Abstract Purpose To determine the attachment sites of the medial patellofemoral ligament (MPFL) and medial patellotibial ligament (MPTL) through anatomical and imaging measurements, and to suggest a possible method for locating the tibial attachment of MPTL for reconstruction purposes. Methods Twenty‐six adult knee specimens (16 formalin‐fixed, 10 fresh‐frozen) underwent anatomical and imaging measurements, including the morphology of MPFL and MPTL and distances from their attachment points to bony landmarks. Two parameters were used to determine the MPTL tibial attachment position: (1) Anatomical vertical distance to the tibial joint line; (2) a/b ratio on anteroposterior (AP) X‐ray. For the a/b ratio, line 1 was defined as perpendicular to the tibial joint line and passing through the tibial tuberosity centre, and line 2 was drawn parallel to line 1 and passing through the medial edge of the femoral medial epicondyle; the vertical distance from the MPTL tibial attachment to line 1 was termed ‘a’, and the distance between line 1 and line 2 was termed ‘b’. Results The MPFL and MPTL were consistently identified in second layer of the medial retinaculum. The tibial attachment of MPTL was 14.0 ± 0.7 mm from the tibial joint line, and the a/b ratio on the AP X‐ray was 0.51 ± 0.03. Additional anatomical parameters, including ligament dimensions and distances to surrounding bony landmarks, were also documented. There were no significant differences between the results of the imaging and anatomical measurements of the distances from the ligament attachment points to the bony landmarks (p > 0.05). Conclusion For MPTL reconstruction, the tibial attachment can be located 14 mm distal to the joint line and halfway between the tibial tuberosity centre and medial epicondyle (a/b = 0.51). This method serves as a reference and warrants further validation in biomechanical and reproducibility studies. Level of Evidence Level V, cadaveric anatomical study.

M2 microglia transplantation has previously demonstrated beneficial effects on spinal cord injury (SCI) by regulating neuroinflammation and enhancing neuronal survival. Exosomes (EXOs), secreted by almost all cell types, embody partial functions and properties of their parent cells. However, the effect of M2 microglia-derived EXOs (M2-EXOs) on SCI recovery and the underlying molecular mechanisms remain unclear. In this study, we isolated M2-EXOs and intravenously introduced them into mice with SCI. Considering the reciprocal communication between microglia and astroglia in both healthy and injured central nervous systems (CNSs), we subsequently focused on the influence of M2-EXOs on astrocyte phenotype regulation. Our findings indicated that M2-EXOs promoted neuron survival and axon preservation, reduced the lesion area, inhibited A1 astrocyte activation, and improved motor function recovery in SCI mice. Moreover, they inhibited the nuclear translocation of p65 and the activation of the NF-κB signalling pathway in A1 astrocytes. Therefore, our research suggests that M2-EXOs mitigate the activation of neurotoxic A1 astrocytes by inhibiting the NF-κB signalling pathway, thereby improving spinal tissue preservation and motor function recovery following SCI. This positions M2-EXOs as a promising therapeutic strategy for SCI.

