Development of a novel approach for restoration of the meniscus using silk-elastin in a rabbit meniscus injury model.

BACKGROUND: Limited healing potential of the meniscus remains a burden for the successful repair of meniscus injuries in the orthopaedic fields. Silk-elastin (SE) is a novel recombinant protein with favorable properties for wound healing. This proof-of-concept study aimed to investigate the therapeutic effect of silk-elastin in a rabbit meniscal defect model. METHODS: A migration assay using rabbit meniscus and synovial cells with various concentrations of SE in a culture medium was conducted to investigate the mechanism of meniscal healing by SE. Additionally, cylindrical defects with a 1.5 mm diameter were created at the anterior horn of the medial meniscus of rabbits. The animals were divided into three groups: 1) the Blank group; defect only, 2) the Col I group; implantation of type I atelocollagen sponge, and 3) the SE group; implantation of SE (150 mg/ml) sponge. Whole medial menisci were harvested at 4, 8, 12, and 24 weeks after surgery. Histological analyses including immunohistochemical staining were performed to assess meniscal healing. RESULTS: In vitro study, Migration assay demonstrated a significantly higher number of migrated cells only in synovial cells. Especially, the SE concentration of 10 µg/mL demonstrated the highest number of migrated cells compared with other concentrations. In vivo study, the SE group exhibited significantly higher Ishida scores than other groups at all time points. Furthermore, the SE group showed higher synovial coverage scores than the Col I group at 4 and 8 weeks. Immunohistochemical staining demonstrated higher type II collagen staining in the SE group compared to other groups at 12 weeks. Implanted SE was efficiently replaced by safranin-O staining positive tissue within 8 weeks. CONCLUSIONS: SE could effectively repair a meniscal defect by inducing coverage of synovial cells. SE has the potential to be a useful material for meniscal repair.

Posterior wall blowout on computed tomography after anterior cruciate ligament reconstruction.

BACKGROUND: During anterior cruciate ligament (ACL) reconstruction, even when a posterior wall of the femoral bone tunnel is identified, computed tomography (CT) occasionally demonstrates a breach of the posterior femoral cortex of the femoral bone tunnel, i.e., posterior wall blowout, after ACL reconstruction (posterior wall blowout-like phenomenon). This study aimed to investigate the influence of the posterior wall blowout-like phenomenon on clinical outcomes after ACL reconstruction using hamstring tendon. METHODS: A total of 105 patients who underwent CT examination two weeks after ACL reconstruction were enrolled. A cortical suspension device was used for femoral side fixation in all cases. Posterior wall was identified in all cases during the surgery. The side-to-side difference in anterior knee laxity, pivot shift test, Lysholm knee score, the International Knee Documentation Committee (IKDC) subjective form, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were evaluated one year after the surgery. A second CT examination was performed 6-12 months after the surgery, if a posterior wall blowout-like phenomenon was identified in the first CT examination. RESULTS: Two weeks after the surgery, 16 of the 105 patients showed a posterior wall blowout-like phenomenon. Twelve of the 16 cases demonstrated a regenerated posterior femoral cortex of the femoral bone tunnel on their second CT images. There were no significant differences between the posterior wall blowout-like phenomenon group and the normal posterior wall group in terms of a side-to-side difference in anterior knee laxity (0.4 ± 1.5 mm and 0.1 ± 1.6 mm, respectively), pivot shift test, Lysholm knee score, IKDC score, and KOOS at one year after surgery. The length and diameter of the femoral bone tunnel were not significantly different between the two groups. CONCLUSIONS: Posterior wall blowout-like phenomenon after ACL reconstruction using a cortical suspension device did not negatively influence clinical outcomes. LEVEL OF EVIDENCE: III - retrospective comparative clinical study.

Application of a true lateral virtual radiograph from 3D-CT to identify the femoral reference point of the medial patellofemoral ligament.

