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Nondisplaced and minimally displaced sacral insufficiency fractures are increasingly being recognized as a cause of immobilizing low back pain in the elderly. These insufficiency fractures are most accurately diagnosed by visualizing sacral bone marrow edema on magnetic resonance imaging, which is the radiologic imaging modality with the highest sensitivity for identifying these fractures. Successful treatment options range from nonsurgical (eg, bed rest, pain medication, mobilization, antiosteoporotic medication, low-intensity-pulsed ultrasound, etc.) to surgical management (ie, sacroplasty and/or osteosynthesis with iliosacral screws or lumbosacral hinge fixation with or without application of reinforcing bone cement). The appropriate surgical treatment for frail subjects requires a less-invasive technique that establishes full weight-bearing stability for successful early remobilization of affected elderly and multimorbid individuals. Iliosacral screw osteosynthesis with a single C-arm is a common surgical technique for stabilizing the posterior pelvic ring after traumatic instabilities or fractures of the sacrum. Bilateral injuries are generally addressed from both sides of the pelvis. This article describes the surgical technique of 3D image-guided transsacral screw fixation for unilateral and bilateral nondisplaced sacral insufficiency fractures in the elderly using a single-sided approach, and specifies the associated preoperative and postoperative management. The procedure is illustrated in an instructional video that demonstrates step-by-step, how the navigated surgical procedure is performed.

Background Up to 7.5% of tined-lead removals in patients having sacral neuromodulation (SNM) therapy are associated with a lead breakage. It is still unclear what adverse effects can be caused by unretrieved fragments. The aim of our study was to describe the lead removal technique we have been using for the last 2 years in our centre. Methods We retrospectively enrolled patients who had lead removal between January 2018 and January 2020 using our standardized technique. The novelty of the technique is in the use of the straight stylet, which is available in the quadripolar tined-lead kit. The stylet gives the electrode greater stiffness, reducing interactions with surrounding tissues and probability of damage or breakage during removal. Results In 59 patients (42 women, mean age 57.2 years [range 40–79 years]) the lead was removed using our standardized technique. In 44 of 59 patients, the tined-lead was removed within 2 months from the SNM-test, due to lack of beneficial effects. In 15 patients the electrode was removed because of failure of definitive implantation. Meantime from definitive implantable pulse generator (IPG) implantation to lead removal was 67.9 months. We recorded only 1 case of lead-breakage during removal: a female patient with a non-tined lead fixed on sacral bone, placed 18 years previously using an open technique. Conclusions Lead breakage during removal is not uncommon and adverse effects of retained fragments may occur. Our technique has been safely used for the last 2 years in our centre, with no episodes of lead breakage or retained fragments, except for one non-tined electrode.

Background Spinal perineural Tarlov’s cysts (TCs) are considered incidental findings that occasionally might exert pressure upon nerve roots and correspond with patients’ signs and symptoms. Purpose of this meta-analysis is to deliver global incidence and characteristics (location, size, and shape) of TCs. Methods Following PRISMA checklist, all major databases were searched by two authors for radiologic studies reporting incidence and morphologic features (location, size, and shape) of TCs. Anatomical Quality Assessment tool was applied for risk of bias evaluation. Meta-analysis of random-effects model was employed. Subgroup analysis for regional distribution, gender, sacral levels, age, correspondence with symptoms, and persistent genital arousal disorder (PGAD) were planned ahead. Results 22 radiologic studies of level 3 evidence involving 13,266 subjects were included. Global pooled prevalence of TCs was 4.18% (95% CI 2.47–6.30). Mean pooled sagittal diameter was 11.86 mm (95% CI 10.78–12.93). Sacral cysts strongly prevailed over the other segments. Of the sacral, S2 level was the most common (46.7% [95% CI 29.4–60.5]). Geographically, the highest incidence was found in Europe (6.07% [95% CI 1.49–13.00]), followed by North America (3.82% [95% CI 0.49–9.44]), and Asia (3.33% [95% CI 1.52–5.75]). TCs were more common in women than in men (5.84% vs 3.03%, p χ2). Subjects with PGAD had incidence of 37.87% (95% CI 2.45–81.75). TCs in pediatric population are rare—0.53% (95% CI 0.02–1.51). 15.59% of TCs corresponded with symptoms. Conclusions Spinal perineural (Tarlov) cysts are found in a minority of population. S2 level of the sacral bone is affected most frequently. There is female predominance. Correspondence with symptoms is seen in less than one-fifth of TCs. Studies with stronger evidence level are needed to corroborate the results. The purported high incidence in PGAD requires confirmation in case–control studies for the risk-ratio calculation.

Background: Low back pain occurs between the lumbar vertebrae and the sacral bone and is affected by factors that often occur when trying to perform a particular operation or during a collision. The purpose of this study was to investigate the effects of long-term wearing of lumbar brace on the electromyography frequency spectrum of trunk and lower limbs in low back pain older adults with pronated feet during walking. Methods: This research was of a semi-experimental type. Fifteen patients with low back pain and pronated feet were selected as an experimental group (age: 68.3 ± 2.7 years) and Fifteen patients with low back pain and pronated feet were selected as a control group (age: 69.0 ± 3.9 years).The lumbar brace used in this research was Sacro Lumbar Support, BB-OPPO 2065 model, Taiwans. The electrical activity of the lower limb and trunk muscles were recorded by the electromyography system during walking in both pre and post-test. All statistical analysis was done on SPSS software by two way ANOVA analyses test at significant level of 0.05. Results: The findings in the experimental group demonstrated that the frequency content of the gastrocnemius medialis muscle during post-test was significantly lower than that during the pre-test (P=0.002). Also, two external oblique (P=0.007) and rectus abdominus (P

Introduction: Sacral hiatus is the chief location for caudal epidural anesthesia during surgery of perineal region and also for a pain free parturition. Thus, this study was conducted to examine, measure and record the morphometry of sacral hiatus and to analyze it for any anatomical variations with clinical implications. Methods: The cross-sectional study was carried in the Department of Anatomy, Sikkim Manipal Institute of Medical Science, Gangtok, Sikkim. For the study seventy dry human sacral bone with entire sacral hiatus were measured. The shape of the sacral hiatus was observed. Level of the apex, base, length, width and anterior posterior diameter of sacral hiatus was measured with Digital Vernier Caliper. The study was approved by Institutional Ethical Committee (IEC No:SMIMS/IEC/2017-01). Data were analysed by one-way analysis of variance (ANOVA) and the difference was considered significant when P

