3D Computed Tomography Reconstruction Research Articles

The Use of Injectable Chitosan/Nanohydroxyapatite/Collagen Composites with Bone Marrow Mesenchymal Stem Cells to Promote Ectopic Bone Formation In Vivo

The aim of this study was to evaluate ectopic in vivo bone formation with or without rat bone mesenchymal stem cells (rBMSCs) of an injectable Chitosan/Nanohydroxyapatite/Collagen (CS/nHAC) composite. The CS/nHAC composites were injected subcutaneously into the backs of Wistar rats with freshly loaded rBMSCs at a density of 10 × 106 cells/mL, and the CS/nHAC composites without cells were used as negative controls. New bone formation, degradation of composites, and degree of calcification were evaluated by Computed Tomography (CT) and three‐dimensional (3D) CT reconstruction. Histological evaluations were performed to further assess bone structure and extracellular matrix by HE and Masson staining. The inflammatory reactions related to osteogenesis were also investigated in the present study. In comparison with the CS/nHAC composites, this study revealed that CS/nHAC/rBMSCs composites showed relatively higher percentage of calcification, better establishment of ECM, and less degradation rate. Meanwhile, different extents of inflammatory reactions were also observed in the CS/nHAC and CS/nHAC/rBMSCs explants at 2 and 4 weeks after implantation. Altogether, CS/nHAC/rBMSCs composites are superior to CS/nHAC composites in ectopic bone formation. In conclusion, the rBMSCs‐seeded CS/nHAC composites may be beneficial to enhancing ectopic bone formation in vivo.

Effect of Three-Dimensional Computed Tomography Reconstructions on Reliability of Classification of Calcaneal Fractures

This study evaluated the impact of three-dimensional (3D) volume-rendering computed tomography (CT) reconstructions on the inter- and intraobserver reliability of six commonly used classification systems in the assessment of calcaneal fractures. Four independent observers with different levels of clinical training evaluated 64 fractures according to the classifications of the Orthopaedic Trauma Association (OTA), Essex-Lopresti, Sanders, Crosby, Zwipp, and Regazzoni, using two-dimensional (2D) CT scans with multiplanar reconstructions and 3D volume-rendering reconstructions. Interobserver reliability was moderate for the OTA, Essex-Lopresti, Sanders, Crosby, and Regazzoni classifications with 2D CT scans and 3D CT reconstructions. The Zwipp classification was poor with 2D CT scans and improved to moderate with 3D reconstructions. Intraobserver reliability with 2D CT scans was good for the Essex-Lopresti classification and moderate for the OTA, Sanders, Crosby, Zwipp, and Regazzoni classifications. After the addition of 3D reconstructions, all classifications showed moderate intraobserver reliability. According to the findings of this study, the additional use of 3D reconstructions is of minor value when used in conjunction with the classifications of the OTA, Sanders, Crosby, Regazzoni, and Essex-Lopresti. If calcaneal fractures are assessed with the Zwipp classification, 3D reconstructions could be used to achieve comparable reproducibility compared to other classifications. 3D reconstructions may have other benefits not evaluated in the presented study and may give useful information not captured by current classification systems.

Structured Light Scanning to Evaluate Three-Dimensional Anthropometry in HIV Facial Lipoatrophy

The psychological and social impact of the lipodystrophy syndrome on HIV-infected individuals may be quite considerable and adversely affect their quality of life. Currently no validated assessment tool for facial lipoatrophy is available. The main objective of this paper is to evaluate the reliability of interactive anthropometric landmark localization based on digitized 3D facial images. By comparing both computed tomography (CT) and structured light scanning we try to demonstrate that surface scanning shows a higher sensitivity in measuring facial reference points. Besides, we evaluate the reproducibility of facial 3D white-light scans. Three HIVpositive men attending our plastic surgery outpatient clinic for treatment of facial lipodystrophy were enrolled in the study. Localization of anthropometric landmarks measurements was performed on the patients. All patients underwent a facial CT and a facial white-light scanning on the same day. The inter-landmark distances measured on facial models developed from CT aided with VirSSPA 3D software and structured light scanning were compared to the real human models. We found that facial distances measured in the CT 3D reconstruction showed a mean error margin of 0.357 cm from the real distances measured on patients. On the contrary, mean error margin with the white-light scanning was of 0.096 cm. In both cases, measurements were found to be statistically significant (p < 0.05). When compared to CT reconstructions, white-light surface scanning offers a more accurate landmark localization as well as reliable reconstructions of up to less than the tenth of a millimetre as average when compared to real measurements on facial human models.

