Different magnetic resonance imaging features in two types of nontraumatic rabbit osteonecrosis models

Relation between the development of osteoporosis and osteonecrosis following glucocorticoid in a rabbit model

BACKGROUND

There has been a recent increase in the number of patients suffering from bone and joint diseases, as a consequence of corticosteroids administration. There are more patients treated with low dose of GCs under long-term conditions in clinical, such as effect of GCs on Rheumatoid arthritis, Crohn's disease and Asthma patients. Hence, it was difficult for doctor to determine which problem occur first - OP or ON; however, there was no clinical report previously in the literature, and there was no effective animal model of OP and ON about low dose GCs. This study was conducted to develop rabbit models of glucocorticoid (GC)-induced femoral head ON and OP and to investigate the temporal relationship between the occurrence of the two events following administration of glucocorticoids.

MATERIALS AND METHODS

Fifty six, 6 months old female rabbits were randomly divided into the GC group and control group (C). Rabbits received gluteal injections of methylprednisolone sodium succinate once a day for 4 weeks, while normal saline solution in the control group. Rabbits were sacrificed at 0, 2, 4, and 8 weeks. Hip magnetic resonance imaging was performed before the rabbits were sacrificed. Serum calcium (Ca), phosphorus (P), total cholesterol, and triglyceride levels were also measured. The bone mineral density (BMD) of femoral head and the femoral shaft were measured by dual-energy X-ray absorptiometry. The trabecular parameters of the femur and the 4(th) lumbar vertebrae (L4) were measured with a micro-computed tomography (μ-CT). Also, the femoral head was stained with hematoxylin-eosin staining.

RESULTS

At 4 weeks in the GC group, the BMD of the femur reduced 33% and 22% in the femoral head and shaft; there was irregular intermediate to high T2-weighted images signals; μ-CT showed microfractures and cystic changes in the femoral head and L4 at 4 weeks. At 8 weeks in the GC group, the classical "line-like sign" indicating ON of the femoral head was observed in 64.3% of the rabbits.

CONCLUSION

A rabbit model of GC-induced OP and ON was developed by repetitive injection with small doses of GCs in the gluteal region. OP was observed at 4 weeks while ON developed at 8 weeks and followed a clear temporal pattern.

Avascular necrosis of the femoral head in patients with Hodgkin's disease

Avascular necrosis of the femoral head (ANFH) is a rare complication that may occur in patients diagnosed with Hodgkin's Disease (HD), as a result of treatment. A review was made of 315 cases of HD treated with systemic chemotherapy associated with high doses of steroids and radiation therapy and 18 patients (5.71%) were found to have developed ANFH during treatment. The mean follow-up time for chemotherapy was 40 months (range 20-110 months) with an average dose of prednisone of 8.45 g (range 3.20 - 18.50). The patients were treated by simple forage, simple forage plus IES and total hip arthroplasty (THA). In 8 cases (44.44%) forage associated with IES was performed as the initial treatment option and 6 of these cases were found to be in Ficat stage II (75%), 1 was found to be in stage III (12.55%) and another in stage IV (12.5%). In 2 cases, the central decompression technique was used (Simple Forage); both were in Ficat stage II. In the other 8 cases, a total hip arthroplasty (THA) was chosen as the initial treatment option, with 3 of these patients in Ficat stage III and 5 in Ficat stage IV. The clinical outcomes (time to postoperative pain, time to radiological failure, and time to arthroplasty from the forage) following surgical management using the forage-biopsy technique with and without internal electrostimulation (IES) were recorded. We observed that treatment with Forage + IES was better than simple Forage in stages below III in patients with Hodgkin's Disease. We considered that in Ficat stage III and IV arthroplasty (THA) was the better option. Steroids do not appear to be the only factor that worsens the outcomes of the parameters tested, and, in our opinion, other associated factors exist.

Experimental animal models of osteonecrosis

Osteonecrosis (ON) or avascular necrosis (AVN) is a common bone metabolic disorder, mostly affecting femoral head. Although many biological, biophysical, and surgical methods have been tested to preserve the femoral head with ON, none has been proven fully satisfactory. It lacks consensus on an optimal approach for treatment. This is due, at least in part, to the lack of ability to systematically compare treatment efficacy using an ideal animal model that mimics full-range osteonecrosis of femoral head (ONFH) in humans with high incidence of joint collapse accompanied by reparative reaction adjacent to the necrotic bone in a reproducible and accessible way. A number of preclinical animal ON models have been established for testing potential efficacy of various modalities developed for prevention and treatment of ON before introduction into clinics for potential applications. This paper describes a number of different methods for creating animal experimental ON models. Advantages and disadvantages of such models are also discussed as reference for future research in battle against this important medical condition.