Aim:Craniosynostosis is a clinical condition that goes with cranial deformities caused by early ossification of fibrous tissue at the suture line. The rate of metopic synostosis has been increasing in recent years. Our aim in this article is to mathematically present the results of endoscopic assisted surgery in the treatment of metopic synostosis.Material and Methods:We present a follow-up of the stages of treatment of 43 patients with metopic synostosis who underwent surgery in a multicenter retrospective study between 2018 and 2021. We developed the formula D3/((D1+D2)/2) based on the theory of “The Angle of a Triangle Opposite The Longest Side is the Largest Angle”. And we called this method \'Metopic Angle Proportion (MAP)’. Paired samples T-test was performed for statistical results. P value <0.05 was considered statistically significant.Results:According to the MAP method; measurements for frontal enlargement, mean pretreatment length D1: 34,57 mm, D2: 34,81 mm, D3: 60,46 mm, and the end of treatment as D1: 37,88 mm, D2: 38,19 mm, D3: 71,09 mm. We perfomed the formula D3/((D1+D2)/2). While this rate was 1.74 before treatment, it increased to 1.87 after treatment. As a result of statistical analysis, it was also found to be significant (p≤0.05).Conclusion:Studies have shown that the rate of trigonocephaly increases between synostoses. This shows that the treatment rate is increasing. As a treatment option , open vault surgery is an older and more familiar technique. However, this method has disadvantages such as long surgical time, higher blood loss, the need for intensive care in the postoperative period, and the surgeon\'s dependence on experience and 3D thinking skills. However, Endoscopic assisted surgery offers a more comfortable surgery and better results.Endoscopy-assisted suturectomy can be applied in many health centres because it is safe, easy and cheaper