Lower abdominal cyst complicated with infection following INFIX internal fixation for pelvic fracture: A report of 2 rare cases

Abstract Background: The Internal Fixator (INFIX) is a popular method for treating anterior pelvic ring fractures, known for its minimal invasiveness, and short operation time. However, studies have shown that postoperative complications may occur, including anterolateral femoral cutaneous nerve injury, the femoral nerve paralysis, and delayed fracture healing. These complications are believed to be related to surgical stimulation, an excessively long lateral end of the connecting rod, a small distance between the screw and bone surface, insufficient pre-bending of the connecting rod, and difficulties in fracture reduction. Case Presentation: We report two unique cases of lower abdominal pseudocyst complicated with infection after INFIX treatment of pelvic fractures at our trauma center.Following surgical removal of the internal fixation, resolution of the cysts was observed in both patients, and subsequent postoperative follow-up revealed the absence of any residual sequelae.These cases have not been reported in previous literature reviews. Discussion: The lower abdominal cysts, potentially arising from the dead space created during intraoperative placement of the INFIX rod, which may increase infection risk. The etiology remains uncertain, despite the presence of abnormal inflammation markers in both cases, and staphylococcus aureus found in one. These cysts were confined to the lower abdomen, not involving the internal fixation, and hence, only the INFIX was removed. Postoperative oral cefazolin treatment was successful, with resolved pseudocysts and no subsequent discomfort. Conclusion: We report two unprecedented cases of post-INFIX abdominal cysts, with a suspected link to intraoperative dead space. Despite uncertain etiology, successful management involved INFIX removal and oral cefazolin therapy. These findings necessitate further exploration into the causes and management of such complications.