Patient-Based Ratio Method for Permanent Zone Donor Area Calculation in Hair Transplant.

 Most common type of hair loss is androgenetic alopecia. Orentreich's donor dominance theory and the definition of safe donor area are the theoretical foundation of modern hair transplantation. In safe donor area no progression of permanent hair loss occurs. Its knowledge is important to prevent loss of transplanted hair. Estimation is not tailored to every patient, also in early stages, the margins are assumed to be free from future hair loss. Our study is an attempt to find and establish a relationship between safe zone dimensions and other standard scalp dimensions, and effectively predict the complete safe zone in early stages of hair loss.  From July to December 2022, the first 100 patients with Norwood IV onwards of hair loss were included. Then, the distance between the vertex and the point of change in occipital hair quality and density was measured, and from this point till occipital protuberance were taken. The ratio between the two was taken. In the next 100 patients of Norwood II to IVa, the applicability of the new ratio to assess the permanent zone was used.  Ratio method takes into account the patient's measurements, that is, permanent zone and total distance from vertex occiput. The ratio range we got is: Permanent zone: total distance from vertex to occiput: 0.43-0.53 Therefore, the permanent zone would be equal to = total distance from vertex to occiput × 0.43-0.53. With the lower limit being the occiput. Over 90% of the patients did not have significant reduction in density of transplanted hair.  The authors suggest the use of this ratio method to determine the dimensions of the permanent zone especially in patients with early grades of hair loss as per the Norwood scale. It is a simple, effective, and easily applicable concept that can ensure long-lasting results in patients undergoing hair transplants.