| Background and Purpose:Acetabular labral tear is one of the main causes of hip pain in young patients.Acetabular labral tears which are usually caused by injury,anatomical abnormalities,or degenerative diseases,can lead to hip pain,joint kink or snapping,limited range of motion,and even stiffness.At present,labral repair under hip arthroscopy is the main method for the treatment of acetabular labral tears.The choice of hip arthroscopy portal is the key to the success of the operation.However,there is a challenge of comprehensive evaluation of the safety and success rate of repair portals in traditional cadaver research.The development of computer-aided design makes it possible to produce individualized 3D digital models of patients.These models have been widely used in 3D model printing,surgical planning,operating simulation,individual guide and prosthesis design.Based on the 3D model of the hip joint,the risk of articular cartilage injury and cortical bone penetration of the common hip arthroscopy portals can be quantitatively evaluated,and the selection of the portal under hip arthroscopy can be optimized.On the other hand,the main cause of hip pain in middle-aged and elderly patients is hip osteoarthritis.In patients with developed dyspepsia of hip(DDH),the biomechanical changes caused by the shallow acetabulum and the reduced contact area between the femoral head and the acetabulum will lead to the premature occurrence of hip osteoarthritis.Based on the three-dimensional model of the hip joint,the finite element analysis model of the hip joint of normal development and DDH patients can clarify the biomechanical defects of the hip joint of DDH patients and further explain the cause of hip osteoarthritis.Currently,total hip arthroplasty(THA)is an effective treatment for final osteoarthritis of the hip in DDH patients.And restoring the biomechanics of the hip joint is the goal of THA.However,there may be insufficient bony coverage and poor initial stability of the acetabular cup when DDH patients with femoral head dislocation undergoing THA at the anatomical level of the acetabulum.Upward reconstruction of the acetabulum can increase bony coverage and stability.However,the extent of acetabular upward displacement and postoperative benefits have not been widely agreed.Therefore,the evaluation of acetabular height and biomechanical benefits in DDH patients undergoing THA is helpful to optimize the clinical surgical and provide biomechanical basis for clinical acetabular cup placement strategy.Methods:Based on the CT of the hip joint,twenty 3D models of the normal development hip joint and three 3D models of the DDH hip joint were reconstructed.The operation of suture anchor insertion during hip arthroscopy labrum repair was simulated on a series of 3D model of the normal development hip joints.By quantifying the Distance to the Articular Cartilage(DAC)and the Distance to the Cortical Bone(DCB),distal anterolateral accessory(DALA),mid-anterior(MAP),anterolateral(AL)and posterolateral(PL)portals were evaluated.There are three DALA portals,including the proximal DAL A(DALA-P),medial DAL A(DALA-M),and distal DAL A(DALA-D),were tested.The medial mid-anterior(MMA)portal.is a modified MAP.The FEA models of Crowe I DDH and normal hips were established based on the 3D model of the hip joint,and the differences of gravity transfer and stress distribution were compared on one leg standing.Then,the FEA model of Crowe Ⅰ-Ⅱ DDH with femoral head dislocation was established.The anatomical reconstruction(0 mm,7.5 mm)and upward reconstruction(15 mm)of Crowe I hip were analyzed on one leg standing.Changes of abductor muscle strength and postoperative stress distribution in Crowe Ⅱ anatomical reconstruction(0 mm),upward reconstruction(10 mm)and high reconstruction(20 mm).Result:Three-dimensional finite element models of the normal and dysplastic hip joints were successfully built,and the results were consistent with the biomechanical characteristics of the hip joint.In unipedal stance,the cartilage stresses in the normal hip were concentrated in the anteroposterior area of the joint,with a peak Von Mises stress of 2.8165 MPa,while the cartilage stresses in the dysplastic hip were also distributed in the anteroposterior area of the joint,but the stresses were more concentrated,with a peak Von Mises stress of 24.692 MPa.The area of high stress in the cartilage of DDH patients coincided with the area of cartilage