Influence of the anatomic characteristics of the pulmonary vein ostium, the learning curve, and the use of a steerable sheath on success of pulmonary vein isolation with a novel multielectrode ablation catheter

Anatomic variability of the pulmonary vein (PV) ostium may adversely affect isolation rates with the circular fixed-size pulmonary vein ablation catheter (PVAC). We wanted to assess the influence on PV isolation rates of anatomic characteristics of the ostium, increasing experience of four different operators, and additional use of a steerable sheath. In the first 190 patients (pts) undergoing PVAC ablation, minimum/maximum diameter, area and shape of the PV ostia, and the length of a common ostium were analysed from computed tomography 3D reconstructions of the left atrium and related to isolation rates. In addition, a comparison was drawn between pts at the beginning and after completion (isolation of all PVs in ≥ 85% of pts) of the learning curve, and the effect of a steerable sheath was assessed. Pulmonary vein isolation was achieved with the PVAC alone in 85% of pts and in 94% of veins after a median procedure and ablation time of 154 [interquartile ranges (IQR): 120, 200] and 51 (IQR: 38, 70) min. An increase in isolation rates was observed after the first 60 pts (73 vs. 90% of pts; P< 0.01; 88 vs. 96% of PVs; P< 0.001), coincident with routine use of a steerable sheath. Anatomic characteristics (larger minimum diameter and area) identified unsuccessful isolation only of the left inferior PV at the beginning of the learning curve. Pulmonary vein isolation rates using this catheter are high. Anatomic variability of PV ostia modestly affects PV isolation rates. Standard use of a steerable sheath plays a major role in increasing isolation rates and overcoming 'difficult' anatomies.

Paper # 193: 3-D CT Analysis of Tunnel Widening in ACL Reconstruction Using Allograft Tendons versus Hamstring Autografts

Tunnel widening after ACL reconstruction is significantly increased with the use of allografts compared to autografts. Tunnel widening has been described after ACL reconstruction and is explained by mechanical and biological phenomena. The aim of this study was to examine the feasibility of Computed Tomography 3D reconstructions to study tunnel widening after ACL surgery. Secondly, the goal was to examine differences in tunnel widening between allo- vs. autografts and between RCI vs. BioRCI among autografts. Thirty-five patients underwent ACL reconstruction performed by a single surgeon (PV). A deep-frozen tibialis posterior tendon allograft was used in 10 patients, while in 25 patients both autologous semitendinosus and gracilis tendons were implanted. All grafts were fixed by a suspensory device on the femoral cortex (Endobutton, Smith&Nephew) and with a screw (BioRCI for allografts, RCI (n=12) or BioRCI (n=13) for autografts, Smith&Nephew) and staple on the tibia. The subjects were evaluated at a minimal follow-up of 1 year using a CT-based 3D reconstruction of both femoral and tibial tunnels. Tunnel widening was measured using a best-fit cylinder model by a least square criterium using the MIMICS software program (MIMICS v.13, Materialise, Belgium). On the femoral side, tunnels were enlarged by 53% in the allograft group versus 35% for the autograft group. On the tibial side, tunnels were enlarged 48% in the allograft group versus 38% in the autograft group. These differences were significant. The use of BioRCI screws did not significantly alter the widening compared to RCI screws. Tunnel widening after ACL reconstruction is significantly increased with the use of allografts compared to autografts. No differences were observed between BioRCI and RCI cases. The biology of intra-tunnel phenomena during graft healing is influenced by graft origin.

