The role of needle tip position on the accuracy of diagnostic selective nerve root blocks in spinal deformity.

PURPOSE: The specificity of a selective nerve root block (SNRB) is dependant on isolating only the required nerve root whilst avoiding injectate flow to traversing nerves. Needle tip position is therefore crucial. Nerve root blocks (SNRBs) in the presence of deformity can be particularly technically challenging to perform. The aims of this study were to document the relationship of needle tip position and SNRB accuracy in patients with and without spinal deformity. METHODS: Over an 8-month period, all SNRBs performed by one spinal surgeon were included. Patients with radiographic evidence of spinal deformity were analysed separately and their lumbar deformity graded using the Schwab grading system. Needle tip position in relation to the superior pedicle and flow of contrast was documented. RESULTS: 76 patients received 85 injections without deformity, 26 patients with deformity underwent 30 SNRBs. In the normal spinal alignment group, there was on overall accuracy of 70.1% regardless of needle tip position, which improved to 91.8% for a lateral needle tip position (P < 0.001). In patients with deformity, the overall accuracy was significantly lower irrespective of needle tip position 36 versus 70%, respectively (P < 0.0019). CONCLUSIONS: Selective nerve root blocks are accurate in patients without deformity where a needle tip placement lateral to the middle third of the pedicle is achieved. The presence of spinal deformity significantly reduces the accuracy of SNRBs with a higher chance of epidural infiltration.

Outcome of Charnley total hip replacement across a single health region in England. The results at ten years from a regional arthroplasty register.

Using the Trent regional arthroplasty register, we analysed the survival at ten years of 1198 consecutive Charnley total hip replacements carried out across a single health region of the United Kingdom in 1990. At ten years, information regarding outcome was available for 1001 hips (83.6%). The crude revision rate was 6.2% (62 of 1001) and the cumulative survival rate with revision of the components as an end-point was 93.1%. At five years, a review of this series of patients identified gross radiological failure in 25 total hip replacements which had previously been unrecognised. At ten years the outcome was known for 18 of these 25 patients (72%), of whom 13 had not undergone revision. This is the first study to assess the survival at ten years for the primary Charnley total hip replacement performed in a broad cross-section of hospitals in the United Kingdom, as opposed to specialist centres. Our results highlight the importance of the arthroplasty register in identifying the long-term outcome of hip prostheses.

Relationship between outcome and annual surgical experience for the charnley total hip replacement. Results from a regional hip register.

Using a regional arthroplasty register, we assessed the outcome, at five years, of 1198 primary Charnley total hip replacements (THRs) undertaken across a single health region in England in 1990. An independent clinical and radiological assessment was completed for 497 operations, carried out in 18 different hospitals, under the care of 56 consultants and by differing grades of surgeon. The overall number of failures in this group was 44 (8.9%). We found that the risk of failure in patients operated on by a consultant whose firm carried out 60 or more THRs in 1990 was 25% of that of patients under the care of a consultant whose firm undertook less than 30, adjusting for a number of patient, surgeon and hospital characteristics (16% v 4%; p < 0.001 for linear trend). Our study shows that the early outcome of hip replacement surgery varies with the number of replacements undertaken by the consultant firm. A national arthroplasty register would be a convenient source for such data.

Radiological features predictive of aseptic loosening in cemented Charnley femoral stems.

The radiological features of the cement mantle around total hip replacements (THRs) have been used to assess aseptic loosening. In this case-control study we investigated the risk of failure of THR as predictable by a range of such features using data from patients recruited to the Trent Regional Arthroplasty Study (TRAS). An independent radiological assessment was undertaken on Charnley THRs with aseptic loosening within five years of surgery and on a control group from the TRAS database. Chi-squared tests were used to test the probability of obtaining the observed data by chance, and odds ratios were calculated to estimate the strength of association for different features. Several features were associated with a clinically important increase (>twofold) in the risk of loosening, which was statistically significant for four features (p < 0.01). Inadequate cementation (Barrack C and D grades) was the most significant feature, with an estimated odds ratio of 9.5 (95% confidence interval 3.2 to 28.4, p < 0.0001) for failure.

The Trent regional arthroplasty study. Experiences with a hip register.

We have assessed the usefulness of a regional hip register in the assessment of the outcome of primary total hip replacement (THR). Over 97% of THRs performed in the Trent region in 1990 were captured onto the register and the inaccuracies recorded were less than 1.8%. In an independent assessment of 2111 patients five years after THR, 85.9% of those available for assessment responded, and 66.8% agreed to an assessment. The cost of this independent assessment at five years, utilising a regional hip register, was approximately l50 per implant. This is a reasonable outlay to identify problems early. Some form of registration and outcome assessment should be performed on a national level.

