Individual CAD/CAM Fabricated Glass-Bioceramic Implants in Reconstructive Surgery of the Bony Orbital Floor

Guidelines for Orbital Defect Assessment and Patient-Specific Implant Design: Introducing OA2 (Orbital Assessment Algorithm)

Study Design

This study presents a review of the evolutionary development in reconstructive orbital surgery over the past 3 decades. Additionally, it proposes the Orbital Assessment Algorithm (OA2) to enhance decision-making for intraorbital reconstruction of post-traumatic orbital deformities.

Objective

The objective of this paper is to provide insights into modern post-traumatic orbital reconstruction from a surgeon's perspective, with a specific focus on adult patients. It aims to highlight the advancements in computer-aided design and manufacturing techniques, particularly in the field of reconstructive orbital surgery, and to introduce the OA2 as a tool for improved decision-making in this context.

Methods

The study conducts a comprehensive review of the evolution of reconstructive orbital surgery, focusing on the integration of 3D technology into surgical practices. It also outlines the development and rationale behind the proposed OA2, emphasizing its potential to enhance the accuracy and efficacy of intraorbital reconstruction procedures for post-traumatic deformities.

Results

The review demonstrates the significant progress made in reconstructive orbital surgery, particularly in leveraging 3D technology for virtual modeling, navigation, and the design and manufacturing of patient-specific implants. The introduction of the OA2 provides a structured approach to assessing and addressing post-traumatic orbital deformities, offering potential benefits in decision-making and surgical outcomes.

Conclusions

In conclusion, this paper underscores the pivotal role of computer-aided design and manufacturing in advancing reconstructive orbital surgery. It highlights the importance of integrating innovative design concepts into implant manufacturing processes and emphasizes the potential of the OA2 to guide surgeons in the management of post-traumatic orbital deformities, ultimately contributing to improved patient outcomes.

Advances in Virtual Cutting Guide and Stereotactic Navigation for Complex Tumor Resections of the Sacrum and Pelvis: Case Series with Short-Term Follow-Up

Primary malignancies of the sacrum and pelvis are aggressive in nature, and achieving negative margins is essential for preventing recurrence and improving survival after en bloc resections. However, these are particularly challenging interventions due to the complex anatomy and proximity to vital structures. Using virtual cutting guides to perform navigated osteotomies may be a reliable method for safely obtaining negative margins in complex tumor resections of the sacrum and pelvis. This study details the technique and presents short-term outcomes. Patients who underwent an en bloc tumor resection of the sacrum and/or pelvis using virtual cutting guides with a minimum follow-up of two years were retrospectively analyzed and included in this study. Preoperative computer-assisted design (CAD) was used to design osteotomies in each case. Segmentation, delineating the tumor from normal tissue, was performed by the senior author using preoperative CT scans and MRI. Working with a team of biomedical engineers, virtual surgical planning was performed to create osteotomy lines on the preoperative CT and overlaid onto the intraoperative CT. The pre-planned osteotomy lines were visualized as "virtual cutting guides" providing real-time stereotactic navigation. A precision ultrasound-powered cutting tool was then integrated into the navigation system and used to perform the osteotomies in each case. Six patients (mean age 52.2 ± 17.7 years, 2 males, 4 females) were included in this study. Negative margins were achieved in all patients with no intraoperative complications. Mean follow-up was 38.0 ± 6.5 months (range, 24.8-42.2). Mean operative time was 1229 min (range, 522-2063). Mean length of stay (LOS) was 18.7 ± 14.5 days. There were no cases of 30-day readmissions, 30-day reoperations, or 2-year mortality. One patient was complicated by flap necrosis, which was successfully treated with irrigation and debridement and primary closure. One patient had local tumor recurrence at final follow-up and two patients are currently undergoing treatment for metastatic disease. Using virtual cutting guides to perform navigated osteotomies is a safe technique that can facilitate complex tumor resections of the sacrum and pelvis.

Technical considerations of computer-aided planning in severe orbital trauma: A retrospective study

The aim of this study was to evaluate the clinical outcomes of linear and orbital volume measurements in severe orbital trauma. Patients with severe orbital trauma that involved more than two walls and entailed a marked degree of comminution were included in this retrospective analysis. However, patients with incomplete clinical records and a simple blowout or zygmatico-orbital fractures were excluded. All the cases underwent surgical correction guided by virtual surgical planning and 3D-printed templates. The measurement protocol depended on assessing orbital dimensions, orbital volumetry, and the zygomatic bone's position in the three-dimensional planes. All patients' preoperative 3D CT scans were obtained, and DICOM files were imported into a three-dimensional image processing software. Data were then converted for 3D reconstruction in the axial, coronal, and sagittal views. A total of 18 patients with a mean age was 39.28 ± 6.28 were included in this study. The results revealed a significant difference between the pre and postoperative differences in distances in relation to the FHP (Frankfurt Horizontal Plane) (P = 0.0014) and sagittal planes (P < 0.0001). The orbital width and height of the traumatized orbit were significantly decreased from 45.26 ± 6.72 mm and 45.30 ± 2.89 mm to 39.74 ± 3.91 mm (P = 0.0022), and 40.34 ± 0.86 mm (P < 0.0001), respectively. Clinically, there was a satisfactory degree of symmetry regarding the zygomatic bones' position and orbital dimensions postoperatively. Moreover, the mean orbital volume on the traumatized side decreased significantly from 23.16 ± 1.91 cm³ preoperatively to 20.7 ± 1.96 cm³ postoperatively (P < 0.0001). These findings were associated with a low incidence of complications. Within the limitations of the study it seems that the described methodology is a relevant addition to clinical treatment options. It incorporates all the latest technology to plan virtual reconstruction surgery in the treatment of complex orbital trauma and should be adapted accordingly in cases of severe displacement and comminution.

