Systematic ultrastructural analyses of meningeal and parenchymal vessels of the central nervous system

The direct endothelial contact with adjacent astrocytic end-feet is believed to establish blood-brain barrier (BBB) typical characteristics in endothelial cells of the central nervous system (CNS). However, this contact is only present in capillary vessels of the brain parenchyma and absent in larger veins, arteries and vessels within the meninges. To investigate a potential impact of direct endothelial interactions with adjacent astrocytic end-feet on the molecular tight junction (TJ) composition and ultrastructure, we performed a systematic analysis of endothelial cell contacts within the vascular tree of parenchymal and leptomeningeal vessels. Immunofluorescence labeling for claudin-3, claudin-5, zonula occludens-1 and occludin was used to compare the molecular composition, without showing significant differences in their distribution along the vascular tree of parenchymal and leptomeningeal vessels. Furthermore, electron microscopy in combination with quantitative analyses was performed to investigate the endothelial ultrastructure revealing significant differences within the length of endothelial overlaps between the different vessel types. Here, parenchymal arteries exhibit noticeably longer cell contacts compared to capillaries, which could not be observed in leptomeningeal vessels. It was also observed that arterial vessels regularly contain a higher density of endothelial vesicles throughout the parenchyma and meninges as a sign for transendothelial traffic. Hence, endothelial expression of blood-brain barrier typical TJs is not limited to capillary vessels with an intimate contact to surrounding astrocytes, but is also observed in arteries and veins of the brain parenchyma as well as the meninges, the latter of which are lacking a direct astrocyte-endothelial interaction. These vessel-specific characteristics can now be used to address and compare alterations of the BBB in different settings of CNS pathologies.:Table of Content 1. INTRODUCTION 4 1.1 THE BLOOD-BRAIN BARRIER 4 1.2 HISTORY 5 1.3 STRUCTURE AND COMPOSITION 6 1.4 THE ROLE OF THE MICROENVIRONMENT 8 1.4.1 ASTROCYTES 8 1.4.2 PERICYTES 9 1.5 BLOOD BRAIN BARRIER FUNCTION 10 1.5.1 PHYSIOLOGIC CONDITIONS 10 1. 5.2 PATHOLOGIC CONDITIONS 11 2. OPEN QUESTIONS AND SCIENTIFIC APPROACH 12 3. PUBLICATIONS 13 3.1 DIFFERENT SEGMENTS OF THE CEREBRAL VASCULATURE REVEAL SPECIFIC ENDOTHELIAL SPECIFICATIONS, WHILE TIGHT JUNCTION PROTEINS APPEAR EQUALLY DISTRIBUTED 13 3.2 THE BLOOD-BRAIN BARRIER 28 4. SUMMARY 40 5. REFERENCES 43 6. PROOF OF SIGNIFICANT CONTRIBUTION 48 7. DECLARATION OF ACADEMIC HONESTY 49 8. ACKNOWLEDGMENT 50 9. CURRICULUM VITAE 5

Significant Improvement in Shoulder Function and Pain in Patients Following Biologic Augmentation of Revision Arthroscopic Rotator Cuff Repair Using an Autologous Fibrin Scaffold and Bone Marrow Aspirate Derived From the Proximal Humerus

