A challenging journey of maxillofacial implants placement and rehabilitation in an irradiated exenterated socket

Abstract

Rehabilitation of a post-exenterated orbital defect is a necessity, to restore a patient's esthetic appearance and help overcome the associated psychosocial stigma. An implant supported prosthesis enjoys a better patient acceptance due to its superior retention and stability. This clinical report highlights the challenges faced in planning, designing and placement of maxillofacial implants in the supra-orbital rim of an exenterated socket post-radiotherapy along with the management of the unexpected complications which developed subsequently. Administration of hyperbaric oxygen therapy, fabrication of a digitally designed surgical guide to ensure predictable implant placement, selection of surface treated implants for better biomechanical anchorage, and a gentler surgical technique for recovery of irradiated hard and soft tissues were measures undertaken during the treatment phase. An effort has been made to point-out the fact that despite the various approaches adopted in an irradiated patient, success of implant placement in such a situation remains a challenge.

Graphical abstract

1. Introduction

Orbital exenteration is a radical procedure entailing the in-toto removal of the globe along with its surrounding adnexa. It results in deterioration of quality of life due to permanent loss of vision, unpleasant facial appearance and altered lifestyle leading to social ostracism and psychological infirmity.¹ Fitting of cosmetically improving maxillofacial prosthesis in these cases is fraught with difficulties in retention and stability. Osseointegrated implant is a promising alternative, especially for young patients who have undergone exenteration following tumor, trauma or congenital anomalies.²

The survival rate of an implant is adversely affected when an ablative tumor removal is accompanied with adjunctive radiotherapy and chemotherapy. The irradiated bone and soft tissues exhibit profound vascular and cellular after effects.³ Factors such as radiation dose, duration after radiation, general physical condition of patient, and surgical technique are instrumental in determining the implant success rate.⁴ The deleterious effects of radiotherapy can be minimized by adopting measures such as intensity modulated radiotherapy (IMRT), hyperbaric oxygen therapy (HBO) and use of radioprotective drugs.⁵ Digitally driven clinical workup using three-dimensional (3D) imaging, reverse engineering and rapid prototyping may prove to be invaluable tools in such compromised cases.

This clinical report describes a slew of protocols adopted in planning for maxillofacial implant placement in the supraorbital rim of an irradiated exenterated socket with a year-long follow up. The placement of implants was supplemented with HBO therapy and fabrication of a digital surgical guide to minimize tissue reflection and enhance predictability of implants. However, despite adopting several precautions prior, during and post-surgery, the maxillofacial implant placement in the irradiated patient followed an unpredictable course. This clinical case asserts that successful implant placement in such factions remains an uncertainty.

2. Case presentation

A 26-year-old male reported to the Department of Prosthodontics for prosthetic rehabilitation following ablative surgery for chondroblastic osteosarcoma of the maxilla with secondary extension to the orbit. The patient had undergone left maxillectomy along with left orbital exenteration (Fig. 1). Subsequently, he was administered intensity modulated radiation therapy (IMRT) having a cumulative dose of 50 Gy, three months after the surgical resection of tumor. The patient was closely monitored for healing till one-year post-radiotherapy. Clinical examination revealed a well healed composite left orbitomaxillary defect without any inflammation, necrosis or infection. The supraorbital rim was intact, the orbital floor absent, and the lateral wall was incomplete due to complete maxillary and partial zygomatic resection. The patient was taken up for the placement of orbital implants in the supraorbital rim along with fabrication of a definitive cast partial obturator and silicone-based implant retained orbital prosthesis. The patient was explained about the procedure, the risks involved, and the various possible outcomes both favorable and unfavorable and informed consent was taken.

Fig. 1.

Patient with A) Left orbital defect post-exenteration. B) Left maxillectomy defect.

Several pre-intervention measures were taken to improve the uptake, survival rate and predictability of the maxillofacial implants. Hyperbaric oxygen was used in a prophylactic role. A total of 30 dives at 2.5 atmospheric pressure for 90 min were given to the patient inside a monochamber. The Marx protocol was followed with 20 dives being administered prior to the surgery and 10 dives post-surgery. A recent computed tomography (CT) scan of the patient, with a radiographic stent in place, was used to generate a virtual 3D model of the defect. This formed the foundation for the subsequent designing of the surgical guide. The radiographic markers in the stent helped correlate the planned implant positions to their corresponding bony locations. Implant planning was done using a CAD software (Blue Sky Plan, Blue Sky Bio LLC, Libertyville, IL, USA) on the digitally generated model. A mirror image of the contralateral side helped predict the position of the future prosthetic eyeball and accordingly it was decided to place three implants, lateral to the supraorbital notch but medial to the frontozygomatic suture. A virtual implant simulation was done and a stereolithographic surgical guide (SLA, Sagmarks Pvt Ltd, Ghaziabad, UP, India) having a minimalistic design was generated to ensure precise implant placement (Fig. 2A). Based on the CT data, three surface treated maxillofacial implants of 6 mm length and 4.8 mm diameter (Dentium Pvt. Ltd, Gangnam-gu, Seoul, Korea) were selected to ensure maximum mechanical and biological anchorage. Prophylactic antibiotics were administered for a week starting a day prior to surgery to combat the chances of post-surgical infections and ensuing osteoradionecrosis.

