Bernd Lethaus

Additive manufacturing for microvascular reconstruction of the mandible in 20 patients

OBJECTIVES The aim of this study was to evaluate the use of model mandibles made preoperatively by additive manufacturing, which were used to prebend reconstruction plates prior to mandibular resection and reconstruction with microvascular bony flaps. MATERIALS AND METHODS Computer Tomography (CT) or Cone Beam Tomography (CBT) scans acquired preoperatively were used to obtain DICOM data sets to produce a model of the mandible using rapid prototyping. This model was used as a template to prebend and then sterilize a 2.3 or 2.7 reconstruction plate, which was used to reconstruct the mandible with a microvascular bony flap. This technique was used in 20 consecutive patients who required mandibular resection and reconstruction because of a tumour or osteoradionecrosis. RESULTS The prebent plate was used in all patients intraoperatively without the need for any further bending. The average time to bend a plate on a nonsterile model was 0.42 h (range 0.25-0.68 h). This is felt to represent the minimum amount of time saved during the operation. Additive manufacture of the mandible prior to resection and reconstruction with a microvascular flap is a useful technique which reduces the operating time.

A treatment algorithm for patients with large skull bone defects and first results.

Large skull bone defects resulting from craniotomies due to cerebral insults, trauma or tumours create functional and aesthetic disturbances to the patient. The reconstruction of large osseous defects is still challenging. A treatment algorithm is presented based on the close interaction of radiologists, computer engineers and cranio-maxillofacial surgeons. From 2004 until today twelve consecutive patients have been operated on successfully according to this treatment plan. Titanium and polyetheretherketone (PEEK) were used to manufacture the implants. The treatment algorithm is proved to be reliable. No corrections had to be performed either to the skull bone or to the implant. Short operations and hospitalization periods are essential prerequisites for treatment success and justify the high expenses.

Reconstruction of a maxillary defect with a fibula graft and titanium mesh using CAD/CAM techniques.

We present a case of maxillary and orbital floor reconstruction with a microvascular fibula graft and an individualized titanium mesh. Both were planned virtually; templates were made by rapid prototyping. The postoperative computertomography scans showed that the planned positions were achieved correctly. This case report illustrates maxillary reconstruction performed with a special template technique and demonstrates the possibilities of computer aided design/computer aided manufacturing (CAD/CAM) applications in reconstructive surgery.

The accuracy of computer-assisted primary mandibular reconstruction with vascularized bone flaps: iliac crest bone flap versus osteomyocutaneous fibula flap.

Background The intention of mandibular reconstruction is to restore the complex anatomy with maximum possible functionality and high accuracy. The aim of this study was to evaluate the accuracy of computer-assisted surgery in primary mandibular reconstruction with an iliac crest bone flap compared with an osteomyocutaneous fibula flap. Materials and methods Preoperative computed tomography data of the mandible and the iliac crest or fibula donor site were imported into a specific surgical planning software program. Surgical guides were manufactured using a rapid prototyping technique for translating the virtual plan, including information on the transplant dimensions and shape, into real-time surgery. Using postoperative computed tomography scans and an automatic surface-comparison algorithm, the actual postoperative situation was compared with the preoperative virtual simulation. Results The actual flap position showed a mean difference from the virtual plan of 2.43 mm (standard deviation [SD] ±1.26) and a surface deviation of 39% <2 mm and 15% <1 mm for the iliac crest bone flap, and a mean difference of 2.18 mm (SD ±1.93) and a surface deviation of 60% <2 mm and 37% <1 mm for the osteomyocutaneous fibula flap. The position of the neomandible reconstructed with an osteomyocutaneous fibula flap indicated a mean difference from the virtual plan of 1.25 mm (SD ±1.31) and a surface deviation of 82% <2 mm and 57% <1 mm, in contrast to a mean difference of 1.68 mm (SD ±1.25) and a surface deviation of 63% <2 mm and 38% <1 mm for the neomandible after reconstruction with an iliac crest bone flap. For shape analysis, a similarly high accuracy could be calculated for both flaps. Conclusion Virtual surgical planning is an effective method for mandibular reconstruction with vascularized bone flaps, and can help to restore the anatomy of the mandible with high accuracy in position and shape. It seems that primary mandibular reconstruction with the osteomyocutaneous fibula flap is more accurate compared with the vascularized iliac crest bone flap.

