Figure-4 Patient Positioning Increases Medial Meniscus Extrusion on Ultrasound in Patients With Posterior Medial Meniscus Root Tears of the Knee.

Purpose: To compare the degree of medial meniscal extrusion (MME) between knees with medial meniscus posterior root tear (MMPRT) and degenerative tears of the medial meniscus using ultrasonography (US) in different limb positions and to identify the findings characteristic of MMPRT. Methods: The study group comprised 25 subjects with MMPRT (group RT), 25 subjects with degenerative medial meniscal tears (group D), and 25 knees with no abnormalities of the medial meniscus (MM) on magnetic resonance imaging (MRI) (group C) whose age was ≥40 years. MME was evaluated using US in the supine, figure-4, feet-dangling, and standing positions. The MME was evaluated by the actual measurement values and the relative values to the MME in the supine position. The differences in the MME among the 3 groups in each limb position were analyzed using one-way analysis of variance. P < .05 was considered significant. Results: The actual MME values were largest in group RT in all 4 limb positions. When changing the limb position from the supine to the figure-4, the actual MME increased from 3.8 ± 0.8 mm to 5.5 ± 1.3 mm in group RT, whereas it decreased from 3.4 ± 1.1 mm to 1.8 ± 1.2 mm in group D, showing the most significant difference in MME of the figure-4 position between the 2 groups (P < .001). In group RT, 88% of knees had the maximum MME in the figure-4 position. In group D, 60% of knees had the maximum MME in the standing position and only 2 knees (8%) had the maximum MME in the figure-4 position. Conclusions: The increase in MME from the supine to the figure-4 position was a characteristic finding of MMPRT but not degenerative tears. Level of Evidence: Level III, case-control study.

Histologic classification of loose bodies in osteoarthrosis.

BACKGROUND: Histologically based analyses of the nature and origin of loose bodies occurring in osteoarthrosis have been few, and further study is warranted. METHODS: We histologically examined 84 loose bodies and 9 related lesions (synovial membrane nodules) surgically removed from 24 joints of 24 patients with osteoarthrosis. RESULTS: The 84 loose bodies included 48 chondral loose bodies (type I), 26 osteochondral loose bodies (type II), and 10 osseous loose bodies (type III). The 26 osteochondral loose bodies (type II) could be subdivided into 8 composed of cartilage with enchondral ossification (type IIa), 11 consisting of mature bone covered by cartilage without enchondral ossification (type IIb), and 7 made up of mature bone and partially articular cartilage or hyaline cartilage (type IIc). Synovial membrane nodules could be also divided into three types in the same manner as loose bodies. Many type IIa, type IIc and type III loose bodies and all synovial membrane nodules showed blood vessels containing red blood cells, as well as osteoclasts. The type I and type IIb loose bodies, however, did not show them. CONCLUSIONS: It is well known that loose bodies grow from proliferation of cartilage without blood supply in the joint cavity, and that enchondral ossification is able to develop only under the condition of having a blood supply. As synovial membrane nodules were also classified to the same types as loose bodies and more than half of osteochondral and osseous loose bodies contained blood vessels with red blood cells, the loose bodies were thought to be caught in the synovial membrane and to be modified as the result of a blood supply. Considering the results of this study, the various histologic characteristics of loose bodies in osteoarthrosis resulted from modifications including cartilage proliferation in the joint cavity and enchondral ossification in the synovial membrane.

Encapsulation of chondrocytes in photopolymerizable styrenated gelatin for cartilage tissue engineering.

We have developed a photopolymerizable styrenated gelatin that can cross-link through polymerization induced by irradiation with visible light. The purpose of this study was to investigate the feasibility of using photopolymerizable styrenated gelatin as a cell carrier in chondrocyte transplantation. As visible light activates camphorquinone added as a photoinitiator, free radicals induce the polymerization of the gelatin macromer; the styrenated gelatin then becomes cross-linked. Rabbit articular chondrocytes were cultured in styrenated gelatin hydrogels and also in collagen gels as a control. After being cultured in the gels, the cells were collected from both gels and counted. Reverse transcriptase-polymerase chain reaction, histological examination, and quantification of the synthesized glycosaminoglycan were performed. On average, 26% of the embedded cells were collected from the gelatin hydrogel immediately after the crosslinking reaction. The surviving chondrocytes expressed the mRNA of type II collagen and aggrecan core protein and produced a cartilaginous matrix throughout the gelatin after 3 weeks. A slightly insufficient accumulation of the matrix was found in the internal region of the gelatin hydrogels, suggesting that less permeability for nutrients due to the high concentration and closely packed structure resulted in less cell viability. Although some limitations became evident, these results indicate that it may be possible to use photopolymerizable styrenated gelatin as a cell carrier in chondrocyte transplantation.