Prediction of 3-Dimensional Coverage Surface Area of the Femoral Head in Hip Dysplasia Through Conventional Computed Tomography.

Background: Assessment of 3-dimensional (3D) femoral head coverage is critical in evaluating, preoperative planning, and treating hip dysplasia. Purpose: To (1) propose a mathematical model to establish 3D femoral head coverage using conventional computed tomography (CT), (2) determine the correlation of 2D parameters with 3D coverage, and (3) characterize the patterns of dysplasia based on 3D morphology. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We identified 30 patients (n = hips) with symptomatic dysplasia and 30 patients (n = hips) without dysplasia. Patients with dysplastic hips were matched with regard to sex, age, and body mass index to those with nondysplastic hips. Preoperative CTs were analyzed using 3D software, and 3D femoral head surface area coverage (FHSAC; in %) was assessed in 4 quadrant zones: anteromedial, anterolateral, posteromedial, and posterolateral. To assess lateral coverage of the femoral head, we introduced the anterolateral femoral head coverage angle (ALFC) and the posterolateral femoral head coverage angle (PLFC). Results: Reduced femoral head coverage was more pronounced in dysplastic versus nondysplastic hips in the anterolateral quadrant (18% vs 40.7%, respectively) and posterolateral quadrant (35.8% vs 56.9%, respectively) (P < .0001 for both). Dysplastic hips had smaller ALFC and PLFC (18.4° vs 38.7°; P < .0001; 47.2° vs 72.3°; P = .0002). Anterolateral and posterolateral FHSAC were strongly correlated with the ALFC (r = 0.88; P < .0001) and the PLFC (r = 0.82; P < .0001) along with the lateral center-edge angle (anterolateral, r = 0.75; P < .0001; posterolateral, r = 0.73; P < .0001). Prediction models established for FHSAC had strong agreement with explanatory CT variables (anterolateral: r = 0.91; P < .0001; posterolateral: r = 0.90; P < .0001). The cutoff values for anterolateral and posterolateral FHSAC were 25% and 41%, respectively. In dysplastic hips, global deficiency was most common (15/30 hips), 9 hips showed an anterolateral deficiency, and 4 hips had a posterolateral deficiency pattern. Conclusion: The ALFC and The PLFC were strongly correlated with 3D lateral FHSAC and were able to predict 3D coverage accurately.

Navigated multiplanar osteotomies for spinal primary bone tumors.

BACKGROUND: Establishing the proper diagnosis and rendering appropriate treatment of spinal primary bone tumors (SPBT) can result in definitive cures. Notably, malignant, or benign SPBT (i.e., with aggressive local behavior) generally require en bloc resection. Osteotomies of the vertebral body in more than 1 plane may avoid critical structures, preserve nerve functions, and reduce the volume of healthy bone resected. Here, our objective was to report how we planned and performed navigated multiplanar osteotomies for en bloc resection of 14 SPBT. METHODS: We performed a retrospective analysis of 14 patients with malignant or locally aggressive benign SPBT operated on consecutively between 2014 and 2019 utilizing preoperative 3D planning/navigation. Tumors were resected in an en bloc fashion utilizing multiplanar osteotomies. Patients were followed for a minimum of 12 postoperative months. RESULTS: Diagnoses included three benign but locally aggressive bone tumors (i.e., all osteoblastomas) and 11 primary sarcomas (i.e., six chordomas and five chondrosarcomas). Eleven tumors involved the sacrum and the other three, the thoracic spine. In 12 patients, the en bloc margins were classified as marginal (<1 cm), and in two patients, as wide (>1 cm). Intraoperative navigation facilitated the performance of 40 osteotomies in 14 patients (median = 2.9, range = 2-6). CONCLUSION: Navigated multiplanar osteotomies increased the precision and safety of en bloc resections for 14 primary spinal bone tumors SPBT that included 11 malignant and three benign/locally aggressive lesions.

Total Temporomandibular Joint Replacement and Simultaneous Orthognathic Surgery Using Computer-Assisted Surgery.