Paper # 192: Therapeutic Advantage in Selective Ligament Augmentation for Partial Tears of Anterior Cruciate Ligament

Background: The selected anterior cruciate ligament (ACL) augmentation procedure, either anteromedial (AM) or posterolateral (PL), has been introduced as a treatment of choice for the repair of partial ACL ruptures which is based on the double bundle anatomy of the ACL. The preserved mechanoreceptor and vascularity in the remnant ACL is thought to provide neurological and biological benefits. Although enhanced knee joint proprioception in ACL augmented patients has been previously reported, there are no studies that assess the biological healing advantages of the graft after the ACL augmentation procedure. Hypothesis: Selected ACL augmentation for partial tears can promote the healing process of the grafted tendon and provide better biomechanical properties compared to ACL reconstruction of a complete tear. Study Design: Controlled Laboratory Study Methods: Two different ACL injury models were established in normal rats; 1) ACL augmentation of a partial tear model and 2) an ACL reconstruction of a complete tear model. To biologically assess the models, cell infiltration and angiogenesis in the grafted tendons were analyzed using hematoxylin/eosin staining and immunostaining using isolectin B4 respectively. Additionally, rat-specific type III collagen were evaluated by immunohistochemical staining to determine the extent of healing, while anti-rat neurofilament antigen was assessed to examine proprioceptive recovery. Biological assessments of the augmented and reconstructed grafts were conducted at week 2 postoperatively and biomechanical testing was performed at week 8 postoperatively. Results: A significantly greater number of infiltrating cells were observed in the augmented graft than in the reconstructed graft as was an increase in angiogenesis. There was also an increased amount of rat-specific type III collagen and anti-rat neurofilament antigen expressed in the augmented graft compared to the reconstructed graft. Biomechanical testing showed that failure load was significantly higher in the augmentation group compared with the reconstruction group. Conclusions: Selected ACL augmentation for partial tears could have biological benefits to promote the grafted tendon resulting in a better biomechanical healing when compared to complete ACL reconstruction. Paper # 193: 3-D CT Analysis of Tunnel Widening in ACL Reconstruction Using Allograft Tendons versus Hamstring Autografts STEVEN CLAES, MD, BELGIUM CEDRIC ROBBRECHT, MEDICAL STUDENT, BELGIUM PETER MAHIEU, MD, BELGIUM PETER VERDONK, MD, PHD, BELGIUM · University Hospitals Gent, Gent, BELGIUM Summary: Tunnel widening after ACL reconstruction is significantly increased with the use of allografts compared to autografts. Abstract: Objective: Tunnel widening has been described after ACL reconstruction and is explained by mechanical and biological phenomena. The aim of this study was to examine the feasibility of Computed Tomography 3D reconstructions to study tunnel widening after ACL surgery. Secondly, the goal was to examine differences in tunnel widening between allovs. autografts and between RCI vs. BioRCI among autografts. Material and Methods: Thirty-five patients underwent ACL reconstruction performed by a single surgeon (PV). A deep-frozen tibialis posterior tendon allograft was used in 10 patients, while in 25 patients both autologous semitendinosus and gracilis tendons were implanted. All grafts were fixed by a suspensory device on the femoral cortex (Endobutton, Smith&Nephew) and with a screw (BioRCI for allografts, RCI (n 12) or BioRCI (n 13) for autografts, Smith&Nephew) and staple on the tibia. The subjects were evaluated at a minimal follow-up of 1 year using a CT-based 3D reconstruction of both femoral and tibial tunnels. Tunnel widening was measured using a best-fit cylinder model by a least square criterium using the MIMICS software program (MIMICS v.13, Materialise, Belgium). Results: On the femoral side, tunnels were enlarged by 53% in the allograft group versus 35% for the autograft group. On the tibial side, tunnels were enlarged 48% in e199 ABSTRACTS Objective: Tunnel widening has been described after ACL reconstruction and is explained by mechanical and biological phenomena. The aim of this study was to examine the feasibility of Computed Tomography 3D reconstructions to study tunnel widening after ACL surgery. Secondly, the goal was to examine differences in tunnel widening between allovs. autografts and between RCI vs. BioRCI among autografts. Material and Methods: Thirty-five patients underwent ACL reconstruction performed by a single surgeon (PV). A deep-frozen tibialis posterior tendon allograft was used in 10 patients, while in 25 patients both autologous semitendinosus and gracilis tendons were implanted. All grafts were fixed by a suspensory device on the femoral cortex (Endobutton, Smith&Nephew) and with a screw (BioRCI for allografts, RCI (n 12) or BioRCI (n 13) for autografts, Smith&Nephew) and staple on the tibia. The subjects were evaluated at a minimal follow-up of 1 year using a CT-based 3D reconstruction of both femoral and tibial tunnels. Tunnel widening was measured using a best-fit cylinder model by a least square criterium using the MIMICS software program (MIMICS v.13, Materialise, Belgium). Results: On the femoral side, tunnels were enlarged by 53% in the allograft group versus 35% for the autograft group. On the tibial side, tunnels were enlarged 48% in e199 ABSTRACTS

