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Editor,—Enucleation techniques continue to evolve.1 While sclera covered hydroxyapatite orbital implants have been quite effective, two major limitations have led us to study other covering materials. One, while there has been no documented human immunodeficiency virus transmission, several patients have expressed concerns about the use of allogeneic sclera because of that issue.2 Two, in some settings obtaining cadaver donor tissue in a timely manner can be vexing.
Processed calf pericardium has been used in a number of clinical settings as diverse as vascular grafts and neurological surgical patches.3 Animal ophthalmic data with these materials have shown little untoward effect. While theoretic concerns about prion disease can be raised no evidence of this problem has been reported from over 90 000 human implantations.4 While this material is a xenograft that is stored in glutaraldehyde, we are unaware of significant ophthalmic reactions on the basis of either parameter.
I performed a phase I-II trial with commercially available calf pericardium in 14 patients who underwent enucleations for large intraocular tumours. I compared the results with 126 previous enucleations in similar patients by the same author with placement of allogeneic scleral wrapped HA implants. When two of these 14 cases developed early, apparently non-infective suture line breakdown (compared with none previously) I stopped the use of this approach.
In a phase I-II trial 14 eyes of 14 patients, with large intraocular tumours that were not amenable to eye salvage techniques, underwent enucleation. Three patients had large, unilateral retinoblastomas and 11 had uveal melanomas. In the latter group, eight had primary enucleations and three had their eye removed at relatively long intervals after either brachytherapy2 or proton radiation.1 The mean age was 49 years old with a range of 1.3–81 years.
Enucleations were performed in a standard manner, as described elsewhere, using double armed 5-0 polyglycolic and polylactic acids (Vicryl) sutures to imbricate each of the recti muscles.1An 18–22 mm HA implant was soaked in a combination of antibiotic-bupivacaine (Marcaine) solution for 5 minutes then covered with a preshaped Oculoguard calf pericardium (Bio-vascular, Inc, St Paul, MN, USA). The open end of the preformed, bag-shaped material was placed posteriorly and was partially closed with interrupted 4-0 polyglycolic and polylactic acids (Vicryl) sutures. A scalpel was used to create four windows, each approximately 3 × 5 mm located at the equator. After haemostasis was achieved the recti muscles were each attached to the anterior edge of their respective 3 × 5 mm window. Tenon's layer was then closed with a running 4-0 polyglycolic and polylactic acids (Vicryl) circlage suture, and overlying interpreted 4-0 polyglycolic and polylactic acids (Vicryl) sutures. The conjunctiva was closed with a running 6-0 plain gut. The retrospective control group was operated on in an identical manner except alcohol preserved allogeneic sclera was used instead of calf pericardium.
Patients who received calf pericardium covered implants have been followed for 7–20 months following surgery. None of the sockets has been drilled for placement of an integrated implant. In two adults we noted breakdown and retraction of the anterior suture line within 1 month of surgery. In neither of the two cases in which breakdown of the suture line in the first month postoperatively was there ocular radiation, pre-existing conditions, or untoward events noted at surgery. In both cases cultures were negative. In the first case, since I had never had this complication in the first month after an enucleation, I assumed that the suture material had broken and took the patient back to the operating room to close the defect. A culture was negative, and I easily resutured the conjunctival edges, but it again broke down 1 week later. In that patient and the second case that presented with a slightly larger defect 2 weeks after enucleation, we removed the anterior face of the calf pericardium that covered the HA implant, and the overlying conjunctival defect was closed with a dermal graft. The first patient has done well. The second case had recurrent breakdown anteriorly so that we removed the implant. No pathogenic organisms were seen.
In the historic control group (126 cases), who had scleral covered HA implants, I had no cases with this type of complication in the first 6 months after surgery.
A large variation in the incidence of post-enucleation complications have been reported.5 Using the technique outlined above, I have not had an early (<6 months) wound dehiscence or anterior surface breakdown. It is uncertain why we have developed this complication in 14% of cases operated on with bovine pericardium. It is likely that either these patients had a reaction to the xenograft or to the preservative material (although the pericardium is carefully washed in balanced saline solution, bupivacaine (Marcaine) and antibiotics before insertion). In some clinical investigations a higher incidence of early complications with scleral covered hydroxyapatite implants has been reported; these series report wound dehiscence between 5–30%.5 While that higher incidence has been noted by others, it has not been my experience with a surgical technique that has been basically unchanged for several years.
The mechanism responsible for this early wound dehiscence is uncertain. In an animal study that compared bovine pericardium with homologous sclera there was significantly greater inflammation with the former material; all rabbits that received bovine pericardium wrapped implants had diffuse inflammation in the outer 20% of the material.3
It is unlikely that our patients had a subclinical infection (cultures were negative and histological studies showed no organisms) although we cannot completely rule out that possibility.
While there are a number of theoretical advantages with the use of calf pericardium instead of allogeneic sclera, the 14% incidence of a significant complication has truncated my experience with this material.
Supported in part by a grant from the Tumori Foundation.