In order to find a method which was better tolerated by patients and more convenient for radiographers, we modified the procedure by placing a coin as a point of reference directly on the plate. The marker was very small in diameter (23 mm) and the radiographers were unable to accurately estimate the level of the femur of obese patients. Patient feedback confirmed that this was not well tolerated. The method was modified in our hospital by placing the marker between the patient's thighs and attaching it to the skin at the level of the femur. Furthermore, the position of the marker (coin or ball) beside the outer thigh would not be included in anteroposterior X-rays of the pelvis of obese patients. 4, 5 However, it is not convenient or sufficiently feasible for radiographers and it has mostly only been used in experiments. ![]() Other studies have shown this method to be reproducible and accurate. ![]() There are many methods available, including Conn's method 3 which uses a coin or ball of known diameter placed beside the patient's outer thigh at the level of the femur. An object of known size is used as a marker to determine magnification. In order to obtain reliable data, the magnification of templates must correspond to the magnification of preoperative X-rays. The purpose is to restore the biomechanics of the hip and minimize leg length discrepancy. Besides confirming clinical diagnosis, these can also be used for operation planning with digital templating to assess the appropriate size of components, the level of osteotomy, and the required postoperative neck length and femoral offset. 1, 2 Preoperative evaluation includes the analysis of X-rays. To achieve optimal hip function, preoperative evaluation is a very important step for successful THA. Total hip arthroplasty (THA) is a reliable procedure for relieving pain and restoring function of the hip joint. The minimal change in distance for patients with different body shape led to easier and more convenient examination, and increased the feasibility of our modified coin method, except in cases where implantation of a very large-sized prosthesis is necessary. Variation in magnification was caused by variation in distance between the rotation center of the hip and the table. The distance between the rotation center of the hip and the table, which is acknowledged to be a factor which influences magnification of the coin, changed little in response to body shape. Furthermore, in order to confirm the expressiveness of the modified method, CT scans of another 50 patients were randomly selected. Bias did not exceed 1.96 mm during measurement of the prosthesis with a diameter of less than 56 mm, and a range of absolute error of measurements of 56–66 mm (standard deviation, SD, 0.04–3.95 mm). Subsequently, the magnification of the coin was used to correct the measuring scale of the X-rays of the other 50 patients (Group B). ![]() The variation was small and limited, and had no correlation with body shape parameters ( i.e. The actual diameter of the prosthesis head was taken as the gold standard for assessment of the magnification of the coin in Group A. ![]() One hundred patients who had undergone hip replacement were enrolled in the study and randomly divided into two groups. We modified this method by placing a coin on the radiograph plate. But in our experience, it is inconvenient for radiographers and is not well tolerated by some patients. Conn's method of placing a marker of known diameter beside the thigh at the level of the femur has been reproduced in many studies and confirmed as one of the most accurate methods. Scaling of anteroposterior digital pelvic X-rays with variable magnification is the premise for accurate preoperative planning of total hip replacement with digital templating.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |