BIOCHEMICAL-ANALYSIS OF HETEROTOPIC OSSIFICATION IN SPINAL-CORD INJURY PATIENTS

Heterotopic ossification (HO) represents a frequent complication in sp inal cord injury (SCI) patients. Samples of HO taken from SCI patients were studied and compared to normal bone. We used a procedure of bone particle fractionation (according to their degree of mineralisation) which allowed us to establish a profile reflecting the metabolic remod elling of bone and to analyse the organic matrix of the newly synthesi sed tissue. In paraplegic patients, we noted that there was a large in crease of the proportion of a degree of calcified bone in the HO as we had previously observed in cortical as well as in cancellous bone of the same patients. Based on aminoacid analyses, we observed in the new ly synthesised organic matrix of HO a decreased proportion of hydroxyp rolyl residues resulting either from an alteration of the prolyl hydro xylation or from the presence of an excess of non-collagen polypeptide s. These results are similar to those seen in sublesional bone of the SCI patients. This study demonstrates that HO is a newly formed bone w hich has a high rate of turnover as is seen in growing bone. This must be taken into account for the treatment of the patients.