BACKGROUND: Disorders of the temporomandibular joint (TMJ) are frequent and are usually associated with other disorders of the facial skeleton. Surgery might be needed to correct TMJ anatomy and function and, in cases where pathologies coexist, a two-stage corrective surgery might be needed. However, the current fashion of single-stage procedures is feasible with the aid of new technologies such as computer-assisted surgery (CAS). This is a step forward toward performing complex procedures such as a TMJ replacement with simultaneous orthognathic surgery. CAS allows designing patient-fitted prosthesis and more predictable and accurate surgeries. Moreover, intraoperative development can be controlled in real time with intraoperative navigation, and postoperative results can be measured and compared afterwards. AIMS: The primary purpose of this article is to present the protocol used in our institution for orthognathic surgery associated with unilateral and bilateral TMJ replacement with patient-fitted prostheses guided with CAS. MATERIALS AND METHODS: We present two cases to illustrate our protocol and its results. RESULTS: In the first case, the difference in millimeters between planning and surgical outcomes was 1.72 mm for the glenoid component and 2.16 mm for the condylar prosthesis; for the second case, differences in the right side were 2.59 mm for the glenoid component and 2.06 mm for the ramus, and in the left side, due to the anatomy the difference was a little greater, without clinical significance. CONCLUSION: Combined surgery of the midface and mandible with total TMJ replacement is feasible and beneficial for the patient. CAS facilitates the planning and design of custom-fit prosthesis and execution of these procedures.

Computer-assisted surgery (CAS) in orthopedic oncology. Which were the indications, problems and results in our first consecutive 203 patients?

AIMS: to review a group of patients with primary bone tumors treated with intraoperative navigation and analyze: (1) The technical problems; (2) Indications for Computer Assisted Surgery (CAS); (3) Oncological results; (4) Non oncological complications. MATERIALS AND METHODS: All patients from a single institution who had preoperative virtual planned for an oncological primary bone resection assisted with navigation between May 2010 and July 2017 were enrolled in the study (203 patients). The use of computer-assisted surgery (CAS) was classified according to the oncologic procedure performed: (1) intralesional resections, (2) en-block resections, and (3) en-block resections + navigated allograft reconstructions. RESULTS: Four patients (4/203, 2%) of the series presented technical problems which came from 2 software and 2 hardware crashes. Eight (4%) procedures were intralesional resections and no local recurrences or complications were reported in this group. Ninety-eight surgeries (49%) were pure en block resection. The pelvis and sacrum were the main location in this group (57%). All bone margins were defined negative but 2 patients presented a positive resection in the soft tissues. Infection was the most prevalent complication (16/23). Ninety-three procedures were done for en block resections + allograft reconstruction (all extremities tumor). All margins were free of tumor and non oncological rate for this group was 28%. CONCLUSION: The main indications for CAS were malignant bone tumors resection. The technical failures precluded navigation use in 2%. CAS for pure en-block resections were mainly indicated in pelvic and sacrum tumors while en-block resection + allograft reconstruction assisted with navigation were only indicated in extremities tumors. LEVEL OF EVIDENCE: IV.

Resección de pared torácica guiada por navegación en paciente con antecedente de resección de sarcoma con márgenes oncológicos comprometidos / Navigation-Guided Chest Wall Resection in Patient with a History of Resected Sarcoma with Compromised Oncological Margins

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Is Navigation-guided En Bloc Resection Advantageous Compared With Intralesional Curettage for Locally Aggressive Bone Tumors?

