AI Article Synopsis

  • Early aseptic loosening in uncemented total hip arthroplasty (THA) is primarily caused by inadequate integration of the femoral stem, often due to excessive micromotions.
  • The study investigated how factors like higher femoral offset, smaller stem sizes, and obesity contribute to these micromotions, using finite element analysis on CT scans of patients.
  • Results indicated that combinations of lower femoral offset, larger body weight, and smaller stem sizes significantly increased micromotion, posing a risk for improper osseointegration in patients undergoing THA.

Article Abstract

Early aseptic loosening is caused by deficient osteointegration of the femoral stem due to increased micromotions and represents a common mode of failure in uncemented total hip arthroplasty (THA). This study hypothesized that a higher femoral offset, a smaller stem size and obesity increase femoral micromotion, potentially resulting in early aseptic loosening. A finite element analysis was conducted based on computed tomography segmented model of four patients who received a THA with a triple-tapered straight stem (Size 1, 3, 6). The influence of femoral stem offset (short neck, standard, lateral), head length (S to XXL), femoral anteversion and obesity during daily activities of fast walking and stair climbing was analyzed. The micromotions for the femoral stem zones were compared to a threshold representing a value above which only partial osseointegration is expected. The minimum femoral offset configuration compared to the maximum offset configuration (short neck stem, S head vs. lateral stem, XXL head) leads to a relative mean micromotion increase of 24% for the upper stem zone. Increasing the body weight (body mass index 30-35 kg/m) increases the micromotion by 20% for all stem zones. The obese population recorded threshold-exceeding micromotions for stem sizes 1 and 3 for all offset configurations during stair climbing. Higher femoral offset, a smaller stem size, and higher loading due to obesity lead to an increase in micromotion between the prosthesis and proximal femur and represent a risk configuration for impaired osseointegration of a triple-tapered straight stem, especially when these three factors are present simultaneously.

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Source
http://dx.doi.org/10.1002/jor.25808DOI Listing

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