Patient-Based Ratio Method for Permanent Zone Donor Area Calculation in Hair Transplant.
Level 4 - case-series / case-control
Case series establishing and testing an anatomical measurement ratio without a randomized or comparative control group
PubMed 39734366 · doi:10.1055/s-0044-1787655
What was done
Between July and December 2022, investigators measured scalp landmarks in 100 patients with advanced androgenetic alopecia (Norwood stage IV and above) to calculate the ratio between the permanent safe donor zone and the total distance from the vertex to the occipital protuberance. This derived ratio was subsequently applied to estimate the permanent donor zone in a second cohort of 100 patients presenting with earlier hair loss stages (Norwood II to IVa).
What was found
The calculated ratio of permanent zone to total vertex-to-occiput distance ranged from 0.43 to 0.53 (permanent zone = vertex-to-occiput distance × 0.43–0.53, with the occipital protuberance as the lower margin). Over 90% of patients reportedly had no significant reduction in transplanted hair density. Specific numerical follow-up durations, confidence intervals, and precise retention rates were not provided in the abstract.
Why it matters
The ratio provides a simple, individualized anatomical formula to demarcate the safe donor area in patients with early-stage alopecia before clear permanent margins become clinically visible.
Limits
The study is an uncontrolled, single-center case series. The abstract does not report the length of postoperative follow-up, precise criteria for measuring graft density reduction, or patient demographics. Long-term alopecia progression beyond the study period cannot be determined from the reported data.
Cited by
- supports Hair follicles transplanted from areas not prone to androgenetic alopecia retain their resistance to androgen-mediated miniaturization when moved to balding areas.