Purpose The aim of this study was to investigate whether bone mineral density (BMD) as measured in planning computed tomographies (CTs) by a new method is a risk factor for pelvic insufficiency fractures (PIF) after radio(chemo)therapy (R(C)T) for cervical cancer. Methods 62 patients with cervical cancer who received definitive or adjuvant radio(chemo)therapy between 2013 and 2017 were reviewed. The PIF were detected on follow-up magntic resonance imaging (MRI). The MRI of the PIF patients was registered to the planning CT and the PIF contoured. On the contralateral side of the fracture, a mirrored structure of the fracture was generated (mPIF). For the whole sacral bone, three lumbar vertebrae, the first and second sacral vertebrae, and the PIF, we analyzed the BMD (mg/cm3), V50Gy, Dmean, and Dmax. Results Out of 62 patients, 6 (9.7%) had a fracture. Two out of the 6 patients had a bilateral fracture with only one of them being symptomatic. PIF patients showed a significantly lower BMD in the sacral and the lumbar vertebrae (p p Conclusion The dose does not seem to have a relevant impact on the incidence of PIF in our patients. One of the predisposing factors for developing PIF after radiotherapy seems to be the low BMD. We presented an easy method to assess the BMD in planning CTs.

Lumbosacral instrumentation continues to be challenging due to complex biomechanical force distributions and poor sacral bone quality. Various techniques have therefore been established. The aim of this study was to investigate the outcome of patients treated with S2-alar-iliac (S2AI), S2-alar (S2A), and iliac (I) instrumentation as the most caudal level. Sixty patients underwent one of the 3 techniques between January 2012 and June 2017 (S2AI 18 patients, S2A 20 patients, I 22 patients). Mean age was 70.4 ± 8.5 years. Screw loosening (SL) and sacroiliac joint (SIJ) pain were evaluated during the course at 3-month and maximum follow-up (FU). All patients completed 3-month FU, the mean FU period was 2.5 ± 1.5 years (p = 0.38), and a median of 5 segments was operated on (p = 0.26), respectively. Bone mineral density (BMD), derived opportunistically from computed tomography (CT), did not significantly differ between the groups (p = 0.66), but cages were more frequently implanted in patients of the S2A group (p = 0.04). SL of sacral or iliac screws was more common in patients of the S2A and I groups compared with the S2AI group (S2AI 16.7%, S2A 55.0%, I 27.3% of patients; p = 0.03). SIJ pain was more often improved in the S2AI group not only after 3 months but also at maximum FU (S2AI 61.1%, S2A 25.0%, I 22.7% of patients showing improvement; p = 0.02). Even in shorter or mid-length lumbar or thoracolumbar constructs, S2AI might be considered superior to S2A and I instrumentation due to showing lower incidences of caudal SL and SIJ pain.

Primary tumors of sacrum are rarely seen, and the differential diagnosis is extensive, such as chordomas, giant cell tumors, and schwannomas. Sacral intraosseous schwannomas (IOSs) are very rare and encompass approximately 1%-5% of all spinal schwannomas. Melanotic schwannomas (MSs) are categorized as an unusual variant of benign schwannomas; however, they sometimes follow a malignant course. The authors present a case of MS with intraosseous extension into sacrum in a 48-year-old male arising from the left S2 nerve root. Magnetic resonance imaging (MRI) and computed tomography (CT) scan demonstrated a destructive mass in the sacrum. He was made a diagnosis with MS by 18F-fluoro-deoxy-glucose positron-emission-tomography (18F-FDG PET) and open biopsy. The tumor was blackish-colored and vascular-rich fragile tumor covered by fibrous capsule. The floor of the tumor was not encapsulated and invading into the sacral bone. Total removal of the tumor together with the left S2 nerve of origin via posterior approach was achieved. The patient made dramatic recovery of neurological symptoms and tumor recurrence is not seen for 6-month follow-up period. MS is a benign tumor with potential for aggressive behavior and capacity to metastasize. Therefore, total removal of the tumor and careful postoperative follow-up are recommended. Postoperative spinopelvic stability also needs to be taken into consideration. The authors discuss our successful management with a focus on diagnostic process, surgical planning, and histological consideration to provide the most up-to-date guidance on managing this challenging tumor.

We report a case of a one-year-old boy with a congenital dermal sinus situated at the lateral buttock. The exact pathway of the sinus was shown by magnetic resonance imaging, contrast medium examination and computed tomographic examination. The sinus was not connected to the spinal canal and the sinus ended near the anterior surface of the sacral bone in a blind manner. Complete surgical resection of the sinus was achieved after these imaging examinations.

Myositis ossificans traumatica (MOT) is a common form of heterotopic ossification associated to trauma. Rare mature manifestations and topographically atypical presentations of MOT are often misdiagnosed as osteosarcoma. This case study discusses a rare, mature case of MOT of the piriformis muscle, potentially clinically associated with piriformis syndrome. The ossification was observed on a dry sacral bone of an adult skeleton belonging to a South African male during routine inventory of the Raymond A. Dart Collection of Human Skeletons, the University of the Witwatersrand, Johannesburg. The MOT was located on the anterior aspect of the sacrum at a site corresponding to the upper portion of the origin of the muscle and extended laterally towards the greater trochanter, beyond the greater sciatic notch. It was cylindrical in shape and measured approximately 52.70 mm in length and 12.10 mm in diameter. Micro-focus CT revealed an extensive and mature bony development of the piriformis muscle with distinct outer cortical and inner trabecular bone. In addition, the skeleton showed widespread healed skeletal trauma, suggesting a history of trauma. The MOT was completely fused to the sacral bone excluding the possibility of congenital anomalies. Information on the MOT of the piriformis muscle is vital to clinicians and radiographers to aid in successful diagnosis and management of the piriformis syndrome and sciatica in the gluteal region. This case also provides a rare example to biological anthropologists, paleoanthropologists and bioarchaeologists of the representation of pathologies like these on a dry bone sample.