Purpose To clinically evaluate patients who underwent a biologic augmentation technique in revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated stem cells isolated from bone marrow aspirate (BMA) obtained from the proximal humerus. Methods This is a retrospective review of prospectively collected data from patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and BMA obtained from the proximal humerus between 2014 and 2015. Minimum follow-up was 12 months. Outcome measures were collected preoperatively and postoperatively including range of motion as well as American Shoulder and Elbow Surgeons Shoulder Form, Simple Shoulder Test, single assessment numeric evaluation, and visual analog score. In addition, BMA samples of each patient were assessed for the number of nucleated cells and colony-forming units. Regression analysis was performed to investigate whether the number of nucleated cells and colony-forming units had an influence on outcome and failure. Results Ten patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated BMA obtained from the proximal humerus between 2014 and 2015 were included. The mean follow-up time was 30.7 (range: 12-49) months. Four patients were revised at final follow-up. Postoperative clinical scores improved significantly: American Shoulder and Elbow Surgeons (28.1 ± 5.4 to 60.9 ± 9.0; P < .01), single assessment numeric evaluation (6.6 ± 2.3 to 65.1 ± 10.9; P < .01), visual analog scale (7.2 ± 0.9 to 3.1 ± 0.9; P < .01), and Simple Shoulder Test (1.6 ± 0.5 to 10.3 ± 5.7; P < .01). Postoperative range of motion increased significantly with regard to flexion (97.0 ± 13.6 to 151.0 ± 12.2; P < .01) and abduction (88.0 ± 14.0 to 134.0 ± 15.1; P = .038) but not with external rotation (38.0 ± 5.7 to 50.5 ± 6.5; P = .16). Less pain was correlated to an increased number of nucleated cells (P = .026); however, there was no correlation between failure rate and number of nucleated cells (P = .430). Conclusions Patients who underwent biologic augmentation of revision arthroscopic rotator cuff repair using an autologous fibrin scaffold and concentrated BMA demonstrated a significant improvement in shoulder function along with reduction of pain. However, the overall revision rate for this procedure was 40%. Level of Evidence Level IV, therapeutic case series

Systematic ultrastructural analyses of meningeal and parenchymal vessels of the central nervous system

The direct endothelial contact with adjacent astrocytic end-feet is believed to establish blood-brain barrier (BBB) typical characteristics in endothelial cells of the central nervous system (CNS). However, this contact is only present in capillary vessels of the brain parenchyma and absent in larger veins, arteries and vessels within the meninges. To investigate a potential impact of direct endothelial interactions with adjacent astrocytic end-feet on the molecular tight junction (TJ) composition and ultrastructure, we performed a systematic analysis of endothelial cell contacts within the vascular tree of parenchymal and leptomeningeal vessels. Immunofluorescence labeling for claudin-3, claudin-5, zonula occludens-1 and occludin was used to compare the molecular composition, without showing significant differences in their distribution along the vascular tree of parenchymal and leptomeningeal vessels. Furthermore, electron microscopy in combination with quantitative analyses was performed to investigate the endothelial ultrastructure revealing significant differences within the length of endothelial overlaps between the different vessel types. Here, parenchymal arteries exhibit noticeably longer cell contacts compared to capillaries, which could not be observed in leptomeningeal vessels. It was also observed that arterial vessels regularly contain a higher density of endothelial vesicles throughout the parenchyma and meninges as a sign for transendothelial traffic. Hence, endothelial expression of blood-brain barrier typical TJs is not limited to capillary vessels with an intimate contact to surrounding astrocytes, but is also observed in arteries and veins of the brain parenchyma as well as the meninges, the latter of which are lacking a direct astrocyte-endothelial interaction. These vessel-specific characteristics can now be used to address and compare alterations of the BBB in different settings of CNS pathologies.:Table of Content 1. INTRODUCTION 4 1.1 THE BLOOD-BRAIN BARRIER 4 1.2 HISTORY 5 1.3 STRUCTURE AND COMPOSITION 6 1.4 THE ROLE OF THE MICROENVIRONMENT 8 1.4.1 ASTROCYTES 8 1.4.2 PERICYTES 9 1.5 BLOOD BRAIN BARRIER FUNCTION 10 1.5.1 PHYSIOLOGIC CONDITIONS 10 1. 5.2 PATHOLOGIC CONDITIONS 11 2. OPEN QUESTIONS AND SCIENTIFIC APPROACH 12 3. PUBLICATIONS 13 3.1 DIFFERENT SEGMENTS OF THE CEREBRAL VASCULATURE REVEAL SPECIFIC ENDOTHELIAL SPECIFICATIONS, WHILE TIGHT JUNCTION PROTEINS APPEAR EQUALLY DISTRIBUTED 13 3.2 THE BLOOD-BRAIN BARRIER 28 4. SUMMARY 40 5. REFERENCES 43 6. PROOF OF SIGNIFICANT CONTRIBUTION 48 7. DECLARATION OF ACADEMIC HONESTY 49 8. ACKNOWLEDGMENT 50 9. CURRICULUM VITAE 5

