Ablation of bone, cartilage, and facet joint capsule using Ho:YAG laser.

OBJECTIVE: The objective of this study was to determine of the efficiency of holmium:YAG laser for bone ablation, compared to cartilage and soft tissue of the intervertebral foramen of the lumbosacral spine. BACKGROUND DATA: The holmium:YAG (Ho:YAG) laser has been used for ablation of bulging or prolapsed discs and also has the potential for decompression of the nerve root when there is narrowing of the foraminae (foraminoplasty). It is proposed that laser ablation of bone and ligament of the intervertebral foramen for nerve root decompression using the Ho:YAG laser is able to produce sufficient bone ablation without inducing significant thermal necrosis in surrounding tissues due to its short absorption length, which could result in significant clinical advantages. MATERIALS AND METHODS: Experiments were performed on samples of laminar bone, facet joint capsule, and cartilage for quantitative and qualitative determination of the effect of Ho:YAG ablation on tissue mass loss using a range of pulse energies from 0.5 to 1.5 J/P at 15 pulses/sec. RESULTS: The results showed a significant linear correlation between the mass loss and pulse energy, and between the mass loss and radiant exposure. Electron microscopy and histology showed that the Ho:YAG ablation resulted in a very sharp and clear border with little charring. Applying 0.01 k.J of total energy at two different settings (1.5 J/p, high power, and 0.5 J/p, low power) at 15 pulses/sec, the cross-sectional area/mm(2) of the ablated bone was measured, using light microscopy and the Scion Image analysis program. The ablated areas were 2.28 +/- 0.87 and 1.16 +/- 0.43 mm(2) at high and low power, respectively (p = 0.008).

The effect of irrigation on peak temperatures in nerve root, dura, and intervertebral disc during laser-assisted foraminoplasty.

BACKGROUND AND OBJECTIVE: The Holmium: YAG (Ho: YAG) laser has been used for the ablation of prolapsed discs but alternative techniques are available, and this application remains controversial. It also has potential for the decompression of nerve roots within narrowed foraminae with the technique of endoscopic laser foraminoplasty. Traditional methods of decompression necessitate a major surgical procedure with potential destabilisation of the lumbar spinal segment. Nevertheless, minimally invasive techniques are attractive only if serious complications can be avoided. This study reports the peak temperatures reached in surrounding tissues with and without saline irrigation. STUDY DESIGN/MATERIALS AND METHODS: Investigation of the hypothesis was carried out in excised sheep lumbar spines. T-type thermocouples were used for the measurement of tissue temperatures during laser ablation of nerve root foraminae. The temperature was assessed in the nerve root, dura mater, and disc space. RESULTS: The Ho: YAG laser was effective in widening the foraminae by approximately 1.5 mm with a total energy of 4.60 kJ. This was statistically significant in both vertical and horizontal directions (P < 0.0003 and P < 0.00005, respectively). The mean temperature of the nerve root, dura, and disc space during the procedure was 44 +/- 3.1 degrees C, 42.8 +/- 4.7 degrees C, and 41 +/- 3.4 degrees C respectively. There were transient high peaks seen in the temperature profiles. Using saline irrigation at 27 ml/minutes these temperatures were reduced to 34.1 +/- 1.8 degrees C (P = 0.0002), 34.9 +/- 1.5 degrees C (P = 0.002), and 37.2 +/- 1.2 degrees C (P < 0.014), for nerve roots, dura, and disc space respectively. CONCLUSIONS: Laser ablation of bone and ligament for nerve root decompression using the Ho: YAG laser may offer substantial advantages, but the risk of serious complication may only be avoided if the technique is combined with saline irrigation.

Geometrical dimensions of the lower lumbar vertebrae--analysis of data from digitised CT images.

