Workup

Alexander P. Sah

A thorough history, physical examination, and xrays are essential to the consultation for consideration of revision surgery.  Often, the patient's history will describe the failure mechanism and match the textbook descriptions of the expected signs and symptoms.  Many other times, the physical examination will hold enough clues to determine the joint problem.  Xrays confirm the suspected diagnosis, and while current xrays are necessary, past xrays are extremely useful in comparison to detect subtle changes over time.

X-rays provide information regarding the position, size, and alignment of the joint components.  Xrays are easy to obtain.  Bone can be evaluated for fractures, osteolysis (bone loss), implant loosening, and other characteristics. Comparing current xrays to prior ones is often the most helpful technique. Most diagnoses can be made by xray alone.

Less frequently, additional imaging tests are ordered.  If exam and xrays are inconclusive, in some instances a nuclear medicine bone scan may help determine if the prosthesis has loosened from the bone. In rare cases, a magnetic resonance imaging (MRI) scan or a computerized tomography (CT) scan will be used to help determine why the joint is problematic.

Laboratory tests including blood work are often ordered in the revision joint replacement workup.  For example, infection is an unfortunate, but not infrequent cause for revision joint replacement.  A blood test is a simple and straightforward method of determining the likelihood of infection being present in the joint.  There may be no other signs of infection present, which can be misleading, but the lab work can determine if infection is present.  Infrequently, if pain is unexplained by other tests, metal levels in the blood can be ordered to see if there is an unusual reaction to the metal implants.  If suspicion persists, a needle can be placed into the hip or knee joint to obtain joint fluid for further analysis, most commonly to rule out infection. 

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