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Biomedical subjects

R M Smith

Publications and source records attributed to R M Smith.

At least 37 records · Page 2Linked to original sources
PubMed2002

Functional handgrip test to determine the coefficient of static friction at the hand/handle interface.

The aim was to devise a method of measuring friction at the hand/handle interface during a functional handgrip task. No descriptions of methods of this kind was found in the literature. An indirect technique of measuring normal grip force was employed to determine friction at the hand/handle interface while performing a functional handgrip action with a grabrail. The coefficient of static friction was calculated between palmar skin (dry, wet, and soapy hands) and five grabrail materials (stainless steel, powder-coated steel, chrome, textured aluminium and knurled steel). Thirty subjects participated (15 female, 15 male), who were aged from 17 to 45 years with a mean age of 30 years. Knurled steel produced a significantly larger mean coefficient of static friction than chrome, powder-coated steel and stainless steel, and textured aluminium had a significantly larger coefficient of static friction than stainless steel. Soapy hands produced the lowest mean coefficients (0.46+/-0.04), significantly less then dry (1.72+/-0.16, p <0.001) and wet hands (1.42+/-0.16, p <0.001). This study has demonstrated the influence of grabrail material and palmar skin treatments on static friction at the hand/handle interface. The use of a functional test that incorporates an indirect determination of normal handgrip force has provided a quantitative method of observing stability at the hand/handle interface.

Adolescent↗
PubMed2002

Injury patterns associated with mortality following motorcycle crashes.

All patients involved in motorcycle crashes admitted to various hospitals in the Yorkshire region of UK between January 1993 and December 1999 were retrospectively reviewed to identify the factors that are likely to predict a reduced survival. Of the 1239 patients requiring hospital admission, 74 died. The probability of reduced survival was estimated by a logistic regression model using independent variables such as head injury, thoracic trauma, abdominal injury, spinal injury and pelvic fracture and a compound variable of pelvic fracture combined with a long bone fracture. The odds ratio for head injury was 0.349, chest injury 0.39, abdominal injury 0.42, and the compound variable (pelvis plus a long bone fracture) 0.576. The mean injury severity score (ISS) in the fatal group was 35.96 compared to 12.2 in the group that survived (P<0.01). There was a significant difference in the Glasgow coma scale (GCS) between patients wearing a helmet and those that did not wear any protective headgear (P=0.0007). Head injury followed by chest and abdominal trauma were found to predict a reduced survival rate. Use of helmets should continue to be compulsory. Chest and abdominal injuries should be diagnosed and treated early to reduce mortality.

Abdominal Injuries↗
PubMed2002

Fluoroscopy-based multiplanar image guidance for insertion of sacroiliac screws.

A prospective controlled experimental study was done to assess the value of fluoroscopy-based, computer-assisted orthopaedic surgery for the insertion of sacroiliac screws and to compare this new technology with the conventional technique, using image intensification. In a simulated surgical setup, 140 cannulated screws were placed into the S1 and S2 vertebral bodies of 35 pelvic models. The screws were inserted under fluoroscopy-based image guidance or with the conventional technique. Different drills were tested with both techniques, including a 2.8-mm guide wire and a 5-mm solid drill. The 2.8-mm guide wire proved inaccurate with the computer-assisted image guidance system because of guide wire flexibility. Using the more rigid 5-mm drill, the results of computer-assisted image guidance were comparable with the image intensifier technique. The radiation exposure during screw insertion was reduced considerably when using the image guidance system. System-specific requirements warranted adjustment of surgical technique and instruments. The major advantages of this new technology are immediate intraoperative image acquisition and provision of surgical guidance in as much as four planes simultaneously. The results of this experimental study are encouraging and have led to initiation of a clinical trial.

Bone Screws↗
PubMed2002

Temperature rise during reamed tibial nailing.

