Letter to the Editor. PEEK interbody device and pseudarthrosis

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TO THE EDITOR: We read, with keen interest, the article published by Krause et al.2 (Krause KL, Obayashi JT, Bridges KJ, et al: Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion. J Neurosurg Spine 30:46–51, January 2019). We commend the authors for analyzing this pertinent clinical problem. The authors concluded that the use of polyetheretherketone (PEEK) devices in 1-level anterior cervical discectomy and fusion (ACDF) is associated with a significantly higher rate of radiographically demonstrated pseudarthrosis and the need for revision surgery compared with the use of allografts. However, there are a few important points that we would like to bring to the attention of the readers of this journal.

Diabetes and osteoporosis are two important patient factors leading to pseudarthrosis, apart from smoking and obesity.3,4 We believe that the PEEK group and the allograft group must be matched for these probable confounding factors.

The authors mentioned that 408 patients underwent 1-level ACDF during the collection period, which ended in July 2016. Twelve patients received iliac crest autograft, and the remaining 396 received either PEEK cage or structural allografts. Only 127 met the study’s inclusion criteria. We would like to know if there were any other exclusion criteria besides inability to procure radiological follow-up of the remaining 269 patients. Kindly comment on the limited inclusion of 127 patients.

We would also like to know the material used (PEEK, structural allograft, or autograft) during the repeat surgery of patients with symptomatic pseudarthrosis following ACDF using PEEK cages. It would be pertinent to know if their symptoms resolved after the repeat surgery. The authors also mentioned that repeat ACDF with PEEK cage was done in the single case of symptomatic pseudarthrosis following primary ACDF with structural allograft. Although the use of PEEK versus allograft versus autograft in primary cervical arthrodesis is contentious, most studies support the use of autograft in revision operations to optimize fusion potential.3,5 It is relevant to know the thought process behind choosing PEEK cage in that scenario.

CT evaluation may actually omit the nonunion and overstate the fusion rates because of the imaging features of cortical allografts.1 Hence, the use of a single standardized method for evaluating pseudarthrosis in all cases will eliminate the intrinsic bias associated with using either one of these modalities.

Disclosures

The authors report no conflict of interest.

References

  • 1

    Gruskay JAWebb MLGrauer JN: Methods of evaluating lumbar and cervical fusion. Spine J 14:5315392014

  • 2

    Krause KLObayashi JTBridges KJRaslan AMThan KD: Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion. J Neurosurg Spine 30:46512019

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  • 3

    Leven DCho SK: Pseudarthrosis of the cervical spine: risk factors, diagnosis and management. Asian Spine J 10:7767862016

  • 4

    Lin WHa ABoddapati VYuan WRiew KD: Diagnosing pseudoarthrosis after anterior cervical discectomy and fusion. Neurospine 15:1942052018

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  • 5

    Simmons EHBhalla SK: Anterior cervical discectomy and fusion: a clinical and biomechanical study with eight-year follow-up. J Bone Joint Surg Br 51:2252371969

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INCLUDE WHEN CITING Published online June 14, 2019; DOI: 10.3171/2019.4.SPINE19276.

Response

We thank Drs. Sardana, Sahu, and Kedia for their interest and comments regarding our article. We would like to respond to the questions they posed.

First, we agree that diabetes and osteoporosis are both important factors to consider. In terms of diabetes, 6 (10.7%) of 56 patients in the PEEK group were diabetic compared to 10 (14.1%) of 71 in the structural allograft group. Despite the higher prevalence of diabetes in the structural allograft group, fusion rates were much higher. However, this does not take into account whether patients’ diabetes was well or poorly controlled. Osteoporosis prevalence was not studied in this patient population, but we agree that future prospective studies should control for osteoporosis.

Second, as mentioned in the manuscript, follow-up practices varied from surgeon to surgeon. Some surgeons did not see patients beyond a few months postoperatively, and others did not obtain imaging unless clinically indicated. The 269 excluded patients were so solely due to the lack of radiography at or after 12 months following surgery.

Third, all patients who suffered from pseudarthrosis with PEEK cages received posterior cervical fusion. Only one patient underwent a redo ACDF but had a posterior fusion in addition. All patients were clinically stable or improved following the reoperation.

Lastly, for one patient who suffered from pseudarthrosis in the setting of structural allograft, the surgeon who provided care is no longer at our institution, and the rationale behind the use of a PEEK cage for the revision surgery is not clearly documented. It should be noted, however, that the patient did ultimately require a posterior foraminotomy at the surgical level for persistent radiculopathy.

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Article Information

Correspondence Hardik Sardana: hardiksardana@yahoo.co.in.

INCLUDE WHEN CITING Published online June 14, 2019; DOI: 10.3171/2019.3.SPINE19244.

Disclosures The authors report no conflict of interest.

© AANS, except where prohibited by US copyright law.

Headings

References

  • 1

    Gruskay JAWebb MLGrauer JN: Methods of evaluating lumbar and cervical fusion. Spine J 14:5315392014

  • 2

    Krause KLObayashi JTBridges KJRaslan AMThan KD: Fivefold higher rate of pseudarthrosis with polyetheretherketone interbody device than with structural allograft used for 1-level anterior cervical discectomy and fusion. J Neurosurg Spine 30:46512019

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Leven DCho SK: Pseudarthrosis of the cervical spine: risk factors, diagnosis and management. Asian Spine J 10:7767862016

  • 4

    Lin WHa ABoddapati VYuan WRiew KD: Diagnosing pseudoarthrosis after anterior cervical discectomy and fusion. Neurospine 15:1942052018

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5

    Simmons EHBhalla SK: Anterior cervical discectomy and fusion: a clinical and biomechanical study with eight-year follow-up. J Bone Joint Surg Br 51:2252371969

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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