Using nonlinear finite element models to analyse stress distribution during subluxation and torque required for dislocation of newly developed total hip structure after prosthetic impingement

Abstract

Dislocation is a serious potential complication of total hip replacement. Previous studies have proposed a newly developed total hip structure that meets the required oscillation angle of 120°, for which the chamfer on the acetabular liner rim was designed to enable the neck to impinge on the chamfer over a large area after impingement occurs. This study adopted the finite element method to further analyse the torque limits leading to dislocation and the contact stresses at the impingement and egress sites of the liner during subluxation. The compressive stress-strain curve for ultra-high molecular weight polyethylene is nonlinear. The results reveal that an adequate chamfer angle of the acetabular cup liner can significantly increase dislocation torque and decrease contact stress on the liner rim. By means of the new design, when the head-neck ratio (HNR) is 2.5 or 3.0, the maximum torque value that a 36-mm head can withstand is 1.38 (8.7 Nm/6.3 Nm) or 1.47 (8.4 Nm/5.7 Nm) times that of a 22-mm head, while the maximum stress of a 36-mm head is 0.41 (14.58 MPa/35.73 MPa) or 0.70 (33.71 MPa/47.90 MPa) times that of a 22-mm head. When the head diameters are identical, the dislocation torque of the HNR = 2.5 structure is slightly greater than that of the HNR = 3.0 structure (3.3-10.5%); thus, the newly developed structure can disperse contact stress, and the structure of a large head with a low HNR exhibits a higher dislocation torque value and lower stress.

Estimation of the effects of inset heights and slit configurations in an acetabular cup on the pull-out behavior of an artificial hip joint with a structure for preventing dislocation using finite element analysis

“…The minimum forces are likely to be valuable target values for designing a new type of artificial hip joint. Moreover, impingement of the femoral neck on the acetabular cup is induced by an inadequate range of hip joint movement [13,17,53]. We will conduct further analyses to study the effects of pull-out direction or loading torque on the pull-out behavior of the joints.…”

“…They concluded that the femoral heads and acetabular cups with a relatively large diameter increased the range of motion after THA and decreased the risk of dislocation. Using finite element analysis, Chi et al [17] also verified that an increased size of the heads and cups resulted in a significant increase in the torque value, which induced dislocation after prosthetic impingement occurred. Human artificial hip joints with structures for preventing dislocation have been previously developed and utilized clinically.…”

Topology Optimization of a Femoral Stem in Titanium and Carbon to Reduce Stress Shielding with the FEM Method

“…As a result of its excellent conductive and favorable bioactive properties, it is widely preferred as a biomaterial of choice in both dentistry and orthopedics [29,30]. While one of the advantages of carbon fiber is that it is biocompatible [31][32][33][34], promotes bone growth on the surface, and has mechanical characteristics similar to cortical bone, there is a reduction in stress shielding. Under the same constraint and load conditions shown in Figure 4a, the results on the von Mises stress distribution for the rod topologically optimized in composite material are reported in Figure 11.…”

Using artificial neural networks to predict impingement and dislocation in total hip arthroplasty

“…A patient who undergoes hip dislocations has reduced mobility, which directly affects the quality of life and increases the costs to the health system (Brown and Callaghan, 2008). Management of THA instability remains a surgical challenge and represents a multifactorial problem that includes the patient condition, surgical technique, implant component design and orientation, bone quality, and surrounding soft tissues (Brown and Callaghan, 2008;Barrack, 2003 Gao et al, 2018;Chi et al, 2018). All previous studies showed an added value with respect to a rigid body dynamics analysis.…”