Quantitative susceptibility mapping detects neovascularization of the epiphyseal cartilage after ischemic injury in a piglet model of legg‐calvé‐perthes disease

Abstract

Background Legg‐Calvé‐Perthes disease (LCPD) is a childhood hip disorder thought to be caused by disruption of blood supply to the developing femoral head. There is potential for imaging to help assess revascularization of the femoral head. Purpose To investigate whether quantitative susceptibility mapping (QSM) can detect neovascularization in the epiphyseal cartilage following ischemic injury to the developing femoral head. Study Type Prospective. Animal Model Right femoral head ischemia was surgically induced in 6‐week‐old male piglets. The animals were sacrificed 48 hours (n = 3) or 4 weeks (n = 7) following surgery, and the operated and contralateral control femoral heads were harvested for ex vivo MRI. Field Strength/Sequence Preclinical 9.4T MRI to acquire susceptibility‐weighted 3D gradient echo (GRE) images with 0.1 mm isotropic spatial resolution. Assessment The 3D GRE images were used to manually segment the cartilage overlying the femoral head and were subsequently postprocessed using QSM. Vessel volume, cartilage volume, and vessel density were measured and compared between operated and control femoral heads at each timepoint. Maximum intensity projections of the QSM images were subjectively assessed to identity differences in cartilage canal appearance, location, and density. Statistical Tests Paired t‐tests with Bonferroni correction were used (P < 0.008 considered significant). Results Increased vascularity of the epiphyseal cartilage following ischemic injury was clearly identified using QSM. No changes were detected 48 hours after surgery. Vessel volume, cartilage volume, and vessel density were all increased in the operated vs. control femoral heads 4 weeks after surgery (P = 0.001, 0.002, and 0.001, respectively). Qualitatively, the increase in vessel density at 4 weeks was due to the formation of new vessels that were organized in a brush‐like orientation in the epiphyseal cartilage, consistent with the histological appearance of neovascularization. Data Conclusion QSM can detect neovascularization in the epiphyseal cartilage following ischemic injury to the femoral head. Level of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:106–113.

Anti-Interleukin-6 Therapy Decreases Hip Synovitis and Bone Resorption and Increases Bone Formation Following Ischemic Osteonecrosis of the Femoral Head

“…To assess the temporal changes of IL‐6 production in the piglet model after the induction of ischemia, we obtained newly cut histologic sections from the animals euthanized at 48 hours, 4 weeks, and 8 weeks post‐ischemia surgery ( n = 4 animals per time point) from our previous studies. ( 37,38 ) These animals had the same age, surgery, and postoperative care as the animals in the no treatment group of our current study. IL‐6 immunohistochemistry was performed, as described in the immunohistochemical staining section below.…”

T1ρ and T2 mapping detect acute ischemic injury in a piglet model of Legg–Calvé–Perthes disease

“…Patients with LCPD often present clinically before revascularization in the so‐called stage of avascular necrosis, and the degree and location of ischemic injury to the SOC are important considerations for surgical intervention 1,6 . Injury to the epiphyseal cartilage may also be important to consider, given both its roles in endochondral ossification and in promoting revascularization via hypoxic signaling and vessel ingrowth 11,17,47‐49 . Thus, T1ρ and T2 mapping provide alternative or complementary measures to contrast‐enhanced MRI to detect early‐stage ischemic injury to the SOC and the epiphyseal cartilage.…”

Diagnostic Value of Magnetic Resonance Image Feature Analysis under Reconstruction Algorithm for Knee Epiphyseal Injury

“…Clinical imaging examination is the main way to evaluate the degree of epiphyseal injury in adolescents and children, including X-ray plain film examination, ultrasound examination, CT examination, and MRI examination [6]. X-ray plain film is the first choice for examination of bone trauma, but due to incomplete epiphyseal ossification, X-ray plain film cannot develop normally, so that missed diagnosis and misdiagnosis often occur.…”