Physical environments play important roles for maturation of mechanical functions of tissue. In this study, effects of relative tribological movement on the expression of tribological function of regenerated synovial membrane were investigated. Fibroin sponge derived from silk was used as a three-dimension scaffold for the synovial membrane regeneration. Synovial cells were isolated from human synovial membrane, and were seeded onto the fibroin sponge. Magnetic stirring system (named Stirring Chamber) was used for culturing with relative slip motion where the cell-seeded side of the scaffold had been rubbed by a glass culture dish for 24 hours/day.

Histological view of regenerated tissue of the dynamically cultured group (D group) showed extracellular-matrix-like eosinophilic meshwork structure formed continuously on the meshwork structure of the fibroin sponge. The newly formed tissue showed expression of collagen type I, especially on the surface of fibroin sponge. These structures were not seen in the statically incubated group (S group). Each group didn’t show expression of collagen type II.

Frictional force was measured by using leaf spring method under the conditions of the sliding velocity: 0.8 mm/s, the loading time prior to sliding: 1 minute, and the applied load during the experiment: 0.029 N. The counterface for regenerated synovium was a flat stainless steel of which roughness was 0.06 μm Ra. All frictional experiments were performed in the saline solution and at room temperature (25°C). The friction coefficient of tissues cultured statically was 0.6–0.8, and that of tissues cultured with sliding motion was 0.2–0.4 at one week culturing, 0.3–0.5 at two weeks culturing.

Our previous experiment showed that combination of fibroin-sponge scaffold and Stirring-chamber culturing system improved the tribological performance of regenerated cartilage tissue. The present study suggests that this combination have also a possibility for synovial cells to form functional lubricious membrane which can be used as anti-adhesion membrane for knee, ligament, and/or other surgical procedures. However, the deterioration of lubrication properties in the 2 weeks dynamically cultured group would indicate that the too long continuous tribological movement does not provide an optimal condition. More fine tribological loading history should be designed.

The purpose of this study is to call attention to the diagnosis of spinal cyst caused by lumbar disc herniation. Reviewing a total of 11 cases of lumbar spinal cyst that have been encountered in our spinal practice, we propose our views concerning the pathology of this lesion.

The clinical findings of lumbar spinal cyst are identical to those in acute disc herniation such as low back pain and radiculopathy. The characteristics of imaging study are as follows; The magnetic resonance imaging (MRI) demonstrates a relatively large, rounded mass postero-laterally to the vertebral body. These lesions are isointense relative to the intervertebral disc on T1-weighted images and homogeneously hyperintense on T2. A gadolinium -DTPA-enhanced MRI shows a rim-enhancing lesion. A discogram reveals leakage of the contrast medium into the mass.

The operative findings demonstrated encapsulated soft tissue masses which contained bloody fluid and small fragments of herniated disc tissue. The pathologic examinations revealed fibrous tissue with hemosiderin deposit in cyst wall and degenerative disc materials with inflammatory cell infiltration.

This type of lumbar spinal cyst has been recognized as spinal epidural hematoma in recent years. Wiltse suggested that epidural hematoma may result from tearing of fragile epidural veins due to acute disc disruption. However, MRI characteristics of hematoma are not identical with those with lumbar spinal cyst. It is more likely that the lesions showing the pattern of changes are herniated disc tissue accompanied by hemorrhage and inflammation. If hernial tissue is covered with some membranous susbtance, formation of cystic lesions is understandable. Hence, we hypothesize that lesions, in which lysis liquefaction and absorption of the herniated disc tissue associated with inflammatory response have progressed, and the herniated disc tissue has completely disappeared, may be filled solely with bloody fluid, showing an appearance like cysts.