Sarcopenia Is an Independent Risk Factor for Proximal Junctional Disease Following Adult Spinal Deformity Surgery

Study Design: Retrospective cohort study. Objectives: Sarcopenia is a risk factor for medical complications following spine surgery. However, the role of sarcopenia as a risk factor for proximal junctional disease (PJD) remains undefined. This study evaluates whether sarcopenia is an independent predictor of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following adult spinal deformity (ASD) surgery. Methods: ASD patients who underwent thoracic spine to pelvis fusion with 2-year clinical and radiographic follow-up were reviewed for development of PJK and PJD. Average psoas cross-sectional area on preoperative axial computed tomography or magnetic resonance imaging at L4 was recorded. Previously described PJD risk factors were assessed for each patient, and multivariate linear regression was performed to identify independent risk factors for PJK and PJF. Disease-specific thresholds were calculated for sarcopenia based on psoas cross-sectional area. Results: Of 32 patients, PJK and PJF occurred in 20 (62.5%) and 12 (37.5%), respectively. Multivariate analysis demonstrated psoas cross-sectional area to be the most powerful independent predictor of PJK (P = .02) and PJF (P = .009). Setting ASD disease–specific psoas cross-sectional area thresholds of <12 cm2 in men and <8 cm2 in women resulted in a PJF rate of 69.2% for patients below these thresholds, relative to 15.8% for those above the thresholds. Conclusions: Sarcopenia is an independent, modifiable predictor of PJK and PJF, and is easily assessed on standard preoperative computed tomography or magnetic resonance imaging. Surgeons should include sarcopenia in preoperative risk assessment and consider added measures to avoid PJF in sarcopenic patients

Is the Use of Intraoperative 3D Navigation for Thoracolumbar Spine Surgery a Risk Factor for Post-Operative Infection?

Pedicle screw fixation is a technique used to provide rigid fixation in thoracolumbar spine surgery. Safe intraosseous placement of pedicle screws is necessary to provide optimal fixation as well as to avoid damage to adjacent anatomic structures. Despite the wide variety of techniques available, none thus far has been able to fully eliminate the risk of malpositioned screws. Intraoperative 3-dimensional navigation (I3DN) was developed to improve accuracy in the placement of pedicle screws. To our knowledge, no previous studies have investigated whether infection rates are higher with I3DN. A single-institution, retrospective study of patients age &gt; 18 undergoing thoracolumbar fusion and instrumentation was carried out and use of I3DN was recorded. The I3DN group had a significantly greater rate of return to the operating room for culture-positive incision and drainage (17 (4.1%) vs. 1 (0.6%), p = 0.025). In multivariate analysis, the use of I3DM did not reach significance with an OR of 6.49 (0.84&ndash;50.02, p = 0.073). Post-operative infections are multifactorial and potential infection risks associated with I3DN need to be weighed against the safety benefits of improved accuracy of pedicle screw positioning

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

Apoptosis Resistance and PKC Signaling: Distinguishing Features of High and Low Metastatic Cells12

The complexity of the process of metastasis is widely recognized. We report herein on a recurrent feature of high compared to low metastatic cells that is linked to their ability to survive early after their arrival at secondary sites. Using novel fluorescent-based imaging strategies that assess tumor cell interaction with the lung microenvironment, we have determined that most high and low metastatic cells can be distinguished within 6 hours of their arrival in the lung and further that this difference is defined by the ability of high metastatic cells to resist apoptosis at the secondary site. Despite the complexity of the metastatic cascade, the performance of cells during this critical window is highly defining of their metastatic proclivity. To explore mechanisms, we next evaluated biochemical pathways that may be linked to this survival phenotype in highly metastatic cells. Interestingly, we found no association between the Akt survival pathway and this metastatic phenotype. Of all pathways examined, only protein kinase C (PKC) activation was significantly linked to survival of highly metastatic cells. These data provide a conceptual understanding of a defining difference between high and low metastatic cells. The connection to PKC activation may provide a biologic rationale for the use of PKC inhibition in the prevention of metastatic progression

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

Efficacy, Cost, and Complications of Demineralized Bone Matrix in Instrumented Lumbar Fusion: Comparison With rhBMP-2.

