A practical guide for planning pelvic bone percutaneous interventions (biopsy, tumour ablation and cementoplasty)
Percutaneous approaches for pelvic bone procedures (bone biopsies, tumour ablation and cementoplasty) are multiple and less well systematised than for the spine or extremities. Among the different imaging techniques that can be used for guidance, computed tomography (CT) scan is the modality of choice because of the complex pelvic anatomy. In specific cases, such as cementoplasty where real-time evaluation is a determinant, a combination of CT and fluoroscopy is highly recommended. The objective of this article is to propose a systematic approach for image-guided pelvic bone procedures, as well as to provide some technical tips. We illustrate the article with multiple examples, and diagrams of the approaches and important structures to avoid to perform these procedures safely.
• Pelvic bone procedures are safe to perform if anatomical landmarks are recognised.
• The safest approach varies depending on the pelvic level.
• CT is the modality of choice for guiding pelvic percutaneous procedures.
• Fluoroscopy is recommended when real-time monitoring is mandatory.
• MRI can also be used for guiding pelvic percutaneous procedures.
KeywordsInterventional musculoskeletal radiology Pelvic bone Biopsy Cementoplasty Tumour ablation
Percutaneous approaches for the spine  or extremities  have been well described in the literature. On the other hand, approaches to the pelvic bone are more complex and poorly systematised. There are several percutaneous procedures aimed at pelvic bone: biopsies of primary bone tumours and metastases [3, 4], percutaneous tumour ablation [5, 6, 7], cementoplasty [8, 9, 10, 11, 12, 13] and percutaneous screw fixation [14, 15]. All these techniques can be used alone or in combination  using the same approaches. The objective of this article is to propose a systematic approach to perform image-guided pelvic bone procedures in the safest way and discuss their technical aspects.
The bony pelvis is a ring formed by the sacrum and the innominate bones joined by the pubic symphysis and the sacroiliac joints. It contains several visceral structures of the genitourinary and lower digestive systems and many vessels and nerves transiting between the pelvis and the lower limbs. Different modalities can be used for guiding pelvic bone percutaneous interventions.
Computed tomography (CT) scanner
CT has been found to provide the most convenient and safest guidance modality . Gantry angulation can be used to facilitate needle placement. Unless using the highly radiating CT fluoroscopy, its main drawback is the absence of real time imaging and control in the Z-axis, which are important in some procedures, such as cementoplasty. This disadvantage can be solved by combining the CT scanner with a C-arm fluoroscopy [10, 12, 18]. In this setting, CT would be typically used for guiding needle placement, while the fluoroscopy allows real-time evaluation of cement distribution during the injection. CT scanner can also be used to guide biopsies by identifying anatomical landmarks when lesions are only visible with other imaging techniques such as magnetic resonance imaging (MRI) or positron emission tomography (PET) scan [16, 19].
MRI guidance could be especially valuable when tumour lesions are not seen with other modalities . The absence of ionising radiation makes it an option for procedures in particular situations such as pregnancy. Because of its high soft tissue contrast, it can show chemical and thermal variations during tumour ablation procedures [5, 20]. However, its main disadvantages remain its higher cost, longer procedure times and limited availability. In addition, the material used during MR-guided interventions should be ideally compatible, which makes it more expensive, or used with special precautions [5, 20, 24].
Electromagnetic navigation allows real-time device tracking . Needle position information in the magnetic field is processed and placed on a preprocedural imaging (CT or MRI), which is used as a map. Generally, fluoroscopy or CT scan images are acquired to confirm the final needle placement in the target, as the main pitfall is the potential mismatch with the preprocedural images .
Other techniques, such as laser guidance, can facilitate needle placement [21, 22]. After CT or cone beam CT images are obtained, the target point is defined and a straight path from the skin is selected [21, 22]. A laser beam indicates the chosen entry site on the skin and the needle orientation [21, 22].
Approaches and essential landmarks
The safest approach for a percutaneous pelvic bone procedure varies depending on the level, as different important-to-avoid structures exit the pelvis through diverse foramina and vary their relative position. The following descriptions of safe approaches are based on CT scan, as it is the recommended modality for guiding percutaneous pelvic bone procedures . Four main levels can be considered:
Iliac wings level
In the supine position, an anterolateral approach through the anterior superior iliac spine to a target in the iliac wing (Fig. 4)
In the prone position, a posterior approach through the iliac tuberosity to a target in the iliac bone (Fig. 5)
In the prone position, a posterolateral approach through the sacroiliac joint (trans-sacroiliac) to a target in the sacral body or to biopsy the sacroiliac joint (Fig. 8)
In the prone position, a direct posterior or posterolateral approach (Fig. 9)
Acetabular roof level
For coccygeal biopsies, a posterior approach is safe, paying attention to visceral structures lying anterior to the coccyx (Fig. 13).
