Dr. Andrew Jacono's Research into What Actually Creates a Defined Jawline

Patients ask for a sharper jawline more often than almost any other single result, and

most walk into a consultation believing an injectable or a skin-tightening device will get

them there. Dr. Andrew Jacono, a dual board-certified facial plastic and reconstructive

surgeon based in New York and practicing exclusively on Park Avenue in Manhattan,

has spent years studying why that assumption usually falls short. His research points to

volume loss deep along the back of the jaw, not sagging skin alone, as the real driver of

an undefined jawline.

Measuring the Mandibular Defining Line

Dr. Jacono and two co-authors published a study in the Aesthetic Surgery Journal

examining 89 patients, or 178 individual sides of the face, who underwent his modified

extended deep-plane facelift technique. The study introduced a new anatomic

measurement, the mandibular defining line, to track how visible and sculpted the jaw

appears from the front of the face. Before surgery, the average measurement was 7.1

centimeters. After surgery, it rose to 9.8 centimeters, a gain tracked over an average

follow-up of 19 months. Patients also gained an average of 3.5 cubic centimeters of

volume in the gonial area, the region overlying the angle of the jaw.

The results back up what Dr. Jacono has argued for years. Jawline aging involves

volume depletion along the posterior mandible, and that’s a factor most fillers and skin-

only procedures can’t correct, since neither reaches that layer of tissue.

A Technique Built on Ligament Release

Dr. Jacono outlined the mechanics behind these findings in a chapter he contributed to

Clinics in Plastic Surgery. His approach extends the deep-plane flap into the neck and

adds a platysmal myotomy, creating what he calls a platysma hammock that defines the

mandibular contour and supports the submandibular gland. Composite flaps of skin,

connective tissue and malar fat are then repositioned to add volume along the midface

and gonial angle rather than pulling the skin tighter.

Dr. Jacono says the goal is "freeing and repositioning deep muscle and fat layers, rather

than stretching the skin," a description he offered in an interview with Vogue Turkey.

The distinction affects how long results hold. An extended deep-plane facelift can last

between 12 and 15 years, and the key factors that affect that longevity include

technique, lifestyle, skin quality and care.

Fellowship Training Behind the Research

Dr. Andrew Jacono has served for most of his career as a Fellowship Director for the

American Academy of Facial Plastic and Reconstructive Surgery, training Fellows from

the organization in advanced techniques that include the jawline-focused methods

described in his research. His body of published work spans more than 70 peer-

reviewed articles, and he performs approximately 250 deep-plane facelifts annually at

his Manhattan practice.

The mandibular defining line has given surgeons a way to measure a result that used to

be judged only by eye. Patients chasing a sharper jaw through injectables alone don’t

always get told why the effect fades so quickly. Dr. Jacono’s data suggests the answer

sits deeper than any filler can reach, in the volume the jaw quietly loses with age.