Nutrient arteries appear as radiolucent lines (Fig. 1) on account of their topography and may erroneously suggest fracture lines. (1) How frequently the nutrient artery canals of the femur are seen after cementless THA and their distribution patterns are; (2) How to distinguish visible nutrient artery canal from fracture lines; and (3) Whether clinical significance of the nutrient artery canals of the femur in patients with primary cementless THA is evident or not.Background
Question/purpose
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. 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.Introduction
Methods
The authors propose a manual measurement method for wear in total hip arthroplasty (PowerPoint method, PP-method) based on the well-known PowerPoint software. In addition, the accuracy and reproducibility of the devised method were quantified and compared with two methods previously described by Livermore and Dorr, and accuracies were determined at different degrees of wear. The 57 hips recruited were allocated to; Class 1 (retrieval series), Class 2 (clinical series), and Class 3 (a repeat film analysis series). The PP method was found to have good reproducibility and to better detect wear differences between classes. The devised method can be easily used for recording wear at follow-up visits, and could be used as a supplementary method when computerized methods cannot be employed.
Wear of the polyethylene liner in Total hip arthroplasty (THA) is associated to aseptic component loosening. With low wear bearing surfaces and metal backing in acetabular components the manual methods of measurements have not fared well. Computerized methods increased the ease and accuracy of wear measurement. The average clinician has no access to these methods. In this study we proposed to develop a method of manual wear measurement (PowerPoint – PP method) using a simple office PC and
quantify its accuracy and reproducibility compare the accuracy with Livermore and Dorr method and determine the accuracy in different degrees of wear. The study population was divided into class 1 (C1), Class 2 (C2) and Class 3 (C3) group. C1 group had 20 patients who had undergone liner change for high wear. This class simulated a high wear situation. C2 group had 24 patients who were implanted with HXLP. This class simulated very low wear situation. 10 patients were included in C3 group. The same 6week postoperative radiograph was paired as a set of x rays for analysis. This mimics a zero wear situation. PP method had more consistency with Livermore method for C1 group. For C2 and C3 groups all the three methods did not provide consistent results. The correlation coefficient values for wear measurement by PP method showed good correlation between observers in C1 and C2 wear (P values <
0.05). For C3 with true zero wear there was poor correlation between the observers (r −0.659, 0.028, 0.638). The paired T test P values for all classes and both observers were >
0.05. There was no statistically significant difference in the reading of the two observers. Pearson correlation coefficient for all methods showed good correlation for C1and C2 groups. All the methods had errors while measuring true zero in C3. The one way ANOVA analysis was done to identify the ability of the three methods differentiate between C2 and C3. The PP method had the ability (P value <
0.05) to differentiate between C1, C2 and C3. The Dorr’s and Livermore’s methods could only differentiate the C1 from C2andC3. Computerized methods have certain limitations. Matthew Collier et al reported a mean linear wear rate of 0.4(0.04–0.86) and 0.27 (0.01–0.56) by computerized methods in radiographs with true zero wear. In C3 group the average wear rate by PP method was 0.22 ± 0.206 mm. In PP method ability to work at 400% magnifications, ability to correct for rotation on X axis, grouping function of PowerPoint program leads to less chances of errors. PP method has a good reproducibility for clinical use (r>
0.930). The ability of the PP method to differentiate between C2 and C3 should make it a preferred manual method of wear assessment. The PP method has limitations. The least measurement is limited by diameter of the femoral head. It cannot be utilized for wear analysis in cup loosening or migration. It can be regarded as a supplement to the existing methods of manual wear measurements.
Orientation of acetabular component, influenced by pelvic tilt, body position and individual variations affects the outcome following total hip arthroplasty (THA). Currently available methods of evaluation are either imprecise or require advanced image processing. We analyzed inter-subject and intra-subject variability of pelvic tilt, measured by sagittal sacral tilt (ST) and its relationship with acetabular component tilt (AT) by using a simple method based on standard radiographs. ST was measured on lateral radiographs of pelvis including lumbosacral spine obtained in supine, sitting, standing and lateral decubitus position for 40 asymptomatic THA patients and compared to CT data obtained in supine position. AT was measured on lateral radiographs (measured acetabular tilt: MAT) in each position and compared to measurement of AT on CT and an indirectly calculated acetabular component tilt(CAT). Mean ST changed from supine to sitting, standing and lateral decubitus positions as follows: 26.5°±15.5 (range, 4.6°–73.4°), 8.4°±6.2° (range, 0.6°– 24.5°) and 13.4°±8.4° (range, 0.1°–24.2°) (p<
0.0001, p=0.002, p=0.0055). The MAT on radiographs was not significantly different from the MAT measured on CT (p= 0.002) and the CAT (p=0.058). There is a good correlation between change in ST and MAT in sagittal plane (r =0.93). Measurement of ST on radiographs is a simple and reliable method to track changes in pelvic tilt in different body positions. There is significant inter-subject and intra-subject variation of ST and MAT with postural changes and it may explain causes of impingement or instability following THA, which could not be previously explained.
