Quantitative Assessment of Orbital Implant Position--A Proof of Concept

Does Intraoperative Navigation Improve Implant Position Accuracy in Orbital Fracture Repair?

Purpose: Our aim was to determine if intraoperative navigation (ION) improved radiographic outcomes in patients undergoing delayed primary/secondary orbital reconstruction for inferomedial defects, as measured by volume restoration, enophthalmos correction, and positional accuracy of implants. Patients and Methods: A prospective quasiexperimental study was performed to compare two groups of patients requiring orbital reconstruction. Use of ION was the exposure evaluated. Outcome measures were (i) intraorbital volume and enophthalmos evaluated radiologically, (ii) implant position accuracy, and (iii) procedural duration. Data were analyzed statistically to compare variance between groups. Results: Forty patients (6 females and 34 males) were recruited into the study with a mean age of 27.3 years. The study group demonstrated a greater reduction of intraorbital volume (0.49 cu.cm; p = 0.02) and enophthalmos (0.72 mm; p = 0.001). Implant positioning was more accurate using ION, with less mediolateral (p = 0.006) and yaw (p = 0.04) deviations. Surgical time for implant positioning was shorter by 17 min, with navigation (p < 0.001). Conclusion: The use of ION demonstrated radiographic improvements in volume restoration, enophthalmos correction, as well as accuracy of implant positioning, in patients requiring delayed primary/secondary orbital reconstruction.

Personalized Medicine Workflow in Post-Traumatic Orbital Reconstruction

Restoration of the orbit is the first and most predictable step in the surgical treatment of orbital fractures. Orbital reconstruction is keyhole surgery performed in a confined space. A technology-supported workflow called computer-assisted surgery (CAS) has become the standard for complex orbital traumatology in many hospitals. CAS technology has catalyzed the incorporation of personalized medicine in orbital reconstruction. The complete workflow consists of diagnostics, planning, surgery and evaluation. Advanced diagnostics and virtual surgical planning are techniques utilized in the preoperative phase to optimally prepare for surgery and adapt the treatment to the patient. Further personalization of the treatment is possible if reconstruction is performed with a patient-specific implant and several design options are available to tailor the implant to individual needs. Intraoperatively, visual appraisal is used to assess the obtained implant position. Surgical navigation, intraoperative imaging, and specific PSI design options are able to enhance feedback in the CAS workflow. Evaluation of the surgical result can be performed both qualitatively and quantitatively. Throughout the entire workflow, the concepts of CAS and personalized medicine are intertwined. A combination of the techniques may be applied in order to achieve the most optimal clinical outcome. The goal of this article is to provide a complete overview of the workflow for post-traumatic orbital reconstruction, with an in-depth description of the available personalization and CAS options.

Critical appraisal of patient-specific implants for secondary post-traumatic orbital reconstruction

In orbital reconstruction, a patient-specific implant (PSI) may provide accurate reconstruction in complex cases, since the design can be tailored to the anatomy. Several design options may be embedded, for ease of positioning and precision of reconstruction. This study describes a cohort of 22 patients treated for secondary orbital reconstruction with a PSI; one patient received two PSI. The preoperative clinical characteristics and implant design options used are presented. When compared to preoperative characteristics, the postoperative clinical outcomes showed significant improvements in terms of enophthalmos (P < 0.001), diplopia (P < 0.001), and hypoglobus (P = 0.002). The implant position in all previous reconstructions was considered inadequate. Quantitative analysis after PSI reconstruction showed accurate positioning of the implant, with small median and 90th percentile deviations (roll: median 1.3°, 90th percentile 4.6°; pitch: median 1.4°, 90th percentile 3.9°; yaw: median 1.0°, 90th percentile 4.4°; translation: median 1.4 mm, 90th percentile 2.7 mm). Rim support proved to be a significant predictor of roll and rim extension for yaw. No significant relationship between design options or PSI position and clinical outcomes could be established. The results of this study show the benefits of PSI for the clinical outcomes in a large cohort of secondary post-traumatic orbital reconstructions.

