Case presentation
A 35-year-old female was referred to our center with right groin pain.
She had undergone total hip arthroplasty (THA) four years ago due to
ONFH following pregnancy. She had no history of fever and trauma. She
received a high dose of corticosteroid following Covid-19 infection. The
passive right hip range of motion was near full, although painful at
extremes of movement. She had a painful weight-bearing with an antalgic
gait. The neurologic examination was good, and no sign or symptom
suggestive of spinal radiculopathy. The late-onset pain, the location,
history, and examination grew us suspicious of a low-grade
peri-prosthetic joint infection (PJI).
Her radiographs demonstrated a severe right acetabular sclerosis, and a
radiolucent line around the acetabular component suggestive of loosening
of the acetabular component (Figure 1).
Her ESR was 16, and her CRP was 14. 99m-Tc bone scan revealed mild
hyper-flow at the right hip in angiography and blood pool images, and
intense uptake in delayed images. Due to the unavailability of metal
artifact reduction sequence (MARS) magnetic resonance imaging (MRI), in
our center, it had not been done. In the next step, hip aspiration took
place for her, which was negative for PJI.
So, we decided to do two-staged arthroplasty. After the acetabular
component removal, we faced severe sclerosis of acetabulum, which was
avascular. Several specimens were assembled for microbiology culture to
assess peri-prosthetic joint infection (PJI) due to high suspicion, and
pathology. A Cement spacer was also implanted. Post-op CT scan was done
to evaluate the acetabulum also confirmed sclerosis (Figure 2).
The cultures were negative for PJI, and pathology confirmed the ONA
(Figure 3).
After two weeks of antibiotic therapy the second stage was done.
Acetabular reaming was associated with a lack of bleeding. Since, we
decided to implant a cemented cup for her in that situation, by ONA
diagnosis due to inappropriate bone ingrowth.
At one year postoperatively, the patient returned for a follow-up visit,
and Radiographs were obtained at this time for routine monitoring
(Figure 4). She had no complaints and her Harris hip score was 81.