Three-Dimensional Distribution of Bone-Resorption Lesions in Osteonecrosis of the Femoral Head Based on the Three-Pillar Classification

Abstract

Objective: To investigate three-dimensional distribution of bone-resorptive lesions based on the three-pillar classification and its effect on the disease progression of osteonecrosis of the femoral head (ONFH).

Methods: A total of 194 femoral head CT images from 117 patients diagnosed with ARCO stage II and III ONFH were retrospectively reviewed from April 2014 to February 2019. Three-dimensional structures of the femoral head and the bone-resorptive lesions were reconstructed. Using the three-pillar classification and coronal plane of the femoral head, we divided each femoral head into six regions to observe the location characteristics of bone-resorption lesions, and explore the destruction of different areas of the femoral head by the bone-resorptive lesions. Then the hips were divided into two groups based on whether they contained bone-resorption lesions and compared the difference of stage II and stage III between the two groups.

Results: The regional distribution revealed 39 (27.27%), 55 (38.46%), six (4.20%), 23 (16.08%), 17 (11.89%) and three (2.10%) bone-resorptive lesions in regions I, II, III, IV, V and VI respectively. The lateral pillar, AL (I + IV), contained 44.76% of the lesions, central pillar, C (II + V), 48.95%, and medial pillar, M (III + VI), 6.29%. Moreover, there were 81.82% bone-resorption lesions in anterolateral pillar, AL (I + II + IV), and 18.18% in posteromedial pillar, PM (III + V + VI). In all ONFH hips, the lateral pillar of 81(88.04%) femoral heads were affected, the central pillar of 84 (91.30%) femoral heads were affected, and the medical pillar of 29 (31.52%) femoral heads were affected. The ratio of ARCO stage III in the group with bone-resorption lesions was significantly higher than that of the group without bone-resorption lesions (76.09% vs 30.39%, P < 0.001).

Conclusions: This study demonstrated that the bone-resorption lesions are mainly distributed in the lateral and central pillar of the femoral head, and the two pillars of the femoral head are usually involved by bone-resorption lesions. Furthermore, the ratio of ARCO stage III in the group with bone-resorption lesions was significantly higher than that of the group without bone-resorption lesions, suggesting that the bone-resorption lesions might accelerate the progression of ONFH.

Keywords: Bone-resorptive lesions; Collapse; Osteonecrosis of the femoral head; Three-dimensional distribution; Three-pillar classification.

Fig. 1

Three‐dimensional reconstruction of the femur, and bone‐resorptive lesions. (A, B) The region of femoral head and bone‐resorption lesions is obtained by software's' semiautomatic tools and manual addition and subtraction. The yellow area is the femoral head area at a certain level (A), The purple area is a bone‐resorptive lesion at a certain level (B); (C, D) Objects are reconstructed in three dimensions and smoothed. (C) femoral head, (D) bone‐resorptive lesions.

Fig. 2

The determination of the reference plane. (A) The green point, red point, and blue point indicate the positions of the center of femoral head fovea, the center of the femoral head and the center of the femoral neck. (B) The reference plane (red plane) was obtained, which included the center of femoral head fovea, the center of the femoral head and the center of the femoral neck.

Fig. 3

Determination of three segmentation planes. (A) Connect the center of femoral head (red point) and the center of femoral neck (blue point) as the axis line of the femoral head and the femoral neck (blue line). (B) On reference plane, make the vertical line of the axis line through the center of the femoral head as the diameter line of the femoral head (red line). (C) Determine two segmentation reference points (deep blue points), which could divide the diameter line into three parts of 30%: 40%: 30%. (D) Cross the two segmentation points to make two planes which is perpendicular to the femoral diameter line (red plane), and use these two planes to divide the femoral head into lateral (L), central(C), and medial (M) pillars. (E) Using reference plane (orange plane), the femoral head is divided into anterior and posterior parts.

Fig. 4

The femoral head are divided into six regions (I–VI) by three planes. (A) I–III represents lateral, central and medial pillars in the anterior side of femoral head respectively. (B) IV–VI represents lateral, central and medial pillars in the posterior side of the femoral head respectively.

Fig. 5

To make the distribution characteristics more obvious, the six areas are redivided into two areas: anterolateral pillar, zone AL (I + II + IV) and posteromedial pillar, zone PM (III + V + VI). (A) The locations of zone AL (I + II + IV)(B)The locations of zone PM (III + V + VI).