Is tartrate-resistant acid phosphatase 5b a potent bio-marker for late stage aseptic implant loosening?

Aseptic loosening is a serious complication after total joint arthroplasty. Plain radiography, along with clinical signs of prosthesis loosening, is the technique of first choice to evaluate loosening of joint replacements. Nevertheless, radiographical signs of osteolysis may not be apparent until progressed stages of loosening. Thus the search for alternative diagnostic methods is of great importance. The purpose of the present study was to evaluate the potential diagnostic significance of TRAP 5b, Osteocalcin, CrossLaps and Bone ALP for aseptic loosening of total joint replacements.Thirty-seven patients (25 women, 12 men, mean age 65 years, age range 54-76 years) treated with revision surgery due to clinically and radiologically confirmed late aseptic prosthesis loosening were examined prospectively. Serum levels of TRAP 5b, Osteocalcin, CrossLaps and Bone ALP were compared with a matched control group (n = 39).We found a significant decrease in TRAP 5B level in patients with aseptic loosening. Bone ALP and Osteocalcin as markers of osteoblast activity, and CrossLaps as another resorption marker did not allow any prediction of bone remodeling in this late phase of loosening.In the "late" phase of aseptic joint replacement loosening, no increase of TRAP 5b and therefore no increase of osteoclast number and activity was measurable. Thus, in this situation an anti-osteolytic therapy with a bisphosphonate or denosumab would not gain any further benefit.