Antti Mäkitie

Accuracy of medical models made by additive manufacturing (rapid manufacturing).

BACKGROUNDnAdditive manufacturing (AM) is being increasingly used for producing medical models. The accuracy of these models varies between different materials, AM technologies and machine runs.nnnPURPOSEnTo determine the accuracy of selective laser sintering (SLS), three-dimensional printing (3DP) and PolyJet technologies in the production of medical models.nnnMATERIALn3D skull models: original, moderate and worse. SLS, 3DP and PolyJet models, and a coordinate measuring machine (CMM).nnnMETHODSnMeasuring balls designed for measurements were attached to each 3D model. Skull models were manufactured using SLS, 3DP and PolyJet. The midpoints of the balls were determined using CMM. The distances between these points were calculated and compared with the 3D model.nnnRESULTSnThe dimensional error for the PolyJet was 0.18xa0±xa00.12% (first measurement) and 0.18xa0±xa00.13% (second measurement), for SLS 0.79xa0±xa00.26% (first model) and 0.80xa0±xa00.32% (second model), and for 3DP 0.67xa0±xa00.43% (original model, first measurement) and 0.69xa0±xa00.44% (original model, second measurement), 0.38xa0±xa00.22% (moderate model) and 0.55xa0±xa00.37% (worse model). Repeatability of the measurement method was 0.12% for the PolyJet and 0.08% for the 3DP.nnnCONCLUSIONnA novel measuring technique was developed and its repeatability was found to be good. The accuracy of the PolyJet was higher when compared with SLS or 3DP.

Patient‐specific reconstruction with 3D modeling and DMLS additive manufacturing

Purpose – The purpose of this paper is to develop a workflow for 3D modeling and additive manufacturing (AM) of patient‐specific medical implants. The comprehensive workflow consists of four steps: medical imaging; 3D modelling; additive manufacturing; and clinical application. Implants are used to reconstruct bone damage or defects caused by trauma or disease. Traditionally, implants have been manually bent and shaped, either preoperatively or intraoperatively, with the help of anatomic solid models. The proposed workflow obviates the manual procedure and may result in more accurate and cost‐effective implants.Design/methodology/approach – A patient‐specific implant was digitally designed to reconstruct a facial bone defect. Several test pieces were additive manufactured from stainless steel and titanium by direct metal laser sintering (DMLS) technology. An additive manufactured titanium EOS Titanium Ti64 ELI reconstruction plate was successfully implanted onto the patients injured orbital wall.Findings...

Novel additive manufactured scaffolds for tissue engineered trachea research

Abstract Conclusions: This study demonstrates proof of concept for controlled manufacturing methods that utilize novel tailored biopolymers (3D photocuring technology) or conventional bioresorbable polymers (fused deposition modeling, FDM) for macroscopic and microscopic geometry control. The manufactured scaffolds could be suitable for tissue engineering research. Objectives: To design novel trachea scaffold prototypes for tissue engineering purposes, and to fabricate them by additive manufacturing. Methods: A commercial 3D model and CT scans of a middle-aged man were obtained for geometrical observations and measurements of human trachea. Model trachea scaffolds with variable wall thickness, interconnected pores, and various degrees of porosity were designed. Photocurable polycaprolactone (PCL) polymer was used with 3D photocuring technology. Thermoplastic polylactide (PLA) and PCL were used with FDM. Cell cultivations were performed for biocompatibility studies. Results: Scaffolds of various sizes and porosities were successfully produced. Both thermoplastic PLA and PCL and photocurable PCL could be used effectively with additive manufacturing technologies to print high-quality tubular porous biodegradable structures. Optical microscopic and SEM images showed the viability of cells. The cells were growing in multiple layers, and biocompatibility of the structures was shown.

Imaging requirements for medical applications of additive manufacturing

Additive manufacturing (AM), formerly known as rapid prototyping, is steadily shifting its focus from industrial prototyping to medical applications as AM processes, bioadaptive materials, and medical imaging technologies develop, and the benefits of the techniques gain wider knowledge among clinicians. This article gives an overview of the main requirements for medical imaging affected by needs of AM, as well as provides a brief literature review from existing clinical cases concentrating especially on the kind of radiology they required. As an example application, a pair of CT images of the facial skull base was turned into 3D models in order to illustrate the significance of suitable imaging parameters. Additionally, the model was printed into a preoperative medical model with a popular AM device. Successful clinical cases of AM are recognized to rely heavily on efficient collaboration between various disciplines – notably operating surgeons, radiologists, and engineers. The single main requirement separating tangible model creation from traditional imaging objectives such as diagnostics and preoperative planning is the increased need for anatomical accuracy in all three spatial dimensions, but depending on the application, other specific requirements may be present as well. This article essentially intends to narrow the potential communication gap between radiologists and engineers who work with projects involving AM by showcasing the overlap between the two disciplines.

