<i>In vitro</i> osteogenic capacity of bone marrow MSCs from postmenopausal women reflect the osseointegration of their cementless hip stems.

Abstract

Age-related dysfunction of mesenchymal stromal cells (MSCs) is suggested as a main cause of altered bone repair with aging. We recently showed that in postmenopausal women undergoing cementless total hip arthroplasty (THA) aging, low bone mineral density (BMD) and age-related geometric changes of the proximal femur are risk factors for increased early migration and delayed osseointegration of the femoral stems. Extending these analyses, we have here explored how the <i>in vitro</i> osteogenic capacity of bone marrow MSCs from these patients reflects implant osseointegration, representing the patient's <i>in vivo</i> bone healing capacity. A total of 19 postmenopausal women with primary hip osteoarthritis (mean age 65 years, range 50-78) and well-defined bone quality underwent successful preoperative <i>in vitro</i> analysis of osteogenic capacity of iliac crest bone marrow MSCs as well as two-year radiostereometric (RSA) follow-up of femoral stem migration after cementless THA. In patients with MSCs of low osteogenic capacity, the magnitude of cumulative stem subsidence after the settling period of three months was greater (<i>p</i> = 0.028) and the time point for translational osseointegration was significantly delayed (<i>p</i> = 0.030) compared to patients with MSCs of high osteogenic capacity. This study suggests that patients with MSCs of low <i>in vitro</i> osteogenic capacity may display increased stem subsidence after the settling period of 3 months and thereby delayed osseointegration. Our study presents a novel approach for studying the biological progress of hip implant osseointegration and to verify the impact of decreased MSCs function, especially in patients with age-related dysfunction of MSCs and bone healing capacity.