Quantitative Computerized Assessment of the Degree of Acetabular Bone Deficiency: Total radial Acetabular Bone Loss (TrABL)

A novel quantitative, computerized, and, therefore, highly objective method is presented to assess the degree of total radical acetabular bone loss. The method, which is abbreviated to “TrABL”, makes use of advanced 3D CT-based image processing and effective 3D anatomical reconstruction methodology. The output data consist of a ratio and a graph, which can both be used for direct comparison between specimens. A first dataset of twelve highly deficient hemipelves, mainly Paprosky types IIIB, is used as illustration. Although generalization of the findings will require further investigation on a larger population, it can be assumed that the presented method has the potential to facilitate the preoperative use of existing classifications and related decision schemes for treatment selection in complex revision cases

A custom-made guide-wire positioning device for Hip Surface Replacement Arthroplasty: description and first results

<p>Abstract</p> <p>Background</p> <p>Hip surface replacement arthroplasty (SRA) can be an alternative for total hip arthroplasty. The short and long-term outcome of hip surface replacement arthroplasty mainly relies on the optimal size and position of the femoral component. This can be defined before surgery with pre-operative templating. Reproducing the optimal, templated femoral implant position during surgery relies on guide wire positioning devices in combination with visual inspection and experience of the surgeon. Another method of transferring the templated position into surgery is by navigation or Computer Assisted Surgery (CAS). Though CAS is documented to increase accurate placement particularly in case of normal hip anatomy, it requires bulky equipment that is not readily available in each centre.</p> <p>Methods</p> <p>A custom made neck jig device is presented as well as the results of a pilot study.</p> <p>The device is produced based on data pre-operatively acquired with CT-scan. The position of the guide wire is chosen as the anatomical axis of the femoral neck. Adjustments to the design of the jig are made based on the orthopedic surgeon's recommendations for the drill direction. The SRA jig is designed as a slightly more-than-hemispherical cage to fit the anterior part of the femoral head. The cage is connected to an anterior neck support. Four knifes are attached on the central arch of the cage. A drill guide cylinder is attached to the cage, thus allowing guide wire positioning as pre-operatively planned.</p> <p>Custom made devices were tested in 5 patients scheduled for total hip arthroplasty. The orthopedic surgeons reported the practical aspects of the use of the neck-jig device. The retrieved femoral heads were analyzed to assess the achieved drill place in mm deviation from the predefined location and orientation compared to the predefined orientation.</p> <p>Results</p> <p>The orthopedic surgeons rated the passive stability, full contact with neck portion of the jig and knife contact with femoral head, positive. There were no guide failures. The jig unique position and the number of steps required to put the guide in place were rated 1, while the complexity to put the guide into place was rated 1-2. In all five cases the guide wire was accurately positioned. Maximum angular deviation was 2.9° and maximum distance between insertion points was 2.1 mm.</p> <p>Conclusions</p> <p>Pilot testing of a custom made jig for use during SRA indicated that the device was (1) successfully applied and user friendly and (2) allowed for accurate guide wire placement according to the preoperative plan.</p

Computer-aided planning of bone reconstructive surgery : optimisation of implant design through automation, integration and biomechanical validation