BACKGROUND: The treatment of locally aggressive bone tumors is a balance between achieving local tumor control and surgical morbidity. Wide resection decreases the likelihood of local recurrence, although wide resection may result in more complications than would happen after curettage. Navigation-assisted surgery may allow more precise resection, perhaps making it possible to expand the procedure's indications and decrease the likelihood of recurrence; however, to our knowledge, comparative studies have not been performed. QUESTIONS/PURPOSES: The purpose of this study was to compare curettage plus phenol as a local adjuvant with navigation-guided en bloc resection in terms of (1) local recurrence; (2) nononcologic complications; and (3) function as measured by revised Musculoskeletal Tumor Society (MSTS) scores. METHODS: Patients with a metaphyseal and/or epiphyseal locally aggressive primary bone tumor treated by curettage and adjuvant therapy or en bloc resection assisted by navigation between 2010 and 2014 were considered for this retrospective study. Patients with a histologic diagnosis of a primary aggressive benign bone tumor or low-grade chondrosarcoma were included. During this time period, we treated 45 patients with curettage of whom 43 (95%) were available for followup at a minimum of 24 months (mean, 37 months; range, 24-61 months), and we treated 26 patients with navigation-guided en bloc resection, of whom all (100%) were available for study. During this period, we generally performed curettage with phenol when the lesion was in contact with subchondral bone. We treated tumors that were at least 5 mm from the subchondral bone, such that en bloc resection was considered possible with computer-assisted block resection. There were no differences in terms of age, gender, tumor type, or tumor location between the groups. Outcomes, including allograft healing, nonunion, tumor recurrence, fracture, hardware failure, infection, and revised MSTS score, were recorded. Bone consolidation was defined as complete periosteal and endosteal bridging visible between the allograft-host junctions in at least two different radiographic views and the absence of pain and instability in the union site. All study data were obtained from our longitudinally maintained oncology database. RESULTS: In the curettage group, two patients developed a local recurrence, and no local recurrences were recorded in patients treated with en bloc resection. All patients who underwent navigation-guided resection achieved tumor-free margins. Intraoperative navigation was performed successfully in all patients and there were no failures in registration. Postoperative complications did not differ between the groups: in patients undergoing curettage, 7% (three of 43) and in patients undergoing navigation, 4% (one of 26) had a complication. There was no difference in functional scores: mean MSTS score for patients undergoing curettage was 28 points (range, 27-30 points) and for patients undergoing navigation, 29 (range, 27-30 points; p = 0.10). CONCLUSIONS: In this small comparative series, navigation-assisted resection techniques allowed conservative en bloc resection of locally aggressive primary bone tumors with no local recurrence. Nevertheless, with the numbers available, we saw no difference between the groups in terms of local recurrence risk, complications, or function. Until or unless studies demonstrate an advantage to navigation-guided en bloc resection, we cannot recommend wide use of this novel technique because it adds surgical time and expense. LEVEL OF EVIDENCE: Level III, therapeutic study.

Medición de impedancias in-vivo durante la cirugía de implante coclear como predictor de la posición de los electrodos dentro de la cóclea / Impedance measures during in-vivo cochlear implantation predict array positioning / Medição das impedâncias in-vivo durante a cirurgia de implante coclear como preditor da posição dos eletrodos no interior da cóclea

INTRODUCCIÓN: Los implantes cocleares son dispositivos protésicos neuronales utilizados para el tratamiento de las hipoacusias neurosensoriales severas a profundas. La activación de electrodos estimula las células del ganglio espiral y las vías nerviosas. Una estimulación más discreta de subpoblaciones neuronales se puede obtener cuando los electrodos están más cerca de las células ganglionares en la pared del modiolo. La distancia del electrodo al modiolo podría ser una de las múltiples variables que influyen en el resultado del paciente con un implante coclear. Actualmente no hay un protocolo establecido para medir esta distancia. Mediante diversas técnicas de imágenes se puede determinar la posición de la guía de electrodos dentro de la cóclea. La tomografía computada cone beam ha sido validada como una herramienta útil para evaluar la posición de los electrodos luego de la implantación. Tykocinski et al. describieron un modelo de la interfase electrodo-electrolito del implante coclear como una resistencia y un condensador en paralelo, y la resistencia del tejido circundante como una resistencia en serie. Realizando un registro detallado de la forma de la curva de voltaje, los datos pueden usarse para calcular la impedancia clínica o total, la resistencia de acceso, la impedancia de polarización y sus subcomponentes: Resistencia de polarización y capacitancia de polarización. El objetivo de este estudio es determinar si la distancia electrodo modiolar de cada uno de los electrodos podría predecirse a partir de mediciones de impedancia...

INTRODUCTION: Cochlear implants are neuronal prosthetic devices used for the treatment of severe to profound sensorineural hearing loss. The activation of electrodes stimulates spiral ganglion cells and nerve pathways. A more discrete stimulation of neuronal subpopulations can be obtained when the electrodes are closer to the ganglion cells in the modiolus wall. The distance from the electrode to the modiolus could be one of the multiple variables that influence the outcome of the patient with a cochlear implant. Currently there is no established protocol to measure this distance. By means of various imaging techniques, the position of the electrode guide inside the cochlea can be determined. Cone beam computed tomography has been validated as a useful tool to evaluate the position of the electrodes after implantation. Tykocinski et al., described a model of the electrode-electrolyte interface of the cochlear implant as a resistance and a capacitor in parallel, and the resistance of the surrounding tissue as a series resistance. By making a detailed record of the shape of the voltage curve, the data can be used to calculate the clinical or total impedance, the access resistance, the polarization impedance and its subcomponents: polarization resistance and polarization capacitance. The objective of this study is to determine if the electrode distance modiolar of each of the electrodes could be predicted from impedance measurements…

