Mechanical properties of morcellised bone graft with the addition of hydroxyapatite

Mixtures of morcellised bone graft (MBG) and hydroxyapatite (HA) are frequently used in revision arthroplasty surgery. However, the changes in the mechanical properties from adding HA to MBG are unknown. This study used a uniaxial compression test to replicate impaction bone grafting and subsequent early postoperative weightbearing to investigate the effect of adding different proportion of HA to MBG. To achieve this aim, human MBG was subjected to increasing impaction forces and the apparent stiffness and creep for each stress level determined. Subsequently, increasing proportions porous and non porous HA were added to the MBG. The major findings were that the apparent stiffness for MBG increased and the associated creep decreased both with the application of increasing stress and with the addition of increasing proportions of HA. In conclusion, greater proportions of HA in the graft mixture improved the mechanical response compared with MBG impacted under the same force. This improvement replicated the properties of pure MBG under high axial stress. This study indicates that graft mixtures of MBG and HA can be tailormade for patients. The need for less impaction force in MBG:HA mixtures to obtain the same properties as pure MBG may decrease the risk of intraoperative fracture.

Modification of Enrichment Protocols for TECRA Listeria Visual Immunoassay Method 995.22: Collaborative Study

A collaborative study was conducted to validate new enrichment methods for the TECRA Listeria Visual Immunoassay (TLVIA). These new methods incorporate a newly formulated medium, TECRA Listeria Enrichment Broth, which does not contain the highly toxic antifungal agent, cycloheximide. The new procedures will provide an alternative to the enrichment procedures described in AOAC Method 995.22. Three food types (raw ground beef, lettuce, and ice cream) were analyzed in the United States, and 2 food types (cooked turkey and cooked fish fillets) were analyzed in Australasia. Thirty collaborators participated in the study, 16 in Australasia and 14 in the United States. With the exception of one batch of ground beef, comparison of the proportion of positive test portions (p ≥ 0.05) showed no significant difference between the TLVIA and the reference method for the 5 foods at 3 inoculation levels. For the one batch of naturally contaminated raw ground beef, the TLVIA gave significantly more confirmed positive results than the reference method.

The CPE network: creating an evidence base for continence product selection

Selecting continence products for an individual patient or hospital contract is often a daunting task. This article describes the evaluation process developed for a program of government-funded multicenter evaluations of continence products established in the United Kingdom to provide an evidence base for product selection. The essential requirements of an evaluation are discussed, together with the methodologic and statistical issues that such evaluations present. The strengths and limitations of multicenter trials are examined and suggestions are made regarding other areas of nursing in which this approach could be usefully adopted.

Efficacy of a tiered therapy defibrillator system used to treat recurrent ventricular arrhythmias refractory to drugs

OBJECTIVE

To evaluate an implantable tiered therapy defibrillator system that delivered antitachycardia pacing treatment for slower well tolerated ventricular tachycardias and cardioversion or defibrillation for fast tachycardias or ventricular fibrillation.

METHODS

A tiered treatment device (Ventritex Cadence V-100) was implanted in 30 patients with ventricular tachycardia that was refractory to drugs. Efficacy was evaluated by the responses of induced or spontaneous arrhythmias to the treatments delivered.

RESULTS

Antitachycardia pacing successfully terminated 80% of episodes of ventricular tachycardia induced by non-invasive programmed stimulation, but acceleration was brought about by pacing in six patients in 10% of episodes. During a follow up of two to 17 (mean seven) months, 18 patients (60%) had recurrence of ventricular arrhythmias. Antitachycardia pacing terminated ventricular tachycardia in 17 of 18 patients in 87% of episodes. Twelve patients received shocks for ventricular tachycardia or fibrillation. Failure of pacing, with subsequent cardioversion, occurred in nine patients (50%) in one or more episodes. Acceleration of tachycardia by pacing occurred in 10 patients in 5% of episodes. Only two of these patients had experienced acceleration of previously induced arrhythmia. Five patients had spontaneous fast ventricular tachycardia or fibrillation treated by cardioversion or defibrillation. Spurious treatment was delivered in nine patients (30%), during atrial fibrillation in five, sinus tachycardia in two, and because of fracture of the sensing lead system in two patients. The retrieval of stored intracardiac electrograms was of clinical value in assessing spurious treatment.

CONCLUSIONS

Tiered treatment was effective in terminating recurrent ventricular arrhythmias in these selected patients. Most episodes were treated successfully by pacing, and resistant tachycardias, pacing induced acceleration, or haemodynamically compromising arrhythmias were treated by shocks.

Improving the performance of small incontinence pads: a study of "wet comfort"

PURPOSE

The wet comfort of small, disposable incontinence pads has been found to correlate strongly with overall acceptability. This study examined the relationship between pad properties (absorption capacity, strike-through, and wetback) and wet comfort.

DESIGN

A group of women with light incontinence were asked to report on the wet comfort of a series of experimental pads made up to the same design geometry but in different combinations of materials.

METHODS

Three different pad variants were selected, and two experiments were conducted. Experiment 1 used a single-blind design in which 20 testers were supplied with a random mix of the three unlabeled pad variants. All pads were saved for weighing and scored for overall performance, wet comfort, and absorbency. In experiment 2, subjects used each pad variant in turn for 1 week and at the end of each week compared that pad with the one used the previous week.