Complexe reconstructieve botchirurgie vereist een goed drie-dimensioneel, operatieplan. Helaas is het opstellen van zo’n plan met conventionele computerondersteunde technieken, belastend en tijdsintensief. De gebruiker – een chirurg of een biomedisch ingenieur – moet zich manueel en met kennis van zaken door medische beeldverwerkingssoftware en CAD programma’s worstelen om, uitgaande van de defecte situatie van het bot, de positie van een gestandaardiseerde component van een implantaat vast te leggen en een rondliggende botstructuur vorm te geven. Bovendien vergt een goed operatieplan meer dan alleen maar een voorstelling van de botgeometrie, en intelligente programma’s voor de reconstructie van het bot. De belangrijkste zorg van de chirurg gaat uit naar de stabiliteit van de reconstructie, het vrijwaren van gezond omliggend weefsel, en daarmee, het herstel van de functionaliteit van de patiënt. Tot voor kort werden bijvoorbeeld louter generische musculoskeletale modellen en Eindige Elementen (EE) studies voorgesteld om het resultaat van een ingreep te simuleren. Doeltreffende en volledig geautomatiseerde technieken voor het individualiseren van spiertrajecten en spieraanhechtingen zijn – hoewel onmisbaar in geval van gepersonaliseerde reconstructies – nog niet beschikbaar. Het doel van dit doctoraatsonderzoek is het computer-gesteund plannen van reconstructieve botchirurgie, en meer precies het implantaatontwerp, te optimaliseren door middel van automatisatie, integratie en biomechanische validatie. Een computer-gesteunde methodologie die de gebruiker een biomechanisch verantwoord en automatisch voorstel tot correctie van een botdefect of een botmisvorming aanbiedt, dient ontwikkeld en gevalideerd te worden. Dit voorstel, dat initieel zal dienst doen als een bijkomend diagnosemiddel, kan dan gebruikt worden om een gepersonaliseerd – mogelijk defectvullend en lastdragend – implantaat vorm te geven, en om dit moeiteloos op volledig patiënt-specifieke wijze te evalueren in een eindige elementen softwarepakket. Tenslotte dient het resulterende CAD (Computer-Aided-Design) ontwerp efficiënt gekoppeld te worden aan directe (Rapid Manufacturing (RM)) en indirecte (persen, frezen van mallen) productietechnieken. De algemeen ontwikkelde methodologie wordt uiteengezet met klinische en retrospectieve gevalsstudies over het gevarieerde domein van reconstructieve botchirurgie. Concreet omhelst dit voorbeelden uit de orthopedie / traumachirurgie en cranio-maxillo-faciale- en kaakchirurgie.status: publishe

Large bone tumour defects: personalised shape reconstruction and plate design

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Medical application of single point incremental forming: cranial plate manufacturing

Single Point Incremental Forming (SPIF) is a new sheet metal forming technique that, unlike other forming processes, does not require a dedicated tool set. Because of the absence of a die, SPIF is ideally suited for small batch or tailored production of sheet metal parts. Medical applications typically fit within these categories. The case presented in this paper deals with the production of a cranial plate used in reconstructive skull surgery. The SPIF process is compared to the conventional manufacturing methods. © 2005 Taylor & Francis Group.Book subtitle: ADVANCED RESEARCH IN VIRTUAL AND RAPID PROTOTYPINGstatus: publishe

Customised medical implant production by means of single point incremental forming

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Computed tomography-based joint locations affect calculation of joint moments during gait when compared to scaling approaches

Hip joint moments are an important parameter in the biomechanical evaluation of orthopaedic surgery. Joint moments are generally calculated using scaled generic musculoskeletal models. However, due to anatomical variability or pathology, such models may differ from the patient's anatomy, calling into question the accuracy of the resulting joint moments. This study aimed to quantify the potential joint moment errors caused by geometrical inaccuracies in scaled models, during gait, for eight test subjects. For comparison, a semi-automatic computed tomography (CT)-based workflow was introduced to create models with subject-specific joint locations and inertial parameters. 3D surface models of the femora and hemipelves were created by segmentation and the hip joint centres and knee axes were located in these models. The scaled models systematically located the hip joint centre (HJC) up to 33.6 mm too inferiorly. As a consequence, significant and substantial peak hip extension and abduction moment differences were recorded, with, respectively, up to 23.1% and 15.8% higher values in the image-based models. These findings reaffirm the importance of accurate HJC estimation, which may be achieved using CT- or radiography-based subject-specific modelling. However, obesity-related gait analysis marker placement errors may have influenced these results and more research is needed to overcome these artefacts.peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=gcmb20status: publishe

Computer supported pre-operative planning of craniosynostosis surgery: a mimics-integrated approach

Clijmans T., Gelaude F., Mommaerts M., Suetens P., Vander Sloten J., ''Computer supported pre-operative planning of craniosynostosis surgery: a mimics-integrated approach'', Annual medical innovations conference - Materialise Mimics Innovation Awards 2006, May 27, 2006, Barcelona, Spain.status: publishe

Simulation tool for predicting the impact of acetabulum reconstruction on hip muscles

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CT-based virtual shape reconstruction for severe glenoid bone defects

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