The accuracy of patient specific implant prebented with 3D-printed rapid prototype model for orbital wall reconstruction

Towards Precision Ophthalmology: The Role of 3D Printing and Bioprinting in Oculoplastic Surgery, Retinal, Corneal, and Glaucoma Treatment

In the forefront of ophthalmic innovation, biomimetic 3D printing and bioprinting technologies are redefining patient-specific therapeutic strategies. This critical review systematically evaluates their application spectrum, spanning oculoplastic reconstruction, retinal tissue engineering, corneal transplantation, and targeted glaucoma treatments. It highlights the intricacies of these technologies, including the fundamental principles, advanced materials, and bioinks that facilitate the replication of ocular tissue architecture. The synthesis of primary studies from 2014 to 2023 provides a rigorous analysis of their evolution and current clinical implications. This review is unique in its holistic approach, juxtaposing the scientific underpinnings with clinical realities, thereby delineating the advantages over conventional modalities, and identifying translational barriers. It elucidates persistent knowledge deficits and outlines future research directions. It ultimately accentuates the imperative for multidisciplinary collaboration to enhance the clinical integration of these biotechnologies, culminating in a paradigm shift towards individualized ophthalmic care.

The Use of Functional Biomaterials in Aesthetic and Functional Restoration in Orbital Surgery

The integration of functional biomaterials in oculoplastic and orbital surgery is a pivotal area where material science and clinical practice converge. This review, encompassing primary research from 2015 to 2023, delves into the use of biomaterials in two key areas: the reconstruction of orbital floor fractures and the development of implants and prostheses for anophthalmic sockets post-eye removal. The discussion begins with an analysis of orbital floor injuries, including their pathophysiology and treatment modalities. It is noted that titanium mesh remains the gold standard for orbital floor repair due to its effectiveness. The review then examines the array of materials used for orbital implants and prostheses, highlighting the dependence on surgeon preference and experience, as there are currently no definitive guidelines. While recent innovations in biomaterials show promise, the review underscores the need for more clinical data before these new materials can be widely adopted in clinical settings. The review advocates for an interdisciplinary approach in orbital surgery, emphasizing patient-centered care and the potential of biomaterials to significantly enhance patient outcomes.

Automatic orbital segmentation using deep learning-based 2D U-net and accuracy evaluation: A retrospective study

The purpose of this study was to verify whether the accuracy of automatic segmentation (AS) of computed tomography (CT) images of fractured orbits using deep learning (DL) is sufficient for clinical application. In the surgery of orbital fractures, many methods have been reported to create a 3D anatomical model for use as a reference. However, because the orbit bone is thin and complex, creating a segmentation model for 3D printing is complicated and time-consuming. Here, the training of DL was performed using U-Net as the DL model, and the AS output was validated with Dice coefficients and average symmetry surface distance (ASSD). In addition, the AS output was 3D printed and evaluated for accuracy by four surgeons, each with over 15 years of clinical experience. One hundred twenty-five CT images were prepared, and manual orbital segmentation was performed in all cases. Ten orbital fracture cases were randomly selected as validation data, and the remaining 115 were set as training data. AS was successful in all cases, with good accuracy: Dice, 0.860 ± 0.033 (mean ± SD); ASSD, 0.713 ± 0.212 mm. In evaluating AS accuracy, the expert surgeons generally considered that it could be used for surgical support without further modification. The orbital AS algorithm developed using DL in this study is extremely accurate and can create 3D models rapidly at low cost, potentially enabling safer and more accurate surgeries.

Is the Pre-Shaping of an Orbital Implant on a Patient-Specific 3D-Printed Model Advantageous Compared to Conventional Free-Hand Shaping? A Systematic Review and Meta-Analysis