Study designRetrospective cohort study.ObjectivesTo evaluate demineralized bone matrix as an adjunct for instrumented lumbar spine fusion compared with recombinant human bone morphogenetic protein-2 (rhBMP-2).MethodsClinical and radiographic review was performed of 43 patients with degenerative spine disease treated with posterolateral spinal fusion with or without posterior or transforaminal lumbar interbody fusion. Final analysis included sixteen patients treated with demineralized bone matrix (DBM; Accell Evo3, SeaSpine) compared with a retrospective matched group of 21 patients treated with rhBMP-2 (rhBMP-2, Infuse, Medtronic). All patients were followed for 24 months. Fusion was evaluated by computed tomography and/or x-ray. Clinical outcomes included visual analogue scale (VAS), Oswestry Disability Index (ODI), and Short Form 12 (SF-12).ResultsOverall fusion rate, including posterolateral and/or interbody fusion, was 100% for both groups, though the fusion rates in the posterolateral space alone were 93.5% and 100% for the DBM and rhBMP-2 groups, respectively. Clinical outcomes were similar between groups, with the DBM group showing greater improvement in ODI. The rhBMP-2 group showed higher rates of radiographic complications with 7 of 21 patients (33.3%) demonstrating either adjacent level fusion or ectopic bone formation, compared with zero in the DBM group. Average biologic cost per level was $1522 for DBM and$3505 for rhBMP-2.ConclusionsDBM and rhBMP-2 demonstrated similar radiographic and clinical outcomes in instrumented lumbar fusions. rhBMP-2 was associated with higher rates of radiographic complications and significantly higher costs

Sarcopenia Is an Independent Risk Factor for Proximal Junctional Disease Following Adult Spinal Deformity Surgery.

Study designRetrospective cohort study.ObjectivesSarcopenia is a risk factor for medical complications following spine surgery. However, the role of sarcopenia as a risk factor for proximal junctional disease (PJD) remains undefined. This study evaluates whether sarcopenia is an independent predictor of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following adult spinal deformity (ASD) surgery.MethodsASD patients who underwent thoracic spine to pelvis fusion with 2-year clinical and radiographic follow-up were reviewed for development of PJK and PJD. Average psoas cross-sectional area on preoperative axial computed tomography or magnetic resonance imaging at L4 was recorded. Previously described PJD risk factors were assessed for each patient, and multivariate linear regression was performed to identify independent risk factors for PJK and PJF. Disease-specific thresholds were calculated for sarcopenia based on psoas cross-sectional area.ResultsOf 32 patients, PJK and PJF occurred in 20 (62.5%) and 12 (37.5%), respectively. Multivariate analysis demonstrated psoas cross-sectional area to be the most powerful independent predictor of PJK (P = .02) and PJF (P = .009). Setting ASD disease-specific psoas cross-sectional area thresholds of &lt;12 cm2 in men and &lt;8 cm2 in women resulted in a PJF rate of 69.2% for patients below these thresholds, relative to 15.8% for those above the thresholds.ConclusionsSarcopenia is an independent, modifiable predictor of PJK and PJF, and is easily assessed on standard preoperative computed tomography or magnetic resonance imaging. Surgeons should include sarcopenia in preoperative risk assessment and consider added measures to avoid PJF in sarcopenic patients

Surgical Site Infection as a Risk Factor for Long-Term Instrumentation Failure in Patients with Spinal Deformity: A Retrospective Cohort Study

Surgical site infection (SSI) remains a complication of spine deformity surgery. Although fusion/instrumentation failure in the setting of SSI has been reported, few studies have investigated the relationship between these entities. We examine the relationship between early SSI and fusion/instrumentation failure after instrumented fusion in patients with thoracolumbar scoliosis. A retrospective review of a prospectively maintained case series for patients undergoing spine surgery between January 1, 2006, and October 3, 2017. Inclusion criteria included age ≥18 years and surgery performed for correction of thoracolumbar scoliosis. Data collected included various demographic, clinical, and operative variables. 532 patients met inclusion criteria, with 20 (4%) experiencing SSI. Diabetes mellitus was the only demographic risk factor for increased SSI (P = 0.026). Number of fused levels, blood volume loss, and operative time were similar between groups. Fusion/instrumentation failure occurred in 68 (13%) patients, 10 of whom (15%) had SSI, whereas of the 464 patients with no fusion/instrumentation failure, only 10 (2%) had SSI (P < 0.001). Of the 20 patients with SSI, 10 (50%) had fusion/instrumentation failure, whereas in the 512 patients with no infection, only 58 (11%) had fusion/instrumentation failure (P < 0.001). Patients with infection also experienced significantly shorter time to fusion/instrumentation failure (P = 0.025), higher need for revision surgery (P < 0.001), and shorter time to revision surgery (P = 0.012). Early SSI significantly increases the risk of fusion/instrumentation failure in patients with thoracolumbar scoliotic deformity, and it significantly shortens the time to failure. Patients with early SSI have a significantly higher likelihood of requiring revision surgery and after a significantly shorter time interval