At Issue: Integrated implants

Ocular Surgery News posed the following question: The integrated implant for enucleation or evisceration surgery is a major advance in the evolution of implant surgery. How often do you use integrated implants?

Issue: August 25, 2008

Thomas J. Joly, MD, PhD

Superior stability within the muscle cone

I use an integrated implant, either hydroxyapatite or polyethylene, in the great majority of cases for enucleation or evisceration.


	Thomas J. Joly

The superior stability of these implants within the muscle cone is my primary reason for choosing them. The risk of migration or extrusion seen with non-integrated implants is practically eliminated with an integrated implant. In addition, an integrated implant allows the option of pegging for improved prosthesis motility, although in my practice, it is the rare patient who pursues this option.

Nonetheless, integrated implants are not without their own problems — in particular, exposure and chronic infection. Over the past 6 years, I have removed two integrated implants, one for chronic inflammation and one for recurrent exposure, and in both cases, I found poor vascularization of the implant and a nidus of chronic abscess within its central core. Both patients were diabetic. In retrospect, these particular patients may have been better served with a non-integrated implant. I use a PMMA non-integrated sphere in cases of evisceration for endophthalmitis and in older patients with co-morbidities that might impair the orbital tissue’s ability to heal into an integrated implant.

When using an integrated implant, it is important to optimize ingrowth of granulation tissue. Impregnating the implant with antibiotic will stimulate granulation ingrowth by inhibiting bacterial growth. A recent study suggests that antibiotic penetration into the implant is maximized by soaking the implant under positive or negative pressure before insertion.

In addition, I routinely open posterior windows in an eviscerated sclera or cut windows under the muscle insertions and leave the posterior pole open in a scleral-wrapped enucleation implant for improved vascular access to the implant.

For more information:

Thomas J. Joly, MD, PhD, can be reached at Virginia Eye Consultants, 241 Corporate Blvd., Norfolk, VA 23503; 757-622-2200; e-mail: tjoly@vec2020.com.

Reference:

J. Badilla, P. Dolman, Methods of antibiotic instillation in porous orbital implants. In: American Society of Ophthalmic Plastic and Reconstructive Surgery 38th Annual Fall Scientific Symposium Syllabus; Nov. 9-10, 2007; New Orleans, La.

John R. Burroughs, MD

Porous implants offer numerous advantages

I use integrated implants 90% to 95% of the time and prefer porous polyethylene. Theoretical advantages of porous implants include fibrovascular ingrowth, which may reduce the risk of infection, migration and extrusion.


	John R. Burroughs

I prefer porous polyethylene (Medpor, Porex Surgical) over other integrated materials because of its light weight, relatively inexpensive cost, durable non-brittle characteristics and variable sizes and shapes. My rare considerations for solid spheres (silicone or acrylic) include infected sockets, secondary implant placement after removal of an infected implant and for patient self-pay cost-saving circumstances. Complications such as exposure and infection are uncommon, and most exposures occur within the first 4 months before fibrovascular integration is complete, as opposed to solid spheres, which may expose and, frankly, extrude many years later.

I do not wrap porous polyethylene implants, as it likely slows vascular ingrowth and adds expense and OR time. I think many, if not most, porous polyethylene implant exposures are related to surgical technique issues, including oversized implants, not closing Tenon’s and conjunctiva separately, or creating too much tension on the conjunctiva.

For eviscerations, I place the implant through a 360° posterior sclerostomy to foster vascularization and reduce exposure risks by completely covering the implant with the overlapping sclera that is sutured with 4-0 Vicryl. For enucleations, I have found good motility success by placing the implant intraconally, draping the recti muscles over the implant and then suturing them near the conjunctival fornices with 5-0 Vicryl.

For enucleations and eviscerations, I also recommend, and offer to all patients, the placement of an autologous dermis graft to allow larger implant placement, an additional barrier to exposure, better preservation of the fornices and tension-free closure of the conjunctiva. I prescribe prophylactic cephalexin or clindamycin for 5 days postoperatively and place a tight pressure patch for 3 or 4 days postoperatively.

I recommend that less-experienced surgeons err on the side of smaller implants to lessen complications and because there are numerous low-risk options for enophthalmos correction, if subsequently necessary.

For more information:

John R. Burroughs, MD, can be reached at Eye and Facial Appearances, 111 East Polk St., Colorado Springs, CO 80907; e-mail: jrburroughs67@yahoo.com. Dr. Burroughs has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.

References:

Su GW, Yen MT. Current trends in managing the anophthalmic socket after primary enucleation and evisceration. Ophthal Plast Reconstr Surg. 2004;20:274-280.

Vagefi MR, McMullan TF, et al. Autologous dermis graft at the time of evisceration or enucleation. Br J Ophthalmol. 2007;91:1528-1531.

Vagefi MR, McMullan TF, et al. Injectable calcium hydroxylapatite for orbital volume augmentation. Arch Facial Plast Surg. 2007;9:439-442.

