Complex Pelvic Anatomy Research Articles

Computed tomography landmark-based semi-automated mesh morphing and mapping techniques: Generation of patient specific models of the human pelvis without segmentation

Current methods for the development of pelvic finite element (FE) models generally are based upon specimen specific computed tomography (CT) data. This approach has traditionally required segmentation of CT data sets, which is time consuming and necessitates high levels of user intervention due to the complex pelvic anatomy. The purpose of this research was to develop and assess CT landmark-based semi-automated mesh morphing and mapping techniques to aid the generation and mechanical analysis of specimen-specific FE models of the pelvis without the need for segmentation. A specimen-specific pelvic FE model (source) was created using traditional segmentation methods and morphed onto a CT scan of a different (target) pelvis using a landmark-based method. The morphed model was then refined through mesh mapping by moving the nodes to the bone boundary. A second target model was created using traditional segmentation techniques. CT intensity based material properties were assigned to the morphed/mapped model and to the traditionally segmented target models. Models were analyzed to evaluate their geometric concurrency and strain patterns. Strains generated in a double-leg stance configuration were compared to experimental strain gauge data generated from the same target cadaver pelvis. CT landmark-based morphing and mapping techniques were efficiently applied to create a geometrically multifaceted specimen-specific pelvic FE model, which was similar to the traditionally segmented target model and better replicated the experimental strain results (R2=0.873). This study has shown that mesh morphing and mapping represents an efficient validated approach for pelvic FE model generation without the need for segmentation.

62. The virtual surgical pelvis: A highly-detailed 3D pelvic model for anatomical education and surgical simulation

Background: The surgical anatomy of the pelvis is highly complex. In case of rectal cancer the surgeon is challenged to perform a total mesorectal excision (TME) warranting complete removal of the tumor and preservation of the autonomic nerves. However, incomplete TME specimens and surgical damage to the nerves are still part of clinical reality. A highly-detailed 3D pelvic model would be an excellent tool to increase anatomical knowledge of the surgical anatomy of the pelvis. Visible Human Datasets (VHDs) are often used to create a 3D model, but they lack anatomical detail such as autonomic nerves and fasciae. Immunohistochemistry is an ideal method to study those key surgical structures at microscopic level. Recently, the Unified Anatomical Human (UAH) has been developed. UAH integrates heterogeneous anatomical data and will allow registration of patient-specific diagnostic images. In this study, we describe the development of The Virtual Surgical Pelvis (VSP) and its potential clinical value in anatomical education and surgical simulation. Material and methods: We selected 910 slices from a VHD that comprised the entire pelvis. All surgically relevant anatomical structures were manually segmented using Amira� software and three-dimensionally reconstructed using the UAH. The Online Anatomical Human (OAH), an online web-viewer, was developed as well. Paraffin embedded mega blocks of 1 female cadaveric pelvic exenteration specimen were sliced in transverse sections of 5 �m. A series was stained with Hematoxylin & Eosin and Masson�s Trichome and selected sections were immunohistochemically stained with S100, a pan-neuron marker. The autonomic nerves and fasciae were manually segmented in Amira� software, three-dimensionally reconstructed and integrated using the UAH. Results: Currently, the VSP presents most of the essential surgical anatomy of the pelvis, including the levator ani muscle and pudendal nerve, and can be interactively visualized in the UAH and OAH. Microscopic analysis of the female cadaveric specimen reveals the organization of autonomic nerves and fasciae in relation to pelvic organs. Conclusion: The VSP showing the complex pelvic anatomy is a potentially excellent tool for anatomical education. Registration of the VSP to patient-specific diagnostic images allows visualization of key surgical structures such as autonomic nerves and fasciae in relation to pelvic viscera. This makes surgical simulation a nearby future goal for all pelvic surgeons.

Successful Transcloacal Ureteral Stent Removal

We report a percutaneous transcloacal approach for removal of a ureteral stent in a 15-year-old girl with a cloacal anomaly, spinal dysraphism, and complex pelvic anatomy, including a bicornuate uterus, reconstructed hindgut neobladder, and duplicated left pelvic kidney. The patient had undergone 3 previous unsuccessful attempts at stent removal, 2 endoscopic attempts by way of her neobladder, and 1 percutaneous transcloacal attempt before successful removal.