A Multi-Criteria Assessment Strategy for 3D Printed Porous Polyetheretherketone (PEEK) Patient-Specific Implants for Orbital Wall Reconstruction

Pure orbital blowout fractures occur within the confines of the internal orbital wall. Restoration of orbital form and volume is paramount to prevent functional and esthetic impairment. The anatomical peculiarity of the orbit has encouraged surgeons to develop implants with customized features to restore its architecture. This has resulted in worldwide clinical demand for patient-specific implants (PSIs) designed to fit precisely in the patient's unique anatomy. Material extrusion or Fused filament fabrication (FFF) three-dimensional (3D) printing technology has enabled the fabrication of implant-grade polymers such as Polyetheretherketone (PEEK), paving the way for a more sophisticated generation of biomaterials. This study evaluates the FFF 3D printed PEEK orbital mesh customized implants with a metric considering the relevant design, biomechanical, and morphological parameters. The performance of the implants is studied as a function of varying thicknesses and porous design constructs through a finite element (FE) based computational model and a decision matrix based statistical approach. The maximum stress values achieved in our results predict the high durability of the implants, and the maximum deformation values were under one-tenth of a millimeter (mm) domain in all the implant profile configurations. The circular patterned implant (0.9 mm) had the best performance score. The study demonstrates that compounding multi-design computational analysis with 3D printing can be beneficial for the optimal restoration of the orbital floor.

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.

Implant-oriented navigation in orbital reconstruction part II: preclinical cadaver study

In orbital reconstruction, the acquired position of an orbital implant can be evaluated with the aid of intraoperative navigation. Feedback of the navigation system is only obtained after positioning of the implant: the implant's position is not tracked in real time during positioning. The surgeon has to interpret the navigation feedback and translate it to desired adjustments of the implant's position. In a previous study, a real-time implant-oriented navigation approach was introduced and the system's accuracy was evaluated. In this study, this real-time navigation approach was compared to a marker-based navigation approach in a preclinical set-up. Ten cadavers (20 orbital defects) were reconstructed twice, by two surgeons (total: 80 reconstructions). Implant positioning was significantly improved in the real-time implant-oriented approach in terms of roll (2.0° vs. 3.2°, P=0.03), yaw (2.2° vs. 3.4°, P=0.01) and translation (1.3mm vs. 1.8mm, P=0.005). Duration of the real-time navigation procedure was reduced (median 4.5 min vs. 7.5 min). Subjective appreciation of the navigation technique was higher for real-time implant-oriented navigation (mean 7.5 vs. 9.0). Real-time implant-oriented navigation feedback provides real-time, intuitive feedback to the surgeon, which leads to improved implant positioning and shortens duration of the navigation procedure.

Orbital implants: State-of-the-art review with emphasis on biomaterials and recent advances

In the treatment of severe oculo-orbital traumas, intraocular malignancies or other life-threatening conditions it is sometimes necessary to surgically remove the patient's diseased eye. Following the removal of the eye, an orbital implant is inserted into the anophthalmic socket in order to provide satisfactory volume replacement and restore the aesthetic appearance of a normal eye. Over the last decades, the implant design and the criteria of materials selection evolved from simple non-porous polymeric sphere to devices with more complex shape and functionalities for ensuring better clinical outcomes in the long-term. Polymeric and ceramic porous implants have gained prominence since their highly interconnected porous architecture allows them to act as a passive framework for fibrovascular in-growth offering reduced complication rates and the possibility of pegging to enhance the motility of the artificial eye. However, there are still drawbacks to these materials. Some critical aspects of today's orbital implants include the risk of migration and extrusion, postoperative infections and low motility transmitted to the aesthetic ocular prosthesis. Hence, the development of novel biomaterials with enhanced functionalities (e.g. angiogenesis, antibacterial effect, in situ mouldability) which enable an improved outcome of eye replacement is more than ever desirable and represents one of the most challenging topics of research in the field of ocular implants. This review summarizes the evolution of orbital implants and provides an overview of the most recent advances in the field as well as some critical remarks for materials design, selection, characterization and translation to clinical applications.