Lack of improvement is thought to be unhelpful and warrants follow-up [129,130]. MRI Hip Wear: MRI is thought to be the most helpful tool for assessing the severity of intracapsular wear-induced synovitis [131]. On MRI, polyethylene wear-induced synovitis appears as low to intermediate signal intensity material that may distend the joint and extend into adjacent bursae [18]. Loosening: Burge et al [132] compared MRI with MAR techniques to radiographs with findings assessed at revision surgery. MRI was shown to be more sensitive than radiography for assessment of component loosening. For acetabular component loosening, MRI showed a sensitivity of 83% and a specificity of 98% compared with radiographs (sensitivity of 26% and specificity of 100%). For femoral component loosening, the sensitivity of MRI was 75% and the specificity 100%, whereas radiographs showed a sensitivity of 20% and a specificity of 100%. Backer et al [120] evaluated MRI and SPECT/CT for assessing loosening and found the sensitivity, specificity, PPV, and NPV of MRI were 86%, 88%, 60%, and 100% and of SPECT/CT were 93%, 97%, 90%, and 100%, respectively. Osteolysis: There is some discrepancy in the literature regarding whether CT or MRI is the optimal study for detecting osteolysis. This may be related to technical factors. Potter et al [133] compared MRI appearances and surgical findings in 15 hips. In all operated cases, osteolysis found on MRI was confirmed at surgery. Walde et al [126] evaluated CT and MRI for the detection of osteolytic lesions in a cadaver model. For lesions of all sizes, CT was 74.7% sensitive and MRI was 95.4% sensitive. The sensitivity of radiographs was only 51.7%. However, Robinson et al [134] demonstrated a reduced sensitivity (27%) and specificity (1%) of MARS-MRI in comparison with CT-MAR for detecting osteolysis associated with painful MoM hip prostheses.
Imaging after Total Hip Arthroplasty PCAs. Lack of improvement is thought to be unhelpful and warrants follow-up [129,130]. MRI Hip Wear: MRI is thought to be the most helpful tool for assessing the severity of intracapsular wear-induced synovitis [131]. On MRI, polyethylene wear-induced synovitis appears as low to intermediate signal intensity material that may distend the joint and extend into adjacent bursae [18]. Loosening: Burge et al [132] compared MRI with MAR techniques to radiographs with findings assessed at revision surgery. MRI was shown to be more sensitive than radiography for assessment of component loosening. For acetabular component loosening, MRI showed a sensitivity of 83% and a specificity of 98% compared with radiographs (sensitivity of 26% and specificity of 100%). For femoral component loosening, the sensitivity of MRI was 75% and the specificity 100%, whereas radiographs showed a sensitivity of 20% and a specificity of 100%. Backer et al [120] evaluated MRI and SPECT/CT for assessing loosening and found the sensitivity, specificity, PPV, and NPV of MRI were 86%, 88%, 60%, and 100% and of SPECT/CT were 93%, 97%, 90%, and 100%, respectively. Osteolysis: There is some discrepancy in the literature regarding whether CT or MRI is the optimal study for detecting osteolysis. This may be related to technical factors. Potter et al [133] compared MRI appearances and surgical findings in 15 hips. In all operated cases, osteolysis found on MRI was confirmed at surgery. Walde et al [126] evaluated CT and MRI for the detection of osteolytic lesions in a cadaver model. For lesions of all sizes, CT was 74.7% sensitive and MRI was 95.4% sensitive. The sensitivity of radiographs was only 51.7%. However, Robinson et al [134] demonstrated a reduced sensitivity (27%) and specificity (1%) of MARS-MRI in comparison with CT-MAR for detecting osteolysis associated with painful MoM hip prostheses.