Computer aided three-dimensional reconstruction and modeling of the pelvis, by using plastinated cross sections, as a powerful tool for morphological investigations

The aim of this study was to describe a method of developing a computerized model of the human female pelvis using plastinated slices. Computerized reconstruction of anatomical structures is becoming very useful for developing anatomical teaching, research modules and animations. Although databases consisting of serial sections derived from frozen cadaver material exist, plastination represents an alternative method for developing anatomical data useful for computerized reconstruction. A slice anatomy study, using plastinated transparent pelvis cross sections, was performed to obtain a 3D reconstruction. One female human pelvis used for this study, first plastinated as a block, then sliced into thin slices and in the end subjected to 3D computerized reconstruction using WinSURF modeling system (SURFdriver Software). To facilitate the understanding of the complex pelvic floor anatomy on sectional images obtained through MR imaging, and to make the representation more vivid, a female pelvis computer-aided 3D model was created. Qualitative observations revealed that the morphological features of the model were consistent with those displayed by typical cadaveric specimens. The quality of the reconstructed images appeared distinct, especially the spatial positions and complicated relationships of contiguous structures of the female pelvis. All reconstructed structures can be displayed in groups or as a whole and interactively rotated in 3D space. The utilization of plastinates for generating tissue sections is useful for 3D computerized modeling. The 3D model of the female pelvis presented in this paper provides a stereoscopic view to study the adjacent relationship and arrangement of respective pelvis sections. A better understanding of the pelvic floor anatomy is relevant to gynaecologists, radiologists, surgeons, urologists, physical therapists and all professionals who take care of women with pelvic floor dysfunction.

Survival, Local Recurrence, and Function After Pelvic Limb Salvage at 23 to 38 Years of Followup

Malignant pelvic tumors frequently pose challenges to surgeons owing to complex pelvic anatomy and local extension. External hemipelvectomy frequently allows adequate margins but is associated with substantial morbidity and reduced function. Limb salvage is an alternative approach when adequate margins can be achieved, but long-term function and survival are unclear. We therefore determined the long-term survival; development of late local recurrence and metastases; function; and need for further reconstructive procedures for patients undergoing limb salvage for treatment of malignant pelvic tumors. We retrospectively reviewed 60 patients treated with pelvic limb salvage before 1989. We reviewed medical records and sent questionnaires incorporating Musculoskeletal Tumor Society (MSTS) and Toronto Extremity Salvage scores to the 38 patients who had no evidence of disease in 1989; 15 patients responded. Minimum followup was 23 years (median, 30 years; range, 23-38 years). Overall survival rate of the 60 patients was 45%: 100% Stage IA, 75% Stage IB, 31% Stage IIB, and 0% Stage III were alive. Late local recurrence developed only in patients with chondrosarcoma (three of 24). Two patients developed late distant bone metastases. Function declined: the MSTS score of the 15 patients who completed a questionnaire decreased 23%. Two patients had further reconstructive procedures. At 23- to 38-year followup, we believe pelvic limb salvage is a reasonable treatment if satisfactory margins can be achieved. If a patient with pelvic sarcoma is free of disease 5 years after sarcoma resection, the subsequent risk of death from sarcoma appears to be low. Late local recurrence remains a risk in patients with pelvic chondrosarcoma. Patient-reported function of the salvaged limb declined with long-term followup. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Sports Hernia

Groin injuries are a common occurrence in elite-level athletes. These injuries can cause significant pain and disability, leading to prolonged periods of inactivity and consternation among athletes, coaches, athletic trainers, and physicians alike. The differential diagnosis for groin pain is vast and spans multiple disciplines, including orthopaedics, general surgery, urology, gynecology, and neurology. Sports hernias are one cause of chronic groin pain in athletes and are distinct entities from classic hernias. They are often caused by a deficient posterior wall of the inguinal canal, but may also involve concurrent injuries, such as conjoint and adductor tendinopathies and nerve entrapment. Understanding the complex lower abdominal, pelvic, and hip anatomy and pathophysiology of sports hernias is crucial to making an accurate diagnosis and providing appropriate treatment options. Newer, less invasive surgical repair techniques show promising early results in improving pain and decreasing recovery time.

Computer-assisted periacetabular screw placement: Comparison of different fluoroscopy-based navigation procedures with conventional technique

The current gold standard for operatively treated acetabular fractures is open reduction and internal fixation. Fractures with minimal displacement may be stabilised by minimally invasive methods such as percutaneous periacetabular screws. However, their placement is a demanding procedure due to the complex pelvic anatomy. The aim of this study was to evaluate the accuracy of periacetabular screw placement assessing pre-defined placement corridors and comparing different fluoroscopy-based navigation procedures and the conventional technique.For each screw an individual periacetabular placement corridor was preoperatively planned using the planning software iPlan CMF© 3.0 (BrainLAB). 210 screws (retrograde anterior column screws, retrograde posterior column screws, supraacetabular ilium screws) were placed in an artificial Synbone pelvis model (30 hemipelves) and in human cadaver specimen (30 hemipelves). 2D- and 3D-fluoroscopy-based navigation procedures were compared to the conventional technique. Insertion time and radiation exposure to specimen were also recorded. The achieved screw position was postoperatively assessed by an Iso-C3D scan. Perforations of bony cortices or articular surfaces were analysed and the screw deviation severity (difference of the operatively achieved screw position and the preoperatively planned screw position in reference to the pre-defined corridors) was determined using image fusion.Using 3D-fluoroscopy-based navigation, the screw perforation rate (7%) was significantly lower compared to 2D-fluoroscopy-based navigation (20%). For all screws, the deviation severity was significantly lower using a 3D- compared to a 2D-fluoroscopy-based navigation and the conventional technique. Analysing the posterior column screws, the screw deviation severity was significantly lower using 3D- compared to 2D-fluoroscopy-based navigation. However, for the anterior column screw, the screw deviation severity was similar regardless of the imaging method. Despite the advantages of the 3D-fluoroscopy-based navigation, this method led to significantly longer total procedure and fluoroscopic times, and the applied radiation dose was significantly higher.Percutaneous periacetabular screw placement is demanding. Especially for posterior column screws, due to a lower perforation rate and a higher accuracy in periacetabular screw placement, 3D-fluoroscopy-based navigation procedure appears to be the method of choice for image guidance in acetabular surgery.

