Abstract
The timing of liner exchange for retroacetabular oste-olysis in THA remains uncertain. Liner exchange should be done before the shell becomes loose. The purpose of this study was to determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell. Osteolytic lesions were quantified radiographically using three different measures. Implant stability was confirmed intraoperatively. Percent of shell circumference with surrounding osteolysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than fifty percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.
The timing of liner exchange for retroacetabular osteolysis in cementless THA remains uncertain. Liner exchange should be done before the shell becomes loose.
To determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell.
Osteolytic areas differ between loose and stable shells.
Between 1992 to 2002, seventy-one cementless shells of the same design were revised at our institution; forty-six were for aseptic retroacetabular osteolysis. Radiographs and a computer-assisted technique were used to quantify osteolytic areas and percent of shell circumference associated with lesions. Implant stability was confirmed intraoperatively.
Of twenty-six stable and twenty loose shells, the average area of osteolysis on AP radiographs showed no significant difference (Stable 591mm2, Loose 630 mm2, p greater than 0.05); whereas, lateral radiographs demonstrated a significant difference (Stable 546 mm2, Loose 837 mm2, p 0.05). The percentage of shell circumference with associated osteolysis on AP and lateral films demonstrated a significant difference (AP: Stable 60, Loose 75, p 0.042; LATERAL: Stable 49, Loose73, p 0.016). Diagnostic criteria of fifty percent shell circumference associated with osteolysis on AP films has sensitivity 1, specificity 0.27 while the same criteria on lateral films has sensitivity 0.84, specificity 0.54 for shell loosening.
Percent of shell circumference with surrounding oste-olysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than fifty percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
