Background: Periprosthetic acetabular fractures following primary total hip arthroplasty (THA) using a cementless acetabular component range from occult to severe fractures. The aims of this study were to evaluate the perioperative periprosthetic acetabular fracture rate and patient-specific risks of a modular cementless acetabular component.

Methods: In this study, we included 7,016 primary THAs (61.4% women, 38.6% men; age, 67 years; interquartile range, 58 to 74) that received a cementless, hydroxyapatite coated, modular titanium press-fit acetabular component from a single manufacturer between January 2013 and September 2022. All perioperative radiographs and computed tomography scans were analyzed for all causes. Patient-specific data and the revision rate were retrieved, and radiographic measurements were performed using artificial intelligence-based software. Following matching based on patients' demographics, a comparison was made between patients who had and did not have periacetabular fractures in order to identify patient-specific and radiographic risk factors for periacetabular fractures.

Results: The fracture rate was 0.8% (56 of 7,016). Overall, 33.9% (19 of 56) were small occult fractures solely visible on computed tomography. In addition, there were 21 of 56 (37.5%) patients with a stable small fracture. Both groups (40 of 56 (71.4%)) were treated nonoperatively. Revision THA was necessary in 16 of 56, resulting in an overall revision rate of 0.2% (16 of 7,016). Patient-specific risk factors were small acetabular component size (≤ 50 mm), a low body mass index (< 24.5), a higher age (> 68 years), women, a low lateral central-edge angle (< 24°), a high extrusion index (> 20%), a high Sharp angle (> 38°), and a high Tönnis angle (> 10°).

Conclusions: A wide range of periprosthetic acetabular fractures were observed following primary cementless THA. In total, 71.4% of acetabular fractures were small cracks that did not necessitate revision surgery. By identifying patient-specific risk factors, such as advanced age, women, low body mass index, and dysplastic hips, future complications may be reduced.