Location and geometric description of carpal bones in CT images

The carpal regions of ten cadaver extremities were imaged by CT. The images were combined into a 3-dimensional model of the carpus using a technique based on a dynamic programming algorithm to find an optimal estimate of the location of the bone boundaries in the CT images. The resulting set of surface points on each bone was used to compute volumes and principal and antipodal axes for the bones. A spatial coordinate system was established based on the positions of the centroids of three bones in the distal carpal row. The angular orientations of all carpal bones were determined with respect to this system. The principal axes for the same bone among ten wrist specimens proved to be more widely dispersed than the antipodal axes for the same bones. The antipodal axes also correspond more closely to an intuitive notion of the “longest axis” of the bones. We conclude that the antipodal axis is a more reliable and useful measure of bone orientation than the principal axis.     

Load transfer characteristics of the wrist. Part II. Perilunate instability

An experimental model with a static positioning frame, pressure-sensitive film (Fuji), and a microcomputer-based video digitizing system, previously developed by the two senior authors, was used in this study to examine the effects of increasing perilunate instability on the load transfer characteristics of the wrist. These effects included a significant dorsal ulnar shift of the scaphoid centroid with increasing perilunate instability together with a less dramatic palmar ulnar shift of the lunate centroid. Overall, the scaphoid contact area was found to decrease as the stage of perilunate instability increased, even in ulnar deviation and/or extension, which in the normal wrist was found to be the positions that had the greatest scaphoid contact area. Average pressures in the high pressure zones were found to significantly increase in wrists with a stage III instability compared with normal wrists. An increase in the intercentroid (scaphoid/lunate) distance was most evident with the wrist in 20 degrees extension, neutral radioulnar deviation, and 90 degrees supination.     

Preoperative methicillin‐resistant Staphylococcus aureus (MRSA) screening: An effective method to control MRSA infections on elective orthopaedics wards

Background: Methicillin‐resistant Staphylococcus aureus (MRSA) infections continue to increase in UK hospitals despite the introduction of various control measures. These infections have serious clinical and economic implications, particularly in relation to elective orthopaedic surgery. Methods: A prospective study was performed from August 2003 to July 2004 to assess the effect of preadmission screening and ‘ring fencing’ of beds on the incidence of infection in an elective orthopaedics unit. Results: The preoperative incidence of MRSA colonization was 2.25% and 53% of these patients had at least one risk factor. There were no postoperative MRSA infections in the ring‐fenced orthopaedic unit. Conclusions: Preoperative screening and ring fencing reduced the MRSA incidence to zero in the operated patients. Mechanisms need to be developed where screening and isolation of MRSA cases can be performed in most, if not all, hospital admissions.     

Effect of long-term use of Norplant implants on haemostatic function.

This study describes the effects of Norplant on haemostatic function after 5 years of use in 97 women. There was a decrease in vitamin-K dependent Factors II, V, VII and reduction in fibrinolytic activity at 2 and 4 years of use. Increased platelet numbers and accelerated platelet aggregation were found throughout the 5 years of Norplant use, whilst raised alpha 2-Macroglobulin (a2-M) and antithrombin III (ATIII) antigen level were observed for up to 4 years of use. Prolonged Norplant use does not appear to activate the coagulation system and does not enhance a state of hypercoagulation.