ObjectiveTo compare the effectiveness of anterior subcutaneous pelvic internal fixator (INFIX) and plate internal fixation in treatment of unstable anterior pelvic ring fractures.MethodsThe clinical data of 48 patients with unstable anterior pelvic ring fractures who met the selection criteria between June 2014 and December 2019 were retrospectively analyzed. Among them, 21 cases were treated with INFIX (INFIX group), and 27 cases were treated with plate (plate group). There was no significant difference in gender, age, body mass index, cause of injury, time from injury to operation, Injury Severity Score (ISS), and fracture type between the two groups (P>0.05). The operation time, intraoperative blood loss, fracture healing time, partial weight-bearing time, and complete weight-bearing time were recorded and compared between the two groups. Matta standard was used to evaluate the quality of fracture reduction, and Majeed score system was used to evaluate the functional recovery of pelvic fracture after operation.ResultsThe patients in both groups were followed up for an average of 12.5 months (range, 6-16 months). The operation time and intraoperative blood loss in INFIX group were significantly lower than those in plate group (t=−11.965, P=0.000; t=−20.105, P=0.000). There was no significant difference in the quality of fracture reduction, fracture healing time, partial weight-bearing time, and complete weight-bearing time between the two groups (P>0.05). At 14 weeks after operation, there was no significant difference in the scores of pain, working, standing and walking, and total scores between INFIX group and plate group (P>0.05), but there were significant differences in sitting and sexual intercourse scores (t=−4.250, P=0.003; t=−6.135, P=0.006). The incidences of lateral femoral cutaneous nerve injury, femoral nerve injury, and heterotopic ossification were significantly higher in INFIX group than in plate group (P<0.05), while the incidence of incision infection was lower in INFIX group than in plate group (P<0.05).ConclusionCompared with the plate internal fixation, the INFIX internal fixation can obtain the similar effectiveness for the unstable anterior pelvic ring fracture and has the advantages of shorter operation time, less blood loss, and lower risk of infection.