The acetabular fractures are technically challenging due to the deep location in the pelvis and low degree of exposure.Although the classic ilioinguinal approach could treat most anterior acetabulum fractures,the limited surgical field and difficulty in exposure is the main obstacle surgeons should overcome.Various approaches including extended approaches and combined anterior and posterior approaches ensure adequate exposure,but high rate of complications impede it from clinical use.The Stoppa approach has been favored by the orthopedic surgeons in recent years for the minimized surgical dissection and good exposure.It allows for extensive visualization of the pelvic brim and direct manipulation of quadrilateral plate.This approach is indicated in all anterior column and wall fractures,combined anterior column and posterior hemi-transverse fractures,selected both-column fractures,transverse and T-fractures.The utilization of the Stoppa approach developed along with the evolution of the relevant theory of acetabular fractures in the past years.The development such as the precise measurement of “safe zone” and the application of new apparatus could do great help in decreasing the complications and improving the surgical results.This article summarizes the relevant literatures and provides a review of the advances in the Stoppa approach in acetabular fractures.

Objective To investigate the clinical significance and distribution of different rotational displacements on the sagittal plane in unstable pelvic fractures radiologically.Methods We retrospectively reviewed 82 patients with unilateral pelvic fracture who had been treated at our department from June 2005 to June 2015.They were 48 men and 34 women,with an average age of 43 ± 18 years.By Tile classification,there were 48 cases of type B and 34 cases of type C.Their rotational displacements on the sagittal plane of the pelvic ring were determined on the anteroposterior X-ray films of the pelvis by measuring the changed distances from the top of iliac crest to the lowest point of ischial tuberosity and to the pubic tubercle.The data were recorded for analysis of different displacements and their clinical significance.Results Of all the 82 patients,based on the preoperative radiographic evidence,36 (43.9％) showed sagittal plane rotational displacement.Of them,28 (77.8％) showed supination displacement and 8 (22.2％) pronation displacement.The preoperative CT three-dimensional reconstruction confirmed the findings from the X-ray films.Twenty-one of the 48 cases of Tile type B (43.8％) and 15 of the 34 cases of Tile type C (44.1％) showed sagittal plane rotational displacement.The success rate of closed reduction was,respectively,66.7％ (24/36) in the 36 cases with sagittal plane rotational displacement,62.5％ (5/8) in those with pronation displacement and 67.9％ (19/28) in those with supination displacement,all significantly lower than the total success rate of closed reduction in this cohort(84.1％).Conclusions The sagittal plane rotational (pronation and supination) displacement of pelvic fracture can be determined by measuring special points and lines on the anteroposterior radiographs of the pelvis.The supination displacement on the sagittal plane is more common.The unstable pelvic fracture with sagittal plane rotational displacement is more difficult to reduce.

Objective To investigate the injury and disruption of anterior sacroiliac ligament (ASIL) and sacrotuberous/sacrospinous ligament complex(STL/SSL),as well as the displacement of pubic symphysis (PS) and sacroiliac joint (SIJ),associated with anterior-posterior compression (APC) of Young-Burgess type Ⅱ.Methods Test models of APC of Young-Burgess type Ⅱ were created in 10 fresh human pelvic cadaveric specimens which were randomized into 2 equal groups (n =5).The fight hemipelvis in one group was fixed to a table (the limited group) while that in the other was not (the unlimited group).At the disruption point of ASIL during external rotation of the hemipelvis,displacement of PS,separation distance between the anterior parts of the sacroiliac joint,and injury and disruption of STL/SSL were recorded.When STL/SSL was gradually made to breakdown and fracture with continuous external rotation of the hemipelvis,bony changes and injuries to the posterior pelvic ligaments were observed and recorded.Results At the failure point of ASIL,the mean displacement of PS was 23.8 ± 2.8 mm and that of SIJ was 10.9 ± 4.4 mm,showing no significant difference between the limited and unlimited groups (P ＞ 0.05);the mean external rotation angle was 40.1°± 9.8° and the mean torsion was 646.7 ± 131.5 N,showing significant differences between the limited and unlimited groups (P ＜ 0.05).At the disruption point of ASIL,obvious injuries or disruption of STL/SSL were not observed in the unlimited group but observed in the limited group.With extreme external rotation,obvious disruption of STL/SSL was not found in the unlimited group but observed in the limited group.When ASIL and STL/SSL were all fractured,the mean displacement of PS was 41.8 mm and that of SIJ was 16.8 mm in the limited group.Conclusions Since APC injury can lead to 2 situations,limited or unlimited hemipelvis,external rotation injuries to the ligaments differ in the 2 different situations.When ASIL fails,the displacement of PS will fluctuate greatly.

