Effects upon bone metabolism following total hip and total knee arthroplasty

In a prospective study we evaluated the course of markers for bone formation and bone resorption in patients undergoing elective total hip and total knee arthroplasty due to osteoarthritis. The aim was to evaluate which changes in bone metabolism take place in the immediate postoperative course following arthroplasty.

Serum and urine samples were obtained preoperatively and in the postoperative course from patients undergoing total arthroplasty over a 90- or 180-day period. The study included a total of 63 patients with cemented hip prostheses (n = 20), uncemented hip prostheses (n = 23) and cemented knee prostheses (n = 20). Different biochemical markers of bone metabolism were assessed including the serum markers bone-specific alkaline phosphatase, and carboxyterminal propeptide of type I procollagen, and the urine markers n-telopeptide (NTx) and deoxypyridinoline (DPD).

For all four markers, there were changes over time which were statistically significant. Markers indicating bone formation were slightly elevated after a 3-month period. In contrast, the two markers indicating bone resorption were back to normal after a 6-month period. There were differences between the groups with cemented and uncemented total hip arthroplasty in the postoperative course with higher values of the markers indicating bone resorption in the cemented group. However, these differences were not statistically significant.

Our results indicate that the two markers of bone resorption, NTx and DPD, are elevated during the first 6 months after hip and knee arthroplasty. Therefore, during this period they cannot be used as a marker for aseptic loosening. However, if these two markers are still elevated after this period, they may reflect an impaired bone metabolism. Further studies are required to assess the potential value of these markers for the diagnosis of aseptic loosening.