To solve the problem of how to choose the appropriate screw for stereotaxic radio surgery (SRS).

Five hundred and thirty-five patients with brain diseases, admitted to Oncology Department of Xi’an Chang’an Hospital from January 2013 to November 2019 were selected. Each patient needs to collect two sets of data at four fixed points data of the thickness of the plating and the scalp. Eight data were obtained for each patient, the naming rules of the measured data at each site are R_{forehead-scrap}, R_{forehead-plate}, L_{forehead-scrap}, L_{forehead-plate}, L_{occipital-scrap}, L_{occipital-plate}, R_{occipital-scrap}, and R_{occipital-plate}. The difference of the left and right forehead scrap and left and right foreheads, left and right occipital scraps and left and right occipital plates were compared, and whether there is a difference between the same forehead scrap and occipital scrap.

The mean and standard deviation of the thickness of each screw point were: R_{forehead-scrap}=(0.733±0.139)cm, R_{forehead-plate}=(0.337±0.087)cm; L_{forehead-scrap}=(0.719±0.152)cm, L_{forehead-plate}=(0.318±0.079)cm; L_{occipital-scrap}=(1.069±0.208)cm, L_{occipital-plate}=(0.364±0.068)cm; R_{occipital-scrap}=(1.085±0.212)cm, R_{occipital-plate}=(0.341±0.058)cm. There was no significant difference in the left and right forehead scrap, and left and right occipital scrap (P>0.05). There was significant difference in the thickness of the left and right frontal skin, left and right occipital skin, left frontal skin and left occipital skin, right frontal skin and right occipital skin (P<0.05). There was no significant difference between men and women of different genders, and between the groups of >60 years old and ≤60 years old (P>0.05).

For patients treated with gamma knife SRS, implanting screws from the scalp: the forehead length is about 0.8 cm, and the occipital lengh is about 1.1 cm. Implanting screws from the plate the nail length is recommended to be ≤0.3 cm, the scheme is more in line with the individuation principle.