BackgroundLateral　compression　type1　(LC-1)　pelvic　fractures　represent　a　wide　spectrum　of　heterogeneous　injuries.　These　include　both　stable　and　unstable　patterns;　however,　determining　whether　a　LC-1　fracture　is　stable　or　unstable　is　a　challenge,　and　the　method　used　to　evaluate　fracture　stability　is　complicated.MethodsWe　prospectively　collected　and　analyzed　data　from　22　patients　with　LC-1　pelvic　fractures,　who　underwent　ultrasonography　and　a　pelvic　compression　and　separation　test,　in　order　to　evaluate　the　role　of　ultrasonography　in　determining　fracture　stability　and　assist　decision-making　for　treatment　strategy.ResultsTwenty-two　patients　(15　men　and　7　women)　were　included　in　the　study.　Following　an　ultrasound　examination,　10　patients　were　classified　into　the　stable　group　and　12　into　the　unstable　group.　In　total,　13　patients　received　conservative　treatment　and　9　underwent　surgery.　At　follow-up,　there　were　no　differences　in　fracture　healing　times　or　fracture-related　complications　between　the　two　groups.　The　Majeed　score　was　comparable　between　the　two　groups　and　most　patients　recovered　well.　There　was　a　moderate　degree　of　consistency　in　Kappa　values　(Kappa=0.571,　P=0.01)　between　the　classification　of　stability　and　the　final　treatment　received.　In　addition,　the　sensitivity　of　ultrasonography　was　66.67%　and　the　specificity　was　76.92%.ConclusionsIn　conclusion,　ultrasonography　is　a　useful　tool　for　diagnosing　the　stability　of　LC-1　pelvic　fractures　and　assists　the　determination　of　treatment　strategy.　Left-right　mobility　0.3cm　may　be　used　as　the　criterion　for　determining　instability.Trial　registrationChiCTR-DDD-16008722.