Objective To determine the permissive safe angle (PSA) of the tibial tunnel in transtibial posterior cruciate ligament (PCL) reconstruction based on a three‐dimensional (3D) simulation study. Methods This was a computer simulation study of transtibial PCL reconstruction using 3D knee models. CT images of 90 normal knee joints from 2017 to 2020 were collected in this study, and 3D knee models were established based on CT data. The tunnel approaches were subdivided into the anterior 1/3 of the anteromedial tibia (T1), middle 1/2 of the anteromedial tibia (T2), the tibial crest (T3), anterior 1/3 of the anterolateral tibia (T4), middle 1/2 of the anterolateral tibia (T5). Five tibial tunnels (T1–T5) were simulated on the 3D knee models. The PSAs, in different tibial tunnel approaches were measured, and subgroup analyses of sex, age and height were also carried out. Results The mean PSAs of the tibial tunnels with 5 different approaches (T1–T5) were 58.49° ± 6.82°, 61.14° ± 6.69°, 56.12° ± 7.53°, 52.01° ± 8.89° and 49.90° ± 10.53°, respectively. The differences of the mean PSAs between the anteromedial and anterolateral approaches were significant (P < 0.05). However, there was no significant difference of the mean PSA value between the two anteromedial tibial tunnel approaches (T1–T2) (P > 0.05), as well as between the two anterolateral tibial tunnel approaches (T4–T5). The patient's anthropomorphic characteristics of sex, age, and height were not associated with the PSAs. Conclusions The PSA varied with the anteromedial, tibial crest and anterolateral approaches for transtibial PCL reconstruction, and surgeons should limit the PCL drill guide by referring to the specific PSA for different surgical approaches.

Objective During the transtibial posterior cruciate ligament (PCL) reconstruction, surgeons commonly pay more attention to the graft turning angle in the sagittal plane (GASP), but the graft turning angle in the coronal plane (GACP) is always neglected. This study hypothesized that the three‐dimensional (3D) killer turn angle was determined by both the GASP and GACP, and aimed to quantitively analyze the effects of the GASP and GACP on the 3D killer turn angle. Methods This was an in‐vitro computer simulation study of transtibial PCL reconstruction using 3D knee models. Patients with knee injuries who were CT scanned were selected from the CT database (April 2019 to January 2021) at a local hospital for reviewing. A total of 60 3D knees were simulated based on the knees' CT data. The femoral and tibial PCL attachment were located on the 3D knee model using the Rhinoceros software. The tibial tunnels were simulated based on different GASP and GACP. The effects of the GASP and GACP on the 3D killer turn angle were quantitatively analyzed. One‐way analysis of variance was used to compare the outcomes in different groups. The regression analysis was performed to identify variables of the GASP and GACP which significantly affected 3D killer turn angle. Results The 3D killer turn angle showed a significant proportional relationship not only with the GASP (r2 > 0.868, P < 0.001), but also with the GACP (r2 > 0.467, P < 0.001). Every 10° change of the GACP caused 2.8° to 4.4° change of the 3D killer turn angle, whereas every 10° change of the GASP caused 6.4° to 9.2° change of the 3D killer turn angle. Conclusions The 3D killer turn angle was significantly affected by both the GASP and GACP. During the transtibial PCL reconstruction, the proximal anterolateral tibial tunnel approach could increase the 3D killer turn angle more obviously compared with the most distal anteromedial tibial tunnel approach. To minimize the killer turn effect, both the GASP and GACP were required to be considered to increase.

Objective Percutaneous suture is a classic technique used in Achilles tendon repair. However, the complication rates surrounding the sural nerve remain relatively high. Modified percutaneous repair technology can effectively avoid these complications; however, the surgical procedure is complicated. Hence, the present study was conducted to describe a redesigned repair technique for the Achilles tendon able to avoid sural nerve injury and reduce the complexity of the procedure. Methods Data of patients with acute primary Achilles tendon rupture at our hospital from January 2019 to May 2020 were included. Subjects with expectations for surgical scarring underwent a minimally invasive‐combined percutaneous puncture technique. The surgical time, requirement for conversion to other technologies, and length of postoperative hospitalization were investigated to assess efficacy. The American Orthopedic Foot & Ankle Society (AOFAS) score and the Arner–Lindholm scale (A‐L scale) were used to assess postoperative clinical outcomes (> 24 months). During the 2‐year follow‐up, MRI was performed to observe the healing of the Achilles tendon. In addition, subjective satisfaction with surgical scar healing was recorded. Results Twenty consecutive subjects with an average follow‐up of 28.3 ± 4.5 months (range, 24–41) met the inclusion criteria. None of the 20 enrolled patients required a converted surgical approach. The mean surgical time was 26.9 ± 6.47 min (range, 20–44). None of the patients experienced dysesthesia or anesthesia around the sural nerve. No signs of postoperative infections were observed. MRI data showed that the wounds of the Achilles tendon healed completely in all the subjects. The AOFAS score increased from 55.6 ± 11.07 (range, 28–71) preoperatively to 97.8 ± 3.34 (range, 87–100) at the last follow‐up. The A‐L scale showed that 90% of the subjects (n = 18) presented as excellent and 10% of the subjects (n = 2) presented as good, with an excellent/good rate of 100%. Moreover, subjects' satisfaction for surgical scars was 9.1 ± 0.78 (upper limit, 10). Conclusions The results indicate that this technique can achieve good postoperative function, a small surgical incision, and high scar satisfaction. In addition, this technique should be widely used in suturing Achilles tendon ruptures.