Calcium Orthophosphate (CaPO4)-Based Bioceramics: Preparation, Properties, and Applications

Various types of materials have been traditionally used to restore damaged bones. In the late 1960s, a strong interest was raised in studying ceramics as potential bone grafts due to their biomechanical properties. A short time later, such synthetic biomaterials were called bioceramics. Bioceramics can be prepared from diverse inorganic substances, but this review is limited to calcium orthophosphate (CaPO4)-based formulations only, due to its chemical similarity to mammalian bones and teeth. During the past 50 years, there have been a number of important achievements in this field. Namely, after the initial development of bioceramics that was just tolerated in the physiological environment, an emphasis was shifted towards the formulations able to form direct chemical bonds with the adjacent bones. Afterwards, by the structural and compositional controls, it became possible to choose whether the CaPO4-based implants would remain biologically stable once incorporated into the skeletal structure or whether they would be resorbed over time. At the turn of the millennium, a new concept of regenerative bioceramics was developed, and such formulations became an integrated part of the tissue engineering approach. Now, CaPO4-based scaffolds are designed to induce bone formation and vascularization. These scaffolds are usually porous and harbor various biomolecules and/or cells. Therefore, current biomedical applications of CaPO4-based bioceramics include artificial bone grafts, bone augmentations, maxillofacial reconstruction, spinal fusion, and periodontal disease repairs, as well as bone fillers after tumor surgery. Prospective future applications comprise drug delivery and tissue engineering purposes because CaPO4 appear to be promising carriers of growth factors, bioactive peptides, and various types of cells.

Clinical outcome of patients with orbital fractures treated with patient specific CAD/CAM ceramic implants - A retrospective study

The aim of this study was to determine whether patients benefit from a secondary reconstruction since it carries the risks of no improvement or worsening of their current situation. Patients treated with individual computer-aided-design/computer-aided-manufacturing (CAD/CAM) ceramic implants were reviewed. To ascertain changes throughout the secondary reconstruction, the study investigators reviewed ophthalmological examinations, took volumetric measurements of the orbits and asked the patients for evaluation of their situation before and after the reconstruction. Points addressed were double vision, visual acuity, field of vision, limitations in daily life and aesthetic considerations. A total of 14 patients were reviewed and 11 answered the questionnaire. Ophthalmological examinations showed that the physical integrity of the eye was maintained. Volumetric measurements preopeatively (33.94 ± 3.24 cm³) and postoperatively (30.67 ± 2.07 cm³) showed that a statistically significant overcorrection of orbital volume leads to good functional and aesthetic outcomes. Patients' subjective opinions were that they greatly benefitted, especially concerning limitations in daily life, which improved by 4.4 ± 2.8 points out of 10 possible points, and aesthetics, with an improvement of 5.9 ± 1.78 points. Based on these findings, we conclude that secondary reconstructions contribute to improvement of the patients' quality of life and therefore should be considered as an option to improve patients' condition.

Custom-Made Zirconium Dioxide Implants for Craniofacial Bone Reconstruction

Reconstruction of the facial skeleton is challenging for surgeons because of difficulties in proper shape restoration and maintenance of the proper long-term effect. ZrO₂ implant application can be a solution with many advantages (e.g., osseointegration, stability, and radio-opaqueness) and lacks the disadvantages of other biomaterials (e.g., metalosis, radiotransparency, and no osseointegration) or autologous bone (e.g., morbidity, resorption, and low accuracy). We aimed to evaluate the possibility of using ZrO₂ implants as a new application of this material for craniofacial bone defect reconstruction. First, osteoblast (skeleton-related cell) cytotoxicity and genotoxicity were determined in vitro by comparing ZrO₂ implants and alumina particle air-abraded ZrO₂ implants to the following: 1. a titanium alloy (standard material); 2. ultrahigh-molecular-weight polyethylene (a modern material used in orbital surgery); 3. a negative control (minimally cytotoxic or genotoxic agent action); 4. a positive control (maximally cytotoxic or genotoxic agent action). Next, 14 custom in vivo clinical ZrO₂ implants were manufactured for post-traumatologic periorbital region reconstruction. The soft tissue position improvement in photogrammetry was recorded, and clinical follow-up was conducted at least 6 years postoperatively. All the investigated materials revealed no cytotoxicity. Alumina particle air-abraded ZrO2 implants showed genotoxicity compared to those without subjection to air abrasion ZrO₂, which were not genotoxic. The 6-month and 6- to 8-year clinical results were aesthetic and stable. Skeleton reconstructions using osseointegrated, radio-opaque, personalized implants comprising ZrO₂ material are the next option for craniofacial surgery.

