Prophylactic Percutaneous Consolidation of Large Osteolytic Tumors of the Pelvic Ring Using Fixation by Internal Cemented Screws

Abstract

Purpose

To evaluate the efficacy, durability, and safety of percutaneous fixation by internal cemented screw (FICS) for prophylactic consolidation of impending pathologic fractures of the pelvic ring.

Materials and Methods

In this single-institute retrospective study, patients with large, minimally symptomatic to asymptomatic osteolytic tumors of the pelvic ring that were treated with percutaneous cone-beam CT–guided FICS procedures were included (January 2014 to May 2019). Follow-up cross-section imaging and clinical reports were reviewed for procedural complications and assessment of the long-term consolidation efficacy on the basis of the development of pathologic fracture or need for additional surgical intervention. All continuous variables were expressed as a mean with standard deviation, and dichotomous variables were expressed as frequencies and percentages.

Results

Fifty consecutive patients (mean age, 60 years ± 12; 27 men) underwent prophylactic FICS for consolidation of 54 osteolytic tumors (mean size, 51 mm ± 21.5; range, 30–114 mm). Local tumor destruction was performed in association with FICS in 38 patients (76%) using percutaneous thermal and/or radiation therapy. Follow-up exceeded a year in 35 patients (70%), with mean follow-up of 22 months ± 18 (range, 1–67 months). Long-term consolidation efficacy was 98% (49 of 50), with the development of a pathologic fracture in only one patient 20 months after FICS. Procedural complications were limited to two patients with self-resolving hematoma, one patient with inflammatory sciatic pain, and one patient with focal pain at the ischial tuberosity.

Conclusion

Percutaneous FICS provides a safe and durable minimally invasive treatment for the prevention of pathologic fractures of the pelvic ring.

Keywords: Interventional-MSK, Percutaneous, Skeletal-Axial, Metastases, Oncology

Supplemental material is available for this article.

© RSNA, 2020

Summary

Percutaneous fixation by internal cemented screw can help prevent impending pelvic pathologic fractures in patients with large pelvic bone osteolytic tumors.

Key Points

• ■ At a mean follow-up of 22 months, fixation by internal cemented screw (FICS) of impending pelvic ring pathologic fracture showed durability with long-term consolidation efficacy achieved in 98% (49 of 50) of patients.

• ■ FICS is a safe treatment with 8% (four of 50) of minor complications and no major complications reported.

Introduction

As advances in oncology treatment shift cancer to a chronic medical condition, bone metastases have become a common occurrence (1). The pelvic bone is the most frequent site of bone metastases in patients with cancer after the spine and the ribs (2). Pathologic fractures occur in 17%–43% of patients with bone metastases and are responsible for reduced survival and quality of life from pain, loss of motor function, and impaired activities of daily living (3–5). Therefore, the prevention of pathologic pelvic fractures stands as a key issue to address.

While classification systems to trigger prophylactic treatment of femoral neck metastases are well established, there is no validated comprehensive scoring system for metastases to the pelvic ring. The Harrington classification does address metastases to the periacetabular region, and multiple factors have been advanced in clinical practice to help predict fracture risk, such as lesion size, location, osteolysis, and the extent of cortical disruption (6–8).

Surgical fixation for pathologic fractures of the pelvic ring has been increasingly focused on prevention (9,10). Pelvic surgery uses prostheses, metallic plates, and rods combined with cement to enable removal and reconstruction of destroyed bone. However, these traditional surgical techniques may be unfit in patients with advanced metastatic cancer who often have underlying nutritional or hematologic deficiencies. A systematic review of seven studies regarding open reduction and internal fixation of pelvic metastatic disease reports a perioperative mortality and complication rate of 3.3% and 19.5%, respectively (11). Complications include intraoperative hemorrhage, sciatic and femoral nerve injuries, prosthetic infections and dislocations, as well as late deep vein thrombosis (12). In addition to a relatively high surgical morbidity rate, the long recovery time for open surgery can require a lengthy delay or pause in systemic cancer treatments such as chemotherapy or immunotherapy.

