04/05/2011 04:48 pm ET Updated Jun 05, 2011

Imaging Studies and Knee Replacement Surgery: What You Need to Know

An article and video on titled 'What you need to know about total knee replacement' was extremely interesting and provided detailed information about the procedure. As a radiologist who sees images of thousands of total knee replacement patients every year I'd like to contribute some additional information to the informative piece, and discuss the integral role imaging plays in this procedure.

Imaging is invaluable and, as they showed, is pivotal in determining whether the knee replacement is even necessary. In addition to using radiologic images to determine whether a replacement is needed, they are also used in the operating room to help guide the orthopedic surgeon for proper placement of the total knee replacement components. After surgery, imaging is also used to help assess post-operative healing.

Hospital for Special Surgery performs approximately 4,000 knee replacements every year and is one of the top centers in the world for joint replacement surgery. The HSS radiology technologists and musculoskeletal radiologists provide the orthopedic surgeons with the appropriate images and accurate interpretations for images in the pre-operative, intra-operative and post-operative stages.

In the pre-op phase, imaging examinations are done to diagnose the patient's cause for pain and determine the extent of the issue that is causing the problem. The results of the initial imaging examination guide the orthopedic surgeon and help determine whether a knee replacement is the appropriate course of treatment. Initial imaging typically includes specific conventional X-rays and in many patients also includes an MRI examination. These imaging studies help document the severity of the problem, assist with planning the surgical approach and help in determining the specific implant that will be used.

In the operating room, surgeons rely on specific conventional X-ray images to help guide the placement of the total knee replacement. Following surgery, imaging is performed to assess positioning and/or diagnose potential infection or loosening of the total joint replacement components.

MRI radiologists at HSS have devised a way to image total knee replacements without image distortion from the implant and without damaging the total knee replacement. Even though metal and MRI are incompatible and a total knee prosthesis is metal, the use of specific MRI protocols that were developed by HSS radiologists allow for total knee replacements to be safely imaged. This has revolutionized post-surgical knee replacement imaging and physicians all over the world are now using these methods to help assess the cause for those rare instances of unexpected postsurgical discomfort.

Carefully acquired images and accurate image interpretations are pivotal in the diagnosis, assessment and total knee replacement surgical planning, in addition to the post-surgical follow-up. Imaging expectations should be included in the overall understanding of what is involved in total knee replacement surgery.