Dural metastases are uncommon in cancer patients, but can have as much of an effect on the lives of patients as brain metastases. Dural metastases are most commonly associated with primary cancers of the breast, prostate, and lung, and it is rare that the primary site of the tumor is unknown. In this study, we encountered a 51-year-old woman who had developed multiple bone tumors, with no known primary cancer lesion. A tumor biopsy of the sacral bone revealed non-keratinizing squamous cell carcinoma; the patient was therefore diagnosed as having multiple bone metastases of an unknown primary cancer. Magnetic resonance imaging revealed cranial metastases and partial thickening of the dura with suspected dura metastases. Platinum-based chemotherapy reduced the bone metastases and the thickened dura. However, as resistance to chemotherapy developed, invasions progressed rapidly and diffusely throughout the dura. This was accompanied by the development of dysarthria, visual impairments, and delirium. The patient died 10 months after being diagnosed with dural metastases. This report provides information on the clinical course and prognosis of patients with dural metastases of unknown primary cancer. Furthermore, it may help to construct a treatment strategy for dural metastases.

Objective: to study the changes of the biomechanical system «bone – fixator – endoprosthesis» under the loading for internal hemipelvectomy I–III type Enneking with reconstruction of the pelvic ring defect by a metalcement spacer with and without reinforcement with a metal bar.Methods: spatial geometry of the pelvis is reconstructed with the software package «Mimics». Data are obtained by calculating Mises values.Results: the stresses on the screws in the model were not significantly (0.27 %) larger (σmах 132.6 MPa vs. 132.3 MPa in the model without reinforcement) and did not exceed the strength limit. The maximum value of stress on polymethylmethacrylate in both models is localized in the place of contact with the pubic symphysis and is not significantly (0.4 %) higher in the model with the bar (σmах — 24.7 and 24.6 MPa, respectively). The maximum values of stress on the sacral bone in both models are defined in the zone of proximal screw installation in the lateral mass of the sacral bone, but 5 % larger in the construction without a bar — 10.6 and 10.1 MPa. The maximum permissible loads were: on the sacral bone in a model with a bar of 1.06 body weight, without a bar — 1.01; for polymethylmethacrylate — 3.05 and 3.03 body weight respectively; for metal screws — 3.44 and 3.43 body weight, respectively.Conclusions: the usage of a metal bar in the system «bone – fixator – endoprosthesis» for internal hemipellectomy type I–III does not change the mechanical strength and stability of the model. The most susceptible to destruction was the lateral area of the sacrum in the place of the proximal screw, which should be strengthened by inserting an additional screw into the upper part of the sacroiliac joint. In the dynamics (walking, running, climbing stairs), the load of the surgery site can be 4 times higher the weight of the body, which due to the linear growth of stress values can lead to the destruction of the structure and requires the usage of additional means of support (crutches, a stick, etc.).

Mucoepidermoid carcinomas (MECs) are generally found in salivary gland, but they have also been mentioned in other organs such as the larynx, esophagus, breast. MECs are considered to be a low-grade carcinoma and their occurrence in the thyroid is extremely rare. We present a 54-year-old male patient admitted to our clinic, complaining about having back pains for approximately three months. A lumbosacral spine MRI and a PET/CT scan revealed multiple lesions in the L4, L5, S1 vertebra bodies, sacral bone and left pelvis bone, suggesting of a metastatic disease. The result of thyroid FNA was carcinoma and a biopsy of the vertebra bone confirmed the presence of a metastatic carcinoma. A total thyroidectomy and level VI neck dissection was conducted followed by palliative external beam radiotherapy (30 Gy) to the vertebra bodies, sacral bone and left pelvis bone. In pathological studies, the diagnosis of thyroid mucoepidermoid carcinoma was confirmed. Six months after treatment, the patient died due to severe pain and fatigue caused by the disease. Here, we report a rare case with bone metastasis as the first symptom of MEC and a brief review of published literature on the subject.

Primary lymphoma of the sacral bone is a rare myeloproliferative disease, occurring primarily after the 4th decade of life and mainly in male patients. We reported a case of sacral bone lymphoma in a 24-year-old man with low back pain and radiculopathy. Imaging showed a sacral bone lesion which later proved to be non-Hodgkin’s lymphoma on the histopathologic study. Lymphoma of the sacral bone is chemoresponsive and carries a good prognosis. Sacral bone lymphoma should be considered a differential diagnosis in patients with low back pain who do not respond to analgesic treatment.

The sacrum is a triangular shaped bone made up of five fused vertebral bodies. It is composed of bone, cartilage, marrow elements as well as notochord remnants and is a common site for both benign and malignant (primary and secondary) tumors. Familiarity with the imaging features and clinical presentations of sacral bone tumors could be helpful in narrowing the differential diagnosis. Magnetic resonance imaging and computed tomography are the preferred imaging modalities for evaluating sacral masses. This pictorial review will highlight imaging features of common sacral tumors with pathologic correlation. Additionally, this article will review some critical principles and helpful tips to successfully biopsy these lesions.

To retrospectively report on safety, pain relief and local tumor control achieved with percutaneous ablation of sacral bone metastases.From February 2009 to June 2020, 23 consecutive patients (12 women and 11 men; mean age, 60±8 [SD] years; median, 60; range: 48-80 years) with 23 sacral metastases underwent radiofrequency (RFA) or cryo-ablation (CA), with palliative or curative intent at our institution. Patients' demographics and data pertaining to treated metastases, procedure-related variables, safety, and clinical evolution following ablation were collected and analyzed. Pain was assessed with numerical pain rating scale (NPRS).Sixteen (70%) patients were treated with palliative and 7 (30%) with curative intent. Mean tumor diameter was 38±19 (SD) mm (median, 36; range: 11-76). External radiation therapy had been performed on five metastases (5/23; 22%) prior to ablation. RFA was used in 9 (39%) metastases and CA in the remaining 14 (61%). Thermo-protective measures and adjuvant bone consolidation were used whilst treating 20 (87%) and 8 (35%) metastases, respectively. Five (22%) minor complications were recorded. At mean 31±21 (SD) (median, 32; range: 2-70) months follow-up mean NPRS was 2±2 (SD) (median, 1; range: 0-6) vs. 5±1 (median, 5; range: 4-8; P0.001) at the baseline. Three metastases out of 7 (43%) undergoing curative ablation showed local progression at mean 4±4 (SD) (median, 2; range: 1-8) months follow-up.Percutaneous ablation of sacral metastases is safe and results in significant long-lasting pain relief. Local tumor control seems sub-optimal; however, further investigations are needed to confirm these findings due to paucity of data.

