Alexandra M. Claus

Comparison of CT, MRI, and radiographs in assessing pelvic osteolysis: a cadaveric study.

In this study, we compared the accuracy of radiography, computed tomography, and magnetic resonance imaging in assessing periacetabular osteolytic lesions. Using a previously published cadaver model, we created 87 lesions in pelves implanted with total hip replacement components. The sensitivity for detecting lesions was 51.7% for radiography, 74.7% for computed tomography, and 95.4% for magnetic resonance imaging. For all three techniques, sensitivity increased as lesion size increased. Magnetic resonance imaging emerged as the most effective tool for detecting small periacetabular osteolytic lesions (≤ 3 cm3). For lesions larger than 3 cm3, which are of more concern clinically, computed tomography and magnetic resonance imaging were effective in identifying lesions with detection rates greater than 80%. For radiography and computed tomography, lesion detection was dependent on lesion location, whereas magnetic resonance imaging had consistently good sensitivity in all lesion locations. Although the mean volumetric errors for computed tomography and magnetic resonance imaging (0.3 cm3 and 0.8 cm3) were small compared with mean lesion volume (6.1 cm3), computed tomography was more accurate than magnetic resonance imaging at measuring lesion volume, with a lower mean absolute error. This study verifies the problems associated with radiographic detection of osteolysis while showing the effectiveness of computed tomography and magnetic resonance imaging in determining the presence of lesions and assessing their three-dimensional volume.

Long-term results using the anatomic medullary locking hip prosthesis.

Since the introduction of cementless total hip arthroplasty in the early 1980s, concern has shifted from component loosening toward polyethylene wear and osteolysis. The current review of 223 consecutive unselected Anatomic Medullary Locking femoral and acetabular components extends the followup on a series of patients previously reported on at 5 and 10 years. The purposes are to describe the reasons for revisions and to assess the onset and size of osteolytic lesions, with the hypothesis that osteolysis represents an important cause of loosening. The population included 204 patients (211 hips) with mean followup of 13.9 years (range, 2-18 years). Among them, 122 patients (129 hips) had a minimum 15-year followup. Minimum 2-year radiographs with a mean radiographic followup of 12.2 years (range, 2-18 years) were available for 204 hips (197 patients). Of the entire study group, 39 hips (38 patients) had 44 component revisions, increasing the number of revisions by 24 since this series was reported previously. Twenty-six patients (27 hips) had their first revision surgery more than 10 years after the primary surgery. The most common reason for revision of original components was wear or osteolysis occurring in 22 of the 39 hips (21 of 38 patients). The overall loosening rate was 3.4% (seven of 204) for femoral components and 5.4% (11 of 204) for acetabular components. Twenty-four percent of hips (48 of 204) had evidence of femoral or pelvic osteolytic lesions larger than 1.5 cm2. Femoral osteolysis was not associated with any case of femoral loosening, whereas seven of the 11 loose acetabular components were associated with pelvic lesions larger than 1.5 cm2.

Radiographic definition of pelvic osteolysis following total hip arthroplasty

BACKGROUND Radiographs are the standard clinical tool used to monitor patients with pelvic osteolysis after total hip arthroplasty; however, previous reports have questioned the value and accuracy of this method. With use of a cadaveric model, we investigated the accuracy of radiographs in determining the location and size of periacetabular osteolysis. METHODS We implanted total hip arthroplasty components in eight cadaveric hips and made four radiographs of each hip from different views. We then removed the components and created two pelvic defects in each hip. We measured the volume of each defect, reimplanted the components, and made another set of radiographs. The defects were then enlarged two more times, with the volume measured and another set of radiographs made each time. In total, 128 radiographs were made of forty-eight lesions. An orthopaedist who was blinded to the location of the lesions assessed the radiographs with regard to the presence and size of osteolytic lesions. RESULTS The overall sensitivity for the detection of osteolysis on a single radiograph was 41.5%, and the overall specificity was 93.0%. Sensitivity was dependent on the location and size of the lesions but not on the radiographic view. Sensitivity ranged from 72% for lesions in the ilium to </=15% for lesions in the ischium and acetabular rim. The detection rate for lesions with a volume of >10 cm (3) was significantly higher than that for smaller lesions (p < 0.001). When all four radiographic views of one lesion were analyzed together, sensitivity increased to 73.6%. Despite the low sensitivity, specificity remained high, indicating that once osteolysis is evident radiographically, the likelihood that a lesion truly exists is high. Additionally, we found that the extent of osteolysis was substantially underestimated on radiographs. CONCLUSIONS The use of radiographs to assess and monitor osteolysis has both limitations and merits. Using multiple views, an experienced orthopaedist identified only 73.6% of pelvic lesions. However, once a pelvic osteolytic lesion is evident radiographically, the likelihood that it truly exists is high.

What we have learned about long-term cementless fixation from autopsy retrievals.