This study aimed to perform a systematic review and meta-analysis to compare pre-shaped implants on a patient-specific 3D-printed (3DP) model to manual free-hand shaping (MFS) for orbital wall reconstruction. The PRISMA protocol was followed in this study, and the review was registered in the PROSPERO database (CRD42021261594). A search was conducted in MEDLINE (PubMed), Embase, Cochrane Library, Clinicaltrials.gov, Google Scholar, and the grey literature. Ten articles were included, and six outcomes were analyzed. In total, 281 patients were in the 3DP group and 283 were in the MFS group. The studies had an overall high risk of bias. 3DP models resulted in a better accuracy of fit, anatomical angle reproduction, and defect area coverage. The correction of orbital volume was also superior with statistical significance. There was a higher percentage of the correction of enophthalmos and diplopia in the 3DP group. Intraoperative bleeding and hospital stay were reduced in the 3DP group. The meta-analysis of operative time showed a reduction in the average operative time by 23.58 min (95% CI: -43.98 to -3.19), which was statistically significant (t(6) = -2.8299, p = 0.0300). The 3DP models appear advantageous for an accurate orbital wall reconstruction, with fewer complications than those for conventional free-hand-shaped implants.

Lateral orbital wall reconstruction after basal cell carcinoma penetration—Case report

Advanced periorbital basal cell carcinomas may necessitate orbital exenteration and consequent vision loss, which significantly reduces patients’ life quality. Orbital reconstruction is a demanding surgical procedure due to the complex orbital anatomy and vital structures located in the orbit. In this report, we presented an 83-year-old patient with advanced basal cell carcinoma that had expanded into the orbit. An orbitotomy was performed to remove the tumor completely while preserving the eye function. Orbital reconstruction was performed by a standard surgical method using a titanium mesh modeled according to a natural phantom skull. This maintained the eye function and achieved satisfactory facial esthetics.

Patient-specific Implants for Orbital Fractures: A Systematic Review

PURPOSE

Orbital fractures are common facial fractures that can be challenging to repair and require careful attention to avoid unacceptable ophthalmic complications. Customized implants that are unique to an individual patient, or patient-specific implants (PSIs), have been increasingly used to repair orbital wall fractures. This systematic review summarizes the current evidence regarding custom-made orbital wall implants.

METHODS

A keyword search of published literature from January 2010 to September 2021 was performed using Ovid MEDLINE, PubMed, and the Cochrane Library databases. Original articles that included more than 3 human subjects with an orbital fracture repaired with a PSI were included. The search results were reviewed, duplicates were removed and relevant articles were included for analysis.

RESULTS

Fifteen articles meeting the inclusion criteria. The articles were categorized into 3 separate groups based on the method of PSI fabrication: manual molding of a PSI on a 3D-printed orbital model (53%), directly from a 3D printer (27%), or via a template fabricated from a 3D printer (20%). Three primary postoperative outcomes were assessed: rates of diplopia, enophthalmos, and orbital volume. Postoperative rates of diplopia and enophthalmos improved regardless of the PSI technique, and postoperative orbital volumes were reduced compared with their preoperative state. When PSIs were compared to conventional implants, patient outcomes were comparable.

CONCLUSIONS

This review of existing PSI orbital implant literature highlights that while PSI can accurately and safely repair orbital fractures, patient outcomes are largely comparable to orbital fractures repaired by conventional methods, and PSI do not offer a definitive benefit over conventional implants.

Orbital reconstruction: a systematic review and meta-analysis evaluating the role of patient-specific implants

The purpose of this study is to execute an evidence-based review answering the following question (PICO): "Do patient-specific implants (PSI), manufactured or designed using computer-assisted technology, improve outcomes (orbital volume change, enophthalmos, diplopia, and operative duration) compared to conventional methods in orbital reconstruction following traumatic orbital injury in the adult patient population?" We performed a systematic review and meta-analysis in accordance with PRISMA guidelines. Inclusion criteria included any comparative paper whereby computer-assisted technology was used in the prefabrication or design process of implants for use in post-traumatic orbital reconstruction. Paediatric patient populations were excluded. Eight databases were systematically searched for relevant studies. Risk of bias was assessed through the NOS and RoB2 tools. Random-effects models were used to identify differences in outcomes between groups where possible. Analysis was performed using R 4.0.0. Eleven of 4784 identified studies were included, comprising 628 adult patients, with 302 and 326 patients in the patient-specific and conventional groups, respectively. Weighted mean difference between unaffected and post-operative orbital volume was 0.32 ml (SD 0.75) and 0.95 ml (SD 1.03) for patient-specific and conventional groups, respectively. Significant improvement was identified in post-operative orbital volume reconstitution with the use of PSI, compared to conventional implants, in 3 of the 5 reporting studies. Equally, post-operative enophthalmos trended towards lower severity in the patient-specific group, with 11.2% of patients affected in the patient-specific group and 19.2% in the conventional group, and operative duration was significantly reduced with the use of PSI in 3 of the 6 reporting studies. Despite a tendency to favour PSI, no statistically significant differences in key outcomes were identified on meta-analysis. Although there is some encouraging data to support improved outcomes with the use of patient-specific orbital implants in post-traumatic reconstruction, there is, at present, no statistically significant evidence to objectively support their use over conventional implants based on the currently available comparative studies. Based on the results of this study, the choice of implant used should, thus, be left to the discretion of the surgeon.

