From the Guidelines
A 3-phase bone scan is not routinely indicated for periprosthetic fracture after Total Knee Replacement (TKR).
Rationale
- The evidence suggests that while bone scintigraphy may be helpful in diagnosing loosening, especially when obtained many years after surgery 1, its utility in diagnosing periprosthetic fracture is limited.
- The 3-phase bone scan is moderately sensitive (76%) in identifying the failed joint prosthesis but with a specificity of only 51% and an accuracy of 50% to 70% 1.
- Periprosthetic uptake on bone scan is a nonspecific finding and cannot differentiate infection from aseptic loosening 1.
- Normal bone scans have a high negative predictive value (NPV) and indicate that infection, loosening, or fracture is unlikely 1.
Key Points
- Bone scintigraphy may be useful as a screening test, with a high NPV, but its accuracy is lower than that of other tests such as WBC or FDG-PET/CT scan 1.
- A positive 3-phase bone scan demonstrates increased periprosthetic uptake in both focal and diffuse patterns, but even with SPECT/CT, it can still be difficult to distinguish between infection and aseptic loosening 1.
- The use of 3-phase bone scintigraphy does not improve the accuracy of the test compared to a single-phase bone scan 1.
From the Research
Indications for 3-Phase Bone Scan
- A 3-phase bone scan is a potential first-line nuclear medicine study for pain after total joint arthroplasty (TJA) when there is concern for periprosthetic joint infection or aseptic loosening 2
- The scan may be useful in the situation where abnormal serology is present, but where repeated joint aspirations samples are inconclusive 3
Diagnostic Accuracy
- A 3-phase bone scan has a positive predictive value of 2.53%, a negative predictive value of 100%, with an overall accuracy of 34.75% in the diagnosis of infection, or loosening with concurrent infection 3
- The scan may have falsely positive findings due to normal physiologic bone remodeling for up to 2 years after TJA 2
Periprosthetic Fractures after Total Knee Replacement
- Periprosthetic fractures after total knee arthroplasty may occur in any part of the femur, tibia, and patella, with the most common pattern involving the supracondylar area of the distal femur 4
- Risk factors for periprosthetic fractures include anterior femoral cortical notching, use of the rotational constrained implant, loose components, and malalignment or malposition of implants 5, 4
Treatment of Periprosthetic Fractures
- Treatment of periprosthetic fractures around the knee should be individualized, considering the stability of the prosthesis, displacement of fracture, and bone quality 4, 6
- Operative stabilization by plate fixation, intramedullary nailing, or revision arthroplasty may be necessary for displaced fractures or fractures with unstable prosthesis 6