Percutaneous cementoplasty was initially advanced to meet the need for a minimally invasive consolidative technique. Percutaneous cementoplasty is conceptually similar to vertebroplasty. It provides effective pain palliation by the precise image-guided injection of polymethyl methacrylate (PMMA) through needles to structurally reinforce tumor-destroyed bone outside of the spine (13–15). While PMMA helps to resist axial compression forces, cementoplasty is not ideal for locations in which torsion and shearing stresses predominate. Furthermore, large lytic defects might require additional reinforcement to spread weight-bearing stresses more evenly across the structural defect.

More recently, percutaneous fixation by internal cemented screw (FICS) has been developed as an improved consolidative method for pelvic pathologic fractures. The approach builds on existing percutaneous surgical techniques and has been advanced by interventional radiologists, by virtue of new imaging capability and image-guidance expertise, as an established, safe, and effective treatment (16,17). The addition of metallic screws provides the necessary resistance to torsion and shearing stresses that is needed in a weakened pelvic bone, with reduced morbidity compared with an open surgical approach (18, 19). While FICS has been proven an effective tool to stabilize pathologic fractures of the pelvic ring, the assessment of the potential of FICS as a prophylactic treatment for impending pathologic fractures of the pelvis is an open area of investigation.

The objective of this study was to determine the safety, efficacy, and durability of percutaneous FICS in the prophylactic treatment of impending pathologic fracture of the pelvic ring within a large cohort of patients with cancer.

Material and Methods

This retrospective single-center study obtained institutional board review approval, and written consent was obtained in accordance with the policy of our institution regarding chart reviews.

Study Design

We retrospectively reviewed the files of all patients with cancer who underwent percutaneous FICS for prophylactic consolidation of the pelvic ring from January 2014 to May 2019 in our tertiary care cancer center. The inclusion criteria were FICS of the pelvic ring, minimally symptomatic to asymptomatic patients with large (greater than 3 cm) osteolytic tumor of the pelvic ring, without demonstrable pathologic fracture at the last preprocedural CT examination. Patients were considered minimally symptomatic to asymptomatic if the self-reported baseline pelvic pain, in the absence of opioid pain medication, was equal to or below 3 out of 10 on the visual analgesic score. In all cases, the decision to proceed with prophylactic percutaneous FICS treatment had been made by a multidisciplinary pain board composed of a pain-specialized physician, a radiation therapy oncologist, an orthopedic surgeon, and an interventional radiologist. Figure 1 shows a patient flowchart with inclusion and exclusion criteria. None of these patients were included in previous studies.

Figure 1:

Flow diagram of inclusion and exclusion of patients within the study. FICS = fixation by internal cemented screw.

Data Collection

Data were collected from the preprocedural CT, interventional radiology consultation, and anesthesiology consultation, which were all performed within 4 weeks of the FICS procedure. Details recorded included patient age, sex, primary tumor location and histopathologic results, Eastern Cooperative Oncology Group (ECOG) performance status, oral pain regimen, and self-reported pain intensity by using the visual analgesic score. Preprocedural CT images were analyzed to measure the size and radiographic characteristics of the tumor, extent of cortical bone erosion, and tumor location in the pelvic ring according to the Enneking classification: ilium, acetabulum, pubis, or sacrum (Fig E1 [supplement]) (20). In addition, the severity of periacetabular tumors was graduated by using the Harrington classification (Fig E2 [supplement]) (6). Additional chart review was performed for prior or subsequent treatments by radiation therapy, percutaneous thermal ablation (radiofrequency ablation or cryoablation), or surgery, as well as the FICS procedural details, including total procedure time and subsequent hospital stay duration.

The safety of the procedure was assessed by evaluation of clinical consultations reports. Long-term consolidation efficacy after FICS was met if no screw dislodgment and no pathologic fracture occurred during the follow-up period. Long-term consolidation efficacy was assessed by reviewing all postprocedural cross-sectional images. All patients underwent a postprocedural interventional radiology clinical consultation and a pelvic CT examination between 4 and 6 weeks after the FICS procedure. Patients were subsequently followed by their medical oncologist with CT examinations every 3 months per standard cancer surveillance guidelines. Any pelvic fracture sustained after the FICS procedure was reported, with specifics regarding type of fracture, the time interval between FICS and fracture, and the subsequent treatment.

