1. What are the findings?
The patient has had a total right hip arthroplasty. The prosthesis is non cemented. Careful evaluation of the prosthesis demonstrates the femoral head lies asymmetrically in the acetabular component with narrowing of the superior joint space. There is also bony debris versus heterotopic bone in the superior right hip joint space.
Also note the bone in the region of the greater trochanter appears osteopenic compared to the other osseous structures. This represents a phenomenon known as stress shielding - a decrease in bone density over time due to the strength and shift in load bearing from the bone to the metal prosthesis. This is not considered a complication but a positive finding.
Diagnosis: Wear of the acetabular liner.
2. What are features to look for in imaging the post operative hip?
There are mutiple complications that can occur with joint replacement hardware and careful examination is required to exclude them. Comparison with prior studies should ALWAYS be performed when available as subtle changes may be easily overlooked. Some examples of post joint replacement complications include:
The patient has had a total right hip arthroplasty. The prosthesis is non cemented. Careful evaluation of the prosthesis demonstrates the femoral head lies asymmetrically in the acetabular component with narrowing of the superior joint space. There is also bony debris versus heterotopic bone in the superior right hip joint space.
Also note the bone in the region of the greater trochanter appears osteopenic compared to the other osseous structures. This represents a phenomenon known as stress shielding - a decrease in bone density over time due to the strength and shift in load bearing from the bone to the metal prosthesis. This is not considered a complication but a positive finding.
Diagnosis: Wear of the acetabular liner.
2. What are features to look for in imaging the post operative hip?
There are mutiple complications that can occur with joint replacement hardware and careful examination is required to exclude them. Comparison with prior studies should ALWAYS be performed when available as subtle changes may be easily overlooked. Some examples of post joint replacement complications include:
- Loosening of cemented prosthesis, migration of components, and cement failure.
2. Wear of the prosthetic components.
The femoral component should sit centered within the acetabulum. Any asymmetry is suggestive of linear wear. This is especially important as wear of the liner produces microparticulate joint debris which may stimulate a histiocytic response resulting in osteolysis.
3. Fracture.
The femoral component should sit centered within the acetabulum. Any asymmetry is suggestive of linear wear. This is especially important as wear of the liner produces microparticulate joint debris which may stimulate a histiocytic response resulting in osteolysis.
3. Fracture.
4. Prosthesis dislocation.
5. Infection.
May be difficult to assess and may require joint aspiration for definitive diagnosis. Infection should be considered if there is persistent pain 3 months after the procedure orin the presence of abnormal lab results (elevated white counts, ESR, and CRP). Poor post op wound healing or persistent drainage also increases the risk for infection. Differentiating between loosening due to wear or cement failiure versus loosening due to infection may be difficult in the absence of secondary bony signs of infection such as periosteal reaction.
May be difficult to assess and may require joint aspiration for definitive diagnosis. Infection should be considered if there is persistent pain 3 months after the procedure orin the presence of abnormal lab results (elevated white counts, ESR, and CRP). Poor post op wound healing or persistent drainage also increases the risk for infection. Differentiating between loosening due to wear or cement failiure versus loosening due to infection may be difficult in the absence of secondary bony signs of infection such as periosteal reaction.
6. Post surgical heterotopic bone formation.
This is a rare complication, however extensive ossification of the soft tissue may cause joint motion problems. Patients with a history of heterotopic bone formation, hypertrophic osteoarthritis, or diffuse idiopathic skeletal hyperostosis (DISH) may be at greater risk of heterotopic bone formation.
7. Metallosis.
This is a rare complication, however extensive ossification of the soft tissue may cause joint motion problems. Patients with a history of heterotopic bone formation, hypertrophic osteoarthritis, or diffuse idiopathic skeletal hyperostosis (DISH) may be at greater risk of heterotopic bone formation.
7. Metallosis.