Richard L. Anderson, MD, FACS

Evolutions in design have aided motility, retention

A number of integrated implants were used long before 1989. The Cutler implant was the best-known. Although early results were good in many types of integrated implants, virtually all suffered the same long-term complications of extrusion and infection. Therefore, most surgeons before 1989 turned to quasi-integrated buried implants to provide good motility and retention. The Allen implant, Iowa implant and Universal implant were excellent implants.


	Richard L. Anderson

Since 1989, many hydroxylapatite implants have been placed with pegging in an attempt to improve motility. It was thought that the vascular ingrowth into these implants made from coral would help prevent infection and extrusion and allow drilling and pegging. I have stopped drilling and pegging because of the many complications early and late. Very few of our retained coralline implants still have pegs, and many of these implants also eroded anteriorly and required removal or repair. The abrasive sharp surfaces of the coralline implant erode through Tenon’s and conjunctiva.

Anyone who scuba dives can understand the sharp, cutting nature of coral surfaces. About a decade ago, I gave up coralline implants, realizing that my retention rates were better and motility was as good with the old Iowa implants and Universal implants (Oculo-Plastik) that I helped design. However, I still believe that the porous nature of an implant helps prevent migration from the vascular ingrowth.

Therefore, I worked with Porex Surgical to make a Universal-like implant out of Medpor material. It has four mounds similar to the Iowa and Universal implants and is called the Quad Motility Implant. Originally, the mounds were slightly abrasive, which led to a few erosions. These mounds have been smoothed in the present design, and I feel this type of quasi-integrated implant provides excellent motility and retention without the complications of integrated implants.

For more information:

Richard L. Anderson, MD, FACS, can be reached at Center for Facial Appearances, 1002 E. South Temple, Suite 308, Salt Lake City, UT 84102; 801-363-3355; e-mail: rick@centerforfacialappearances.com. Dr. Anderson has a financial interest in the Quad Motility Implant from Porex Surgical.

References:

Anderson RL, Thiese SM, et al. The universal orbital implant: indications and methods. Adv Ophthalmic Plast Reconstr Surg. 1990;8:88-99.

Anderson RL, Yen MT, Lucci LM, Caruso RT. The quasi-integrated porous polyethylene orbital implant. Ophthal Plast Reconstr Surg. 2002;18:50-55.

Jordan DR, Anderson RL, Nerad JA, Allen L. A preliminary report on the Universal Implant. Arch Ophthalmol. 1987;105:1726-1231.

Jeffrey A. Nerad, MD, FACS

No ideal anophthalmic socket implant at this time

The term integrated implant was originally used in the 1940s to describe the direct attachment of a prosthesis to the implant. These early implants were integrated directly to the prosthesis through an opening in the conjunctiva – a technique known as open integration. This integration provided excellent motility of the ocular prosthesis. Unfortunately, over time, all of these implants became infected and extruded.


	Jeffrey A. Nerad

With the introduction of the hydroxyapatite implant (HA, BioEye) in 1985, the idea of a buried porous implant that would allow vascular ingrowth and support a closed integration of the prosthesis and implant brought a renewed interest in the anophthalmic socket. The hope was that the movement of the old, exposed open-integrated implant with the “lock-and-key” fit of the 1940s could be incorporated into a system that would not become infected.

Unfortunately, in most patients, the epithelium over the peg site is not able to withstand the pressures of the peg against the implant when the implant moves and the prosthesis abruptly stops hitting the fornices. Exposure, irritation, infection and granulation tissue occur at the junction of the implant and peg. Several revisions of the integration system have not solved these problems. Consequently, most surgeons have abandoned any attempts at pegging or integrating a hydroxyapatite implant with the prosthesis.

Porous polyethylene spheres (Medpor, Porex Surgical) were introduced as an alternative to hydroxyapatite. Medpor implants appear to have a lower exposure rate than hydroxyapatite, perhaps because of a smoother anterior surface. Attempts at the integration of the implant and prosthesis have been attempted but not yet achieved. A titanium screw integration system was introduced but did not gain wide acceptance. A new magnetic coupling device has more recently been introduced that may allow enough implant-prosthesis coupling for movement, at the same time providing the necessary slippage to avoid tissue breakdown. Unfortunately, this magnetic device does not allow imaging with MR scanning.

Synthetic hydroxyapatite and other ceramic materials continue to be tested as implant materials. A few surgeons still peg these implants with some success due largely to diligent attempts at revisions as needed.

There is no ideal anophthalmic socket implant at this time. Everyone agrees that the implant should restore adequate orbital volume requiring at least a 20-mm sphere. Most surgeons would agree that the extraocular muscles should be reattached to the implant. The “perfect union” or integration of the implant and prosthesis has not been found.

For more information:

Jeffrey A. Nerad, MD, FACS, can be reached at the University of Iowa Hospitals & Clinics, Eye Department, 200 Hawkins Drive., Iowa City, IA 52242-1009; 319-356-2590; e-mail: jeffrey-nerad@uiowa.edu. Dr. Nerad has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.