Plasma levels of platelet-derived growth factor BB and transforming growth factor in patients with failed hip prostheses

Background The role of growth factors in prosthesis loosening is unclear. We evaluated the levels of plate-let-derived growth factor BB (PDGF-BB), transforming growth factors β1 (TGF-β1) and β2 (TGF-β2), both before and after activation, in patients with aseptic loosening of their hip prosthesis.

Patients and methods 26 patients with loosened hip implants were compared with 21 patients who had stable hip prostheses, and 28 patients undergoing primary hip replacement. The plasma levels of the growth factors were analyzed by enzyme immunoassay. TGF-β1 and TGF-β2 were determined both before and after activation.

Results Patients with aseptic loosening had significantly lower PDGF-BB levels than patients undergoing primary hip replacement, and significantly lower TGF-β2 levels than patients with a stable implant. Patients with stable prostheses had significantly higher TGF-β1 and TGF-β2 levels than patients undergoing primary hip replacement.

Interpretation It is possible that the prosthetic implant itself causes a local increase in PDGF-BB, TGF-β1 and TGF-β2, released by osteoblasts and other cells in the microenvironment. The plasma PDGF-BB measured does not correspond to local release, which is probably due to local consumption or degradation. The consumption of PDGF-BB is low in stable implants, and TGF-β1 and TGF-β2 levels increase during bone formation. In loosening, PDGF-BB consumption is higher and causes a significant reduction in plasma levels as compared to presurgery. The formation of poor-quality bone may be related to the scarce increase in TGF-β1 and TGF-β2. In conclusion, compared with patients with a stable implant, a reduction in bone-forming growth factors appears to occur in individuals with aseptic loosening.