Hip joint level
Ischial tuberosity and pubic symphysis level
For every pelvic bone procedure, great care should be taken to avoid pelvic viscera, vessels and nerves during the approach to the lesion. Depending on the kind of procedure, other potential risks must be considered, such as non-target ablation and extraosseous cement leakage.
If a primary bone lesion is biopsied, gluteal muscles and rectus femoris should be avoided, as they are essential in a limb-sparing procedure and the needle tract would have to be resected [16, 26, 27, 28].
When a pelvic bone metastasis is favoured, intramuscular needle path is less determinant, albeit cases of tumour seeding along the needle path after core biopsy have been reported . A direct access through gluteal muscles can be used provided that no major vessels or nerves lie in the needle path. However, reducing the length of the path in the soft tissues decreases the risk of bleeding. Moreover, iliac lesions tend to have a longer diameter in the wing axis and more material can be sampled by accessing the lesion along its greater axis.
The choice of the needle depends on the mineralisation of the lesion and the presence of a cortical breach . A 14- to 16-G soft tissue cutting biopsy needle is the favoured choice whenever possible. A 10- to 16-G bone biopsy needle is indicated for dense lesions and when the cortex is intact. A coaxial technique is recommended because it allows keeping bone access to take several samples and occasionally perform percutaneous embolisation, and also protects the needle path from tumour dissemination [24, 25].
The number of samples required depends on the pathology department of each institution [3, 16, 24]. Usually two or three samples in formalin are enough [3, 24, 25, 26]. More samples may be needed when using smaller-gauge needles, mainly in paediatric patients . If a lymphoma is suspected, a sample in saline serum should be sent to allow the realisation of flow cytometry . Because infection is an occasional mimicker of bone tumours, systematically sending one or two samples for microbiological analysis is a good practice in uncertain cases .
Percutaneous tumour ablation
Percutaneous tumour ablation can be curative or palliative [5, 6, 7, 30]. There are several techniques available with different indications: ethanol, laser, radiofrequency, microwave and cryoablation [5, 6, 7, 30].
Different techniques have been described to prevent thermal damage to adjacent critical structures (mainly nerves and visceral structures), such as temperature monitoring to prevent overheating or overcooling, carbon dioxide gas or liquid dissection to increase the distance between the target area and critical structures and counteract temperature changes [30, 31, 32]. Covering the skin with sterile gloves filled with warm saline can also be helpful to prevent frost bites during cryoablation of superficial lesions (Fig. 22) .
Percutaneous screw fixation
All these described techniques can be used alone or in combination to obtain better pain control and mechanical support [5, 15, 16]. When combining techniques, it is usually feasible to use the same coaxial access to the target area, in order to reduce the risk of complications along the approach and to reduce the procedural time (Figs. 11, 12, 19 and 24).
In conclusion, pelvic bone procedures are safe to perform with an adequate knowledge of the anatomical landmarks. We described and illustrated multiple approaches to the most frequent targets at different levels of the pelvic bone. These approaches can be used for biopsies, percutaneous tumour ablation, cementoplasty, percutaneous osteosynthesis, or a combination of them. The principles of the different procedures and some practical and safety tips have been discussed as well.
Some of the diagrams included in the article have been presented partially in the RSNA 2007 electronic educational exhibit: Moser T, Buy X, Tok C, Irani F, Dietemann J, Gangi A. Image-guided interventions of the pelvic girdle: practical radioanatomy for a safe approach to a complex region. Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, 25-30 November 2007, Chicago. http://archive.rsna.org/2007/5005869.html
Two images of Fig. 19 (b and c) have been previously published in a Case Report: Bauones S, Freire V, Moser TP (2015) Retrograde transpubic approach for percutaneous radiofrequency ablation and cementoplasty of acetabular metastasis. Case Rep Radiol 2015:146963
- 14.Deschamps F, de Baere T, Hakime A et al (2016) Percutaneous osteosynthesis in the pelvis in cancer patients. Eur Radiol 26:1631–1639Google Scholar
- 17.Traina F, Errani C, Toscano A et al (2015) Current concepts in the biopsy of musculoskeletal tumors. J Bone Joint Surg Am 97:e7Google Scholar
- 19.Hillen TJ, Talbert RJ, Friedman MV et al (2017) Biopsy of CT-occult bone lesions using anatomic landmarks for CT guidance. AJR Am J Roentgenol 209:214–221Google Scholar
- 20.Guth SBX, Guermazi A, Gangi A (2009) Procedure basics and technique guidance. In: Gangi A, Guth S, Guermazi A (eds) Imaging in Percutaneous musculoskeletal interventions. Springer, New York, pp 1–14Google Scholar
- 26.Espinosa LA, Jamadar DA, Jacobson JA et al (2008) CT-guided biopsy of bone: a radiologist’s perspective. AJR Am J Roentgenol 190:W283–W289Google Scholar
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.