Effect of pregnancy on joint contracture in the rat knee.

As there is evidence that ligamentous laxity is affected by the female hormones, we hypothesized that hormonal changes occurring during pregnancy could have a therapeutic role in preventing the development of a joint contracture. Knee joint contractures were created in pregnant and nonpregnant rats. After 2 wk of immobilization, the degree of contracture was measured with structural properties of the medial collateral and anterior cruciate ligaments and the pubic symphysis. Although not statistically significant, there was a general trend toward reduced contracture in pregnant compared with nonpregnant rats. Cutting the posterior capsule significantly decreased contracture for both the pregnant and nonpregnant groups, confirming the contribution of capsular structures to contracture. Ultimate loads of the medial collateral and anterior cruciate ligaments significantly decreased after immobilization compared with control, but there was no significant effect due to pregnancy. Stiffness and ultimate load of the pubic symphysis were not significantly different between pregnant and nonpregnant groups. The trend toward reduced contracture with pregnancy points toward a possible therapeutic role for female hormones in the prevention of postoperative and/or posttraumatic joint contracture.

Cell motility in a new single-cell wound model.

Until now researchers have used a monolayer of cultured cells to investigate cell motility toward an injured cell. However, we suspect that, when using this method, adjacent cells move to the free space due to relief of contact inhibition. The current study was designed to investigate the cell motility nearby an injured cell in varying cell connectivity. A low-power laser beam was used to damage one cell selectively with the silver coating beads. After injury, we observed the cell motility in three different cell types: (1) those immediately adjacent to the injured cell, (2) those removed from the injured cell by interposition of another cell, and (3) those removed from the injured cell by free space. The cells that are in direct contact with the injured cell moved toward the injured cell within 1.5-3.0 h. Indirectly connected cells and cells with no contact, on the other hand, showed no significant movement toward the injured cell. This suggests that the cell motility toward the cell injury is not only due to relief of contact inhibition but might also be caused by cell-to-cell signaling via cell connection. The current method will provide a tool to create a cell injury without damaging adjacent cells.

Influence of the vitamin D receptor alleles on human osteoblast-like cells.

We investigated the effect of vitamin D receptor gene (VDRG) polymorphism on the responsiveness to 1,25(OH)2D3 in human osteoblast-like cells. The cells were obtained from the femoral heads of 18 women with osteoarthritis of the hip. Three different restriction enzymes, BsmI, ApaI, and TaqI, were used to analyse the polymorphism. The genotypes of the 18 patients were bbAaTT (8), bbaaTT (6), BbAaTt (3), and BbAATt (1). Our findings showed that there were no differences according to the VDR genotype, but there was a statistically significant difference in the production of osteocalcin between BbAaTt and bbAaTT, and between BbAaTt and bbaaTT. Northern blot analysis of osteocalcin and VDR mRNA showed no significant differences among the three VDR genotypes. These findings suggest that VDR gene polymorphism affects the individual responsiveness of 1,25(OH)2D3.

Effects of periosteum wrapped around tendon in a bone tunnel: A biomechanical and histological study in rabbits.

The present study demonstrated the effects of periosteal autograft on tendon-to-bone healing in the rabbits. In 20 Japanese white rabbits, proximal end of the long digital extensor tendon that was wrapped around by a periosteum was transplanted into a drill hole in the proximal tibial metaphysis. A fresh periosteum was used in the left tibia and a frozen periosteum was used in the right tibia. Six specimens were harvested at each 2, 4, and 6 weeks postoperatively. Radiological features showed progressive remodeling of trabecular bone surrounding the implanted tendon. This remodeling in fresh periosteal graft was earlier than that in frozen graft. Generally, the pull-out strength of the transplanted tendons with a fresh or frozen periosteum increased progressively according to the length of the healing periods. The strength was significantly greater in a fresh periosteal graft than that in a frozen graft at 4 weeks postoperatively. In histological analysis, a 4-week specimen with the fresh periosteal graft showed fibrocartilage formation in the bone tendon interface, whereas the specimens with the frozen graft demonstrated simple approximation of oriented fibrous tissue. In conclusion, the fresh periosteal autograft produced the premature form of fibrocartilagenous attachment in a bone tunnel and provided good mechanical strength.

Restoration of tensile properties at tendon insertion to bone by a patellar tendon-tibia autograft: an experimental study with canine infraspinatus.

A free patellar tendon-tibia autograft was performed to reconstruct a tendon insertion to bone of the canine infraspinatus. In this experimental study restoration of mechanical properties at tendon insertion to bone of the patellar tendon-tibia autograft was examined on 0, 42, and 84 postoperative days. Five dogs were used for each time point. Bone union occurred in all grafts by 6 postoperative weeks. The ultimate strength at the tendon insertion to bone recovered from 255.5 N on 0 day to 264.3 N and 439.3 N on 42 and 84 postoperative days, respectively. Stiffness recovered from 141.8 KN/m on 0 day to 201.8 KN/m and 226.3 KN/mN on 42 and 84 postoperative days, respectively. Our results demonstrate that patellar tendon-tibia autograft maintains excellent mechanical properties at tendon insertion to bone in the early healing period. This result suggests that transfer or free graft of tendons with attaching bone plug has a mechanical advantage for reconstruction of the rotator cuff, which may allow the patient to institute early postoperative mobilization.