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Study Design. A retrospective study (level of evidence: level 4). Objective. To evaluate the radiographic outcomes after extreme lateral lumbar interbody fusion (XLIF) and oblique lateral lumbar interbody fusion (OLIF) procedures especially the effect of indirect decompression to the ligamentum flavum and to evaluate the effect of facet degeneration to the radiographic outcomes of these procedures. Summary of Background Data. Indirect decompression via lateral lumbar interbody fusion provides spinal canal area expansion. However, the effect to the ligamentum flavum area and thickness at the operated spinal level is unclear. Methods. Thirty-five patients (57 lumbar levels) underwent XLIF or OLIF with percutaneous pedicle screw fixation (PPS) without direct posterior decompression were retrospectively studied. Radiographic parameters including ligamentum flavum area (LFA), ligamentum flavum thickness (LFT), cross-sectional area (CSA) of thecal sac, posterior disc height, foraminal height, cage alignment, and facet degeneration were measured on magnetic resonance image (MRI). Cage position was assessed with plain radiography. Results. All of the radiographic parameters were significantly improved. Comparing pre- and postoperative value, mean LFA decreased from 78.9 ± 24.9 mm2 to 66.9 ± 26.8 mm2 (–14.2%; P-value < 0.00625). Mean right LFT decreased from 2.9 ± 0.9 mm to 2.3 ± 0.7 (–17.0%; P-value < 0.00625). Mean left LFT decreased from 3.3 ± 1.6 mm to 2.6 ± 0.9 mm (–17.6%; P-value < 0.00625). Mean CSA of thecal sac increased from 93.1 ± 43.0 mm2 to 127.3 ± 52.5 mm2 (50.8%; P-value < 0.00625). All radiographic outcomes were not significant difference between lumbar levels that have grade 0–1 and grade 2–3 or between grade 2 and grade 3 facet degeneration. Conclusion. Ligamentum flavum area and thickness were significantly reduced after lateral lumbar interbody fusion through both XLIF and OLIF. Unbuckling of the ligamentum flavum played an important role for improvement of spinal canal area after the indirect decompression. Level of Evidence: 4

This study confirmed the L4 level of the aortic bifurcation and iliac vein coalescence but also demonstrated substantial mobility of the great vessels with positioning. Supine magnetic resonance imaging will underestimate the proximity of the vessels to the intervertebral disc. Large interindividual variation in the location of vasculature was noted, emphasizing the importance of careful study of the location of the retroperitoneal vessels on a case-by-case basis.

Study Design Systematic review. Objective To compare laminoplasty versus laminectomy and fusion in patients with cervical myelopathy caused by OPLL. Methods A systematic review was conducted using PubMed/Medline, Cochrane database, and Google scholar of articles. Only comparative studies in humans were included. Studies involving cervical trauma/fracture, infection, and tumor were excluded. Results Of 157 citations initially analyzed, 4 studies ultimately met our inclusion criteria: one class of evidence (CoE) II prospective cohort study and three CoE III retrospective cohort studies. The prospective cohort study found no significant difference between laminoplasty and laminectomy and fusion in the recovery rate from myelopathy. One CoE III retrospective cohort study reported a significantly higher recovery rate following laminoplasty. Another CoE III retrospective cohort study reported a significantly higher recovery rate in the laminectomy and fusion group. One CoE II prospective cohort study and one CoE III retrospective cohort study found no significant difference in pain improvement between patients treated with laminoplasty versus patients treated with laminectomy and fusion. All four studies reported a higher incidence of C5 palsy following laminectomy and fusion than laminoplasty. One CoE II prospective cohort and one CoE III retrospective cohort reported that there was no significant difference in axial neck pain between the two procedures. One CoE III retrospective cohort study suggested that there was no significant difference between groups in OPLL progression. Conclusion Data from four comparative studies was not sufficient to support the superiority of laminoplasty or laminectomy and fusion in treating cervical myelopathy caused by OPLL.

