Techniques for the Application of Stereotactic Head Frames Based on a 25-Year Experience

Abstract

The use of skull fixed stereotactic head frames remains an integral part of neurosurgical practice. Methods for the positioning, anesthesia, and fixation have been described in various publications. The authors describe the steps used currently that reflect a 25-year experience with stereotactic frame application. Photographs were obtained throughout the set-up and frame application process. The step-by-step methods were described with accompanying figures. Consent was obtained from that patient to allow for photographs throughout the frame application process. Consent was also obtained from a separate patient for videotaping the entire application process. Descriptive tags are embedded in the video to assist with the instruction of the senior author's (MWM) methods. The senior author has used the described method in over 1,000 cases. A recent analysis of the patient pain experience has been reported and is well tolerated. Supplemental devices beyond the manufacturers' standard equipment have been employed or developed: ethyl chloride spray, angled front posts, frame positioner, and torque wrenches. There have been no shunt perforations, no cranial vault penetrations, one titanium mesh cranioplasty deformation, three pin site infections (3 patients; 4,000 pin sites; 0.075%), and one thermal injury (0.025%). Stereotactic head frame application remains an important part of neurosurgical practice. The steps in application employed here after a 25-year experience appear to make the procedure well tolerated by patients. The authors hope this instructional article will be of value to new users who practice stereotactic radiosurgery, frame-based biopsy, depth electrode placement, or deep brain stimulator implantation.

Keywords: gamma knife; head frame; stereotactic.

Figure 1. Equipment for frame application.

Frame positioner (A), frame pin/screw set (B), local anesthetic (C), ruler (D), marking pen (E), ethyl chloride spray (F), torque wrenches (G), Leksell frame (H), pin/screw wrenches (I).

Figure 2. Gebauer’s ethyl chloride® instant topical anesthetic (Gebauer Company, Cleveland, OH, USA).

Figure 3. The frame holder is positioned on top of the patient’s head with gauze padding for initial frame positioning.

Figure 4. Injection sites are sprayed with ethyl chloride to anesthetize the skin.

Figure 5. Each pin site is injected with 2 ml of local anesthetic.

Figure 6. Distance from skin to outer edge of post is measured to estimate pin/screw length.

Figure 7. Pins are manually placed on the diagonal.

Figure 8. Pins are tightened on the diagonal with thumb and index finger grip.

Figure 9. The wrench is held with the thumb and index finger to avoid over-tightening the screws prior to the final torque.

Figure 10. Final screw tightening is performed with torque wrenches on the diagonal to 4 inch-pounds of torque per screw.

Figure 11. Deformation of titanium mesh cranioplasty caused by pin application. This injury caused a cosmetic deformity that required revision cranioplasty.