A detailed knowledge on the exact morphology of pelvic injuries provided crucial information in understanding the mechanisms of injury and has influence on the natural course and subsequent mortality. However, forensic medical literature investigating pelvic fractures in detail is scarce to date. This case series aims to compare the accuracy in detecting pelvic injuries using autopsy and ante mortem computed tomography (CT). Nineteen deceased patients with CT scans of pelvic fractures were included retrospectively. Pelvic injuries were independently assessed by a board-certified radiologist (R) and a board-certified trauma surgeon (T), both using the ante mortem CT scans, and by a board-certified forensic pathologist using autopsy (A) results without knowledge of the CT scan findings. No patient had died causatively from a pelvic fracture. Most injuries of the pelvis were present in the pubic rami (16/18) and sacral bone (13/18), followed by the sacroiliac joint (9/18) and iliac bone fractures (8/18). Ilium fractures (A:100%;R:67%;T:67%) and injuries of the sacroiliac joint (A:83%;R:50%;T:42%) were best detected via autopsy. The diagnosis of sacral fractures (A:19%;R:94%;T:88%) and fractures of the pubic rami (A:67%;R:96%;T:96%) were most often missed in autopsy. The results show deficits in the assessment of the pelvic injury for both CT and autopsy. Autopsy was superior in detecting injuries of the sacroiliac joint, but inferior in detecting sacral and pubic bone fractures. For an encompassing evaluation of ligamento-skeletal pelvic injuries, the complementary use of both CT and autopsy is recommended.

Abstract:: The diagnosis of sacral neoplasms is often delayed because they tend to remain clinically silent for a long time. Imaging is useful at all stages of the management of sacral bone tumors, i.e., from the detection of the neoplasm to the long-term follow-up. Radiographs are recommended as the modality of choice to begin the imaging workup of a patient with known or suspected sacral pathology. More sensitive examinations, such as Computerized Tomography (CT), magnetic resonance (MRI), or scintigraphy, are often necessary. The morphological features of the lesions on CT and MRI help orientate the diagnosis. Although some imaging characteristics are helpful to limit the differential diagnosis, an imaging-guided biopsy is often ultimately required to establish a specific diagnosis. Imaging is of paramount importance even in the long-term follow-up, in order to assess any residual tumor when surgical resection remains incomplete, to assess the efficacy of adjuvant chemotherapy and radiotherapy, and to detect recurrence.

Extramedullary hematopoiesis (EMH) represents the production of blood cells outside of the bone marrow and occurs in beta thalassemia major. Although EMH usually occurs in the liver, spleen, and lymph nodes, it may also occur in the spinal canal or sacral bone lead to neurological complications

Fragility fracture of the sacrum has been an issue for elderly people. Research has been limited for the sacrum partly because its shape is complex with large inter-subject variation. Also, large-scale statistical analysis of its shape and density distribution has been limited mainly due to the computational load in establishment of the voxel correspondences, i.e., deformable registration.In this study, we employed a convolutional neural network (CNN)-based deformable registration algorithm in the analysis of the sacral bone. The algorithm we employed, VoxelMorph (Dalca et al. Med Image Anal 2019), is characterized as an unsupervised algorithm where no ground truth deformation field is required. The algorithm also allows to create a conditional deformable template, which is a volume image exhibiting smallest deformation field from all samples with specific attributes (e.g., age, sex, etc.), which in short represents the “average” (or “centroid”) image among the specific age and sex group. We applied it on a database consisting of 837 CTs (149 males, 688 females, 58.14 ± 14.73 y.o.) of the pelvis region, where the sacral bone was segmented and masked. We computed the templates corresponding to ages of 20 to 80 for male and female. The templates visually illustrated reduction of the bone density with aging in both male and female. The quantitative analysis showed that the average CT value over the sacrum region was reduced from 135.73 HU to 39.88 HU for 20 y.o. template to 80 y.o. template.

Background Currently, few studies have described the relationship between functional MRI findings and histology of normal sacroiliac joint (SIJ). Besides, due to the difficulties in access to SIJ, authentic animal models are important in providing opportunities for quantitative parameter extraction on imaging. Aims This study aimed at exploring the parameters of Intravoxel Incoherent Motion Diffusion-Weighted Imaging (IVIM-DWI) and Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) and comparing them with the histology of the SIJ in normal rats with different ages. Methods A total of thirty 7-week-old male Wistar rats were included in the study. The parameters of IVIM-DWI and DCE-MRI in the bone marrow and the joint space of SIJ were measured at 8, 13, 18, 23, 28, and 33 weeks. The histological analysis of the SIJ was examined using light microscopy. One-way ANOVA was used for statistical analysis. Results The D values in the sacral and iliac bone marrow of normal rats decreased with an increase in age. One-way ANOVA analysis indicated a significant difference in D values in different age groups (P Conclusions This study obtained the IVIM-DWI and DCE-MRI parameters of the sacral and iliac bone marrow and the synovial area of the joint space in normal rats. The parameters in normal rats can be used in future research to compare to similar parameters in animal models or patients with SIJ diseases. This study serves as a guide for future research in SIJ diseases.

