Tartrate-resistant acid phosphatase 5b and C-terminal telopeptides of type I collagen as markers for diagnosis of aseptic loosening after total hip replacement

Introduction

Plain radiography, bone scintigraphy, digital subtraction arthrography and various other techniques can be used to evaluate loosening of hip replacements. These methods are associated with radiation exposure and some of them have an increased morbidity. Furthermore, in some cases the results are not conclusive.

Method

The osteoclast biomarkers tartrate-resistant acid phosphatase 5b (TRAP 5b) and C-terminal telopeptides of type I collagen (CTX) in serum taken from 12 patients with aseptic loosening were measured. Serum samples from 24 other patients, 12 with an intact arthroplasty and 12 without any kind of joint replacement, served as control groups.

Results

The serum level of CTX was increased in comparison to the control groups, but the differences were not significant. In contrast, the increase in TRAP 5b in patients with aseptic loosening was highly significant (P < 0.001). A TRAP 5b value of 3.365 U/L was determined as a cut-off value, giving a sensitivity of 83.3% and specificity of 91.7% to differentiate the patients with aseptic loosening from those with an intact arthroplasty. Measurement of serum TRAP 5b may be a clinically relevant assay for monitoring patients after arthroplasty.