Outcomes and Complications Associated With 191 Carbon Fiber Pedicle Screws in Spinal Oncology Patients

Carbon Fiber Instrumentation Use

Currently, titanium or cobalt-chrome instrumentation is commonly used for patients with metastatic spine disease with symptomatic epidural compression or spinal instability. However, titanium implants can produce imaging artifacts and diminish the effectiveness of postoperative radiotherapy.9 Interest in CFR-PEEK instrumentation for oncological spinal surgery has increased in recent years due to its radiolucent nature, which can help identify recurrence earlier and assist with radiation therapy planning.

CFR-PEEK spinal implants, first developed in 1978 and approved by the US Food and Drug Administration for human use in the 1990s, can circumvent some limitations of titanium instrumentation.10 CFR-PEEK instrumentation has many desirable properties, including high wear and radiation resistance and a relatively low Young’s modulus, which reduces stress shielding compared with titanium.11 However, its radiolucency may be the most critical attribute in this patient population, as it enables high-quality postoperative imaging with minimal artifact (Figure 3).

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Figure 3

A 68-year-old woman with a 20-y history of primary T3–T4 low-grade chondrosarcoma status after debulking, T1–T8 posterior spinal fusion, and proton beam radiation. The patient presented with thoracic pain without neurological deficits and concern for tumor recurrence. (A) Sagittal and (B) axial T2 magnetic resonance imaging without contrast of the thoracic spine demonstrate right-sided tumor recurrence at T3 (circle) with extension into the spinal canal and cord compression. Axial computed tomography (CT) without contrast at T1 (C) demonstrates bilateral titanium pedicle screws (solid arrows) from previous T1 to T8 fusion. (D) Right-sided destructive changes at T3 vertebral body. The patient underwent revision T3 partial corpectomy, T2–T4 laminectomy with removal of extradural tumor, and removal of T1–T7 instrumentation, with carbon fiber rods and screws replacement. Axial CT without contrast 3 mo after the operation demonstrates (E) bilateral carbon fiber screws at T1 (hollow arrows). (F) T3 status after partial corpectomy. Note the difference in imaging artifacts produced by titanium (C) compared with carbon fiber screws (E) (arrows).

The benefits of carbon implant systems must be weighed against the cost of these implants, which is often significantly higher than their titanium counterparts,12 as well as any unforeseen changes in the peri- and postoperative course due to the differences in material properties and/or implantation method. Unfortunately, much remains unknown about the use of CFR-PEEK in clinical practice and the outcomes of patients receiving CFR-PEEK instrumentation. Our case series details our experience with CFR-PEEK instrumentation, discussing complications and mortality in cancer patients who receive CFR-PEEK implants for both primary and metastatic spinal cancer.

The existing literature is similarly limited by variation in follow-up rates and median follow-up times. Patients with metastatic spine cancer have a median survival rate of 10 months, which may significantly contribute to varying follow-up intervals.13 Most tumors recur after the first 3 years; therefore, future studies should emphasize a follow-up period of at least 5 years to capture recurrence and remission rates.14

Recurrence

One of the main advantages of CFR-PEEK is its radiolucency, which reportedly enables more accurate imaging and precise photon therapy.11 A recent study by Ward et al compared local tumor recurrence rates and time to detection in patients with titanium alloy implants vs those with CFR-PEEK instrumentation.15 There was no significant difference in recurrence incidence between the groups. However, local recurrence in patients with CFR-PEEK implantations was detected on average 95 days earlier than in the titanium group.15 Early detection of recurrence enables timely intervention and treatment, preventing further spread. We recorded a recurrence rate of 9.1%, with a mean time to recurrence of 7.9 months, which is lower than rates reported in a similar study that used both titanium and CFR-PEEK instrumentation, which reported a recurrence rate of 57.9% at 6 months.16 However, in our series, given that our cohort was primarily palliative (89% metastatic and 40% mortality at ~5 months), faster recurrence detection is not necessarily applicable. Instead, adequacy of decompression immediately postoperatively is much more relevant to palliative patients.

