Polydopamine-coated biomimetic bone scaffolds loaded with exosomes promote osteogenic differentiation of BMSC and bone regeneration.

Introduction: The repair of bone defects is ideally accomplished with bone tissue engineering. Recent studies have explored the possibility of functional modification of scaffolds in bone tissue engineering. We prepared an SF-CS-nHA (SCN) biomimetic bone scaffold and functionally modified the scaffold material by adding a polydopamine (PDA) coating loaded with exosomes (Exos) of marrow mesenchymal stem cells (BMSCs). The effects of the functional composite scaffold (SCN/PDA-Exo) on BMSC proliferation and osteogenic differentiation were investigated. Furthermore, the SCN/PDA-Exo scaffolds were implanted into animals to evaluate their effect on bone regeneration. Methods: SCN biomimetic scaffolds were prepared by a vacuum freeze-drying/chemical crosslinking method. A PDA-functionalized coating loaded with BMSC-Exos was added by the surface coating method. The physical and chemical properties of the functional composite scaffolds were detected by scanning electron microscopy (SEM), energy spectrum analysis and contact angle tests. In vitro, BMSCs were inoculated on different scaffolds, and the Exo internalization by BMSCs was detected by confocal microscopy. The BMSC proliferation activity and cell morphology were detected by SEM, CCK-8 assays and phalloidin staining. BMSC osteogenic differentiation was detected by immunofluorescence, alizarin red staining and qRT‒PCR. In vivo, the functional composite scaffold was implanted into a rabbit critical radial defect model. Bone repair was detected by 3D-CT scanning. HE staining, Masson staining, and immunohistochemistry were used to evaluate bone regeneration. Results: Compared with the SCN scaffold, the SCN/PDA-Exo-functionalized composite scaffold had a larger average surface roughness and stronger hydrophilicity. In vitro, the Exos immobilized on the SCN/PDA-Exo scaffolds were internalized by BMSCs. The BMSC morphology, proliferation ability and osteogenic differentiation effect in the SCN/PDA-Exo group were significantly better than those in the other control groups (p < 0.05). The effects of the SCN/PDA-Exo functional composite scaffold on bone defect repair and new bone formation were significantly better than those of the other control groups (p < 0.05). Conclusions: In this study, we found that the SCN/PDA-Exo-functionalized composite scaffold promoted BMSC proliferation and osteogenic differentiation in vitro and improved bone regeneration efficiency in vivo. Therefore, combining Exos with biomimetic bone scaffolds by functional PDA coatings may be an effective strategy for functionally modifying biological scaffolds.

Arthroscopic percutaneous pullout suture transverse tunnel technique repair for tibial spine fractures in skeletally immature patients.

PURPOSE: We introduce an arthroscopic percutaneous pullout suture transverse tunnel (PP-STT) technique for repair tibial spine fractures (TSF) in skeletally immature patients (SIPs) to avoid damage to the tibial epiphyseal and evaluate the clinical and radiological outcomes of the PP-STT technique for repair TSF in SIPs. METHODS: Between February 2013 and November 2019, 41 skeletally immature patients were diagnosed with TSF; 21 patients were treated using the conventional transtibial pullout suture (TS-PLS) technique (group 1), and 20 patients were treated using the PP-STT technique (group 2). We compared clinical outcomes using the International Knee Documentation Committee (IKDC), Lysholm, Tegner, and visual analog scale (VAS) scores and participant sport levels, after a minimum of two year follow-up. Residual knee laxity was evaluated using Lachman and anterior drawer tests. Fracture healing and displacement were compared using X-ray. RESULTS: Significant improvements in clinical and radiological outcomes between preoperative and final follow-up (Lysholm, Tegner, IKDC, and VAS scores; Lachman and anterior drawer tests; and fracture displacement; p = 0.001) were achieved in both groups, with no significant between-group differences. Groups 1 and 2 exhibited no significant difference in time to radiographic healing (12.2 ± 1.3 weeks vs 13.1 ± 1.5 weeks, respectively; p = 0.513) or in the rate of return to sports level (19 (90.4%) vs 18 (90.0%), respectively; p = 0.826). CONCLUSION: Both surgical techniques provided satisfactory clinical and radiological outcomes. PP-STT may be a suitable alternative to protect the tibial epiphyseal for repair TSP in SIPs.

Outcomes After Combined Remnant Preservation and Bone Marrow Stimulation for Acute Rotator Cuff Tears.