Pelvic FICS Procedures

FICS procedures were performed under general anesthesia by three interventional radiologists with more than 5 years of experience in bone procedures (F.D., L.T., C.R.). After sterile preparation, a cone-beam CT (Innova 4100-IQ; GE Healthcare) of the pelvis was performed to plan the most appropriate screw trajectories. The screw track was chosen among seven options on the basis of the tumor location and the integrity of the adjacent normal bone: anterior or posterior transiliac track, anterior or posterior iliopubic track, ischiopubic track, transischial track, and transsacroiliac track (Fig E3 [supplement]). Fluoroscopic guidance and navigation software (TrackVision; GE Healthcare) were used to guide an 8-gauge needle across the tumor. An additional cone-beam CT was performed to confirm exact placement of the needle and to measure the appropriate length for the cannulated screw. Screw placement and length were determined to provide an effective bridge or lintel bar that spans the tumor and transmits the load stress along the screws across the tumor defect and into stable bone on either side. For better consolidation and to avoid screw displacement, we developed a coaxial approach to anchor the screw tip in PMMA cement (anchorage cementoplasty). For this purpose, PMMA (Bone Cement V; Zimmer Biomet) was injected first under close fluoroscopic observation through the 8-gauge needle and then this needle was rapidly and coaxially exchanged over a 3.2-mm Kirschner wire (Threaded Guide Wire Asnis III; Stryker) before equally rapid advancement of an 8-mm partially threaded cannulated screw (Asnis III; Stryker) over the Kirschner wire with a manual screwdriver before the PMMA could harden. Additional PMMA was occasionally injected after the screw insertion through additional 8-gauge needles (consolidation cementoplasty) if the interventional radiologist deemed it appropriate for added consolidative effect in large lytic metastasis. More details about technical parameters of FICS can be found in previous publications by our team (21).

We defined technical success as a screw positioned across the tumor with proximal anchorage against nonlytic cortex and distal anchorage in nonlytic bone, without screw protrusion from the osseous margins. Long-term consolidation efficacy was achieved if no pathologic fracture was identified at follow-up imaging after FICS.

Statistical Analysis

All continuous variables were expressed as a mean with standard deviation, and dichotomous variables were expressed as frequencies and percentages when relevant.

Results

Patient Characteristics

From June 2014 to May 2019, a total of 332 patients with cancer underwent percutaneous FICS in our tertiary care cancer center (262 pelvic ring FICS, 61 femoral neck FICS, and nine sternal FICS). A total of 70 patients were excluded for having femoral neck or sternum FICS. Among the patients with pelvic ring FICS, 212 patients presented with symptomatic pelvic fractures or high focal pain and were excluded. Included in this study were the 50 patients (27 men and 23 women) in which FICS was performed for prophylactic consolidation of 54 minimally symptomatic to asymptomatic osteolytic tumors of the pelvic ring.

As shown in Table 1, mean age was 60 years ± 12 (men, 58 years ± 9; women, 63 years ± 15), and cancer types were breast (n = 14), renal (n = 9), multiple myeloma (n = 8), lung (n = 4), thyroid (n = 3), hepatocellular (n = 2), and various less common types (n = 10). Mean ECOG performance status was 0.7 ± 0.7 (range, 0–2). All tumors exceeded 30 mm in greatest diameter with mean greatest diameter of 51 mm ± 21.5 (range, 30–114 mm). Ninety-one percent (49 of 54) of the tumors were solely osteolytic, while 9% (five of 54) manifested with a mixed sclerotic-lytic radiographic appearance. Tumors were located in the ilium (n = 20), acetabulum (n = 18), pubis (n = 5), and sacrum (n = 11). Tumors of the acetabulum region were mostly ranked Harrington III (78%; 14 of 18), while Harrington II and Harrington I tumors accounted for 17% (three of 18) and 6% (one of 18), respectively. Cortical involvement was present in 85% (46 of 54).

Table 1:

Patient and Tumor Characteristics

FICS Procedure

Table 2 details the FICS procedures performed. Technical success was achieved in 49 out of 50 patients (98%). The one technical failure was the result of extremely dense bone, possibly a result of the radiation therapy that was performed between the preprocedural CT examination and FICS procedure. The placement of the screw was not possible, and the procedure was aborted. In the 49 technical successes, a total of 72 screws were inserted (average, 1.4 ± 0.6 per patient; range, 1–3). The screws were reinforced with PMMA using the anchorage technique in 41 patients (82%) and the consolidation technique in 19 patients (38%) for additional consolidation of a large lytic defect. No PMMA was injected in three patients (6%) with mixed sclerotic-lytic disease because the peritumoral bone was deemed sufficiently strong by manual assessment during screw advancement. Cases of patients with FICS using the anchorage and the consolidation techniques for cementoplasty are displayed in Figures 2 and 3.

