AlphaSphere is a spherical orbital implant for use after enucleations that was recently developed and released by Addition Technology. This implant differs from others currently on the market because of its material makeup that lends to a host of other characteristics that make this implant unique.
Design:
AlphaSphere is the first poly-HEMA (2-hydroxyethyl methacralate) (PHEMA) formulated orbital implant that is made of one inert material, yet exists as two hemispheres differing by water content of the anterior and posterior sections. Unlike other implants that have a smooth anterior surface, the AlphaSphere design is opposite. The anterior portion consists of an endo-skeletal, 3 layer porous hemisphere that allows fibrovascular ingrowth of orbital tissues, a characteristic that is paramount to motility of the implant. The anterior most porous layer is very soft and nonabrasive. It covers a layer of merselene mesh with clear PHEMA beneath. The posterior surface, on the other hand, is smooth and resists fibrovascularization due to its clear, solid gel consistency and decreased water content. The thought behind this particular design is that the extraocular muscles will grow into the anterior surface and the smooth posterior surface will allow for improved motility as it glides through the orbital tissues without being confined from tissue ingrowth. Another advantage of the clear posterior hemisphere is it allows the user to see directly through the implant so depth of suture passes can be verified. The implant is designed so that sutures can be passed directly through the anterior hemisphere given the gel-like consistency, eliminating the need for scleral wrapping. The implants come packaged with a specially designed double-armed 12mm half-circle tapered needle attached to a 5-0 polyglactin suture. The needle design is for sake of ease with passing the needle through the anterior porous surface and engaging the merselene mesh directly beneath. The merselene mesh stabilizes the suture in the implant and prevents cheese-wiring. In general, the sphere is light and very smooth. It is pliable but will not loose its shape. The majority of the Alphasphere composition is water making this implant more similar to the natural globe than other implants. The implant is packaged in sterile water and comes in seven sizes, 1 mm increments ranging from 16 to 22mm with a 3-year shelf life.
Surgical Advantages:
Advantages of this implant include the ability to directly suture the muscles to the implant hence eliminating the need for scleral wrapping. The result is decreased operative time and operative costs. This characteristic is similar to other implants on the market, but the difference is the needle and sutures can be passed anywhere on the anterior surface instead of precisely through premade suture tunnels. In the operating room, the circulating nurse simply opens the jar containing the implant that is suspended in sterile water and transfers the sphere to the scrub nurse. It can then be dipped in an antibiotic solution and placed directly into the orbit. Like porous polyethylene and hydroxyapatite, this implant allows fibrovascular ingrowth for incorporation into the socket, but is less abrasive because of the smaller macro-pores. This characteristic also lends to a very fragile anterior surface that must be handled carefully without the use of sharp instruments.
Surgical Pearls:
The included tapered needle is different to pass than the traditional spatulated needle one would use for the muscles, but regardless, this needle can easily be passed in a double locking fashion through the rectus muscles. A surgical marking pen can be used to place small dots on the anterior surface before placement into the orbit. These markings will serve as an indicator of where the extraocular muscles are to be placed. (See figure below)
If an introducer is used for placement of the implant into the orbit, care must be taken to open the petals so as not to disrupt the fragile anterior porous surface. As well, when manipulating the sphere during muscle reattachment, it is best to use cotton tip applicators because sharp instruments easily shred the porous anterior surface. The 12mm half circle tapered needle tip should be placed perpendicular to the anterior surface and it is best to follow the curve of the needle. This simple maneuver, when done correctly, will guarantee engagement of the merselene mesh, a necessary step to this procedure. (See video) The same 5-0 polyglactin suture on the 12mm half circle tapered needle can be used to suture Tenon’s capsule. It does take a bit more force to get through the tissues given the tapered design. As an alternative, a 5-0 polyglactin suture on an S-24 or S-14 needle can be used and glides through the tissues easier. There is no need for pegging of this implant as motility is very comparable to other implants.
Update:
Several cases to date have been performed using the AlphaSphere orbital implant. When following the surgical pearls given above, use is very easy and, again, surgical time and cost is decreased. Good motility has been documented post operatively and patient comfort has been satisfactory. Ocularists seem to have no troubles fitting prostheses for patients with AlphaSphere implants. Extrusion does not seem to be any more of an issue with this implant than with any other commonly used spherical implants.
The AlphaSphere orbital implant was recently named winner of the prestigious 2010 Alpha Award for Innovation in Engineering & Technology presented by the Engineering Society of Detroit, a society that recognizes creative ideas that generate innovative solutions in engineering and technology.