Objective:To compare the intraoperative effects of computer navigation-assisted versus simple arthroscopic reconstruction of posterior cruciate ligament (PCL) tibial tunnel. Methods:The clinical data of 73 patients with PCL tears who were admitted between June 2021 and June 2022 and met the selection criteria were retrospectively analysed, of whom 34 cases underwent PCL tibial tunnel reconstruction with navigation-assisted arthroscopy (navigation group) and 39 cases underwent PCL tibial tunnel reconstruction with arthroscopy alone (control group). There was no significant difference in baseline data between the two groups, including gender, age, body mass index, side of injury, time from injury to surgery, preoperative posterior drawer test, knee range of motion (ROM), Tegner score, Lysholm score, and International Knee Documentation Committee (IKDC) score between the two groups ( P>0.05). The perioperative indicators (operation time and number of guide wire drillings) were recorded and compared between the two groups. The angle between the graft and the tibial tunnel and the exit positions of the tibial tunnel in the coronal, sagittal, and transverse planes respectively were measured on MRI at 1 day after operation. The knee ROM, Tegner score, Lysholm score, and IKDC score were evaluated before operation and at last follow-up. Results:The operation time in the navigation group was shorter than that in the control group, and the number of intraoperative guide wire drillings was less than that in the control group, the differences were significant ( P<0.05). Patients in both groups were followed up 12-17 months, with an average of 12.8 months. There was no perioperative complications such as vascular and nerve damage, deep venous thrombosis and infection of lower extremity. During the follow-up, there was no re-injuries in either group and no revision was required. The results showed that there was no significant difference in the exit positions of the tibial tunnel in the coronal, sagittal, and transverse planes between the two groups ( P>0.05), but the angle between the graft and the tibial tunnel was significantly greater in the navigation group than in the control group ( P<0.05). At last follow-up, 30, 3, 1 and 0 cases were rated as negative, 1+, 2+, and 3+ of posterior drawer test in the navigation group and 33, 5, 1, and 0 cases in the control group, respectively, which significantly improved when compared with the preoperative values ( P<0.05), but there was no significant difference between the two groups ( P>0.05). At last follow-up, ROM, Tegner score, Lysholm score, and IKDC score of the knee joint significantly improved in both groups when compared with preoperative values ( P<0.05), but there was no significant difference in the difference in preoperative and postoperative indicators between the two groups ( P>0.05). Conclusion:Computer-navigated arthroscopic PCL tibial tunnel reconstruction can quickly and accurately prepare tunnels with good location and orientation, with postoperative functional scores comparable to arthroscopic PCL tibial tunnel reconstruction alone.

Objective:To investigate the effect of M2 microglia (M2-MG) transplantation on spinal cord injury (SCI) repair in mice.Methods:Primary MG were obtained from the cerebral cortex of 15 C57BL/6 mice born 2-3 days old by pancreatic enzyme digestion and identified by immunofluorescence staining of Iba1. Then the primary MG were co-cultured with interleukin 4 for 48 hours (experimental group) to induce into M2 phenotype and identified by immunofluorescence staining of Arginase 1 (Arg-1) and Iba1. The normal MG were harvested as control (control group). The dorsal root ganglion (DRG) of 5 C57BL/6 mice born 1 week old were co-cultured with M2-MG for 5 days to observe the axon length, the DRG alone was used as control. Forty-two 6-week-old female C57BL/6 mice were randomly divided into sham group ( n=6), SCI group ( n=18), and SCI+M2-MG group ( n=18). In sham group, only the laminae of T 10 level were removed; SCI group and SCI+M2-MG group underwent SCI modeling, and SCI+M2-MG group was simultaneously injected with M2-MG. The survival of mice in each group was observed after operation. At immediate (0), 3, 7, 14, 21, and 28 days after operation, the motor function of mice was evaluated by Basso Mouse Scale (BMS) score, and the gait was evaluated by footprint experiment at 28 days. The spinal cord tissue was taken after operation for immunofluorescence staining, in which glial fibrillary acidic protein (GFAP) staining at 7, 14, and 28 days was used to observe the injured area of the spinal cord, neuronal nuclei antigen staining at 28 days was used to observe the survival of neurons, and GFAP/C3 double staining at 7 and 14 days was used to observe the changes in the number of A1 astrocytes.Results:The purity of MG in vitro reached 90%, and the most of the cells were polarized into M2 phenotype identified by Arg-1 immunofluorescence staining. M2-MG promoted the axon growth when co-cultured with DRGs in vitro ( P<0.05). All groups of mice survived until the experiment was completed. The hind limb motor function of SCI group and SCI+M2-MG group gradually recovered over time. Among them, the SCI+M2-MG group had significantly higher BMS scores than the SCI group at 21 and 28 days ( P<0.05), and the dragging gait significantly improved at 28 days, but it did not reach the level of the sham group. Immunofluorescence staining showed that compared with the SCI group, the SCI+M2-MG group had a smaller injury area at 7, 14, and 28 days, an increase in neuronal survival at 28 days, and a decrease in the number of A1 astrocytes at 7 and 14 days, with significant differences ( P<0.05).Conclusion:M2-MG transplantation improves the motor function of the hind limbs of SCI mice by promoting neuron survival and axon regeneration. This neuroprotective effect is related to the inhibition of A1 astrocytes polarization.

