All THA bearing surfaces generate wear particles. The association between PE wear and osteolysis is well established.^1,2,3 Highly cross-linked polyethylene (XLPE) has a significantly lower wear rate than conventional PE.^4,5 Despite the advent of XLPE in the mid-1990s, osteolysis remains a relevant problem because of the large number of prostheses that had been implanted before its development. Additionally, early generations of XLPE may not be as durable as newer versions. Therefore, younger or more active patients who received a joint replacement in the era just after 2000 may also be more likely to experience wear-induced osteolysis requiring revision with a higher frequency than older, sedentary patients. Despite significant wear and osteolysis, many patients are satisfied with the function of their prosthesis and may not be symptomatic.⁶ Early intervention in such patients can allow for a more limited procedure and yield good results if components are well fixed, correctly positioned, and the liner locking mechanism carries a solid track record.^7,8 The acetabular shell can be retained because removal of a well-ingrown shell can entail significant bone loss that may even lead to pelvic discontinuity in severe cases.⁹ Surgical treatment options for osteolysis include bearing exchange with or without debridement and bone grafting of bony defects, cementing an XLPE liner into a well-fixed acetabular shell, or component revision for malpositioned or loose components. In some cases, hip instability can be treated with an isolated head and liner exchange using components that enhance the intrinsic stability of the construct.¹⁰

Instability can be another result of bearing surface wear. Two other causes of recurrent instability are component malposition and neuromuscular dysfunction. For a malpositioned acetabular shell, bearing exchange alone may not suffice to compensate for the malposition. Acetabular shell revision is then recommended. Recurrent dislocation due to neuromuscular causes such as abductor deficiency or other neurologic conditions can be treated with bearing conversion to a constrained liner provided the components are well fixed and well positioned. More recently, the use of dual-mobility constructs has gained traction in cases of recurrent instability.¹¹ Depending on the size of the shell and its properties, a dual-mobility liner can be snap-fit or cemented into the retained well-positioned and well-fixed shell.¹² Head and liner exchange also allows for using a larger-diameter femoral head that confers a higher degree of intrinsic hip stability. However, large heads may produce increased volumetric PE wear and/or present an increased risk of galvanic corrosion at the trunnion.^13,14 It is recommended to increase the femoral head diameter during routine bearing exchange because it increases the jump distance, thereby reducing the risk of instability after revision.¹⁵ The use of ceramic femoral heads with titanium sleeve neck adapters for revision bearing exchanges is strongly suggested whenever feasible to help reduce or eliminate the risk of trunnion corrosion subsequent to the modular bearing exchange.

Hard-on-hard bearings can be associated with particular problems such as adverse soft tissue reactions. A conversion of an existing MOM bearing to ceramic-on-XLPE or metal-
on-XLPE can be a good and straightforward solution.¹⁶ Revision of a COC bearing to an XLPE liner for squeaking
is also a viable option with good clinical results.¹⁷ Rare causes of catastrophic COC bearing failures include fractures of the liner or the femoral head.¹⁸ An isolated head and liner exchange to another hard-on-hard bearing surface is advisable after removal of the fractured fragments with rigorous debridement of all macroscopic debris.¹⁹

Lastly, treatment of acute periprosthetic joint infections with debridement, retention of well-fixed components, and exchange of modular parts in the “debridement with implant retention” strategy is also a good indication for isolated head and liner exchange.²⁰