![]() Detecting complications after arthroplasty is the result of thorough clinical investigation, history taking, examination, and judicious use of supportive radiologic and laboratory studies. Given sufficient time, all prostheses eventually fail. The specific type of prosthesis, surgical technique, and surgeon-related and patient-related factors play a role in the relative frequency with which complications occur. Although the types of prostheses continuously evolve, hip prostheses may be divided simply into unipolar, bipolar, and total arthroplasties, with the last divided further by bearing surface (metal on polyethylene, metal on metal, ceramic on ceramic, and ceramic on polyethylene). The high prevalence of hip pathology and the broad success of hip replacement surgery have resulted in hip arthroplasty becoming a routine procedure, with an estimated 170,000 primary hip arthroplasties performed annually in the United States and approximately 35,000 revision surgeries performed as revision surgery. More sophisticated imaging and image-guided interventions may then be used to determine the cause of failure, primarily to exclude sepsis. In a postarthroplasty patient, subtle changes may often be indicators of loosening and hardware failure. The relative ease of radiographic comparison allows for more accurate monitoring of disease progression. Cross-sectional imaging may be used for disease confirmation and determination of severity and extent. Together with the clinical evaluation and laboratory studies, radiographic evaluation serves as the first line of investigation of any hip pain, providing an overall view of the hip joint. Based on this study, relying simply on a cursory exam and a hip x-ray to make the decision to replace a hip is a bad idea.Radiographic evaluation of the hip before and after arthroplasty is the cornerstone of radiologic assessment. IMHO all patients who are considering hip replacement surgery need at least a pre – hip replacement MRI (which provides some additional information that at least correlates with pain) and a diagnostic numbing injection into the hip joint which should miraculously relieve the pain and allow good function for the duration of the anesthetic. As I’ve blogged before, there are many things that cause hip pain such as the SI joint, so regrettably, this may mean that we have a reasonable number of patients undergoing an invasive and risky hip replacement who don’t need the surgery. This study suggests that a hip x-ray is sorely lacking in any ability to determine who needs a hip replacement. The upshot? A few years ago many insurance companies, operating on the recommendation of professional societies, started forcing doctors to make hip replacement x-ray and exam based decisions. More freaky was that x-ray evidence of arthritis had no correlation with pain, function, or physical tests! This is a monster issue, as the decision to replace most hips these days is made only by an x-ray which according to this study is insufficient to see if a patient’s hip is a problem and needs to be replaced. While bone marrow lesions (swelling in the bone) and bone cysts were associated with more pain and reported loss of function, they didn’t correlate with less function on the researcher’s physical hip tests. In fact, only one of the physical tests correlated with cartilage loss in the socket, while the other two they used did not. In fact, lost cartilage on the ball (femoral head, the most common place this is seen) didn’t correlate at all with pain and function-only lost cartilage on the socket (acetabulum) was associated with pain and function. ![]() So the amount of lost cartilage in the joint was the single biggest thing that predicted more pain and less function, right? Wrong. Researchers looked at more than 100 x-rays and MRIs of patients with and without hip arthritis and also gave the patients physical tests of the hip (which makes this study better than many others which just look at a correlation between pain and MRI findings). ![]() The most recent entry in this debate was just published last month and it shows how few things on a hip x-ray and MRI correlate well with hip problems. Almost all patients and many physicians still treat x-ray and MRI images like the Oracle of Delphi, yet study after study continues to show that there isn’t great correlation between what we see on these images and pain. ![]()
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