Objective To investigate the reliability of using the pubic symphysis diastasis of 25 mm and anterior separation distance of sacroiliac joint to differentiate anteroposterior compression (APC) type Ⅰ and Ⅱ injuries as well as assess the injury severity.Methods A total of 11 (seven males and four females) fresh cadaver specimens with 22 hemipelvis were collected.The pelvic APC injury test models including fixed hemipelvis (restricted group) and unfixed hemipelvis (non-restricted group) were established,with 11 hemipelvis in each group according to the random number table method.Meanwhile the specimens were divided into male group (14 hemipelvis) and female group (eight hemipelvis),simulating APC type injury external rotation hemipelvis.The public symophysis interval and anterior interval of sacroiliac joint of the original pelvis,the pubic symphysis diastasis and anterior diastasis of sacroiliac joint after anterior tibiofibular ligament failure,as well as the affected pelvis ligament and sacral ligament injury were recorded and compared between the restricted and non-restricted groups,male and female groups.Results There were no significant differences in the public symphysis interval of the original pelvis and anterior interval of sacroiliac joint between the restricted group and the non-restricted group (P ＞ 0.05).The pubic symphysis interval of the original pelvis was [(5.13 ± 0.61) mm] in male group and (4.03 ± 0.84)mm] in female group (P ＜ 0.05).When the anterior tibiofibular ligament ruptured,the pubic symphysis diastasis distance was (23.36 ± 7.27) mm,ranging from 12 to 41 mm,and the diastasis distance of anterior sacroiliac joint was (9.82 ± 3.25)mm,ranging from 5 to 18 mm.In terms of the public symphysis interval,there were no significant differences between male and female groups,restricted and the non-restricted groups (P ＞ 0.05).In terms of anterior interval of sacroiliac joint,there was significant difference between male and female groups (P ＜ 0.05) but no significant difference between the restricted and non-restricted groups (P ＞ 0.05).In the restricted group,sacrotuberous ligament injuries were found in four patients,and sacrospinous ligament injuries in five,whhile there were no obvious sacrospinous ligament and sacrotuberous ligament injuries in non-restricted group.There were 10 specimens with the pubic symphysis diastasis ≥23.36 mm and 10 specimens with the diastasis distance of anterior sacroiliac joint ≥9.82 mm (46％),and there were 15 specimens with at least the pubic symphysis interval ≥ 23.36 mm or the anterior interval of sacroiliac joint ≥ 9.82 mm (68％).Conclusions The public symphysis interval ≥ 23.36 mm or anterior interval of sacroiliac joint ≥ 9.82 mm can distinguish anteroposterior compression Ⅰ from Ⅱ injuries,and the combination of the two criteria can be beneficial to assessment of pelvic injury severity.

Objective To summarize the complications and their incidences following Anterior Subcutaneous Internal Pelvic Fixation(ASIPF).Methods A comprehensive search was conducted of PubMed Library,Cochrane Library,Web of Science,SinoMed,Wanfang Data and China National Knowledge Internet for all articles addressing the postoperative complications of ASIPF published in English and Chinese from January 2009 to November 2018.A proportion Meta-analysis across the studies was performed for the complications after ASIPF (lateral femoral cutaneous nerve irritation,femoral nerve palsy,heterotopic ossification,infection and implant failure) using R software.Results This meta-analysis included 29 clinical studies involving a total of 825 patients.The complications following ASIPF were lateral femoral cutaneous nerve irritation,femoral nerve palsy,heterotopic ossification,infection and implant failure;their incidences were respectively 12％ (95％ CI:from 7％ to 19％),3％ (95％ CI:from 2％ to 4％),30％ (95％ CI:from 22％ to 39％),4％ (95％ CI:from 3％ to 6％) and 4％ (95％ CI:from 3％ to 6％).Conclusions Lateral femoral cutaneous nerve irritation and heterotopic ossification are common complications following minimally invasive internal fixation for anterior pelvic ring injury.High-quality clinical research is needed into the factors leading to the complications and into their preventive countermeasures.

Objective To investigate the biomechanical stability of 5 kinds of internal fixation for acetabular T-shaped fractures using finite element analysis.Methods After a three-dimensional model of normal pelvis was reconstructed using Mimics software,the model of acetabular T-shaped fracture was divided by Solidworks software.Models of acetabular T-shaped fracture fixated by 5 methods were reconstructed:(A) a reconstruction plate for anterior column + lag screws for posterior column,(B) lag screws for anterior column + a reconstruction plate for posterior column,(C) a reconstruction plate for anterior column + a medial ilioischial plate for posterior column (combination plating),(D) retrograde lag screws for 2 columns,and (E) a reconstruction plate for anterior column + and a posterior ilioischial plate for posterior column.Valuation was conducted with software Ansys to simulate 600 N loading on the terminal plate of S1 vertebral body at standing and sitting positions.The biomechanical stabilities were compared between the 5 models of internal fixation.Results At standing and sitting positions,the displacements of anterior column in modelA (0.522±0.121 mmand0.762±0.181 mm),modelC (0.512±0.207mmand0.730±0.181mm) and model E (0.513 ± 0.184 mm and 0.733 ± 0.166 mm) were significantly smaller than those in model B (0.622±0.224 mmand 1.328±0.537 mm) and in modelD (0.655±0.174mm and 1.591± 0.270 mm) (P ＜ 0.05).However,there were no statistically significant differences in anterior column displacements between models A,C and E or between models B and D (P ＞ 0.05).At standing and sitting positions,the displacements of posterior column in model B (0.631 ± 0.151 mm and 0.572 ± 0.693 mm),in model C (0.621 ± 0.195 mm and 0.538 ± 0.075 mm) and in model E (0.625 ± 0.192 mm and 0.544 ± 0.063 mm) were significantly smaller than those in model A (0.742 ±0.140 mm and 0.715 ±0.072 mm)and in modelD (0.754±0.247 mm and 0.717 ± 0.071 mm) (P ＜0.05).However,there were no statistically significant differences in posterior column displacements between models B,C and E or between models A and D (P ＞ 0.05).Conclusions In the treatment of acetabular T-shaped fractures,reconstruction plating has better stability than screwing.Reconstructive plating shows the best stability for anterior and posterior columns,followed by combination plating which is the best choice for reducing surgical injury.