Acoustic monitoring (RFM) of total hip arthroplasty results of a cadaver study

Introduction

At present there are no reliable non-traumatic and non-invasive methods to analyse the healing process and loosening status after total hip replacement. Therefore early as well as late loosening of prosthesis and interface component problems are difficult to be found or diagnosed at any time.

Methods

In a cadaver study the potential application of Resonance Frequency Monitoring (RFM) will be evaluated as a non-invasive and non-traumatic method to monitor loosening and interface problems in hip replacement. In a 65 year old female cadaver different stability scenarios for a total hip replacement (shaft, head/modular head and cup, ESKA, Luebeck, Germany) are simulated in cemented and cement less prosthesis and then analysed with RFM. The types of stability vary from secure/press-fit to interface-shaft disruption.

Results

The RFM shows in cemented as well as cement less prosthesis significant intra-individual differences in the spectral measurements with a high dynamic (20 dB difference corresponding to the factor 100 (10000%)), regarding the simulated status of stability in the prosthesis system.

Conclusion

The results of the study demonstrate RFM as a highly sensitive non-invasive and non-traumatic method to support the application of RFM as a hip prosthesis monitoring procedure. The data obtained shows the possibility to use RFM for osteointegration surveillance and early detection of interface problems, but will require further evaluation in clinical and experimental studies.     

Repetitive Electrical Stimulation of Peripheral Nerve and Spinal Cord Activity

Abstract

Spinal cord neuron and dorsal column fiber responses to electrical stimulation of the sciatic nerve in anesthetized cats were recorded before, during, and after periods of repetitive electrical stimulation of the sciatic nerve through an implantable nerve cuff stimulator device of the type and method used in human patients for pain relief. In previous publications from this laboratory using similar experimental conditions, we reported that repetitive electrical stimulation of the peripheral nerve suppressed all components of the compound action potential of nerves. The present study corrfmns that 5 percent of the spinal cord units studied showed facilitated discharge, 46 percent showed inhibited or depressed discharge, 36 percent underwent no change, and 13 percent showed equivocal responses to repetitive electrical stimulation. Inhibition of dorsal column fiber activity following repetitive electrical stimulation of peripheral nerve is not consistent with the Melzack-Wall gate hypothesis in which suppression of small fiber nociceptive input is mediated by large fiber activity. Our work suggests that the most commonly observed effect 9f electroanalgesia is to cause a more diffuse depreSSIon of nociceptive as well as nonnociceptive spinal cord activity.     

Care related pain in hospitalized patients: A cross‐sectional study

Context: Care‐related pain includes pain occurring during transportation, movement, diagnostic imaging, physical examination, or treatment. Its prevalence has never been assessed in a large adult inpatient population. Objective: To identify the procedures likely to induce or increase pain in hospital patients, attempting to separate the most painful from those reported as most frequently inducing pain. Design: A single‐day cross‐sectional survey conducted in two large French teaching hospitals, including all hospitalized patients, free of communication problems. One third was randomly selected and interviewed about the painful episodes that had occurred or were associated with the procedures performed during the previous two weeks. Patients were interviewed using a structured questionnaire. Results: Six‐hundred‐eighty‐four patients were randomly selected. Six‐hundred‐seventy‐one painful events were reported in 55% of the patients, with an average of 1.8events/patient. Fifty‐two percent of the painful events were associated with procedures performed by non‐medical staff; 38% of the painful episodes occurred during procedures involving vascular puncture and 24% during patients’ mobilization. In 57% of painful procedures, pain was rated as severe or extremely severe. The most painful procedures were invasive procedures, other than vascular and non vascular punctures (74% of severe and extremely severe painful episodes). Maximum pain intensity was rated higher for procedures that were repeated than for those experienced only once (62% versus 53%, p=0.02). Conclusion: This survey gives new insight into our daily practice. Proper management of care‐related pain should be a major concern of all hospital staff to improve the quality of our health care.     

An immuno-precipitation assay for determining specific interactions between antibodies and phage selected from random peptide expression libraries

Libraries of random peptides displayed by bacteriophage can be screened to select phage expressing peptides that specifically bind antibodies, so that the peptide sequence motifs expressed by the phage can help to define the epitopes of the antibodies. It is often desirable to screen antibody-selected phage for binding of the selecting antibody in an immunoassay in order to verify the specificity of the interaction. Enzyme-linked immunosorbent assays (ELISAs) are commonly used for this purpose. However, for many antibodies, the best techniques for measuring specific, high affinity interactions are immuno-precipitation assays. Immuno-precipitation was therefore investigated as a means of measuring interactions between antibodies and phage clones selected from random peptide display libraries. Three mouse monoclonal antibodies specific for glutamic acid decarboxylase were used to select peptides as 9-mers on T7 phage, linear 12-mers on pIII of M13 phage, or constrained 15-mers on pVIII of M13 phage. Following the cloning and sequencing of selected phage, mixtures of antibody and phage were incubated in solution and the immune complexes were precipitated with Protein G bound to Sepharose beads. In order to detect and quantitate the phage that had formed immune complexes and been precipitated, advantage was taken of the biological properties of the phage by inducing infection of Escherichia coli by the precipitated phage. The aim was to quantitate the phage precipitated by determining the number of plaques produced, which would therefore be proportional to the degree of interaction between the phage and the antibody in solution. The results presented here indicate that this method of measuring monoclonal antibody interactions with phage selected for expression of peptides recognised by the monoclonal antibody is highly specific and sensitive.     

Anti-GBM nephritis in the mouse: severe proteinuria in the heterologous phase

Summary Highly reproducible anti glomerular basement membrane (GBM) nephritis has been induced in the mouse after a single injection of rabbit or goat antibody against purified homologous GBM. The severity of albuminuria was closely related to the amount of antibody given. With doses of 4 mg or more, low serum albumin concentrations, sometimes accompanied by ascites and oedema, were observed after 1 week. Glomerular injury was characterized by an initial accumulation of polymorphonuclear granulocytes followed by thrombosis and necrosis, the extent of which defined the outcome of the glomerulonephritis. With high doses of antibody the exudative lesions entered a chronic phase, while at doses lower than 2 mg remission of the lesions occurred. Immunofluorescence studies showed prompt linear fixation of the injected anti-bodies to the glomerular capillary wall, accompanied by immediate binding of C3 in a fine granular pattern. Fibrin deposits appeared at 2 h in some glomeruli, increased thereafter, and were present after one day in more than 90% of the glomeruli in mice that had received 4 mg of antibody. This new reproducible model in the mouse is suited for the study of the relationship between activation of mediator systems, histological lesions, and proteinuria.