Current methods for brow fixation: are they safe?

BACKGROUND

No single technique for fixation of the scalp after forehead-lift is universally accepted. Complications such as alopecia, loss of elevation, implant palpability, paresthesia, and dural injury are possible with the variety of techniques used currently. This anatomic study was designed to evaluate the thickness of the calvarium at selected points used in brow fixation. The depth of cranial penetration necessary for currently used techniques is measured and compared.

METHODS

In a study of 14 fresh adult cadavers, calvarial thickness was measured at selected points (A-F) used in various brow-lifting procedures. This was accomplished by drilling holes in selected points and using a depth gauge to measure thickness. Immediately adjacent to selected points, the cranium is prepared for brow fixation using the following techniques: cortical tunnels, 2.0-mm screw fixation (10, 12, and 14 mm), the Mitek 2.0-mm Quickanchor screw, and the Endotine 3.5 Forehead Device. The depths required for adequate fixation and the potential for cranial penetration through the inner table with all the standard techniques are compared.

RESULTS

Depth analysis by mean values showed that sites posterior to the coronal suture (points C-F) were thickest. Depth analysis of sites stratified by gender showed that mean values for the thickness of female skulls were greater than those for males. A review of fixation methods found that cortical tunnels at 45 degrees angles never penetrated the inner table in any of the 14 skulls. Mitek screws never penetrated the inner table, and one Endotine post penetrated the inner table on the left side of one cadaver skull. After placement of 10-, 12-, and 14-mm miniscrews at each of the sites, it was found that three penetrated the inner table. The penetrations all were at far lateral sites, posterior to the coronal suture.

CONCLUSION

Variation in skull thickness exists among cadaver specimens at different sites on the skull. In this study, thickness increased medially and posteriorly. Women tended to have thicker skulls than men, and age was not a major variable. This is consistent with findings in previous work. Given the unpublished reports of inner table penetration, with cerebrospinal fluid leak after invasive brow fixation, it behooves the surgeon to keep in mind the anatomy of the calvarium and its nuances.