Long term follow up of bone derived hydroxyapatite orbital implants

Abstract

Aims: To document the long term experience of bone derived hydroxyapatite orbital implants and compare results using scleral wrapped implants with those not using sclera.

Methods: This retrospective case series reviewed the long term follow up of 118 patients with 120 eyes which had undergone enucleation and bone derived hydroxyapatite orbital implant insertion at Dunedin Hospital from 1977 until 2000. Patient details were obtained from theatre records, case note review, patient interview and examination, interview of patient relatives, and family general practitioner records.

Results: Of the 120 eyes 84 had bone derived hydroxyapatite orbital implants with sclera and 36 without sclera. Follow up was 0.5-25 years (mean 8.9 years). 25 (19.3%) suffered minor complications of limited exposure of the implant which resolved spontaneously, with implant drilling or wound resuture. Nine (7.5%) suffered major complications requiring explantation. Major complications were more likely in cases with major tissue disruption, ischaemia, or inflammation. There were significantly fewer complications in the group where a bone derived hydroxyapatite orbital implant was implanted without a scleral covering (p<0.05).

Conclusions: The placement of a bone derived hydroxyapatite orbital implant in the socket was associated with a low rate of long term complications and good cosmesis in most cases. The omission of a scleral covering over the hydroxyapatite sphere had some advantages and may prove to be the procedure of choice.

Figure 1

Spontaneous absorption of scleral cap with exposure of underlying non-organised bone 2.5 years after insertion of implant in 32 year old patient H with diabetes and Turner’s syndrome. Photograph shows oedematous conjunctiva with scattered light reflexes and a central area of exposed bone. No treatment was given and the patient continued to wear the prosthesis.

Figure 2

Photograph taken 12 weeks after initial exposure in patient H. The conjunctiva is healthy with few light reflexes Spontaneous debridement of the bone is complete leaving a conical cavity lined by healthy conjunctiva.

Figure 3

Axial T2 TSE scan (TR 3000 ms TE eff 120 ms) through the mid-orbits in a 60 year old patient 10.5 weeks after enucleation and right implant without a scleral cap. This shows increased T2 signal centrally consistent with oedema here. The presence of oedema indicates the presence of tissue fluid or recent ingrowth of vascular connective tissue while the areas of low signal indicate the presence of mature connective tissue occupying the entire periphery of the implant.

Figure 4

Axial T2 TSE scan (TR 3000 ms TE eff 120 ms) through the orbits of a 19 year old patient 12 weeks after enucleation and right implant with a scleral cap. This shows increased T2 signal consistent with oedema centrally and extending to the anterior surface of the implant, deep to the scleral cover. The presence of oedema indicates the site of tissue fluid or recent ingrowth of vascular connective tissue while the areas of low signal indicate the presence of mature connective tissue occupying the posterior and equatorial periphery of the implant. The scleral cap shows as a linear area of very low signal.