A Pilot Three-Dimensional Evaluation of Acetabular Bony Coverage After Modified Spitzy Shelf Acetabuloplasty

Modified Spitzy shelf acetabuloplasty is a joint-preserving surgical procedure for acetabular dysplasia that aims to enhance bony coverage of the hip joint. Although prior studies have primarily relied on two-dimensional (2D) radiographic evaluations, comprehensive three-dimensional (3D) assessments remain limited. The purpose of this retrospective study was to evaluate changes quantitatively in acetabular coverage following modified Spitzy shelf acetabuloplasty using 3D models reconstructed from computed tomography (CT) images. We retrospectively analyzed 11 hips in 11 patients who underwent staged bilateral modified Spitzy shelf acetabuloplasty. Preoperative and postoperative CT data were used to construct 3D pelvic models, which were registered using anatomical landmarks. Bone graft dimensions, insertion angle, and placement location were evaluated. Acetabular sector angles (ASA), representing circumferential coverage of the femoral head, were measured at 15° intervals on the functional pelvic plane and the anterior pelvic plane. The mean bone graft dimensions were 26.3 ± 3 mm (anteroposterior length) and 12.7 ± 2.7 mm (mediolateral length), providing coverage of 49.5° ± 9.1°. Postoperative ASA increased significantly from 34.5° to 60° on the functional pelvic plane and from 0° to 45° on the anterior pelvic plane (both p < 0.05). 3D analysis demonstrated that modified Spitzy shelf acetabuloplasty effectively enhanced anterosuperior acetabular bony coverage. Although this is a report of a few cases (11 hips), the above findings highlight the value of 3D evaluation in identifying postoperative changes that may not be detected using conventional 2D assessments. Also, further research analyzing the three-dimensional bone graft model revealed in this study may help inform the development of a more ideal biomimetic approach, not only in terms of shape but also function.