Biomechanical evaluation of an arthroscopic transosseous repair as a revision option for failed rotator cuff surgery

Abstract Background The number of revision rotator cuff cases is increasing. The literature is lacking guidance or biomechanical evaluation for fixation strength in a revision case scenario. Therefore, the aim of the study was to provide biomechanical data investigating primary fixation strength of a transosseous technique after anchor pullout failure of a single row reconstruction. It was hypothesized that an arthroscopic transosseous repair system as a procedure for rotator cuff revisions is providing equivalent stability compared to a primary single row suture anchor fixation due to change of fixation site. Methods Eight matched pairs (n = 16) of fresh frozen human shoulders were tested. The paired specimen shoulders were randomly divided into two repair groups (A single row and B primary transosseous repair). The potted specimens were mounted onto the Servohydraulic test system. Both groups were tested under cyclic loading followed by load to failure testing. Suture anchor repair shoulders (group A) that were tested to failure underwent a revision transosseous repair and were subsequently tested again using the same setup and protocol (group C). Results The mean native footprint areas did not show a significant difference between groups. The reconstructed footprint area showed a significantly greater coverage in favor of the transosseous repair. Ultimate load to failure of reconstructions with the primary anchor fixation (344.73 N ± 63.19) and the primary transosseous device (375.36 N ± 70.27) was not significantly higher compared to the revision repair (332.19 N ± 119.01 p = 0.45, p = 0.53). Conclusion The tested transosseous anchor device is a suitable option to widely used suture anchors, providing equivalent fixation properties even in a revision case scenario. Level of evidence Basic Science Study, Biomechanics

Dynamic Q-angle is increased in patients with chronic patellofemoral instability and correlates positively with femoral torsion

PURPOSE The purpose of the study was to evaluate the frontal gait patterns in patients with chronic patellofemoral instability compared to healthy controls. The hypothesis was that internal-rotation-adduction moment of the knee as altered dynamic Q-angle is evident in patients and correlates positively with increased femoral torsion. METHODS Thirty-five patients with symptomatic recurrent patellofemoral instability requiring surgical treatment were matched for average age, sex, and body mass index with 15 healthy controls (30 knees). Several clinical and radiographic measurements were taken from each participant: internal and external rotation (hipIR, hipER), Q-angle, tubercle sulcus angle (TS-angle), femoral antetorsion (femAT), tibial tubercle-trochlear groove (TT-TG) distance, and frontal leg axis. Additionally, three frontal gait patterns were defined and recorded: (1) internal-rotation-adduction moment of the knee during normal walking, (2) dynamic valgus of the knee, and (3) Trendelenburg's sign in a single-leg squat. Randomized videography was evaluated by three independent blinded observers. Statistical analysis was performed using regression models and comparisons of gait patterns and clinical and radiological measurements. Furthermore, observer reliability was correlated to gradings of radiological parameters. RESULTS Patients showed altered dynamic Q-angle gait pattern during normal walking (p < 0.001) compared to healthy controls (interrater kappa = 0.61), whereas highest observer agreement was reported if femAT was greater than 20° (kappa = 0.85). Logistic regression model revealed higher femAT (18.2° ± 12.5 versus 11.9° ± 7.0 (p = 0.004) as a significant variable, as well as lower TT-TG distance (23.6 mm ± 2.8 vs. 16.6 mm ± 4.9, p = 0.004) on evident dynamic Q-angle gait pattern. Dynamic valgus in a single-leg squat was observed significantly more often in patients (p < 0.001) compared to controls (interrater kappa = 0.7). However, besides the static measured Q-angle as the only significant variable on evident dynamic valgus pattern (13.6° ± 4.6 vs. 10.3° ± 5.2, p = 0.003), no radiological parameter was detected to correlate significantly with dynamic valgus and Trendelenburg's sign (n.s.). CONCLUSIONS Clinical detection of pathologic torsion and bony alignment may be difficult in patients with patellofemoral instability. The present study demonstrated that dynamic Q-angle gait pattern is significantly altered in patients with chronic patellofemoral instability compared to healthy controls. Moreover, dynamic Q-angle correlates positively with higher femoral torsion and negatively with higher TT-TG distance. Therefore, clinical and radiological assessment of maltorsion should be added to the standard diagnostic workup in cases of patellofemoral instability. LEVEL OF EVIDENCE Level II