Fig. 2.

A) Digitally designed implant surgical guide. B) Maxillofacial implants placed in the left supraorbital rim.

The surgery was conducted in collaboration with the Department of Ophthalmology. The implants were placed under general anaesthesia using a high magnification microscope to ensure accurate implant placement and gentle handling of the fragile tissues post-irradiation. After reflection of skin and periosteal flap, the surgical guide was seated at the intended site followed by sequential drilling at a slow speed of 1200 rpm with constant chilled irrigation to prepare the implant osteotomies. The drills and saline were cooled pre-operatively to decrease the propensity of the heat generation within the cortical bone of the supraorbital rim. Each implant was placed at a low speed of 15 rpm followed by hand torquing (Fig. 2B and Video 1). An adequate primary stability was achieved. The cover screws were placed, and layered suturing was done using polyglactin sutures (6-0) and silk sutures (6-0) to approximate the tissues. The surgical site healed uneventfully. No abnormal hard or soft tissue changes were observed in the six months follow-up. A check CT scan done after six months showed satisfactory implant placement.

The following is the supplementary data related to this article:

Video 1An overview of maxillofacial implant placement in irradiated bone.

The second stage surgery was initiated 6 months post-implant placement. A tissue punch was used to expose the implants and healing abutments were placed to develop a soft tissue collar. The immediate post-operative period was uneventful. However, three weeks later development of multiple, wandering, painless, desquamative lesions was observed around the implants and the inner roof of the exenterated socket raising a suspicion of post-radiation osteomyelitis or osteoradionecrosis. Additionally, loss of anchorage of the lateral most implant was observed, eventually leading to its failure (Fig. 3). The resultant defect healed by secondary intention. A Contrast Enhanced Computed Tomography (CECT) revealed normal bone architecture without signs of any pathological deformity (Fig. 4). The patient was maintained on a strict orbital hygiene with local cleaning using 5% povidone iodine wipes. Despite repeated administration of broad-spectrum antibiotics, the lesions had a recurring presentation at multiple new sites. After 6 months of no improvement, the healing abutments were removed and implants were submerged to facilitate healing. The patient responded well, and the lesions gradually healed within three months (Fig. 5). He was further monitored for three more months and was found to be asymptomatic. A conventionally retained orbital prosthesis was chosen to rehabilitate the patient (Fig. 6). Considering the large size of the orbital defect magnetic retention was used between the orbital prosthesis and the hollow bulb of the underlying obturator. The two submerged implants continue to possess sufficient retentive power and remain viable options for future attempts.

Fig. 3.

Multiple scattered necrotic red lesions within the socket. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4.

Contrast Enhanced Computed Tomography (CECT) A. Pre-operative B. One year later revealing normal bone architecture without signs of any pathological deformity.

Fig. 5.

Healing lesions post-submergence of implants.

Fig. 6.

A conventional orbital prosthesis fabricated for the patient, keeping the implants submerged under the soft tissue.

3. Discussion

An orbital prosthesis helps camouflage lost structures and provides a semblance of esthetic, morphological, functional and psychological normality in those affected. The conventional means of anchorage for maxillofacial prosthesis encompass anatomical undercuts, tissue adhesives, double sided tapes, spectacle frames, and magnets.¹ However, the composite nature of the defect, its large size, and the absence of suitable anatomical undercuts in the patient mandated an additional retentive source for a definitive orbital prosthesis. Surgical anchorage by means of osseointegrated craniofacial implants provides a significant advantage in terms of prosthesis retention, stability, placement, and longevity along with improved accessibility for optimal tumor aftercare.² Although the placement of implants in an irradiated orbital bone is debatable, the young age of the patient, his fair general condition, absence of comorbidities and detrimental habits such as smoking were factors in favor of the procedure.