The current authors summarize insights gained from their experience studying uncemented porous-coated femoral and acetabular hip replacement components retrieved at autopsy. For femoral components, autopsy studies showed that osseointegration occurs over an average 35% of the porous surface with the most predictable ingrowth occurring near the termination of the porous coating. The bone ingrowth pattern causes a predictable bone remodeling pattern: an overall decrease in bone mineral content (mean, 23% loss) occurring on a gradient with the most loss proximally and the least distally. This pattern occurs regardless of the implant’s level of coating, mirrors the gradient of strain reduction, and because it is recognized easily, can be used by orthopaedists to distinguish between components with and without bone ingrowth on standard radiographs. Studies also have shown that femoral bone loss is more related to the characteristics of the implanted femur than any other variable. On the acetabular side, bone ingrowth is more unpredictable and occurs randomly. Although the amount of acetabular bone ingrowth averaged 32%, it ranged from 3% to 84%. Unfortunately, a consistent pelvic remodeling pattern has not been associated with an implanted porous-coated uncemented cup. Consequently, orthopaedists cannot determine radiographically whether an acetabular component truly is bone ingrown. Overall, autopsy studies have contributed to a basic understanding of the histologic and radiographic appearance of osteointegrated porous-coated implants and have confirmed the durability of this three-dimensional fixation even in the presence of osteolysis.

Long-term results using the anatomic medullary locking hip prosthesis

Since the introduction of cementless total hip arthroplasty in the early 1980s, concern has shifted from component loosening toward polyethylene wear and osteolysis. The current review of 223 consecutive unselected Anatomic Medullary Locking femoral and acetabular components extends the followup on a series of patients previously reported on at 5 and 10 years. The purposes are to describe the reasons for revisions and to assess the onset and size of osteolytic lesions, with the hypothesis that osteolysis represents an important cause of loosening. The population included 204 patients (211 hips) with mean followup of 13.9 years (range, 2–18 years). Among them, 122 patients (129 hips) had a minimum 15-year followup. Minimum 2-year radiographs with a mean radiographic followup of 12.2 years (range, 2–18 years) were available for 204 hips (197 patients). Of the entire study group, 39 hips (38 patients) had 44 component revisions, increasing the number of revisions by 24 since this series was reported previously. Twenty-six patients (27 hips) had their first revision surgery more than 10 years after the primary surgery. The most common reason for revision of original components was wear or osteolysis occurring in 22 of the 39 hips (21 of 38 patients). The overall loosening rate was 3.4% (seven of 204) for femoral components and 5.4% (11 of 204) for acetabular components. Twenty-four percent of hips (48 of 204) had evidence of femoral or pelvic osteolytic lesions larger than 1.5 cm 2 . Femoral osteolysis was not associated with any case of femoral loosening, whereas seven of the 11 loose acetabular components were associated with pelvic lesions larger than 1.5 cm 2 .

The relationship between lysis and loosening in failed anatomic medullary locking components.

Lysis does not cause loosening of extensively porous-coated, apparently well-fixed femoral components. We attribute this in large part to the fact that the area of strongest bone ingrowth is in the femoral diaphysis remote from the joint space. In contrast, for the acetabular component, osteolysis can be the sole or a contributing factor to loosening. We attribute this difference to the fact that the bone-implant interface of the acetabular component is much closer to the joint space and more readily accessible to osteolytic damage. In the future, with improved bearing surfaces, lysis may occur less frequently. Whether lysis is diminished as a result of these new designs, the authors contend that without adequate initial fixation, loosening will still occur. Because of our observations concerning osteolysis and loosening, we are more cautious in revising patients for osteolyis and do not revise when osteolysis first becomes apparent. Rather, we closely monitor osteolysis in these patients. For us, the question of when to operate for osteolysis remains unanswered.

Accuracy of ein bild Röntgen analyse in determining wear in total hip arthroplasty in vitro

The Ein Bild Röntgen Analyse system is used to radiographically measure femoral head penetration in total hip replacement components. Because determining the accuracy of any wear analysis system is more precise and comparable under in vitro conditions, we used a femoral head migration simulator to assess the accuracy of Ein Bild Röntgen Analyse and determine the effect of magnification factors on accuracy. We used onscreen magnifications of 100% and 200% to measure anteroposterior radiographs, which improved the accuracy of determining femoral head penetration. Improvements averaged 0.056 mm (95% CI ± 0.013 mm) in the X direction and 0.024 mm (95% CI ± 0.027 mm) in the Y direction. Femoral head penetration was simulated in 0.25-mm steps from 0-1 mm. Accuracy ranged from 0-0.029 mm (95% CI, 0.035-0.067 mm) for the X direction and from 0.001-0.013 mm (95% CI, 0.046-0.079 mm) for the Y direction. Assuming the worst accuracy combined for the X and Y directions, Ein Bild Röntgen Analyse can accurately detect femoral head penetration greater than 0.128 mm. These results are comparable with reported accuracy values for different systems and suggest that magnification tools should be considered with Ein Bild Röntgen Analyse when measuring wear radiographically.