Background/objective: Formation of heterotopic ossification (HO) in soft tissue after spinal cord injury (SCI) is associated with various degrees of inflammation. Recent studies have shown that inhibition of inflammatory reaction with nonsteroidal anti-inflammatory drugs is an effective prevention of HO after SCI. The goal of this study was to monitor the activity of the most widely used indicators of acute inflammation--namely, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)--in patients with HO.
Methods: In a retrospective study, the results of 37 patients with HO were evaluated. There were 25 patients with tetraplegia and 12 with paraplegia. The age (mean +/- SD) of the patients was 28 +/- 8 years (range = 19-46 years). The patients were admitted to the rehabilitation center 2 to 5 weeks after SCI. HO was confirmed by bone scintigraphy. Blood samples were obtained from the patients at the time of diagnosis of HO and during the therapy. ESR was measured with the Westergren method, and serum CRP was determined by enzyme-linked immunosorbent assay.
Results: In the acute stage of HO, both tests were elevated in all patients. In the later stages when clinical signs and symptoms of inflammation were resolving, both tests showed a gradual decline. When clinical signs and symptoms of inflammation (fever, acute soft tissue swelling, and erythema) were not present, the concentration of CRP was normal in 91.2% of patients, whereas only 17.6% of patients had normal ESR. Mean serum concentrations of CRP were 8.9 +/- 5.6 mg/L in the inflammatory phase and 0.9 +/- 0.6 mg/L in the noninflammatory phase.
Conclusion: The data indicate that serum CRP is a useful and more specific test than is ESR for monitoring the inflammatory activity of HO after SCI. The normalization of CRP was seen during the first 3 to 4 weeks of etidronate therapy, indicating a resolution of acute-phase inflammatory reaction.