THA may lead to remodeling of the sacrum, development of sacral insufficiency fractures
Results showed patients who undergo unilateral total hip arthroplasty may experience decreases in bone mineral density at the sacral ala contralateral to the arthroplasty, which can lead to the development of sacral insufficiency fractures.
Isabel Graul, MD, and colleagues retrospectively analyzed data on 50 patients with sacral insufficiency fractures (SIFs) who were treated with THA, 31 of whom were treated with unilaterally implanted press-fit metal or polyethylene acetabular cups. According to the study, patients who underwent hemiarthroplasty, bilateral THA or were treated with cemented cups were excluded. Graul and colleagues used the data to determine the rate of SIF ipsilateral and contralateral to the THA. Additionally, the researchers used CT scans to analyze a second cohort of 39 patients who underwent THA with healthy bone to determine changes in bone mineral density (BMD) at the sacral ala ipsilateral and contralateral to the THA. All data were analyzed at 1 year of follow-up.
Of the 31 patients with SIFs who were treated with unilateral THA, 42% had an SIF contralateral to the THA; 19% had an SIF ipsilateral to the THA; and 39% had bilateral SIFs. After scanning for BMD in patients without SIFs, Graul and colleagues found median BMD decreased from 35 Hounsfield units (HU) to 13 HU at the sacral ala contralateral to the THA. Median BMD also decreased from 24 HU to 17 HU at the sacral ala ipsilateral to the THA; however, researchers determined this decrease was not significant.
“This leads us to conclude that THA leads to spatially different bone remodeling of the posterior pelvic ring because of altered load transmission,” Graul and colleagues wrote in the study. “This remodeling either negatively affects the contralateral side of the sacrum (as demonstrated in the present study) or prevents natural bone loss at the ipsilateral sacrum. Additional studies focusing on this remodeling process, and assessing different implant designs and longer-term changes, are needed,” they concluded.
Editor's Note: This article was updated on Dec. 7, 2021 with more detailed information on the type of acetabular cups used in the cohort.