The precise dimensions of the lumbar vertebrae and discs are critical for the production of appropriate spinal implants. Unfortunately, existing databases of vertebral and intervertebral dimensions are limited either in accuracy, study population or parameters recorded. The objective of this study is to provide a large and accurate database of lumbar spinal characteristics from 126 digitised computed tomographic (CT) images, reviewed using the Picture Archiving Communication System (PACS) coupled with its internal measuring instrumentation. These CT images were obtained from patients with low back pain attending the spinal clinic at the Hammersmith Hospitals NHS Trust. Measurements of various aspects of vertebral dimensions and geometry were recorded, including vertebral and intervertebral disc height. The results from this study indicated that the depth and width of the vertebral endplate increased from the third to the fifth lumbar vertebra. Anterior vertebral height remained the same from the third to the fifth vertebra, but the posterior vertebral height decreased. Mean disc height in the lower lumbar segments was 11.6 +/- 1.8 mm for the L3/4 disc, 11.3 +/- 2.1 mm for the L4/5, and 10.7 +/- 2.1 mm for the L5/S1 level. The average circumference of the lower endplate of the fourth lumbar vertebra was 141 mm and the average surface area was 1,492 mm2. An increasing pedicle width from a mean of 9.6 +/- 2.2 mm at L3 through to 16.2 +/- 2.8 mm at L5 was noted. A comprehensive database of vertebral and intervertebral dimensions was generated from 378 lumbar vertebrae from 126 patients measured with a precise digital technique. These results are invaluable in establishing an anthropometric model of the human lumbar spine, and provide useful data for anatomical research. In addition this is important information for the scientific planning of spinal surgery and for the design of spinal implants.

Historical note: past, present and future of the antiglobulin test.

This is a review of two invited talks on the antiglobulin reaction on the occasion of the 50th Anniversaries of the International Blood Group Reference Laboratory, now at Bristol, and the National Blood Service, London, and coincidentally the 51st anniversary of the antiglobulin test! The first talk (as specially requested) is a very personal reminiscence of the discovery, with Rob Race and Arthur Mourant, of the antiglobulin test in blood group serology. The second talk traces developments in antiglobulin testing in general immunology using, of course, isotype-specific antiglobulin reagents as and when they became available. Special emphasis was given to: (1) testing for poorly agglutinating bacterial antibodies; (2) special procedures for measuring reaginic (IgE) antibodies to various allergens; (3) the incorporation of an antiglobulin step or stage in many of the routine automated immunoassay procedures; (4) the special experimental procedures in the form of mixed antiglobulin reactions to reveal antibodies to the surface antigens on tissue cells, and, finally, (5) by chemically coupling antiglobulin to red blood cells, a distinctive integrated immunoassay system was developed, enabling reverse passive haemagglutination as an assay for immunoglobulins, rosetting reactions to reveal native IgG receptors on lymphocytes or antibody immunoglobulin reacting with CD marker antigens; this same reagent, namely red-cell-labelled antiglobulin, can be used to detect antibodies reacting with either bacteria or antigens adsorbed on the walls of wells of microtitre plates. The need for improved stabilization and preservation of the antiglobulin-linked red cells to prolong their 'shelf-life' is stressed.

Avascular necrosis of the hip.

Avascular necrosis is a common problem and can be a grossly disabling condition in young patients. Magnetic resonance imaging has revolutionized the diagnosis and assessment of early cases. Core decompression of the femoral head may promote venous drainage and reduce the risk of progressive collapse towards osteoarthritis. However, the authors favour early total joint replacement in patients who are greatly incapacitated.

Fusidic acid in staphylococcal bone and joint infection.

Over 25 years experience with fusidic acid in the treatment of bone and joint infections is reviewed. Fusidic acid, usually given concurrently with another antibiotic, has proved effective in a wide variety of staphylococcal infections, including acute osteomyelitis and septic arthritis. It is a valuable adjunct to surgery in patients with chronic osteomyelitis. Oral therapy is generally well tolerated, apart from gastrointestinal side effects in a small proportion of cases. Use of fusidic acid in other orthopaedic situations is considered in the light of recent information.

Interleukin-2-induced production of interferon-gamma by resting human T cells and large granular lymphocytes: requirement for accessory cell factors, including interleukin-1.

Between 5 and 20% of normal human lymphocytes were found to synthesize interferon-gamma (IFN-gamma) in primary cultures with recombinant interleukin-2 (rIL-2). After 22 hr, IFN-gamma-producing cells included CD5+ T lymphocytes, CD16+ large granular lymphocytes (LGL), and a population of CD5-, CD16- blast cells. Only a small proportion (0-7%) of IFN-gamma-synthesizing cells expressed HLA-DR. The production of IFN-gamma by all rIL-2-responding lymphocyte subsets was shown to require the presence of DR+ accessory cells, probably including nonadherent, esterase-negative monocytes and/or dendritic cells. Accessory cell function in lymphocyte preparations depleted of DR+ cells, or in purified (greater than or equal to 95%) suspensions of LGL, was fully replaced either by addition of 2% autologous, adherent monocytes or by monocyte culture supernatant. The activity of monocyte supernatant was greatly reduced by treatment with antiserum specific for human interleukin-1 beta (IL-1 beta), although a combination of rIL-1 beta and rIL-2 failed to stimulate IFN-gamma production in DR- lymphocytes. These results indicate that rIL-2-induced IFN-gamma synthesis in both T cells and LGL requires the synergistic activity of IL-1, and possibly of one or more other monokines, as yet unidentified.

