Bone Allograft Pedicle Screw Augmentation: A Biomechanical Study.

STUDY DESIGN: We performed a comprehensive cadaveric biomechanical study to compare the fixation strength of primary screws, screws augmented with bone allograft, and screws augmented with polymethylmethacrylate cement. OBJECTIVE: To evaluate a novel technique for screw augmentation using morselized cortico-cancellous bone allograft to fill the widened screw track of failed pedicle screws. BACKGROUND: To date, there are no known biological methods available for failed pedicle screw augmentation or fixation. MATERIALS AND METHODS: Biomechanical tests were performed using 2 different testing modalities to quantify fixation strength including axial screw pullout and progressive cyclic displacement tests. RESULTS: Fifty vertebrae were instrumented with pedicle screws. Our study showed that bone allograft augmentation using the same diameter screw was noninferior to the fixation strength of the initial screw. In the axial pullout test, screws undergoing bone allograft repair failed at 25% lower loads compared with native screws, and screws augmented with cement showed approximately twice as much strength compared with native screws. In the cyclic displacement test, screws fixed with cement resisted loosening the best of all the groups tested. However, screws augmented with bone graft were found to have an equal strength to native screw purchase. our study did not find a correlation with bone mineral density as a predictor for failure in axial pullout or cyclic displacement tests. CONCLUSION: Bone allograft augmentation for pedicle screw fixation was noninferior to the initial screw purchase in this biomechanical study. This bone allograft technique is a viable option for screw fixation in the revision setting when there is significant bone loss in the screw track.

Lumbar spine segmentation in MR images: a dataset and a public benchmark.

This paper presents a large publicly available multi-center lumbar spine magnetic resonance imaging (MRI) dataset with reference segmentations of vertebrae, intervertebral discs (IVDs), and spinal canal. The dataset includes 447 sagittal T1 and T2 MRI series from 218 patients with a history of low back pain and was collected from four different hospitals. An iterative data annotation approach was used by training a segmentation algorithm on a small part of the dataset, enabling semi-automatic segmentation of the remaining images. The algorithm provided an initial segmentation, which was subsequently reviewed, manually corrected, and added to the training data. We provide reference performance values for this baseline algorithm and nnU-Net, which performed comparably. Performance values were computed on a sequestered set of 39 studies with 97 series, which were additionally used to set up a continuous segmentation challenge that allows for a fair comparison of different segmentation algorithms. This study may encourage wider collaboration in the field of spine segmentation and improve the diagnostic value of lumbar spine MRI.

MRI image features with an evident relation to low back pain: a narrative review.

PURPOSE: Low back pain (LBP) is one of the most prevalent health condition worldwide and responsible for the most years lived with disability, yet the etiology is often unknown. Magnetic resonance imaging (MRI) is frequently used for treatment decision even though it is often inconclusive. There are many different image features that could relate to low back pain. Conversely, multiple etiologies do relate to spinal degeneration but do not actually cause the perceived pain. This narrative review provides an overview of all possible relevant features visible on MRI images and determines their relation to LBP. METHODS: We conducted a separate literature search per image feature. All included studies were scored using the GRADE guidelines. Based on the reported results per feature an evidence agreement (EA) score was provided, enabling us to compare the collected evidence of separate image features. The various relations between MRI features and their associated pain mechanisms were evaluated to provide a list of features that are related to LBP. RESULTS: All searches combined generated a total of 4472 hits of which 31 articles were included. Features were divided into five different categories:'discogenic', 'neuropathic','osseous', 'facetogenic', and'paraspinal', and discussed separately. CONCLUSION: Our research suggests that type I Modic changes, disc degeneration, endplate defects, disc herniation, spinal canal stenosis, nerve compression, and muscle fat infiltration have the highest probability to be related to LBP. These can be used to improve clinical decision-making for patients with LBP based on MRI.

Targeting self-efficacy more important than dysfunctional behavioral cognitions in patients with longstanding chronic low back pain; a longitudinal study.

