OBJECTIVESTo analyze retrospectively the formation and histological changes of sclerosis rim in patients with osteonecrosis of the femoral head (ONFH), and to study the relationship between bone morphogenetic proteins (BMP4) and sclerosis rim, so as to acquire experimental and theoretical basis on individualized treatment for ONFH patients.

METHODSFrom November 2005 to November 2007, 184 hips of steroid-induced ONFH inpatients were collected. The mean age was (47 ± 7) years, the patients were divided into high (more than 54 years old), middle (40 - 54 years old) and low (less than 40 years old) age groups. Their clinical data were analyzed retrospectively according to gender and age. Parts of the femoral heads were selected for the study, including 18 hips in high age group, 11 hips in low age group and 20 hips in middle age group. Each 10 hips were selected with or without sclerosis rim. The femoral heads were cut along middle coronal plane, their weight-bearing and non-weight-bearing areas were used for the study. The specimens were processed by routine HE staining and picric acid-Sirius red staining and electron microscopy preparation and immunohistochemistry stain. The average optical density of BMP4 protein was calculated by image analysis software.

RESULTSThe trabecular of sclerosis rim was thickening and disorder. But its osteocytes were normal and with high secretion. The ratio of sclerosis rim was 71.4% (105/147) in middle age ONFH patients, which was significantly higher than the low age group patients (45.5%, 5/11) and high age group patients (38.5%, 10/26) (P < 0.01). The optical density of BMP4 in middle age ONFH patients was 0.32 ± 0.14, which was significantly higher than the low age group 0.20 ± 0.17 and high age patients 0.19 ± 0.27 (P < 0.05). The optical density was 0.16 ± 0.11 in ONFH patients without sclerosis rim, which was significantly lower than with sclerosis rim (0.28 ± 0.13) (P < 0.01). The time from hip pain to joint replacement in patients with sclerosis rim was (49 ± 11) months, and (15 ± 2) months without sclerosis rim. There was significant difference between the two groups (P < 0.01).

CONCLUSIONSThe formation of sclerosis rim is positively related to the expression of BMP4, and high expression of BMP maybe promote the formation of sclerosis rim.