PURPOSE: The purpose of this study is two-fold: (1) to describe the femoral reference point of the medial patellofemoral ligament (MPFL) on a virtual true lateral radiograph reconstructed from a three-dimensional computed tomography (3D-CT) image and (2) to compare this point with that of patients without patellofemoral instability and with Schöttle's point. METHODS: A total of 26 consecutive patients (29 affected knees) with recurrent patellar dislocation (RPD), who underwent MPFL reconstruction were included in this study (4 males; 22 females; mean age, 24.0 years old). Using a true lateral 3DCT image, the MPFL femoral insertion was identified and marked with a 2-mm circle, and this image was reconstructed as a virtual true lateral radiograph. Following Schöttle's method, the point of intersection was described by their anterior-posterior and proximal-distal positions. As a control population, 29 age- and gender-matched patients with anterior cruciate ligament (ACL) injuries were also analysed. RESULTS: The points in RPD patients were located significantly posterior (-2.5 ± 2.3 mm, p < 0.01) to the line representing an extension of the posterior cortex of the femur and distal (- 6.9 ± 2.4 mm, p < 0.01) to the posterior origin of the medial femoral condyle compared with those in the control population. The mean reference point of RPD patients was located in a 3.8-mm posterior and 4.4-mm distal position compared with Schöttle's point. CONCLUSIONS: An anatomical and radiographic femoral reference point of the MPFL on a true lateral virtual radiograph was described with our method. In patients with RPD, this reference point was identified to be more posterior and distal to Schöttle's point. More anatomical and individualized MPFL reconstruction will be secured using our method. LEVEL OF EVIDENCE: Level IV.

Isolated Lateral Collateral Ligament Injury of the Knee in a Judo Athlete: A Surgical Case Report.

Introduction: We report a rare case of surgical treatment for an isolated lateral collateral ligament (LCL) injury of the knee that was difficult to correctly diagnose considering physical findings alone of a judo athlete. Case Report: The 27-year-old man complained of pain on the lateral side of the right knee and discomfort and balance instability when climbing and descending stairs. During a judo match, he stepped on his right foot to prevent his opponent's waza (techniques), causing forced varus on his knee in a slight flexion position. His right knee showed no apparent sway in the manual test, but pain around the fibular head was induced in the figure-of-four position, and the LCL could not be palpated. Joint instability was not detected on varus stress roentgenography, but magnetic resonance imaging showed signal changes and an abnormal course in the fibula head insertion at the distal part of the LCL. Although no instability was observed objectively, clinical findings diagnosed LCL as an isolated injury, and surgical treatment was performed. Six months after the operation, his symptoms improved, and he resumed competing in judo. Conclusion: To correctly diagnose an isolated LCL injury of the knee, it is important to consider patient history and physical findings. Repair of the injury could improve subjective symptoms, such as pain, discomfort, and balance instability, even if objective instability is not observed.

Comparison of the mechanical properties and mechanical damages to tendon tissue in three suspensory fixation techniques.

Background: Anterior cruciate ligament (ACL) injury is the most common traumatic injury to the knee joint. Suspensory fixation has become popular in ACL reconstruction because of its high primary stability, less invasiveness, and surgical convenience. There are two common types of suspensory fixation devices: those with fixed-length and those with adjustable-length loops. Owing to structural differences and differences in initial tensioning techniques, it is expected that mechanical property and damage to the tendons will vary from device to device; however, no literature has examined this so far. The main purpose of this study was to evaluate the damage caused to the tendon by three different suspensory fixation devices. An effective mechanical test was carried out as a prerequisite. Methods: First, the mechanical properties of simple loop device (SLD) as fixed-length loop device, first-generation, and second-generation adjustable devices (AD1 and AD2) as adjustable-length loop devices were tested (isolated device testing). Second, each device was tested using bovine extensor tendons (specimen testing). Cyclic testing included 2000 cycles; the devices were subsequently displaced until failure, and the ultimate tensile strength was determined using isolated device testing. Six samples of 3 devices were used in each testing experiment. After specimen testing, the surface structure of the tendon was evaluated quantitatively using optical coherence tomography (OCT) and our original histological scoring system. Results: During isolated device testing, SLD demonstrated the least cyclic displacement, followed by AD1 and AD2. The highest ultimate tensile strength was observed in AD2, followed by SLD and AD1. In specimen testing, the least cyclic displacement was observed in SLD, followed by AD1 and AD2. Histologically, AD1 demonstrated a significantly lower score, with damaged surface morphology, than SLD and AD2. OCT values were significantly higher, with a more disturbing tendon surface structure, in AD1 than in SLD and AD2. Conclusions: The first-generation adjustable loop device exhibited greatest graft tissue damage at the suspensory site in a clinically relevant setting. The thinner adjustable loop mechanism may have elevated graft damage by frictional stresses during loop adjustment or by repetitive tensioning stresses.