Innovations in Orbital Surgical Navigation, Orbital Implants, and Orbital Surgical Training

Image-guided orbital surgery: a preclinical validation study using a high-resolution physical model

OBJECTIVE

Preclinical validation study to assess the feasibility and accuracy of electromagnetic image-guided systems (EM-IGS) in orbital surgery using high-fidelity physical orbital anatomy simulators.

METHODS

EM-IGS platform, clinical software, navigation instruments and reference system (StealthStation S8, Medtronic) were evaluated in a mock operating theatre at the Royal Victoria Eye and Ear Hospital, a tertiary academic hospital in Dublin, Ireland. Five high-resolution 3D-printed model skulls were created using CT scans of five anonymised patients with an orbital tumour that previously had a successful orbital biopsy or excision. The ability of ophthalmic surgeons to achieve satisfactory system registration in each model was assessed. Subsequently, navigational accuracy was recorded using defined anatomical landmarks as ground truth. Qualitative feedback on the system was also attained.

RESULTS

Three independent surgeons participated in the study, one junior trainee, one fellow and one consultant. Across models, more senior participants were able to achieve a smaller system-generated registration error in a fewer number of attempts. When assessing navigational accuracy, submillimetre accuracy was achieved for the majority of points (16 landmarks per model, per participant). Qualitative surgeon feedback suggested acceptability of the technology, although interference from mobile phones near the operative field was noted.

CONCLUSION

This study suggests the feasibility and accuracy of EM-IGS in a preclinical validation study for orbital surgery using patient specific 3D-printed skulls. This preclinical study provides the foundation for clinical studies to explore the safety and effectiveness of this technology.

Surgical instrument to improve implant positioning in orbital reconstruction: a feasibility study

Adequate positioning of an orbital implant during orbital reconstruction surgery is essential for restoration of the pre-traumatised anatomy, but visual appraisal of its position is limited by the keyhole access and protruding soft tissues. A positioning instrument that attaches to the implant was designed to provide feedback outside the orbit. The goal of this study was to evaluate the accuracy of placement with the instrument and compare it with the accuracy of placement by visual appraisal. Ten orbits in five human cadaver heads were reconstructed twice: once using visual appraisal and once using the instrument workflow. No significant improvement was found for the roll (5.8° vs 3.4°, respectively, p=0.16), pitch (2.1° vs 1.5°, p=0.56), or translation (2.9 mm vs 3.3 mm, p=0.77), but the yaw was significantly reduced if the instrument workflow was used (15.3° vs 2.9°, p=0.02). The workflow is associated with low costs and low logistical demands, and may prevent outliers in implant positioning in a clinical setting when intraoperative navigation or patient-specific implants are not available.

Nasolacrimal Obstruction Following the Placement of Maxillofacial Hardware

Purpose

This article reviews cases of nasolacrimal obstruction (NLO) secondary to maxillofacial hardware placement.

Methods

A retrospective review was performed at a single institution from 2012 to 2017 of patients with NLO following maxillofacial reconstruction. The study was approved by the Institutional Review Board of the University of California, San Francisco, adhered to the tenets of the Declaration of Helsinki, and was Health Insurance Portability and Accountability Act compliant. Patients were included if external dacryocystorhinostomy (DCR) confirmed previously placed maxillofacial hardware as the primary contributor to lacrimal outflow obstruction and had at least 3 months of follow-up.

Results

Of 420 patients who underwent external DCR, 6 cases of implant-related NLO were identified. The mean age was 47.3 ± 9.6 years and 66.7% of patients were male. All patients presented with epiphora and 50% also had chronic dacryocystitis. Patients had prior maxillofacial hardware placement for paranasal sinus tumors (66.7%) or facial fractures (33.3%). In addition to external DCR, all patients had revision or removal of implants that were impeding lacrimal outflow by 2 mechanisms: (1) an orbital implant impinging the lacrimal sac or nasolacrimal duct (NLD) and/or (2) maxillofacial screws placed into the bony NLD or nasolacrimal fossa. Five of the 6 patients (83.3%) had complete resolution of symptoms and patency of the nasolacrimal system at their last follow-up visit (range 3-30 months).

Conclusion

NLO secondary to hardware placement, though infrequent, is underreported. Two mechanisms of hardware-induced NLO were encountered in this case series. Specific attention to nasolacrimal anatomy at the time of maxillofacial reconstruction may help minimize implant-induced NLO.

Navigation-Assisted Orbital Trauma Reconstruction Using a Bioactive Osteoconductive/Bioresorbable u-HA/PLLA System

Orbital fractures with orbital wall defects are common facial fractures encountered by oral-maxillofacial surgeons, because of the exposed position and thin bony walls of the midface. The primary goal of surgery is to restore the pre-injury anatomy and volume of hard tissue, and to free incarcerated or prolapsed orbital tissue from the fracture by bridging the bony defects with reconstructive implant material and restoring the maxillofacial-orbital skeleton. Numerous studies have reported orbital fracture repair with a wide variety of implant materials that offer various advantages and disadvantages. The ideal orbital implant material will allow conformation to individual patients' anatomical characteristics, remain stable over time, and are radiopaque, especially for the reconstruction of relatively large and/or complex bony walls. Based on these requirements, novel uncalcined and unsintered hydroxyapatite (u-HA) particles and poly-L-lactide (PLLA; u-HA/PLLA) composite sheets could be used as innovative, bioactive, and osteoconductive/bioresorbable implant materials for orbital reconstruction. In addition, intraoperative navigation is a powerful tool. Navigation- and computer-assisted surgeries have improved execution and predictability, allowing for greater precision, accuracy, and minimal invasiveness during orbital trauma reconstructive surgery of relatively complex and large orbital wall defects with ophthalmological malfunctions and deformities. This review presents an overview of navigation-assisted orbital trauma reconstruction using a bioactive, osteoconductive/bioresorbable u-HA/PLLA system.