Purpose To evaluate the diagnostic accuracy of color-coded dual-energy CT virtual noncalcium (VNCa) reconstructions for the assessment of traumatic bone marrow edema in sacral insufficiency fracture (SIF). Method Data from 52 consecutive patients (28 women, 24 men; mean age, 61 ± 13 years; range, 49−94 years) who had undergone third-generation dual-source CT and 3-Tesla (T) MRI due to low back pain without adequate trauma were retrospectively evaluated. Five radiologists, blinded to MRI and clinical information, independently analyzed conventional grayscale dual-energy CT series for sacral fractures according to the Denis classification. Eight weeks later, readers re-assessed all scans using color-coded VNCa reconstructions for sacral bone marrow edema. CT numbers on VNCa reconstructions were measured by a sixth radiologist. One experienced radiologist (33 years of experience in musculoskeletal [MSK] imaging), blinded to CT and clinical information, defined the reference standard by analyzing the MRI scans. The primary indices for diagnostic accuracy were sensitivity, specificity, and the area under the curve (AUC). Results MRI revealed a total of 39 zones with SIF-associated bone marrow edema in 27 patients. In the qualitative analysis, VNCa showed high overall sensitivity (93 %) and specificity (95 %) for assessing SIF-associated bone marrow edema. The quantitative analysis of color-coded VNCa reconstructions revealed an overall AUC of 0.976. A cut-off value of –43 Hounsfield units provided a sensitivity of 85 % and a specificity of 95 % for differentiating bone marrow edema. Conclusions Color-coded dual-energy CT VNCa reconstructions yield excellent diagnostic accuracy in the analysis of SIF-associated bone marrow edema compared to MRI.

Introduction: Sacral chordomas are rare, low-grade and slow growing malignant bone tumours arising from the sacral bone. They are locally aggressive with the tendency to metastasize to the lungs. Surgical resection remains the mainstay of treatment of sacral chordomas. However, most patients presented late with large tumours and intra-abdominal extension making en bloc resection highly challenging. Besides that, surgical resection poses risk of injury to the surrounding structures such as major blood vessels, bladder, ureters and rectum due to their proximity to the tumour. Therefore, multidisciplinary team approach is vital in ancipitating possible complications and preventing surgical morbidity. We present a case of advanced sacral chordoma which has been successfully resected with the assistance of pre-operative selective arterial embolization as a pre-emptive therapy. Case report: A 58-year-old lady presented with a large sacral chordoma (17.17 cm x 27.3 cm x 30.5 cm) with sacral erosion, infiltration to gluteus maximus, medius and minimus muscles and lung metastasis. A decision to perform a surgical resection was made to alleviate the pain secondary to sacral nerve compression. Anticipating massive bleeding intra-operatively, pre-operative arterial embolization was performed involving one branch of right internal iliac artery as well as five branches of left internal and external iliac arteries using endovascular coils. The tumour was resected with partial sacrectomy from S2 and below. Intra-operatively, 6 pints of packed cells were transfused with estimated blood loss of 4 litres. The patient recovered well after the surgery. She was pain-free post-operatively with no lower limb neurological deficit. Conclusion: Surgical resection remains the treatment of choice for sacral chordoma. Pre-operative selective arterial embolization can reduce intra-operative bleeding and avoid a potentially convoluted surgery.

Background Individuals' interest in sports activities has been increasing, contributing to more stress fracture occurrences in uncommon locations on the skeleton. In this study, several cases of stress fractures in atypical locations are presented, and the possibility of combining diagnostic methods to make accurate and quick diagnoses is explored. Additionally, different causes of stress fractures, as well as various modalities of treatment, are highlighted. Other potential factors of stress fractures were identified by a literature review. Case summary Six cases of stress fractures in the calcaneus, intermediate cuneiform bone, sacrum, tibia (bilateral), navicular bone and femoral neck are presented, with different types of diagnostic imaging and treatments. All of the cases were associated with an aspect of mobility because all of the patients were physically active in various sport disciplines. Conclusion The type of therapeutic procedure selected should depend on the specific clinical case, i.e., the patient's condition and level of physical activity.

Context: Spine duplication is a rare condition, with various extents and severe additional anomalies. The goal of this study was to describe a unique case of a boy with split notochord syndrome who was followed up from birth until maturity. Findings: Physical examination at birth showed defects of the abdominal wall and cloacal exstrophy with visible urether outlets. A transposed anus was present in the perineal region. Split bony elements of the spine with nonpalpable sacral bone were noted. A soft, skin-covered lump, with the consistency of a lipoma, was present in the sacral area. There was asymmetry of the lower limbs: the left was hypoplastic, with a deformed foot and hip. Computed tomography revealed a normal shape of the Th12 and L1 vertebrae, whereas the L2 was split. Downward from L3, there were two vertebrae at each level, with two spinal canals. The spinal cord divided into two “semicords” at the level of L1. Neurologic status and the shape of the spine remained unchanged during puberty. The last follow-up was performed at the age of 18 years. He managed to walk independently in prosthesis with visible limping. Conclusion: Spine deformities are always suspected in neonates with lipoma in the sacral region, which may sometimes be serious. Walking ability and quality of life depend on neurologic deficits; even with long duplication and double sacrum, walking can be a feasible option.

Objective To evaluate the feasibility and safety of an individualized and reassemblable three-dimensional (3D) printing navigation template for making accurate punctures during sacral neuromodulation (SNM). Methods From July 2016 to July 2017, 24 patients undergoing SNM were enrolled. Conventional X-ray guidance was used in the control group, which included 14 patients, while the 3D printing template was used in the experimental group, which included 10 patients. The number of punctures, the average puncture time, the exposure to X-ray, the adjustment time during the operation and the testing of the SNM device, the infection and haemorrhage rate, and the implantable pulse generator (IPG) implantation rates were compared between the two groups. Results In total, 24 patients successfully underwent stage I. When comparing the control group and the experimental group, the number of punctures were 9.6 ± 7.7 and 1.5 ± 0.7, respectively; the average puncture times were 35.4 ± 14.6 and 4.1 ± 2.2 min, respectively; and the X-ray exposure levels were 8.37 ± 4.83 mAs and 2.34 ± 0.54 mAs, respectively. No postoperative complications were reported in either group. The IPG implantation rates were not different between the two groups. Conclusion The 3D printing template for SNM can help us to perform accurate and quick punctures into the target sacral foramina, reduce X-ray exposure, and shorten the operation time. For patients with obesity, sacral variation, sacral bone fractures or losses and for patients who are unable to tolerate the prone position during operation, use of the 3D printing template is recommended.

