For a liquid droplet to slide down a solid planar surface, the surface usually has to be tilted above a critical angle of approximately 10°. By contrast, droplets of nearly any liquid "slip" on lubricant-infused textured surfaces - so termed slippery surfaces - when tilted by only a few degrees. The mechanism of how the lubricant alters the static and dynamic properties of the drop remains elusive because the drop-lubricant interface is hidden. Here, we image the shape of drops on lubricant-infused surfaces by laser scanning confocal microscopy. The contact angle of the drop-lubricant interface with the substrate exceeds 140°, although macroscopic contour images suggest angles as low as 60°. Confocal microscopy of moving drops reveals fundamentally different processes at the front and rear. Drops recede via discrete depinning events from surface protrusions at a defined receding contact angle, whereas the advancing contact angle is 180°. Drops slide easily, as the apparent contact angles with the substrate are high and the drop-lubricant interfacial tension is typically lower than the drop-air interfacial tension. Slippery surfaces resemble superhydrophobic surfaces with two main differences: drops on a slippery surface are surrounded by a wetting ridge of adjustable height and the air underneath the drop in the case of a superhydrophobic surface is replaced by lubricant in the case of a slippery surface.

II Systematic review of literature.

Background: The risk of recurrence after the first episode of anterior shoulder dislocation is high with nonoperative treatment in younger patients. Purpose/Hypothesis: The aim of this study was to compare the results of arthroscopic Bankart repair and nonoperative treatment for shoulder dislocation in patients younger than 25 years, with a minimum of 2 years of follow-up. The hypothesis was that surgery would decrease the risk of recurrence. Study design: Randomized controlled trial; Level of evidence, 1. Methods: We included patients aged between 18 and 25 years after a first episode of anterior shoulder dislocation and divided them into 2 groups. The first group was treated surgically with an arthroscopic Bankart repair within 2 weeks after the dislocation; the second group was treated nonoperatively. Both groups were immobilized for 3 weeks in internal rotation and followed the same physical therapy protocol. Standard radiography and computed tomography were performed immediately after reduction of the dislocation, and follow-up was performed at 3, 6, 12, and 24 months. The primary outcome measure was instability recurrence, defined as another anterior shoulder dislocation requiring closed reduction by another person (the patient was unable to reduce the dislocated joint themselves), a subluxation, or a positive apprehension test. Secondary outcome measures included range of motion, return to sport, and functional scores such as the short version of the Disabilities of the Arm, Shoulder and Hand score the Walch-Duplay score, and the Western Ontario Shoulder Instability Index (WOSI). Results: A total of 20 patients were included in each group. The mean ± SD age was 21 ± 1.8 years, and there were 33 men (82.5%) and 7 women (17.5%) in the total sample. Recurrence of instability was significantly decreased in the surgical treatment group compared with the nonoperative group (2 [10%] vs 14 [70%], respectively; P = .0001). Fewer patients in the surgical treatment group versus the nonoperative group had another episode of dislocation (0 vs 6 [30%], respectively), subluxation (2 [10%] vs 13 [65%], respectively; P = .003), or a positive apprehension test (1 [5%] vs 11 [58%], respectively; P = .0005). The Walch-Duplay score (88.4 vs 70.3 points; P = .046) and WOSI (11.5 vs 17.7 points; P = .035) were significantly better in the surgical group versus the nonoperative group after a 2-year follow-up. Level of sport was the same or better in 89% of the surgical treatment group vs 53% of the nonoperative treatment group ( P = .012). No surgical complication was recorded. We did not find any significant difference in range of motion. Conclusion: In patients with first-time shoulder dislocations, arthroscopic labral repair (Bankart procedure) reduced the risk of secondary shoulder dislocation and improved functional outcome versus nonoperative treatment after a 2-year follow-up. Surgical treatment after a first episode of shoulder dislocation could be offered as a primary treatment option in a younger population if these results are confirmed by larger studies with a longer follow-up. Registration: NCT03315819 (ClinicalTrials.gov identifier)

IV.

No abstract

Background: An isolated arthroscopic Bankart repair carries a high mid- and long-term risk of recurring instability. Preoperative patient selection based on the Instability Severity Index Score should improve outcomes. Purpose: To report the overall long-term recurrence rate for isolated Bankart repair, investigate the predictive factors for recurrence, analyze time to recurrence, and determine a quantitative cutoff point for recurrence in terms of Instability Severity Index Score. Study Design: Cohort study; Level of evidence, 2. Methods: This was a prospective multicenter study. Inclusion criteria were recurring anterior instability and an Instability Severity Index Score of 4 or less. Of the 125 patients included, 20 patients had a score of 0, 31 patients scored 1, 29 patients scored 2, 34 patients scored 3, and 11 patients scored 4. All centers used the same arthroscopic technique and rehabilitation protocol. Follow-up data were collected at 3, 6, 12, and 24 months and 3 and 9 years. The primary endpoint was recurrence of instability (total or partial dislocation). The statistical analysis was performed by use of the software package SAS 9.4. Results: We initially identified 328 patients, of whom 125 patients were prospectively included. The main reason for excluding the 202 patients was the presence of bony lesions, which carry 2 points each in the Instability Severity Index Score (humeral head notch and/or glenoid lesion visible on standard radiographs). Of the 125 eligible patients, 73% were athletes and 22.5% competitors; 16% were lost at the last follow-up. At the endpoint, 23% had experienced a recurrence after a mean interval of 35 months (range, 5.5-103 months). No statistical differences were found between patients with and without bony lesions in the overall group of 125 patients or in the subgroup with an Instability Severity Index Score of 3 or 4 points (P = .4). According to univariate analysis, the only predictive factor for recurrence was age less than 20 years at the time of surgery, with a 42% rate of recurrence in this group (P = .03). Multivariate analysis showed that the Instability Severity Index Score was the only predictive factor with a quantitative cutoff point (namely, a score of ≤2 points) that was statistically associated with a decreased long term recurrence rate (P = .02). The recurrence rate was 10% for a preoperative Instability Severity Index Score of 2 or less compared with 35.6% for a score of 3 or 4. The survival curves demonstrated no new dislocations after year 4 for patients with an Instability Severity Index Score of up to 2 points. Conclusion: In a preselected population, mainly without bony lesions, the Instability Severity Index Score cutoff value that provides an acceptable recurrence rate at 9 years after isolated Bankart repair is 2 out of 10.