INTRODUCÃO: Os implantes cocleares são dispositivos protéticos neuronais utilizados no tratamento da perda auditiva neurossensorial severa a profunda. A ativação de eletrodos estimula as células ganglionares espirais e as vias nervosas. Uma estimulação mais discreta de subpopulações neuronais pode ser obtida quando os eletrodos estão mais próximos das células ganglionares na parede do modíolo. A distância do eletrodo ao modíolo pode ser uma das múltiplas variáveis que influenciam o resultado do paciente com implante coclear. Atualmente não há protocolo estabelecido para medir essa distância. Por meio de várias técnicas de imagem, a posição do guia do eletrodo dentro da cóclea pode ser determinada. A tomografia computadorizada por feixe cônico foi validada como uma ferramenta útil para avaliar a posição dos eletrodos após o implante. Tykocinski et al. Descreveu um modelo da interface eletrodo-eletrólito do implante coclear como uma resistência e um capacitor em paralelo, e a resistência do tecido circundante como uma resistência em série. Realizando um registo detalhado da forma da curva de tensão, os dados podem ser usados para calcular a impedância clínico ou total, a resistência de acesso, a impedância de polarização e seus subcomponentes: resistência de polarização e capacitância de polarização. O objetivo deste estudo é determinar se a distância modiolar do eletrodo de cada um dos eletrodos poderia ser prevista a partir de medidas de impedância...

Manejo endoscópico de osteoma etmoidal con extensión orbitaria: a propósito de un caso / Endoscopic manegement of frontoethmoidal osteoma: on case subject

El osteoma es el tumor más frecuente de los senos paranasales, habitualmente asintomático debido a su lento crecimiento, sin embargo, pueden desarrollarse síntomas dependiendo del tamaño, localización y extensión, con potencial compromiso de órbita y cerebro. La cirugía está indicada en casos sintomáticos pudiendo realizarse abordaje externo, endoscópico o combinado. Presentamos un caso de osteoma etmoidal con compromiso orbitario resuelto, manejado por medio de la cirugía endoscópica nasal, con apoyo de navegación.

The osteoma is the most common tumor of the paranasal sinuses, is usually asymptomatic because of their slow growth, however, may develop symptoms depending on the size, location and extent, with potential compromise of orbit and brain. Surgery is indicated in symptomatic cases, with external, endoscopic or combined approach. We present a case of ethmoidal osteoma with orbital involvement managed by endoscopic image guided surgery.

Cirugía endoscópica nasosinusal y de base de cráneo asistida por navegación / Endoscopic sinonasal surgery and skull base surgery assited navigation

Introducción: La cirugía guiada por imágenes corresponde a una herramienta quirúrgica que comienza a desarrollarse a mediados del siglo XX. En 1990 comienza a utilizarse en otorrinolaringología, siendo sus principales indicaciones la cirugía endoscópica de cavidades paranasales y la cirugía de base de cráneo anterior. Objetivo: Analizar y presentar el resultado del uso de cirugía guiada por imágenes en pacientes intervenidos en el Hospital Clínico de la Universidad de Chile (HCUCH). Material y método: Se realizó un estudio retrospectivo incluyendo todos los casos de cirugía endoscópica nasosinusal y base de cráneo asistida por imágenes en HCUCH. La selección para usar la navegación se hizo en base a las recomendaciones de la Academia Americana de Otorrinolaringología. Resultados: De un total de 12 pacientes intervenidos con el uso de navegación, se obtuvo 100% de éxito quirúrgico con disminución de los síntomas y sin complicaciones intraoperatorias. Conclusión: La cirugía asistida por navegación en cavidades paranasales y base de cráneo, es una herramienta de suma utilidad en casos seleccionados que potencia las habilidades quirúrgicas del cirujano sin reemplazar sus conocimientos anatómicos. Otorga seguridad y precisión en cirugías que comprometen estructuras nobles como base de cráneo y órbita entre otros.