Preliminary findings from the National Pre-ESRD Education Initiative.

Regardless of age or race, more patients preferred peritoneal dialysis (PD) than would be expected from the current ratio of patients treated with PD in the U.S. The percent of patients choosing PD seems to be largely influenced by the scope of information they receive prior to therapy initiation. In the absence of thorough treatment option education, a significant number of patients may be assigned a therapy when, in reality, they would have selected an alternative option. There is a need to further understand the correlation between a practice's PD utilization rate and the extent to which patients are given dialysis treatment options.

Outcome of Charnley total hip replacement across a single health region in England: the results at five years from a regional hip register.

Using a regional arthroplasty register we assessed the outcome at five years of 1198 primary Charnley total hip replacements (THRs) carried out in 1152 patients across a single UK health region in 1990. Information regarding outcome was available for 1080 hips (90%) and 499 had an independent clinical and radiological assessment. By five years the known rate of aseptic loosening was 2.3%, of deep infection 1.4%, of dislocation 5.0% and of revision 3.2%. The radiological assessment of 499 THRs revealed gross failure in a further 5.2%, which had been previously unrecognised. The combined rate of failure of nearly 9% is higher than those published from specialist centres and surgeons, but is probably more representative of the norm. Our study supports the need for a national register and surveillance of THRs. It emphasises that all implants should be followed, and suggests that the results of such surgery, when performed in the general setting, may not be as good as expected.

Current practice in primary total hip replacement: results from the National Hip Replacement Outcome Project.

As part of the National Study of Primary Hip Replacement Outcome, 402 consultant orthopaedic surgeons from three regions were contacted by postal questionnaire which covered all aspects of total hip replacement (THR). There was a 70% response rate of which 71 did not perform hip surgery, a further 33 refused to take part, leaving 181 valid responses. Preoperative assessment clinics were used by 89% of surgeons, but anaesthetists and rehabilitation services were rarely involved at this stage. Of respondents, 99% used routine thromboprophylaxis, with 79% using a combination of mechanical and chemical methods. Of surgeons, 84% routinely used stockings, whereas 95.5% used chemical prophylaxis, 63% employed low molecular weight heparins. Theatre facilities were shared with other surgical specialties by 6% of surgeons and 18% regularly used body exhaust suits for THR. Antibiotic loaded cement was used by 69% of surgeons, the majority (65%) used a single brand of normal viscosity cement with 9% using reduced viscosity formulations. Modern cementing techniques were commonly used at least in part, 87% used a cement gun and 94% a cement restrictor for femoral cementing. On the acetabulum, 47% pressurised the cement. In all, 36 different femoral stems and 35 acetabular cups were in routine use, but the majority of surgeons (55%) used Charnley type prostheses. Of the surgeons, 57% performed only cemented THR, while 3% exclusively used uncemented THR. Of consultants, 21% followed up their patients to 5 years, the majority discharge patients within the first year. Of concern is a large proportion of surgeons using low molecular weight heparins despite a lack of evidence with regard to reducing fatal pulmonary embolism, and also the small number of surgeons using prostheses of unproven value. Third generation cementing techniques have yet to be fully adopted. The introduction of a national hip register could help to resolve some of these issues.

Autism and maternally derived aberrations of chromosome 15q.

Of the chronic mental disabilities of childhood, autism is causally least well understood. The former view that autism was rooted in exposure to humorless and perfectionistic parenting has given way to the notion that genetic influences are dominant underlying factors. Still, identification of specific heritable factors has been slow with causes identified in only a few cases in unselected series. A broad search for genetic and environmental influences that cause or predispose to autism is the major thrust of the South Carolina Autism Project. Among the first 100 cases enrolled in the project, abnormalities of chromosome 15 have emerged as the single most common cause. The four abnormalities identified include deletions and duplications of proximal 15q. Other chromosome aberrations seen in single cases include a balanced 13;16 translocation, a pericentric inversion 12, a deletion of 20p, and a ring 7. Candidate genes involved in the 15q region affected by duplication and deletion include the ubiquitin-protein ligase (UBE3A) gene responsible for Angelman syndrome and genes for three GABA(A) receptor subunits. In all cases, the deletions or duplications occurred on the chromosome inherited from the mother.

The form of the human dental arch.

The human dental arch form is shown to be accurately represented mathematically by the beta function. The average correlation coefficient between measured arch-shape data and the mathematical arch shape, expressed by the beta function, is 0.98 with a standard deviation of 0.02. Forty sets of casts--15 Class I, 16 Class II, and 9 Class III--were examined. A precision machine tool device was used to record the X-, Y-, and Z-coordinates of selected dental landmarks on all casts to 0.001 mm accuracy. The coordinates were processed through a computer curve-fitting program. The Class III mandibular arches had smaller arch depth and greater arch width (beginning in the premolar area) than the Class I arches. The Class II mandibular arches exhibited generalized reduced arch width and depth compared with the Class I arches. Maxillary arch depths were similar in all three groups. However, the Class III maxillary arch widths were greater from the lateral incisor-canine area distally compared with the Class I maxillary arch, and the Class II maxillary arch form was narrower than the Class I arch form from the lateral incisor-canine area distally. The beta function more accurately described the dental arch form than representations previously reported.

Mortality and fatal pulmonary embolism after primary total hip replacement. Results from a regional hip register.

We calculated the rates for perioperative mortality and fatal pulmonary embolism (PE) after primary total hip replacement in a single UK health region, using a regional arthroplasty register and the tracing service of the Office of National Statistics. During 1990, there were 2111 consecutive primary replacements in 2090 separate procedures. Within 42 days of operation a total of 19 patients had died (0.91%, 95% CI 0.55 to 1.42). Postmortem examination showed that four deaths (0.19%, 95% CI 0.05 to 0.49) were definitely due to PE. The overall perioperative mortality and fatal PE rates are low and in our study did not appear to be altered by the use of chemical thromboprophylaxis (perioperative mortality rate: one-tailed Fisher's exact test, p = 0.39; fatal PE rate: one-tailed Fisher's exact test, p = 0.56). The routine use of chemical thromboprophylaxis for primary THR is still controversial. The issue should be addressed by an appropriate randomised, prospective study using overall mortality and fatal PE rate as the main outcome measures, but the feasibility of such a study is questioned.

Models of the human brain and the surrounding media: their influence on the reliability of source localization.

This article is a review of the evolution of models of the head as used in dipole source localization. Models fall into two classes: those that can be expressed in simple analytic form, such as the homogeneous sphere or spherical three-shell models, or those that can only be solved by numerical methods, such as the finite element approach. The latter models always involve heavy procedural and computational burdens. The trend over the last decade has been to use these more advanced models to estimate the error that would be incurred if one of the simpler spherical models were used instead for dipole source localization. An estimate is presented of the magnitudes of the random and systematic errors of localization that may be expected when using these methods.

Dependence of Panum's fusional area on local retinal stimulation.

The range of fusion in the human binocular vision system has been shown by many research groups to be capable of extension. Although each of these research groups tested the extension of fusion under different conditions, the majority agreed that an extension of fusion is possible, and most have noted a variety of variables that contribute to the phenomenon. The extension of fusion may be interpreted in at least two ways. The first is that the range over which fusion is possible is enlarged, and the second is that the range is shifted. Therefore a study of human binocular fusional ranges was performed to clarify the nature of the extension of Panum's fusional area. The following results were obtained: (1) A shift of the fusional area occurs when one of a pair of fused retinally stabilized images is moved into disparate locations on the retinas. Results for one observer demonstrate a corresponding small enlargement of the fusional area. Thus the extension of the fusional area not only involves the recruitment of retinal locations into the fusional area that are not normally in the area but also involves the loss from the fusional area of certain retinal locations that are normally within it. (2) A continually present stimulus fuses over a wider range with a flashed stimulus than with another continually present stimulus.

Hysteresis in human binocular fusion: temporalward and nasalward ranges.

Fender and Julesz [J. Opt. Soc. Am. 57, 819 (1967)] moved pairs of retinally stabilized images across the temporalward visual fields and found significant differences between the disparities that elicited fusion and the disparities at which fusion was lost. They recognized this phenomenon as an example of hysteresis. In the work reported in this paper, binocular retinally stabilized images of vertical dark bars on white backgrounds were moved into horizontal disparity in both the nasalward and the temporalward directions. The limits of Panum's fusional area and the hysteresis demonstrated by these limits were measured for two observers. The following results were obtained: (1) the nasalward limits of Panum's fusional area and the hysteresis demonstrated by the nasalward limits do not differ significantly from the temporalward limits and the hysteresis demonstrated by the temporalward limits; (2) the limits of Panum's fusional area and the hysteresis demonstrated by these limits are not significantly different if one stimulus moves across each retina or if one stimulus is held still on one retina and the other stimulus is moved across the other retina; (3) the use of nonstabilized cross hairs for fixation decreases the hysteresis; and (4) the full hysteresis effect can be elicited with a rate of change of disparity of 2 arcmin/sec.