However, Chang et al [14] found that in more than half of patients with surgically proven metallosis, radiographs did not show metal density in the soft tissues preoperatively. Radiographs are neither sensitive nor specific for infection. Normal radiographs do not exclude infection; half of the patients in a series of 20 infected hip prostheses reviewed by Tigges et al were normal [60]. Lucencies suggesting aseptic loosening or focal osteolysis may be present in infected hips [60]. Progression of lucency may be rapid in cases of infection. Periostitis was seen in 2 cases. Stumpe et al [61] reviewed radiographs of 35 patients with painful total hip replacements: 9 with septic, 21 with aseptic prosthetic loosening, and 5 without loosening. Rapid progression of osteolysis, rapid component migration, and/or irregular periprosthetic osteolysis were used to diagnose infection. For 2 readers, a sensitivity of 89% and 78%, specificity of 50% and 65%, and accuracy of 60% and 69% were found. In a review, Fritz et al [18] noted that radiographs are usually the first imaging modality for patients with postoperative lateral hip pain. Radiographs help assess the presence of periprosthetic fractures, avulsions of the greater trochanter, and heterotopic ossification [18]. Radiographs showing >2 mm surface irregularities of the greater trochanter have been reported with abductor tendon abnormalities and peritendinous edema on MRI [62]. However, a review of 38 cases of greater trochanter pain syndrome and 100 controls showed the findings of trochanteric surface irregularities including spurs protruding 2 mm were associated with a 24.7% PPV, 64.0% sensitivity, 25.7% specificity, 74.3% false-positive rate, 36.0% false-negative rate, and 65.3% negative predicative value (NPV) for clinical greater trochanteric pain syndrome [63].
Imaging after Total Hip Arthroplasty PCAs. However, Chang et al [14] found that in more than half of patients with surgically proven metallosis, radiographs did not show metal density in the soft tissues preoperatively. Radiographs are neither sensitive nor specific for infection. Normal radiographs do not exclude infection; half of the patients in a series of 20 infected hip prostheses reviewed by Tigges et al were normal [60]. Lucencies suggesting aseptic loosening or focal osteolysis may be present in infected hips [60]. Progression of lucency may be rapid in cases of infection. Periostitis was seen in 2 cases. Stumpe et al [61] reviewed radiographs of 35 patients with painful total hip replacements: 9 with septic, 21 with aseptic prosthetic loosening, and 5 without loosening. Rapid progression of osteolysis, rapid component migration, and/or irregular periprosthetic osteolysis were used to diagnose infection. For 2 readers, a sensitivity of 89% and 78%, specificity of 50% and 65%, and accuracy of 60% and 69% were found. In a review, Fritz et al [18] noted that radiographs are usually the first imaging modality for patients with postoperative lateral hip pain. Radiographs help assess the presence of periprosthetic fractures, avulsions of the greater trochanter, and heterotopic ossification [18]. Radiographs showing >2 mm surface irregularities of the greater trochanter have been reported with abductor tendon abnormalities and peritendinous edema on MRI [62]. However, a review of 38 cases of greater trochanter pain syndrome and 100 controls showed the findings of trochanteric surface irregularities including spurs protruding 2 mm were associated with a 24.7% PPV, 64.0% sensitivity, 25.7% specificity, 74.3% false-positive rate, 36.0% false-negative rate, and 65.3% negative predicative value (NPV) for clinical greater trochanteric pain syndrome [63].