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Objective: Lumbar interbody cage subsidence has a multifactorial etiology. Cage material, although well studied after transforaminal lumbar interbody fusion, has not been investigated as a contributing factor to subsidence after lateral lumbar interbody fusion (LLIF). In this study the authors compared rates of subsidence and reoperation after LLIF between polyetheretherketone (PEEK) and 3D-printed porous titanium (pTi) in an institutional propensity score-matched and cost analysis., Methods: This is a retrospective observational cohort analysis of adult patients who underwent LLIF with pTi versus PEEK between 2016 and 2020. Demographic, clinical, and radiographic characteristics were collected. Propensity scores were calculated and 1:1 matching without replacement of surgically treated levels was performed. The primary outcome of interest was subsidence. The Marchi subsidence grade was determined at the time of last follow-up. Chi-square or Fisher's exact tests were used to compare subsidence and reoperation rates between lumbar levels treated with PEEK versus pTi. Modeling and cost analysis were performed using TreeAge Pro Healthcare., Results: The authors identified a total of 192 patients; 137 underwent LLIF with PEEK (212 levels) and 55 had LLIF with pTi (97 levels). After propensity score matching, a total of 97 lumbar levels remained in each treatment group. After matching, there were no statistically significant differences between groups in baseline characteristics. Levels treated with pTi were significantly less likely to exhibit subsidence (any grade) compared to those treated with PEEK (8% vs 27%, p = 0.001). Five (5.2%) levels treated with PEEK required reoperation for subsidence, but only 1 (1.0%) level treated with pTi required reoperation for subsidence (p = 0.12). Given subsidence and revision rates experienced in the cohorts in this study, the pTi interbody device is economically superior to PEEK in a single-level LLIF as long as its cost is at least $1185.94 lower than that of PEEK., Conclusions: The pTi interbody device was associated with less subsidence, but statistically similar revision rates after LLIF. pTi is potentially a superior economic choice at this study's reported revision rate.

Introduction: Interbody fusion is commonly utilized for arthrodesis and stability among patients undergoing spine surgery. Over the last few decades, interbody device materials, such as titanium and polyetheretherketone (PEEK), have been replacing traditional autografts and allografts for interbody fusion. As such, with the exponential growth of bioengineering, a large variety cage surface technologies exist. Different combinations of cage component materials and surface modifications have been created to optimize interbody constructs for surgical use. This review aims to provide a comprehensive overview of common surface technologies, their performance in the clinical setting, and recent modifications and material combinations., Materials and Methods: We performed a comprehensive review of the literature on titanium and PEEK as medical devices between 1964 and 2021. We searched five major databases, resulting in 4974 records. Articles were screened for inclusion manually by two independent reviewers, resulting in 237 articles included for review., Conclusion: Interbody devices have rapidly evolved over the last few decades. Biomaterial and biomechanical modifications have allowed for continued design optimization. While titanium has a high osseointegrative capacity, it also has a high elastic modulus and is radio-opaque. PEEK, on the other hand, has a lower elastic modulus and is radiolucent, though PEEK has poor osseointegrative capacity. Surface modifications, material development advancements, and hybrid material devices have been utilized in search of an optimal spinal implant which maximizes the advantages and minimizes the disadvantages of each interbody material., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objective: Lumbar spondylolysis occurs in 5%-8% of adults. This study aimed to report clinical and radiographic outcomes of direct pars repair in adults with lumbar spondylolysis., Methods: We conducted a retrospective review of all patients treated for lumbar spondylolysis via open fracture reduction and direct pars repair with cannulated screws using a lag technique. Demographics, clinical presentation, perioperative and intraoperative imaging, and postoperative data were collected. We subsequently performed a systematic review to describe radiographic and clinical outcomes following direct pars repair., Results: Three patients were identified (mean age 40.3 years; range, 21-72 years; 2 male). All patients had bilateral L5 pars fractures treated via open, direct repair with cannulated screws. There were no intraoperative complications. Length of stay was <24 hours for each patient. All patients reported back/radicular symptom relief and returned to full-time manual labor by latest follow-up. Noncontrast lumbar computed tomography performed 14-20 months postoperatively confirmed that all patients had good bilateral screw placement without fracture. Two patients (21 and 28 years old at surgery) had evidence of fusion across fracture sites, while 1 patient exhibited radiolucency around the screws and no progression of spondylolisthesis. Additionally, we reviewed 8210 articles and included 15 in a systematic review of direct pars repair. Fusion rates were 67%-100%, with improved average Oswestry Disability Index and visual analog scale back pain scores by latest follow-up., Conclusions: Lumbar spondylolysis treatment with open fracture reduction and direct pars repair with cannulated screws in adults is safe and may result in mechanical back/radicular pain relief, even in the absence of radiographic fusion., (Copyright © 2022. Published by Elsevier Inc.)