P15, a synthetic 15 amino acid peptide, mimics the cell-binding domain within the alpha-1 chain of human collagen is being tested in clinical trials to determine if it enhances bone formation in spinal fusions. We hypothesize that covalent attachment of P15 to titanium implants may also serve to promote osseointegration. To test this hypothesis, we measured osteoblast and mesenchymal cell adhesion, proliferation, and maturation on P15 tethered to a titanium (Ti-P15) surface. P15 peptide was covalently bonded to titanium alloy surfaces and incubated with osteoblast like cells. Cell toxicity, adhesion, spreading, and differentiation was then evaluated. Real-time quantitative PCR, Western blot analysis, and fluorescent immunohistochemistry was performed to measure osteoblast gene expression and differentiation. There was no evidence of toxicity. Significant increases in early cell attachment, spreading, and proliferation were observed on the Ti-P15 surface. Increased filapodial attachments, a 2 integrin expression, and phosphorylated focal adhesion kinase immunostaining indicated activation of integrin signaling pathways. qRT-PCR analysis indicated there was significant increase in osteogenic differentiation markers in cells grown on Ti-P15 compared to control-Ti. Western blotting confirmed these findings. Surface modification of titanium with P15 significantly increased cell attachment, spreading, osteogenic gene expression, and differentiation. Results of this study suggest that Ti-P15 has the potential to safely enhance bone formation and promote osseointegration of titanium implants. ß

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Study Design Retrospective cohort study Objectives This study aimed to report the incidence and potential risk factors of polyetheretherketone (PEEK) cage subsidence following oblique lateral interbody fusion (OLIF) for lumbar degenerative diseases. We proposed also an algorithm to minimize subsidence following OLIF surgery. Methods The study included a retrospective cohort of 107 consecutive patients (48 men and 59 women; mean age, 67.4 years) who had received either single- or multi-level OLIF between 2012 and 2019. Patients were classified into subsidence and non-subsidence groups. PEEK cage subsidence was defined as any violation of either endplate from the computed tomography scan in both sagittal and coronal views. Preoperative variables such as age, sex, body mass index, bone mineral density (BMD) measured by preoperative dual-energy X-ray absorptiometry, smoking status, corticosteroid use, diagnosis, operative level, multifidus muscle cross-sectional area, and multifidus muscle fatty degeneration were collected. Age-related variables (height and length) were also documented. Univariate and multivariate logistic regression analyses were used to analyze the risk factors of subsidence. Results Of the 107 patients (137 levels), 50 (46.7%) met the subsidence criteria. Higher PEEK cage height had the strongest association with subsidence (OR = 9.59, P < .001). Other factors significantly associated with cage subsistence included age >60 years (OR = 3.15, P = .018), BMD <−2.5 (OR = 2.78, P = .006), and severe multifidus muscle fatty degeneration (OR = 1.97, P = .023). Conclusions Risk factors for subsidence in OLIF were age >60 years, BMD < −2.5, higher cage height, and severe multifidus muscle fatty degeneration. Patients who had subsidence had worse early (3 months) postoperative back and leg pain.

Object Lumbar degenerative spondylolisthesis (LDS) is common and has generally been characterized as a homogeneous disease entity in the literature and in clinical practice. Because disease variability has not been carefully characterized, stratification of treatment recommendations based on scientific evidence is currently lacking. In this study, the authors analyzed radiographic parameters of patients with LDS at the L4–5 level to better characterize this entity. Methods Demographic data were collected from 304 patients (200 women and 104 men) with LDS at the L4–5 level. Plain radiographs including anteroposterior, lateral, and flexion-extension lateral radiographs were analyzed for disc height, segmental angulation, segmental translation, and osteophyte formation. Correlations were sought between the variables of age, sex, disc height, segmental angulation, segmental translation, and osteophyte formation. Results The mean patient age was 63.8 years (range 40–86 years). The mean mid-disc height was 7 mm (range 0–14 mm) on the neutral lateral view. The mean angulation between the superior endplate of L-5 and the inferior endplate of L-4 was 6° of lordosis (range 13° of kyphosis to 23° lordosis) on the neutral lateral view. The mean angular change between flexion and extension lateral radiographs was 5° (range 0°–17°). The mean translation on the neutral lateral view was 6 mm (range 0–15 mm). The mean change in translational between flexion and extension was 2 mm (range 0–11 mm). Twenty patients (7%) exhibited spondylolisthesis only on the flexion view. A significant positive correlation was found between the change in angulation and the change in translation on flexion and extension views (ρ = 0.18, p = 0.001). No significant correlation was found between anterior osteophyte size and mobility with flexion-extension radiographs. Conclusions The wide range in all radiographic parameters for LDS confirms the heterogeneous nature of this condition and suggests that a grading system to subclassify LDS may be clinically useful. On flexion and extension radiographs, increased translational motion correlated with increased angular motion. Anterior osteophyte size was not found to be predictive of segmental stability. This data set should prove beneficial to those seeking to subcategorize LDS in the future.