Background: The preoperative number of dislocations has been previously proved to be a major factor influencing the results after Bankart repair with more preoperative dislocations correlated with higher recurrence rates and more reoperations. This could possibly be because of the lower quality of the tissue repaired during the procedure after multiple dislocations. On the other hand, the Latarjet procedure does not ''repair'' but rather reconstructs and augments the anterior glenoid.Purpose/Hypothesis: The main objective was to report the clinical outcomes of patients undergoing a Latarjet procedure after 1 dislocation versus multiple (2) dislocations. The hypothesis was that the preoperative number of dislocations would not influence clinical results.Study Design: Cohort study; Level of evidence, 3.Methods: Patients older than 18 years who had undergone a primary Latarjet procedure for shoulder instability with at least 2 years of follow-up were included. Three different techniques were used: a mini-open technique using 2 screws, an arthroscopic technique using 2 screws, and an arthroscopic technique using 2 cortical buttons. Patients were evaluated and answered a questionnaire to assess the number of episodes of dislocation before surgery, the time between the first dislocation and surgery, recurrence of the dislocation, revision surgery, the Walch-Duplay score, the Simple Shoulder Test score, and the visual analog scale (VAS) score for pain.Results: A total of 308 patients were included for analysis with a mean follow-up of 3.4 6 0.8 years. Of that, 83 patients were included in the first-time dislocation group and 225 in the recurrent dislocation group. At last follow-up, the rates of recurrence and reoperation were not significantly different between groups: 4.8% in the first-time dislocation group versus 3.65% in the recurrent dislocation group and 6.1% versus 4.0%, respectively. The overall Walch-Duplay scores at last follow-up were also comparable between the 2 groups, 67.3 6 24.85 and 71.8 6 25.1, even though the first-time dislocation group showed a lower pain subscore (15.0 6 8.6 vs 18.0 6 7.5; P = .003). The VAS for pain was also significantly higher in the first-time dislocation group compared with the recurrent dislocation group (1.8 6 2.3 vs 1.2 6 1.7; P = .03). Conclusion:The number of episodes of dislocation before surgery does not affect postoperative instability rates and reoperation rates after the Latarjet procedure. However, patients with first-time dislocations had more postoperative pain compared with patients with recurrent dislocations before surgery.

Background: It remains unclear whether results differ between a Latarjet procedure performed after a failed arthroscopic Bankart repair and one performed as the primary operation. Purpose: To compare the postoperative outcomes of the Latarjet procedure when performed as primary surgery and as revision for a failed arthroscopic Bankart repair. Study Design: Cohort study; Level of evidence, 3. Methods: A multicenter retrospective comparative case-cohort analysis was performed for all patients undergoing a Latarjet procedure for recurrent anterior shoulder instability. Patients were separated into 2 groups depending on if the Latarjet procedure was performed after a failed arthroscopic Bankart repair (group 1) or as the first operation (group 2). Outcome measures included recurrent instability, reoperation rates, complications, pain, Walch-Duplay scores, and Simple Shoulder Test. Results: A total of 308 patients were eligible for participation in the study; 72 (23.4%) did not answer and were considered lost to follow-up, leaving 236 patients available for analysis. Mean follow-up was 3.4 ± 0.8 years. There were 20 patients in group 1 and 216 in group 2. Despite similar rates of recurrent instability (5.0% in group 1 vs 2.3% in group 2; P = .5) and revision surgery (0% in group 1 vs 6.5% in group 2; P = .3), group 1 demonstrated significantly worse pain scores (2.56 ± 2.7 vs 1.2 ± 1.7; P = .01) and patient-reported outcomes (Walch-Duplay: 52 ± 25.1 vs 72.2 ± 25.0; P = .0007; Simple Shoulder Test: 9.3 ± 2.4 vs 10.7 ± 1.9; P = .001) when compared with those patients undergoing primary Latarjet procedures. Conclusion: Functional outcome scores and postoperative pain are significantly worse in patients undergoing a Latarjet procedure after a failed arthroscopic Bankart repair when compared with patients undergoing primary Latarjet. The assumption that a failed a Bankart repair can be revised by a Latarjet with a similar result to a primary Latarjet appears to be incorrect. Surgeons should consider these findings when deciding on the optimal surgical procedure for recurrent shoulder instability.