Jaw angle reduction surgery, technically known as reduction gonioplasty, is a well known procedure to help reduce a square lower face. It is particularly common in Asians who often have more of a wider face with thicker masseter muscles and greater posterior jaw bone width. It has been practiced for years and is often part of other facial reshaping procedures with the goal of an overall thinner face.
Jaw angle reduction surgery can be done by one of two techniques, a oblique ostectomy (amputation) and a sagittal reduction. (outer table ostectomy) Each has their own advantages and disadvantages with an ostectomy being a more aggressive bone reduction method than an ostectomy. But either jaw angle reshaping techniques involves the need to raise the masseter muscle off the bone to perform the surgery. What effect this has on the long-term result has never been studied. Although it has been hypothesized, based on other jaw angle surgeries, that some muscle thinning effect may occur as well due to muscle trauma and disinsertion.
In the September 2014 issue of the Journal of Craniofacial Surgery, an article appeared entitled ‘Long-Term Changes in the Masseter Muscle Following Reduction Gonioplasty’. In this paper, 56 patients were studied before and four years after jaw angle reduction surgery with 3D CT scans. The changes in the volume and shape of the masseter muscle were analyzed. Their results showed that the masseter muscle shrunk an average amount of 21% in the lower part of the masseter muscle in long-term follow-up.
This study confirms what would be suspected with elevating the masseter muscle for any surgery, whether it be jaw angle reduction, jaw angle implants or sagittal split osteotomies. Elevation and disinsertion of the muscle results in some degree of atrophy and loss of muscle bulk afterwards. This can potentially create a skeletonization of the jaw angle area which may account for some of the facial narrowing effect. This could have a positive or negative effect on the jaw angle reduction result depending upon how much bone is removed.
Dr. Barry Eppley
Indianapolis, Indiana