The current study determined the temperature rise during reamed tibial intramedullary nailing in vivo. Eighteen adult patients were studied. The tibial medullary canal diameter ranged from 8 to 11 mm and was reamed to at least 1.5 mm above the required nail diameter with AO reamers. Reaming of the medullary cavity ranged from 9 to 12 mm before nail insertion. Intraoperative monitoring of the heat produced during reaming of the medullary cavity was done by inserting two platinum resistance thermometer probes into the cortical bone at the short isthmic segment of the tibial shaft. The probes were connected to a data logger, and temperature readings were taken every 5 seconds during each reaming procedure. The mean tibial temperature before initiation of reaming was 35.6 degrees C (standard deviation, +/- 0.5 degrees), and peak temperatures recorded were from 36.1 degrees C to 51.6 degrees C. A direct correlation was observed between temperature elevation and amount of reaming. With reaming above 10 mm, tibias with a canal diameter of 8 mm showed a statistically higher temperature rise compared with tibias with a canal diameter of 9, 10, or 11 mm. No patients had intraoperative or postoperative complications related to skin or bone thermal necrosis, and bony healing progressed uneventfully. The small amount of reaming required to insert a nail into a normal 9-, 10-, or 11- mm tibial canal does not seem to produce a clinical problem. Reaming smaller canals (8 mm) to a larger size may induce a significant heating effect.

Adolescent↗
PubMed2002

Friction burns within the tibia during reaming. Are they affected by the use of a tourniquet?

We have carried out a prospective, randomised trial to measure the rise of temperature during reaming of the tibia before intramedullary nailing. We studied 34 patients with a mean age of 35.1 years (18 to 63) and mean injury severity score of 10 (9 to 13). The patients were randomised into two groups: group 1 included 18 patients whose procedure was undertaken without a tourniquet and group 2, 16 patients in whom a tourniquet was used. The temperature in the bone was measured directly by two thermocouples inserted into the cortical bone near the isthmus of the tibial diaphysis. Reaming was carried out to at least 1.5 mm above the required diameter of the nail. Blood loss was assessed by recording the preoperative and postoperative haemoglobin (Hb) level. The minimum clinical follow-up was six months. In group 1 (no tourniquet), the mean Hb dropped 2.8 g/dl from 14.3 +/- 1.02 g/dl to 11.5 +/- 1.04 g/dl (p = 0.0001), whereas with the tourniquet, the mean decrease was 1.3 g/dl from 14 +/- 1 g/dl to 12.7 +/- 1.3 g/dl (p = 0.007). This difference was not statistically significant. The mean initial tibial temperature was 35.6 degrees C (SD 0.6) and rose with reaming to levels between 36.3 degrees C and 51.6 degrees C. The highest temperatures were obtained with the largest reamers (11 and 12 mm, p = 0.0001) and the most rapid rise with the smallest diameters of medullary canal (8 or 9 mm). The rise of temperature was transient (20 s). We were unable to identify any effect of the use of a tourniquet on the temperature achieved. Reamed intramedullary tibial nailing induces a transient elevation of temperature which is directly related to the amount of reaming.

Adolescent↗
PubMed2002

Review: systemic effects of femoral nailing: from Küntscher to the immune reactivity era.

Intramedullary nailing is the preferred treatment for stabilizing femoral diaphyseal fractures. Despite the superior biomechanical advantages over other implants, its use especially in some selected groups of patients, has been questioned because of possible harmful systemic effects of intramedullary reaming. The lung seems to be the primary target for fat embolization and for mediated effects by inflammatory reactions. The latter are initiated in the immediate aftermath after injury, and femoral nailing can amplify these responses. The role of reaming in the context of early femoral fracture fixation in the patient experiencing trauma is debatable. This review article focuses on the evidence that has emerged during the past century regarding the systemic effects of femoral nailing.

Animals↗
PubMed2001

Static friction properties between human palmar skin and five grabrail materials.

The purpose of this study was to investigate the static friction properties between human palmar skin and five grabrail materials (chrome, stainless steel, power-coated steel, textured aluminium and knurled steel) for dry, wet and soapy hands. Thirty subjects (15 female, 15 male) participated in this study, their ages ranging from 19 to 45 years with a mean age of 28 years. The normal force, friction force, and coefficient of static friction were determined by measuring three-dimensional forces while slipping the palm of the hand over the surface of a grabrail. A repeated measures ANOVA indicated that gender, age, hand size and trial effect had no significant influence (p>0.05) on these results. The coefficient of friction (p<0.001) and friction force (p<0.001) were significantly lower when the hand was soapy than when it was dry or wet. The normal force applied when the hand was soapy was significantly greater (p<0.001) than when it was dry or wet. No significant difference was found between dry and wet hands. The two textured materials displayed superior friction properties when the hand was soapy, while the smooth materials performed best when the hand was dry.

