Carbon fiber lumbopelvic reconstruction following sacral giant cell tumor resection: illustrative case

Abstract

BACKGROUND

The use of carbon fiber or polyetheretherketone spine constructs has proven to be a safe and effective alternative to standard metal alloy. The mechanical properties of carbon fiber while unique provide a construct that is comparable in strength to previous titanium-based constructs and have additionally shown greater fatigue resistance. These constructs have been especially useful for the mechanical stabilization of the spine following tumor resection. The subsequent interference seen when imaging a patient with a traditional metallic construct is reduced and allows for improved tumor surveillance after the procedure, and a more accurate delivery of radiotherapy when indicated.

OBSERVATIONS

This case report details the treatment of a 25-year-old female diagnosed with a sacral giant cell tumor. The authors discuss the use of a carbon fiber-reinforced polyetheretherketone for lumbopelvic reconstruction.

LESSONS

Carbon fiber-reinforced polyetheretherketone with its radiolucency and rigidity is a reliable option for complex spinal reconstruction after tumor resection.

The treatment and stabilization of the spine using various constructs is dependent on the overall goal for the construct, and the ability of the materials to withstand the deforming forces placed on them. In general these properties are determined by the material that the rods and construct are made from, the diameter of the rod, and ultimately the shape they must assume.¹ Previous standard options included stainless steel, cobalt chrome, or titanium.² Although reliable, these alloys provide a high level of stiffness that has been associated with the development of adjacent segment disease.^3,4 Recently, the use of polyetheretherketone (PEEK) and carbon fiber-reinforced polyetheretherketone (CFRP) spine constructs has proven to be a safe and effective alternative to standard metal alloy.^5–7 The mechanical properties of carbon fiber, although unique, provide a construct that is comparable in strength to previous metal alloy-based constructs and have additionally shown greater fatigue resistance.⁸ These constructs have been especially useful for the mechanical stabilization of the spine after tumor resection.^5–7,9–13 The subsequent interference seen when imaging a patient with a traditional metallic construct is reduced and allows for improved tumor surveillance after the procedure, and a more accurate delivery of radiotherapy when indicated.^7,9,11 The present case report documents the use of a CFRP-based construct for lumbosacral fixation and sacral reconstruction after resection for a locally aggressive sacral giant cell tumor.

Illustrative Case

A 25-year-old female with a history of depression, anxiety, and panic attacks and a body mass index of 33.99 kg/m² presented with 3-month history of lower back pain. On initial presentation the patient had tenderness to palpation over the midline lumbar and lumbosacral junction with no associated neurological deficits. Initial imaging did not reveal any obvious osseous lumbar pathology (Fig. 1A and B). The patient was subsequently referred to physical therapy (PT). One week later, the patient re-presented to the clinic with worsening pain and new-onset paresthesia and numbness of the right thigh in the L5 distribution. The patient was prescribed meloxicam and flexeril for pain relief and again encouraged to attend PT. Two weeks later the patient presented to an outside emergency department after the pain had worsened, and she additionally developed right lower extremity weakness, which progressed to bilateral lower extremity weakness. During this admission, lumbar magnetic resonance imaging (MRI) demonstrated an infiltrative enhancing mass at L5–S1 with paravertebral epidural enhancement resulting in severe sacral spinal stenosis (Fig. 1C and D). Subsequently the patient underwent computed tomography (CT)-guided biopsy and was diagnosed with a giant cell tumor of the sacrum. The patient was noted to have significant mechanical instability and near-complete involvement of the sacrum at S1 and S2 resulting in lumbopelvic dissociation on CT (Fig. 1E and F). A plan was made to proceed with surgical debridement and intraoperative liquid nitrogen adjuvant therapy. Ultimately the patient underwent surgical debulking, bone grafting, and lumbopelvic stabilization. One dose of denosumab was received 1 month before surgery. Prior to surgery, the patient was assessed by interventional radiology for possible tumor embolization. Imaging did not reveal a safe target and tumor embolization was not performed. Preoperative anteroposterior (AP) and lateral radiographs were obtained (Fig. 1G and H).