Comparison of common hard tissue cephalometric measurements between computed tomography 3D reconstruction and conventional 2D cephalometric images

To compare cephalostat two-dimensional (2D) measurements to 3D computed tomography (CT) measurements in order to determine the compatibility of CT landmarks identification for orthodontic purposes. Ten human skulls were x-rayed in conventional lateral cephalogram and then scanned with spiral CT. Twenty-eight linear and angular cephalometric measurements were registered on the 2D lateral cephalogram and compared to the same measurement on the 3D CT scan. Significance of the results was determined by t-test for paired differences (P < .05). No difference was found between 2D and 3D images for linear or ratio measurements. As for the angular cephalometric measurements, only the sella turcica dependent measurements, showed significant difference between 2D and 3D. The compatibility of using most of the common orthodontic examined cephalometric measurements on 3D volume rendered image was proven except for the angular measurements that included sella anatomic landmark.

Scapular body fractures: results of operative treatment

The authors operated on 22 patients with scapular body fractures, with a mean age of 35 years. The minimal follow-up was 12 months. All patients were treated from the Judet posterior approach. The study included 14 cases of an isolated body fracture, three of scapular body fracture combined with fracture of the scapular neck and five of glenoid fossa fracture. In all 14 cases where a 3D computed tomography (CT) reconstruction was performed prior to operation, intraoperative findings corresponded to this reconstruction. In eight cases without preoperative 3D CT reconstruction, the correct type of fracture was identified in only two cases. We also identified three basic types of fractures of the lateral border of the scapula. The anatomical relationship between the glenoid fossa and scapular body, congruency and stability of the shoulder joint was achieved in all cases. The average constant score was 94.

Computed tomography measurement of the auricle in Han population of north China

A large number of anthropometric studies of the human auricle have been conducted in various populations. However, data from Han Chinese population are currently not available. The morphology of the auricle is highly complex. Consequently, traditional direct measurement techniques are unable to provide sufficient detail and accuracy. The present study sought to provide anthropometrical data on the auricles of Han Chinese individuals using a three-dimensional (3D) computed tomography (CT) reconstruction technique. A total of 485 data sets were utilised for this study. This sample consisted of data from 241 females aged 18-75 years and 244 males aged 18-74 years. All participants were categorised by gender and further into three age groups. Twelve anthropometrical dimensions of normal auricles were measured with 3D CT. Auricular, tragal, lobular and conchal indices were calculated to further examine the auricles. Earlobes were classified into three basic groups according to the angle of the junction of the earlobe with the cheek. Few of the anthropometrical data showed significant bilateral differences in auricular dimensions. The height of the tragus, lobular length, lobular width, conchal width, protrusion at tragal level and inclination angle of auricles showed no significant differences between males and females. All the linear dimensions of auricles, except the height of the tragus, conchal length and width, increased with age for both males and females. Protrusion at the superaurale and tragal levels showed a decrease of between 4% and 9% for males and 4% and 10% for females across all age groups. This study is the first to report CT measurement of normal auricles in a northern Han Chinese population. We found that this method enabled the complexity of the ear to be measured easily and accurately. Increasing our knowledge of normal auricular dimensions will be beneficial for plastic surgeons.

Three-Dimensional Localization of Implanted Biomaterials in Anatomical and Histological Specimens Using Combined X-Ray Computed Tomography and Three-Dimensional Surface Reconstruction: A Technical Note

For adequate histological processing of implanted biomaterials or tissue-engineered constructs, it is sometimes essential to obtain insight into the localization of structures inside the tissue samples. Observation of three-dimensional (3D) surface reconstruction, including basic photorealistic texture characteristics as surface pattern and color combined with X-ray computed tomography 3D reconstruction at different levels, is a useful approach to localize anatomical or implanted structures within experimental tissue samples. Because of the possible observation of structures of interest in a 3D environment, fusion of these techniques can greatly facilitate histological processing.