Rationale and Objectives This study aimed to determine the diagnostic utility of standardized uptake values (SUV) and apparent diffusion coefficients (ADC) for assessment of focal and diffuse bone marrow involvement in patients with malignant lymphoma. Materials and Methods Sixty treatment-naive patients (28 males; mean age 51.2 ± 16.7 years) with histologically proven lymphoma, who underwent fludeoxyglucose (18F) positron emission tomography-computed tomography ([F18]-FDG-PET/CT) and whole-body diffusion-weighted imaging (WB-DWI) within 7 days, and also routine bone marrow biopsy, were included in this institutional review board-approved, retrospective study. The maximum SUV (SUVmax) on [F18]-FDG-PET/CT, and the mean ADC (ADCmean, ×10−3 mm2/s) on whole-body-DWI, were extracted from focal lesions, or, in their absence, from the thoracic (Th8) and lumbar vertebral bodies (L4), the sacral bone (S1), and the iliac crest. Lesion-to-liver-ratios (SUVmax-ratio) were calculated. Pearson correlation coefficients were used to assess the correlation between SUVmax-ratios and ADCmean values. Results Bone marrow involvement was observed in 16 of 60 patients (8 of 16 with diffuse infiltration). The SUVmax-ratio cutoff value was 95.25% for focal and 70.2% for diffuse bone marrow involvement (sensitivity/specificity of 87.5%/86.4% and 100%/43.2%, respectively). The ADCmean cutoff value was 0.498 for focal and 0.401 for diffuse bone marrow involvement (sensitivity/specificity of 100%/90.9% and 87.5%/56.8%, respectively). No significant correlations were found between SUVmax-ratios and ADCmean values in the different groups. Conclusion With the liver as reference tissue, quantitative [F18]-FDG-PET/CT may be useful to differentiate bone marrow involvement from normal bone marrow in patients with lymphoma, even though the specificity for diffuse marrow involvement is rather low. Quantitative DWI can be used only to distinguish focal bone marrow lesions from normal bone marrow.

An 88-year-old male patient of high surgical risk was presented with left sciatic pain symptoms and a palpable pulsatile left lower abdominal mass. He was operated 8 years ago for a large infrarenal aortic aneurysm. Computed tomography angiography (CTA) revealed a giant 161 mm left internal iliac aneurysm with multilocular appearance and left sacral bone erosion causing the symptoms. Endovascular repair was successfully performed using a monotubular iliac stent-graft. Follow-up CTA showed absence of contrast enhancement and a fully thrombosed sac. Patient recovered completely and was discharged 1 month after the procedure in a relatively good condition, nevertheless sciatic symptoms remained.

To investigate the incidence rate, time-to-onset and recovery, MRI morphology and occurrence of insufficiency fractures in radiation-induced changes in the sacrum following pelvic radiotherapy. 410 patients with pelvic malignancies treated with radiotherapy were reviewed. Follow-up was 1–124 months (mean 22 months). Serial MRI (average four studies/patient) were analysed using a new semi-quantitative score (Radiation-Induced Sacral Changes=RISC). A size category (I/II/III), a type category for MR signal morphologies (a/b/c) and sacral insufficiency fractures (+/-) were applied. Seventy-two patients (17.6 %) were found to have new pathological signal changes. Radiation osteitis was documented in 83.3 % (60/72, RISC stage a + b), and definite osteonecrosis (stage c) in 12 patients (16.7 %, 12/72). Thirty-one patients (43.1 %) had sacral insufficiency fractures. Initial bone marrow signal changes were found 1–35 months (median 4 months) after radiotherapy. The maximum manifestation of radiation-induced signal changes occurred after 1–35 months (mean 11 months). Fifty-six cases (77.8 %) showed a significant signal recovery within 16.5 months. Radiation-induced bone marrow changes appear with a high incidence at the sacrum with an early onset and frequent recovery. The majority presented a pattern of radiation osteitis, whereas osteoradionecrosis was proportionately rare. • Radiation-induced sacral bone marrow changes appear frequently (17.6 %) following pelvic radiotherapy. • Insufficiency fractures are common late effects (43 %). • Radiation osteitis develops early (4 mo), with recovery between 16.5 and 39.5 months. • Definite radiological osteoradionecrosis is proportionately rare (3 %). • A 3-stage classification system simplifies and standardizes the morphological disease staging.

Introduction Previous reports indicated the effectiveness of surgical resection for locally recurrent rectal cancer (LRRC). Most cases with posterior invasion patterns require concomitant sacrectomy to secure negative histologic margins, although this is a highly invasive procedure. Here, we present a new minimally invasive laparoscopic surgical technique for LRRC with concomitant sacrectomy. Materials and surgical technique A 64-year-old man presented with LRRC on the surface of the sacral bone. He underwent laparoscopic abdominoperineal resection with concomitant sacrectomy below the S4 vertebra. The surgical procedure, including sacrectomy, was performed laparoscopically. The distance between the estimated resection line (below the S4 vertebra) and sacral promontory was measured by preoperative imaging. Intraoperatively, a flexible ruler was employed to determine the resection line. Securing adequate space dorsal to the sacral bone was indispensable for placement of the Gigli wire saw. After the Gigli wire saw was positioned, bilateral caudal trocars were used to remove the ends of the wire. Then, the sacral bone was cut by the linear reciprocating motion of the Gigli wire saw. Pathologically confirmed curative resection was achieved. The procedure was successfully performed without transfusion or intraoperative complications. The operation time was 757 min, and blood loss volume was 890 ml. There were no severe postoperative complications. The patient is alive and well with no evidence of recurrence at 58 months after surgical resection of LRRC. Discussion Our newly developed technique demonstrates that laparoscopic intraperitoneal sacrectomy using a Gigli wire saw is a safe and useful procedure to facilitate resection of LRRC.

