consolidation of 3.4x10(-3)cm(2)/s, and a coefficient of secondary strain of 0.9%. The test methods described in this technical note can be used to evaluate the influence of fluid content on the mechanical behavior of MCB.

Animals↗

PubMed1999

Bone grafting from the proximal tibia.

OBJECTIVE: A retrospective study was undertaken to analyze the results of proximal tibial bone grafts with immediate postoperative weight bearing. METHODS: Over a 2-year period, 54 patients underwent bone grafting harvested from the proximal tibia. Postoperatively patients were allowed to bear weight as tolerated on the donor site. Mean follow-up was 26.4 weeks, with a range of 6 to 80 weeks. Indications for bone grafting were fresh fractures with primary grafting and nonunions. RESULTS: The overall complication rate was 1.9%, with one patient suffering a local hematoma. No major complications such as fracture, sensory deficit, or wound infection were observed. Immediate postoperative weight bearing did not have any deleterious effects. Higher complication rates for iliac graft sites have been reported. The amount of bone that can be harvested is usually more than adequate. CONCLUSION: Complication rates are low without significant patient morbidity. Most importantly, the patients may start weight bearing immediately after surgery.

Adult↗

PubMed1998

Tremulous jaw movements in rats: a model of parkinsonian tremor.

Several pharmacological and neurochemical conditions in rats induce 'vacuous' or 'tremulous' jaw movements. Although the clinical significance of these movements has been a subject of some debate, considerable evidence indicates that the non-directed, chewing-like movements induced by cholinomimetics, dopamine antagonists and dopamine depletions have many of the characteristics of parkinsonian tremor. These movements occur within the 3-7 Hz peak frequency range that is characteristic of parkinsonian tremor. Tremulous jaw movements are induced by many of the conditions that are associated with parkinsonism, and suppressed by several different antiparkinsonian drugs, including scopolamine, benztropine, L-DOPA, apomorphine, bromocriptine, amantadine and clozapine. Striatal cholinergic and dopaminergic mechanisms are involved in the generation of tremulous jaw movements, and substantia nigra pars reticulata appears to be a major basal ganglia output region through which the jaw movements are regulated. Future research on the neurochemical and anatomical characteristics of tremulous jaw movements could yield important insights into the brain mechanisms that generate tremulous movements.

Animals↗

PubMed1997

In vivo study of stainless steel and Ti-13Nb-13Zr bone plates in a sheep model.

A sheep study was performed to compare the in vivo performance of bone plates of 316L stainless steel and a new titanium alloy, titanium + 13% niobium + 13% zirconium (Ti-13Nb-13Zr), which had been subjected to a diffusion hardening treatment to produce a blue, wear resistant surface. Bone plates and screws of stainless steel and diffusion hardened Ti-13Nb-13Zr were implanted in adult sheep, in one group (with unosteotomized femurs) for 16 weeks, and in the other (with osteotomized femurs) for 8 weeks. At harvest, the diffusion hardened Ti-13Nb-13Zr devices had superior fixation strength, with greater screw torque out strength and fewer loose screws. In the osteotomized animals, the femurs with diffusion hardened Ti-13Nb-13Zr plates had higher torsional strength after removal of the implants; however, the difference was not statistically significant. In the unosteotomized animals, the torsional strength of the femurs was identical for both materials. There was a slightly reduced incidence of infection (bacterial adhesion) for the sheep with diffusion hardened Ti-13Nb-13Zr implants. In a parallel in vitro study, the magnetic resonance imaging compatibility of Ti-13Nb-13Zr was significantly superior to that of stainless steel. This indicates that diffusion hardened Ti-13Nb-13Zr may be an attractive alternative material for osteosynthesis.

Alloys↗