Introduction: Image Guided Surgery is a surgical tool that develop in the mid-twentieth century. In 1990 it began to be used in otolaryngology, being its main indications endoscopic surgery of paranasal sinuses and anterior skull base. Aim: To analyze and present the result of image-guided surgery in patients undergoing surgery at the Hospital of the University of Chile. Material and method: A retrospective study included all cases of endoscopic sinus surgery and skull base imaging assisted at the Clinical Hospital of the University of Chile from August 2015 to August 2016. The choice to use the navigation was made in based on the recommendations of the American Academy of Otolaryngology, and analyzed case by case. Results: A total of 12 patients were operated using Navigation, achieving 100 % of surgical success with decreased symptoms and without intraoperative complications. Conclusion: Image Guided Surgery in paranasal sinuses and skull base is a tool very useful in selected cases where enhances the surgeon skills without replacing their anatomical knowledge. Provides security and accuracy in surgeries involving noble structures such as the skull base, orbit among others. their anatomical knowledge. Provides security and accuracy in surgeries involving noble structures such as the skull base, orbit among others.

Virtual Planning and Allograft Preparation Guided by Navigation for Reconstructive Oncologic Surgery: A Technical Report.

INTRODUCTION: Advanced virtual simulators can be used to accurately detect the best allograft according to size and shape. STEP 1 ACQUISITION OF MEDICAL IMAGES: Obtain a multislice CT scan and a magnetic resonance imaging (MRI) scan preoperatively for each patient; however, if the time between the scans and the surgery is >1 month, consider repeating the MRI because the size of the tumor may have changed during that time. STEP 2 SELECT AN ALLOGRAFT USING VIRTUAL IMAGING TO OPTIMIZE SIZE MATCHING: Load DICOM images into a virtual simulation station (Windows 7 Service Pack 1, 64 bit, Intel Core i5/i7 or equivalent) and use mediCAS planning software ( medicas3d.com ) or equivalent (Materialise Mimics or Amira software [FEI]) for image segmentation and virtual simulation with STL (stereolithography) files. STEP 3 PLAN AND OUTLINE THE TUMOR MARGINS ON THE PREOPERATIVE IMAGING: Determine and outline the tumor margin on manually fused CT and MRI studies using the registration tool of the mediCAS planning software or equivalent (Materialise Mimics software.). STEP 4 PLAN AND OUTLINE THE SAME OSTEOTOMIES ON THE ALLOGRAFT: Determine and outline the osteotomies between host and donor using the registration tool of the mediCAS planning software or equivalent (Materialise Mimics software.). STEP 5 ASSESS THE PATIENT AND ALLOGRAFT IN A VIRTUAL SCENARIO: Be sure to consider the disintegration of bone tissue that occurs during the osteotomy and corresponds to the thickness of the blade (approximately 1.5 mm). STEP 6 NAVIGATION SETTINGS: A tool of the mediCAS planning software allows the virtual preoperative planning (STL files) to be transferred to the surgical navigation format, DICOM files. STEP 7 PATIENT AND ALLOGRAFT INTRAOPERATIVE NAVIGATION: The tumor and allograft are resected using the navigated guidelines, which were previously planned with the virtual platform. RESULTS: The 3D virtual preoperative planning and surgical navigation software are tools designed to increase the accuracy of bone tumor resection and allograft reconstruction3.

What Is the Expected Learning Curve in Computer-assisted Navigation for Bone Tumor Resection?

BACKGROUND: Computer navigation during surgery can help oncologic surgeons perform more accurate resections. However, some navigation studies suggest that this tool may result in unique intraoperative problems and increased surgical time. The degree to which these problems might diminish with experience-the learning curve-has not, to our knowledge, been evaluated for navigation-assisted tumor resections. QUESTIONS/PURPOSES: (1) What intraoperative technical problems were observed during the first 2 years using navigation? (2) What was the mean time for navigation procedures and the time improvement during the learning curve? (3) Have there been any differences in the accuracy of the registration technique that occurred over time? (4) Did navigation achieve the goal of achieving a wide bone margin? METHODS: All patients who underwent preoperative virtual planning for tumor bone resections and operated on with navigation assistance from 2010 to 2012 were prospectively collected. Two surgeons (GLF, LAA-T) performed the intraoperative navigation assistance. Both surgeons had more than 5 years of experience in orthopaedic oncology with more than 60 oncology cases per year per surgeon. This study includes from the very first patients performed with navigation. Although they did not take any formal training in orthopaedic oncology navigation, both surgeons were trained in navigation for knee prostheses. Between 2010 and 2012, we performed 124 bone tumor resections; of these, 78 (63%) cases were resected using intraoperative navigation assistance. During this period, our general indications for use of navigation included pelvic and sacral tumors and those tumors that were reconstructed with massive bone allografts to obtain precise matching of the host and allograft osteotomies. Seventy-eight patients treated with this technology were included in the study. Technical problems (crashes) and time for the navigation procedure were reported after surgery. Accuracy of the registration technique was defined and the surgical margins of the removed specimen were determined by an experienced bone pathologist after the surgical procedure as intralesional, marginal, or wide margins. To obtain these data, we performed a chart review and review of operative notes. RESULTS: In four patients (of 78 [5%]), the navigation was not completed as a result of technical problems; all occurred during the first 20 cases of the utilization of this technology. The mean time for navigation procedures during the operation was 31 minutes (range, 11-61 minutes), and the early navigations took more time (the regression analysis shielded R2 = 0.35 with p < 0.001). The median registration error was 0.6 mm (range, 0.3-1.1 mm). Registration did not improve over time (the regression analysis slope estimate is -0.014, with R2 = 0.026 and p = 0.15). Histological examinations of all specimens showed a wide bone tumor margin in all patients. However, soft tissue margins were wide in 58 cases and marginal in 20. CONCLUSIONS: We conclude that navigation may be useful in achieving negative bony margins, but we cannot state that it is more effective than other means for achieving this goal. Technical difficulty precluded the use of navigation in 5% of cases in this series. Navigation time decreased with more experience in the procedure but with the numbers available, we did not improve the registration error over time. Given these observations and the increased time and expense of using navigation, larger studies are needed to substantiate the value of this technology for routine use. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Cirugía asistida por computador en tumores óseos: principios generales / Computer assisted surgery in bone tumours: general principles

