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BACKGROUND: Surgical treatment of endocrine orbitopathy can be performed by way of resecting orbital walls, which effectively releases superfluous tissue from the surgically enlarged orbital space allowing the eyeballs to move back. Existing approaches aim to select an optimal surgical strategy based on statistical correlations between the extent of the surgical procedure and the resulting bulbus displacement but do not provide an individual surgery plan or predict surgery outcome. METHODS: In this retrospective study, we performed a quantitative analysis of pre- and post-surgery 3D tomographic data of six patients and applied explorative biomechanical modeling of orbital mechanics to dissect factors influencing patient-specific outcome. FINDINGS: Our experimental results showed a large variability of the backward eyeball displacement in dependency on the amount of orbital volume flow, which could partially be described by computational simulation. Our detailed analysis revealed that patients with regular fat tissue show a good correlation between bulbus displacement and relative volume of decompressed tissue, which, in turn, correlates with decrease in hydrostatic pressure. In contrast, patients with fibrotic tissue exhibit significantly reduced and computationally less predictable eyeball translation in response to surgical tissue decompression. INTERPRETATION: Based on the results of this study we see a great potential for quantitative planning of surgical exophthalmos treatment using 3D biomechanical modeling. Conventional approaches to planning of soft tissue interventions consider, however, only the patient's 3D anatomy and widely disregard individual tissue properties. Further investigations are required to establish reliable procedures for assessment of individual tissue properties and incorporating them into patient-specific models of orbital mechanics.

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Following publication of the original article [1], the authors reported that the registration number of the ethics approval was accidentally entered under trial registration. A trial registration was not performed by the authors.

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BACKGROUND: Minimally invasive temporomandibular joint surgery (MITMJS) is an option for patients suffering from severe internal derangement or adhesions. To improve TMJ access, a workflow to create surgical templates is introduced. METHODS: A workflow to generate a dividable patient specific template based on CBCT and optical scanning to access the joint is introduced. In a first clinical trial 3 patients (6 joints) were treated by way of template-guided endoscopically-assisted TMJ therapy (3 arthrocenteses and 3 arthroscopies). RESULTS: Generation and clinical use of the templates was as planned. All templates showed perfect fit and permitted instant access to the TMJ. All surgeries were performed without complications. CONCLUSIONS: Template-guidance could improve the feasibility of endoscopically-assisted TMJ therapy. An important issue is the capability to dis- and remount the template during surgery. Using in-house production, costs are affordable. TRIAL REGISTRATION: This study was registered at the Ethic Committee of the Berlin Medical Chamber ( Eth-30/17 , 12/06/2017).

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PURPOSE: Surgery in endocrine orbitopathy should address exophthalmos and adjunct stigmata such as increased lid aperture and scleral show. Secondary to decompression, rehabilitative surgical treatment such as blepharoplasty is routinely used to achieve this goal. Until now, however, there has been no investigation to measure the effect of decompression surgery on scleral show and lid aperture 3-dimensionally. MATERIALS AND METHODS: Ocular surface area (OSA) and lid aperture of 34 patients (67 orbits) were measured pre and post decompression surgery in a retrospective investigation using 3-dimensional (3D) stereophotogrammetry. The mean follow-up after decompression was 6 ± 4 months. RESULTS: Mean OSA ranged between 3.1 ± 1.5 cm2 (pre orbital decompression) and 2.5 ± 0.6 cm2 (post orbital decompression). Orbital decompression caused a statistically significant reduction of the surface area of about 19.4% (p < 0.001). Lid apertures showed average values between 12.7 ± 3.3 mm (pre orbital decompression) and 11.3 ± 2.2 mm (post orbital decompression). Thus orbital decompression led to a statistically significant reduction of the palpebral fissure of about 11% (p < 0.001). OSA correlated with lid aperture pre and post surgery (p < 0.001). The extent of OSA reduction showed no correlation with the amount of exophthalmos reduction. CONCLUSION: Our results show that surgical decompression, besides correcting exophthalmos, leads to a significant reduction of scleral show and lid aperture. However, it is not possible to estimate its effect on an individual basis.

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PURPOSE: The aim of the study was to analyze the eligibility of resorbable collagen membrane in the treatment of midfacial fractures to prevent gap formation and subsequent cheek tissue retraction. MATERIAL AND METHODS: We included nine patients (six males, three females; mean age 51; range 20-73 years; mean bone gap size 8.03 × 13.12 mm) in a retrospective study design. The defect size was assessed by ultrasound. RESULTS: After a healing period of 4 to 55 weeks, treatment resulted in a significant reduction of gap size (residual mean bone gap size 6.14 × 7.32 mm). CONCLUSIONS: Native resorbable collagen membrane is a promising tool to reduce the size of bony gap in midfacial defects.

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PURPOSE: Orbital wall decompression is routinely used to treat proptosis in endocrine orbitopathy. Until now, however, there has been no investigation to measure the area/extent of the removed walls. MATERIALS AND METHODS: The inner areas of 154 orbital walls (lateral, inferior, medial) which had been resected in 38 patients were measured using pre- and postsurgical computed tomographic data in Brainlab iPlan software. Furthermore the effect of concomitant centrolateral orbital rim advancement was calculated in 48 cases. Surgery was performed after preoperative planning using intraoperative navigation. RESULTS: The mean area of resected inferior and medial orbital walls lay at 6.7 cm2 and 6.2 cm2, while the area of the lateral orbital wall was 6.9 cm2. Rotation-advancement of the lateral rim added an area of 1.8 cm2 (∼25% of the lateral orbital wall). Comparison of the pre- and postsurgical computed tomographic data showed excellent conformity of the presurgical planning and postsurgical results. CONCLUSIONS: This investigation is a first step in analyzing the potential surgical effect of bony decompression surgery by stating the metric amount of orbital wall removal. Using these data, further studies will be performed in the future.

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PURPOSE: In navigated craniomaxillofacial surgery, bone segments often have to be repositioned. To keep them reliably in the desired place during referencing and osteosynthesis, a miniature external distractor can be used. MATERIALS AND METHODS: The use of a miniature external mandibular distractor is shown in a case of bilateral lateral orbital rim advancement during endocrine orbitopathy decompression surgery. RESULTS: The advantages of using a distractor are the possibility of changing the fragment position incrementally in all directions during intraoperative control with the navigated pointer and the small size of the appliance. CONCLUSIONS: Bone segments can be manipulated intraoperatively with a miniature distractor in navigated surgery.

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PURPOSE: This report describes a fully digital workflow for computer-assisted esthetic facial surgery planning and guidance. MATERIAL AND METHODS: Using optical scans, virtual surgery is performed according to the 3-dimensional cephalometric results. Next, surgical templates are generated using rapid prototyping. These templates act as a guide during surgery. RESULTS: The workflow has been tested successfully in 4 esthetic facial surgical procedures (rhinoplasty and genioplasty). In addition to surgical assistance, the advantages of the workflow include the possibility of discussing the treatment plan interactively with the patient and comparing and measuring simulation surgery with the actual outcome. As an additional benefit, the appropriate size of the alloplastic implants can be determined preoperatively. CONCLUSIONS: Templates could improve special procedures in esthetic facial surgery.

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