BACKGROUND: Multidisciplinary pain management programs based on cognitive behavioral training (CBT) principles have been shown moderately effective in improving daily functioning in patients with chronic low back pain (CLBP). To optimize health-related outcomes as daily functioning, a clear understanding of the working mechanisms of these programs is warranted. Being confident to achieve a desired outcome, i.e. self-efficacy, is suggested to be a more potent determinant for beneficial treatment outcomes than restructuring the patient's dysfunctional behavioral cognitions (pain catastrophizing and fear of movement [FoM]), but the evidence is scarce. The objective of this study was twofold: 1) to determine whether a two-week pain management program resulted in post-treatment improvements in self-efficacy and decreased dysfunctional behavioral cognitions in patients with CLBP, and 2) to examine the unique contribution of self-efficacy to improvement in post-treatment disability. METHODS: A secondary analysis of an historical cohort study was performed, including 524 patients (59% females). PRIMARY OUTCOME: functional status (Oswestry Disability Index v2.1a). SECONDARY OUTCOMES: catastrophizing (Pain Catastrophizing Scale), FoM (Tampa Scale for Kinesiophobia), and self-efficacy (Pain Self-Efficacy Questionnaire). ASSESSMENTS: pre-, post-treatment, 1, and 12-months follow-up. Paired Student's t-tests were applied and clinical relevancy of improvements was described using minimal clinical important changes. Adjusted multivariate linear regression analyses were performed to explore the unique contribution of self-efficacy. RESULTS: The mean age of patients was 46 (SD = 9.5) years and they had longstanding CLBP (mean 12.5 [SD = 10.8] years). Mean functional status, self-efficacy, and dysfunctional behavioral cognitions improved significantly at post-treatment, with improvements maintained at 12 months follow-up. Post-treatment relevant improvements in self-efficacy and dysfunctional behavioral cognitions ranged from 62.4% (FoM) to 68.7% (self-efficacy). Post-treatment self-efficacy improved the model explaining post-treatment functional disability (basic model R2 = 0.49, F(6,517) = 83.67, p < 0.001; final model R2 = 0.57, F(8,515) = 85.20, p < 0.001). This was further substantiated by the relative contribution (standardized betas) of self-efficacy: 5.67 times more than catastrophizing and 9.75 times more than FoM. CONCLUSIONS: Targeting self-efficacy contributes to fast improvement in functional status for selected and motivated patients with persistent CLBP. In pain management programs and (online) self-management programs for CLBP, targeting patients' self-efficacy should have a prominent place.

One-step surgical procedure for the treatment of osteochondral defects with adipose-derived stem cells in a caprine knee defect: a pilot study.

Regenerative therapies offer attractive alternatives for the treatment of osteochondral defects. Adipose-derived stromal vascular fraction (SVF) cells allow the development of one-step surgical procedures by their abundant availability and high frequency. In this pilot study we evaluated the in vivo safety, feasibility, and efficacy of this concept using scaffolds seeded with freshly isolated (SVF) or cultured adipose stem cells (ASCs), and compared these to their acellular counterparts. Osteochondral defects were created in medial condyles and trochlear grooves in knees of eight goats. Defects were filled with acellular collagen I/III scaffolds or scaffolds seeded with SVF cells or cultured ASCs. Osteochondral regeneration was evaluated after 1 and 4 months by macroscopy, immunohistochemistry, biomechanical analysis, microCT analysis, and biochemistry. After 1 month, no adverse effects were noted. Microscopic, but not macroscopic evaluation showed considerable yet not significant differences, with cell-loaded constructs showing more extensive regeneration. After 4 months, acellular constructs displayed increased regeneration, however, to a lesser degree than cell-treated constructs. The latter exhibited more extensive collagen type II, hyaline-like cartilage, and higher elastic moduli, and their glycosaminoglycan content in the cartilaginous layer better approached native tissue values. Moreover, their defect regions contained higher levels of regenerated, mature subchondral bone with more intense collagen type I staining. SVF cells tended to perform best on all parameters. In summary, this pilot study demonstrated the preclinical safety and feasibility of a one-step surgical procedure for osteochondral defect regeneration. Similar regeneration was found between freshly isolated SVF cells and cultured ASCs. Larger studies with longer follow-up are required to substantiate these findings.