Computer-Aided Design and Manufacture of Intraoral Splints: A Potential Role in Cleft Care

BACKGROUND

Nasoalveolar molding is a nonsurgical modality for the treatment of cleft lip and palate that uses an intraoral splint to align the palatal shelves. Repeated impressions are needed for splint modification, each carrying risk of airway obstruction. Computer-aided design and manufacturing (CAD/CAM) has the ability to simplify the process. As a precursor to CAD/CAM splint fabrication, a proof-of-concept study was conducted to compare three-dimensional splints printed from alginate impressions versus digital scans. We hypothesized that intraoral digital scanning would compare favorably to alginate impressions for palate registration and subsequent splint manufacture, with decreased production times.

METHODS

Alginate and digital impressions were taken from 25 healthy teenage volunteers. Digital impressions were performed with a commercially available intraoral scanner. Plaster casts made from alginate impressions were converted to Standard Triangle Language files. Patient-specific matched scans were evaluated for total surface area with the concordance correlation coefficient. Acrylic palatal splints were three-dimensionally printed from inverse digital molds. Subjective appliance fit was assessed using a five-point scale.

RESULTS

A total of 23 participants were included. Most subjects preferred digital impression acquisition. Impression methods showed moderate agreement (concordance correlation coefficient 0.93). Subjects rated splints from digital impressions as having a more precise fit (4.4 versus 3.9). The digital approach decreased impression phase time by over 10-fold and overall production time by 28%.

CONCLUSIONS

CAD/CAM has evolved extensively over the past two decades and is now commonplace in medicine. However, its utility in cleft patients has not been fully realized. This pilot study demonstrated that CAD/CAM technologies may prove useful in patients requiring intraoral splints.

Overview of tools for the measurement of the orbital volume and their applications to orbital surgery

There are numerous applications in craniofacial surgery with orbital volume (OV) modification. The careful management of the OV is fundamental to obtain good esthetic and functional results in orbital surgery. With the growth of computer-aided design - computer-aided manufacturing (CAD-CAM) technologies, patient-specific implants and custom-made reconstruction are being used increasingly. The precise measurement of the OV before surgery is becoming a necessity for craniofacial surgeons. There is no consensus on orbital volume measurements (OVMs). Manual segmentation of computed tomography (CT) images is the most used method to determine the OV, but it is time-consuming and very sensitive to operator errors. Here, we describe the various methods of orbital volumetry validated in the literature that can be used by surgeons in preoperative planning of orbital surgery. We also describe the leading software employed for these methods and discuss clinical use (posttraumatic enophthalmos prediction and orbital reconstruction) in which OVMs are important.

Single-Step Resection of Sphenoorbital Meningiomas and Orbital Reconstruction Using Customized CAD/CAM Implants

Objective  Computer-aided design and manufacturing (CAD/CAM) implants are fabricated based on volumetric analysis of computed tomography (CT) scans and are routinely used for the reconstruction of orbital fractures. We present three cases of patients with sphenoorbital meningiomas that underwent tumor resection, orbital decompression, and orbital reconstruction with patient specific porous titanium or acrylic implants in a single procedure. Methods  The extent of bone resection of the sphenoorbital meningiomas was planned in a virtual three-dimensional (3D) environment using preoperative thin-layer CT data. The anatomy of the orbital wall in the resection area was reconstructed by superimposing the contralateral unaffected orbit and by using the information of the neighboring bony structures. The customized implants and a corresponding craniotomy template were designed in the desired size and shape by the manufacturer. Results  All patients presented with a sphenoorbital meningioma and exophthalmos. After osteoclastic craniotomy with the drilling template, orbital decompression was performed. Implant fitting was tight in two cases and could be easily fixated with miniplates and screws. In the third patient, a reoperation was necessary for additional bone resection, as well as drilling and repositioning of the implant. The postoperative CT scans showed an accurate reconstruction of the orbital wall. After surgery, exophthalmos was substantially reduced and a satisfying cosmetic result could be finally achieved in all patients. Conclusions  The concept of preoperative 3D virtual treatment planning and single-step orbital reconstruction with CAD/CAM implants after tumor resection involving the orbit is well feasible and can lead to good cosmetic results.

