Tag: PEEK

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Predictors of subsidence after lateral lumbar interbody fusion

J Neurosurg Spine 37:183–187, 2022

Lateral lumbar interbody fusion (LLIF) facilitates the restoration of disc height and the indirect decompression of neural elements. However, these benefits are lost when the graft subsides into the adjacent endplates. The factors leading to subsidence after LLIF are poorly understood. This article presents a case series of patients who underwent LLIF and reports factors correlating with subsidence.

METHODS A retrospective review of a consecutive, prospectively collected, single-institution database of patients who underwent LLIF over a 29-month period was performed. The degree of subsidence was measured on the basis of postoperative imaging. The timing of postoperative subsidence was determined, and intraoperative fluoroscopic images were reviewed to determine whether subsidence occurred as a result of endplate violation. The association of subsidence with age, sex, cage size and type, bone density, and posterior instrumentation was investigated.

RESULTS One hundred thirty-one patients underwent LLIF at a total of 204 levels. Subsidence was observed at 23 (11.3%) operated levels. True subsidence, attributable to postoperative cage settling, occurred for 12 (5.9%) of the levels; for the remaining 11 (5.4%) levels, subsidence was associated with intraoperative endplate violation noted on fluoroscopy during cage placement. All subsidence occurred within 12 weeks of surgery. Univariate analysis showed that the prevalence of true subsidence was significantly lower among patients with titanium implants (0 of 55; 0%) than among patients with polyetheretherketone cages (12 of 149; 8.1%) (p = 0.04). In addition, the mean ratio of graft area to inferior endplate area was significantly lower among the subsidence levels (0.34) than among the nonsubsidence levels (0.42) (p < 0.01). Finally, subsidence among levels with posterior fixation (4.4% [6/135]) was not significantly different than among those without posterior fixation (8.7% [6/69]) (p = 0.23). Multivariate analysis results showed that the ratio of cage to inferior endplate area was the only significant predictor of subsidence in this study (p < 0.01); increasing ratios were associated with a decreased likelihood of subsidence.

CONCLUSIONS Overall, the prevalence of subsidence after LLIF was low in this clinical series. Titanium cages were associated with a lower prevalence of observed subsidence on univariate analysis; however, multivariate analysis demonstrated that this effect may be attributable to the increased surface area of these cages relative to the inferior endplate area.

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Nonunion Rates After Anterior Cervical Discectomy and Fusion: Comparison of Polyetheretherketone vs Structural Allograft Implants

Neurosurgery 89:94–101, 2021

Although advances in implant materials, such as polyetheretherketone (PEEK), have been developed aimed to improve outcome after anterior cervical discectomy and fusion (ACDF), it is essential to confirm whether these changes translate into clinically important sustained benefits.

OBJECTIVE: To compare the radiographic and clinical outcomes of patients undergoing up to 3-level ACDF with PEEK vs structural allograft implants.

METHODS: In this cohort study, radiographic and symptomatic nonunion rates were compared in consecutive patients who underwent 1 to 3 level ACDF with allograft or PEEK implant. Prospectively collected clinical data and patient-reported outcome (PRO) scores were compared between the allograft and PEEK groups. Regression analysis was performed to determine the predictors of nonunion.

RESULTS: In total, 194 of 404 patients met the inclusion criteria (79% allograft vs 21% PEEK). Preoperative demographic variables were comparable between the 2 groups except for age. The rate of radiographic nonunion was higher with PEEK implants (39% vs 27%, P = .0035). However, a higher proportion of nonunion in the allograft cohort required posterior instrumentation (14% vs 3%, P = .039). Patients with multilevel procedures and PEEK implants had up to 5.8 times the risk of radiographic nonunion, whereas younger patients, active smokers, and multilevel procedures were at higher risk of symptomatic nonunion.

CONCLUSION: Along with implant material, factors such as younger age, active smoking status, and the number of operated levels were independent predictors of fusion failure. Given the impact of nonunion on PRO, perioperative optimization of modifiable factors and surgical planning are essential to ensure a successful outcome.