Objective To compare the safe zone and safe angles between males and females for screw placement on the medial iliosciatic plate for acetabular posterior column using 3D reconstruction technique.Methods Normal pelvic CT scans of 52 adults (27 males and 25 females;aged from 18 to 74 years,averaging 47.2 years) were obtained to create pelvic 3D models.After the acetabulum was thickened by 5 mm,the width (d) of the safe zone for placement of the medial iliosciatic plate was measured.After the vertical distance (w) between the vertex of the obturator canal and the greater sciatic notch was measured,the ratio (r) of d/w was calculated.The recombined innominatum model was cut through the center of the acetabulum with a plane perpendicular to the quadrilateral plate and the greater sciatic notch.The cross-section was marked as M.In males,4 points at distances of 1.0 cm,1.5 cm,2.0 cm and 2.5 cm anterior to the greater sciatic notch were marked.At the 4 points,the angulations (∠ a,∠b,∠ c and ∠ d) between the quadrilateral plate and the tangent line of the outer edge of the thickened acetabulum model were measured on the cross-section M.In females,3 points at distances of 1.0 cm,1.5 cm and 2.0 cm anterior to the greater sciatic notch were marked before ∠a,∠b,and ∠c were measured.The differences in the above parameters were compared between males and females.Results The width (d) of the safe zone for placement of the medial iliosciatic plate was 28.56 ±2.44 mm in males and 24.36 ±2.47 mm in females;the ratio (r) was 0.61 ± 0.07 in males and 0.54 ± 0.05 in females.The safe angulations for screw placement in males,∠ a,∠b,∠cand ∠d,were 88.04°±3.18°,77.81°±3.85°,68.01°±4.11°and56.81°±4.81° while those in females,∠a,∠b and ∠c,were 91.29°±4.52°,76.23°±3.82° and 62.79°±3.51°,respectively.There were statistically significant differences between males and females in values of d,r,∠ a and ∠ c (P ＜ 0.05).Conclusions In fixation of acetabular posterior column fractures using medial iliosciatic plate,the differences between males and females should be taken into account.Besides,specific safe angles should be chosen according to the position of the plate.