Primary reconstruction of extensive orbital fractures using two-piece patient-specific implants: the Helsinki protocol

PURPOSE

We present our experience of titanium-milled two-piece patient-specific implants (PSIs) for primary reconstructions of extensive orbital floor and medial wall fractures (EOFMFs) and evaluate their postoperative functional and aesthetic outcomes in relation to commercially available implants.

METHODS

We included all patients with primary reconstructions (< 22 days from injury) of EOFMFs treated in our department between January 2011 and October 2020. Extensive orbital floor and medial wall fracture was defined as involvement of orbital floor, medial wall and maxilloethmoidal junction; a fracture defect 5 mm or more; defect size more than a third of both inferior and medial walls; and Jaquiéry classification III or more. Patient characteristics, details of fracture defects and surgeries, postoperative outcomes and implant positions were retrospectively evaluated and compared between study groups.

RESULTS

Nineteen patients were included: 5 with two-piece PSIs and 14 with commercial implants. Implant position was good in 4/5 patients with two-piece PSIs and 2/14 with commercial implants. Revision surgery, globe malposition (GMP) > 2 mm, significant diplopia and poor implant position were more frequent in patients with commercial implants than two-piece PSIs. None of the patients with a good overall implant position had any significant postoperative symptoms.

CONCLUSION

Extensive orbital fracture reconstructions are somewhat rare, and surgical treatment is associated with a high rate of complications and postoperative symptoms. Titanium-milled two-piece PSIs are well suited for primary reconstructions of EOFMFs, as they lead to more precise reconstructions and fewer postoperative symptoms than commercially available implants.

Reconstruction of maxillofacial bone defects using patient-specific long-lasting titanium implants

The objective of this retrospective study is to verify the effectiveness and safety of patient-specific titanium implants on maxillofacial bones, with a long-term follow-up. Total 16 patients with various maxillofacial defects underwent reconstruction using patient-specific titanium implants. Titanium implants, manufactured by electron beam melting, selective laser sintering, or milling, were inserted into the maxilla, mandible, or zygoma. Long-term follow‐up (36.7 ± 20.1 months) was conducted after the surgery. Bone fusion of the titanium implant body, postoperative infection, implant malunion, functional results, patient satisfaction, subsidence, osteolysis around the implants, and complications were recorded and analyzed at the last follow-up. Of the 28 implants, only one failed to unite with the bone; therefore, revision surgery was performed. No osteolysis or subsidence around the titanium implants nor adverse events were observed; the mean VAS score for satisfaction was 9. All patients enrolled in this trial were esthetically and functionally satisfied with their surgical results, and fixation failure and esthetic dissatisfaction complications were well resolved. Patient-specific titanium showed satisfactory outcomes when used to treat various oral and maxillofacial defects. A 3D printed titanium implant can be effectively used in the reconstruction of the zygoma and mandible instead of autogenous bone without donor site morbidity.

"6 Anatomical Landmarks" Technique for Satisfactory Free-Hand Orbital Reconstruction With Standard Preformed Titanium Mesh

Study Design

Retrospective study.

Objective

Resolution of clinical signs and symptoms following orbital fractures depends on the accurate restoration of the orbital volume. Computer-Assisted procedures and Patient Specific Implants represent modern solutions, but they require additional resources. A more reproducible option is the use of standard preformed titanium meshes, widely available and cheaper; with their use quality of results is proportional to the accuracy with which they are positioned. This work identifies 6 reproducible and constant anatomical landmarks, as an intraoperative guide for the precise positioning of titanium preformed meshes.