Esophagus imaging for catheter ablation of atrial fibrillation: comparison of two methods with showing of esophageal movement

This study aims to evaluate whether visualization and integration of the computed tomography (CT) scan of the left atrium (LA) and the esophagus into the three-dimensional (3D) electroanatomical map the day before ablation is accurate compared with integration of an esophagus tag into the electroanatomic LA map visualizing the anatomic relationship during the radiofrequency ablation or whether esophagus movement prohibits esophagus visualization the day before ablation. Eighteen patients with highly symptomatic atrial fibrillation underwent cardiac CT imaging the day before pulmonary vein ablation. Before CT imaging, a gastric tube was introduced into the esophagus allowing its CT 3D reconstruction. During radiofrequency ablation, mapping of the esophagus was performed and integrated into the LA 3D map. By comparing the position of the gastric tube during CT on day 1 with real-time anatomical mapping using a 3D navigation catheter on day 2, an average distance of more than 10 mm was found in six of 18 patients (33%). In six of 18 (33%), the maximal distance between day 1 and day 2 was even more than 15 mm. Reliance on CT images, even if acquired within 24 h before ablation, does not ensure adequate intraprocedural localization of the esophagus or enhance recognition of esophageal motility.

The three-dimensional anatomy of proximal humeral fractures

Three-dimensional (3D) computed tomography (CT) reconstructions have the potential to convey the anatomy of proximal humeral fractures more realistically than do standard 2D images. Proximal humeral fractures in 248 adult patients were examined prospectively using 3D CT reconstructions. To our knowledge, this represents the largest reported series of such fractures examined by this method. Of 248 fractures examined by a 3D classification system, 14% were of the 2 Part type, 36% were 3 Part, 21% were Shield fractures, 13% were isolated tuberosity injuries, and 16% were fracture dislocations. This study led to a modification of the Neer classification system. The frequency of each type of injury in this new classification is presented and a technique for viewing 3D images is suggested which maximizes their usefulness. Level 2; Clinical, observational, and prospective.

Three-dimensional pelvimetry by computed tomography

This study was undertaken to assess the agreement of computed tomography (CT) pelvimetry with different postprocessing techniques. CT data sets of 25 patients were retrospectively analysed. There were no CT examinations performed solely for pelvimetry, and there was no radiation exposure for study purposes. Six pelvimetric measurements were obtained by two independent observers in four data sets of each patient, i.e. on biplanar topograms, multiplanar reconstructions of 1-mm slices, volume-rendered images of the same data and volume-rendered images based on 5-mm-thick images. Interobserver agreement and variability were determined by Bland-Altman analysis. A human skeleton was also scanned and measured with the same techniques and by ruler as reference. With a correlation coefficient of 0.98, interobserver agreement was best for assessing 3D volume-rendered images reconstructed from 1-mm-thick slices. Interobserver variability was very good for sagittal outlet and midpelvic diameter, transverse inlet diameter and obstetric conjugate (correlation coefficients 0.96-0.99) but limited for intertuberous and interspinous distance. CT and ruler measurements of the skeleton showed excellent agreement. Pelvimetry can be obtained with low interobserver variability on 3D volume-rendered CT reconstructions. Thus, CT pelvimetry is suitable to gain exact knowledge of pelvic anatomy to identify relevant parameters for dystocia in retrospective studies.

Interactive surgery simulation for the nose augmentation using CT data

Surgery to reshape the nose with an implant has been a regular procedure for enhancing a patient’s appearance and self-confidence. The purpose of this study was to establish a computed tomography (CT) based three-dimensional assistant plastic surgery systems, which can provide the patients with realistic prediction of their own postoperative appearance in computer and specifically produce a nose implant for an individual patient. Preoperative CT data and 3D reconstruction techniques were employed to generate 3D model of the patient’s skull. 3D collision detection and finite elements model deformation were then applied to simulate nose augmentation surgery and predict postoperative appearance. According to the patient’s expectation, digital models of the nose implants were constantly modified. When the patient is satisfied with the simulated results, custom made silicone implants were produced by a computer controlled device. Accurately regeneration of 3D images and realistic operative simulations could be achieved with this system. The implants produced exactly conformed to the results of simulation. No curving and reshaping were needed during operating. The clinical results extremely matched with the simulations. The system enhances surgeon patient communication and facilitates preoperative planning. It is especially desirable for implant surgery with less guesswork of size, contour, and orientation of the implant. The best chance of optimal results could be achieved.

