Micro-CT Bone Morphometric Analysis Of Femoral Head Necrosis After Internal Fixation Of Femoral Neck Fractures In Young Adults

Objective:Comparing with that of normal femoral neck fracture femoral head samples,analyze the three-dimensional histomorphological characteristics of femoral head necrosis after internal fixation of femoral neck fractures in quantity in young adults using Micro-CT bone morphometric method.Methods:Patients who underwent hip arthroplasty due to femoral head necrosis after femoral neck fracture in the Second Hospital of Shanxi Medical University from October 2018 to October 2020 were used as the experimental group.There were 6 patients,2 males and 4females.The average age was(62.00±9.36)years old,and the hip replacement was performed(47.67±14.22)months after internal fixation.Patients with femoral neck fracture undergoing hip arthroplasty were used as the control group.There were 3 patients,2 males and 1 female,with an average age of(69.33±4.62)years.The femoral head necrosis samples which were collected during the operation were divided into five regions of interest using Micro-CT tomography:the whole body,the hardened area around the nail,the nail channel and hardened area,the relatively normal area and the collapsed area.Applied quantitative analysis to the three-dimensional parameters of trabecular bone in each part,including bone volume fraction(BV/TV),number of trabecular bone(Tb.N),connection density(Conn.D),trabecular bone thickness(Tb.Th),bone size Beam separation(Tb.Sp),structural model index(SMI)and bone density(BMD),etc.By three-dimensional reconstruction technology,analyze the nail channel and hardened area,collapse area and relative normal area percentage in the femoral head necrosis sample.Results:1.Compared with the normal group BV/TV(0.1248±0.0390),oon.D(2.5708±0.5187)/mm~3,Tb.N(0.7314±0.0990)/mm,Tb.Th(0.1713±0.0333)μm,SMI(1.2115±0.3872)and BMD(66.5181±43.0380)g/cm~3.In the experimental group,the overall femoral head BV/TV(0.2448±0.0586),Coon.D(5.4131±1.773)/mm~3,Tb.Th(0.2952±0.0322)μm and BMD(203.4379±59.2638)g/cm~3;BV/TV(0.3180±0.0617),Coon.D(6.9261±2.4715)/mm~3,Tb.N(1.3533±0.2760)/mm,Tb.Th(0.3262±0.0136)μm and BMD(298.9241±54.2029)g/cm~3;relative to normal area BV/TV(0.2162±0.0642),Tb.Th(0.2817±0.0410)μm and BMD(182.5022±86.0429)g/cm~3.BV/TV(0.2222±0.0684),Coon.D(5.4741±2.3024)/mm~3,Tb.Th(0.2775±0.0326)μm and BMD(195.0153±71.8509)g/cm~3 in the collapse area were significantly increased.In the experimental group,SMI(0.4766±0.2200)in the hardened area and SMI(0.5749±0.5085)in the collapsed area were significantly reduced.2.In the experimental group,BV/TV,Coon.D,Tb.N and BMD in the sclerotic zone were compared with the overall Tb.N and BMD of the femoral head;BV/TV,Coon.D,Tb.N and BMD in the normal zone and BV in the collapse zone were compared/TV and BMD increased significantly.3.In the experimental group,the volume ratio of the nail channel and the hardened area around the nail to the entire femoral head(0.4964±0.0950),the volume ratio of the relative normal area to the entire femoral head(0.4599±0.1416),and the volume ratio of the collapsed area to the entire femoral head(0.1026±0.0379).Conclusion:After internal fixation of femoral neck fractures,a large amount of hardened bone is formed around the long-term residual internals.The trabecular bone structure is obviously dense.The parameters of trabecular bone are significantly higher than normal femoral head tissue.The nail channel and surrounding hardened bone occupy the entire femoral head.About 50%of the volume,it may be one of the mechanical mechanisms of rapid collapse of femoral head necrosis after femoral neck fracture internal fixation.