Acetabular Bone Defect in Total Hip Arthroplasty for Crowe II or III Developmental Dysplasia of the Hip: A Finite Element Study

Abstract

Background. The purpose of this study was to establish the finite element analysis (FEA) model of acetabular bone defect in Crowe type II or III developmental dysplasia of the hip (DDH), which could evaluate the stability of the acetabular cup with different types of bone defects, different diameters of femoral ceramic heads, and the use of screws and analyze the stress distribution of screws. Methods. The FEA model was based on the CT scan of a female patient without any acetabular bone defect. The model of acetabular bone defect in total hip arthroplasty for Crowe II or III DDH was made by the increasing superolateral bone defect area of the acetabular cup. Point A was located in the most medial part of the acetabular bone defect. A 52 mm PINNACLE cup with POROCOAT Porous coating was implanted, and two screws (the lengths were 25 mm and 40 mm) were implanted to fix the acetabular cup. The stability of the acetabular cup and the von Mises stress of point A and screws were analyzed by a single-legged stance loading applied in 1948 N (normal working). The different diameters of the femoral ceramic head (28 mm, 32 mm, and 36 mm) were also analyzed. Results. The von Mises stress of point A was gradually increased with the increasing uncoverage values. When the uncoverage values exceeded 24.5%, the von Mises stress of point A without screws increased significantly, leading to instability of the cup. Screws could effectively reduce the von Mises stress of point A with uncoverage values of more than 24.5%. However, the peak von Mises stress in the screws with the uncoverage values that exceeded 24.5% was considerably increased. The diameter of the femoral ceramic head had no significant effect on the von Mises stress and the stability of the acetabular cup. Conclusions. We recommend that uncoverage values of less than 24.5% with or without screw is safe for patients with Crowe II or III DDH.

Mid-term outcomes after total hip arthroplasty in 106 Crowe II/III hips: different hip center positions

“…Then, we can observe that THA not only improved the functional scores in Crowe II/III hips, but also helped relieve the pain from the hip and low back [9]. Besides, the hip center position was not associated with the clinical outcomes in Crowe II/III hips, we should consider more of the host bone coverage on the acetabular prosthesis and actual situation during THA [4]. Our study was consistent with previous research [12]…”

“…3 Department of Orthopedics, Weifang People's Hospital, Shandong, China. 4 Department of Nursing, The Third People's Hospital of Datong, Shanxi, China. 5 • thorough peer review by experienced researchers in your field…”

“…An obvious bone defect was frequently found at the superolateral of the true acetabulum in Crowe II/III hips during THA [4]. The special anatomy was like the slab in Rock Climbing, and the slope makes the true acetabulum hard to hold the acetabular cup with host bone coverage in THA.…”

“…More recent clinical studies have recommended that the acetabular cup uncoverage should not exceed 30% of its overall surface, otherwise a structural bone grafting may be needed. It was also reported that uncoverage values of less than 24.5% with or without screw was safe for patients with Crowe II/III hips [4]. Even so, different placements of the acetabular prosthesis are still controversial and more mid-term follow-up studies are required.…”

Prótesis de revisión de cadera en paciente con secuelas de displasia del desarrollo de cadera. Reporte de un caso y revisión de la literatura

“…De acuerdo con la clasificación de Crowe para displasia acetabular, esta paciente presenta un tipo I que corresponde a una migración de la cabeza femoral menor de 50%, 14 en este caso el componente acetabular se pudo colocar de manera exitosa, sin necesidad de colocar injerto óseo o aumentos metálicos, 15 para restituir el centro de rotación de la cadera, sólo requirió de medialización de la copa para proporcionar una adecuada cobertura, 16,17 el fracaso de la reconstrucción articular protésica se debió a una inadecuada inclinación acetabular y anteversión, motivo por el cual la cadera protésica presentó subluxación, se decide restituir copa acetabular con una inclinación acetabular y anteversión correctas, adecuado centro de rotación de la cadera y un recubrimiento total de la copa. 18 En lo que respecta al fémur, presenta un defecto proximal que se extiende a la diáfisis, el vástago indicado inicialmente no fue el correcto presentando hundimiento del mismo, ya que estos tipo de fémur presentan su anatomía irregular y son biomecánicamente insuficientes para una fijación metafisaria proximal, se decide retirar vástago realizando una osteotomía lateral femoral extendida, colocando un vástago modular cónico estriado, los cuales son los idóneos para este tipo defectos, ya que presentan una fijación diafisaria distal, donde al menos se requieren de 2 cm para que sean estables, otorgándoles estabilidad axial y rotacional.…”