Updates in Head and Neck Reconstruction

LEARNING OBJECTIVES

After reading this article, the participant should be able to: 1. Have a basic understanding of virtual planning, rapid prototype modeling, three-dimensional printing, and computer-assisted design and manufacture. 2. Understand the principles of combining virtual planning and vascular mapping. 3. Understand principles of flap choice and design in preoperative planning of free osteocutaneous flaps in mandible and midface reconstruction. 4. Discuss advantages and disadvantages of computer-assisted design and manufacture in reconstruction of advanced oncologic mandible and midface defects.

SUMMARY

Virtual planning and rapid prototype modeling are increasingly used in head and neck reconstruction with the aim of achieving superior surgical outcomes in functionally and aesthetically critical areas of the head and neck compared with conventional reconstruction. The reconstructive surgeon must be able to understand this rapidly-advancing technology, along with its advantages and disadvantages. There is no limit to the degree to which patient-specific data may be integrated into the virtual planning process. For example, vascular mapping can be incorporated into virtual planning of mandible or midface reconstruction. Representative mandible and midface cases are presented to illustrate the process of virtual planning. Although virtual planning has become helpful in head and neck reconstruction, its routine use may be limited by logistic challenges, increased acquisition costs, and limited flexibility for intraoperative modifications. Nevertheless, the authors believe that the superior functional and aesthetic results realized with virtual planning outweigh the limitations.

Mechanical resistance of the periorbita and the orbital floor complex--are isolated orbital floor fractures only a soft tissue problem?

The primary aims of orbital floor reconstruction are to prevent enophthalmos and herniation of the orbital contents in order to achieve correct globe position. Theoretically, the mechanical load of the orbital floor is approximately 0.0005N/mm(2) (30g orbital content onto 600mm(2) of orbital floor area). Therefore, low mechanical stress from orbital floor reconstruction materials is expected. The periorbita and orbital floor complex (bony orbital floor with periorbita) of 12 human cadavers were investigated for their mechanical resistance to distortion and compared to different absorbable pliable reconstruction materials after modification with pores (Bio-Gide, Creos, and PDS). The human periorbita resistance (approximately 1.4N/mm(2)) was comparable to that of the absorbable membranes (Creos, Bio-Gide), and the resistance of PDS (approximately 2.3N/mm(2)) was comparable to that of the orbital floor complex. The periorbita has a higher stability than the bony orbital floor. Therefore, in isolated orbital floor fractures with a traumatized bony orbital floor and periorbita, reconstruction of the soft tissue as a periorbita equivalent with a resorbable membrane appears to be adequate to prevent enophthalmos and herniation of the orbital contents.

Management of orbital fractures: challenges and solutions

Many specialists encounter and treat orbital fractures. The management of these fractures is often challenging due to the impact that they can have on vision. Acute treatment involves a thorough clinical examination and management of concomitant ocular injuries. The clinical and radiographic findings for each individual patient must then be analyzed for the need for surgical intervention. Deformity and vision impairment can occur from these injuries, and while surgery is intended to prevent these problems, it can also create them. Therefore, surgical approach and implant selection should be carefully considered. Accurate anatomic reconstruction requires complete assessment of fracture margins and proper implant contouring and positioning. The implementation of new technologies for implant shaping and intraoperative assessment of reconstruction will hopefully lead to improved patient outcomes.

Mechanical properties of collagen membranes modified with pores--are they still sufficient for orbital floor reconstruction?

Adequate mechanical strength is essential for materials used to reconstruct the orbital floor, and collagen membranes have recently been suggested for the repair of isolated fractures of the orbital floor. However, their mechanical properties after modification with pores for increased drainage of blood into the sinus have not been sufficiently investigated. We have tested the mechanical resistance of polydioxanone foils (PDS) to distortion and compared it with that of 3 resorbable collagen membranes (Smartbrane(®), Bio-Gide(®), and Creos(®)) in mint condition and when artificially aged (3 weeks, 6 weeks, and 8 weeks) after modification with pores (diameter 2mm) in a standard configuration (n=12 in each group). PDS and Creos(®) had comparable initial values for mechanical resistance of about 2.3N/mm(2), and Bio-Gide(®) and Smartbrane(®) had about 20% and 80% lower initial mechanical resistance, respectively. All materials tested had lower values after artificial ageing. After eight weeks of ageing, PDS lost about 99% of its initial mechanical resistance, Creos(®) about 66%, Bio-Gide(®) about 30%, and Smartbrane(®) about 95%. After 3 weeks the mechanical resistance in all groups was significantly less than the initial values (p=0.05), but there was no difference between samples aged artificially for 6 compared with 8 weeks. The mechanical resistance of the tested materials was not influenced by the presence of pores in a standard configuration and was in the appropriate range for moderate fractures of the orbital floor. We recommend further clinical investigations of collagen membranes modified with pores.

A new option for the reconstruction of orbital floor defects with heterologous cortical bone

BACKGROUND

The orbital floor is one of the most frequently injured areas of the maxillofacial skeleton during facial trauma. A retrospective analysis of patients who have undergone treatment of orbital floor fractures with heterologous cortical bone is presented.

