A New Universal Follicular Unit Excision Classification System for Hair Transplantation Difficulty and Patient Outcome

Introduction: The difficulty of the follicular unit excision (FUE) hair transplantation procedure is currently attributed to hair curliness and subsurface angulation. Patients possessing the curliest hair shafts are considered the most challenging. Consequently, patients with these features are often denied FUE. However, this practice does not consider intrapatient variation in the graft attrition rate and the rates themselves, which are frequently low in very curly hair where the skin firmness/thickness is average. To better aid practitioners in predicting FUE performance, we have developed a new scoring system (the Sanusi FUE Score Scale [SFS Scale]) based on two major donor variables (hair and skin characteristics). Material and Method: The scale assigns scores to each of three hair subtypes (straight-wavy, curly, and coily-kinky) and each of three skin subtypes (thick/firm, soft/thin, and medium thickness/firmness). The scores were weighted based on the assessment of 13 experienced FUE practitioners from around the globe, who were asked to score each of the three skin and hair characteristics for their contribution to FUE difficulty. Results: On the contribution of skin characteristics to FUE difficulty, 12/13 (92%) practitioners assigned the highest (most difficult) score to thick/firm skin, with medium skin thickness/firmness being the least challenging. The same percentage of practitioners gave the highest difficulty score to coiled-kinky hair subtypes regarding the contribution of hair characteristics to FUE difficulty. All agreed that straight-wavy hair presents the least challenge to FUE performance. Tallying the scores of the skin and hair variables generates a final score range of 2-9, which is associated with five grades/classes of challenge in the FUE procedure, influencing the need for a specialized skill/nuanced approach or equipment. Conclusion: We developed a universal FUE donor scoring scale that accounts for the diversity of human hair and skin types. Further evaluation to determine the validity of this new classification system in predicting and grading FUE difficulty and patient outcomes is warranted.