Adult↗
PubMed2001

Removal of the retained fragment of broken solid nails by the intra-medullary route.

The development of solid nails has not eliminated the risk of occasional nail failure. It has been suggested that subsequent intra-medullary removal of solid nail fragment may be virtually impossible and thus major surgery is required for their revision. We report two cases of hardware failure of a solid intra-medullary nail (Synthes solid femoral and tibial nail) and describe their successful intra-medullary removal using the Synthes extraction kit.

Adult↗
PubMed2001

Extending fixation beyond the working length of an intramedullary nail with a linked intramedullary and extramedullary fixation in complex femoral fractures; a brief series.

We report the use of a fixed-angle side-plate device linked to an intramedullary nail in the femur with the interlocking screws applied through the plate. The 95 degrees device extends the effective length of the nail and increases the stability of the fixation. This technique is one of various adaptations that can be recommended to stabilise a complex combination of femoral fractures. This is a report of four such patients.

Adult↗
PubMed2001

Inter-segment foot motion and ground reaction forces over the stance phase of walking.

OBJECTIVE: To compare the magnitude and patterns of motion of the rearfoot segment relative to the leg, forefoot segment relative to the rearfoot, height change in the medial longitudinal arch and ground reaction forces of normal adult males during the stance phase of walking. BACKGROUND: Knowledge of normal motion of the rearfoot and forefoot segments and of the arch during stance phase is important in clinical management. METHODS: Motion data were obtained from surface markers, and force data from a force plate, from the right limb of participants while walking at a self-selected pace. RESULTS: Stance phase range of motion across sagittal, frontal and transverse planes was 12 degrees, 4 degrees and 10 degrees for the forefoot, compared to 22 degrees, 8 degrees and 10 degrees for the rearfoot. Most motion occurred at the beginning and end of stance phase when support was via only the rearfoot or forefoot, and when forces were maximal. Arch height decreased from heel contact and increased after heel rise to its maximum at toe-off. CONCLUSIONS: The extent of forefoot segment motion confirms the significance of midfoot joints to normal foot function. Between foot flat and heel rise, the forefoot pattern of motion is indicative of foot stability. Typical foot motion does not obey descriptions of triplanar motion such as 'pronation' and 'supination'. RELEVANCE: Typical stance phase foot motion has been described according to a forefoot:rearfoot model and rearfoot:leg model of motion, together with profiles of medial longitudinal arch height and ground reaction forces. This information can be applied in the management of foot dysfunction and should stimulate research into midfoot motion and overall control of the foot.

Adult↗
PubMed2001

TNF alpha is required for hypoxia-mediated right ventricular hypertrophy.

Hypoxia has been shown to activate the pleiotropic cytokine TNFalpha in the lung. TNFalpha in turn, is known to induce pulmonary vasoconstriction. Additional effects of this cytokine in hypoxia mediated cardiopulmonary remodeling are poorly understood. To further evaluate the role of TNFalpha in chronic hypoxia we exposed TNFalpha null (TNFalpha-/-) and wild-type mice to three weeks of hypobaric hypoxia (10% O2). Equivalent erythocytosis (Hematocrit increased by > 40%) developed in both genetic backgrounds. In contrast, right ventricular systolic pressure increased in response to three weeks of hypoxia in the wild-type mice (> or = 75%), yet was unaltered in the TNFalpha-/- mice. Concomitantly right ventricular hypertrophy was attenuated in the TNFalpha-/- mice (35 +/- 5% increase) when compared to wild-type mice (124 +/- 6% increase p < 0.001, n > or = 20). Interestingly in both strains the lung wet weights increased to a similar degree in response to hypoxia. In conclusion, our data demonstrate that TNFalpha is an integral autocoid in chronic hypoxia mediated right ventricular hypertrophy. Moreover, additional components of cardiopulmonary remodeling may be regulated by TNFalpha signaling as suggested by the negligible right ventricular systolic pressure response to hypoxia in the absence of TNFalpha.