Table 2:

FICS Procedures Details

Figure 2:

Example of prophylactic fixation by internal cemented screw (FICS) by using the anchorage technique. Images in a 51-year-old woman with metastatic renal cancer who underwent radiation therapy 9 days prior to fixation by FICS. A, Preprocedural axial noncontrast CT image shows a 51-mm–wide osteolytic sacral metastasis with extensive cortical disruption. B, Postprocedural axial noncontrast CT image shows one of the transsacroiliac screws with anchorage cement at the tip. FICS steps: C, Insertion of two 8-gauge needles by the right transsacroiliac track; D, injection of polymethyl methacrylate cement through the needles; E, exchange of the needles over Kirschner wires and insertion of two 8-mm and 10-cm screws; and, F, withdrawal of the wires and final result.

Figure 3:

Example of prophylactic fixation by internal cemented screw (FICS) by using both anchorage and consolidation techniques. Images in a 63-year-old woman with multiple myeloma who underwent radiation therapy 2 months prior to FICS. A, Preprocedural sagittal noncontrast CT image shows a 63-mm–wide osteolytic tumor of the acetabulum involving the superior acetabular wall. B, Postprocedural sagittal noncontrast CT image shows the anterior transiliac screw and additional cement for consolidation FICS steps: C, insertion of two 8-gauge needles by the ascending and descending anterior transiliac tracks; D, injection of polymethyl methacrylate cement through the needles; E, insertion of one 8-mm and 11.5-cm screw through the ascending transiliac track; and, F, final result from a straight frontal view.

As reported in Table 3, the chosen screw track among the seven tracks available (Fig E3 [supplement]) depended on the tumor location. Iliac tumors were treated with screws advanced by transiliac tracks (anterior or posterior), pubic tumors by transiliopubic tracks (anterior or posterior), and sacral tumors by transsacroiliac tracks. Periacetabular tumors were mostly approached by the anterior transiliac, posterior transiliopubic, and transischial tracks. The ischiopubic track was not used in this cohort of patients.

Table 3:

Screw Track and Tumor Location

The mean procedure duration was 102 minutes ± 41 and mean postprocedure hospitalization stay was 2.5 days ± 1.8. Local tumor destruction was performed in association with FICS in 38 patients by using percutaneous thermal ablation only (n = 9), radiation therapy only (n = 27), or both (n = 2).

Outcome Analysis

As shown in Table 4, mean follow-up was 22 months ± 18 (range, 1–67). Follow-up exceeded 12 months for 35 patients (70%). Twenty patients (40%) had died of advanced cancer progression after a mean follow-up of 13 months ± 11 (range, 1–42 months), six patients (12%) were lost to follow-up after a mean follow-up of 13 months ± 13 (range, 2–35 months), and 24 patients (48%) were still alive after a mean follow-up of 32 months ± 18 (range, 8–67 months).

Table 4:

Outcome Analysis

All patients but one underwent follow-up pelvic CT examinations. The mean time to the last follow-up CT examination was 18 months ± 15 (range, 0–52 months). During the follow-up period, 13 patients (26%) showed local progression of disease on the basis of CT or PET/CT evaluation.

Long-term consolidation efficacy was achieved in 98% (49 of 50) of patients. One patient with a 60-mm Harrington III acetabulum breast cancer metastasis developed a pathologic fracture along the superior acetabular wall 20 months after FICS. The follow-up CT images had shown local progression after FICS, which had not been treated with radiation therapy nor percutaneous thermal ablation aside. Because of the patient’s comorbidities, the pathologic fracture was subsequently treated with external radiation therapy for local tumor control and with additional FICS for further palliative consolidation 21 months after the first procedure. Despite these subsequent interventions, the pathologic fracture progressed 5 months after the second FICS procedure. A total hip replacement was performed 13 months after the second FICS procedure.

