Optimal Number of Fixation Pins for Dedicated Mini Jig Cutting Guides During Navigated Total Knee Arthroplasty

Purpose: The optimal number of fixation pins for minimally invasive cutting guides in computer-navigated arthroplasty has not been determined. The authors hypothesized that more fixation pins will lead to greater mechanical stability and more accurate resections. Materials and Method: 12 bovine knee joints were divided into three groups with differing numbers of fixation pins. The ASM [Stryker] knee navigation system was utilized to perform resections, and accuracy of alignment and posterior slope was measured. Comparison was performed between the groups to calculate average differences between predicted and actual resection with differing number of pins. Results: The difference between actual and predicted values showed a trend toward diminishing with a greater number of fixation pins. The mean difference in coronal alignment of predicted versus actual resection was 0.75° for two fixation pins, 0.5° for three pins and 1° for four fixation pins. Similarly, the difference between posterior slope was 2.75°, 2°, and 1°, respectively. Conclusion: This study reveals a trend toward greater accuracy of resections with more fixation pins. Further investigation may be beneficial.     

The emergency department: an appropriate referral rate for radiography

AIM: To evaluate the hypothesis that where there is good clinical practice in an emergency department (ED), there is a low uptake of plain radiography. MATERIALS AND METHODS: Emergency notes and radiography records were reviewed over one week in January 1999, to determine the rate of radiography of first time attenders at the North Staffordshire NHS Trust. The clinical appropriateness of the imaging was assessed by pairs of radiology specialist registrars and casualty physicians. They judged the appropriateness of the imaging by the 1998 Royal College of Radiologists (RCR) guidelines and/or their clinical judgement, by consensus. Where there was no consensus or the data appeared incomplete, the radiology and ED consultant reviewed the notes. RESULTS: A total of 1615 notes were found out of 1643 (98%). Of these, 147 (9%) return attenders were excluded and 32 patients left without being seen. The number of first time attenders was 1436 (87%), of whom 637 (44%) were radiographed; 95% of these radiography examinations were appropriate and 5% were inappropriate. Of the first time attenders who were not radiographed the decision was appropriate in 95% of cases, and inappropriate for 5%, i.e. 5% of those who had no radiography, should have been X-rayed. There were no disagreements between RCR guidelines and the clinical judgements, but in 16% there were no suitable RCR guidelines. Junior doctors were not always able to find the relevant RCR guideline (relevant clinical guideline found in 73% of cases) in the guideline book, compared to the consultants (relevant clinical guideline found in 84% of cases). CONCLUSION: The application of the RCR guidelines is taken as representing good clinical practice in determining when to refer a patient for radiography. Based on this assumption, a referral rate for radiography of 44% of first time attenders was found to be appropriate. This referral rate can be taken as a benchmark. A benchmark is necessary in order to allow departments to make a local assessment as to whether their local referral rate is likely to be too high or too low. Richards, P. J. et al. (2002). Clinical Radiology57, 753-758.