We compared the biological characteristics of extrinsic fibroblasts infiltrating the patellar tendon with those of normal, intrinsic fibroblasts in the normal tendon in vitro. Infiltrative fibroblasts were isolated from the patellar tendons of rabbits six weeks after an in situ freeze-thaw treatment which killed the intrinsic fibroblasts. These intrinsic cells were also isolated from the patellar tendons of rabbits which had not been so treated. Proliferation and invasive migration into the patellar tendon was significantly slower for infiltrative fibroblasts than for normal tendon fibroblasts. Flow-cytometric analysis indicated that expression of alpha5beta1 integrin at the cell surface was significantly lower in infiltrative fibroblasts than in normal tendon fibroblasts. The findings suggest that cellular proliferation and invasive migration of fibroblasts into the patellar tendon after necrosis are inferior to those of the normal fibroblasts. The inferior intrinsic properties of infiltrative fibroblasts may contribute to a slow remodelling process in the grafted tendon after ligament reconstruction.

This study investigated the current incidence of hip fractures in Okinawa prefecture and compared the data with those obtained in our previous study, which was conducted using similar methods in 1987/1988. All patients, aged 50 years or older and residing in Okinawa, admitted to Okinawa hospitals in 2004 for a fresh hip fracture were identified from hospital registries. Details were obtained from the medical records and radiographs of all patients and classified according to fracture type (cervical or trochanteric), age, sex, and fracture location. Subtrochanteric fractures and pathological fractures were excluded. A total of 1,349 patients (242 men and 1,107 women) were admitted for a fresh hip fracture in 2004. Their average age was 76.9 years for men and 82.4 years for women. There were 671 cervical fractures, 654 trochanteric fractures, and 24 unclassified proximal femoral fractures. Comparing the data from 1987/1988 to those from 2004, the total number of hip fractures increased by 188%, from 469 to 1,349. The age-adjusted incidence rates per 100,000, standardized to the 2000 US population, were 75.7 and 296.1 in 1987/1988 and 123.6 and 420 in 2004 for men and women, respectively. The incidence rates in all age groups (at 5-year intervals) were higher in 2004 than in 1987/1988, indicating that people 50 years of age or older became more susceptible to hip fractures. Accordingly, the accretion of the hip fracture incidence rate was greater than that which could be explained purely by changes in population size and structure.

[Abstract]Background: After ligament reconstruction, mechanical deterioration of the grafted tendon is observed with revascularization and cellular proliferation. However, the effect of cellular proliferation on the mechanical properties of the tendon matrix has not been fully understood.Methods: Cultured fibroblasts derived from the rabbit patellar tendon were seeded around an acellular rabbit patellar tendon that had undergone freeze-thaw treatment. At time-zero, 3, and 6 weeks after seeding the cells, we evaluated cellular distribution in the tendon using a confocal laser microscope and the mechanical evaluations of the tendon fascicles and the tendon bundles. Findings:The confocal laser microscopic analysis showed fibroblast infiltration ex vivo into the acellular tendon matrix. We could not find significant effects of the cellular infiltration on the tangent modulus of the tendon bundle, although the ex vivo cellular infiltration significantly reduced the modulus of the tendon fascicle. In addition, the tangent modulus of the incubated tendon without fibroblasts significantly decreased with time, particularly in the tendon bundle levels. Interpretation:The findings of this study suggested that the effects of ex vivo cellular infiltration on the mechanical properties of the tendon bundles are relatively small, 2 compared with its striking effect on the tendon fascicles.

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