La mayoría de los tumores óseos primarios pueden ser tratados mediante una resección amplia —muchas veces asociada a terapias adyuvantes— sin comprometer la sobrevida del paciente. La posibilidad de una resección conservadora depende de la localización y tamaño del tumor y de las partes blandas circundantes. Una cuidadosa evaluación de estudios imagenológicos permite al cirujano elaborar un plan quirúrgico que permita una resección con márgenes adecuados, al mismo tiempo que conservar la mayor cantidad de tejido sano, de modo de obtener una extremidad funcional. A veces, la ejecución quirúrgica de lo planeado se hace muy difícil, y la precisión de esta puede resultar afectada. La cirugía guiada por computador se ha constituido en una herramienta útil en estas situaciones. Está basada en la creación de un plan virtual en 3 dimensiones mediante el procesamiento de imágenes de tomografía computada (TC) y resonancia nuclear magnética (RNM). Este plan puede ser reproducido en el escenario quirúrgico mediante la correspondencia entre este escenario virtual y la anatomía real del paciente. Esta tecnología puede permitir una mayor precisión en la ejecución de osteotomías en zonas difíciles como la pelvis, minimizando la resección innecesaria de tejido sano, pero manteniendo un margen oncológico adecuado. Describiremos los principios y el razonamiento que fundamentan el uso de la cirugía guiada por computador en la cirugía de tumores óseos, la cual se ha constituido en una herramienta útil para el manejo de situaciones clínicas específicas...

The majority of primary bone tumours can be effectively treated with wide resection —frequently associated with adjuvant therapy— without compromising the outcome of the patient. The feasibility of limb-sparing surgery in a particular scenario is dependent on the location and size of the tumour, as well as the involvement of the host bone and surrounding soft tissues. Careful evaluation of imaging studies allows the surgeon to plan the resection with adequate margins, while preserving as much normal tissues as possible, in order to achieve a functional limb. At times, the surgical execution of what was planned as resection becomes very difficult, and precision may be less than optimal. Computer-guided surgery has become a useful tool in these situations. It is based on the creation of a three-dimensional virtual plan by means of image processing from computed tomography (CT) and magnetic resonance (MRI) of the clinical situation. This plan is reproduced in the surgical field by means of the interaction between this virtual scenario and the actual anatomy of the patient. This technology could allow better precision in the execution of osteotomies in difficult areas, such as the pelvis, minimising unnecessary resection of normal tissue, while maintaining wide margins. A description is presented of the principles and rationale of computer-guided surgery for bone tumours, which has become a useful tool for the management of selected clinical situations...