Methods

90 patients treated at the Maxillofacial Surgery Department, Niguarda Trauma Center, Milan, for unilateral orbital reconstruction (January 2012 to December 2018), were studied. In all cases reconstruction was performed respecting the 6 proposed anatomical landmarks. The outcomes analyzed are: post-operative CT adherence to the 6 anatomical markers and symmetry achieved respect to controlateral orbit; number/year of re-interventions and duration of surgery; resolution of clinical defects (at least 12-months follow-up); incidence of complications.

Results

Satisfactory results were obtained in terms of restoration of orbital size, shape and volume. Clinical defects early recovered with a low incidence of complications and re-interventions. Operating times and radiological accuracy have shown a progressive improvement during years of application of this technique.

Conclusions

The proposed "6 anatomical landmarks" is an easy free-hand technique that allows everyone to obtain high levels of reconstructive accuracy and it should be a skill of all surgeons who deal with orbital reconstruction in daily clinical activity.

A Literature Review of Rapid Prototyping and Patient Specific Implants for the Treatment of Orbital Fractures

Post-traumatic reconstruction of the orbit can pose a challenge due to inherent intraoperative problems. Intra-orbital adipose tissue is difficult to manipulate and retract making visualization of the posterior orbital contents difficult. Rapid prototyping (RP) is a cost-effective method of anatomical model production allowing the surgeon to produce a patient specific implant (PSI) which can be pre-surgically adapted to the orbital defect with exact reconstruction. Intraoperative imaging allows immediate assessment of reconstruction at the time of surgery. Utilization and combination of both technologies improves accuracy of reconstruction with orbital implants and reduces cost, surgical time, and the rate of revision surgery.

3D Printing in Eye Care

Three-dimensional printing enables precise modeling of anatomical structures and has been employed in a broad range of applications across medicine. Its earliest use in eye care included orbital models for training and surgical planning, which have subsequently enabled the design of custom-fit prostheses in oculoplastic surgery. It has evolved to include the production of surgical instruments, diagnostic tools, spectacles, and devices for delivery of drug and radiation therapy. During the COVID-19 pandemic, increased demand for personal protective equipment and supply chain shortages inspired many institutions to 3D-print their own eye protection. Cataract surgery, the most common procedure performed worldwide, may someday make use of custom-printed intraocular lenses. Perhaps its most alluring potential resides in the possibility of printing tissues at a cellular level to address unmet needs in the world of corneal and retinal diseases. Early models toward this end have shown promise for engineering tissues which, while not quite ready for transplantation, can serve as a useful model for in vitro disease and therapeutic research. As more institutions incorporate in-house or outsourced 3D printing for research models and clinical care, ethical and regulatory concerns will become a greater consideration. This report highlights the uses of 3D printing in eye care by subspecialty and clinical modality, with an aim to provide a useful entry point for anyone seeking to engage with the technology in their area of interest.

Functional and Cosmetic Outcome after Reconstruction of Isolated, Unilateral Orbital Floor Fractures (Blow-Out Fractures) with and without the Support of 3D-Printed Orbital Anatomical Models

The present study aimed to analyze if a preformed "hybrid" patient-specific orbital mesh provides a more accurate reconstruction of the orbital floor and a better functional outcome than a standardized, intraoperatively adapted titanium implant. Thirty patients who had undergone surgical reconstruction for isolated, unilateral orbital floor fractures between May 2016 and November 2018 were included in this study. Of these patients, 13 were treated conventionally by intraoperative adjustment of a standardized titanium mesh based on assessing the fracture's shape and extent. For the other 17 patients, an individual three-dimensional (3D) anatomical model of the orbit was fabricated with an in-house 3D-printer. This model was used as a template to create a so-called "hybrid" patient-specific titanium implant by preforming the titanium mesh before surgery. The functional and cosmetic outcome in terms of diplopia, enophthalmos, ocular motility, and sensory disturbance trended better when "hybrid" patient-specific titanium meshes were used but with statistically non-significant differences. The 3D-printed anatomical models mirroring the unaffected orbit did not delay the surgery's timepoint. Nonetheless, it significantly reduced the surgery duration compared to the traditional method (58.9 (SD: 20.1) min versus 94.8 (SD: 33.0) min, p-value = 0.003). This study shows that using 3D-printed anatomical models as a supporting tool allows precise and less time-consuming orbital reconstructions with clinical benefits.