FIG. 1.

Initial presentation clinic radiographs, AP (A) and lateral (B) views. Diagnostic sagittal (C) and axial (D) T2-weighted MRI with contrast shows sacral stenosis. Preoperative CT reveals lumbopelvic dissociation and sacroiliac destruction (E and F). Preoperative radiographs, AP (G) and lateral (H) views.

Operative Report

Initially, adequate exposure and correct level identification was performed followed by pedicle screw fixation bilaterally from L3–5 (Fig. 2A). Subsequently, bilateral iliac bolts were placed by creating a starting point with a bur at the iliac crest just deep to the posterior superior iliac spine using an awl. This was placed down the ilium just above the greater sciatic notch with appropriate imaging to avoid violation of the inner and outer table of the iliac wing (Fig. 2B–E). Longitudinal rods were prepared and locked in place. Bilateral laminectomy was performed from L5–S3. Lateral recess was decompressed with a Kerrison and foraminotomies were performed. Attention was then turned to dissection of the tumor off the sacral nerve roots, while S1–5 nerve roots were identified and protected. An open biopsy was performed and sent to pathology for permanent section. After tumor debulking was completed, three cycles of liquid nitrogen freezing followed by thawing were performed (Fig. 3A). Subsequently, an interiliac fibular strut graft was placed for reconstruction (Fig. 3B). Posterior elements were decorticated with a bur and bone grafts were packed into the posterolateral gutter. Additionally, bilateral SI fusion was completed using cancellous bone allograft without instrumentation. Four deep and one superficial drain were placed. Postoperative AP radiograph is shown in Fig. 4.

FIG. 2.

Intraoperative fluoroscopy of pedicle crew placemen (A). Intraoperative fluoroscopy of bilateral iliac bolt placements (B–E).

FIG. 3.

Intraoperative use of liquid nitrogen (A). Intraoperative photograph of interiliac fibular strut graft (B).

FIG. 4.

Postoperative AP radiograph.

Discussion

Giant cell tumors are common benign bone tumors that can be locally aggressive.¹⁴ Management of giant cell tumor in the spine are based on many factors including spine stability, and likelihood of complete resection. En bloc resection provides the greatest chance of curing the patient and limiting disease reoccurrence. The literature recommends that if the likelihood of neurological deficits and morbidity following en bloc resection are high, then local resection and embolization should be attempted.^14,15 For the present case, multiple approaches were considered including en bloc resection sacrificing the sacral roots, radiation treatment, observation, as well debulking curettage and bone grafting. En bloc resection was not pursued due to the anterior and posterior involvement of the sacrum with no ability to achieve wide resection for a cure, and thus provided limited to no benefit of sacrificing the sacral nerves.

Radiation therapy was withheld out of concern for malignant degeneration to sarcoma. Considering the development of rest pain and progressive neurological decline, observation was not a viable option. Ultimately, local aggressive curettage and bone grafting and a delta lumbopelvic reconstruction was pursued with intraoperative adjunctive liquid nitrogen therapy.

Observations

After surgery, the patient was discharged on postoperative day 7 on oral pain relief and scheduled for PT. Two weeks after the procedure, office visit revealed yellow drainage from the wound and no improvement in neurological symptoms prompting admission. Examination revealed continued drainage and several small sinus tracts at the distal end of the incision. She was subsequently taken to the operating room for debridement and washout and a wound vac was placed.

