Prospective Evaluation of Biomarkers Variability in Knee Prosthetic Surgery

Aseptic implant loosening after TKR causes knee pain, reduces knee function and may require revision surgery.

Several proteins have been identified, which are involved in bone metabolism and remodelling; variations in serum levels of some of these proteins after TKR loosening have also been described.

However, preoperative identification of risk factors for aseptic loosening remains a challenge.

An observational study is conducted to evaluate how levels of the following serum biomarkers vary after TKR:

• osteoprotegerin (OPG)
• receptor activator of nuclear factor kappa-B (RANK)
• receptor activator of nuclear factor kappa-B ligand (RANK-L)
• sclerostin
• cathepsin K

To avoid bias caused by inflammatory states, C reactive protein (CRP), interleukin 1 (IL-1), interleukin 6 (IL-6), tumor necrosis factor α (TNF-α) levels and erythrocyte sedimentation rate (ESR) will be measured.

Secondary goals are to evaluate the mRNA expression of OPG, RANK-L, cathepsin K and sclerostin on tibial bone biopsies and to study if changes in serum biomarkers levels after surgery are associated with:

• clinical outcomes
• periprosthetic bone density
• variation of two bone reabsorption markers, the postoperative change of which has already been described in details: type 1 collagen cross-linked C-terminal telopeptide (CTP1) and type 1 procollagen N-terminal telopeptide (P1NP).

One day before surgery, after having signed informed consent, patients will undergo a vertebral and femoral dual-energy X-ray absorptiometry (DEXA) scan and blood samples will be collected.

During surgery a tibial biopsy will be collected. Between 4 and 7 days postoperatively and 3, 6 and 12 months after surgery patients will again undergo periprosthetic DEXA scans and blood samples will be collected.