Anterior-column acetabular fractures extending posteriorly toward the sacroiliac (SI) region without SI joint disruption represent a rare and under-recognized fracture pattern. It remains unclear whether these fractures behave as atypical anterior-column fractures or as combined pelvic-acetabular injuries that necessitate sacroiliac fixation. This study addresses the lack of systematic data on this morphology and provides a biomechanical insight that the continuity of the SI ligamentous complex preserves pelvic stability despite posterior extension. This study aims to evaluate clinical, radiological, and functional outcomes of this fracture type and to clarify whether posterior fixation is necessary. A retrospective case series was conducted, including 19 adult patients with anterior-column acetabular fractures that extended posteriorly toward the SI region, while the posterior ligamentous complex remained intact between January 2015 and January 2022. Inclusion criteria were: (1) adults aged ≥18 years, (2) patients diagnosed with acute anterior column acetabular fractures confirmed on CT, (3) fractures demonstrating posterior extension toward the SI region without evidence of diastasis or ligamentous injury. Fractures associated with SI dissociation or pelvic-ring instability, both-column fractures with complete posterior involvement, pathological fractures secondary to tumor or infection, prior ipsilateral hip or pelvic surgery, and inadequate imaging or follow-up shorter than 24 months were all excluded. Preoperative evaluation included thin-slice CT with 3-dimensional reconstruction to confirm SI integrity. All patients underwent anterior fixation via either the ilioinguinal ( n = 11) or modified Stoppa approach ( n = 8). Reduction quality, fracture union, SI stability, and functional outcomes (Harris hip score, modified Merle d’Aubigné–Postel, and Western Ontario and McMaster Universities Osteoarthritis Index scores) were assessed over a mean follow-up of (39.8 ± 13.5) months. Statistical analyses were performed with SPSS (version 27). Mean ± standard deviation was used to describe continuous variables, while categorical variables were presented as frequency and percentage. Comparisons between subgroups were carried out using Student’s t -test or Mann–Whitney U test for continuous variables, and Chi-square or Fisher’s exact test for categorical variables. A p < 0.05 was considered statistically significant. The mean age of the included patients was (45.7 ± 11.8) years. The mean union time of all fractures was (4.8 ± 0.7) months. Anatomical reduction was achieved in 16 patients (84.2%) and imperfect reduction in 3 (15.8%). No patient required SI fixation, and SI joint congruity was maintained in all cases. Functional outcomes were favorable. The mean Harris hip score at final follow-up was 88.9 ± 6.8. According to the Western Ontario and McMaster Universities Osteoarthritis Index score, 14 patients (73.7%) had excellent outcomes, 4 patients (21.1%) had good outcomes, 1 patient (5.3%) had a fair outcome, and no poor outcomes were recorded. All patients were evaluated using the modified Merle d’Aubigné–Postel score: 15 (78.9%) achieved an excellent rating, 3 (15.8%) a good rating, 1 (5.3%) a fair rating, and none were rated as poor. Complications were minimal, including 1 superficial wound infection and 1 transient lateral femoral cutaneous nerve neuropraxia. Posterior extension of anterior-column fractures without SI ligamentous disruption behaves biomechanically as an isolated acetabular injury, obviating the need for posterior fixation. Accurate preoperative CT assessment and intraoperative verification enable safe anterior fixation, ensuring union, stable SI articulation, and excellent function. These findings highlight a distinct morphologic variant overlooked by current classification systems, warranting refinement to integrate functional stability criteria. • Anterior-column acetabular fractures may extend toward the sacroiliac region without true sacroiliac joint or ligamentous disruption, representing an under-recognized fracture morphology. • Posterior extension of the fracture line alone does not equate to pelvic-ring instability; preservation of the sacroiliac ligamentous complex maintains biomechanical pelvic stability. • High-resolution CT with three-dimensional reconstruction is essential to differentiate this atypical anterior-column fracture from combined pelvic–acetabular or crescent-type injuries. • Isolated anterior fixation via ilioinguinal or modified Stoppa approaches achieves reliable fracture union, maintained sacroiliac congruity, and excellent functional outcomes without sacroiliac fixation. • These findings support a functional, stability-oriented fracture concept and highlight limitations of current classification systems, advocating refinement based on ligamentous integrity rather than fracture trajectory alone.
Fahmy et al. (2026) studied this question.