METHODS

This retrospective study was carried out with 21 patients over a period of 4 years between 2010 and 2014. All patients with a traumatic orbital floor defect who underwent reconstruction with heterologous cortical bone were included. The operations were carried out under general anesthesia for all patients. A subciliary incision was used in 20 patients and an infraorbital approach was used in one patient. All patients underwent follow-up examinations clinically as well as radiologically, at 1, 3, 6 and 12 months postoperatively. Computed tomographic scans were taken at the postoperative 6th month, and at the first postoperative year if needed.

RESULTS

Preoperatively, the physical examination revealed diplopia in 17 patients (80.9%), gaze restriction in 14 patients (66.6%), enophthalmos in six patients (28.5%), and infraorbital nerve paresthesia in two patients (9.5%). None of the patients showed impaired visual acuity preoperatively or postoperatively. Diplopia and gaze restriction resolved postoperatively in all of the patients. All patients had a negative intraoperative forced duction test demonstrating free globe movement. Enophthalmos showed complete resolution in the postoperative period. In one of the two patients with preoperative infraorbital nerve paresthesia, this resolved at the postoperative fifth month. Scleral show appeared in six patients but resolved completely within 3-8 weeks with massage. There was no graft extrusion, resorption or displacement during the follow-up period.

CONCLUSIONS

Tecnoss Semi Soft Lamina is a good alternative for the reconstruction of blowout fractures due to its plasticity and biocompatible structure. Without donor site morbidity, it is a safe and appropriate heterologous bone graft material for maxillofacial applications such as orbital floor reconstruction. We cannot recommend its use for near-total, wide orbital floor defects as it may not provide enough support in such circumstances.

The use of anatomically drop-shaped bioactive glass S53P4 implants in the reconstruction of orbital floor fractures--A prospective long-term follow-up study

An isolated fracture of the orbital floor needs reconstruction if there is a clear herniation of adipose tissue or of the rectus inferior muscle into the maxillary sinus. A prospective study was carried out treating 20 patients with an isolated blow-out fracture of the orbital floor or with a combined zygomatico-orbito-maxillary complex fracture, using a newly designed anatomically drop-shaped implants made of bioactive glass (BAG) S53P4. Computed tomography (CT) was performed immediately postoperatively to confirm the correct position of the plate. The patients were followed up for an average of 32 months clinically and radiologically with magnetic resonance imaging (MRI) for an average of 31 months. None of the patients had any signs of complications related to the implant and the clinical outcome was very good. None of the patients had persisting diplopia. The level of the pupillas was normal in 15 of 20 patients. Minor hypo-ophthalmos ranging from 0.5 to 1.0 mm was observed in three patients, and moderate hypo-ophthalmos of 2.0 mm was seen in one patient. Hyperophthalmos of 1.0 mm was seen in one patient. Minor enophthalmos on the operated side ranging from 0.5 to 1.0 mm was seen in eight patients. Mild to moderate paraesthesia of the infraorbital nerve was observed in six patients. The immediate postoperative CT and the long term follow-up MRI revealed that the drop-shaped BAG implants retained their correct position in the orbital floor and did not show any evidence of losing their original shape or material resorption. No adverse tissue reaction was associated with the material. Due to the anatomical drop shape, the implants could successfully maintain the orbital volume and compensate for the retrobulbar adipose tissue atrophy.

Rapid prototyped patient specific implants for reconstruction of orbital wall defects

Defects of orbital walls can be reconstructed using implants. The authors report a safe and accurate method to reconstruct bone defects in the orbital area using patient specific implants. A detailed process description of computer aided design (CAD) reconstructive surgery (CRS) is introduced in this prospective study. The 3D volumetric virtual implant was design using MSCT data and PTCProEngineer™ 3D software. The intact orbital cavity of twelve patients was mirrored to the injured side. Specific ledges steered the implant into correct place. Postoperatively the position was assessed using image fusion. One implant (8%) was rejected due to chemical impurities, two (16%) had a false shape due to incorrect CAD. Data of thin bone did not transfer correctly to CAD and resulted in error. One implant (8%) was placed incorrectly. Duration of the CRS was in average 1.17 h, correspondingly 1.57 h using intraoperative bending technique. The CRS process has several critical stages, which are related to converting data and to incompatibility between software. The CRS process has several steps that need further studies. The data of thin bone may be lost and disturb an otherwise very precise technique. The risk of incorporating impurities into the implant must be carefully controlled.

3D modeling, custom implants and its future perspectives in craniofacial surgery

Custom implants for the reconstruction of craniofacial defects have gained importance due to better performance over their generic counterparts. This is due to the precise adaptation to the region of implantation, reduced surgical times and better cosmesis. Application of 3D modeling in craniofacial surgery is changing the way surgeons are planning surgeries and graphic designers are designing custom implants. Advances in manufacturing processes and ushering of additive manufacturing for direct production of implants has eliminated the constraints of shape, size and internal structure and mechanical properties making it possible for the fabrication of implants that conform to the physical and mechanical requirements of the region of implantation. This article will review recent trends in 3D modeling and custom implants in craniofacial reconstruction.