Red-cell IgM-antibody capture assay for the detection of Mycoplasma pneumoniae-specific IgM.

A red-cell IgM-antibody capture assay has been developed for detecting Mycoplasma pneumoniae-specific IgM, which is based on the adsorption or 'capture' of IgM from patients' sera onto so-called 'inagglutinable' bovine red cells, chemically linked with anti-human mu. When M. pneumoniae antigen is added to the system, the red cells agglutinate in the presence of M. pneumoniae-specific IgM. The test was compared with the mu-capture ELISA described by Wreghitt & Sillis (1985), and was found to give comparable results. The two tests had similar sensitivity and specificity and could detect M. pneumoniae-specific IgM for a similar time (up to 6 months) after proven M. pneumoniae infection. However, the red-cell antibody capture assay is a much more simple and rapid test, taking only 1 h to perform (compared to 24 h for mu-capture ELISA). The red-cell IgM-antibody capture assay is therefore amenable to rapid diagnosis of M. pneumoniae infection and the institution of early appropriate antibiotic therapy.

Measurement of gamma-interferon in culture supernatants of antigen-stimulated lymphocytes from patients with Schistosoma mansoni infections by a reverse passive haemagglutination assay.

An assay for gamma-interferon (IFN gamma) in human lymphocyte culture supernatants, based on reverse passive haemagglutination (RPH) of red cells bearing a monoclonal anti-IFN gamma antibody, was developed and compared with a conventional virus inhibition assay. Test samples comprised supernatants of lymphocytes from patients with Schistosoma mansoni infections, cultured with or without a soluble worm antigen preparation. The two assays gave comparable results, the correlations for individual samples being good. The RPH assay was both specific and sensitive, allowing the detection of IFN gamma at 13 u/ml (1 ng/ml) or less. The advantages of the RPH assay were that it was quick, relatively inexpensive and suitable for testing large numbers of samples. In particular, between-experiment variation was very low, allowing the assay of different samples on different occasions.

Progesterone assay by inhibition of reverse passive haemagglutination.

An assay for the steroid hormone progesterone is described based on the inhibition of the agglutination by progesterone-bovine serum albumin conjugate of red cells coupled with monoclonal antiprogesterone antibody (reverse passive haemagglutination). A low-affinity agglutination system produced the optimal sensitivity, capable of detecting less than 1 ng/ml steroid. This assay has the simplicity and sensitivity for a potential clinical test for placental or corpus luteum function. It also serves as a model for detection of other small ligands (drugs, hormones) by inhibition of reverse passive haemagglutination.

Does 'sugar' permeability reflect macromolecular absorption? A comparison of the gastro-intestinal uptake of lactulose and beta-lactoglobulin in the neonatal guinea pig.

Intestinal closure to cow's milk beta-lactoglobulin occurs within 6 days of birth in the guinea pig. Passive intestinal permeability to lactulose persists through the suckling period. The uptake of small water-soluble markers does not reflect macromolecular absorption, and has no place in the measurement of immunologic protein handling by the gut.

Experimental studies on red cell-based assays for total IgE and allergen-specific IgE.

The potential of red cell-based assays for IgE and allergen-specific IgE has been examined using mouse monoclonal anti-human IgE antibodies and chimaeric human IgE anti-4-hydroxy-3-iodo-5-nitrophenacetyl. Experiments concerned with developing a red cell IgE antibody-capture assay for allergen-specific IgE have pointed to the advantages of presenting the allergen on a second agglutinable red cell.

The detection of heat-aggregated IgG (as a model for immune complexes) by reverse passive haemagglutination using a human monoclonal rheumatoid factor coupled to erythrocytes.

A human monoclonal IgM rheumatoid factor (RF) produced in vitro by an Epstein-Barr virus (EBV)-immortalized cell line was purified by protein A-Sepharose adsorption and coupled by the chromic chloride method to human erythrocytes. The RF-coupled cells were incorporated in reverse passive haemagglutination (RPH) assays to detect immune complexes (IC) using heat-aggregated human IgG as a model system. The sensitivity of the RPH was comparable to an enzyme-linked immunosorbent assay (ELISA) using sheep C1q for the detection of ICs.