Abstract
Purpose :
This histoplathological study of the capsules encasing an orbital poly methyl methacrylate (PMMA) implant aims to describe their histopathologic, immunohistochemical and scanning electron microscopy (SEM) characteristics and correlate myofibroblastic changes within the capsule with implant failure.
Methods :
This was an in-vitro histopathologic, immunohistochemistry and scanning electron microscopy study performed on ten excised specimens of orbital peri-implant capsules harvested at the time of implant exchange. Data collected included demography, clinical presentations, etiology of the explantation, age of the capsule in months, inflammatory cells noted/high power field (HPF), CD3, CD20 and CD68, capillary proliferation/HPF, percentage Masson’s trichrome staining, mean capsular thickness, smooth muscle antigen (SMA) expression and SEM characteristics. Implant failure was defined as implant exposure/extrusion/migration over the follow up period.
Results :
Mean patient age at presentation was 33.3±13.08 years. Of the 10 included patients, eight underwent an implant exchange for an exposed/extruded/migrated implant and the remaining two underwent an implant exchange for volume augmentation. Mean age of the fibro-collagenous membranes was 32.86±57.25 months (median 13 months). Median CD3, CD20 and CD68 positivity was 80%, 9% and 7% denoting a predominant T-lymphocytic response. Mean capsular thickness was 733±421.71µ (median 677.85µ). Age of the harvested capsule showed a linear correlation with inflammatory cells/HPF (r=0.93, p<0.0001, 95% C.I. 0.73 to 0.98), with CD3 positivity (r=0.6, p=0.04, 95% C.I. 0.02 to 0.9), with capillary proliferation/HPF (r=0.85, p=0.003, 95% C.I. 0.43 to 0.96) and with percentage of cells showing Masson’s trichrome stain positive (r=0.71,p=0.03, 95% C.I. 0.08 to 0.93). The odds of implant failure when SMA was positive were 5 (p=0.36). There was a weak correlation of age of the capsule with its thickness (r=0.4, p=0.35). SEM confirmed the presence of inflammatory cells and fibrosis.
Conclusions :
PMMA orbital spherical implant, incites a predominantly T-cell mediated inflammatory response which clinically presents as a peri-implant capsule. The age of the capsule correlates positively with increasing inflammation and this phenomenon may be responsible for delayed PMMA implant exposure and extrusion.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.