The thickness of skull at the halo pin insertion site.

STUDY DESIGN

The thickness of 415 skulls of Thai population was measured at the areas where halo pins are placed.

OBJECTIVE

Analysis of skull thickness at the area of halo pin insertion site.

SUMMARY OF BACKGROUND DATA

Halo orthosis is a device used for providing stable fixation of instability of cervical spine injury. Although this device can be applied quickly and safely, complications do occur. While clinical experiences have informed us that cranial bone thickness varies with age.

METHODS

Coronal computerized tomography scans of 415 heads of patients who had no head injury, skull fracture, or craniofacial abnormalities were reviewed. All scans were performed with a Philips CX/Q. The patients' ages were between 15 days and 89 years. Measurements were taken directly from the computer console, using the measure mode function. These measurements were obtained in millimeters at the locations where halo pins would normally be placed. Statistical analyses within and between all age groups were performed using analysis of variance tests.

RESULTS

The skull thickness increased with age at all sites measured. The average thickness of skull at the anterior midline varied from 5.62 mm (0-9 years) to 7.42 mm (80-89 years). The average thickness of the anterolateral was from 5.52 to 8.54 mm, and the average thickness of the posterolateral was from 5.59 to 8.86 mm.

CONCLUSION

The thickness of skull at the halo pin insertion site gradually increases with age. Our study reveals that the thickness of skull reaches a steady peak in third to sixth decades. The thickness of skull at the anterior midline can be predicted by a simple linear regression equation: A = 7.302 + 0.014*age.