Objective In order to reduce the “killer turn” effect, various tibial tunnels have been developed. However, few studies investigated the biomechanical effects of different tibial tunnels during PCL reconstruction. This study aims to compare the time‐zero biomechanical properties of anteromedial, anterolateral, lower anteromedial, and lower anterolateral tibial tunnels in transtibial posterior cruciate ligament (PCL) reconstruction under load‐to‐failure loading. Methods Porcine tibias and bovine extensor tendons were used to simulate in vitro transtibial PCL reconstruction. Forty bovine extensor tendons and 40 porcine tibias were randomly divided into four experimental groups: anteromedial tunnel group (AM group, n = 10), anterolateral tunnel group (AL group, n = 10), lower anteromedial tunnel group (L‐AM group, n = 10), and lower anterolateral tunnel group (L‐AL group, n = 10). The biomechanical test was then carried out in each group using the load‐to‐failure test. The ultimate load (in newtons), yield load (in newtons), tensile stiffness (in newtons per millimeter), load‐elongation curve, failure mode, and tibial tunnel length (in millimeter) were recorded for each specimen. One‐way analysis of variance (ANOVA) was used to compare the mean differences among the four groups. Results The biomechanical outcomes showed that there were no differences in the mean tensile stiffness and failure mode among four groups. The ultimate load and yield load of the L‐AM group were significantly higher than those of other three groups (P < 0.05). For the AM group, its ultimate load is significantly higher than that of the L‐AL group (P < 0.05), and its yield load is higher than that of the AL group and L‐AL group (P < 0.05). However, we found no significant differences in either ultimate load or yield load between AL group and L‐AL group (P > 0.05). There was significant statistical difference in the length of tibial tunnel between anatomic groups (AM and AL) and lower groups (L‐AM and L‐AL) (P < 0.05). Conclusion Compared with the anteromedial, anterolateral, and lower anterolateral tibial tunnel, the lower anteromedial tibial tunnel showed better time‐zero biomechanical properties including ultimate load and yield load in transtibial PCL reconstruction.

Background The anatomical positioning of the graft during anterior cruciate ligament reconstruction (ACLR) is of great significance for restoring normal knee kinematics and preventing early joint degeneration. Therefore, the adjustment of the mispositioned guide pin becomes extremely important. Our research aims to test the time-zero biomechanical properties in adjusting inaccurate guide pins to the center of the tibial footprint in anatomical anterior cruciate ligament single-bundle reconstruction. Methods Porcine tibias and bovine extensor tendons were used to simulate a transtibial ACL reconstruction in vitro. Load-to failure testing was carried out in 4 groups: control group ( n = 45): the guide pin was drilled at the center of the ACL footprint; group I, group II and group III ( n = 45, respectively): the guide pin was respectively drilled 1 mm, 2 mm and 3 mm away from the center of the ACL footprint. In the experimental groups, a small tunnel with a 4.5 mm reamer is made and the guide pin is shifted to the center of the footprint. All the reamed tibias were scanned by CT to measure the area of the tunnel in the footprint, and time-zero biomechanical properties were recorded. Results All graft-tibia complexes failed because the grafts slipped past the interference screws. Compare to control group, the ultimate load, yield load, and tunnel exit area in group III decreased significantly ( p < 0.05). Regarding to the ultimate load, yield load, tensile stiffness, twisting force and tunnel exit area, t-test showed no significant differences between control group and group I, group II respectively ( p > 0.05). Pearson test showed that tunnel exit area was negatively correlated with other characteristics ( p < 0.05). Conclusions Surgical adjustment of the guide pin to the center of the tibial footprint may have significant influence in time-zero biomechanical properties in anatomical anterior cruciate ligament single-bundle reconstruction when the adjusted tibial tunnel was significantly enlarged compare to the standard tibial tunnel.