MAIN OUTCOME MEASURES

Absorption capacity, wetback, and strike-through properties for each pad variant were measured in the laboratory setting, and wet comfort was measured by a written tool completed by participants during clinical trials.

RESULTS

Data analysis from experiment 1 revealed statistically significant differences among pad variants, particularly when assessed for absorbency. Differences for wet comfort were less marked and only achieved significance when those with ratings of good or OK for wet comfort were compared with those with a score of poor. In experiment 2, no statistically significant differences were found for wet comfort.

CONCLUSIONS

Overall, the improvement in wet comfort achieved by a substantial increase in absorption capacity and reduction in wetback were disappointing. The relatively small sample and the design specifications of the pad may have masked differences. Cost considerations mean that more evidence is needed to justify the inclusion of more expensive materials and production stages in the manufacture of small pads.

Verbal conditioning of male and female schizophrenics as a function of experimenter proximity

Verbal conditioning of male and female schizophrenics and nonschizophrenics was observed as Ss sat at different distances and orientations from an E who delivered a positive word/positive tone reinforcer ("Good"). Results indicated that the presence vs. absence of diagnostic differences in learning depended on (a) the sex of the Ss; and (b) the distance that Ss sat from the E. The absence of overall diagnostic group differences in learning and the finding that in some proxemic conditions schizophrenics learned more than nonschizophrenics are consistent with the view that under appropriate conditions schizophrenics emit behaviors that are incompatible with an assumption of schizophrenic deficit.

A Stream-Wetland-Riparian (SWR) index for assessing condition of aquatic ecosystems in small watersheds along the Atlantic slope of the eastern U.S

As part of a regional study by the Atlantic Slope Consortium (ASC) to develop ecological and socioeconomic indicators of aquatic ecosystem condition, we developed and tested a protocol for rapidly assessing condition of the stream, wetland, and riparian components of freshwater aquatic ecosystems. Aspects of hydrology, vegetation, in-stream and wetland characteristics, and on-site stressors were measured in the field. The resulting metrics were used to develop an index of overall condition, termed the Stream-Wetland-Riparian (SWR) Index. Values of this Index were compared to existing biotic indices and chemical measures, and to a Landscape Index created using satellite-based land cover data and a geographic information system (GIS). Comparisons were made at several levels of spatial aggregation and resolution, from site to small watershed. The SWR Index and associated Landscape Indices were shown to correlate highly with biological indicators of stream condition at the site level and for small contributing areas. The landscape patterns prevalent throughout the entire watershed do not necessarily match the patterns found adjacent to the stream network. We suggest a top-down approach that managers can use to sequentially apply these methods, to first prioritize watersheds based on a relative condition measure provided by the Landscape Index, and then assess condition and diagnose stressors of aquatic resources at the subwatershed and site level.

The role of bradykinin in the regulation of blood flow to hindlimb muscle groups of the anaesthetized cat

1. Male cats were anaesthetized with alphaxalone-alphadolone and breathed spontaneously following tracheotomy, Using coloured microspheres, muscle blood flow was measured at rest and during two periods of contraction elicited by simultaneous stimulation of the left sciatic and femoral nerves at 3 Hz for 10 min. In one group, the hindlimb blood flow was allowed to increase during muscle contraction and in another group the perfusion of the hindlimb was limited by a stenosis on the left external iliac artery. 2. In the absence of flow restriction, soleus muscle blood flow increased from 18.9 +/- 3.8 to 30.4 +/- 3.3 ml min-1 (100 g tissue)-1 (n = 6; P < 0.02) and gastrocnemius muscle blood flow increased from 24.8 +/- 5.9 to 61.6 +/- 12.8 ml min-1 (100 g tissue)-1 (n = 6; P < 0.01) during contraction. The bradykinin (BK) antagonists HOE 140 (1 mg kg-1, i.v.) did not affect the response in either the soleus (37.7 +/- 7.3 ml min-1 (100 g tissue)-1; n = 6; n.s.) or the gastrocnemius (62.9 +/- 7.9 ml min-1 (100 g tissue)-1; n = 6; n.s.) muscles. 3. In the stenosis group, soleus muscle blood flow increased from 9.8 +/- 2.3 to 22.9 +/- 4.9 ml min-1 (100 g tissue)-1 (n = 6; P < 0.01) and gastrocnemius muscle blood flow increased from 15.8 +/ 3.4 to 36.4 +/- 5.5 ml min-1 (100 g tissue)-1 (n = 6; P < 0.01) during contraction. Following administration of HOE 140, functional hyperaemia in the soleus muscle was unaffected (blood flow, 17.8 +/- 2.2 ml min-1 (100 g tissue)-1, n = 6; n.s.) white blood flow in the gastrocnemius muscle was reduced to 21.8 +/- 6.0 ml min-1 (100 g tissue)-1 (n = 6; P < 0.05). 4. The results show that BK does not contribute ot functional hyperaemia associated with twitch contraction at 3 Hz when blood flow is unrestricted, but may contribute up to 40% of the vasodilation of predominantly glycolytic muscle groups such as the gastrocnemius when flow is restricted. BK plays no role in hyperaemia associated with twitch contraction of oxidative muscle groups such as the soleus.