PurposeThe purpose of this study was to compare clinical scores and imaging outcomes of bony Bankart lesions that underwent single-point and modified double-pulley fixation after at least 2 years of follow-up. MethodsPatients who underwent surgery to treat bony Bankart injuries were included and divided into groups A and B. A total of 69 patients were included (32 in group A and 37 in group B). Patients in group A underwent arthroscopic modified double-pulley fixation and patients in group B underwent arthroscopic single-point fixation. Three-dimensional computed tomography (3D-CT) was used to assess glenoid reduction one day after surgery. Postoperative bony union was assessed using 3D-CT and multiplanar reconstruction images 6 months after surgery. Constant-Murley, Rowe rating system, visual analogue scale and University of California at Los Angeles and American Shoulder and Elbow Surgeons scores were recorded before and after surgery. ResultsIn terms of imaging measurements, there was no significant group difference in the preoperative size of the glenoid defect, the size of the bony fragment or the expected postoperative size of the glenoid defect. The sizes of the actual postoperative glenoid defects differed significantly between the groups (p = 0.027), as did the absolute difference between the expected and actual glenoid defect sizes (p < 0.001). At 6 months postoperatively, 50.0% of group A patients and 24.3% of group B patients exhibited complete bony union (p = 0.027); the rates of partial union were 37.5% and 56.8%, respectively. At the final follow-up, all clinical scores were significantly better than the preoperative scores (all p < 0.05), with no significant group differences (not significant). ConclusionsThe use of the modified double-pulley technique with two anchors to treat bony Bankart injuries provides a better reduction of bone fragments than single-point fixation with two anchors and was associated with a higher rate of early bone union. Level of EvidenceLevel III.

Objective To explore the effectiveness of different knee arthroscopic medial collateral ligament release techniques in the treatment of patients with medial meniscus posterior horn injury and their prognoses. Methods A total of 54 patients with medial meniscus posterior horn injury who underwent surgical treatment at the Department of Sports Medicine in our hospital from June to August 2021 were enrolled. They were divided into group A (who underwent knee arthroscopic percutaneous outside-in, superficial release) and group B (who underwent knee arthroscopic inside-out, anteromedial release) based on the conditions and wishes of the patients. The two groups of patients were recorded and compared for surgical duration and follow-up outcomes of the following indices at 1, 3, and 12 months after surgery: local symptom duration, visual analogue score of knee pain, Lysholm score of knee joints, International Knee Documentations Committee Rating System-based score, and knee joint range of motion score. Results There was no significant difference in surgical duration between the two groups of patients (P>0.05), but the local symptom duration in group B was significantly shorter than that in group A (t=11.950,P<0.01). The results of repeated measures analysis of variance showed that time had a significant impact on postoperative knee joint function scores of the patients (Ftime=1 805.492-2 715.143,P<0.05). Compared with the scores 1 month after surgery, knee joint function scores of the patients in groups A and B significantly improved at 3 and 12 months after surgery (F=700.701-1 557.491,P<0.05). However, there were no significant differences in knee joint function scores between the two groups of patients at each follow-up time point after surgery (P>0.05). Conclusion For patients with simple medial meniscus posterior horn injury, it is recommended to use knee arthroscopic anteromedial inside-out, superficial release if the surgeons are confident of the condition.