Computer-Assisted Resection and Reconstruction of Pelvic Tumor Sarcoma

Pelvic sarcoma is associated with a relatively poor prognosis, due to the difficulty in obtaining an adequate surgical margin given the complex pelvic anatomy. Magnetic resonance imaging and computerized tomography allow valuable surgical resection planning, but intraoperative localization remains hazardous. Surgical navigation systems could be of great benefit in surgical oncology, especially in difficult tumor location; however, no commercial surgical oncology software is currently available. A customized navigation software was developed and used to perform a synovial sarcoma resection and allograft reconstruction. The software permitted preoperative planning with defined target planes and intraoperative navigation with a free-hand saw blade. The allograft was cut according to the same planes. Histological examination revealed tumor-free resection margins. Allograft fitting to the pelvis of the patient was excellent and allowed stable osteosynthesis. We believe this to be the first case of combined computer-assisted tumor resection and reconstruction with an allograft.

Sentinel Node Mapping in Vulvovaginal Melanoma Using SPECT/CT Lymphoscintigraphy

We report 2 cases of vulvovaginal melanoma in which sentinel node mapping, performed using Tc-99m filtered sulfur colloid SPECT/CT lymphoscintigraphy, added important information to that provided by planar imaging and played a critical role in surgical planning and subsequent management. In the first case, lymphoscintigraphy planar imaging showed only foci of tracer uptake in the right groin and an equivocal focus in the left groin. SPECT/CT precisely localized these radioactive foci to the right and left inguinal sentinel nodes. The patient then underwent bilateral inguinal sentinel node sampling. In the second case, F-18 FDG PET/CT performed prior to lymphoscintigraphy demonstrated a moderately FDG-avid right inguinal lymph node that was indeterminate in nature. SPECT/CT revealed this lymph node to be a radioactive sentinel lymph node that was seen in the right groin on planar imaging. The patient then underwent right inguinal sentinel node sampling. Because pathologic study showed metastasis to the sentinel node, a planned pelvic exenteration was canceled, and the patient was referred for systemic treatment. Preoperative SPECT/CT lymphoscintigraphy is ideal for mapping the unpredicted lymphatic drainage pathways within the complex pelvic anatomy and this technique may also be used in the preoperative workup of other gynecologic malignancies.

Preoperative 3 T MR imaging of rectal cancer: Local staging accuracy using a two-dimensional and three-dimensional T2-weighted turbo spin echo sequence

Purpose The purpose of our study was to evaluate the image quality and diagnostic performance of two-dimensional (D) turbo spin echo (TSE) and 3D T2-weighted TSE MR imaging in local staging of rectal cancer at 3 T. Materials and methods 3 T phased-array MR imaging was performed in 36 consecutive patients with biopsy-proven rectal cancer. High-resolution 2D TSE images in three planes and 3D TSE images of the rectum were obtained. Two independent observers performed an image quality assessment using eight image quality characteristics. All 2D and 3D datasets were evaluated separately. MR images were prospectively evaluated by two experienced radiologists in consensus with regard to local disease. Total mesorectal excision was used as the standard of reference. The sensitivity, specificity, positive and negative predictive value, and overall accuracy were calculated. Areas under the receiver operating characteristic (ROC) curve (AUC) were determined. Results Twenty-two patients who underwent a total mesorectal excision were enrolled in this study. Significantly more motion artifacts were present with 3D TSE imaging ( P = 0.04). The overall sensitivity, specificity, and accuracy of muscularis propria invasion in rectal cancer using 2D T2-weighted images were 100%, 66%, and 95%, respectively. There was a statistical significant greater AUC using 2D T2-weighted images compared to 3D T2-weighted MR images ( P = 0.04). The ROC curves describing the results of the interpretation of 2D and 3D T2-weighted datasets regarding perirectal tissue invasion showed no statistical significant difference ( P = 0.41). Conclusions In this study, high local staging accuracies with 3 T 2D T2-weighted MR imaging were demonstrated. 3D T2-weighted MR imaging cannot replace 2D MR imaging for local staging of rectal cancer. However, 3D MR imaging can be used for visualization of the complex pelvic anatomy for treatment planning purposes.