Calcium Orthophosphate-Based Bioceramics

Various types of grafts have been traditionally used to restore damaged bones. In the late 1960s, a strong interest was raised in studying ceramics as potential bone grafts due to their biomechanical properties. A bit later, such synthetic biomaterials were called bioceramics. In principle, bioceramics can be prepared from diverse materials but this review is limited to calcium orthophosphate-based formulations only, which possess the specific advantages due to the chemical similarity to mammalian bones and teeth. During the past 40 years, there have been a number of important achievements in this field. Namely, after the initial development of bioceramics that was just tolerated in the physiological environment, an emphasis was shifted towards the formulations able to form direct chemical bonds with the adjacent bones. Afterwards, by the structural and compositional controls, it became possible to choose whether the calcium orthophosphate-based implants remain biologically stable once incorporated into the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of regenerative bioceramics was developed and such formulations became an integrated part of the tissue engineering approach. Now calcium orthophosphate scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous and harbor different biomolecules and/or cells. Therefore, current biomedical applications of calcium orthophosphate bioceramics include bone augmentations, artificial bone grafts, maxillofacial reconstruction, spinal fusion, periodontal disease repairs and bone fillers after tumor surgery. Perspective future applications comprise drug delivery and tissue engineering purposes because calcium orthophosphates appear to be promising carriers of growth factors, bioactive peptides and various types of cells.

Calcium orthophosphates as bioceramics: state of the art

In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30-40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics-which is able to promote regeneration of bones-was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes.

Bone regeneration with glass ceramic implants and calcium phosphate cements in a rabbit cranial defect model

Hydroxyapatite cement (BoneSource®) and brushite calcium phosphate cement (chronOS™ Inject) were tested for fixation of glass ceramic implants (Bioverit®) in experimentally created cranial defects in 24 adult New Zealand White rabbits. Aim of the in vivo study was to assess and compare the biocompatibility and osseointegration of the implanted materials. Macroscopic and histological evaluations were performed 1 month, 3 months, and 6 months postoperatively. All implanted materials were well tolerated by the surrounding tissue. Both bone cements exhibited osteoconductive properties. Differences could be detected regarding to the rates of cement resorption and new bone formation. The brushite cement was resorbed faster than the hydroxyapatite cement. The chronOS™ Inject samples exhibited a higher rate of connective tissue formation and an insufficient osseointegration. BoneSource® was replaced by bone with minimal invasion of connective tissue. New bone formation occurred faster compared to the chronOS™ Inject group. Bioverit® implants fixed with BoneSource® were successfully osseointegrated.

[Reconstruction of the cranial vault using CAD/CAM-fabricated glass bioceramic implants]

BACKGROUND AND PURPOSE

Reconstruction of a cranial vault after craniectomy is an esthetic and functional challenge. The quest for the ideal implant that would mimic an original bone graft has tested many materials such as bone implants and artificial substitutes. The aim of this multicenter study was to report a set of preliminary results of cranioplasty using bioceramic implants made of Bioverit® II.

METHODS

In this retrospective study, we attempted to assess the esthetic results of prefabricated Bioverit® II prostheses and to determine their performance in reducing operating time and surgical complications in delayed cranioplasty.

RESULTS

Within a 3-year period, 16 patients from four French university hospitals underwent cranial reconstruction using this technique. The results were encouraging, with all patients showing a good esthetic outcome. Hospital length of stay after surgery was short (median, 5.5 days). One prosthesis had to be reshaped during surgery. Only one patient experienced superficial wound infection successfully treated without removing the material.

CONCLUSIONS

CAD/CAM-fabricated Bioverit® II prostheses are a good alternative when autologous bone is not available. Fabrication of bioceramic prostheses using this method requires surgical scheduling, which is justified by the following advantages: reduced operating time, lack of donor morbidity, good esthetic results, and stability. The only drawback of this material is its price, which can limit its deployment.

Evaluation of the application of computer-aided shape-adapted fabricated titanium mesh for mirroring-reconstructing orbital walls in cases of late post-traumatic enophthalmos

PURPOSE

Computer-aided individually shape-adapted fabricated titanium mesh for the mirroring-reconstruction of the orbit is a promising method for the correction of post-traumatic enophthalmos. The purpose of this study was to evaluate the application of this technique and assess the treatment outcomes.

PATIENTS AND METHODS

Twenty-one patients with delayed treatment of unilateral impure orbital fracture and post-traumatic enophthalmos were included in this study. Computed tomography-based mirroring-reconstruction images of the orbit were obtained for each individual to fabricate anatomically adaptive titanium mesh by computer-aided design and computer-aided manufacturing techniques. After exposing the areas of orbital defect and reducing the herniated soft tissue, the titanium mesh was inserted to reconstruct the internal orbit with a mean deep extension of 29.33 mm. Measurements were performed to assess the change in the degree of enophthalmos and orbital volume before and after surgery. Paired samples t test and Pearson correlation coefficient were employed for statistical analysis.

