Abstract: BACKGROUND: At present, digital subtraction angiography is used in the clinical observation of blood supply of femoral head necrosis, and the patency of the nutrient blood vessels of the femoral head is evaluated by observing the in and out of the contrast agent. Although digital subtraction angiography can visually observe the feeding vessels of the femoral head, it cannot quantify the perfusion. In addition, the collapse of the femoral head is closely related to the prognosis of the disease, but there are few studies on the changes in blood supply in the femoral head during the peri-collapse period.
OBJECTIVE: To compare the differences in microcirculation perfusion in different regions and different stages of femoral head necrosis, summarize the changes in microcirculation perfusion characteristics of femoral head necrosis, and observe the effect of dynamic contrast-enhanced magnetic resonance imaging in evaluating the microcirculation perfusion of the femoral head.
METHODS: From February 16 to September 1, 2022, a total of 37 patients (69 hips) who visited a doctor for femoral head necrosis were retrospectively collected, including 29 males and 8 females; the age was (35.35±12.19) years (range 18-65 years). The patient’s bilateral femoral head and proximal femur were scanned by dynamic contrast-enhanced magnetic resonance imaging, and gadoteric acid meglumine was intravenously injected during the scanning. After scanning, Geniq software was used to post-process the data to obtain femoral head microcirculation perfusion parameters. Regions of interest were drawn at the necrotic zone, repair reaction zone, and greater trochanter, and time-signal intensity curves of the regions of interest were obtained and classified. Paired t-tests were used to evaluate differences between necrotic area, repair reaction area, and greater trochanter perfusion parameters, as well as differences in femoral head perfusion in different stages of necrosis. Differences in necrotic area, repair reaction area and greater trochanter time-intensity curve classification were evaluated using the χ2 test.
RESULTS AND CONCLUSION: (1) Comparing the perfusion parameters in different regions, the peak value of enhanced signal intensity, area under the curve, maximum slope, volume transfer constant, and the median volume fraction of extravascular extracellular space in the necrotic region were lower than those of the greater trochanter, and the differences were statistically significant (P < 0.05). There was no statistically significant difference in the volume rate constant (P > 0.05). (2) The signal peak value, area under the curve, maximum slope, volume transfer constant, rate transfer constant, and the median ratio of extravascular to extracellular space in the repair reaction area were higher than those in the necrotic area and the greater trochanter, and the differences were statistically significant (P < 0.05). (3) The median signal peak value and maximum slope of the necrotic area in ARCO stage II were greater than those in ARCO stage III, and the difference was statistically significant (P < 0.05). There were no significant differences in area under the curve, rate transfer constant, volume transfer constant and the median ratio of extravascular to extracellular space (P > 0.05). (4) The signal peak value, area under the curve, maximum slope, volume transfer constant, rate transfer constant, and ratio of extravascular to extracellular space in the repair reaction zone of the ARCO Stage II were lower than those of the ARCO Stage III, and the difference was statistically significant (P < 0.05). (5) It is concluded that the microcirculation perfusion velocity, blood flow and capillary permeability in the necrotic area of the femoral head were significantly reduced, while the microcirculation perfusion velocity, blood flow and vascular permeability in the repair reaction area were significantly improved compared with those in the normal area. With the occurrence of collapse, the perfusion velocity and blood flow were further reduced, and the perfusion in the repair reaction zone was enhanced.

Key words: femoral head necrosis, dynamic contrast-enhanced magnetic resonance imaging, hemodynamics, perfusion, microcirculation