Purpose Sacral neuromodulation (SNM) therapy is indicated for some refractory urological conditions. The electrode lead position in sacral x-rays during routine follow-up may predict the outcome of SNM therapy. To determine whether the radiographic position of the electrode in the sacral foramen predicted the long-term outcome of SNM therapy. Methods This was a retrospective study of patients who underwent InterStim SNM at Toronto Western Hospital by 2 surgeons from July 2013 to March 2014. The position of electrodes in relation to the sacral bone was assessed on follow-up sacral x-rays. In the lateral view, we determined the location of the radio-opaque marker of the electrode relative to the inner surface of the sacrum (P3, D3, P2, D2, P1, D1, P0, and D0). In the anteroposterior view, the angle between a line through the spinous process shadow and the electrode was measured (0°-30°, 30°-60°, 60°-90°, >90°, or medial). Dissatisfied patients were defined as those who did not improve based on a voiding diary or those who needed salvage treatment after SNM. The primary endpoint was to determine whether the electrode lead position on sacral x-rays predicted the outcome of SNM therapy. Results A total of 69 patients (61 female and 8 male patients) were included, with a median age of 55 years. Forty-two of the patients (60.9%) had refractory overactive bladder, 21 (30.4%) suffered from chronic urinary retention, and 6 (8.7%) had lower urinary tract symptoms and chronic pelvic pain syndrome. The univariate analysis did not show any correlation between SNM response and the electrode position or angle. Dummy regression analysis using response to implantation as the dependent outcome variable did not show any significance for any of the predictors. Conclusions Our study did not show a correlation between the long-term response to SNM and the electrode position on follow-up sacral x-rays. In this study, electrode lead position in sacral x-ray at follow-up was not correlated with the outcome of SNM therapy.

Objective: to study in healthy volunteers radiometric parameters of sacrum and pelvis, affecting the spinal-pelvic balance in the frontal plane and their relationship to each other. Methods: we examined 36 healthy student volunteers (25 males and 11 females aged 17 to 23 years). The average height was 173 cm (from 168 to 183), average body mass index — 22.23 (from 17.90 to 29.38). Standing X-ray examination performed in all the volunteers. X-rays were measured: 1) the angle of the cra­nial sacral bone plate by the method of R. E. Irvin in frontal plane; 2) the angle of the pelvic tilt; 3) the angle of rotation around the sacrum axis by method of A. Orel; 4) width of sac­roiliac joint in the ventral, dorsal and medial portions. Results were assessed using statistical methods. Results: the majority of volunteers (81 %) had asymmetric joint space width of sacro­iliac joint, which accompanied pelvic and sacral tilt and sacral bone rotation. The sacral slope measured in 95 % of patients, pelvis — 83 %, sacral rotation in 92 %. The width of the joint space of volunteers was (3.3 ± 0.9) mm. Using cluster analysis all volunteers were divided into four clusters (groups), charac­terized by certain parameters. In the first group examined joint space width was symmetrical in all portions, pelvic tilt and sacral slope were the same, the rotation of sacrum decreased. Joint asymmetry found in two groups of volunteers in the third and fourth groups (39 %, 14 persons) and three parts — other (42 %, 15 people). Found that 20 volunteers (56 %) had joint space asymmetry, pelvic tilt and sacral slope, sacral rotatio 3°, the maximum deviation (more than 3°) these indicators are re­corded in 7 volunteers (19 %).

Objective To establish a three-dimensional (3D) finite element (FE) model of ankylosing spondylitis (AS) kyphosis that is a digital platform for further studies. Methods A 30-year-old man with AS kyphosis underwent computed tomography transverse scanning from T1 to the sacrococcyx. The images were imported into Mimics® 17.0 software to establish a 3D model of the posterior spine, which was then imported into Studio Geomagic 2013 software. Posterior spine convex geometry was established on the 3D geometric model for subsequent optimization of image processing. Unigraphics NX 8.5 produced the spinal kyphosis surface model. Modeled calcification of ligaments and partial resection of useless sacral bone were added. The model was imported into ANSYS 15.0 FE analysis software. Ligaments were added. Parameters were set to generate a 3D FE model of AS. Results and Conclusion A 3D FE model of AS was successfully established, providing a reliable digital platform for subsequent biomechanical analysis.

Study Objective To demonstrate the robot-assisted laparoscopic decompression approach to treat aberrant vessels entrapping the sacral nerves causing motor deficit. Design Video presentation of two cases. Setting Tertiary unit specializing in advanced gynecologic surgery and neuropelveology. Patients or Participants Case 1: A 23-year-old virgin female patient presented with right lower extremity weakness, which had progressed into a limp over the past year and dysmenorrhea with a VAS (visual analog scale) score of 10. Gynecological examination revealed a 2 cm endometrioma on the right ovary. Under neurological examination hypoesthesia on right peroneal and right tibial nerve-dermatomes and chronic denervation of the muscles innervated by L5-S1 were observed. Case 2: A 46-year-old gravidity 3 parity 3 female patient presented with non-menstrual left sciatic pain, which caused difficulties while wearing socks and high heels and climbing up stairs. Magnetic resonance imaging (MRI) revealed dilated vessels on the left sacral nerve roots. Interventions Robot-assisted laparoscopic sacral nerve decompression Measurements and Main Results Patients were evaluated at 3rd and 6th month postoperatively. First patient's electromyography (EMG) result was normal at the 3rd month control. Motor deficit of both patients were eliminated and they both recovered fully. Conclusion Motor deficit or pain radiating (i.e. sciatica) to lower extremities are usually caused by spinal cord problems. However, these symptoms could arise by anatomic structures obstructing the nerves travelling to target organs or by nerve injuries. Since lumbosacral plexus is located over the sacral bone, it can be compressed easily by abnormal vessels crossing over the plexus. Accessing to the sacral plexus between lateral iliac vessels and iliopsoas muscle is crucial and stable instruments are crucial during surgery. Robotic-assisted laparoscopy allows this stability and decrease the possibility of complications. The robotic technique offers, three-dimensional vision, improved maneuverability and enhanced ergonomics in the deepest parts of the pelvis.

