Research Article TheIschialSpineinDevelopmentalHipDysplasia:Unravelingthe Role of Acetabular Retroversion in Periacetabular Osteotomy Gerard El-Hajj , 1 Hicham Abdel-Nour, 2 Rami Ayoubi, 2 Joseph Maalouly, 2 Fouad Jabbour, 2 Raja Ashou, 1 and Alexandre Nehme 2 1 Department of Radiology, Saint George Hospital University Medical Center, University of Balamand, P.O. Box 166378, Achrafieh, Beirut 1100 2807, Lebanon 2 Department of Orthopedic Surgery and Traumatology, Saint George Hospital University Medical Center, University of Balamand, P.O. Box 166378, Achrafieh, Beirut 1100 2807, Lebanon Correspondence should be addressed to Gerard El-Hajj; gerard.hajj@gmail.com Received 18 March 2020; Revised 21 July 2020; Accepted 27 July 2020; Published 18 August 2020 Academic Editor: Allen L. Carl Copyright©2020GerardEl-Hajjetal.isisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Purpose. Radiological diagnosis of acetabular retroversion (AR) is based on the presence of the crossover sign (COS), the posterior wall sign (PWS), and the prominence of the ischial spine sign (PRISS). e primary purpose of the study is to analyze the clinical significance of the PRISS in a sample of dysplastic hips requiring periacetabular osteotomy (PAO) and evaluate retroversion in symptomatic hip dysplasia. Methods. In a previous paper, we reported the classic coxometric measurements of 178 patients with symptomatic hip dysplasia undergoing PAO where retroversion was noted in 42% of the cases and was not found to be a major factor in the appearance of symptoms. In the current study, we have added the retroversion signs PRISS and PWS to our analysis. Among the retroverted dysplastic hips, we studied the association of the PRISS with the hips requiring PAO. We also defined the ischial spine index (ISI) and studied its relationship to the coxometric measurements and AR. Results. In hips with AR, the operated hips were significantly associated with the PRISS compared to the nonoperated ones (χ 2 � 4.847). Additionally, the ISI was able to classify acetabular version (anteverted, neutral, and retroverted acetabula). A direct correlation between the ISI and the retroversion index (RI) was found, and the highest degree of retroversion was found when the 3 signs of acetabular retroversion were concomitantly present (RI � 33.6%). Conclusion. e PRISS, a radiographic sign reflecting AR, was found to be significantly associated with dysplastic hips requiring PAO where AR was previously not considered a factor in the manifestation of symptoms and subsequent requirement for surgery. Moreover, the PRISS can also serve as an adequate radiographic sign for estimating acetabular version on pelvic radiographs. 1. Introduction Subtle variations in normal anatomy of the hip joint labeled by Ganz et al. as CAM and pincer-type impingement can cause a premature contact between the head-neck junction and the anterior wall of the acetabulum leading to early hip osteoarthritis (OA). is was later confirmed by Tanzer et al., and a clear relationship between FAI and early OA was established [1–3]. Reynold defined the crossover sign (COS) and the posterior wall sign (PWS) as the radiological pa- rameters to detect acetabular retroversion on a typical AP pelvic radiograph [4]. e COS is positive in all retroversion cases, whereas the PWS is positive only in hips with deficient posterior wall. Jamali et al. confirmed that the presence of a positive crossover sign is a highly reliable indicator of ac- etabular retroversion with anatomic correlations performed on 43 cadavers [5]. However, despite being good radiological indicators, the COS and PWS both rely on difficult visu- alization of the acetabular walls [6–8]. As a result, the prominence of the ischial spine (PRIS) inside the pelvic brim emerged as a more reproducible sign reflecting acetabular retroversion because it is easier to detect. It was first described by Kalberer et al. in 2008, with excellent sensitivity and a positive predictive value [9]. It has Hindawi Advances in Orthopedics Volume 2020, Article ID 1826952, 7 pages https://doi.org/10.1155/2020/1826952