After the washout patient was prescribed vancomycin and piperacillin/tazobactam. Cultures revealed gram-negative rods, Proteus mirabilis, and patient was transitioned to vancomycin and ceftriaxone and a peripherally inserted central catheter was placed, antibiotics were continued for 6 weeks. Over the next 3 months the patient continued to improve and was again prescribed denusomab with plans to continue dosing every 4 weeks for 1 year. Eighteen months after surgery the patient is ambulatory with the use of bilateral ankle foot orthoses (AFO) and a cane. At 24 months after surgery, the patient has made marked improvement in her bilateral lower extremity strength with return of full motor 5/5 function in all muscle groups except for 4/5 ankle dorsiflexion (ADF) bilaterally. She is now ambulatory with the use of bilateral AFOs and a cane. Her persistent bilateral ADF weakness is likely due to neurological injury from prolonged tumor compression combined with possible thermal injury from the application of the liquid nitrogen, and from the surgical debulking and reconstruction. Fortunately, the patient’s pain is gone, but she continues to have numbness in the peroneal distribution, and mild sexual dysfunction. The most recent CT does not show any local recurrence (Fig. 5A–D). In addition, postoperative scoliosis AP pelvis and lateral sacral radiographs are included (Fig. 5E–H).

FIG. 5.

Postoperative CT does not show local occurrence (A–D). Postoperative scoliosis radiographs (E and F) show coronal and sagittal balance. Postoperative AP pelvis and lateral radiographs (G and H) show fibular strut graft to bridge the sacroiliac joint and solid reconstruction.

With limited availability in the United States and only a few constructs design available, limited literature exists describing the use of CFRP for lumbopelvic reconstruction. A survey of spinal oncology surgeons found a lack of consensus with regards to the imaging and radiation benefits, due to current construct availability. Therefore the routine use of these carbon fiber implants for anterior and posterior spinal reconstructions remains to be seen.¹⁶ Murthy et al.¹⁷ uniquely described the treatment of an osteosarcoma of the sacrum via a sacrectomy, right internal hemipelvectomy, en bloc resection of tumor utilizing an L3 to pelvis carbon fiber instrumentation. Yet, most cases of CFRP utilization have been for the treatment of cervical metastasis, but extensive lumbar reconstruction has been limited.¹⁸ In addition to availability, this may be partially attributable to difficulties using this material due to an inability to contour the rods as CFRP is less malleable and user-friendly than standard metal alloys.

The other alternative to CFRP, PEEK, has a surface that is relatively hydrophobic, limiting cell adhesion. In some instances, the biological activity of PEEK in vivo is unsatisfactory, and the capacity of the PEEK polymer surface to integrate with osteocytes is limited, which is contrary to the requirement of spinal fusion.¹⁹ However, by combining PEEK with bioactive materials such as carbon fiber, bioactivity can be enhanced. Additionally, Stubinger et al.²⁰ revealed that the CFRP equips exceptional osteoconductive and osteoinductive properties, which are beneficial in ultimately achieving spinal fusion.

Lessons

Traditional constructs such as titanium create extensive image artifact on imaging that impedes the determination of spinal tumors on radiographs, whereas CFRP exhibits superior radiopacity and allows for improved tumor surveillance using both CT and MRI imaging modalities.^9,11,21 The improved imaging and reduced artifact is related to the fact that CFRP as a lower density than standard constructs, which is similar to that of compact bone leading to less scattering and a more precise image.^22,23 Metal implants have a higher atomic number leading to a greater scattering effect and quantum noise. This advantage is beneficial for clinicians to better manage complex spinal tumors and to more clearly evaluate residual or recurrent tumor during follow-up, but light transmittance may also hinder evaluation of implant placement, especially intraoperative correction. Overall, this construct material allows for more accurate tumor follow-up and increased accuracy for radiation therapy.²⁴

CFRP constructs are viable option for the treatment of spinal neoplasms that require follow-up surveillance. The use of this construct in a complicated reconstruction is currently limited by availability and construct designs. Regardless, this case report reveals that sacral reconstruction using a CFRP construct is indeed possible and in the appropriately selected patient can provide adequate mechanical stability.

Disclosures

Dr. Shen reported being a consultant for CarboFix.

Author Contributions

Conception and design: Shen, Raso. Acquisition of data: Shen, Raso. Analysis and interpretation of data: Shen, Raso, Frank. Drafting the article: Shen, Raso, Chi. Critically revising the article: Shen, Raso, Chi. Reviewed submitted version of manuscript: Shen, Raso, Chi, Labaran. Approved the final version of the manuscript on behalf of all authors: Shen. Statistical analysis: Chi. Study supervision: Labaran.