A novel model of traumatic femoral head necrosis in rats developed by microsurgical technique

Abstract

Background: Clinical angiography and vascular microperfusion confirmed that the femoral head retains blood supply after a collum femur fracture. However, no animal model accurately mimics this clinical situation. This study was performed to establish a rat model with retained viability of the femoral head and partial vasculature deprivation-induced traumatic caput femoris necrosis by surgery.

Methods: Thirty rats were randomly divided into three groups (n = 10 per group): normal group, sham-operated group (Control), and ischemic osteonecrosis group. The femoral head of the normal group of rats underwent a gross anatomy study and microangiography to identify femoral head blood supply. Microsurgical techniques were used to cauterize the anterior-superior retinacular vessels to induce osteonecrosis. Hematoxylin and Eosin (H&E) staining were used for femoral head histologic assessment. Morphologic assessments of the deformity in and trabecular bone parameters of the femoral head epiphysis were performed using micro-CT.

Results: The blood supply of the femoral head in rats primarily came from the anterior-superior, inferior, and posterior retinacular arteries. However, anterior-superior retinacular vasculature deprivation alone was sufficient in inducing femoral head osteonecrosis. H&E showed bone cell loss in nuclear staining, disorganized marrow, and trabecular structure. The bone volume (BV) decreased by 13% and 22% in the ischemic group after 5 and 10 weeks, respectively. The mean trabecular thickness (Tb.Th) decreased from 0.09 to 0.06 mm after 10 weeks. The trabecular spacing (Tb.Sp) increased from 0.03 to 0.05 mm after 5 weeks, and the epiphyseal height-to-diameter (H/D) ratio decreased.

Conclusions: We developed an original and highly selective rat model that embodied femoral head traumatic osteonecrosis induced by surgical anterior-superior retinacular vasculature deprivation.

Keywords: Animal model; Femoral head traumatic osteonecrosis; Femoral neck fracture; Vasculature deprivation.

Fig. 1

The normal rat femoral head blood supply. The rat femoral head is nourished by the anterior-superior, inferior and posterior retinacular arteries. The anterior-superior retinacular branches were the main stems of the femoral head epiphyseal artery. a The front view of the left hip showing the anterior-superior retinacular branches; b The inside view of the left hip showing the inferior retinacular branches; c The femoral head blood vessels perfusion and reconstruction showing the anterior-superior (Blue arrow), inferior (Red arrow) and posterior (Yellow arrow) retinacular arteries

Fig. 2

Vessel deprivation and creation of the rat femoral head osteonecrosis model. a is the anterior-superior retinacular blood vessels under the microscope. b shows the anterior-superior retinacular blood vessels after vessel deprivation

Fig. 3

Hematoxylin and eosin staining of rat femoral heads. The deprivation of the anterior-superior retinacular blood vessels resulted in cell loss in most regions of the femoral head in terms of nuclear staining in the trabeculae and bone marrow; the structure was disorganized in the femoral head epiphysis after 5 and 10 weeks; however, the entire femoral head epiphysis did not appear completely necrotic. Chondral surfaces were not round and smooth in the ischemic group at week 10. In contrast, the chondral surface was round and smooth, and no cell death or bone structure disorganization manifested in the control group

Fig. 4

Morphological parameters of the femoral heads in the rats were analyzed by micro-CT. Micro-CT was used to assess bone volume percent (BV/TV %) (a), trabecular bone spacing (Tb.Sp)(b), trabecular number (Tb.N) (c), and trabecular thickness (Tb.Th) (d) in the femoral head epiphysis after induction of ischemic osteonecrosis. At 5 and 10 weeks, the ratio of height to diameter of epiphysis in the ischemic group was lower than that in the control group (e)