Review Question - QID 5607

Figures A-C show a cementless Austin-Moore hemiarthroplasty with pedestal formation at the distal aspect of the stem with a large radiolucent line in Gruen zones 5 and 6. This, along with her clinical presentation of thigh and knee pain, is most consistent with aseptic loosening.

Aseptic loosening is a common reason for revision hip arthroplasty and should be considered in any patient who presents with groin, buttock or thigh pain after a hip replacement. In this situation, ESR and CRP values were within defined limits, making infection highly unlikely. Common reasons for aseptic loosening include poor initial fixation, osteolysis, and mechanical loss of fixation over time. Signs that are suggestive of aseptic loosening include progressive radiolucent lines, change of implant position on sequential radiographs, a positive bone scan, and pedestal formation at the distal aspect of a femoral stem. In this situation, there were no prior radiographs available, but her clinical presentation, pedestal formation, and large radiolucent line suggest motion of the prosthesis within the canal.

Portillo et al. reviewed 112 patients undergoing revision surgery after hip, knee, shoulder and elbow arthroplasty. Aseptic loosening was the most common reason for revision. Revisions <2 years from the time of surgery were most commonly due to infection.

Lombardi et al. reviewed 498 patients who underwent hip arthroplasty surgery (both primary and revision) with ultraporous acetabular components to determine if smoking is a risk factor for early failure. They found failure rates of 10% in both current and past smokers, compared to 3% in non-smokers.

Illustrations A and B show the post-operative images with a tapered cone femoral prosthesis. Illustration C shows a closer view of the pedestal at the end of the uncemented femoral stem.

Incorrect Answers:
Answer 1: While it is certainly possible this patient has a degree of acetabular erosion (arthritis), her presentation and radiographs are more suggestive of aseptic loosening.
Answer 2: In this situation, and without radiographs to support the diagnosis, aseptic loosening of the femoral component is a better answer.
Answer 3: Abductor tears would more commonly cause a limb and weakness.
Answer 4: Spinal stenosis should always be considered in patients with lower extremity pain, but given her radiographic findings, aseptic loosening is the better answer.