Fibrin-genipin adhesive hydrogel for annulus fibrosus repair: performance evaluation with large animal organ culture, in situ biomechanics, and in vivo degradation tests.

Annulus fibrosus (AF) defects from annular tears, herniation, and discectomy procedures are associated with painful conditions and accelerated intervertebral disc (IVD) degeneration. Currently, no effective treatments exist to repair AF damage, restore IVD biomechanics and promote tissue regeneration. An injectable fibrin-genipin adhesive hydrogel (Fib-Gen) was evaluated for its performance repairing large AF defects in a bovine caudal IVD model using ex vivo organ culture and biomechanical testing of motion segments, and for its in vivo longevity and biocompatibility in a rat model by subcutaneous implantation. Fib-Gen sealed AF defects, prevented IVD height loss, and remained well-integrated with native AF tissue following approximately 14,000 cycles of compression in 6-day organ culture experiments. Fib-Gen repair also retained high viability of native AF cells near the repair site, reduced nitric oxide released to the media, and showed evidence of AF cell migration into the gel. Biomechanically, Fib-Gen fully restored compressive stiffness to intact levels validating organ culture findings. However, only partial restoration of tensile and torsional stiffness was obtained, suggesting opportunities to enhance this formulation. Subcutaneous implantation results, when compared with the literature, suggested Fib-Gen exhibited similar biocompatibility behaviour to fibrin alone but degraded much more slowly. We conclude that injectable Fib-Gen successfully sealed large AF defects, promoted functional restoration with improved motion segment biomechanics, and served as a biocompatible adhesive biomaterial that had greatly enhanced in vivo longevity compared to fibrin. Fib-Gen offers promise for AF repairs that may prevent painful conditions and accelerated degeneration of the IVD, and warrants further material development and evaluation.

Implementation of cloud computing in the German healthcare system.

With the advent of artificial intelligence and Big Data - projects, the necessity for a transition from analog medicine to modern-day solutions such as cloud computing becomes unavoidable. Even though this need is now common knowledge, the process is not always easy to start. Legislative changes, for example at the level of the European Union, are helping the respective healthcare systems to take the necessary steps. This article provides an overview of how a German university hospital is dealing with European data protection laws on the integration of cloud computing into everyday clinical practice. By describing our model approach, we aim to identify opportunities and possible pitfalls to sustainably influence digitization in Germany.

Monitoring the load on a telemeterised vertebral body replacement for a period of up to 65 months.

PURPOSE: To determine the postoperative temporal course of the forces acting on a vertebral body replacement (VBR) for two well reproducible activities. METHODS: A telemeterised VBR was implanted in five patients. It allows the measurement of six load components. Implant loads were measured in up to 28 measuring sessions for different activities, including standing and walking. RESULTS: The postoperative temporal course of the resultant implant forces measured during standing and walking was similar in each patient, but the patterns varied strongly from patient to patient. In one patient, the forces decreased in the first year and then increased in the following 4 years. In another patient, the forces increased in the first few months and then decreased. In a third patient, the forces varied only slightly in the postoperative time. In two patients, there was a strong drop of the implant force in the first two postoperative months. The force was on average approximately 100 N or 71% higher for walking than for standing. CONCLUSIONS: The strong force reduction in the first 2 months is most likely caused by implant subsidence, and the force reduction over a period of more than 6 months is most likely caused by fusion of the vertebrae adjacent to the VBR. The short-term force increase could be attributed to bone atrophy at the index level, and the long-term force increase could be attributed to an increase in the thoracic spine kyphosis angle.

Parameters influencing the outcome after total disc replacement at the lumbosacral junction. Part 1: misalignment of the vertebrae adjacent to a total disc replacement affects the facet joint and facet capsule forces in a probabilistic finite element analysis.

