C-reactive protein as an early indicator of the formation of heterotopic ossifications after total hip replacement

The formation of heterotopic ossifications after total hip endoprosthesis implantation is a well-known complication. During the postoperative course laboratory parameters are subject to partial change due to the development of heterotopic ossifications. However, these changes occur relatively late at a time when the application of prophylactic precautions is usually already decided. Any meaningful prophylactic treatment, however, has to be initiated immediately after surgery. In a prospective study we assessed the postoperative C-reactive protein (CRP) levels in 95 patients twice after total hip replacement surgery. The initial assessment took place on the Ist day following surgery and again between the 5th and 7th day. All patients received three doses of 50 mg diclofenac daily for 7 days starting on the Ist postoperative day. Average CRP values on the Ist postoperative day were 6.33 +/- 2.28 mg/dl for ossification grade Brooker 0, 7.04 +/- 1.8 mg/l for Brooker 1 and 7.65 +/- 3.7 mg/dl for Brooker grades 2-4. At the time of the second CRP assessment (postoperative day 5-7), CRP values in the groups of patients showing ossifications were higher. Whereas patients without ossifications (A) exhibited an average level of 4.22 +/- 3.13 mg/dl, in patients with ossification grade 1 (B) CRP was 5.57 +/- 2.78 mg/dl and in the group with ossification grades 2-4 (C) was 6.38 +/- 4.48 mg/dl. The differences between group A on the one hand and the combined groups B and C values on the other were significant (P = 0.036). We are able to assert that after total hip replacement, significantly higher CRP levels can be recorded immediately after surgery in those patients who will eventually develop heterotopic ossifications, as compared with those who do not. Hence, the postoperative rise of CRP levels should be introduced as a further risk factor for the formation of heterotopic ossifications since its recording at such an early stage still allows for the timely initiation of prophylactic treatment.