Study On The Biomechanics And Blood Supply Of Developmental Dysplasia Of The Hip And Clinical Transformation

ObjectiveTo clarify the biomechanical characteristics of the hip.joint and the stress distribution characteristics of the articular cartilage in patients with developmental dysplasia of the hip(DDH).in order to find the best biomechanical matching relationship between femoral head and acetabulum;to determine the distribution and characteristics of nutrient arteries and internal blood vessels of femoral head in patients with DDH;porous tantalum metal acetabular patch was designed by 3D printing technology and applied to clinical practice to observe its clinical effect on DDHMethodsA three-dimensional model of human hip joint was reconstructed by reverse engineering software.The biomechanical models of DDH patients and healthy subjects were constructed.The stress value and variation trend produced by acetabula with different central edge angles being relative to femoral head and acetabular joint cartilage at different times in a complete gait cycle and during the process of sitting down and standing up were compared.The blood vessels of the isolated femoral head were perfused with barium sulfate,and the three-dimensional reconstruction of the blood vessels was performed by high-resolution micro-CT,and then the distribution of the nutrient arteries and the internal blood vessels of the femoral head in the patient with DDH was analyzed,which provided a theoretical basis for surgical design and prognostic judgment.Porous tantalum metal acetabular patch was designed by 3D printing technology and applied to clinical practice to observe its clinical effect on 8 patients(12 hips)with Crowe ? stage DDH.Results? Reverse engineering software can effectively construct finite element models of DDH and hip.joints with different CE angles,which conform to the biomechanical properties of normal hip joints.?In the complete gait cycle,the stress-concentrated area of the articular cartilage is located above the anterior acetabulum and femoral head.In the process of sitting down and standing up,the stress-concentrated area of the articular cartilage is located above the posterior acetabulum and above the femoral head.When the model with a CE angle of 0° presents a single-leg support phase,the peak Von Mises pressure of the cartilage is the largest(the acetabular cartilage is 7.209 MPa,and the femoral head cartilage is 7.433 MPa).When the model with a CE angle of 50° presents the support phase of both legs,the peak Von Mises pressure of the articular cartilage is the lowest(the acetabular cartilage is 2.901 MPa,and the femoral head cartilage is 2.782 MPa).The peak Von Mises pressures at the phase point of the two resultant force peaks during the process of sitting down and standing up are relatively close.As the CE angle increases,the peak Von Mises pressure decreases,The peak Von Mises pressure at the time of CE angle of 0°is about twice of that at the time of the CE angle of 50°The main nutrient arteries of the femoral head in DDH patients are the superior retinacular artery,the inferior retinacular artery and the anterior retinacular artery.The round ligament arteries of most patients are degraded and disappeared;the internal artery of the femoral head is connected to the epiphyseal artery network through the epiphyseal basilar artery network to form a blood supply complex of the femoral head,which has abundant blood supply;and a small amount of nutrient arteries are also present in the cystic reion.?Eight patients(12 hips)with DDH are treated with 3D printing porous tantalum acetabular patches.The CE angle of the lateral hip joint increases from 9.83°±5.54°before surgery to 32.67°±2.53° after surgery.The anterior CE angle increases from 3.83°±2.790 before surgery to 21.67°±1.87° after surgery.The difference is statistically significant(P<0.05).The mean follow-up is 8.2 months;the Harris score is from(69.67±4.62)before surgery to(84.25±4.17)at the time of the last follow-up,so the difference is statistically significant(P<0.05).ConclusionsBiomechanics plays a key role in the pathogenesis and the evolution of DDH,so the coverage of the femoral head increased by the acetabulum can effectively improve its biomechanical environment;the femoral heads of the patients with DDH are rich in blood supply,so there is the possibility of repair and reconstruction in the cystic change area;3D printing porous tantalum acetabular patch can effectively correct the acetabular coverage of the femoral head and improve its biomechanical environment.So it is a new reliable,simple and low-risk surgical technique for the treatment of DDH.