Four patients experienced early mild complications after FICS. Two patients presented with small- to medium-sized hematomas that resolved spontaneously. One patient experienced inflammatory sciatic pain that was conservatively managed with oral anti-inflammatory medication. One patient who had a screw placed in the ischium with an ischiopubic track had focal pain when sitting because of pressure on the screw head that had not been buried beneath the ischial tuberosity cortex. Because pain was not alleviated with oral medication, percutaneous removal of the screw was performed 26 days after the FICS procedure, with subsequent pain relief.

The mean postprocedure visual analgesic score was 0.76 ± 1.73. Four patients reported a higher postprocedure pain, which was not related to the procedure, but to tumor progression in the pelvis (three patients) or lumbar spine (one patient).

Discussion

Despite the clinical relevance, no comprehensive guidelines exist for prophylactic consolidation of pelvic bone osteolytic tumors. Preventative and reactive open surgery can be quite invasive, portends unfavorable morbidity and mortality rates, and can further delay systemic therapy during the healing period. The treatment paradigm for fixation of these osteolytic tumors has recently expanded to minimally invasive procedures. Advanced imaging equipment, such as fluoroscopic cone-beam CT and hybrid CT-fluoroscopy units, have expanded the potential for real-time image guidance and combination of local-regional therapies (19). FICS performed under cone-beam CT guidance has already been proven efficient and safe for bone fractures in the pelvic ring (14,21–23). All previously published studies report treatment for patients with documented pathologic bone fractures or patients with high self-reported pain on weight-bearing that suggests the presence of microfractures.

Our study focused solely on prophylactic fixation of pelvic ring osteolytic tumors. Procedural success was achieved in 98% (49 of 50) of patients, with a low complication rate of 8% (four of 50), including only minor complications. Long-term consolidation efficacy with absence of progression to pathologic fracture was reported in 98% (49 of 50) despite a locally progressive disease in 26% of patients (13 of 50). In the sole patient with fracture development, the consolidated tumor measured 60 mm in maximal dimension at the time of FICS, and the fracture developed 20 months after the FICS procedure as a result of local tumor progression.

Importantly, the FICS procedures did not result in any delays in chemotherapy, immunotherapy, or radiation therapy. Because local tumor destruction by radiation therapy or percutaneous thermal ablation is known to weaken the bone, the ability to perform the FICS procedure after these local tumor control treatments is important to preventatively consolidate the weakened weight-bearing bone (22). Screw tracks were selected depending on the tumor location to allow appropriate bridging of the tumor defect. In our experience, screws advanced by an inferior ischiopubic approach should be buried completely beneath the ischial tuberosity cortex to minimize the risk of focal buttock pain when sitting.

We acknowledged several limitations of our study. We specifically decided to exclude patients with symptomatic pelvic bone metastases (visual analgesic score > 3) since we aimed to evaluate the use of FICS in a prophylactic approach. In the absence of a control group, it was not possible to know precisely how many fractures were prevented because of FICS. However, several factors supported that the FICS procedure was responsible for prevention of progression to pathologic fracture. The osseous tumor defects all measured 30 mm or greater (mean, 51 mm ± 21.5; range, 30–114 mm), and cortical disruption was present for the great majority (85%). Moreover, all patients were in a general good performance status (mean ECOG, 0.7 ± 0.7; range, 0–2) and bearing weight on a daily basis, suggesting that the stresses of daily activities might have led to fracture in the absence of FICS. Last, the follow-up time (mean, 22 months ± 18; range, 1–67 months) was much longer than in most studies involving patients with bone metastases where median follow-up time usually ranged from 7 to 12 months (13,23,24).

An additional study limitation was the absence of correlation of prior or concomitant systemic therapy, which was an intentional omission given the wide variety of cancer types and systemic therapies. Instead, the decision was made to focus on the technical outcomes and failures of the FICS procedure, which can be performed in association with various local and systemic cancer treatments because of the minimally invasive nature of the FICS procedure. On the basis of our preliminary work, a prospective study with a control group or a matched study with an institution that does not have FICS capability could address this limitation. It would help to select patients who would benefit the most from percutaneous FICS as a prophylactic treatment.

Percutaneous FICS is a safe and durable treatment to prevent pathologic fractures in patients with asymptomatic large osteolytic tumors of the pelvic ring. Prevention of pathologic pelvic fractures can provide critical structural support to extend functional performance and weight-bearing potential, without interrupting systemic therapies.