Masaki Sonoda

Quantitation and localization of cartilage degeneration following the induction of osteoarthritis in the rabbit knee

OBJECTIVE To develop and apply a new video imaging technique to quantify and localize Indian ink staining of cartilage of the rabbit femorotibial joint after the induction of osteoarthritis by unilateral transection of the anterior cruciate ligament (ACLT). METHODS Nine weeks after surgery, femora and tibiae from 11 ACLT and contralateral control knees were harvested and positioned to obtain calibrated gray-scale images of the ink-painted articular cartilage surfaces that are opposed with the knee in 90 degrees flexion. Images were processed so that areas of normal cartilage gave a relatively high reflectance score, whereas ink-stained fibrillated cartilage and exposed bone gave low scores. RESULTS Comparison of the medial and lateral femoral condyles and tibial plateaus (MFC, LFC, MTP, LTP) of control and ACLT knees showed that the area of the MTP not covered by the meniscus had a significantly lower reflectance score (P < 0.001) than other areas. ACLT led to an 11% decrease (P < 0.001) in the overall reflectance score. The reflectance score decreased as a traditional morphological grading of degeneration increased. ACLT-induced degeneration had a predilection for the posteromedial aspects of the joint, and to a lesser extent, the anterolateral aspects. In the tibial plateaus, ACLT caused significant degeneration in the covered, but not the uncovered, areas. Image scores of opposing cartilage surfaces (i.e., MFC vs MTP and LFC vs LTP) were significantly (R = 0.56-0.70, P < 0.001) correlated in ACLT and control knees. DISCUSSION Identification and characterization of cartilage areas prone to degeneration may be particularly useful for further analysis of biochemical and biomechanical mechanisms in osteoarthritis, as well as the efficacy of therapeutic interventions.

The Effects of Hyaluronan on Tissue Healing After Meniscus Injury and Repair in a Rabbit Model

To assess the effect of hyaluronan on meniscus injury and repair, we had 35 mature New Zealand White rabbits undergo bilateral meniscus injury and repair (19 in the peripheral region, and 16 in the inner region). A longitudinal tear was created in the medial meniscus and repaired with horizontally placed nylon sutures. The left knee joint received intraarticular injections of hyaluronan 1 week after surgery and once a week for 5 weeks. The right knees were injected with phosphate-buffered saline (the carrier vehicle of the hyaluronan). Twelve weeks after repair, tears in the peripheral region showed gross and histologic evidence of healing, with no difference between the vehicle- and hyaluronan-treated menisci. Biochemically, the ratio of reducible collagen cross-links in the hyaluronan-treated menisci was significantly higher than in the vehicle-treated menisci, indicating greater level of collagen remodeling. Biomechanically the vehicle- and hyaluronan-treated menisci demonstrated similarly high tearing load and fracture toughness. In the inner region, poor healing response was observed grossly and histologically in both treatment groups. Water content in the hyaluronan-treated menisci was significantly lower than in the vehicle-treated menisci, indicating a lower level of swelling. Hyaluronan treatment stimulated collagen remodeling in the peripheral region and inhibited swelling of the meniscus repaired in the inner region.

The Effects of Hyaluronan on the Meniscus and on the Articular Cartilage After Partial Meniscectomy

The effect of hyaluronan (molecular weight = 8 × 105) on the meniscus and on the articular cartilage was assessed after partial meniscectomy in a rabbit model. On gross examination, remodeled meniscus appeared as newly synthesized translucent tissue, and was seen in both vehicle- and hyaluronan-treated menisci. His tologically, safranin O staining revealed the strong presence of glycosaminoglycans in the newly remod eled tissue, and polarized light demonstrated the ab sence of mature collagen architecture. Hydration of the hyaluronan-treated menisci was significantly less than that of the vehicle-treated menisci, and the reducible collagen cross-link dihydroxylysinonorleucine was sig nificantly increased in the hyaluronan-treated menisci compared with the vehicle-treated menisci, indicative of a greater degree of collagen remodeling. In situ hybridization of vehicle- and hyaluronan-treated me nisci revealed a high level of type I procollagen mRNA expression and minor expressions of types II and III mRNA. Expression of the type I collagen gene ap peared to be more pronounced in the hyaluronan- treated menisci than in the vehicle-treated menisci. The tibial plateaus revealed mild cartilage fibrillation after partial meniscectomy. A statistically significant difference between vehicle- and hyaluronan-treated cartilage was not demonstrated in the present study because of the slow development (i.e., 12 weeks) of osteoarthritis after partial meniscectomy in the rabbit model. These results suggest that in the rabbit model, hyaluronan enhances collagen remodeling and inhibits meniscal swelling after partial meniscectomy in the avascular region.

Correlation Between Knee Laxity and Graft Appearance on Magnetic Resonance Imaging After Double-Bundle Hamstring Graft Anterior Cruciate Ligament Reconstruction

Background In recent years, double-bundle (anteromedial bundle [AMB], posterolateral bundle [PLB]) anterior cruciate ligament reconstruction has developed into an accepted practical surgical procedure; therefore, its efficacy needs to be established. Hypothesis Multiple-sliced 2-dimensional magnetic resonance imaging allows evaluation of each bundle separately. Both bundles are important for knee stability, and each bundle has a role in the prevention of knee instability. Knee laxity testing will correlate with the magnetic resonance imaging appearance of the individual graft bundles. Study Design Cohort study; Level of evidence, 2. Methods A total of 97 double-bundle anterior cruciate ligament reconstructions were evaluated 1 year after surgery, including side-to-side difference of KT-2000 arthrometer and pivot shift test. T2-weighted 2-dimensional magnetic resonance images were captured in the middle plane of each bundle to express magnetic resonance signals of each bundle. The magnetic resonance signals were divided into 3 grades: grade I, low-intensity signal; grade II, high-intensity signal within 50%; and grade III, high-intensity signal greater than 50%. Results Anterior laxity in AMB grade II (PLB I, 3.5 ± 1.7 mm; PLB II, 4.5 ± 1.9 mm) was significantly larger than in AMB grade I (PLB I, 1.9 ± 1.7 mm; PLB II, 2.1 ± 1.7 mm) with statistical difference (P = .025 in PLB I; P = .002 in PLB II). A positive rate in pivot shift test in PLB II (48%) was significantly larger than in PLB I (21%) with statistical difference (P = .031). Conclusions Varying magnetic resonance signals according to the bundle indicate role differences of each bundle in knee stability. These results imply that the AMB has a major role in preventing anterior translation of the tibia and the PLB has a major role in preventing anterolateral rotatory instability.