A digital process for additive manufacturing of occlusal splints: a clinical pilot study

The aim of this study was to develop and evaluate a digital process for manufacturing of occlusal splints. An alginate impression was taken from the upper and lower jaws of a patient with temporomandibular disorder owing to cross bite and wear of the teeth, and then digitized using a table laser scanner. The scanned model was repaired using the 3Data Expert software, and a splint was designed with the Viscam RP software. A splint was manufactured from a biocompatible liquid photopolymer by stereolithography. The system employed in the process was SLA 350. The splint was worn nightly for six months. The patient adapted to the splint well and found it comfortable to use. The splint relieved tension in the patients bite muscles. No sign of tooth wear or significant splint wear was detected after six months of testing. Modern digital technology enables us to manufacture clinically functional occlusal splints, which might reduce costs, dental technician working time and chair-side time. Maximum-dimensional errors of approximately 1 mm were found at thin walls and sharp corners of the splint when compared with the digital model.

Frontobasilar fractures: Proposal for image reviewing algorithm

OBJECTIVEnThe aim of this study was to develop and test the utility of a novel systematic protocol to analyze CT images of patients with trauma in the anterior cranial base and upper midface.nnnMATERIAL AND METHODSnThe radiological data and primary reports of 27 consecutive patients with a frontal skull base fracture treated in two tertiary care hospitals from 2007 to 2011 were scrutinized. A novel algorithm for systematic image reviewing was used to assess the CT images and the findings were compared with the primary radiological reports.nnnRESULTSnThe systematic review detected a substantial number of fractures and defects in anatomical structures that had not been systematically reported in the primary, on-call reports. Anterior skull base fracture was not initially reported in 32% of the patients; however, the algorithm detected this in 93% of them. The corresponding rates for fracture through cribriform plate were 28% and 72% and for fracture through the sella or hypophyseal area 22% and 78%. There were two fractures of the clivus and these were initially missed.nnnCONCLUSIONSnDespite the failure to identify these fractures radiologically in the primary setting, all patients were still considered to have received appropriate treatment, but, the use of an image-reviewing algorithm will enhance the specificity of CT in the diagnosis of frontobasilar fractures.

Aesthetics of the auricle and its implications for otoplasty and auricular reconstruction

OBJECTIVEnOtoplasty is the most common aesthetic surgical procedure performed in children. The goals for auricular surgery and the proportions of an aesthetically pleasing ear appear to be based on the aesthetic opinions of individual surgeons rather than on evidence-based data. Our study aimed to determine whether identifying an aesthetically pleasing auricle is possible.nnnMETHODSnWe used digital photographs of 29 auricles, a standardized camera setup, a panel of 20 plastic surgeons, and a visual analogue scale (VAS). We then analyzed the scores assigned by the panel for mean, median, standard deviation, analysis of variance, Tukey-Kramer Multiple Comparison Test, and Top 5 rankings.nnnRESULTSnRanking by the panel was statistically significant (p<0.000001).nnnCONCLUSIONSnIt is possible to statistically rank the aesthetics of auricles, although it is difficult to identify the structural details that made an auricle aesthetically pleasing.

A hamartoma presenting as an intramural upper oesophageal tumour

Oesophageal hamartomas are extremely rare conditions especially in upper oesophagus. We report on a 20-year-old woman who presented with dysphagia and was diagnosed with a retrosternal 4.9 cm × 9.0 cm heterogenic tumour located in her upper oesophagus. Preoperative examinations included computed tomography of the chest, bronchoscopy and esophagoscopy, and no signs of malignancy were noted. She underwent surgical resection of the mass and the final histopathological diagnosis was osteochondromatous hamartoma of the upper oesophagus. No acute or long-term complications or tumour recurrence were noted during a 6-year follow-up.