degeneration in the hip joint.When reconstructing the hip joint in DDH patients with dislocation,the abduction muscle forces required in singleleg stance were 1122.3 N,1176.7 N,and 1298.8 N for anatomic reconstruction,superior reconstruction,and high reconstruction,respectively.acetabular liner contact stresses were 6.9758(3.7293-10.3445)MPa,7.3668(3.7699-11.4150)MPa and 10.7615(7.078210.7615)MPa(p=0.168).The Von mises stress of the femoral stem was 22.9575(11.9140-38.4873)MPa for the high reconstruction,which was higher than 22.2860(11.2190-37.8663)MPa for the anatomical reconstruction and 22.1805(11.3318-37.5298)MPa for the upward displacement reconstruction(p<0.001).The bony contact area of the acetabular cup for the anatomic reconstruction,the upward displacement reconstruction and the high displacement reconstruction was 82.67%,88.38%and 95.90%,respectively(p<0.001).The acetabular cup contact stress was 0.0886(-0.0177-0.4028)MPa for the upward displacement reconstruction,which was lower than 0.1101(-0.0085-0.3751)MPa for the anatomic reconstruction(p=0.220)and 0.1246(-0.0202-0.5563)MPa for the high reconstruction(p<0.001).The 3D FEA models of normal and DDH hips were successfully constructed,and the load was transmitted continuously from the sacroiliac joint to the distal femoral,which was consistent with the biomechanical of normal hip.On leg standing,the stress in the normal hip j oint was concentrated in the anterior superior part of the joint cartilage,and the peak Von Mises stress of the cartilage was 2.8165 MPa.The stress in the DDH hip joint was also distributed in the anterior superior part of the joint cartilage,while the stress was more concentrated.And the peak Von Mises stress of the cartilage was 24.692 MPa.The high stress area of hip cartilage in DDH was consistent with the degeneration area of articular cartilage.Total hip reconstruction reduced the strength of abductor muscle on one leg standing in Crowe Ⅰ-Ⅱ DDH patients,and there was a stress shielding in the Gruen 7 zone of the proximal femur.The bone coverage of the acetabular cup increased with the elevation of acetabular reconstruction.The bone coverage of Crowe Ⅱ hip joint was the smallest,only 54.79%(p<0.001).There was no significant difference in the contact stress of the acetabular liner after Crowe I hip reconstruction.The Von mises stress of the femoral stem in upward reconstruction was higher than that in anatomical reconstruction(p<0.001).The contact stress of acetabular liner for Crowe Ⅱ hip in anatomical reconstruction,upward reconstruction and high reconstruction were 8.60(5.23,11.95)MPa,9.23(5.60,12.33)MPa and 9.33(5.60,12.78)MPa,respectively.The liner contact stress of high reconstruction was higher than that of anatomical reconstruction(p=0.042).The Von mises stress of anatomic reconstruction,upward reconstruction and high reconstruction increased with elevation of acetabular reconstruction.which were 21.81(10.45,38.08)MPa,22.32(11.27,38.66)MPa and 22.92(11.85,39.33)MPa(p<0.001).Conclusion:The appropriate portals of anchor placement during hip arthroscopy can reduce the risk of complications.MAP,DALA-P,AL and PL are suitable for acetabular labrum repair at positions of 4 to 1 o ’clock in the anterior,2 to 12 o ’clock in the anterosuperior,11 o ’clock in the posterosuperior,and 10 to 8 o ’clock in the posterior,respectively.In addition,MMA has the potential to be a low-risk alternative to MAP when anchors are inserted at 3 points.Biomechanical abnormalities play an important role in hip joint degeneration and disease development in DDH patients.The stress of hip cartilage in DDH patients is higher than that in normal hips,and the stress area is concentrated.Total hip reconstruction can improve the abductor function of DDH patients,and this advantage decreases with the increase of acetabular reconstruction level.Anatomical reconstruction can restore the biomechanics in Crowe Ⅰ hip cause the stress shielding in the 7 zone of the proximal femur caused.On the contrary,anatomical reconstruction cannot meet the cup coverage in Crowe Ⅱ hip.While high reconstruction can provide the most cup coverage.Meanwhile,it leads to an increase in hip joint load and contact stress of the liner,which may increase the liner wear.Upward reconstruction can provide more cup coverage without increasing the load of acetabular liner,which is beneficial to the stability of the cup. |
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