Validación posoperatoria en la selección asistida por computadora de aloinjertos de fémur distal / Postoperative assessment in computer assisted selection of femur osteoarticular allograft

El objetivo de nuestro trabajo fue comparar dos grupos de pacientes tratados con trasplantes osteoarticulares del fémur distal en términos de evaluar: 1) el volumen del fémur distal del receptor y del trasplante, 2) la superficie articular de contacto del fémur distal del receptor y del trasplante, 3) el ángulo del valgo anatómico femoral del fémur distal del receptor y del trasplante. Materiales y métodos: se realizó una búsqueda retrospectiva entre 2002 y 2012 analizando a pacientes tratados con un trasplante osteoarticular de fémur distal. Se incluyó un total de 32 pacientes. Estos fueron divididos en dos grupos de acuerdo con el método de selección del trasplante: Grupo 1, conformado por 16 pacientes con trasplantes seleccionados mediante tomografía 2D y Grupo 2, 16 pacientes con trasplantes seleccionados a través de un método 3D. La evaluación fue realizada por un observador independiente y ciego para los dos grupos. Resultados: las diferencias en las pruebas de estimación de volumen y superficie articulares entre el donante y el receptor no fueron estadísticamente significativas (p>0,05). Sin embargo, la diferencia entre los ángulos de valgo del fémur receptor y el fémur donante, seleccionados por el método 2D fue significativa (p<0,05), mientras que la diferencia de estos ángulos en el método 3D no lo fue (p>0,05). Conclusión: el método de selección de un aloinjerto, mediante la utilización de un banco de huesos virtual 3D para la reconstrucción con un trasplante osteoarticular de femur distal, permite obtener una mejor alineación del miembro comparado con aquellos seleccionados solo con un método bidimensional. (AU)

The aim of our study was to compare two groups of patients treated with distal femur osteoarticular allograft in terms of: 1) the volume of the distal femur of the allograft and patient, 2) the articular surface contact, 3) the anatomical femoral valgus angle. Material and methods: a retrospective review was performed between 2002 and 2012 and all patients with an osteo-articular allograft of the distal femur were analysed. A total of 32 patients were included in the study. Patients were divided into two groups according to the selection method of the allograft: Group 1, 16 patients with allograft selected by 2D (CT) and Group 2, 16 patients selected through a 3D method. The evaluation was done by an independent and blind observer. Results: the differences in terms of volume estimation and joint surface contact between the donor allograft and patient distal femur were not statistically significant (p>0.05). However, the difference between the valgus angle showed significant differences between donor and patient femurs selected by the 2D method (p<0.05) but no difference in the group of patients selected by 3D method (p>0.05). Conclusion: the 3D method for allograft selection of the distal femur showed better results in limb alignment compared to 2D selection method. (AU)

Techniques in surgical navigation of extremity tumors: state of the art.

Image-guided surgical navigation allows the orthopedic oncologist to perform adequate tumor resection based on fused images (CT, MRI, PET). Although surgical navigation was first performed in spine and pelvis, recent reports have described the use of this technique in bone tumors located in the extremities. In long bones, this technique has moved from localization or percutaneous resection of benign tumors to complex bone tumor resections and guided reconstructions (allograft or endoprostheses). In recent years, the reported series have increased from small numbers (5 to 16 patients) to larger ones (up to 130 patients). The purpose of this paper is to review recent reports regarding surgical navigation in the extremities, describing the results obtained with different kind of reconstructions when navigation is used and how the previously described problems were solved.

3D Printed Models and Navigation for Skull Base Surgery: Case Report and Virtual Validation.

In recent years, computer-assisted surgery tools have become more versatile. Having access to a 3D printed model expands the possibility for surgeons to practice with the particular anatomy of a patient before surgery and improve their skills. Optical navigation is capable of guiding a surgeon according to a previously defined plan. These methods improve accuracy and safety at the moment of executing the operation. We intend to carry on a validation process for computed-assisted tools. The aim of this project is to propose a comparative validation method to enable physicians to evaluate differences between a virtual planned approach trajectory and a real executed course. Summarily, this project is focused on decoding data in order to obtain numerical values so as to establish the quality of surgical procedures.

Accuracy of Chest Wall Tumor Resection Guided by Navigation: Experimental Model.

Difficulty in identification wall chest tumors lead to unnecessary wide resections. Optical navigation and preoperative virtual planning are assets for surgeries that require exactness and accuracy. These tools enable physicians to study real anatomy before surgery and to follow an established pathway during procedure ensuring effectiveness. The aim of this paper is to demonstrate that Preoperative Virtual Planning is a useful tool in chest tumor interventions to define oncological margins successfully. Moreover, it is possible to use a virtual specimen in order to quantify accuracy. Optical navigation has been used in surgical procedures such as neurosurgery, orthopaedics and ENT over the last ten years. This principle is used in order to orientate the surgeon in three dimensional spaces during the surgery. Surgeons are guided intraoperatively with navigation and are able to obtain a correspondence between images acquired and processed before the surgery and the real anatomy.