A pressure sore is an ulceration caused by excessive pressure being applied to a tissue over an excessive duration. These ulcers are also called decubitus ulcers, bed sores, or pressure ulcers; these names implying that they are caused by lying down too long. Elderly people represent the single largest group likely to suffer from pressure sores. With medical care gradually improving around the world, life expectancies are increasing, which leaves a larger segment of the population susceptible to pressure sores. The skin over the sacral bone is almost without muscle padding. This factor, in combination with the sacral bone having an extremely pointed shape, like that of a spur, causes pressure sores to develop there most often when an individual is positioned in the supine position. Skin, muscle, fat, and eventually bone are all susceptible to developing a pressure sore when they are excessively mechanically deformed over a period of time.

BACKGROUND Anatomic and surgical complexity make pelvic and sacral bone sarcoma resections challenging. Positive surgical margins are more likely to occur in patients with pelvic and sacral bone sarcomas than in those with extremity sarcomas and are associated with an increased likelihood of local recurrence. Intraoperative navigation techniques have been proposed to improve surgical accuracy in achieving negative margins, but available evidence is limited to experimental (laboratory) studies and small patient series. Only one small historically controlled study is available. Because we have experience with both approaches, we wanted to assess whether navigation improves our ability to achieve negative resection margins. QUESTIONS/PURPOSES Are navigated resections for pelvic and sacral primary bone sarcomas better able to achieve adequate surgical margins than nonnavigated resections? METHODS Thirty-six patients with pelvic or sacral sarcomas treated with intraoperative navigation were retrospectively compared with 34 patients undergoing resections without navigation. All patients underwent resections between 2000 and 2017 with the intention to achieve a wide margin. Patients in the navigation group underwent surgery between 2008 and 2017; during this period, all resections of pelvic and sacral primary bone sarcomas with the intention to achieve a wide margin were navigation-assisted by either CT fluoroscopy or intraoperative CT. Patients in the control group underwent surgery before 2008 (when navigation was unavailable at our institution), to avoid selection bias. We did not attempt to match patients to controls. Nonnavigated resections were performed by two senior orthopaedic surgeons (with 10 years and > 25 years of experience). Navigated resections were performed by a senior orthopaedic surgeon with much experience in surgical navigation. The primary outcome was the bone and soft-tissue surgical margin achieved, classified by a modified Enneking system. Wide margins (≥ 2 mm) and wide-contaminated margins, in which the tumor or its pseudocapsule was exposed intraoperatively but further tissue was removed to achieve wide margins, were considered adequate; marginal (0-2 mm) and intralesional margins were considered inadequate. RESULTS Adequate bone margins were achieved in more patients in the navigated group than in the nonnavigation group (29 of 36 patients [81%] versus 17 of 34 [50%]; odds ratio, 4.14 [95% CI, 1.43-12.01]; p = 0.007). With the numbers available, we found no difference in our ability to achieve adequate soft-tissue margins between the navigation and nonnavigation group (18 of 36 patients [50%] versus 18 of 34 [54%]; odds ratio, 0.89 [95% CI, 0.35-2.27]; p = 0.995). CONCLUSIONS Intraoperative guidance techniques improved our ability to achieve negative bony margins when performing surgical resections in patients with pelvic and sacral primary bone sarcomas. Achieving adequate soft-tissue margins remains a challenge, and these margins do not appear to be influenced by navigation. Larger studies are needed to confirm our results, and longer followup of these patients is needed to determine if the use of navigation will improve survival or the risk of local recurrence. LEVEL OF EVIDENCE Level III, therapeutic study.

Aims The aim of this study was to investigate the local recurrence rate at an extended follow-up in patients following navigated resection of primary pelvic and sacral tumours. Patients and Methods This prospective cohort study comprised 23 consecutive patients (nine female, 14 male) who underwent resection of a primary pelvic or sacral tumour, using computer navigation, between 2010 and 2012. The mean age of the patients at the time of presentation was 51 years (10 to 77). The rates of local recurrence and mortality were calculated using the Kaplan–Meier method. Results Bone resection margins were all clear and there were no bony recurrences. At a mean follow-up for all patients of 59 months (12 to 93), eight patients (34.8%) developed soft-tissue local recurrence, with a cumulative rate of local recurrence at six-years of 35.1% (95% confidence interval (CI) 19.3 to 58.1). The cumulative all-cause rate of mortality at six-years was 26.1% (95% CI 12.7 to 49.1). Conclusion Despite the positive early experience with navigated-assisted resection, local recurrence rates remain high. With increasing knowledge of the size of soft-tissue margins required to reduce local recurrence and the close proximity of native structures in the pelvis, we advise against compromising resection to preserve function, and encourage surgeons to reduce local recurrence by prioritizing wide resection margins of the tumour. Cite this article: Bone Joint J 2019;101-B:484–490.

Background The study aimed to compare sex differences in the morphology and spatial orientation of pelvic acetabula to advance the understanding of hip anatomy. Material and methods The study was based on three-dimensional reconstructions of computed tomography images of 50 female and 50 male acetabula. The images were used for spatial analysis of hip acetabula relative to the base of the sacral bone as the plane of reference. Statistical analysis was performed to compare angles relevant to the actual axis of the acetabulum (inclination angle, anteversion angle, tilt angle) as well as the volume and inner surface area of the acetabulum. Results Both the inclination and tilt angles of the acetabulum did not differ significantly between the groups, the respective values being: 68.61° and 26.53° in females and 70.56° and 30.19° in males (p>0.05). The anteversion angle was significantly larger for female acetabula (38.27° compared to 32.05° in men, with p=0.0008), while the volume and the inner surface area were significantly smaller in women (p=0.0007 and 0.0001 respectively). Conclusions 1. Acetabular orientation is sex-specific, with female acetabula being more forward-oriented than those of men. 2. The volume and inner surface area of acetabula also differ between the sexes, being smaller in women. 3. Regardless of the plane of reference, sexual dimorphism of the acetabulum is constant. 4. Awareness of the above sex-dependent differences is necessary for preoperative planning before orthopaedic surgeries (such as hip arthroplasty or operative treatment of FAI).