RESULTS

Follow-up examinations revealed that the degree of enophthalmos decreased to less than 2 mm in 11 patients, 2 to 4 mm in 9 patients, and remained greater than 7 mm in 1 patient. Statistical analysis revealed that post-traumatic enophthalmos in this series was 4.05 +/- 2.02 mm, which was associated with an orbital volume increment of 6.61 +/- 3.63 cm(3), with a regression formula of enophthalmos = 0.446 x orbital volume increment + 2.406. Orbital reconstruction effected a orbital volume decrease of 4.24 +/- 2.41 cm(3) and enophthalmos correction of 2.01 +/- 1.46 mm, the regression formula being enophthalmos = 0.586 x orbital volume decrease + 0.508. After surgery, the degree of unresolved enophthalmos was 2.03 +/- 1.52 mm, and the retained orbital volume expansion was 2.23 +/- 2.86 cm(3), and the regression formula was enophthalmos = 0.494 x orbital volume expansion + 1.415.

CONCLUSION

Application of the individual fabricated titanium mesh for orbital reconstruction reduced the trauma-induced orbital volume increment by 65% and corrected 50% of severe late enophthalmos. Additional augmentation of orbital contents was required for further correction. The related treatment parameters were suggested.

Rapid prototyped PGA/PLA scaffolds in the reconstruction of mandibular condyle bone defects

BACKGROUND

Craniomaxillofacial bone defects are currently reconstructed by using computer-aided design and manufacturing (CAD/CAM) processes. We have developed a novel digital medical support system that enables us to custom-make scaffolds to repair craniomaxillofacial bone defects using three-dimensional computed tomographic (CT) images and a rapid-prototyping method.

METHODS

We created positive molds using CT data, CAD/CAM and a rapid prototyping method using 3D printing. Custom-made poly (glycolic acid) (PGA) and polymers poly (lactic acid) (PLA) scaffolds were prefabricated by a positive-negative mold interchange technique. A laser scanning system was used to evaluate the accuracy of the PGA/PLA scaffold. Bone marrow stem cells were incubated with the scaffold to assess biocompatibility.

RESULTS

The mean error was <0.3 mm and confidence was >or=95% when the error was <1 mm. Results from in vitro cell culture demonstrated that the PGA/PLA scaffold had excellent cellular compatibility.

CONCLUSIONS

This pilot study suggests that custom-made PGA/PLA scaffolds infiltrated with bone marrow stem cells may be effective for future treatment of craniomaxillofacial bone injuries.

[Enophthalmos correction in complex orbital floor reconstruction : computer-assisted, intraoperative, non-contact, optical 3D support]

In the case of displacement of the globe such as enophthalmos induced by trauma, the patient is affected on both counts: function and aesthetics. To prevent double vision or conspicuous asymmetry, exact correction of the globe position is required. The aim of this case report is to demonstrate an intraoperative computer-assisted, non-contact, optical 3D procedure for identification of the globe position to aid in placing the eyeball in the position required in complex reconstruction of the orbital floor. A 33-year-old man presented with a sunken eye on the right side in the horizontal and vertical plane 6 months after having undergone surgery elsewhere for a zygomatico-orbital fracture, also including the orbital floor. The patient was affected by double vision and a noticeable defective globe position. In planning the correction of the globe position, a three-dimensional image of the face with opened eyes was made with the optical sensor. Automatic comparison of symmetry revealed enophthalmos of 4 mm on relative en- and exophthalmometry. The decision was made to lift the orbital floor with a split calvarial bone graft. During surgery the position of the globe was also controlled by the three-dimensional optical technique. At the end of surgery there was exophthalmos of 1 mm. Six weeks after surgery the patient was not affected by any double vision. After 3 and 24 months enophthalmos was 1 mm. This case demonstrates how the non-ionizing, non-contact, optical 3D technique can help in planning, intraoperative transformation, and clinical monitoring to identify the correct position of the corneal vertex in complex orbital floor reconstruction.

Computerassistierte Enophthalmuskorrektur

Pronounced enophthalmos can restrict patients both functionally and aesthetically. Typical symptoms are double vision on both eyes and obvious asymmetry, both of which were present in the 67-year-old male patient presented in this paper. The resulting data of computed tomography was used to fabricate a patient specific ceramic implant for reconstruction of the left orbital floor with an enophthalmos of 4mm. During the surgery the implant fitted anatomically correct, but exophthalmos occurred. The implant needed to be regraded and recontoured in the dorsal fraction, so that overcorrection could be reduced. With the assistance of optical 3D en- and exophthalmometry during surgery, the position of the cornea vertex was reproducible measured. At the end of surgery, exophthalmos was 1.5 mm. After 12 months, enophthalmos of only 1mm exists. This case displays the combination of a patient specific fabricated implant for reconstruction of the orbital floor with optical 3D-en-and exophthalmometry to correct enophthalmos with a high degree of accuracy. Therefore these two techniques in combination should be used when complex corrections of enophthalmos are needed.