The Use of Improvised Bullet Markers with 3D CT Reconstruction in the Evaluation of Penetrating Trauma

Radio-opaque markers placed over entry and exit wounds, have been used to help evaluate penetrating injuries and provide a permanent record of wound location on plain radiographs. To date there...

Cone Beam Computed Tomography 3D Reconstruction of the Mandibular Condyle

To determine the ideal window level and width needed for cone beam computed three-dimensional (3D) reconstruction of the condyle. Linear dimensions were measured with a digital caliper to assess the anatomic truth for 50 dry human mandibular condyles. Condyles were scanned with the i-CAT cone beam computed tomography (CBCT) and 3D-models were reconstructed. Three linear three-dimensional measurements were made on each of the 50 condyles at 8 different Hounsfield unit (HU) windows. These measurements were compared with the anatomic truth. Volumetric measurements were also completed on all 50 condyles, at 23 different window levels, to define the volumetric distribution of bone mineral density (BMD) within the condyle. Significant differences were found in two of the three linear measurement groups at and below the recommended viewing window for osseous structures. The most accurate measurements were made within the soft tissue range for HU window levels. Volumetric distribution measurements revealed that the condyles were mostly comprised of low-density bone, and that condyles exhibiting significant changes in linear measurements were shown to have higher percentages of low-density bone than those condyles with little change from the anatomic truth. CBCT assessment of the mandibular condyle, using the 3D reconstruction, is most accurate when accomplished at density levels below that recommended for osseous examination. However, utilizing lower window levels which extend into the soft tissue range, may compromise one's capacity to view the bony topography.

Analysis of calcaneonavicular coalitions using multi-planar three-dimensional computed tomography

Computed tomography (CT) is the current imaging standard for confirming the diagnosis of a calcaneonavicular coalition. The purpose of this study was to evaluate three-dimensional (3D) multi-planar CT images of calcaneonavicular coalitions and adjacent tarsal relationships, compared to controls, in order to obtain an understanding of the 3D anatomy for classification and as an aid to surgical resection. All patients who underwent CT of bilateral feet at our institution to evaluate a suspected calcaneonavicular coalition between 9/2005 and 3/2008 were retrospectively reviewed. Seventy-four feet (37 patients) were included in this analysis. In addition, 12 patients with a presumed normal calcaneonavicular relationship, who underwent CT of bilateral feet for various other diagnoses, were included as a control cohort. Seven measurements were performed on the 3D reconstructions to quantify the shape of the coalition (dorsal and plantar widths of the calcaneal and navicular contributions, coalition depth of the calcaneal and navicular contributions, and coalition length). The coalitions were classified into four types based on their appearance and their relationship to adjacent tarsal bones. 32/37 patients (86%) were noted to have bilateral involvement (69 coalitions). Coalitions were categorized into four types: Type I (forme fruste)-28%, Type II (fibrous)-23%, Type III (cartilaginous)-45% and Type IV (osseous)-4%. The average shape of the coalition was found to be a curved wedge, which was on average 16 mm wide dorsally, 7 mm wide on the plantar surface, 10 mm in length, and 25 mm in depth. 3D CT reconstructions enabled the classification of the spectrum of calcaneonavicular coalitions. The shape of the cuboid was found to correlate with the extent of ossification. In Type I or II coalitions, the cuboid extended medially plantar to the fibrous connection. In more complete Type III or IV coalitions, the cuboid was "squared off" and remained lateral to the osseous bridge. An understanding of the 3D anatomy is important when diagnosing milder forms of coalitions, and during resection in order to avoid iatrogenic injury to the calcaneus, head of the talus, or cuboid.

