Background: The deltoid muscle is a primary abductor of the upper arm whose mass gives the shoulder its rounded shape. Despite its seemingly uniform rounded shape it actually has three distinct heads or muscle masses, the anterior, lateral and posterior heads which helps the arm abduct in different planes. It is innervated exclusively by the axillary nerve.
The axillary nerve can be injured by a variety of mechanisms such as trauma or. Surgery. When sustaining a significant injury the deltoid muscle will quickly atrophy down to just a fraction of original mass. Instead of a convex shape in profile the shoulder becomes indented or concave. With that loss of muscle mass comes shoulder asymmetry which appears as if a bite of tissue was taken from the shoulder. It becomes skeletonized with the prominent appearance of the bony acromion and coronoid processes of the scapula.
In treating the aesthetic shoulder asymmetry from deltoid muscle atrophy, treatment options include fat injections and implants. Each has their advantages and disadvantages. When implants are a consideration the relevant issues are what type of implants (size, shape and number), the incision placement to insert them and what tissue pocket should be used..
Case Study: This young male suffered an axillary nerve injury from prior shoulder surgery two years previously.He was bothered by the shoulder asymmetry from deltoid muscle atrophy.
As a young male he opted for deltoid implants to help improve his shoulder asymmetry. The deltoid implants were made using a custom moulage method, creating an initial one piece moulage. This would be used to create a mold from which an ultrasoft solid silicone implant would be made. During surgery this would be separated into a smaller anterior deltoid implant and a larger posterolateral deltoid implant.
Under general anesthesia the markings for the two deltoid implants were outlined based on tracings from the fabricated implant. On the back table the one piece implant was separated into the smaller anterior and larger posterolateral implants. Multiple perfusion holes were placed through the implants by dermal punches to encourage postoperative soft tissue ingrowth during healing.
The smaller anterior deltoid implant was placed through a 2.5cm incision just lateral to the AC joint. Initial subfascial dissection enabled entrance into the sub muscular space which occurred rather easily due to the muscle atrophy.
The larger posterolateral deltoid implant was placed through a 3cm incision placed more posterior to the first incision but at the superior aspect of the residual muscle. The muscle atrophy enabled an atraumatic subfascial pocket dissection and implant insertion.
Both incisions were closed in multiple layers with a subcuticular closure of the skin. The immediate results showed a good restoration of shoulder muscle volume.
There are numerous methods of making custom body implants of which the moulage method is an effective one. It is an artistic method that requires creating a silicone elastomer putty mixture and molding it into the desired contour shape until set. From these silicone moulage templates the permanent implants are created by injection into printed molds from the scanned models. Implant designing can also be done from 3D shoulder CT scans but comes at a higher cost to do so.
1) Deltoid muscle atrophy is a common sequelae of an axillary nerve injury.
2) For the shoulder asymmetry due to deltoid muscle atrophy an effective treatment option are implants for which a custom design approach works the best. A moulage design technique is one method for such custom implant fabrication.
3) Deltoid implants are most effectively placed in either the subfascial or submuscular pocket through small superior skin incisions.
Dr. Barry Eppley