Background <p>Quadrilateral plate (QLP) acetabular fractures are technically demanding because of complex anatomy and high-energy trauma. Direct infrapectineal plating via the ilioinguinal approach provides stable fixation, although prospective data correlating reduction quality with functional outcomes remains limited.</p> Methods <p>This prospective cohort study included 25 patients with acute QLP fractures treated between January 2021 and January 2024 using direct infrapectineal plating through the ilioinguinal approach. Radiological outcomes were assessed using the Matta score and functional outcomes using the Merle d’Aubigné and Postel score. Subgroup analyses evaluated the effects of age, fracture type, associated injuries, and surgical timing on operative parameters and outcomes.</p> Results <p>Mean age was 39.7 years. Mean operative time was 160 min and mean blood loss was 850 mL. Anatomical reduction was achieved in 64% of patients, imperfect reduction in 24%, and poor reduction in 12%. Anatomical reduction was associated with significantly superior functional outcomes (17.2 ± 2.3 vs 15.1 ± 2.7 and 12.3 ± 2.5; <i>p</i> = 0.002), with moderate correlation between radiological and functional results (r = 0.58, <i>p</i> = 0.004). Older age and associated injuries increased operative complexity without affecting final outcomes. Earlier surgery (&lt; 10 days) showed a trend toward improved results. At mean follow-up of 14.7 months, excellent or good outcomes were achieved in 68% of patients. One deep infection occurred.</p> Conclusion <p>Direct infrapectineal plating was associated with satisfactory radiological and functional outcomes in quadrilateral plate acetabular fractures. Anatomical reduction strongly correlates with improved functional outcomes, while patient- and fracture-related factors mainly influence operative complexity.</p> <p><b>Clinical Trial Registration:</b> NCT07170280.</p>