Background: Standalone single and multilevel lateral lumbar interbody fusion (LLIF) have been increasingly applied to treat degenerative spinal conditions in a less invasive fashion. Graft subsidence following LLIF is a known complication and has been associated with poor bone mineral density (BMD). Previous research has demonstrated the utility of computed tomography (CT) Hounsfield units (HUs) as a surrogate for BMD. In the present study, we investigated the relationship between the CT HUs and subsidence and reoperation after standalone and multilevel LLIF., Methods: A prospectively maintained single-institution database was retrospectively reviewed for LLIF patients from 2017 to 2020, including single and multilevel standalone cases with and without supplemental posterior fixation. Data on demographics, graft parameters, BMD determined by dual-energy x-ray absorptiometry, preoperative mean segmental CT HUs, and postoperative subsidence and reoperation were collected. We used 36-in. standing radiographs to measure the preoperative global sagittal alignment and disc height and subsidence at last follow-up. Subsidence was classified using the Marchi grading system corresponding to disc height loss: grade 0, 0%-24%; grade I, 25%-49%; grade II, 50%-74%; and grade III, 75%-100%., Results: A total of 89 LLIF patients had met the study criteria, with a mean follow-up of 19.9 ± 13.9 months. Of the 54 patients who had undergone single-level LLIF, the mean segmental HUs were 152.0 ± 8.7 for 39 patients with grade 0 subsidence, 136.7 ± 10.4 for 9 with grade I subsidence, 133.9 ± 23.1 for 3 with grade II subsidence, and 119.9 ± 30.9 for 3 with grade III subsidence (P = 0.032). Of the 96 instrumented levels in the 35 patients who had undergone multilevel LLIF, 85, 9, 1, and 1 level had had grade 0, grade I, grade II, and grade III subsidence, with no differences in the HU levels. On multivariate logistic regression, increased CT HU levels were independently associated with a decreased risk of reoperation after both single-level and multilevel LLIF (odds ratio, 0.98; 95% confidence interval, 0.97-0.99; P = 0.044; and odds ratio, 0.97; 95% confidence interval, 0.94-0.99; P = 0.017, respectively). Overall, the BMD determined using dual-energy x-ray absorptiometry was not associated with graft subsidence or reoperation. Using a receiver operating characteristic curve to separate the patients who had and had not required reoperation, the threshold HU level determined for single-level and multilevel LLIF was 131.4 (sensitivity, 0.62; specificity 0.65) and 131.0 (sensitivity, 0.67; specificity, 0.63), respectively., Conclusions: Lower CT HUs were independently associated with an increased risk of graft subsidence after single-level LLIF. In addition, lower CT HUs significantly increased the risk of reoperation after both single and multilevel LLIF with a critical threshold of 131 HUs. The determination of the preoperative CT HUs might provide a more robust gauge of local bone quality and the likelihood of graft subsidence requiring reoperation following LLIF than overall BMD., (Copyright © 2022 Elsevier Inc. All rights reserved.)