¡¡¡¡Park et al[5] also discovered the exposure of HA after removing pyogenic conjunctival granuloma. We discovered that 9 cases has variant degree of exposure after the pyogenic conjunctival granuloma excision[6]. We think that friction and damage of conjunctiva increased risk of the exposure of HA. The exposure of HA also increased risk of the infection of pathogenic bacteria such as the pyogenic conjunctival granuloma.

¡¡¡¡Even small or not obvious conjunctiva defection and exposure of HA can also cause aggravation of HA infection[1].The cases with thin conjunctiva after orbital HA implant must be closely followed up£¬some cases can develop the exposure of HA, which must be handled in time. Spontaneous healing of exposed porous implants is relatively uncommon. However, many exposed porous implants can be salvaged with secondary repair[4].

¡¡¡¡The persistent complaint of irritation£¬increase of secretion and appearance of pyogenic granuloma after orbital implant£¬will help us highly doubt the possibility of infection of HA.
Histopathologic examination revealed chronic inflammation and microabscess formation in the explanted implants[3].The bacteria culture of secretion discovered that Gramª²positive anaerobic coccobacteria is the main pathogenic bacteria of pyogenic conjunctival granuloma.

¡¡¡¡Coating Materials May Have Relation with Pyogenic Granuloma  Extensive porous system of HA permitting fibrovascular tissue ingrowths, which is difficult to implant HA into the orbit cavity for it¬ðs rough surface, with increasing incitement and abrasion to the orbital soft tissue, and implanted resistance.

¡¡¡¡A variety of wrapping materials have been used with variable results for HA implantation, including autogenous sclera,banked sclera[6],dermis fat grafts[7],temporalis fascia,fascia lata and other patch graft materials[2].Poor vascularisation and graft melting that lead to exposure of HA were frequently seen in cases where some graft materials were used.

¡¡¡¡Coated with banked sclera and other coating material, HA was implanted easily into the orbit cavity. The ocular muscle or surrounding orbital soft tissue can be accurately fixed on the HA, which reduced the exposure of HA. However,coating material is obstacle for vascularization of HA[8]. Sufficiently vascularized HA decreased the risk of implant extrusion and infection.

¡¡¡¡The development of pyogenic granuloma in HA orbital implants may be related with coating material, which may lead to rejection or foreign body reaction.

¡¡¡¡Banked sclera has little antigen, as the main coating material, it was widely used in HA implant. We discovered that the incidence of pyogenic conjunctival granuloma with banked sclera is higher than with autogenous sclera£¨10.71%ª²2.06%£©. Banked sclera possibly induces reject reaction or foreign body reaction,the protection is lower when banked sclera was absorbed, which increased the risk of implant exposure and infection. It was possible that banked sclera contain pathogen, which lead to secondary infection of HA. HIVª²1 gene was detected in banked sclera in the recent research[9], that means careful choose of banked sclera,without extension of infection.

¡¡¡¡As a coating material, bull arcula cordis may provoke severe rejection in earlier period after implant, with the conjunctiva deliquesce and exposure of HA,especially in the young patients. Pyogenic granuloma may develop after the bull arcula cordis was used in HA implant[10].
The artificial coating material can avoid the infectious diseases and rejection£¬that was induced by banked sclera or other biomaterial.But synthetic material like polytetrafluoroethylene also can induce pyogenic granuloma as foreign body reaction.
Pegging and drilling of HA increased risk of the pyogenic granuloma.

¡¡¡¡After pegging and drilling of HA implant,the orbital HA implant appeared to provide superior cosmesis and motility. The HA implant must be sufficiently vascularized before being drilled which decrease the risk of implant exposure and infection.

¡¡¡¡Pyogenic conjunctival granulomas rarely developed in patients without pegging HA implants. Jordan et al[11] reported that the incidence of pyogenic granuloma is 13.2%¡«30.6% after pegging and drilling of HA implant. We reported 10 cases of pyogenic granuloma, which developed in 1 unpegged implants patient and 9 patients after pegging and drilling of HA implant. After 4ª²7 years of pegging and drilling of HA implant, pyogenic conjunctival granulomas were generated in 9 patients. Among them, the earlier plastic pegs were used in 7 patients, and the titanium peg in 2 patients. The plastic pegs were extruded or prolapsed by the proliferated granulation tissue. The drilling holes were packed with the granulation tissue. But the titanium pegs were conjugated with HA implant firmly. We think that pegging and drilling of HA implant increase the incidence of pyogenic conjunctival granuloma. It is possible that pegging and drilling of HA implant destroyed the integrity of conjunctiva, leading to the exposure of HA implant[6].The secondary infection was generated easily in the gap between the peg and HA implant.
Jordan¬ð research did not show the development of pyogenic conjunctival granuloma which were related with implanted peg material after pegging and drilling of HA implant[11].Our previous study reported that pyogenic granuloma developed only in the patients with implanted plastic peg, not in Tiª²peg patients. Recently we discovered that pyogenic granuloma generated in 2 patients with implanted Tiª²peg in long time followª²up[6].We think that the implanted Tiª²peg can not prevent the development of pyogenic conjunctival granuloma. The Tiª²peg have used in our hospital for more than 4 years, more cases of pyogenic conjunctival granuloma will be diagnosed in future.

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