Abstract
PurposeThis study was aimed to explore (1) location on AP pelvic X-ray that displayed bone stock in anterosuperior acetabulum; (2) whether X-ray could provide enough evidence to evaluate whether bone stock could provide support for acetabular cup; (3) criteria to determine whether anterosuperior bone stock could provide sufficient support for cup on X-ray.MethodsOur study retrospectively collected 43 patients who underwent revision THA for cup loosening from 2014 to 2019. The position of anterosuperior acetabular bone stock was compared between X-ray and CT-based 3-D reconstruction. Seventy-millimeter acetabular cup was implanted simulatively to obtain the contact line between acetabular cup and superolateral remaining bone stock. The contact line length and the angle were measured. Patients were divided into cup group and cage group, and ROC curves of both contact line length and angle were drawn.ResultsThe superolateral part of acetabulum on X-ray could reflect the anterosuperior host bone stock of acetabulum according to the comparison of anteroposterior pelvic X-ray and 3-D reconstruction. Critical point was chosen when we got the highest sensitivity with a 100% specificity in ROC curves. The critical values of contact length and angle were 15.58 mm and 25.5°.ConclusionsSurgeons could assess the anterosuperior bone stock of acetabulum by AP pelvic X-ray to decide whether revision could be done merely using cup or need customized cage. Clinically, when contact line length was larger than 16 mm or contact angle was larger than 25.5°, adoption of cup could obtain primary stability in the revision surgery in most cases.
Highlights
The number of patients undergoing revision total hip arthroplasty (RTHA) is rapidly increasing [1, 2]
We concluded that when the contact angle and contact length, measured using the aforementioned measuring method, were over 25.5° and 15.58 mm, respectively, an acetabular cup could be used as a primary revision prosthesis instead of a cup cage or a customized cage
We found that the superolateral part of the acetabulum in the AP pelvic X-ray represented the anterosuperior part of the acetabulum in the 3-D model, which was consistent with our experience
Summary
The number of patients undergoing revision total hip arthroplasty (RTHA) is rapidly increasing [1, 2]. Among those who undergo RTHA, bone defects, especially acetabular bone defects, are some of the most common but difficult problems that surgeons face [3,4,5,6]. Assessment of acetabular bone defects is critical for surgical planning and preoperative preparation [7]. Significant errors may occur when different surgeons use these methods This may have adverse effects on preoperative planning [12, 17]. The role of primary assessment, the precise information that surgeons need to obtain from X-ray, and the significance of X-ray results in pre-surgical planning are still unknown
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