Pilot study of modification of the bilateral sagittal split osteotomy (BSSO) in pig mandibles

OBJECTIVE This study investigated a new technique for the bilateral sagittal split osteotomy (BSSO) by adding a new osteotomy line at the inferior border of the mandible in the Obwegeser-Dal Pont operation. MATERIAL AND METHODS For this purpose a test system was designed and 100 pig mandibles were split to assess the tests reliability, to compare the torque necessary to split the mandible in both techniques and to record the fracture lines. The splitting technique was standardized, avoiding any contact with the inferior alveolar nerve. All outcomes were statistically examined by paired t-tests. RESULTS By using the new technique, we demonstrated a decrease in the torque force required to split the mandible of 29.7% (t(69)=-12.68; p<0.05, paired t-test) compared to the Obwegeser-Dal Pont technique. The fracture lines were close to ideal. CONCLUSION The additional osteotomy facilitates the BSSO technique and it reduces the likelihood of bad splits and damage to the inferior alveolar nerve in pig mandibles.

Interval cranioplasty with patient-specific implants and autogenous bone grafts--success and cost analysis.

UNLABELLED Different options exist for the reconstruction of craniectomy defects following interval cranioplasty. The standard procedure is still based on the re-implantation of autogenous bone specimen which can be stored in the abdominal wall or be cryopreserved. Alternatively patient-specific implants (PSIs) can be used. We conducted a retrospective study based on 50 consecutive patients with skull bone defects of 100 cm(2) or more being operated on by the same team of surgeons. Thirty-three patients agreed to take part in the study. Seventeen patients who underwent reconstruction with PSIs (titanium and polyether ether ketone, PEEK) (follow-up, 43 months [range, 3-93]) were compared with 16 control subjects who had autogenous bone grafts re-implanted (follow-up, 32 months [range, 5-92]). Criteria analyzed were the success and complication rates, operation time, duration of hospitalization and the treatment costs. Complication rate and the rate of reoperation were significantly lower, and the hospital stay was shorter in the PSI group. The treatment costs for reconstruction with autogenous bone were considerably lower than skull bone reconstruction based on PSIs (average costs: 10849.91 €/patient versus 15532.08 €/patient with PSI). Due to biological reasons some of the autogenous bone implants fail due to infection and resorption and the patients have to undergo another operation with implantation of a PSI in a secondary attempt. For those patients the highest overall treatment costs must be calculated (average costs: 26086.06 €/patient with secondary stage PSI versus 15532.08 €/patient with primary stage PSI). CONCLUSION High success rates and reliability of PSIs may change the treatment strategy in patients undergoing interval cranioplasty.

Different Culture Media Affect Proliferation, Surface Epitope Expression, and Differentiation of Ovine MSC

Orthopedic implants including engineered bone tissue are commonly tested in sheep. To avoid rejection of heterologous or xenogeneic cells, autologous cells are preferably used, that is, ovine mesenchymal stem cells (oMSC). Unlike human MSC, ovine MSC are not well studied regarding isolation, expansion, and characterization. Here we investigated the impact of culture media composition on growth characteristics, differentiation, and surface antigen expression of oMSC. The culture media varied in fetal calf serum (FCS) content and in the addition of supplements and/or additional epidermal growth factor (EGF). We found that FCS strongly influenced oMSC proliferation and that specific combinations of supplemental factors (MCDB-201, ITS-plus, dexamethasone, and L-ascorbic acid) determined the expression of surface epitopes. We compared two published protocols for oMSC differentiation towards the osteogenic, adipogenic, and chondrogenic fate and found (i) considerable donor to donor variations, (ii) protocol-dependent variations, and (iii) variations resulting from the preculture medium composition. Our results indicate that the isolation and culture of oMSC in different growth media are highly variable regarding oMSC phenotype and behaviour. Furthermore, variations from donor to donor critically influence growth rate, surface marker expression, and differentiation.

