A variable-force microvascular clip

Assessment of the clipping efficacy of intracranial aneurysms: analysis of the employed methodology in relation to case difficulty

OBJECTIVE

To assess intracranial aneurysms clipping efficacy (CE) employing different angiographic techniques in relation to the case difficulty.

METHOD

In the past 6 years, 152 patients harboring 179 aneurysms who underwent surgical clipping in our department were angiographically examined to confirm aneurysm occlusion. Intraoperative angiography (IA), post-operative conventional (PCA) and three-dimensional angiography were single or sequentially performed based on the surgeon's concern about case difficulty. The percentage of visualized angiographic abnormalities (PVAA) assessing CE and their impact on corrective treatment were retrospectively analysed.

RESULTS

The PVAA of IA was 67.8% (19 of 28 aneurysms). Eighteen of them (eight aneurysm remnants, four parent vessel stenosis, two distal branch occlusions and five clip slippage phenomena) underwent immediate corrective treatment (clip reposition in 11 cases, complementary clipping in three cases and combined treatment in four cases). The impact on corrective treatment was 94.7%. The PVAA of PCA was 18.4% (33 of 179 aneurysms). Fifteen patients presented aneurysm remnants, six presented parent vessel stenosis, five presented distal branch occlusions and seven presented clip slippage phenomena. The impact of this technique on corrective treatment was 15.1% (five of 33 angiographic abnormalities). In only one case, PCA demonstrated an aneurysm remnant which was missed on IA. Twenty patients were additionally examined with three-dimensional angiography. The impact on corrective treatment of three-dimensional angiography was 25% (five of 20 examined patients with angiographic abnormalities).

CONCLUSION

In pre-selected difficult cases, IA provides high PVAA and increased impact on corrective treatment. In non-selected patients, PCA shows low PVAA and reduced impact on corrective treatment. The complementary assessment with multiplanar three-dimensional angiography increases the impact on corrective treatment and facilitates decisions about the final case management.

Experimental animal studies of clip-induced microvascular trauma

This study was designed to evaluate microvascular clip potential for causing changes in vessel-wall tissue and the extent to which this potential is influenced by features of the clip. Light and scanning electron microscopy were used to examine vessel-wall changes after temporary clip occlusion. Vessel patency is shown to be influenced by anastomosis and clip site, changes in occlusion force due to material fatigue are described, and novel clip features to reduce vessel trauma are proposed. Evaluation of mechanical clip properties showed that material fatigue does not lead to relevant loss of precision in alpha-type clips. While the modified clip designed to reduce trauma cannot abolish trauma altogether, it significantly reduces the associated changes and hence the risk of thrombosis. Arteries were more sensitive than veins to clip-induced trauma, with increased occlusion force producing more severe damage than increased clipping time. Maximal changes were seen in the tunica media. These results indicate the paramount importance of applying modest clip pressure commensurate with the requirements of microvascular Surgery.

Risk of intraoperative aneurysm clip slippage: a new experience with titanium clips

Slippage of an aneurysm clip as a result of insufficient clip-closing force cannot be predicted, even when using force-testing devices. Descriptions of intraoperative clip slippages are rarely found in the literature. The authors summarize four unusual cases in which titanium aneurysm clips slipped by a scissorslike mechanism during surgery. They analyze the possible factors implicated in such a dangerous situation and discuss corrective choices.

A new microclip for vascular occlusion. Technical note

A new microclip for use on blood vessels 300 mu to 1 mm in diameter is described. This clip is suitable for either temporary or permanent occlusion and has been used in experimental applications. Potential clinical applications are described.