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PEEK versus titanium cages in lateral lumbar interbody fusion: a comparative analysis of subsidence

Neurosurg Focus 49 (3):E10, 2020

The authors have provided a review of radiographic subsidence after lateral lumbar interbody fusion (LLIF) as a comparative analysis between titanium and polyetheretherketone (PEEK) cages. Many authors describe a reluctance to use titanium cages in spinal fusion secondary to subsidence concerns due to the increased modulus of elasticity of metal cages. The authors intend for this report to provide observational data regarding the juxtaposition of these two materials in the LLIF domain.

METHODS A retrospective review of a prospectively maintained database identified 113 consecutive patients undergoing lateral fusion for degenerative indications from January to December 2017. The surgeons performing the cage implantations were two orthopedic spine surgeons and two neurosurgeons. Plain standing radiographs were obtained at 1–2 weeks, 8–12 weeks, and 12 months postoperatively. Using a validated grading system, interbody subsidence into the endplates was graded at these time points on a scale of 0 to III. The primary outcome measure was subsidence between the two groups. Secondary outcomes were analyzed as well.

RESULTS Of the 113 patients in the sample, groups receiving PEEK and titanium implants were closely matched at 57 and 56 patients, respectively. Cumulatively, 156 cages were inserted and recombinant human bone morphogenetic protein– 2 (rhBMP-2) was used in 38.1%. The average patient age was 60.4 years and average follow-up was 75.1 weeks. Subsidence in the titanium group in this study was less common than in the PEEK cage group. At early follow-up, groups had similar subsidence outcomes. Statistical significance was reached at the 8- to 12-week and 52-week follow-ups, demonstrating more subsidence in the PEEK cage group than the titanium cage group. rhBMP-2 usage was also highly correlated with higher subsidence rates at all 3 follow-up time points. Age was correlated with higher subsidence rates in univariate and multivariate analysis.

CONCLUSIONS Titanium cages were associated with lower subsidence rates than PEEK cages in this investigation. Usage of rhBMP-2 was also robustly associated with higher endplate subsidence. Each additional year of age correlated with an increased subsidence risk. Subsidence in LLIF is likely a response to a myriad of factors that include but are certainly not limited to cage material. Hence, the avoidance of titanium interbody implants secondary solely to concerns over a modulus of elasticity likely overlooks other variables of equal or greater importance.

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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, 2019

Common interbody graft options for anterior cervical discectomy and fusion (ACDF) include structural allograft and polyetheretherketone (PEEK). PEEK has gained popularity due to its radiolucency and its elastic modulus, which is similar to that of bone. The authors sought to compare the rates of pseudarthrosis, a lack of solid bone growth across the disc space, and the need for revision surgery with the use of grafts made of allogenic bone versus PEEK.

METHODS The authors retrospectively reviewed 127 cases in which patients had undergone a 1-level ACDF followed by at least 1 year of radiographic follow-up. Data on age, sex, body mass index, tobacco use, pseudarthrosis, and the reoperation rate for pseudarthrosis were collected. These data were analyzed by performing a Pearson’s chi-square test.

RESULTS Of 127 patients, 56 had received PEEK implants and 71 had received allografts. Forty-six of the PEEK implants (82%) were stand-alone devices. There were no significant differences between the 2 treatment groups with respect to patient age, sex, or body mass index. Twenty-nine (52%) of 56 patients with PEEK implants demonstrated radiographic evidence of pseudarthrosis, compared to 7 (10%) of 71 patients with structural allografts (p < 0.001, OR 9.82; 95% CI 3.836–25.139). Seven patients with PEEK implants required reoperation for pseudarthrosis, compared to 1 patient with an allograft (p = 0.01, OR 10.00; 95% CI 1.192–83.884). There was no significant difference in tobacco use between the PEEK and allograft groups (p = 0.586).

CONCLUSIONS The results of this study demonstrate that the use of PEEK devices in 1-level ACDF is associated with a significantly higher rate of radiographically demonstrated pseudarthrosis and need for revision surgery compared with the use of allografts. Surgeons should be aware of this when deciding on interbody graft options, and reimbursement policies should reflect these discrepancies.

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