Establishing an optimal trajectory for calcaneotibial K-wire fixation in emergent treatment of unstable ankle fractures.

OBJECTIVE: In unstable ankle fractures the associated soft tissue damage can be a therapeutic challenge. The aim of this study was to optimize planning of minimally invasive stabilization of ankle fractures by calcaneotibial transfixation, which is a demanding technique due to the complex hind foot anatomy. METHODS: In a retrospective radiographic analysis the angles and dimensions of a safe drill tunnel for calcaneotibial K-wire insertion were defined on standard radiographs of the ankle joint. 165 lateral weight-bearing radiographs (77 right; 88 left) and 147 (80 right; 67 left) mortise views of 186 (90 right; 96 left) uninjured feet from 123 patients (74 women (114 feet); 49 men (72 feet)) were included in this study. The average patient age was 49 (range, 13-85) years. Inter- and intra-observer reliability was evaluated on 20 randomized radiographs that were analyzed in a default set, three times, by two different examiners on three different days. RESULTS: In the lateral view the drilling tunnel was orientated at 59.4° to the plantar plane with a maximum proximal variance of 7.1 image-mm. Distal variance cannot be tolerated since an ankle joint injury would ensue. In the mortise view the drill tunnel was directed with a mean angle of 18.4° to the distal tibial articular surface. At most a mean of 11° fibular- and 13.4° tibial- expansion can be tolerated. Intra- and inter-observer reliability was higher for the angles than for the drill corridors. CONCLUSION: The three-dimensional (3D) orientation for safe K-wire placement for calcaneotibial transfixation should adhere to the drill tunnels established in this study.

The influence of metal artifacts on navigation and the reduction of artifacts by the use of polyether-ether-ketone.

Registration is a crucial step in navigation assisted surgery. When performing anatomical pair-point registration, there are several potential sources of error, including inadequate data acquisition, improper segmentation, and distortion resulting from metal artifacts. The aim of this study was to evaluate the influence of metal artifacts on the precision of Iso-C(3D) and fluoroscopy-based navigation, and to assess any changes in precision from the use of a newly developed Schanz screw composed of polyether-ether-ketone (PEEK OPTIMA). A T-shaped test specimen was manufactured from synthetic bone material. It was then scanned with a Siremobil Iso-C(3D) while different types of implant were present in the specimen. Five Iso-C(3D) scans were acquired: one with a steel Schanz screw in the specimen, one with a titanium screw, one with a PEEK screw, one with a 5-hole plate, and one with no screw or plate present. The registration was analyzed by "reverse verification" with a pointer in a purpose-built, manipulable 3D holder. All experiments were then repeated using fluoroscopy-based navigation. Increasing presence of metal in the scan area resulted in an increase in mean error (0.55 mm with the steel Schanz screw, 0.7 mm with the 5-hole plate). Artifacts resulting from the titanium Schanz screw were less than those caused by the stainless steel Schanz screw. While this study demonstrates that metallic artifacts do have an influence on the precision of Iso-C(3D) navigation, such artifacts were not found to be a factor when performing fluoroscopy-based navigation.

Modulation of base hydroxylation by bile acids and salicylates in a model of human colonic mucosal DNA: putative implications in colonic cancer.

Bile acids are believed to be involved in the formation of colonic cancer, and 5-aminosalicylic acid and other salicylates may have a protective role. The precise mechanisms of both actions are not known, but modifications (stimulation or inhibition) of basal or oxygen-radical induced DNA base hydroxylation as potential early events in tumor formation by these compounds may be involved in such actions. We, therefore, investigated whether: (1) bile acids in concentrations as they occur systemically or intraluminally are able to enhance basal or OH*-radical-stimulated base hydroxylation in DNA from calf thymus; (2) 5-aminosalicylic acid, its main intestinal metabolite N-acetyl-aminosalicylic acid and salicylate, the main aspirin metabolite, are able to inhibit this hydroxylation; and (3) DNA from calf thymus can be used as a model by comparing its base composition and hydroxylation with DNA from normal human colonic mucosa. We found an enhancement of the OH*-radical-induced DNA hydroxylation especially 8-OH adenine with 214.0%. On the other hand 5-ASA, N-acetyl-ASA, and salicylate showed a concentration-dependent inhibition of OH*-stimulated hydroxylation with IC50 between 0.04 +/- 0.01 mM (X +/- SD) and 1.3 +/- 0.1 mM. No effects were observed on basal hydroxylation. Electron spin resonance spectroscopy studies showed reduction of the corresponding base signals pointing to a scavenger mechanism. In DNA isolated from normal human colonic mucosa (N = 7) a similar base distribution was found as in calf thymus; hydroxylation was < or = 1.0% in both systems. From our results we conclude that DNA from calf thymus may serve as a model for human colonic mucosal DNA and that one of the carcinogenic actions of bile acids may be enhancement of oxygen-radical-induced DNA base hydroxylation, especially 8-OH adenine. The absence of effects under unstimulated conditions supports their role as cocarcinogens. The concentration-dependent inhibition of OH*-stimulated DNA hydroxylation by 5-ASA, salicylate, and N-acetyl-ASA may be a possible mechanism of chemoprevention.