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Background: Metacarpal shaft fractures are common and can be treated nonoperatively. Shortening, angulation, and rotational deformity are indications for surgical treatment. Various forms of treatment with advantages and disadvantages have been documented. The purpose of the study was to determine the stability of fracture fixation with intramedullary headless compression screws in two types of metacarpal shaft fractures and compare them to other common forms of rigid fixation: dorsal plating and lag screw fixation. It was hypothesized that headless compression screws would demonstrate a biomechanical stronger construct. Methods: Five matched paired hands (age 60.9 ± 4.6 years), utilizing non-thumb metacarpals, were used for comparative fixation in two fracture types created by an osteotomy. In transverse diaphyseal fractures, fixation by headless compression screws (n = 7) and plating (n = 8) were compared. In long oblique diaphyseal fractures, headless compression screws (n = 8) were compared with plating (n = 8) and lag screws (n = 7). Testing was performed using an MTS frame producing an apex dorsal, three point bending force. Peak load to failure and stiffness were calculated from the load-displacement curve generated. Results: For transverse fractures, headless compression screws had a significantly higher stiffness and peak load to failure, means 249.4 N/mm and 584.8 N, than plates, means 129.02 N/mm and 303.9 N (both p < 0.001). For long oblique fractures, stiffness and peak load to failure for headless compression screws were means 209 N/mm and 758.4 N, for plates 258.7 N/mm and 518.5 N, and for lag screws 172.18 N/mm and 234.11 N. There was significance in peak load to failure for headless compression screws vs plates (p = 0.023), headless compression screws vs lag screws (p < 0.001), and plates vs lag screws (p = 0.009). There was no significant difference in stiffness between groups. Conclusion: Intramedullary fixation of diaphyseal metacarpal fractures with a headless compression screw provides excellent biomechanical stability. Coupled with lower risks for adverse effects, headless compression screws may be a preferable option for those requiring rapid return to sport or work. Level of evidence: Basic Science Study, Biomechanics., Finanziert über die DEAL-Vereinbarung mit Wiley 2019-2022.

Background: Arthroscopic coracoplasty is a procedure for patients affected by subcoracoid impingement. To date, there is no consensus on how much of the coracoid can be resected with an arthroscopic burr without compromising its stability. Purpose: To determine the maximum amount of the coracoid that can be resected during arthroscopic coracoplasty without leading to coracoid fracture or avulsion of the conjoint tendon during simulated activities of daily living (ADLs). Study Design: Controlled laboratory study. Methods: A biomechanical cadaveric study was performed with 24 shoulders (15 male, 9 female; mean age, 81 ± 7.9 years). Specimens were randomized into 3 treatment groups: group A (native coracoid), group B (3-mm coracoplasty), and group C (5-mm coracoplasty). Coracoid anatomic measurements were documented before and after coracoplasty. The scapula was potted, and a traction force was applied through the conjoint tendon. The stiffness and load to failure (LTF) were determined for each specimen. Results: The mean coracoid thicknesses in groups A through C were 7.2, 7.7, and 7.8 mm, respectively, and the mean LTFs were 428 ± 127, 284 ± 77, and 159 ± 87 N, respectively. Compared with specimens in group A, a significantly lower LTF was seen in specimens in group B (P = .022) and group C (P < .001). Postoperatively, coracoids with a thickness ≥4 mm were able to withstand ADLs. Conclusion: While even a 3-mm coracoplasty caused significant weakening of the coracoid, the individual failure loads were higher than those of the predicted ADLs. A critical value of 4 mm of coracoid thickness should be preserved to ensure the stability of the coracoid process. Clinical Relevance: In correspondence with the findings of this study, careful preoperative planning should be used to measure the maximum reasonable amount of coracoplasty to be performed. A postoperative coracoid thickness of 4 mm should remain., Finanziert durch den Open-Access-Publikationsfonds der Westfälischen Wilhelms-Universität Münster (WWU Münster).

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., Finanziert durch den Open-Access-Publikationsfonds der Westfälischen Wilhelms-Universität Münster (WWU Münster).