Comparison of Nasoseptal Cartilage Graft Versus Titanium Mesh in Reconstruction of Pure Orbital Blowout Fractures

PURPOSE

To compare the efficacy of nasoseptal cartilage grafts versus titanium mesh implants in pure orbital blowout fractures.

METHODS

A retrospective review was performed on 48 patients who had surgical repair of an orbital fracture. Patients who underwent pure orbital blowout fracture repair with either nasoseptal cartilage grafts or titanium mesh implants and at least 1 year postoperative follow-up were included in the study. The clinical features and treatment outcomes were analyzed.

RESULTS

Twenty-five patients fulfilled our study criteria and were included in the analyses. Nasoseptal graft was used in 12 patients (48%) while titanium mesh was preferred in 13 patients (52%). Preoperative clinical features including age, size of the floor defect, and preoperative clinical findings (enophthalmos, diplopia, and restriction of ocular motility) were similar between 2 groups. Mean postoperative follow-up was 14.7 ± 2.3 months in the nasoseptal group while it was 16.1 ± 2.5 months in the titanium group (P = 0.84). Diplopia and ocular motility limitation were resolved in all patients at the last postoperative follow-up visit, while 1 patient in each group had enophthalmos (8.3% versus 7.6%, P = 1.0). No patient in the nasoseptal group experienced postoperative complications while 2 patients in the titanium group (15.3%) developed material-related complications (P = 0.48).

CONCLUSIONS

Long-term clinical results of nasoseptal cartilage grafts and titanium mesh implants in pure orbital blowout fractures with preoperative floor defects smaller than 4 cm2 were comparable. Nasoseptal cartilage grafts may be preferred in patients with septal deviation and no spurs or turbinate hypertrophy.

Sex-related and racial variations in orbital floor anatomy

BACKGROUND

Repair of the orbital floor following trauma or tumor removal remains a challenge because of its complex three-dimensional shape. The purpose of the present study is to understand normal orbital floor anatomy by investigating its differences across four groups (Caucasian American and East Asian, males and females) via facial bone computed tomography (CT).

METHODS

A total of 48 orbits in 24 patients between 20 and 60 years of age were evaluated. Although most patients underwent CT scanning following trauma, the orbital walls were intact in all patients. Linear and angular measurements of the orbital floor were obtained from CT images.

RESULTS

Orbital floor width, length, angle between the orbital floor and medial wall, and distance from the inferior orbital rim to the lowest point of the orbital floor did not show a statistically significant difference between groups. Angles made by the infraorbital rim, the lowest point of the floor, and the anterior border of the infraorbital fissure were statistically significantly wider in East Asian females than in male groups. The floor depth in East Asian females was significantly smaller compared to all the other groups.

CONCLUSION

East Asian female population had smaller curvature and depth of an orbital floor than the other groups, which means racial and sex-related differences should be considered in the orbital floor reconstruction.

Three-Dimensional Analysis of Isolated Orbital Floor Fractures Pre- and Post-Reconstruction with Standard Titanium Meshes and "Hybrid" Patient-Specific Implants

The aim of this study was to compare the efficacy of the intraoperative bending of titanium mesh with the efficacy of pre-contoured “hybrid” patient-specific titanium mesh for the surgical repair of isolated orbital floor fractures. In-house 3D-printed anatomical models were used as bending guides. The main outcome measures were preoperative and postoperative orbital volume and surgery time. We performed a retrospective cohort study including 22 patients who had undergone surgery between May 2016 and November 2018. The first twelve patients underwent conventional reconstruction with intraoperative free-hand bending of an orbital floor mesh plate. The subsequent ten patients received pre-contoured plates based on 3D-printed orbital models that were produced by mirroring the non-fractured orbit of the patient using a medical imaging software. We compared the preoperative and postoperative absolute volume difference (unfractured orbit, fractured orbit), the fracture area, the fracture collapse, and the effective surgery time between the two groups. In comparison to the intraoperative bending of titanium mesh, the application of preformed plates based on a 3D-printed orbital model resulted in a non-significant absolute volume difference in the intervention group (p = 0.276) and statistically significant volume difference in the conventional group (p = 0.002). Further, there was a significant reduction of the surgery time (57.3 ± 23.4 min versus 99.8 ± 28.9 min, p = 0.001). The results of this study suggest that the use of 3D-printed orbital models leads to a more accurate reconstruction and a time reduction during surgery.