Virtual Microscopy Large Slide Automated Acquisition: Error Analysis and Validation.

The aim of this work is to assess and analyze the discrepancies introduced in the reconstruction of an entire tumoral bone slice from multiple field acquisitions of a large microscopy slide. The reconstruction tends to preserve the original structural information and its error is estimated by comparing the reconstructed images of eight samples against single pictures of these samples. This comparison is held using the Structural Similarity index. The measurements show that smaller samples yield better results. The detected errors are introduced by the insufficiently corrected optical distortion caused by the camera lens, which tends to accumulate along the sample. Nevertheless, the maximum error encountered does not exceed 0.39 mm, which is smaller than the maximum tolerable error for the intended application, stated in 1 mm.

Transfer accuracy and precision scoring in planar bone cutting validated with ex vivo data.

The use of interactive surgical scenarios for virtual preoperative planning of osteotomies has increased in the last 5 years. As it has been reported by several authors, this technology has been used in tumor resection osteotomies, knee osteotomies, and spine surgery with good results. A digital three-dimensional preoperative plan makes possible to quantitatively evaluate the transfer process from the virtual plan to the anatomy of the patient. We introduce an exact definition of accuracy and precision of this transfer process for planar bone cutting. We present a method to compute these properties from ex vivo data. We also propose a clinical score to assess the goodness of a cut. A computer simulation is used to characterize the definitions and the data generated by the measurement method. The definitions and method are evaluated in 17 ex vivo planar cuts of tumor resection osteotomies. The results show that the proposed method and definitions are highly correlated with a previous definition of accuracy based in ISO 1101. The score is also evaluated by showing that it distinguishes among different transfer techniques based in its distribution location and shape. The introduced definitions produce acceptable results in cases where the ISO-based definition produce counter intuitive results.

Does intraoperative navigation assistance improve bone tumor resection and allograft reconstruction results?

BACKGROUND: Bone tumor resections for limb salvage have become standard treatment. Recently, computer-assisted navigation has been introduced to improve the accuracy of joint arthroplasty and possible tumor resection surgery; however, like with any new technology, its benefits and limitations need to be characterized for surgeons to make informed decisions about whether to use it. QUESTIONS/PURPOSES: We wanted to (1) assess the technical problems associated with computer-assisted navigation; (2) assess the accuracy of the registration technique; (3) define the time required to perform a navigated resection in orthopedic oncology; and (4) the frequency of complications such as local recurrence, infection, nonunion, fracture, and articular collapse after tumor resection and bone reconstruction with allografts using intraoperative navigation assistance. METHODS: We analyzed 69 consecutive patients with bone tumors of the extremities that were reconstructed with massive bone allografts using intraoperative navigation assistance with a minimum followup of 12 months (mean, 29 months; range, 12-43 months). All patients had their tumors reconstructed in three-dimensional format in a virtual platform and planning was performed to determine the osteotomy position according to oncology margins in a CT-MRI image fusion. Tumor resections and allograft reconstructions were performed using a computer navigation system according to the previously planned cuts. We analyzed intraoperative data such as technical problems related to the navigation procedure, registration technique error, length of time for the navigation procedure, and postoperative complications such as local recurrence, infection, nonunion, fracture, and articular collapse. RESULTS: In three patients (4%), the navigation was not carried out as a result of technical problems. Of the 66 cases in which navigation was performed, the mean registration error was 0.65 mm (range, 0.3-1.2 mm). The mean required time for navigation procedures, including bone resection and allograft reconstruction during surgery, was 35 minutes (range, 18-65 minutes). Complications that required a second surgical procedure were recorded for nine patients including one local recurrence, one infection, two fractures, one articular collapse, and four nonunions. In two of these nine patients, the allograft needed to be removed. At latest followup, three patients died of their original disease. CONCLUSIONS: The navigation procedure could not be performed for technical reasons in 4% of the series. The mean registration error was 0.65 mm in this series and the navigation procedure itself adds a mean of 35 minutes during surgery. The complications rate for this series was 14%. We found a nonunion rate of 6% in allograft reconstructions when we used a navigation system for the cuts. LEVEL OF EVIDENCE: Level IV, case series. See the Guidelines for Authors for a complete description of levels of evidence.