Étude de la fiabilité des mesures de l’incidence pelvienne dans l’analyse de l’équilibre sagittal du bassin

The pelvic incidence (PI) is an anatomic parameter independent of the spatial orientation of the pelvis. However, measuring the PI remains a technically difficult task. PI is determined from radiographic construction which has several consequences. Imperfect radiographic incidence may compromise optimal conditions for measurement. Anatomic remodeling of the sacral plate can also have an impact on rigorous measurement of the PI. Several solutions have been proposed in the literature in order to obtain equivalent measurements. The proposed methods (Duval-Beaupere, Vialle) appear logical, but remain to be validated. The purpose of this study was to determine whether the angle measured on the plain x-ray is affected by the radiographic quality of the image and to determine whether the "variant pelvic incidence" (VPI) using a reference constituted by the posterior aspect of the sacrum, can be accepted as a valid equivalent to PI in the event of anatomic remodeling.This was a prospective study conducted in 50 patients. The PI and the VPI were measured on 3D computed tomography reconstructions which allowed three series of measurements: in a strictly lateral view, in a view with the position of the femoral heads shifted in the horizontal plane, and a view with the position of the femoral heads shifted in the vertical plane. Statistical analysis was applied to compare the three series of measures in order to search for a significant difference for the two angles under consideration (PI and VPI) dependent on the position of the pelvis.There was no significant difference in PI as a function of the position of the femoral heads: the coefficients of variation were all greater than 0.98 (p<0.01). For VPI, there was a significant difference between the theoretical ideal position and the horizontal shift of the femoral heads (p<0.05). Average measurements of PI and VPI were statistically different for each individual (p<0.05), with no identifiable relationship between the two values (PI and VPI).Pelvic incidence is a reliable measure, even if the quality of the x-ray is not perfect. Conversely, the variant, using the posterior aspect of the sacrum, is highly dependent on pelvic orientation, with significant differences with position. We were unable to establish a relation between PI and VPI. In practice, it would be licit to consider that the straight line between the two femoral heads indicates the center of the femoral heads. On the contrary, it would not be wise to consider the posterior aspect of the sacrum as a reliable reference.

Pathognomonic radiological signs for predicting prognosis in patients with chronic atlantoaxial rotatory fixation

The authors conducted a study to assess the correlation between radiological features and clinical courses in patients with chronic atlantoaxial rotatory fixation (AARF) and to determine diagnostic imaging signs for predicting prognosis. There were 24 patients (eight boys and 16 girls) whose mean age was 7.8 years (range 4-14 years) and in whom AARF was diagnosed. The mean follow-up duration was 3.7 years (range 5 weeks-12 years). There were two groups of patients: 15 patients who visited the hospital less than 8 weeks after symptom (torticollis) onset comprised the acute group, and nine patients in whom the diagnosis of AARF was established later than 3 months after symptom onset comprised the chronic group. The chronic group was divided into two subgroups: those in whom the closed reduction could be achieved and those in whom it could not. Clinical data and radiographic studies, including plain radiographs and plain and three-dimensional (3D) computed tomography (CT) reconstructions, were reviewed retrospectively. A deformity of the superior C-2 facet joint was frequently observed in the group of patients with chronic AARF (p < 0.0001). This sign represented a risk factor for recurrent dislocation (p = 0.0003, Fisher exact test). Prominent lateral inclination of C-1 was an impeding factor for reduction of chronic AARF (p < 0.0001, analysis of variance with Fisher post hoc test). Greater than 20 degrees of lateral inclination of the atlas indicated an irreducible subluxation (p = 0.0023, Fisher exact test). Both facet joint deformity and lateral inclination observed on 3D CT reconstructions can be useful signs to predict the prognosis and the treatment of choice in patients with chronic AARFs.

Three-dimensional reconstruction based on images from spiral high-resolution computed tomography of the temporal bone: anatomy and clinical application

The aim of this study was to investigate the usefulness of a three-dimensional (3D) reconstruction of computed tomography (CT) images in determining the anatomy and topographic relationship between various important structures. Using 40 ears from 20 patients with various otological diseases, a 3D reconstruction based on the image data from spiral high-resolution CT was performed by segmentation, volume-rendering and surface-rendering algorithms on a personal computer. The 3D display of the middle and inner ear structures was demonstrated in detail. Computer-assisted measurements, many of which could not be easily measured in vivo, of the reconstructed structures provided accurate anatomic details that improved the surgeon's understanding of spatial relationships. A 3D reconstruction of temporal bone CT might be useful for education and increasing understanding of the anatomical structures of the temporal bone. However, it will be necessary to confirm the correlation between the 3D reconstructed images and histological sections through a validation study.