Mechanisms and treatment of extruding intraconal implants: socket aging and tissue restitution (the "Cactus Syndrome").

OBJECTIVE To investigate the initial features and treatment of 26 consecutive patients referred with extruding orbital implants between January 1991 and December 2004. METHODS Retrospective medical record review recording the reason for enucleation, primary implant type, infection when initially seen, time to implant exposure, location of conjunctival defect, and time to surgical revision. RESULTS Of the 26 eyes, 16 (62%) were removed after trauma, 3 (12%) because of tumor, 3 (12%) because of infection, and 4 (15%) because of painful blind eyes (percentages do not total 100 because of rounding). Of the 26 eyes, 8 (31%) were right eyes and 15 (58%) were hemispheric implants; 8 implants (31%) were acrylic or glass spheres, and 1 (4%) each was a hydroxyapatite, porous polythene, or bone sphere. Hemisphere extrusion occurred at a mean of 16 years after implantation, significantly later than with spheres (mean, 10 years after implantation; P = .05). The conjunctiva was breached medially in only 1 (sphere) (4%), centrally in 13 (50%), and laterally in 12 (46%). Lateral erosion occurred solely with hemispheres, in contrast to central erosions, in which 10 of 13 (77%) were spheres (P < .001). Twelve patients (46%) underwent surgical revision within a year of extrusion, 7 (27%) within 2 years, and the remaining 7 (27%) at 2 to 21 years. CONCLUSIONS Exposure of hemispheres occurred later, from pressure erosion at their prominent lateral edge. In contrast, central erosion (in spheres) occurred earlier, because of gradual tissue restitution after forced-ball implantation ("cactus syndrome"). This may be avoided by implantation through a polythene glide.