Objective To explore the clinical efficacy of medial iliosciatic plating via the Stoppa approach for complex acetabular fractures involving the posterior column.Methods Between February 2015 and February 2016,a total of 16 complex acetabular facture cases treated by the medial iliosciatic plate via the Stoppa approach were retrospectively analyzed in this study.This approach provided good exposure to a large region of the pelvis and acetabulum including pubis symphysis,pubic ramus,anterior and inner wall of acetabulum,quadrilateral surface,inner surface of posterior column,true pelvic margin,greater sciatic notch and sacroiliac articulation.The anterior and column was reduced and fixed by the anterior column plate and the medial ilioseiatie plate.The screw direction and angle were adjusted according to the intraoperative X-ray.Surgical time,amount of bleeding,and relevant complications were recorded.The reduction of the posterior column fracture was evaluated by Matta scoring system on the plain X-ray of the pelvic post-surgery,and functional outcomes of the hip joint affected were evaluated one year post-surgery by the Merle d'Aubigne-Postel scoring system.All the cases were followed for at least 12 months.Results The reduction and fixation of the posterior column was accomplished in all the 1 6 patients.The average surgical time was 165.5 min (range,130-270 min).The average blood loss was 1 245.6 ml (range,600-5 600 ml).Thc intraoperative infusionof concentrated red blood cells averaged 6 units.According to the Matta scoring system,anatomical reduction was achieved in 12 cases,satisfactory reduction in 3,and poor reduction in one.The patients were followed from 12 to 22 months.According to the Merle d'Aubigne-Postel scoring system,there were 11 cases of excellent and 3 cases of good,yielding a good or excellent rate of 87.5％.The average Merle d'Aubigne-Postel score was 15.8 (range,8-18).There were 1 case of external iiiac vein rupture and 1 case of bladder rupture.Both were repaired during surgery.Superior gluteal artery rupture was found in 1 case and surgical ligation of the artery was performed during surgery.Conclusion In the treatment of complicated acetabular fractures involving the posterior column,the medial iliosciatic plating via the Stoppa approach is safe and effective,because it can provide a safe and sufficient operative field for surgeons to reduce and fix the posterior column fractures,and it leads to satisfactory recovery of the patients with limited complications.

Objective To establish a three-dimensional finite element model of pelvic anteroposterior compression (APC) for analysis of mechanisms for related liganentous damages.Methods A finite element model and a laboratory mechanical model of APC were established using the same pelvic specimens.In a finite element model of normal pelvic bones and ligaments,after the right pelvis was fixated the pubic symphysis (PS) was sectioned.Next,a manual external mobile force was gradually applied to the left hemipelvis to make the PS diastasis 10,20,30,40,60,80 and 100 mm apart.The mechanical experiment revealed the anterior sacroiliac ligament (ASIL) was ruptured when the PS diastasis reached 28 mm.After the strain value of ASIL was calculated through the finite element model,it was applied to the other pelvic ligaments.The displacement in front of the sacroiliac joint (SIJ),stress,strain and extent of injury and disruption of sacrotuberous/sacrospinous ligaments (STL/SSL) with a corresponding PS diastasis were observed and recorded.Results ASIL failed at the point when the PS diastasis was 28 mm and the displacement in front of SIJ was 7.41 ± 1.14 mm.The strain and maximum principal stress of ASIL calculated in the finite element model were 259.5％ and 543.24 MPa respectively.The maximum principal stress value of SSL was 35.00 MPa at the point of failure when the PS diastasis and the displacement in front of SIJ were 51 mm and 15.23 ±2.88 mm,respectively.When the PS diastasis and the displacement in front of SIJ were 100 mm and 7.5 mm respectively,the maximum principal stress value of STL was 16.17 MPa but the strained ligament was not ruptured.When the pelvis was rotated externally step by step,the ASIL failure was followed by the rupture of SSL but not necessarily by the STL failure.Conclusion As the finite element pelvic bone-ligament model established in this study can effectively simulate the mechanisms for APC injury,it can be used to evaluate different extents of pelvic ligamentous injury,providing a basis for the biomechanical study of pelvic bones and ligaments.

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.

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.

Objectives To put forward the modified Letournel classification of acetabular fractures,and evaluate the guiding role of the modified Letournel classification in clinical work.Methods A retrospective study of 170 patients (178 sides) with acetabular fractures treated at Nanfang Hospital between January 2006 and August 2018 was performed.Among them 129 cases were males and 41 were females.The average age was 40.2±14.2 years (range,14-82 years).According to the Letournel classification,unclassifiable/atypical acetabular fractures were found out with plain Ⅹ-ray and plain CT scan and three-dimensional CT,and then their unclassifiable reasons were analyzed.Based on anatomical landmarks,clear boundaries of acetabular walls were defined on the 3D printed pelvic model.The structure of each column is a trihedron.The wall's fracture and column's fracture were distinguished using a theory that the wall's fracture involved two surfaces of column with interruption of continuity and column's fracture involved three.When column's fracture associated with wall's fracture,lowercase a,p and q were used representing comminuted areas of corresponding anterior and posterior wall,quadrilateral plate respectively.When column's fracture didn't associates with wall's fracture,it is marked with number 0.Finally,all fractures were classified according to the modified Letournel classification.The relationship between fracture type and surgical approach was analyzed.Results There was 51.7％ (92 sides) of acetabular fractures that couldn't be classified by the Letournel classification.Incomplete fracture lines (49 sides,53.3％),comminuted fractures (28 sides,30.4％),both of them (15 sides,16.3％) were their unclassifiable reasons.There were 8 types in the modified Letournel classification,including posterior wall fracture,posterior column fracture,anterior wall fracture,anterior column fracture,transverse fracture,T-shaped fracture,anterior column+posterior hemitransverse fracture,and both columns fracture.Posterior column+posterior wall fracture,transverse+posterior wall fracture had respectively become a form of posterior column fracture and of transverse fracture.According to the modified Letournel classification,the reclassification rate of 178 side fractures was 100％,which was significantly higher than 48.3％ (86/178) of the traditional Letournel classification,and the difference was statistically significant (x2=124.06,P＜ 0.001).100％ of posterior wall fracture and 80.00％ of posterior column fracture were treated by posterior approach.100％ of anterior column fracture and 73.68％ of both columns fracture were treated by anterior approach.Conclusion All acetabular fractures can be classified by the modified Letournel classification.The orientation of the comminuted walls reflects in part severity of the injury,better helps orthopaedic surgeons understand the morphology of acetabular fractures and select appropriate surgical approach.

Objective:To evaluate internal fixation via only the modified Stoppa approach in the treatment of central hip dislocation complicated with fracture of the posterior acetabular wall.Methods:A retrospective study was conducted in the 13 patients with central hip dislocation and fracture of the posterior acetabular wall who had been treated at Department of Orthopedic Trauma, Nanfang Hospital between February 2015 and February 2018. They were 10 men and 3 women, aged from 31 to 65 years (average, 46.7 years). All patients were treated with internal fixation via only the modified Stoppa approach. The reduction of double-column and posterior wall fractures was evaluated according to the X-ray Matta scoring system, as well as to the Wiberg central-edge (CE) angles between the vertical line of the center point of the femoral head and the lateral edge of the acetabulum and acetabular tolerance on the normal and affected sides immediately after operation; the hip function was evaluated by the modified Merle d'Aubigne and Postel scoring system at 12 months after operation.Results:All patients were followed up for 16 to 52 months (average, 25.6 months). In all of them, reduction and fixation of central hip dislocation and acetabular fracture was completed successfully, and indirect reduction of posterior wall fracture and acetabular tolerance were satisfactory. Operation time ranged from 130 to 270 min, averaging 155.5 min; intraoperative blood loss from 600 to 5,600 mL, averaging 1,150.5 mL; intraoperative infusion of concentrated red blood cells from 2 to 12 U, averaging 6 U. By the X-ray Matta scoring system immediately after operation, anatomical reduction was achieved in 4 posterior wall fractures and satisfactory reduction in 9 ones. There was no significant difference between the normal and affected sides in the CE angle (43.53°±3.46° for the affected side versus 43.19°±3.28° for the normal side) or in the acetabular tolerance (76.56%±15.50% for the affected side versus 75.32%±16.24% for the normal side) ( P>0.05). The modified Merle d'Aubigne and Postel scores at 12 months after operation ranged from 12 to 18 points, averaging 16.5 points; the hip function was assessed as excellent in 9 cases, as good in 3 and as fair in one. By the last follow-up, none of the 13 patients lost fracture reduction, and their internal fixation was firm with no loosening or breakage. Conclusion:In the treatment of central hip dislocation complicated with fracture of the posterior acetabular wall, internal fixation via only the modified Stoppa approach can lead to satisfactory fracture reduction, firm fixation, good hip joint tolerance, and fine clinical efficacy.