Titanium Is the Primary Metal Used for Aneurysm Clips
Aneurysm clips are primarily made of titanium alloy due to its superior imaging characteristics, biocompatibility, and mechanical properties compared to other metals. 1, 2
Types of Metals Used in Aneurysm Clips
Current Standard: Titanium Alloy
- Titanium alloy (typically 6 aluminum-4 vanadium-titanium) is the preferred metal for modern aneurysm clips due to significantly reduced artifacts on imaging studies 1, 2
- Titanium clips produce 2-3 times less artifact on CT and MRI compared to cobalt-based alloy clips, allowing better visualization of surrounding brain structures 1
- Titanium is non-ferromagnetic, making it safe for MRI procedures 1
Historical Metal Options
- Cobalt-based alloys (including Elgiloy and Phynox) were commonly used before titanium became standard 3
- Earlier clips used various stainless steel alloys (301,401,402,58, and 17-7 PH) which were found to be unsuitable due to high risk of corrosion 3
- 316MOSS stainless steel was more biocompatible than earlier stainless steel variants but still inferior to titanium 3
Advantages of Titanium Clips
- Biocompatibility: Titanium clips produce only mild gliosis when implanted in the subarachnoid space, similar to cobalt alloy clips 1
- Corrosion resistance: Electron microscopic scans show no evidence of corrosion with titanium implants 1
- Superior imaging: Artifact reduction on CT and MRI by a factor of 2-3 compared to cobalt alloy clips 1, 4
- Mechanical equivalence: Closing forces comparable to conventional clips (151.6-181.8g) 1, 2
- MRI safety: No motion in magnetic fields, unlike some other metals 3
Limitations of Titanium Clips
- Mechanical durability: Closing force may reduce by approximately 10% after 100 repeated openings, compared to no significant changes in cobalt alloy clips 2
- Limited elastic deformation: May not open as wide as cobalt alloy clips, making them less suitable for large broad-based aneurysms 5
- MR angiography limitations: Despite reduced artifacts, titanium clips still produce enough shadow to affect MRA quality for evaluating completeness of aneurysm elimination 5
Clinical Outcomes with Titanium Clips
- Safe and effective in clinical use with no immediate or delayed complications directly related to the clips 4
- Significant improvement in postoperative imaging quality, with average cross-sectional artifact areas of 0.96,1.36, and 1.05 cm² on T1-, T2-, and intermediate-weighted MRI images (compared to 3.13,3.70, and 2.81 cm² with cobalt alloy clips) 4
- Average artifact volumes on gradient echo MR images: 1.8 cm³ for titanium versus 10.1 cm³ for cobalt alloy clips 4
Treatment Considerations
- Complete obliteration of the aneurysm should be the goal whenever possible 6
- For patients with ruptured aneurysms amenable to both endovascular coiling and neurosurgical clipping, endovascular coiling should be considered first 6
- For patients with posterior circulation aneurysms amenable to coiling, coiling is indicated in preference to clipping 6
- Patients under 40 years of age might benefit more from surgical clipping for improved durability and long-term outcomes 6
Follow-up Imaging After Clip Placement
- Imaging after surgical intervention is recommended to document aneurysm obliteration 6
- Cervicocerebral arteriography remains the reference standard for evaluation of treated aneurysms 6
- CTA is useful for surveillance but limited by metallic streak artifacts, though titanium produces less artifact than other metals 6, 1
- MRA can be used for follow-up but has limitations with clip artifacts affecting complete evaluation 6, 5
Titanium aneurysm clips represent the current standard in neurosurgical practice due to their optimal balance of mechanical properties, biocompatibility, and reduced imaging artifacts, making them the metal of choice for aneurysm treatment.