Background: Both remnant preservation (RP) and bone marrow stimulation (BMS) enhance the healing potential of the repaired rotator cuff by improving the biological milieu of the tendon-bone interface. Purpose: To evaluate the clinical and imaging outcomes of arthroscopic rotator cuff repair using a combined RP-BMS technique in patients with acute rotator cuff tears. Study Design: Cohort study; Level of evidence, 3. Methods: Between January 2016 and June 2019, a total of 56 patients were diagnosed with acute rotator cuff tears; 29 patients underwent conventional repair (group 1), and 27 patients underwent RP-BMS (group 2). At a minimum follow-up period of 2 years, the authors compared clinical outcomes with the University of California-Los Angeles; Constant; American Shoulder and Elbow Surgeons; and pain visual analog scale scores as well as shoulder range of motion. Tendon integrity and retear were assessed on magnetic resonance imaging according to the Sugaya classification (intact, grades 1-3; retear, grades 4-5). Between-group comparisons were conducted using the Student t test or Mann-Whitney U test for continuous variables and the Pearson chi-square test or Fisher exact test for categorical variables. Results: In both groups, patients had significant preoperative to postoperative improvement on all clinical outcome measures (P = .001 for all). Shoulder abduction in group 2 was significantly greater compared with group 1 at the postoperative 3-month (107.37° ± 8.32° vs 95.44° ± 8.78°; P = .001), 6-month (155.25° ± 10.02° vs 144.72° ± 9.28°; P = .001), and final (165.15° ± 9.17° vs 158.31° ± 8.01°; P = .021) follow-ups. At the final follow-up, significantly more patients in group 2 had intact tendons (Sugaya grades 1-3) compared with group 1 (P = .015), and the tendon retear rate was lower in group 2 (1/27; 3.70%) than in group 1 (7/29; 24.14%) (P = .033). Conclusion: Both surgical techniques led to satisfactory clinical outcomes, but shoulder abduction was greater after the RP-BMS technique compared with conventional repair. RP-BMS may be an alternative surgical technique to improve tendon integrity and retear rates after the repair of acute rotator cuff tears.

A silk fibroin/chitosan/nanohydroxyapatite biomimetic bone scaffold combined with autologous concentrated growth factor promotes the proliferation and osteogenic differentiation of BMSCs and repair of critical bone defects.

Purpose: With the goal of increasing the translational efficiency of bone tissue engineering for practical clinical applications, biomimetic composite scaffolds combined with autologous endogenous growth factors for repairing bone defects have become a current research hotspot. In this study, we prepared a silk fibroin/chitosan/nanohydroxyapatite (SF/CS/nHA) composite biomimetic scaffold and then combined it with autologous concentrated growth factor (CGF) to explore the effect of this combination on the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and the efficiency of repairing critical radial defects. Methods: Three kinds of SF/CS/nHA composite biomimetic scaffolds with mass fractions of 3%, 4%, and 5% were prepared by vacuum freeze-drying and chemical cross-linking methods, and the characteristics of the scaffolds were evaluated. In vitro, BMSCs were seeded on SF/CS/nHA scaffolds, and then CGF was added. The morphology and proliferation of BMSCs were evaluated by live-dead staining, phalloidin staining, and CCK-8 assays. ALP staining, alizarin red staining, cellular immunofluorescence, RT-PCR, and Western blotting were used to detect the osteogenic differentiation of BMSCs. In vivo, a rabbit radius critical bone defect model was constructed, and the SF/CS/nHA-BMSC scaffold cell complex combined with CGF was implanted. The effect on bone defect repair was evaluated by 3D CT scanning, HE staining, Masson staining, and immunohistochemistry. Results: The characteristics of 4% SF/CS/nHA were the most suitable for repairing bone defects. In vitro, the SF/CS/nHA combined CGF group showed better adhesion, cell morphology, proliferation, and osteogenic differentiation of BMSCs than the other groups (P < 0.05 for all). In vivo imaging examination and histological analysis demonstrated that the SF/CS/nHA scaffold combined with CGF had better efficiency in bone defect repair than the other scaffolds (P < 0.05 for all). Conclusions: A SF/CS/nHA composite biomimetic bone scaffold combined with autologous CGF promoted the proliferation and osteogenic differentiation of BMSCs in vitro and improved the repair efficiency of critical bone defects in vivo. This combination may have the potential for clinical translation due to its excellent biocompatibility.

Shared ACL Bone Tunnel Technique for Repair of Lateral Meniscus Posterior Root Tears Combined With ACL Reconstruction.

Background: Independent transtibial pullout repair is a common surgical technique for repairing lateral meniscus posterior root tears (LMPRTs). The shared anterior cruciate ligament (ACL) bone tunnel technique is an alternative technique for LMPRT repair combined with ACL reconstruction (ACLR) to avoid the establishment of additional bone tunnels. Purpose: To compare the clinical outcomes of the shared ACL bone tunnel versus the independent transtibial pullout techniques for LMPRT repair combined with ACLR. Study Design: Cohort study; Level of evidence, 3. Methods: Between March 2014 and February 2018, a total of 48 patients were diagnosed with ACL injury with concomitant LMPRT; 22 patients underwent independent transtibial pullout repair (group T), and 26 patients underwent the shared ACL bone tunnel technique (group S). At a follow-up of >2 years, we compared knee functional recovery using the Lysholm, Tegner, and International Knee Documentation Committee scores and the pivot-shift test. Lateral meniscal extrusion, and cartilage degeneration on magnetic resonance imaging (MRI) scans were also compared. The healing status of the lateral meniscus posterior root was compared using second-look arthroscopy and MRI. Results: The duration of surgery was significantly shorter in group S compared with group T (98.3 ± 11.1 vs 127.9 ± 17.5 min; P = .001). At final follow-up, there were no significant differences between the 2 groups in knee functional scores, pivot shift, or grade of cartilage degeneration. Lateral meniscal extrusion was decreased in group S compared with group T (2.41 ± 0.61 vs 1.59 ± 1.35 mm; P = .014). Second-look arthroscopy revealed stable healing in 16 of 18 patients (88.9%) in group S and 10 of 15 patients (66.7%) in group T (P = .38). Conclusion: Both the shared ACL bone tunnel and the independent transtibial pullout techniques led to satisfactory clinical outcomes. The shared ACL bone tunnel technique is the simpler of the 2 procedures for combined LMPRT repair with ACLR.