PURPOSE: After total disc replacement with a ball-and-socket joint, reduced range of motion and progression of facet joint degeneration at the index level have been described. The aim of the study was to test the hypothesis that misalignment of the vertebrae adjacent to the implant reduces range of motion and increases facet joint or capsule tensile forces. METHODS: A probabilistic finite element analysis was performed using a lumbosacral spine model with an artificial disc at level L5/S1. Misalignment of the L5 vertebra, the gap size of the facet joints, the transection of the posterior longitudinal ligament, and the spinal shape were varied. The model was loaded with pure moments. RESULTS: Misalignment of the L5 vertebra reduced the range of motion up to 2°. A 2-mm displacement of the L5 vertebra in the anterior direction already led to facet joint forces of approximately 240 N. Extension, lateral bending, and axial rotation caused maximum facet joint forces between 280 and 380 N, while flexion caused maximum forces of approximately 200 N. A 2-mm displacement in the posterior direction led to capsule forces of approximately 80 N. Additional moments increased the maximum facet capsule forces to values between 120 and 230 N. CONCLUSIONS: Misalignment of the vertebrae adjacent to an artificial disc strongly increases facet joint or capsule forces. It might, therefore, be an important reason for unsatisfactory clinical results. In an associated clinical study (Part 2), these findings are validated.

Loads on a vertebral body replacement during locomotion measured in vivo.

Walking is one of the most important activities in daily life, and walking exposes the spine to a high number of loading cycles. Little is known about the spinal loads during walking. Telemeterized spinal implants can provide data about their loading during different activities. The aim of this study was to measure the loads on a vertebral body replacement (VBR) during level and staircase walking and to determine the effects of walking speed and using walking aids. Telemeterized VBRs were implanted in five patients suffering from compression fractures of the L1 or L3 lumbar vertebral body. The implant allows measurements of three force and three moment components. The resultant force on the VBR was measured during level and staircase walking, when walking on a treadmill at different speeds, and when using a wheeled invalid walker or crutches. On average, the resultant force on the VBR for level walking was 171% of the value for standing. This force value increased to 265% of the standing force when ascending stairs and to 225% when descending stairs. Walking speed had a strong effect on the implant force. Using a walker during ambulation on level ground reduced the force on the implant to 62% of standing forces, whereas using two crutches had only a minor effect. Walking causes much higher forces on the VBR than standing. A strong force reduction can be achieved by using a walker.

Comparison of eight published static finite element models of the intact lumbar spine: predictive power of models improves when combined together.

Finite element (FE) model studies have made important contributions to our understanding of functional biomechanics of the lumbar spine. However, if a model is used to answer clinical and biomechanical questions over a certain population, their inherently large inter-subject variability has to be considered. Current FE model studies, however, generally account only for a single distinct spinal geometry with one set of material properties. This raises questions concerning their predictive power, their range of results and on their agreement with in vitro and in vivo values. Eight well-established FE models of the lumbar spine (L1-5) of different research centers around the globe were subjected to pure and combined loading modes and compared to in vitro and in vivo measurements for intervertebral rotations, disc pressures and facet joint forces. Under pure moment loading, the predicted L1-5 rotations of almost all models fell within the reported in vitro ranges, and their median values differed on average by only 2° for flexion-extension, 1° for lateral bending and 5° for axial rotation. Predicted median facet joint forces and disc pressures were also in good agreement with published median in vitro values. However, the ranges of predictions were larger and exceeded those reported in vitro, especially for the facet joint forces. For all combined loading modes, except for flexion, predicted median segmental intervertebral rotations and disc pressures were in good agreement with measured in vivo values. In light of high inter-subject variability, the generalization of results of a single model to a population remains a concern. This study demonstrated that the pooled median of individual model results, similar to a probabilistic approach, can be used as an improved predictive tool in order to estimate the response of the lumbar spine.

Correlation between back shape and spinal loads.

The purpose of this study was to determine the correlation between the back shape of the lumbar region and the spinal loads during activities performed in the sagittal plane. Measurements were performed in four subjects who had suffered from a compression fracture of a lumbar vertebral body which was treated with a telemeterized vertebral body replacement that is able to measure six load components in vivo. An Epionics SPINE measurement system was used to determine the lumbar lordosis angle. The relationship between the lordosis angle and the corresponding loads was quantified with the Spearman's rank correlation coefficient method. Measurements were performed during thirteen exercises in lying, standing or sitting. During upper body flexion, the force increased on average by approximately 285N and the lordosis angle decreased by 15°. The change of the force for elevating 30N in one hand was on average approximately 190N and for the lordosis angle 2°. Correlation coefficients greater than 0.6 were found for exercises that involved both large back shape and load changes, such as upper body flexion. A strong increase in spinal load can be associated with an increase or a decrease of the lordosis angle. Only for considerable changes of the lordosis angle in an upright body position was a strong correlation between lordosis angle and implant force found.