Footprint coverage comparison between knotted and knotless techniques in a single-row rotator cuff repair: biomechanical analysis

Abstract Background The objective of this biomechanical study is to compare two variations of single-row knotless techniques (Knotless repair and Rip-stop Knotless repair) against a single-row double-loaded anchor (DL) repair, focused on evaluating contact pressure and contact area amongst three different single-row techniques for rotator cuff repairs. Methods A total of 24 fresh frozen human shoulders were tested. Specimens were randomly assigned into one of the three single-row (SR) repair groups: A Knotted single-row double-loaded anchor (DL) repair, a Knotless (K) repair, or a Knotless Rip-Stop (KRS) repair. The footprint was measured after complete detachment of the supraspinatus tendon from the greater tuberosity, introducing pressure sensors between bony footprint and detached rotator cuff, and finally reconstructing it. All specimens were mounted onto a servohydraulic test system to analyze contact variables at 0° and 30° of abduction with 0 N, 30 N and 50 N of tension. Results Groups did not differ significantly in their footprint sizes: DL group 359.75 ± 58.37 mm2, K group 386.5 ± 102.13 mm2, KRS group 415.87 ± 93.80 mm2 (p = 0.84); nor in bone mineral density: DL group 0.25 ± 0.14 g/cm2, K group 0.32 ± 0.19 g/cm2, KRS group 0.32 ± 0.13 g/cm2, (p = 0.75) or average age. The highest mean pressurized contact area measured for the K repair was 248.1 ± 50.9 mm2, which equals a reconstruction of 67.1 ± 19.3% at 0° abduction and a 50 N supraspinatus load. This reconstructed area was significantly greater compared with the DL repair 152.8 ± 73.1 mm2, reconstructing 42.0 ± 18.5% on average when under the same conditions (p = 0.04). The mean contact pressure did not significantly differ amongst groups (p = 1.0): DL group 30.8 ± 17.4 psi, K group 30.9 ± 17.4 psi and KRS group 30.0 ± 10.9 psi. Neither the 30° abduction angle nor the supraspinatus load had a significant influence on the contact pressure in our study. Conclusion Both single-row knotless techniques resulted in significantly higher footprint reconstruction, providing larger contact area and a more uniform pressure distribution when compared with the single-row Knotted techniques. The mean contact pressure did not differ among groups significantly. These knotless techniques may be an alternative if the surgeon decides to perform a single-row rotator cuff repair. Level of evidence Basic Science Study, Biomechanics

The Glenolabral Articular Disruption Lesion Is a Biomechanical Risk Factor for Recurrent Shoulder Instability

PURPOSE: To investigate the biomechanical effect of a glenolabral articular disruption (GLAD) lesion on glenohumeral laxity. METHODS: Human cadaveric glenoids (n = 10) were excised of soft tissue, including the labrum to focus on the biomechanical effects of osteochondral surfaces. Glenohumeral dislocations were performed in a robotic test setup, while displacement forces and three-dimensional morphometric properties were measured. The stability ratio (SR), a biomechanical characteristic for glenohumeral stability, was used as an outcome parameter, as well as the path of least resistance, determined by a hybrid robot displacement. The impacts of chondral and bony defects were analyzed related to the intact glenoid. Statistical comparison of the defect states on SR and the path of least resistance was performed using repeated-measures ANOVA and Tukey’s post hoc test for multiple comparisons (P < .05). The relationship between concavity depth and SR was approximated in a nonlinear regression. RESULTS: The initial SR of the intact glenoid (28.3 ± 7.8%) decreased significantly by 4.7 ± 3% in case of a chondral defect (P = .002). An additional loss of 3.2 ± 2.3% was provoked by a 20% bony defect (P = .004). The path of least resistance was deflected significantly more inferiorly by a GLAD lesion (2.9 ± 1.8°, P = .002) and even more by a bony defect (2.5 ± 2.9°, P = .002). The nonlinear regression with concavity depth as predictor for the SR resulted in a high correlation coefficient (r = .81). CONCLUSIONS: Chondral integrity is an important contributor to the SR. Chondral defects as present in GLAD lesions may cause increased laxity, influence the humeral track on the glenoid during dislocation, and represent a biomechanical risk factor for a recurrent instability