Biocompatibility of polyetheretherketone for the treatment of orbital bone defects

AIM

To investigate the biocompatibility and therapeutic effects of polyetheretherketone (PEEK) on recovery of a rabbit orbital defect.

METHODS

Totally 16 New Zealand rabbits were used to establish an orbital bone defect model and then randomly divided into two groups. PEEK was implanted in the experimental group. The control group was blank, and no substance was implanted. The model rabbits were sacrificed at 4 and 8wk, and examined by general observations, histology, electron microscopy, Western blotting, and real-time polymerase chain reaction.

RESULTS

No infection or rejection occurred after PEEK implantation, and biocompatibility was good. The relative expression of vascular endothelial growth factor (VEGF) protein in the experimental group was significantly higher than that in the control group postoperatively (P<0.05). Bone defect repair in the experimental group was significantly better than that in the control group in the same period and some osteogenesis was observed.

CONCLUSION

PEEK has good biocompatibility and efficacy for the treatment of orbital bone defects in a rabbit model.

Complications Following Orbital Floor Repair: Impact of Intraoperative Computed Tomography Scan and Implant Material

Importance: Orbital floor fracture repair is complex and postoperative complications are common. A variety of applicable surgical techniques and technologies are available to surgeons, so data about which of these may decrease postoperative complication rates can help better guide clinical decision making. Objectives: To characterize the patient demographics and surgical techniques utilized in orbital floor fracture repairs at San Antonio Military Medical Center and their relationship with rates of postoperative complications. Design, Setting, and Participants: Retrospective chart review of patients who underwent orbital floor fracture repairs from March 2014 to March 2019 with a mean follow-up time of 1.86 months at a tertiary care academic military hospital and level 1 trauma center. Main Outcomes and Measures: Demographic data, indication for surgical repair, fracture severity, orbital floor approach, implant material, and use of intraoperative computed tomography (CT) scan were recorded. Chi-square analysis was performed to determine the relationship between these factors and postoperative diplopia, hypoglobus, enophthalmos, and infection. Results: A total of 124 procedures were performed during the study period: 71.8% of patients were male and 74% were civilian. Mean age was 39 years (range 19-81). Thirty-one patients were lost to follow-up. The most common approach was transconjunctival (83%), which was most frequently used exclusively (68.5%), but was also combined with cantholysis, transcaruncular, or transantral approach. Postoperative diplopia at follow-up was common (53.8%), resolved after an average of 36.3 days, and was significantly associated with surgical indication of entrapment or revision (p = 0.01) and nonutilization of intraoperative CT (p = 0.04). From 2014 to 2016, intraoperative CT was utilized in 21% of cases and revision rate was 10.5%. From 2017 to 2019, 50% of cases utilized intraoperative CT and revision rate was 2% (p = 0.15). Three cases were revisions performed for abnormal plate position noted on postoperative CT scan. Conclusions and Relevance: A statistically significant association was found between postoperative diplopia, surgical indication of entrapment or revision, and nonutilization of intraoperative CT. Revision rates decreased when use of intraoperative CT increased. Three revision cases may have been prevented by use of an intraoperative CT scan. Patients with entrapment should be counseled regarding the increased risk of postoperative diplopia.

Use of 3D Printed Models to Create Molds for Shaping Implants for Surgical Repair of Orbital Fractures

RATIONALE AND OBJECTIVES

Surgical repair of an isolated orbital fracture requires anatomically accurate implant shape and placement. We describe a three-dimensional (3D) printing technique to customize the shape of commercially available absorbable implants.