Fragestellung: Diese Studie untersucht den stabilisierenden Effekt moderner Cerclagen bei Längsfrakturen langer Röhrenknochen anhand ihrer biomechanischen Eigenschaften. Methodik: Folgende Cerclagen wurden am humanen Humerus und am Kunstknochen mit und ohne Interposition von Gewebe des [zum vollständigen Text gelangen Sie über die oben angegebene URL]

Supplemental material, sj-pdf-1-ajs-10.1177_0363546520981559 for Comparison of Different Fixation Techniques of the Long Head of the Biceps Tendon in Superior Capsule Reconstruction for Irreparable Posterosuperior Rotator Cuff Tears: A Dynamic Biomechanical Evaluation by Daniel P. Berthold, Lukas N. Muench, Felix Dyrna, Bastian Scheiderer, Elifho Obopilwe, Michael R. Krifter, Guiseppe Milano, Ryan Bell, Andreas Voss, Andreas B. Imhoff, Augustus D. Mazzocca, Knut Beitzel and Mark P. Cote in The American Journal of Sports Medicine

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.

Supplemental material, DS_10.1177_0363546519833990 for Dynamic Anterior Shoulder Stabilization With the Long Head of the Biceps Tendon: A Biomechanical Study by Julian Mehl, Alexander Otto, Florian B. Imhoff, Matthew Murphy, Felix Dyrna, Elifho Obopilwe, Mark Cote, Alexandre Lädermann, Philippe Collin, Knut Beitzel and Augustus D. Mazzocca in The American Journal of Sports Medicine

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 51

Supplemental material, DS_10.1177_0363546518802842 for Human Subacromial Bursal Cells Display Superior Engraftment Versus Bone Marrow Stromal Cells in Murine Tendon Repair by Felix Dyrna, Philip Zakko, Leo Pauzenberger, Mary Beth McCarthy, Augustus D. Mazzocca and Nathaniel A. Dyment in The American Journal of Sports Medicine

The stem cell as the building block necessary for tissue reparation and homeostasis plays a major role in regenerative medicine. Their unique property of being pluripotent, able to control immune process and even secrete a whole army of anabolic mediators, draws interest. While new arthroscopic procedures and techniques involving stem cells have been established over the last decade with improved outcomes, failures and dissatisfaction still occur. Therefore, there is increasing interest in ways to improve the healing response. MSCs are particularly promising for this task given their regenerative potential. While methods of isolating those cells are no longer poses a challenge, the best way of application is not clear. Several experiments in the realm of basic science and animal models have recently been published, addressing this issue, yet the application in clinical practice has lagged. This review provides an overview addressing the current standing of MSCs in the field of arthroscopic surgery. Level of evidence IV.

Glenoid retroversion is a known independent risk factor for recurrent posterior instability. The purpose was to investigate progressive angles of glenoid retroversion and their influence on humeral head centration and posterior translation with intact, detached, and repaired posterior labrum in a cadaveric human shoulder model.A total of 10 fresh-frozen human cadaveric shoulders were investigated for this study. After CT- canning, the glenoids were aligned parallel to the floor, with the capsule intact, and the humerus was fixed in 60° of abduction and neutral rotation. Version of the glenoid was created after wedge resection from posterior and fixed with an external fixator throughout the testing. Specimens underwent three conditions: intact, detached, and repaired posterior labrum, while version of the glenoid was set from + 5° anteversion to - 25° retroversion by 5° increments. Within the biomechanical setup, the glenohumeral joint was axially loaded (22 N) to center the joint. At 0° of glenoid version and intact labrum, the initial position was used as baseline and served as point zero of centerization. After cyclic preloading, posterior translation force (20 N) was then applied by a material testing machine, while start and endpoints of the scapula placed on an X-Y table were measured.The decentralization of the humeral head at glenoid version angles of 5°, 10°, 15°, and 20° of retroversion and 5° of anteversion was significantly different (P 0.001). Every increment of 5° of retroversion led to an additional decentralization of the humeral head overall by (average ± SD) 2.0 mm ± 0.3 in the intact and 2.0 mm ± 0.7 in the detached labrum condition. The repaired showed significantly lower posterior translation compared to the intact condition at 10° (P = 0.012) and 15° (P 0.01) of retroversion. In addition, CT measured parameters (depth, diameter, and native version) of the glenoid showed no correlation with angle of dislocation of each specimen.Bony alignment in terms of glenoid retroversion angle plays an important role in joint centration and posterior translation, especially in retroversion angles greater than 10°. Isolated posterior labrum repair has a significant effect on posterior translation in glenoid retroversion angles of 5° and 10°. Bony correction of glenoid version may be considered to address posterior shoulder instability with retroversion 15°.