The lower jaw has numerous constituent parts one of which is the ramus. The ramus of the mandible has considerable clinical interest as it is associated with multiple reconstructive and aesthetic procedures. The well known sagittal split ramus osteotomy (SSRO) is a fundamental orthognathic surgery procedure that splits the ramus into two pieces in a sagittal direction for distal bony segment repositioning. The ramus is also one of the most common sites of jaw fractures and poses unique stabilization concerns because of its numerous muscle attachments. It can also be aesthetically reduced by v-line surgery or augmented by various types of jaw angle implants.
On causal glance the mandibular ramus seems anatomically simple. But on closer inspection it actually has four sides, two surfaces, four borders and two processes. The lower two-thirds of its exterior surface, below the two processes (coronoid and condylar processes) is what is of aesthetic significance and is where the entire masseter muscle attaches throughout its borders. The lower end of the posterior. border and the entire inferior border up to the external oblique line is raised as a result of this muscular attachment.
The aesthetic relevance of the external oblique ridge, or what could be called the anterior ramus line or border, is that this creates an exact outline of where the masseter muscle resides. This provides shape to the jaw angle area particularly in males where the muscle is thicker and the ramus lines more distinct.
Historically the consideration of the anterior ramus line was not factored into isolated jaw angle or custom wrap around jawline implant designs. Having looked at thousands of 3D CT scans I have observed that many male patients have this line the more developed the jaw angle/jawline is.
This natural bony feature may be of aesthetic value in custom jawline implant designs to provide some enhanced definition in the angle area. It would more clearly be seen in patients with thinner overlying soft tissue. Rather than having a completely linear line that tapers from the jaw angle to the chin. (making the posterior gonial angle the widest part of the jawline) such a feature may help make the jaw angle more defined .
Dr. Barry Eppley