Hydroxyapatite (HA) orbital spheres are the most commonly used implants after primary enucleations.1 The wide acceptance of HA implants is due to its high biocompatibility and optimal pore size, which permits host fibrovascular ingrowth. Rapid integration of the implant into the orbital soft tissues offers many potential advantages over nonporous implants, including diminished risk of infection, resistance to implant migration, and enhanced motility with implant peg-prosthesis coupling. We are aware of only 2 histopathologic case reports detailing the degree of host fibrovascularization of a HA sphere (removed because of an orbital malignant neoplasm and not an implant infection) within the first few months after placement of an implant in a human orbit.2,3 Shields et al2 reported approximately 3 mm of fibrovascular ingrowth at the sites of precut scleral windows in a 20-mm, scleral-wrapped, HA sphere removed 4 weeks after implantation in a 69-year-old man. Similarly, in a 20-mm, scleral-wrapped, HA implant removed 19 days after implantation in a 9-year-old boy, Rosner et al3 described a matrix of loose connective tissue extending 6 mm into the sphere in the area of a prefashioned scleral window. Fibrovascularization was most prominent at the surface of the implant. We report herein fibrovascular ingrowth into the paracentral region of a HA implant removed 97 days after implantation.
A 55-year-old otherwise healthy man with a blind, painful right eye due to neovascular glaucoma of unknown cause underwent enucleation with placement of a 20-mm synthetic HA orbital implant (FCI; Issy-Les-Moulineaux, Cedex, France). The sphere was wrapped in polyglactin 910 mesh (Vicryl; Ethicon Inc, Somerville, NJ) and the rectus and inferior oblique muscles were attached as previously described.4 Histopathologic examination of the enucleated globe revealed an occult ring melanoma of the ciliary body with extensive intraocular invasion and extraocular extension to the episcleral surface with involvement of the perilimbal conjunctiva at the surgical resection margin. Three months postoperatively, a pedunculated conjunctival mass was noted in the patient's anophthalmic socket. The biopsy specimen from the lesion demonstrated recurrence of his ocular melanoma. Orbital exenteration of the right socket was performed 97 days after enucleation.
After decalcification of the exenterated orbital implant, the HA sphere was sectioned anteroposteriorly and examined to determine the degree of host fibrovascular ingrowth. Fibrovascularization, associated with a mild, predominantly chronic, inflammatory cell infiltrate, was evident in the peripheral (outer third) and paracentral (between the outer third and central third) regions of the implant (Figure 1 and Figure 2). The intertrabecular spaces in the central third of the implant were devoid of fibrovascular tissue and contained an exudate, with occasional histiocytes, which also was present focally in the paracentral portion of the implant (Figure 1 and Figure 2). The degree of fibrovascular ingrowth occurred approximately equally throughout the circumference of the HA sphere, extending up to 5 mm from the surface toward the center of the implant. Several multinucleated foreign body giant cells were noted adjacent to the trabeculae, mainly toward the periphery of the implant (Figure 2, inset). The external surface of the implant was covered with fibrovascular tissue of variable density and thickness, from which the fibrovascular septa arose, and contained some multinucleated giant cells in which tubular spaces were identified, presumably representing previously digested polyglactin 910 mesh and/or suture material.
An anteroposterior section of the implant demonstrates fibrovascularization (F) in the peripheral (outer third) and paracentral (between the outer third and central third) regions of the hydroxyapatite implant. An inflammatory exudate (E) is present more centrally (hematoxylin-eosin, original magnification ×11).
The junction between the fibrovascularization (F) and the more central exudate (E) is evident in the paracentral region of the implant (hematoxylin-eosin, original magnification ×30). Inset, Multinucleated foreign body giant cell adjacent to intertrabecular fibrovascular tissue (F) (hematoxylin-eosin, original magnification ×500).
Histologic evaluation of the rate of host fibrovascular ingrowth of HA orbital implants has been mainly limited to animal studies, where fibrovascularization has been noted to extend to the center of a 12-mm polyglactin 910–wrapped HA implant by 1 month.5 Fibrovascular ingrowth in both the coralline HA implant (Bio-eye; Integrated Orbital Implants Inc, San Diego, Calif) and synthetic HA implant (FCI) has been shown in a rabbit model to occur at a similar rate.6 To our knowledge, our case represents the third report of a HA spherical implant removed from a human orbit due to an orbital malignant neoplasm in the early postoperative period and prior to complete fibrovascularization to the center of the implant. In both of the previously reported cases, the coralline HA implants were wrapped in sclera and removed within the first month after implantation.2,3 The synthetic HA implant described in our patient was wrapped in polyglactin 910 mesh and not removed until day 97 after implantation, but it demonstrated a similar tissue response as previously noted in the coralline HA implants.2,3 Prominent fibrovascular ingrowth was evident uniformly to the paracentral zone of the implant. The center of the implant did not demonstrate fibrovascularization. A better understanding of the rate at which fibrovascular ingrowth occurs in HA orbital implants is important in establishing the appropriate time for implant drilling and motility peg placement. The generally accepted guideline of waiting at least 6 months after implantation to drill HA implants is supported by the absence of central vascularization in our patient 3 months after implantation of a synthetic HA sphere.7
Corresponding author: David R. Jordan, MD, 340 McLeod St, Suite 104, Ottawa, Ontario, Canada K2P 1A4.
Klapper SR, Jordan DR, Brownstein S, Punja K. Incomplete Fibrovascularization of a Hydroxyapatite Orbital Implant 3 Months After Implantation. Arch Ophthalmol. 1999;117(8):1088-1089. doi: