Minimally invasive procedure enhances care for periacetabular osteolytic metastasis
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Massive osteolytic metastases in the periacetabular regions are clinical dilemmas.
The classical teaching 10 to 20 years ago was that orthopedic stabilization of osteolytic metastases in the femur and pelvis was for palliative care and a comfort measure for better quality of remaining life. These days, the medical oncology specialty has changed dramatically. Prolonged survival is often seen after trying new generations of oncologic drugs that specifically target cell signaling or augment host immune responses. Some cancers are now considered as a chronic manageable disease.
Source: Francis Y. Lee, MD, PhD
Most common orthopedic procedures for periacetabular osteolytic metastases are adopted from trauma or arthroplasty techniques using metal implants through extensive open surgical approaches. Orthopedic reconstructive surgeries using megaprostheses, 3D custom implants, and plates and screws are associated with prolonged recovery from muscle dissections, infection, delayed wound healing, transfusion, medical complications and hospitalization.
AORIF procedure
The musculoskeletal tumor research team at Yale School of Medicine challenged a classical treatment paradigm for periacetabular osteolytic metastases that do not respond to chemotherapy, radiation and antiresorptive agents. Fundamental provocative questions are related to extensive open surgical approaches to reconstruct small bone defects around the acetabulum and bone reinforcement without addressing recalcitrant cancer cells.
We published several articles on cancer-induced biology, biomechanics and clinical outcomes following a minimally invasive treatment for periacetabular osteolytic metastases. Certain types of cancer cells, such as breast, lung, kidney and thyroid, create inflammation in the bone, thereby increasing osteoclastic bone resorption and inhibiting osteoblastic bone formation. Antiresorptive treatments, such as denosumab or bisphosphonates, do not completely prevent bone loss because metastatic cancer cells inhibit osteoblastic bone repair while promoting osteoclastic bone resorption. Metastatic cancers are usually resistant to radiation or drug therapies. Therefore, chemotherapy- and radiotherapy-resistant cancer cells need to be killed to halt the cancer-induced bone loss. Local cancer control can be accomplished with radiofrequency ablation.
The weight-bearing portion of the acetabulum is located in a small area in the superior-medial aspect. We performed a biomechanical study that compared maximal strength and cyclic loading capacity among cement fixation alone, screw fixation alone and a combination of cement plus screw fixation. Combination of cement plus screw fixation improved biomechanical integrity for weight-bearing. The use of cement is advantageous not only for providing immediate stability but also for thermal necrosis of cancer cells. Zoledronate is a heat-stable bisphosphonate drug that can be mixed with polymethylmethacrylate (PMMA) bone cement. It has been shown that zoledronate-loaded bone cement is safe and effective in suppressing recurrence of giant cell bone tumors.
Based on our rigorous scientific data on molecular biology, biomechanics and clinical data, we can offer immediate benefits to patients with ablation-osteoplasty-reinforcement-internal fixation (AORIF). A new minimally invasive procedure, AORIF will reduce cancer burden by radiofrequency ablation along with thermal necrosis by zoledronate-loaded bone cement that also fills the defects through percutaneous cannulated screws. Balloon osteoplasty is used to open the space for initial cement deposition in the liquified cancer following radiofrequency ablation. Cement flows the path of least resistance, and the balloon inflation-created space assures the initial deposition of injected cement through cannulated screws. Balloon osteoplasty also collapses tumor vessels and minimizes bleeding and cement embolization.
Key technical points
With reduction of cancer cells and bone-protective action of zoledronate, an increase in bone mass is often observed after AORIF. This procedure can be used as a first-line provisional procedure to prolong life and to consider secondary open surgical procedures in long-term surviving patients, if needed. Overall, AORIF is ideally suited for modern oncology.
Indications and contraindications: AORIF is indicated for any painful osteolytic or mixed blastic-lytic periacetabular metastatic cancer-induced bone defects that cause pain and decrease ambulatory function secondary to skeletal metastases. Previously failed chemotherapy or radiation therapy are not contraindicated. Subchondral fractures and protrusio acetabuli are not contraindications.
Preoperative planning: Plain radiographs and CT scans are reviewed to identify the defects that are responsible for painful impaired ambulation on coronal, sagittal and axial images. Only key defects, such as in the superomedial aspect, are addressed (Figure 1).
Position and draping: Most cases are done in the supine position with a small block draping. If there are concurrent posterior iliac crest or sacro-iliac joint lesions, prone position is used.
Intraoperative imaging: Biplane C-arm fluoroscopy is used once experience is gained using 3D imaging, such as cone beam CT, Ziehm C-arm, O-arm or navigation system.
Insertion of guidewires: The anterior iliac crest, the most superficial, palpable and strongest bone, is most commonly used to reach the weight-bearing portion of the acetabulum (Figure 2 and Figure 3). Typically, guidewires for two cannulated screws are used to prevent rotation and cement embolization. An additional guidewire is used for the anterior acetabulum-pubic rami junction in diffuse osteolytic lesions. The iliac crest view shows the anterior and posterior iliac crest like a hairpin loop. The iliac wing view shows the posterior acetabular wall, sciatic notch and ischial spine. The iliac crest and iliac wing views are perpendicular to each other in two planes. Screw fixation patterns may vary, but the most common screw configuration is insertion of two screws in the anterior iliac crest region for decompressing pressure and anti-rotation effects.
Cannulated screw fixation and biopsy: Cannulated screws are used so that catheters are readily passed through the screw head percutaneously. Most commonly, cannulated screws are partially inserted, and visible screw head cannulas serve as portals for ablation, balloon dilatation and cement delivery under direct vision and fluoroscopic guidance (Figure 2). A biopsy specimen may be taken through the cannulated screw when a new specimen is needed.
Radiofrequency ablation: Most stage IV cancers are chemotherapy- and radioation-resistant. Cancers are responsible for bone destruction by creating inflammation at the metastatic sites. Therefore, cancers are debulked by radiofrequency ablation thermal necrosis. Radiofrequency ablation also liquefies the cancer matrix for easier cement delivery. Because cryoablation may cause avascular necrosis of the femoral head, cryosurgery may be considered when the lesion is far away from the femoral head.
Balloon osteoplasty: Cement leaks through the path of least pressure and resistance. Balloon inflation is done in the radiofrequency ablation-liquified cancer so that the initial cement deposition site is created. Balloon inflation produces pressure and has secondary effects of collapse of tumor vessels, decreased bleeding, formation of wall for less cement leakage and decreased cement embolization. Balloons may rupture when there are sharp bony spicules, or when the tumor matrix is stiff. There are no harmful effects of rupture of balloons that contain normal saline and radio-opaque dye (Figure 2).
Cement injection through cannulated screws: High viscosity cement is delivered with the help of a well-controlled cement delivery system through cannulated screws under intermittent fluoroscopic imaging guidance. PMMA bone cements are often mixed with zoledronate that is a heat-stable anti-resorptive agent. For 20 g of cement, 0.5 mL of 4 mg/5 mL zoledronate is mixed. Many patients have massive loss of subchondral bone defects. The cement forms a new subchondral roof, and apparent cement leakage is not detrimental for ambulation. High viscosity cements do not commonly generate loose cement fragments.
Advancement of screws through curing bone cement: Guidewires are placed through the cannulas. Screws are advanced through curing PMMA bone cement (Figure 3).
Post-AORIF care and follow-up: Outpatients are sent home on the day of AORIF. Inpatients return to the oncology floor. Weight-bearing is allowed as tolerated. CT scans are obtained as part of a standard oncology staging study. Radiographs are obtained at the orthopedic clinic at 3-month intervals (Figure 4). Complications that can be expected from open surgeries are all precluded.
Resume oncologic care: Owing to the percutaneous nature of the procedure, patients may resume any medical drug therapies the next day.
Outcomes
In a prospective cohort of 72 patients with periacetabular osteolytic metastases, we found more than 50% of patients survived beyond 1 year after AORIF. There were no cases of complications, infections or readmissions. One patient required hemiarthroplasty 2 years for the flattened femoral head against the deformed acetabulum following comminuted acetabular pathological fracture and restoration of bone mass. CT scans collected preoperatively and postoperatively in the first 3 months and beyond 6 to 12 months after AORIF in 22 patients showed increased Hounsfield units. This increased bone mass was attributed to combinations of cancer cytoreduction by radiofrequency ablation and thermal necrosis, and locally eluted zoledronate. Overall survival was prolonged compared to PathFx 3.0-predicted survival and was attributed to immediately enhanced ambulatory function that allowed continued or initiation of oncologic care without delay. The 17 patients who had severe subchondral bone loss and protrusion acetabuli also experienced decreased pain and increased ambulatory function after AORIF.
It is an exciting time for orthopedic oncologists to provide minimally invasive but comprehensive oncologic care for periacetabular osteolytic metastases, thereby facilitating life-prolonging anticancer drug therapies.
- References:
- Back J, et al. Bone Res. 2021;doi:10.1038/s41413-021-00158.
- Chang SS, et al. Clin Orthop Relat Res. 2004;doi:10.1097/01.blo.0000141372.54456.80.
- Dussik CM, et al. Radiology. 2023;doi:10.1148/radiol.221401.
- Greenberg DD, et al. Am J Clin Oncol. 2019;doi:10.1097/COC.0000000000000504.
- Ibe I, et al. J Bone Joint Surg Am. 2023;doi:10.2106/JBJS.22.00694.
- Jiang W, et al. Cardiovasc Intervent Radiol. 2023;doi:10.1007/s00270-023-03425-x.
- Lee FY. Instr Course Lect. 2022;71:213-220.
- Morris MT, et al. Clin Biomec (Bristol, Avon). 2022;doi:10.1016/j.clinbiomech.2021.105565.
- For more information:
- Gary Friedlaender, MD; Igor Latich, MD; Francis Y. Lee, MD, PhD; and Dieter Lindskog, MD, can be reached at the Orthopaedic Oncology Service in the department of orthopaedics and rehabilitation at Yale School of Medicine in New Haven, Connecticut. Lee’s email: francis.lee@yale.edu.
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