Objective:To evaluate the postoperative clinical efficacy and meniscus healing of knee anterior cruciate ligament(ACL) injury with lateral meniscus posterior horn tear by different treatment methods with different tear lengths, and to provide basis and reference for clinical decision-making of knee ACL injury with lateral meniscus posterior horn tear.Methods:A retrospective analysis was carried out on 113 patients with ACL injury accompanied with lateral meniscus posterior angle tear who were admitted to the Sports Medicine Department of Qingdao University Affiliated Hospital from 2010 to 2019. Inclusion criteria: ACL injury with lateral meniscus posterior angle tear; the distance between the tear edge of the meniscus and the synovial margin was within 5 mm during surgery; the postoperative follow-up time was 12 months. Exclusion criteria: multiple ligament injuries in the knee joint; inner meniscus injury; accompanying knee joint fractures; the duration was more than six months after trauma. According to the posterior horn tear length of the lateral meniscus and whether it had been sutured for repair, the patients were divided into two groups: the small tear group in which the posterior horn tear length was less than 15 mm and no popliteal tendon involved (33 cases were not sutured for repair in the small tear group A; 27 cases were fully sutured in the small tear group B); the moderate tear group in which the posterior horn tear length was larger than 15 mm but less than 20 mm, and no popliteal tendon involved (28 cases were not sutured for repair in the moderate tear group A, while 25 cases were fully sutured in the moderate tear group B). Lysholm score, International Knee Joint Documentation Committee (IKDC) score, and imaging MRI examination before surgery and at 12 months follow-up after surgery were recorded. The data were analyzed by repeated measurement analysis of variance, chi square test, and histogram format.Results:All the patients were followed up and showed improvement in their clinical functional scores at the last follow-up compared to the scores before surgery. For patients with lateral meniscus tear length less than 15 mm, there was no statistically significant difference in postoperative Lysholm functional score and IKDC score between suture repair and non-suture repair (F=0.49, 2.21, all P>0.05). For lateral meniscus tear-length of 15 to 20 mm, the postoperative Lysholm functional score and IKDC score of the suture repair group were significantly improved compared to the non-suture repair group (F=189.21, 41.08, all P <0.05). MRI results at follow-up showed that all patients in small tear group achieved satisfactory healing; the healing rates of the two subgroups in the moderate group was 96.4% and 96.0% respectively, which showed no statistically significant difference(χ2=0.94, P>0.05).Conclusions:For patients with ACL injury accompanied with posterior horn tear of lateral meniscus, if the popliteal tendon is not involved and the tear length is less than 15 mm, the posterior horn of lateral meniscus can be healed without repair, which may achieve the equal clinical efficacy as suture repair of meniscus and simple ACL reconstruction. If the popliteal tendon is not involved and the tear length is larger than 15 mm and less than 20 mm, suture repair of the posterior horn of the lateral meniscus tear is stronly recommended.

Ferroptosis plays crucial roles in the pathology of spinal cord injury (SCI). The purpose of this study was to identify differentially expressed ferroptosis-related genes (DE-FRGs) in human acute SCI by bioinformatics analysis and validate the hub DE-FRGs in non-SCI and SCI patients. The GSE151371 dataset was downloaded from the Gene Expression Omnibus and difference analysis was performed. The differentially expressed genes (DEGs) in GSE151371 overlapped with the ferroptosis-related genes (FRGs) obtained from the Ferroptosis Database. A total of 41 DE-FRGs were detected in 38 SCI samples and 10 healthy samples in GSE151371. Then, enrichment analyses of these DE-FRGs were performed for functional annotation. The GO enrichment results showed that upregulated DE-FRGs were mainly associated with reactive oxygen species and redox reactions, and the KEGG enrichment analysis indicated involvement in some diseases and ferroptosis pathways. Protein-protein interaction (PPI) analysis and lncRNA-miRNA-mRNA regulatory network were performed to explore the correlations between genes and regulatory mechanisms. The relationship between DE-FRGs and differentially expressed mitochondria-related genes (DE-MRGs) was also analyzed. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the hub DE-FRGs in clinical blood samples from acute SCI patients and healthy controls. Consistent with the bioinformatics results, qRT-PCR of the clinical samples indicated similar expression levels of TLR4, STAT3, and HMOX1. This study identified DE-FRGs in blood samples from SCI patients, and the results could improve our understanding of the molecular mechanisms of ferroptosis in SCI. These candidate genes and pathways could be therapeutic targets for SCI.