MATERIALS AND METHODS

We reviewed our early experience with three cases in which 3D printed molds were utilized for fracture repair. The institution's medical records were reviewed to assess operative time for orbital floor blow-out fracture repairs. Thin section computed tomography (CT) images were loaded into a clinical 3D visualization software, and stereolithography models were created. The models were loaded into stereolithography editing software in which the nonfractured side was mirrored and overlaid with the fractured side. Sterilizable 3D printed molds were created using the fracture images as well as the virtual mirrored images. The molds were taken to the operating room and used to shape a customized orbital implant for fracture repair, using off-the-shelf bioabsorbable implants.

RESULTS

The three patients treated using 3D printed molds had excellent outcomes, with decreased postoperative edema and rapid resolution of ocular misalignment/strabismus. Surgical times were decreased from an average of 93.3 minutes using standard implants to 48.3 minutes following adoption of 3D printed molds.

CONCLUSION

Three-dimensional printed models can be used to create molds for shaping bioabsorbable implants for customized surgical repair, improving fit, reducing tissue handling and postoperative edema, and reducing surgical times.

Orbital floor repair using patient specific osteoinductive implant made by stereolithography

The orbital floor (OF) is an anatomical location in the craniomaxillofacial (CMF) region known to be highly variable in shape and size. When fractured, implants commonly consisting of titanium meshes are customized by plying and crude hand-shaping. Nevertheless, more precise customized synthetic grafts are needed to meticulously reconstruct the patients' OF anatomy with better fidelity. As alternative to titanium mesh implants dedicated to OF repair, we propose a flexible patient-specific implant (PSI) made by stereolithography (SLA), offering a high degree of control over its geometry and architecture. The PSI is made of biodegradable poly(trimethylene carbonate) (PTMC) loaded with 40 wt % of hydroxyapatite (called Osteo-PTMC). In this work, we developed a complete work-flow for the additive manufacturing of PSIs to be used to repair the fractured OF, which is clinically relevant for individualized medicine. This work-flow consists of (i) the surgical planning, (ii) the design of virtual PSIs and (iii) their fabrication by SLA, (iv) the monitoring and (v) the biological evaluation in a preclinical large-animal model. We have found that once implanted, titanium meshes resulted in fibrous tissue encapsulation, whereas Osteo-PMTC resulted in rapid neovascularization and bone morphogenesis, both ectopically and in the OF region, and without the need of additional biotherapeutics such as bone morphogenic proteins. Our study supports the hypothesis that the composite osteoinductive Osteo-PTMC brings advantages compared to standard titanium mesh, by stimulating bone neoformation in the OF defects. PSIs made of Osteo-PTMC represent a significant advancement for patients whereby the anatomical characteristics of the OF defect restrict the utilization of traditional hand-shaped titanium mesh.

Restoration of the inferomedial orbital strut using a standardized three-dimensional printing implant

The inferomedial orbital strut (IOS) is the thin bony junction of the orbital medial wall and floor. Its fracture is common and leads to serious complications, including enophthalmos, globe dystopia and diplopia. However, anatomical restoration of the IOS is challenging owing to reduced structural support; sound anatomical background and accurate implants are therefore essential. The aim of the present study was to incorporate data from cadaveric orbit anatomy into three-dimensional (3D) printing technology and to reconstruct the complex orbital fracture elaborately. After averaging the data from computed tomography (CT) images of 100 adult cadavers, the dimensions of the IOS were extracted, and a tangent sphere was created using a computer-aided design program. The curves were compared with the CT data of 10 adult patients from the simulation test. Based on these data, a standardized 3D implant, 1.15 mm thick, was designed using polycaprolactone. The implant was placed in five patients with complex orbital fractures. The radius of the sphere in contact with the orbit, measuring 33.54 mm, was confirmed to be appropriate. A comparison between the normal side volume (V0) and the postoperative volume (V_post ) showed that they were statistically similar. Furthermore, a comparison between V0 and the preoperative volume (V_pre ), and V_post compared with V_pre also showed a statistically significant difference (P < 0.05). On follow-up, the preoperative ocular symptoms were resolved. The orbital data obtained from 100 cadavers provided standardized orbital anatomy, and 3D printed implants were created. The implants were anatomically accurate with regard to the orbital cavity and adequately covered the simulation model. The implant also showed satisfactory results when applied clinically in actual patients.

