The survival of non-traumatic osteonecrosis of femoral head at ARCO II with ring-shaped sclerotic zone: a mid-term follow-up retrospective study

Abstract

The sclerotic zone in the osteonecrosis of femoral head (ONFH), containing condensed trabecular bone and abundant neovascularization, is the transition area between osteonecrosis and normal tissue. Due to the prominent feature in ONFH, the characteristics of the sclerotic zone might indicate the femoral head survival of the disease. Thirty ONFH patients (41 hips) with ring-shaped sclerotic zone at Association Research Circulation Osseous-II were recruited during 1996 to 2019, and the corresponding radiographic images in their follow-up are reviewed retrospectively. Two subtypes (type A and B) are defined to discriminate different locations of ring-shaped sclerotic zone in the femoral head (center or subchondral bone plate) in accordance with the radiographic images. The natural history of the enrolled subjects was followed up for average 9 years to record and compare their collapse incidences as well as the progress of hip symptoms. Chi-square test shows that the occurrence rates of symptomatic hip of type A are significantly lower than that of type B and differences between these two groups were significant (P < 0.05). Kaplan Meier survival curve analysis shows that the mean survival time of type A is 247.600 M (95% CI: 203.072 ∼ 292.128 M) and type B is 88.795 M (95% CI: 72.607 ∼ 104.984 M). The survival rate of femoral head of type A is significantly higher than that of type B (P < 0.005). This study demonstrates that type A shows a more satisfactory clinical outcomes and lower femoral head collapse rate in a mid-term follow-up.

Fig. 1.

The two subtypes diagram (the hardened zone of type A is at the center of the femoral head; the hardened zone of type B is located in the subchondral bone plate of the femoral head).

Fig. 2.

A 50-year-old man (Patient 6) who has idiopathic necrosis of the femoral head. (A) Frog-leg lateral radiographs and anteroposterior radiographs show bilateral hips with stage II disease at his initial diagnosis, the right and left are type A. (B) MRI image of the suffered hip obtained at initial diagnosis. (C, D and E) The three years, the sixth year and the eighth year, the patient was free from symptoms and had no radiographic progression of the double femoral head. (F) Until eight years later, the patient was free from symptoms and had good function.

Fig. 3.

A 48-year-old man (Patient 25) who has idiopathic necrosis of the femoral head. (A) Frog-leg lateral radiographs and anteroposterior radiographs show bilateral hips with stage II disease and type A at his initial diagnosis. (B) Without special treatment for 15 years, the patient was free from symptoms and had no collapse of the femoral heads bilaterally on frog-leg lateral radiographs and anteroposterior radiographs. (C) After 21 years, the patient was free from symptoms and had no radiographic progression of the bilateral femoral head. (D and E) MRI image of the suffered hip obtained 16 years later. (F) At present, the patient was free from symptoms and had good function.

Fig. 4.

The time of first occurrence of collapse was used as the survival curve of the end point.