Objective:To investigate whether the outlet of the femoral tunnel will cause iatrogenic injury to the medial collateral ligament (MCL) during posterior cruciate ligament reconstruction (PCLR) and estimate the safe angle of femoral tunnel placement.Methods:Thirteen formaldehyde-soaked human knee joint specimens were used, 8 from men and 5 from women; the donors' age ranged from 49 to 71 years, with an average of 61 years. First, the medial part of the femur was carefully dissected to clearly expose the region of the MCL course and attachment on the femoral medial aspect and to outline the anterior margin of the region with a marked line. The marked line divided the medial femoral condyle into an area with an MCL course and a bare bone area which is regarded relatively safe for no MCL course. Then, the posterior cruciate ligament (PCL) was cut to identify the femoral attachment of the PCL. After the knee joint was fixed at a 120° flexion angle, the process of femoral tunnel preparation for the PCL single-bundle reconstruction was simulated. The inside-out technique was used to drill the femoral tunnel from the PCL femoral footprint inside the knee joint with an orientation to exit the medial condyle of the femur, and the combination angle of the two planes, the axial plane and the coronal plane, was adapted to the process of drilling femoral tunnels at different orientations. The following 15 angle combinations were used in the study: 0°/30°, 0°/45°, 0°/60°, 15°/30°, 15°/45°, 15°/60°, 30°/30°, 30°/45°, 30°/60°, 45°/30°, 45°/45°, 45°/60°, 60°/30°, 60°/45°, 60°/60° (axial/coronal). The positional relationship between the femoral tunnel outlet on the femoral medial condyle and the marked line was used to verify whether the tunnel drilling angle was a risk factor for MCL injury or not, and whether the shortest distance between the femoral exit center and the marked line was affected by the various angle combinations. Furthermore, the safe orientation of the femoral tunnel placement would estimated.Results:When creating the femoral tunnel for PCLR, there was a risk of damage to the MCL caused by the tunnel outlet, and the incidence was from 0 to 100%; when the drilling angle of the axial plane was 0° and 15°, the incidence of MCL damage was from 69.23% to 100%. There was a significant difference in the incidence of MCL damage among femoral tunnels of 15 angle combinations ( χ 2=148.195, P<0.001). By comparison between groups, it was found that when drilling femoral tunnels at 5 combinations of 45°/45°, 45°/60°, 60°/30°, 60°/45°, and 60°/60° (axial/coronal), the shortest distances between the tunnel exit and the marked line were significantly different than 0°/45°, 0°/60°, 15°/45°, 15°/60°, and 30°/30° (axial/coronal) ( P<0.05). Additionally, after comparing the median of the shortest distance with other groups, the outlets generated by these 5 angles were farther from the marked line and the posterior MCL.Conclusion:The creation of the femoral tunnel in PCLR can cause iatrogenic MCL injury, and the risk is affected by the tunnel angle. To reduce the risk of iatrogenic injury, angle combinations of 45°/45°, 45°/60°, 60°/30°, 60°/45°, and 60°/60° (axial/coronal) are recommended for preparing the femoral tunnel in PCLR.

Objective: Tendons are the special connective tissue that connects bones to muscles and governs joint movement in response to loads passed by muscles. The healing of tendon injuries is still a challenge. In recent years, adipose-derived mesenchymal stem cells (ADSCs) have been increasingly used for tissue regeneration, but the underlying mechanism of tendon injury still remains unclear. Methods: High-throughput sequencing was used to identify a novel lncRNA, whose expression was significantly decreased in injured tendon compared with normal tendon. Furthermore, pyrosequencing, nuclear-cytoplasmic separation, FISH assay and qRT-PCR analysis were used to verify the level of lncRNA methylation in the injured tenocytes. lncRNA was confirmed to promote the proliferation of tenocytes by flow cytometry, wound healing assay, qRT-PCR, and western blot, and the target gene of lncRNA was predicted and verified. To confirm that ADSCs could repair injured tendons, ADSCs and injured tenocytes were co-cultured in vitro, and ADSCs were injected into injured tendons in vitro, respectively. Results: The lncRNA Morf4l1 promoter methylation in injured tendons led to down-regulation of its expression and inhibition of tenocyte proliferation. LncRNA Morf4l1 promoted the expression of TGF-β2 by targeting 3′U of miR-145-5p. After co-cultured ADSCs and injured tenocytes, the expression of lncRNA Morf4l1 was up-regulated, and the proliferation of injured tenocytes in vitro was promoted. The ADSCs were injected into the injured tendon to repair the injured tendon in vivo. Conclusion: This study confirmed that ADSCs promoted tendon wound healing by reducing the methylation level of lncRNA Morf4l1.

Traumatic central nervous system (CNS) disorders have catastrophic effects on patients, and, currently, there is no effective clinical treatment. Cell transplantation is a common treatment for traumatic CNS injury in animals. In recent years, an increasing number of studies have reported that the beneficial effect of transplanted cells for CNS repair is mediated primarily through the extracellular vesicles (EVs) secreted by the cells, in which microRNAs play a major role. Accordingly, numerous studies have evaluated the roles and applications of EVs secreted by different cell types in neurological diseases. Furthermore, due to their unique biological features, EVs are used as disease biomarkers and drug delivery systems for disease prevention and treatment. We discuss current knowledge related to EVs, focusing on the mechanism underlying their effects on traumatic CNS diseases, and summarize existing research on the potential clinical utility of EVs as disease biomarkers and drug delivery systems.