Osteoarthritis (OA) is the most prevalent joint disorder associated with severe chronic pain. Although synovial inflammation is well correlated with pain severity, the molecular mechanism responsible for OA pain remains unclear. Here, we show that extracellular miR-21 released from synovial tissue mediates knee OA pain in surgical OA model rats. miR-21 was the most abundant among increased microRNAs (miRNAs) in the synovial tissue. miR-21 was released into extracellular space from the synovial tissue and increased in the synovial fluid. A single intra-articular injection of miR-21 inhibitor exerted long-term analgesia of knee OA pain, whereas miR-21 injection in naive rats caused knee joint pain. miR-21 mutant, which lacks the Toll-like receptor (TLR) binding motif, but not in the seed sequence, did not cause joint pain, suggesting a non-canonical mode of action different from translational repression. Consistent with this, the algesic effect of miR-21 was blocked by antagonizing TLR7. The TLR7 antagonist also exerted a long-lasting analgesic effect on knee OA pain. Therefore, extracellular miR-21 released from synovial tissue mediates knee OA pain through TLR7 activation in surgical OA model rats. Extracellular miRNA in the joint may be a plausible target for pain therapy, providing a novel analgesic strategy for OA.

Posterior cruciate ligament (PCL) resection during posterior-stabilized total knee arthroplasty (PS-TKA) has been reported to preferentially increase the tibiofemoral joint gap in flexion compared with extension. However, previous assessments of the joint gaps have been performed after bone resection and medial soft tissue release. Thus, these procedural steps may have the potential to influence soft tissue balance. In native knees, soft tissue laxity is generally greater in the lateral compartment than in the medial compartment both with the knee in extension and in flexion. Some surgeons may retain this natural soft tissue balance with less aggressive medial release during TKA. We performed this study to evaluate the impact of the PCL resection on the extension and flexion gaps in the absence of bone resection or medial soft tissue release. Tibiofemoral joint gaps for 41 patients (10 males and 31 females) in full extension and at 90 degrees of flexion both before and after the resections of both the anterior cruciate ligament (ACL) and PCL were assessed using a ligament tensioner device. The statistical analyze was performed using the Mann–Whitney U test. The results showed that medial gap in extension and flexion were 6.7 ± 1.0 and 7.3 ± 0.9 mm, and lateral gap in extension and flexion were 7.6 ± 1.1 and 8.4 ± 1.6 mm, respectively. Thus, physiological tibiofemoral gaps just after knee arthrotomy were trapezoidal and asymmetric shape with the significantly wider gaps in lateral and flexion, compared with the medial and extension, respectively (p < 0.05). However, the increases of the gaps with the ACL and PCL resections were less than 1 mm under the existence of medial soft tissues. As the medial collateral ligament is the primary restraint for the valgus instability, it was also considered to prevent the increase of the flexion gap although the PCL—which is the secondary restraint for the valgus instability—was resected. This finding is critically important for orthopedic surgeons applying PS-TKA implants, particularly for preserving soft tissues to achieve natural knee kinematics postoperatively.

These results revealed that varus insertion of femoral implants had no influence on short- to mid-term clinical outcomes because the pain score and ROM significantly improved in both the varus and non-varus groups. However, high rates of severe stress shielding appeared with varus insertion of femoral implants, suggesting an influence on long-term clinical outcomes.

Recent reports suggest that uncemented total hip replacement arthroplasty (THR) results in favorable short-to mid-term clinical results. In the present study, we assessed the mid-term clinical results of VerSys Hip System uncemented THR at our hospital. Materials and Methods:We studied patients who received THR using VerSys Hip System and who could be followed-up more than 3 years. Clinical records were used to retrospectively identify patient characteristics, which included age, gender, disease requiring THR, preoperative and postoperative pain score of the Japan Orthopaedic Association scoring system, range of motion in flexion and abduction, operating time, intraoperative complication, and additional operation or revision surgery. Additionally, we investigated the loosening and alignment of implants from X-ray films.Results: Ninety-one patients and 108 hip joints were investigated. Subjects were 11 males and 97 females (mean age, 64.6 years). Mean follow-up period was 6.9 years. Reasons for requiring THR were as follows: secondary osteoarthritis, 87 joints; idiopathic osteonecrosis of the femoral head, 16 joints; rapidly destructive coxarthrosis, 4 joints; and idiopathic ossification of the labrum, 1 joint. Mean operating time was 166 minutes. A total of 11 intraoperative fractures occurred, and wiring was performed in 3 of those cases. Adverse events pertaining to the surgery were limited; however, another adverse event was that 1 case resulted in intraoperative perforation of femoral cortex, for which a revision surgery was performed. There was no dislocation. Pain score using the Japan Orthopaedic Association scoring system and range of motion tests showed statistically significant improvement following THR. At the final follow-up, although no loosening of femoral implants was observed, the loosening of acetabular component was seen in 1 case. Varus insertion of femoral implant was recognized in 40 joints. Moreover, the average inclination angle of acetabular implants was 52.2 degrees. Conclusion:These data suggest that patients receiving VerSys Hip System uncemented THR demonstrate favorable results pertaining pain score and range of motion. However, high rate of intraoperative fracture and malalignment of implants, which may be at a risk of dislocation and/or polyethylene wear in future, suggests that this implant technique requires improvement. (J Nippon Med Sch 2016; 83: 184 187)

Compared with the conventional IMHS, the Asian IMHS is smaller, has increased variations in the shaft/neck angle of the lag screw, and has a titanium-alloy construction, allowing magnetic resonance imaging. The intraoperative fracture may have occurred because of the configuration of the distal interlocking screw in the Asian IMHS. Breakage of the implant likely occurred because the nail was too small in diameter, and too short in length for the unstable AO 31-A3 fracture. If careful attention is paid to the configuration of its distal interlocking screw intraoperatively and a nail of appropriate size is selected, the Asian IMHS is better suited than the conventional IMHS for treating Japanese patients, who generally have a small physique, because of its many variations in size and angle.