Abstract
Introduction
The purpose of this study was to identify the factors contributing to the development and progression of periacetabular osteolytic lesions and to identify which of these lesions can progress at an early stage following THA using repeated computed tomography scans. We also evaluated the accuracy of radiographs in assessing periacetabular osteolysis after THA with uncemented acetabular components and compared it with results of CT analysis.
Methods
CT scans were done in ninety-seven patients (118 hips) who had undergone primary THA between 1996 and 2004 at our hospital at a minimum of two-years postoperatively, from April to August 2006. All the CT images were acquired using high resolution multi-detector row CT (MDCT). The mean age of the patients at the time of surgery was 46.2 years (range, 21–65 years). The mean follow-up at the time of obtaining CT scan was 82.1 months (range, 18–234 months). The second CT scans were obtained in sixty three hips of 49 patients (36 males and 13 females) in 2009. The mean of patient's age was 52.7 years (range, 30 to 76 years). At the time of initial CT scan, the mean duration of implantation was 76.9 months (range, 17–156 months). The volume of periacetabular osteolysis was measured using Rapidia 3D software version. Linear wear of the PE was measured in digitalized radiographs obtained within 3 months of the surgery.
Results
The sensitivity and specificity of anteroposterior radiographs for detection of osteolysis was 57.6% and 92.9%, respectively. Addition of oblique radiographs increased the sensitivity to 64.4% without changing the specificity. The sensitivity increased to 92.8% for lesion more than 1000 mm3. One hundred four hips with osteolysis on CT had an average volume of 2283.2 ± 6883.8 mm3 (range, 24.2–61657.6 mm3). The average volume with only CT evidence of lysis was 375.1 ± 373.9 mm3 (range, 24.2–1864.7 mm3). Linear wear of PE showed good correlation with 2D lysis area on radiographs (r = 0.60; p < .001) and with 3D lysis volume on CT (r = 0.62; p < .0001). The PE wear accounts for 35% (r2 = 0.35) of the variability of the osteolytic volume in CT scan. There was a large correlation between the 2D lysis area and 3D lysis volume(r=.74). However, the limits of agreement for the volume estimates based on the radiograph area were −4.5 to 5.54 mL. The size of the osteolytic lesion in second CT showed good correlation with Harris hip score(r = 0.553, p<.001) and the volume of osteolytic lesion in initial CT (r = 0.984, p < .001), moderate inverse correlation with patient's age (r = −0.621, p < .001). The progression rate of osteolysis of hips with small osteolytic volume less than 766.97 mm3 in initial CT was 85.82 mm3/year, and that of hips with osteolysis more than 766.97 mm3 was 456.3 mm3/year (p < .001).