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.

Present and future for technologies to develop patient-specific medical devices: a systematic review approach

The main purpose of this investigation was to systematically review the literature regarding case studies on patient-specific implants and devices, with the goal of analyzing the process of developing custom-made medical devices. A content analysis was performed to identify design processes and methodologies implemented to develop devices such as implants adapted to bone geometries. Reverse engineering, computer-aided design, simulation of assets, and rapid prototyping technologies were selected according to their interoperability in a process framework for developing new products. Finally, results from the case studies and process stages identified in the consulted research were analyzed. These results showed a relationship between the scope and complexity of the process and the stage of technology integration of the patient-specific device development. The analyzed case studies were characterized by technical, scientific, and multidisciplinary components to achieve research goals. Likewise, integration of technologies using patient-specific technologies is needed for product development that converges into designing devices, such as implants, biomodels, and cutting drilling guides.

Three-Dimensional Printed Model and Transantral Endoscopy to Orbital Fracture Repair

Orbital fractures are high prevalent and result in several complications such as diplopia, muscular entrapment, visual impairment, and enophthalmos. The goal of orbital reconstruction is to restore orbital anatomy, volume, and globe symmetry. This case report aims to describe the use of transantral endoscopy and 3D printed model for treatment of an orbital floor fracture. A 54-year-old woman presented orbital floor fracture with diplopia and extraocular muscle entrapment. The surgical treatment was performed using a standard titanium mesh bended over 3D printed model, and transantral endoscopy to verify fracture extension and implant adaptation. The postoperative evaluation demonstrates correction of diplopia and ocular motility restriction. Computed tomography scan showed reestablishment of the orbital anatomy. The association of transantral endoscopy and 3D printed models is a feasible technique to improve orbital reconstruction.

The influence of concomitant medial wall fracture on the results of orbital floor reconstruction

INTRODUCTION

Up to 35% of orbital floor fractures extend to the medial wall. This results in restriction of both abduction and adduction, leading to horizontal diplopia. The greater the defect, the more pronounced the enophthalmos.

AIM OF THE STUDY

The aim of the study was to determine the influence of concomitant medial wall defects on enophthalmos and diplopia, and the influence of intraoperative revision on the results of surgical reconstruction in patients with orbital floor fracture.

MATERIAL AND METHODS

78 cases of orbital floor fracture, with or without concomitant medial wall defect, were retrospectively analyzed. Reconstruction surgeries were performed in a similar fashion, but with variation in the alloplastic materials used. Careful investigation of the area was performed during the surgery.

RESULTS

Patients with associated medial wall defects had significantly more pronounced enophthalmos than those with isolated floor fracture, with no such difference after the orbital reconstruction. Postoperative vertical diplopia was more common in patients with an associated medial defect.

CONCLUSIONS

Associated medial wall defect leads to more severe enophthalmos at presentation. However, if the medial aspect of the orbital wall is revised properly, postoperative outcomes are not inferior to those in cases of isolated floor fracture.

Mechanical stress in plates for bridging reconstruction mandibular defects and purposes of double plate reinforcement

PURPOSE

To evaluate the biomechanical performance of a commercially available bridging plate (2.4) as well as screws and bone simulating the reconstruction of hemimandibular defects and to indicate alternatives of reinforcement to prevent plate fractures either by strength or fatigue.

MATERIAL AND METHODS

Two common hemimandibular defects are investigated using computed finite element analysis (FEA) approach. Simplified and refined computational models are developed for the geometry of the screw. Conditions of non-locking and locking plate-screw interfaces are considered. Static loads of 120 N are applied. Von Mises stresses and fatigue are calculated. As reinforcement, a second complete or partial plate is placed onto the original plate.

RESULTS

Results demonstrate that reconstruction plates are often subjected to excessive stress that may lead to fracture either by strength or by fatigue. An attached complete or partial second plate is able to reduce stress in the plate, in screws and bone so that stress remains below the allowable limit of the materials.

CONCLUSION

A simplified technique of attaching a whole or sectioned second plate onto the original plate can reduce the stress calculated and may reduce the frequency of plate fractures for the patient's comfort, security and financial savings.