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Background: The back of the head is prone to the greatest frequency of aesthetic shape deformations. This is no surprise given that the back of the head is exposed to the greatest amount of external forces from how the fetus lays in utero to how the baby lays after birth and beyond. When this is combined with the genetic tendency of certain ethnicities to have a decreased anteroposterior skull length, flatness and asymmetry of various amounts of the back of the head are not uncommon.

Also, the back of the head is not just a flat surface of one continuous skull bone. Rather it represents the union of three skull bones  (paired parietal bones and one single occipital bone) which are joined by the midline sagittal and paired lambdoidal sutures. Such a confluence of skull structures is prone to shape deformations that are different and unexpected from the most recognizable although more rare craniosynostosis deformities.

One such unexplained back of the head deformity is flatness that is associated with a large indentation that adds some concavity to it. This could be a linear groove down the center of the back of the head or a circular crater-like indentation. For some patients they may want only the concavity filled while others, and most, want an overall roundness added to the back of the head.    

Case Study: This female had a flat back of the head she wanted augmented but a palpable crater existed in the center of it. Her 3D CT scan showed a flatness in profile and a large circular indentation with the union of the sagittal and lambdoid sutures at its central depth.

A custom back of the head skull implant was designed to add some roundness to the back of the head. It was thickest at its middle location in the depth of the crater at 15mms. It was important to keep the implant volume no greater than 150ccs in volume. The total implant at this thickness was 154ccs. 

Under general anesthesia and in the prone position, the flatness of the back of her head could be appreciated with a positive cup test. (A cup that sits flat and does not fall off)

A low horizontal scalp incision was made over the nuchal ridge and the bone on the back of the head was exposed, revealing the large indentation as seen on the 3D CT scan. The custom skull implant was prepared by the placement of multiple perfusion holes, inserted and positioned and secured with multiple small micros screws at its inferior edge. It was a very tight scalp closure so no drain was placed.

The immediate improvement in the shape of the back of her head could be appreciated while she was still in the prone position.

Flat back of the heads with an actual crater indentation are rare but can be successfully corrected (crater) and augmented. (flat to convex shape) But in doing so some implant volume will be lost in the crater that does not benefit the augmentation proper. This  needs to be calculated into the implant design to ensure that it will fit within what the scalp stretch can accommodate.

Key Points:

1) A flat back of the head with an indented crater indentation of congenital origin is a rare aesthetic skull deformity

2) A custom skull implant design can fill in the crater and round out the back of the head within the limits of the scalp stretch to accommodate the increased volume.

3) The depth of the occipital-parietal indentation will steal some volume from how much the back of the head can be rounded out.

Dr. Barry Eppley

World-Renowned Plastic Surgeon

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