Reaming debris as a novel source of autologous bone to enhance healing of bone defects.

Reaming debris is formed when bone defects are stabilized with an intramedullary nail, and contains viable osteoblast-like cells and growth factors, and might thus act as a natural osteoinductive scaffold. The advantage of using reaming debris over stem cells or autologous bone for healing bone defects is that no extra surgery is needed to obtain the material. To assess the clinical feasibility of using reaming debris to enhance bone healing, we investigated whether reaming debris enhances the healing rate of a bone defect in sheep tibia, compared to an empty gap. As golden standard the defect was filled with iliac crest bone. Bones treated with iliac crest bone and reaming debris showed larger callus volume, increased bone volume, and decreased cartilage volume in the fracture gap, and increased torsional toughness compared to the empty gap group at 3 weeks postoperative. In addition, bones treated with reaming debris showed increased torsional stiffness at 6 weeks postoperatively compared to the empty defect group, while bending stiffness was marginally increased. These results indicate that reaming debris could serve as an excellent alternative to iliac crest bone for speeding up the healing process in bone defects that are treated with an intramedullary nail.

The use of poly(L-lactide-co-caprolactone) as a scaffold for adipose stem cells in bone tissue engineering: application in a spinal fusion model.

Since the early 1990s, tissue engineering has been heralded as a strategy that may solve problems associated with bone grafting procedures. The original concept of growing bone in the laboratory, however, has proven illusive due to biological, logistic, and regulatory problems. Fat-derived stem cells and synthetic polymers open new, more practicable routes for bone tissue engineering. In this paper, we highlight the potential of poly(L-lactide-co-caprolactone) (PLCL) to serve as a radiolucent scaffold in bone tissue engineering. It appears that PLCL quickly and preferentially binds adipose stem cells (ASCs), which proliferate rapidly and eventually differentiate into the osteogenic phenotype. An in vivo spinal fusion study in a goat model provides a preclinical proof-of-concept for a one-step surgical procedure with ASCs in bone tissue engineering.

Rapid attachment of adipose stromal cells on resorbable polymeric scaffolds facilitates the one-step surgical procedure for cartilage and bone tissue engineering purposes.

The stromal vascular fraction (SVF) of adipose tissue provides an abundant source of mesenchymal stem cells. For clinical application, it would be beneficial to establish treatments in which SVF is obtained, seeded onto a scaffold, and returned into the patient within a single surgical procedure. In this study, we evaluated the suitability of both a macroporous poly(L-lactide-co-caprolactone) and a porous collagen type I/III scaffold for this purpose. Surprisingly, cell attachment was rapid (∼10 min) and sequestered the majority of adipose stem cells, as deduced from colony-forming unit assays. Proliferation occurred in both polymeric scaffolds. Upon chondrogenic induction, up-regulation of chondrogenic genes, production of glycosaminoglycans, and accumulation of collagen type II was observed, indicating differentiation of scaffold-attached SVF cells along the chondrogenic lineage. Osteogenic differentiation was achieved in both scaffold types, as visualized by up-regulation of osteogenic genes, increase of alkaline phosphatase production over time, and accumulation of bone sialoprotein and osteonectin. In conclusion, this study identifies both poly(L-lactide-co-caprolactone) and collagen type I/III as promising scaffold materials for rapid attachment of adipose stem cell-like (stromal) cells, enhancing the development of one-step surgical concepts for cartilage and bone tissue engineering.

Osteogenic differentiation strategies for adipose-derived mesenchymal stem cells.

