P. De Potter et al., Postcontrast magnetic resonance imaging assessment of porous polyethylene orbital implant (Medpor), OPHTHALMOL, 107(9), 2000, pp. 1656-1660
Objective: To evaluate the fibrovascular ingrowth progression within the po
rous polyethylene orbital implant (Medpor) with serial magnetic resonance i
maging (MRI).
Design: Prospective, nonrandomized, comparative (self-controlled) trial.
Participants: Ten patients who underwent enucleation and implantation of a
20-mm porous polyethylene implant wrapped with heterologous sclera.
Methods: Serial precontrast and postcontrast T1-weighted MRI were obtained
at 1.5, 3, 6, and 12 months after implantation. The percentage area of enha
ncement was calculated by use of manual planimetric contouring unenhanced a
reas at the equator of each sphere on axial and coronal planes.
Results: All the implants showed enhancing areas as early as 1.5 months aft
er enucleation, In 8 of the 10 patients, the areas of enhancement at the eq
uator of the implant consistently showed similar centripetal progression pr
imarily during the first 6 months after enucleation, The presence of fibrov
ascular tissue at the equator was associated in all cases with enhancing zo
nes at the anterior portion of the implant. None of the implants showed dif
fuse complete enhancement after 12 months. Two patients failed to demonstra
te further enhancement progression 1.5 months after implantation. No histop
athologic study to equate with the MRI findings was performed in this serie
s.
Conclusions: Postcontrast magnetic resonance studies seem to be the best-su
ited imaging modality for assessing the fibrovascular tissue progression in
to porous polyethylene spheres after enucleation and for identifying patien
ts in whom failure of vascularization occurs. Incomplete vascularization at
the equator of the porous polyethylene sphere does not prove an absence of
fibrovascular ingrowth in the anterior region. Prior ocular surgery and co
existing arterial hypertension may slow the progression of fibrovascular in
growth. Ophthalmology 2000;107:1656-1660 (C) 2000 by the American Academy o
f Ophthalmology.