Objective To compare the clinical efficacy of posterior minimally invasive reconstruction plate and 3D-navigated percutaneous sacroiliac screw fixation of elderly patients with posterior pelvic ring fractures.Methods A retrospective cases control study was performed to analyze the data of 75 elderly patients with posterior pelvic ring fractures admitted from January 2014 to June 2018 in Central Hospital of the PLA.There were 32 males and 43 females,with the age range of 60-83 years (mean,67.7 years).Twenty-four patients in the plate group were treated by posterior minimally invasive reconstruction plate fixation,and 51 patients in the navigation group were treated by percutaneous sacroiliac screw internal fixation with 3 D navigation.The operation time,intraoperative blood loss,X-ray exposure time,complication rate and postoperative visual analogue scale (VAS) were compared between the two groups.Postoperative Matta radiographic criteria was used to assess fracture reduction quality,and Majeed criteria was used to assess pelvic function at the last follow-up.Results All 75 patients were followed up for 6-24 months (mean,13.5 months).The operation time,intraoperative blood loss and X-ray exposure time in the plate group were (126.1 ± 20.6) minutes,(251.6 ± 50.8) ml,and (15.7 ±4.4)s,showing significant differences in comparison with the navigation groups [(49.7 ± 17.5)minutes,(22.8 ±5.1) ml,and (112.8 ± 8.8) s] (P ＜0.05).The incidence of postoperative complications was not significantly different between the plate group (4％) and the navigation group (4％) (P ＞0.05).At day 3,one week,and one month postoperatively,the VAS in the navigation group was (3.3 ± 0.7) points,(3.2 ± 0.7) points,(2.4 ± 0.6) points,better than that in the plate group [(7.2 ± 0.7) points,(6.2 ± 0.8) points and (4.5 ± 0.7) points] (P ＜ 0.05).However,there was no significant difference between the two groups at 3 months and one year after operation (P ＞ 0.05).According to the Matta radiographic criteria,the excellent and good rate was 92％ in plate group (excellent in 14 cases,good in 8,and fair in 2),and was 82％ in the navigation group (excellent in 25 cases,good in 17 and fair in 9).There was no significant difference between the two groups (P ＞0.05).According to the Majeed criteria at the follow-up,the excellent and good rate was 96％ in the plate group (excellent in 15 cases,good in 8 and fair in 1),and was 94％ in the navigation group (excellent in 35 cases,good in 13 and fair in 3).The difference between the two groups was not statistically significant (P ＞ 0.05).Conclusion For elderly patients with osteoporotic posterior pelvic ring fractures,percutaneous sacroiliac screw fixation under 3D navigation has the advantages of shorter operation time,less bleeding,less radiation dose and less postoperative pain than minimally invasive reconstruction plate internal fixation,and hence deserves clinical application.