Review Question - QID 8353

The differential diagnosis of pain after a total hip arthroplasty encompasses a number of etiologies, but the question is directed to a basic and essential part of the workup (ie, definitively considering and ruling in or out the possibility of deep sepsis). Radiographs may point to other, obvious sources of pain, but the orthopaedic surgeon must not overlook the possibility that deep sepsis is the predominant cause of the symptoms. Accordingly, ESR and CRP are logical next steps in the workup in this clinical scenario. Radiographs show increased anteversion of the metal socket, and pain etiologies can include psoas irritation, hip instability, or adverse tissue reaction to metal debris generated by suboptimal implant position leading to higher bearing contact stresses and/or impingement. Once other common etiologies of hip pain have been excluded such as deep infection or lumbar pathology, the most likely cause of hip symptoms should be considered. Here the evidence points to a malpositioned acetabular component. Systemic ion dissemination may occur in this patient but will not produce hip pain. Head-neck taper corrosion can generate metallic debris, but a more likely source of local metallic debris is edge loading or impingement of the metal-metal bearing. Leg length inequality can be distressing to a patient but will usually not result in hip pain. Component malposition is the best answer. Among the spectrum of clinical presentations following failed metal-metal total hip replacements, abductor damage from localized inflammation is one finding that can lead to hip instability. A reasonable treatment option is to repair the abductors as best as possible, with augmentation of soft-tissue repair using graft tissue, a large-diameter femoral head, and a constrained polyethylene liner. This is a challenging clinical scenario because chronic hip instability with deficient abductors is difficult to control and is an indication for the use of constrained components. Revision to a larger head and increased leg lengths will not address the underlying cause of instability. Hip resection is not necessary because this is not a septic total hip.