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Hydroxyapatite implant becomes vascularised and integrated in the orbital tissues. In view of the rough hard external surface, wrapping materials are used to enclose the hydroxyapatite implant that facilitate attachment of extraocular muscles. Various wrapping materials have been tried including donor human sclera,1 acellular dermis,2 rectus abdominis sheath,3 posterior auricular muscle,4 polyglactin mesh,5 and bovine pericardium.6 In this report, we present our 5 year experience with the use bovine pericardium wrap. The wrap is presterilised using glutaraldehyde, ethanol, and propylene oxide to minimise the risk of transmission of bacterial and viral infections.
Patients and methods
All patients undergoing primary enucleation for large choroidal melanoma with the insertion of hydroxyapatite implant wrapped in processed bovine pericardium were included in the study. Patients with less than 3 months’ postoperative follow up or radiotherapy were excluded.
Three consultant ocular oncologists performed all the surgeries. After enucleation and haemostasis, a size 18 or 20 mm hydroxyapatite orbital implant was wrapped with bovine pericardium wrap (Ocugaurd Supple, Bio-Vascular Inc, St Paul, MI, USA) (fig 1). The posterior loose ends were anchored securely on the implant with a 6-0 Dacron suture joining opposite ends of the wrap. Windows in a square or slit configuration were cut into the wrap and all four rectus muscles were attached to the anterior lip of the apertures (fig 2). The Tenon’s capsule and the conjunctiva were closed in two layers with interrupted 6-0 Vicryl sutures. An artificial eye was inserted approximately 6 weeks postoperatively and the patient was reviewed every 3–6 months.
In all, 104 (62 men and 42 women) consecutive patients operated between July 1998 and July 2002 were included. The first 27 of these patients formed part of a preliminary report published previously.6 Median age at diagnosis was 61 years (range 21–88 years). There were no intraoperative complications in any case. Median postoperative follow up was 2.35 years (range 3 months to 4.5 years).
One patient developed pyogenic granuloma and one additional patient had large subconjunctival haematoma that resolved spontaneously. Three patients (2.9%) developed postoperative wound dehiscence. In two patients, dehiscence within 6 weeks of enucleation with exposure of the implant required replacement with high density polyethylene biomaterial implant (Medpor, USA). The remaining patient’s conjunctival wound was resutured.. Three additional patients needed a lateral canthal sling operation between 6–12 months after enucleation. The overall cosmetic result was excellent in 101 patients (97%) and with ocular motility satisfactory to the patients.
It is important to have a wrapping material that is safe and easy to use. The harvesting of autologous materials leaves scars and increases the surgical time.7
Sclera is the most commonly used wrapping material for hydroxyapatite implants associated with varying rates of wound dehiscence (7.5%–19.3%).8 Comparable wound dehiscence rates of 5–14% with bovine pericardium wraps have also been reported.9,10 Wound dehiscence/implant exposure rate of 2.9% in our series is much lower than other published series using bovine pericardium or human donor sclera.8,10 Low complication rate in our series could be attributed to inclusion of cases without any orbital pathology, exclusion of cases treated previously with irradiation, and the meticulous wound closure.7
Concerns regarding possible association of the use of sclera with the transmission of viral and prion infections including Creutzfeldt-Jakob disease has forced the clinicians to search for alternative materials.11,12 It is believed that the risk of transmitting prion disease by human or animal derived tissue is proportional to the risk of the donor harbouring them.12 With the use of bovine pericardium originating from countries not known to have bovine spongiform encephalitis the risk of transmission of such infections can be minimised.
Our study suggests that the use of bovine pericardium as a wrap for hydroxyapatite implants is a safe alternative to other wrapping materials and has a low rate of complications when performed in the setting of primary enucleation.