Open subpectoral biceps tenodesis in patients over 65 does not result in an increased rate of complications

Abstract Background Long head biceps tendon pathology is a common cause of anterior shoulder pain and is often associated with other shoulder conditions, such as rotator cuff tears and osteoarthritis. It is well accepted that older patients are at increased risk for major and minor peri- and postoperative complications. The purpose of this study is to investigate patients over 65 years old who underwent subpectoral biceps tenodesis and compare the complication rates of this group to those of patients younger than 65 years old. The hypothesis is, that there would be no difference in complication rates and that clinical outcome scores for patients over 65 were satisfying and showed improvements over time. Methods There were 337 patients who underwent open subpectoral biceps tenodesis, between January 2005 and June 2015, 23 were identified as being over the age of 65 with a minimum follow up of 12 months. All patients over the age of 65 were evaluated pre- and postoperatively using Simple Shoulder Test (SST), American Shoulder and Elbow Surgeons (ASES), Constant-Murley (CM) and Single Assessment Numeric Evaluation (SANE). Intraoperative and postoperative adverse events (fracture, infection, wound opening, rupture/failure and neurovascular injuries) related to the tenodesis procedure and to the surgery itself were collected from all 337 patients in a routine postoperative follow-up. Results The under 65 group (range 27–64 years) at an average follow up (FU) of 30 months (range 12–91 months) showed a 5.4% (17 out of 314) post-operative complication rate related to the subpectoral tenodesis, whereas the group over 65 (range 65–77 years) at an average follow up of 33 months (range 12–79 months) showed an 8.7% (2 out of 23) complication rate. Conclusion This study demonstrates that in patients over the age of 65, biceps tenodesis is a successful procedure when performed for biceps tendinopathy and concomitantly with other surgical procedures of the shoulder, and does not result in an increased rate of complications when compared to a group of patients under the age of 65

Glenoid concavity has a higher impact on shoulder stability than the size of a bony defect

Purpose!#!Surgical treatment of shoulder instability caused by anterior glenoid bone loss is based on a critical threshold of the defect size. Recent studies indicate that the glenoid concavity is essential for glenohumeral stability. However, biomechanical proof of this principle is lacking. The aim of this study was to evaluate whether glenoid concavity allows a more precise assessment of glenohumeral stability than the defect size alone.!##!Methods!#!The stability ratio (SR) is a biomechanical estimate of glenohumeral stability. It is defined as the maximum dislocating force the joint can resist related to a medial compression force. This ratio was determined for 17 human cadaveric glenoids in a robotic test setup depending on osteochondral concavity and anterior defect size. Bony defects were created gradually, and a 3D measuring arm was used for morphometric measurements. The influence of defect size and concavity on the SR was examined using linear models. In addition, the morphometrical-based bony shoulder stability ratio (BSSR) was evaluated to prove its suitability for estimation of glenohumeral stability independent of defect size.!##!Results!#!Glenoid concavity is a significant predictor for the SR, while the defect size provides minor informative value. The linear model featured a high goodness of fit with a determination coefficient of R!##!Conclusion!#!Glenoid concavity is a crucial factor for the SR. Independent of the defect size, the computable BSSR is a precise biomechanical estimate of the measured SR. The inclusion of glenoid concavity has the potential to influence clinical decision-making for an improved and personalised treatment of glenohumeral instability with anterior glenoid bone loss