Osteolytic change surrounding biodegradable cement restrictors used in total hip replacements mimicking malignancy

Abstract

Peri-prosthetic osteolysis is a well-documented complication of total hip arthroplasty. A lesser-known form of peri-prosthetic osteolysis occurs specifically involving biodegradable cement restrictor devices which may be used in total hip replacements (THRs) to contain the cement material within the femoral medullary canal, which would help maintain adequate pressurization within the canal and secure the prosthetic femoral stem. The device is inserted into the femoral medullary canal just distal to the prosthetic stem. Different types of restrictors are used; certain biodegradables forms of restrictors are known to cause progressive osteolysis at the site of insertion, which can present as a gradually enlarging focal lytic lesion on imaging. While this entity as well as its relevance as a risk factor for peri-prosthetic fracture has been discussed in existing literature, the resemblance of this entity to a neoplastic process, particularly given the gradual enlargement over time is not well-documented. Understanding this process and potential pitfall when interpreting imaging, particularly X-rays, in patients who have previously undergone a THR, is important to avoid misdiagnosis of this otherwise benign entity as a neoplastic process and would potentially negate the need for unnecessary investigations.