BACKGROUND: Bone marrow cell profiles are variable after total hip arthroplasty (THA), including variable levels of Stro-1+ and bone morphogenetic protein receptor (BMPRs)+ cells. We investigated the impact of bone marrow cell profiles on changes in periprosthetic bone mineral density (BMD) in uncemented THA patients.

MATERIAL AND METHODS: Bone marrow aspirates were collected from the metaphyseal region of discarded femoral heads from 24 consecutive THA patients (12 men and 12 women; mean age 66.7±11.0 years; range 52–87 years) treated from March 2009 to March 2011 at a single facility. Perioperative proportions of Stro-1+ and BMPR+ cells in femoral heads were assessed by flow cytometry. Follow-up examined the proximal femur Gruen zones R1 and R7 at 1 week and at 3, 6, and 12 months after THA, using dual-energy X-ray absorptiometry. Associations between BMD loss and age, gender, BMPRs+, and Stro-1+ were analyzed.

RESULTS: At 3 months, R1 and R7 BMD decreased by 4.4% and 6.4%, respectively (P<0.05). At 12 months, the overall BMD decreases in R1 and R7 were 10.2% and 1%, respectively (P<0.05). Higher Stro-1+ cells proportion predicted R7 BMD increases at all time points (P<0.05) and R1 BMD increases at 6 and 12 months (P<0.05). BMPR1a+ proportion was associated with BMD increases at 6 months in the R1 region. BMPR2+ was not significantly associated with BMD (P>0.05).

CONCLUSIONS: Elevated Stro-1+ bone marrow cell profile may be a useful prognostic indicator for uncemented THA patients.

Keywords: Osteogenesis, Absorptiometry, Photon, Arthroplasty, Replacement, Hip, Bone Morphogenetic Proteins, Aged, 80 and over, Antigens, Surface - metabolism, Bone Cements - therapeutic use, Bone Density, Bone Marrow Cells - pathology, Bone Morphogenetic Protein Receptors, Type I - metabolism, Bone Morphogenetic Protein Receptors, Type II - metabolism, Femur - radiography, Hip Prosthesis, Postoperative Care, Stromal Cells - pathology