Animals↗
PubMed2001

Plasma membrane resident 'fusion complexes' mediate reconstituted exocytosis.

Calcium-triggered exocytosis is thought to be mediated by membrane-associated protein complexes. In sea urchin eggs, high concentrations of calcium activate multiple 'fusion complexes' per cortical vesicle-plasma membrane docking site. Some of these fusion complexes are known to reside in the vesicle membrane. It is not known if fusion complexes also reside in the plasma membrane, or if plasma membrane-resident fusion complexes require cognate partners in the vesicle membrane. Using reconstitution, we show that N-ethylmaleimide treatment of either vesicles or plasma membrane fragments prior to reconstitution does not completely inhibit exocytosis. Treatment of both components did result in complete inhibition. Upon reconstitution, cortical vesicles and the early endosomes formed by compensatory endocytosis both contributed, on average, two fusion complexes per reconstituted docking site. The plasma membrane contributed, on average, two fusion complexes per docking site when assembled with cortical vesicles, but only one complex when reconstituted with endosomes. We conclude that there are at least two types of plasma membrane-resident fusion complexes that participate in reconstituted cortical vesicle-plasma membrane fusion. The activity of one of these fusion complexes is target-specific for cortical vesicles, while the second type also supports fusion with endosomes.

Actins↗
PubMed2001

Bilateral, simultaneous, spontaneous rupture of quadriceps tendons without trauma in an obese patient: a case report.

This is a single case report of bilateral, simultaneous, spontaneous rupture of the quadriceps tendon caused by obesity without trauma. The patient was a 52-year-old, 350-pound, morbidly obese man with a sedentary life style whose quadriceps tendons ruptured while he was descending a staircase. He presented with a large deficit superior to the patella and an inability to straighten his knees. After surgery, his knees were immobilized in extension for 6 weeks, followed by gradual weight bearing and gait training with braces. He was weaned off the braces as he increased the range of motion and strength in his knees. The rehabilitation process was protracted, and he returned to full-time work 6 months postinjury. Physiatrists should be familiar with the diagnosis, treatment, and rehabilitation of this rare condition.

Humans↗
PubMed2001

Induction of immune hyporesponsiveness after portal vein immunization with ovalbumin.

BACKGROUND: Previous work has demonstrated prolonged allograft survival after donor-specific portal vein immunization before the transplantation. The purpose of this study was to examine the potential mechanism of portal vein-induced hyporesponsiveness after portal vein immunization with the soluble protein ovalbumin. METHODS: Balb/c mice were immunized with a portal vein injection of ovalbumin. After the immunization, in vivo delayed-type hypersensitivity response and in vitro proliferative response of ovalbumin-specific T cells were assessed to determine host immune response. Type 1 (IL-2, IL-12, IFN-gamma) and type 2 (IL-4, TGF-beta) regulatory cytokines were assessed by semiquantitative reverse transcriptase polymerase chain reaction. Sera anti-ovalbumin IgG, IgG1, and IgG2a were measured by enzyme-linked immunosorbent assay, and the antigen-presenting ability of liver nonparenchymal cells (NPCs) was assessed by T-cell proliferation to ovalbumin in vitro. RESULTS: There was significant inhibition of ovalbumin-specific delayed-type hypersensitivity and T-cell proliferation in portal vein-immunized mice compared with intraperitoneal-immunized or control mice. Reverse transcriptase polymerase chain reaction analysis results showed that lymphocytes from portal vein-immunized mice exhibited decreased type 1 and increased type 2 cytokine messenger RNA expression compared with intraperitoneal-immunized or control animals. The type 2 cytokine response of lymphocytes from ovalbumin portal vein-immunized mice correlated with increased sera ovalbumin-IgG1 and decreased IgG2a. The results of an antigen-presenting assay revealed that liver NPCs were deficient antigen-presenting cells compared with adherent cells from heart or spleen. CONCLUSIONS: Processing of ovalbumin by hepatic NPCs results in hyporesponsiveness to ovalbumin by an impaired type 1 cytokine response and a preferential shift toward a type 2 cytokine response, possibly because of defective antigen presentation by hepatic NPCs. Intrahepatic processing of antigen may play an important role in the development of strategies to reduce host immunoreactivity against transplanted allografts.

Animals↗