Guided bone regeneration: dynamic procedures versus static shielding in an animal model.

Due to its osteoinductive potential, the periosteum plays a crucial role in the process of neoosteogenesis. Therefore, periosteal elevation can lead to new bone formation in an artificially created space. In this study, we compared dynamic periosteal elevation with static shielding in an animal experiment. Different elevation/shielding heights of 5, 10, and 15 mm were tested with regard to various consolidation periods. Histological analysis, histomorphometry, and microradiography were used to measure the quantity and quality of the newly formed bone. No significant differences regarding bone quantity or quality were found between the two techniques. The cumulative results for the bone regeneration in the space created by distraction/elevation were about 66% in the dynamic and 67% in static procedure. The main advantages of both techniques are minimal invasion and low morbidity. In terms of clinical applications, periosteal elevation could be applied in cranio-maxillofacial surgery, in pre-implant augmentation and in reconstructive surgery.

Definition of quality indicators in microsurgery in head and neck reconstruction based on a 5-year follow-up without a loss.

BACKGROUND Microsurgical tissue transfer is a standard procedure in reconstructive surgery of defects in head and neck oncology patients. According to the literature vascular thrombosis occurs in 8-14% of cases and is considered to be the main reason for flap failure. A review of the literature on this subject was carried out and related to the quality guidelines of the Department of Cranio-Maxillofacial Surgery in the Maastricht University Medical Centre. We defined quality indicators and quality goals for the reconstruction of head and neck defects. We investigated whether or not these parameters are practicable in a specialized head and neck cancer unit. PATIENTS AND METHODS We included 81 consecutive patients with oral cancer/osteoradionecrosis of the mandible who received a microsurgical free tissue transfer for reconstruction. The patients were treated in our institution between August 2007 and December 2011. Patient data were collected in a prospective database. Follow-up was conducted in the Department of Cranio-Maxillofacial Surgery. Data were analysed for the defined reference groups, and the results were compared with the quality goals. RESULTS Median follow-up was 29.1 (range 1-55) months. There were only six (7.4%) immediate complications leading to compromised flaps. Among the complications were four (5.0%) anastomosis-related complications and two haematomas (2.5%). There was no flap loss. Based on the quality goals we were able to reach an overall flap success rate of 100%. CONCLUSION Most of the defined quality goals can be attained in a specialized head and neck unit. Careful patient selection, pharmacologic, non-pharmacologic and surgical measures for preventing thrombosis, such as meticulous micro-vascular surgery are considered to be essential. No consensus in the literature was found on how complications could best be prevented. The role of a standardized pre-, peri- and postoperative management is presented. The importance of thorough planning and the technical skill of the reconstructive surgeon are highlighted. The debate on quality goals has the potential to enable further improvement in the care of head and neck cancer patients.

Fluorescent SNAP-Tag Galectin Fusion Proteins as Novel Tools in Glycobiology

Galectins,β-galactoside binding proteins, function in several physiological and pathological processes. The further evaluation of these processes as well as possible applications of galectins in diagnosis and therapy has raised high scientific interest. Therefore, easy and reliable test systems are necessary. Here we present the simple and cost-efficient production of recombinant human galectins as fusion proteins with SNAP-tag and fluorescent proteins. These constructs show binding specificities and oligomerisation properties generally comparable to recombinant galectins. Their direct fluorescence signal was utilised by ELISA-type assay and flow cytometry analysis with human and ovine mesenchymal stem cells (MSC). Flow cytometry demonstrated glycan mediated binding of His6-SNAP-YFP-Gal- 3 to both MSC types, which was specifically inhibited by lactose. Moreover, directed immobilisation by SNAP-tag technology onto benzylguanine- activated sepharose was utilised to prepare galectin affinity columns for glycoprotein analysis and purification. The SNAPtag directed coupling yielded up to three-fold higher binding capacities for the glycoprotein standard asialofetuin compared to nondirected coupled galectin suggesting improved functionality following directed coupling.