Three-Dimensional Transperineal Ultrasonography of the Pelvic Floor

With increasing awareness of the scope of pelvic floor disorders has come development and introduction into clinical practice of new imaging techniques, with increasing importance of ultrasonography. Complex pelvic floor anatomy, the conceptual difficulty in the basics of some pelvic floor disorders, and the uneven standardization of ultrasonographic techniques were the impetuses of this review. The purpose of this study was to review the basic anatomy of the pelvic floor and the transperineal ultrasonographic evaluation technique and to provide an overview of the current clinical use of 3-dimensional transperineal ultrasonography in the evaluation of the anterior and posterior pelvic floor compartments. A literature review illustrated with index cases from our center was conducted. Ultrasonography has been widely applied to evaluation of the anterior and posterior compartments of the pelvic floor. Three-dimensional ultrasonography has a role in improving pelvic floor assessment. Three-dimensional transperineal ultrasonography has been applied to evaluation of normal and pathologic pelvic floor anatomy. Practical application, through well-designed and sufficiently powered clinical studies, will establish the association between the clinical presentations of dysfunction with ultrasonographic findings.

Technik der perkutanen SI-Verschraubung mit Unterstützung durch konventionellen C-Bogen

During percutaneous iliosacral screw fixation, fluoroscopy with a conventional C-arm X-ray unit is still the standard procedure for intraoperative orientation. Lateral sacral images in combination with the inlet and outlet view are always necessary. Nevertheless, the complex pelvic anatomy makes it difficult to prevent malpositioning of screws. Defining the correct entry into the bone is the decisive step for ideal screw placement. The better this is defined, the larger safety margins will be concerning cortical perforation by the screws. In the lateral view, an entry ventral to the sacral canal has to be avoided as well as an entry into the cranial half of the first sacral vertebra. To improve the surgeon's three-dimensional orientation with the help of his personal experience and two-dimensional images, it is recommended to place the tip of the screws in the center of the sacrum (in AP view) whenever possible. Routinely performed postoperative CT imaging of 24 screws, consecutively implanted according to the standards described, revealed no case of malpositioning. Standard X-ray views in combination with standardized aiming of screw entry position and final screw thread position enable the surgeon to find the "safe zone" for iliosacral screw insertion and to prevent iliosacral screw malpositioning with high accuracy.

Three-dimensional digital rotation angiography for embolization therapy of uterine leiomyomas: first results

To evaluate three-dimensional rotational digital subtraction angiography (3D-RDSA) in the embolization of the uterine artery in the treatment of symptomatic uterine leiomyomas (fibroids). Eight women with complex pelvic vessel anatomy caused by large fibroids were embolized using 3D-RDSA. The raw data were sent to an external workstation, and video files with a resolution of one image/3 degrees and a scan range of 180 degrees in a surface-shaded display mode were produced. The primary goal was to assess an image intensifier angulation for the optimal visualization of the origin of the uterine artery. In addition, the intervention parameters were compared with those of 48 patients with standard angiography. The analysis revealed no single angulation that can be recommended for standard angiography. No statistical differences were found between both groups concerning fluoroscopy time, dosage area product and amount of administered contrast medium (p > 0.05). It can be stated that 3D-RDSA is a feasible method that facilitates the catheterization of the uterine artery even in patients with complex pelvic vessel anatomy, with the potential to reduce the radiation exposure and the amount of administered contrast medium in future embolization therapy of symptomatic uterine fibroids.

Sectional depiction of the pelvic floor by CT, MR imaging and sheet plastination: computer-aided correlation and 3D model.

The structures of the pelvic floor are clinically important but difficult to assess. To facilitate the understanding of the complicated pelvic floor anatomy on sectional images obtained by CT and MR imaging, and to make the representation more vivid, a computer-aided 3D model was created from a male and a female torso to develop a teaching tool. A male and a female cadaver torso were investigated by means of CT, MR imaging, and serial-section sheet plastination. A 3D reconstruction of the pelvic floor and adjacent structures was performed by fusion of CT and MR imaging data sets with sheet plastination sections. Corresponding sections from all three methods could be compared and visualized in their 3D context. Sheet plastination allows distinction of connective tissue, muscles, and pelvic organs down to a microscopic level. In combination with CT, MR imaging, and sheet plastination a 3D model of the pelvic floor offers a better understanding of the complex pelvic anatomy. This knowledge may be applied in the diagnostic imaging of urinary incontinence or prolapse and prior to prostate surgery.