Long-bone critical-size defects treated with tissue-engineered grafts: a study on sheep

Standardized particulate bone constructs, obtained by expanding autologous mesenchymal stem cells (MSCs) onto coral granules in vitro, were transplanted into long-bone, critical-size defects in sheep. Control experiments were also performed in which autologous bone grafts were implanted. Defect cavities were lined with a preformed vascularized membrane (induced by temporarily inserting a cement spacer for 6 weeks prior to bone construct implantation), which served as a mold keeping the engineered bone granules in place. Radiographic, histological, and computed tomographic tests performed 6 months later showed that the osteogenic abilities of the engineered construct and autograft were significantly greater than those of coral scaffold alone. No significant differences were found between the amount of newly formed bone in defects filled with coral/MSCs and those filled with autograft, yet radiological scores differed significantly between the two groups (21% and 100% healed cortices, respectively). The present study on a clinically relevant animal model provides the first evidence that standardized particulate bone constructs can be used to repair large bone defects and that their osteogenic ability approaches that of bone autograft, the bone repair benchmark. By proving feasibility, the present study makes possible the treatment of segmental bone losses with bone constructs engineered from granules, a process which is much simpler than preparing customized massive constructs using computer-assisted techniques. Important parameters, such as the rate of scaffold resorption and the number of MSCs to be seeded on the scaffolds, need to be optimized before reaching pertinent definitive conclusions.

Late Reconstruction of the Complex Orbital Fractures With Computer-Aided Design and Computer-Aided Manufacturing Technique

BACKGROUND

To construct three-dimensional (3D) imaging and computer generated models of complex orbital fractures, and develop a Computer-Aided Design/Computer-Aided Manufacture (CAD/CAM) system to help improve the surgical planning of complex orbital fracture and promote its outcome.

METHODS

A prospective study was carried out on 17 patients with unilateral complex orbital fractures from Mar 2003 to Mar 2006 at the Shanghai ninth people's hospital. The utilization of a CAD/CAM technique based on Helical computer tomography data, with stereolithographical (SLA) modelling as intermediate step, enabled surgeons to plan for the surgical progress of osteotomy, movement, reposition, fixation and material implanting. Orbital volume was calculated pre and post-operatively. Orbital fracture reconstruction and globe repositioning was performed and followed up 3-9 months post-treatment. Ocular function and aesthetic deformities such as enophthalmos, diplopia and extraocular motility problems were accessed. The data was processed with SAS 6.17 statistical software.

RESULTS

17 patients with complex orbital fractures underwent successful orbital fracture reconstruction surgery. The deformities of orbit, medial canthus, nose, zygomata, maxillary and frontal bone were well corrected. The volume of reconstructed orbit was approximately symmetrical with respect to the contralateral orbit. Enophthalmos was corrected and diplopia, extraocular movement were improved.

CONCLUSIONS

CAD/CAM system enables the surgeon to predict reconstructive surgical steps before the operation, and can help to improve the outcome of surgery. This technique may be proved as one of the most useful clinical tools for orbital surgery.

Gesichtsschädelaugmentationen mit porösen Polyethylenimplantaten (Medpor®)

SUBJECT

Porous polyethylene (Medpor) is an alloplastic material commonly used in craniofacial reconstruction. We report about our first clinical experiences with Medpor for facial augmentation procedures.

PATIENTS AND METHODS

We treated 27 patients between 2001 and 2005 (11 female, 16 male) with 48 Medpor-implants. The indications for application of porous polyethylene implants in our clinic were congenital malformations (15), post-traumatic defects (10), and reconstructions after tumor resection (2). The implants were used for nasal/paranasal augmentations (16), for zygomatico-orbital augmentations (18), and for augmentations of the chin and malar region (11). The procedures were performed in a standardized manner. We used prefabricated, self-contoured implants and fixed them subperiosteally with titanium osteosynthesis screws. All operations were performed under general anesthesia. We evaluated the aesthetic results and the ingrowth behavior clinically and histologically.

RESULTS

We achieved good aesthetic results and the patients showed no signs of discomfort or rejection. Four patients required a second intervention. These revision surgeries included two cases of local infections and two for aesthetic contouring. The necessary reduction of the implants allowed the harvesting of tissue and implant samples for microscopy.

CONCLUSION

Porous polyethylene implants showed a good fibrovascular integration without encapsulation under the light microscope. Giant cells were detected on the surface of the implants. Besides this there was evidence for resorption of the implant material. Fixation with titanium screws is very effective. No implant dislocation or implant fracture occurred. The implants showed high volume stability and were easily handled and contoured. It is not possible to visualize Medpor implants with current imaging techniques, because polyethylene shows no contrast.