Adipose stem cell preparations, either obtained as a freshly isolated so-called stromal vascular fraction (SVF) or as cells cultured to homogeneity and then referred to as adipose stem cells (ASCs), have found widespread use in a broad variety of studies on tissue engineering and regenerative medicine applications, including bone repair.For newcomers within the field, but also for established research laboratories having up to 10 years of expertise in this research area, it may be convenient to strive for, and use consensus protocols (1) for studying the osteogenic differentiation potential of ASC preparations in vitro, and (2) for osteogenic induction regimes for in vivo implementation. To assist in achieving this goal, this chapter describes various step-by-step osteogenic differentiation protocols for adipose-derived stem cell populations (SVF as well as ASCs) currently applied within our laboratory, with particular emphasis on protocols aimed at intra-operative use. The protocols describe the use of inducing compounds, including the bone morphogenetic proteins (BMPs), 1,25-dihydroxyvitamin-D3, and polyamines, as well as methods and parameters for evaluating the level of differentiation achieved.We would appreciate receiving feedback on the protocols described; this will facilitate the development of consensus protocols, which in turn will allow better comparison of data sets generated by different research groups. This continuing standardization, which might be reported on at international meetings like those of IFATS ( http://www.IFATS.org ), might be of benefit for the whole ASC research community.

Caprine articular, meniscus and intervertebral disc cartilage: an integral analysis of collagen network and chondrocytes.

Cartilage is a tissue with only limited reparative capacities. A small part of its volume is composed of cells, the remaining part being the hydrated extracellular matrix (ECM) with collagens and proteoglycans as its main constituents. The functioning of cartilage depends heavily on its ECM. Although it is known that the various (fibro)cartilaginous tissues (articular cartilage, annulus fibrosus, nucleus pulposus, and meniscus) differ from one each other with respect to their molecular make-up, remarkable little quantitative information is available with respect to its biochemical constituents, such as collagen content, or the various posttranslational modifications of collagen. Furthermore, we have noticed that tissue-engineering strategies to replace cartilaginous tissues pay in general little attention to the biochemical differences of the tissues or the phenotypical differences of the (fibro)chondrocytes under consideration. The goal of this paper is therefore to provide quantitative biochemical data from these tissues as a reference for further studies. We have chosen the goat as the source of these tissues, as this animal is widely accepted as an animal model in orthopaedic studies, e.g. in the field of cartilage degeneration and tissue engineering. Furthermore, we provide data on mRNA levels (from genes encoding proteins/enzymes involved in the synthesis and degradation of the ECM) from (fibro)chondrocytes that are freshly isolated from these tissues and from the same (fibro)chondrocytes that are cultured for 18 days in alginate beads. Expression levels of genes involved in the cross-linking of collagen were different between cells isolated from various cartilaginous tissues. This opens the possibility to include more markers than the commonly used chondrogenic markers type II collagen and aggrecan for cartilage tissue-engineering applications.

Reproducible long-term disc degeneration in a large animal model.

STUDY DESIGN: Twelve goats were chemically degenerated and the development of the degenerative signs was followed for 26 weeks to evaluate the progression of the induced degeneration. The results were also compared with a previous study to determine the reproducibility. OBJECTIVES: The purpose of this study was determine whether this Chondroitinase ABC (CABC) induced goat model is reproducible and to study the development of the degeneration in time up to 26 weeks. SUMMARY OF BACKGROUND DATA: Injecting CABC into goat intervertebral discs results in mild disc degeneration after 12 weeks. Spontaneous recovery or leveling off of the degeneration has been reported before and is relevant when the goat model is used in regeneration studies. Reproducibility of the induced degeneration is relevant as well. METHODS: Twelve goats were used in this study. The development of degeneration was studied after the injection of 0.25 U/mL CABC intradiscally. The development of degenerative signs was studied after 18 (n = 6) and 26 (n = 6) weeks by means of radiograph, magnetic resonance imaging, macroscopic analysis, and histology and biochemical evaluation. The induced degeneration was compared with the results from a previous study, in which degeneration was induced similarly and analysis was performed after 12 weeks. RESULTS: The severity of the degenerative signs was mild and was consequently present in all parameters analyzed. When compared with the results after 12 weeks, the degeneration was similar in the present study. Spontaneous recovery was not observed up to 26 weeks. CONCLUSION: The injection with CABC in the intervertebral disc reproducibly results in mild disc degeneration in the goat. These findings corroborate the goat model as a suitable large animal model to evaluate mild disc degeneration and potential new therapies.