The patient had received 50 Gy (Gy) of fractionated Intensity Modulated Radiation Therapy (IMRT), which delivers a focused beam of high energy photons to the affected area while sparing the adjacent healthy tissues.⁵ Doses having a cumulative value less than 55 Gy are associated with predictable osseointegration while complications are observed at values higher than 65 Gy.⁶ The implants were purposefully planned one year post-radiotherapy to help the bone regain majority of its regenerative capacity and to abate the risk of developing osteoradionecrosis.⁷ A further delay was not favored though because of the perils of progressive endarteritis in irradiated bone.^8,9

The compromised vascularity, slow rate of bone healing, wound dehiscence, and increased proclivity towards infection in an irradiated tissue are impediments to a successful rehabilitation. An imbalance in the osteoclast-osteoblast ratio causes bone resorption to exceed formation thus, affecting the bone quality. Vascular alterations induce tissue hypoxia, hypocellularity, and hypovascularity causing a breakdown in tissue integrity.¹⁰ Hyperbaric oxygen therapy when administered therapeutically at 2.5 atmospheric pressure increases the oxygen plasma content significantly and resolves hypoxia. Healing is promoted by stimulating angiogenesis, fibroblast proliferation, collagen synthesis and crosslinking, and enhancing antimicrobial actions of leukocytes, thus, providing resistance to infections.^{11, 12, 13} At elevated pressure, oxygen acts as a growth factor thereby stimulating osseointegration, increasing the bone implant contact (BIC) and the removal torque needed to pull out titanium implants placed in irradiated bone.^14,15 However, the positive effects of HBO therapy happened to be inadequate in this case, thereby recommending prudence.^{16, 17, 18}

Considering the paramount importance of a gentle surgical technique in recovery of irradiated hard and soft tissues, a guided implant placement protocol was followed.¹⁹ Reverse engineering, using patient's CT data, enabled virtual 3D visualization of the defect. A surgical guide, with minimal extensions, was digitally designed to facilitate precise control over the position, depth and angulations of the implants to be placed.^20,21 Rapid prototyping helped generate a stereolithographic model of the same in real time. The minimal time spent in seating the guide intraoperatively was indicative of its accuracy. Minimal flap reflection, low drill speeds, pre-operative cooling of the drills and saline, use of extensive internal and external irrigation in the first stage surgery followed by deliberate use of tissue punches to expose the implants in the second stage surgery were conscious efforts to protect the bone and soft tissues from mechanical, surgical and thermal insults.

The implants had a rough, sandblasted and acid etched surface to enhance biologic and functional compatibility with the compromised bone.²² The selected dimensions were chosen to help achieve maximum BIC while permitting peri-abutment hygiene maintenance. As per the protocol the normal interval between the first and second stage surgeries is usually three months. However, in this case, considering the compromised circumstances the same was doubled to six months, to give tissues the time to heal and for implants to adequately osseointegrate.¹⁹

Despite the numerous precautions taken and a careful implant bed preparation, the post-second stage period followed an unpredictable course. Prior to the second-stage surgery, the primary surgical site healed nicely without any post-operative complaints. Though studies report failure of osseointegration in irradiated bone by the time of implant exposure, the same was not documented in this case.²³ The implants when exposed during the placement of healing abutments displayed a fair amount of stability with no evidence of loss of bone integrity. The development of multiple diffusely scattered necrotic red lesions was observed after a few weeks and not immediately. A contrast enhanced computed tomography (CECT) also ruled out the suspicion of post-radiation osteomyelitis/osteoradionecrosis. One of the possible explanations could be micromovements around the abutments causing bacterial infiltration of the micro-gap present at the implant-abutment interface causing the inflammatory response. This was further aggravated by patient's post-radiation immunodeficient state. Although the newer implant designs have reduced micro-gap, it is not entirely eliminated, and the passage area persists.²⁴ The post-submergence healing of the ulcers confirmed the same. The implant loss could be because of the altered regenerative ability of the osteoprogenitor cells leading to formation of peri-implant necrotic margin.²⁵ This was replaced by fibrous tissue instead of bone, subsequently causing exfoliation of the implant.

The conventional orbital prosthesis used to rehabilitate the patient though served its fundamental functions had definite drawbacks. Sole dependency on tissue adhesives for retention was not found to be suitable due to the considerable size and composite nature of defect. Furthermore, repeated applications of the adhesive on already friable soft tissue would have been detrimental. The use of a magnetic connection between the orbital prosthesis and obturator bulb resolved this issue. However, this direct connection led to the transfer of dislodging forces to the orbital prosthesis during physiologic functions of mastication, swallowing, and speech thus, making the patient aware of a constant, disturbing motion of the orbital prosthesis. The small area of contact between the orbital prosthesis and the obturator bulb also limited the number and size of the magnets that could be used.

The two remaining implants which were left submerged can serve as a potential solution in future by providing an alternate mode of bony anchorage to the prosthesis from its superior aspect instead of depending on the inferiorly placed obturator. The implants possess sufficient retentive power and attempts can be made again for their successful utilization.

The unfavorable outcome depicts the unique difficulties encountered post-implant placement in irradiated orbital bone and highlights the associated unpredictability despite the adoption of several preventive measures. Reverse engineering and rapid prototyping serve as precise, ergonomic and time-saving tools. However, a better insight into the anticipated tissue response and the presence of an alternative rehabilitative modality to fall back on, in case of a failure, is a necessity while handling such cases.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published, and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

Declaration of competing interest

The authors report no conflict of interest.