Complications

Literature shows that the durability of CFR-PEEK is comparable to that of titanium alloy.17 In this study, 2.1% of cases exhibited breakage of CFR-PEEK pedicle screws.16 We report a similar figure of 2.8%, noting 1 instance, out of 36 procedures, in which a carbon fiber screw broke intraoperatively. A similar study with a median follow-up of 8 months using titanium alloy screws notes a failure rate of 13.8%, with 3.4% of failures requiring revision surgery. The risk factor for instrumentation failure was myelomatous spine lesions.17 The aforementioned carbon fiber screw break in our case series occurred in a patient with metastatic lung cancer who underwent hybrid instrumentation.

A study by Ringel et al stated that CFR-PEEK has no biomechanical inferiority to titanium screws and offers lower material fatigue and virtually unbreakable strength, which may be superior for long-term hardware stability. Pedicle screws break when the forces exerted on them by the surrounding anatomy exceed their ultimate strength along a given axis. Longer screws, on average, exhibit a greater bending strength.16 Therefore, the length should be considered when assessing the failure rate of CFR-PEEK screws. We were able to record the results of screws across a variety of levels with several different lengths, lending some external validity to the results of our work. However, our limited median follow-up time of 5 months precludes definitive conclusions on carbon fiber screw durability. Future prospective studies can better evaluate long-term screw integrity.

A postoperative complication rate of 16.7% (6/36) was recorded in our case series, similar to median spinal complication rates of 7% to 20%.18 This rate is lower when compared with complications and reoperation rates in spinal metastasis surgery with titanium alloy, which has a complication rate of 34%.2 Three patients had surgical site infections that required incision and drainage, and 1 patient had an epidural hematoma that required evacuation. Our relatively low rate of surgical site infections may be attributable, in part, to wound-complication prevention strategies implemented by the senior author, including intrawound vancomycin powder, which has been shown to substantially reduce the incidence of wound infections.19–21 The remaining 2 complications consisted of 1 patient with carbon fiber-only implants who underwent revision surgery within 2 weeks of surgery to reposition a right S1 symptomatic percutaneous screw. One patient developed a CSF leak that required reoperation and placement of a lumbar drain.

Physician Preference

Physician preference, health system contracting, and expenses are some of the determinants of whether CFR-PEEK will be commonly used for oncological spinal surgeries. Surgeons in each study concluded that CFR-PEEK instrumentation is comparable to or more advantageous than titanium alloy.8,22–28 Joerger et al and Boriani et al recommend their use in cancer patients due to improved cancer treatment, leading to more aggressive radiotherapy and therefore less surgery.27,28 Joerger et al included computed tomography and magnetic resonance imaging of CFR-PEEK instrumentation, demonstrating reduced perturbation effects and a more optimal postoperative radiotherapy regimen of 40/50 Gy á 2/2,5 G.27

Limitations

This case series was limited by a small sample size, which limits our findings. Additionally, follow-up durations varied, including imaging intervals, creating uncertainty in the assessment of the collected data. Overall, postoperative symptom improvement in patients with CFR-PEEK could not be thoroughly assessed because different scales were used, including the visual analog scale for pain and the ASIA Impairment Scale for neurological assessment. Despite the use of different assessment tools, each assessment reported improvements across both measures postoperatively, and our findings similarly showed improvements in ASIA motor scores. However, additional outcome measures, including patient-reported outcomes, would provide a more robust assessment; future prospective studies would benefit greatly from their incorporation. Last, during the literature search for this case series, we identified 8 articles reporting a total of 673 patients.8,15,23–28 However, nearly half (48%; n = 321) of these cases were from a single retrospective study by Joerger et al.27 This gap in existing studies underscores the importance of collecting more patient data on CFR-PEEK implants. Ultimately, more consistent research is needed to compare long-term outcomes with CFR-PEEK. Currently, CFR-PEEK seems to be an appropriate alternative to titanium alloy screws, and with more research, it may become the preferred treatment modality for spinal tumors.