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. MethodsThirteen 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. ResultsWhen 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 (χ2=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. ConclusionThe 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 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 T10 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). ConclusionM2-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.
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). ConclusionComputer-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.