Mid-term Results of an Anterior Plating Via Combined Anterior Approach for complex Acetabular Fractures: A Retrospective Cohort Study


 Background: Solely anterior plating via the modified Stoppa approach might yield satisfactory outcomes for selected cases of complex acetabular fractures, however, its indications are not practically clear. Methods: Patients with complex acetabular fractures treated with solely anterior plating via the modified Stoppa approach with or without a lateral window at our trauma center between January 2013 and December 2019 were retrospectively reviewed. Fracture type was identified according the newly established three-column classification of acetabular fracture. Perioperative information was recorded, and fracture reduction was evaluated radiographically at 3 days postoperatively. Postoperative hip function was assessed at least 1 year postoperatively. Results: Twenty patients were included with an average 17 months (range, 13-28) follow-up. According to the three-column classification, 2 cases were classified as type B2.2, 8 cases as type B2.3, 3 cases as type C1, and 7 cases as type C3. The mean time from injury and surgery was 7.0 days (range, 3-13 days), operative time was 2.0 hours (range, 1.4-3.2 hours), and intraoperative blood loss was 320 ml (range, 220-450 ml). Fracture reduction was excellent in 15 cases (75%), good in 3 cases (15%), fair in 1 case (5%), and poor in 1 case (5%). Final hip function was excellent in 13 cases (68%), good in 3 cases (16%), fair in 2 cases (11%), and poor in 1 case (5%). Bony healing was achieved in all cases and few complications were reported including recoverable obturator nerve injuries in 2 patients (10%) and controllable osteoarthritis in 1 patient (5%). Conclusions: Solely anterior plating via the combined anterior approach achieved satisfactory mid-term outcomes for complex acetabular fractures with posterior column detachments. Based on the newly established three-column classification of complex acetabular fracture, the type B, C1, and C3 fractures are possibly the appropriate indications for such a simplified procedure.Trial registration informationThe trial was retrospectively registered in https://www.researchregistry.com (No. Researchregistry4862) on July 04, 2019. The first participant was enrolled on March 06, 2017.


Background
The advantages of simultaneous anterior and posterior approaches over extensile exposures allowing adequate visualization and/or palpation of the fracture to obtain an anatomic reduction [1]. The combined approach is most useful in transverse, transverse posterior wall fractures with wide anterior displacement, T type fractures with signi cant anterior-inferior displacement, or both column fractures with posterior wall involvement [1]. Controversies still exist regarding the optimal surgical approach for achieving better exposure of fracture sites, less soft tissue damage and lower complications rates in complex acetabular fractures [2][3][4][5][6][7]. Simultaneous anterior (e.g. ilioinguinal approach, pararectus approach, and modi ed Stoppa approach) and posterior approaches (e.g. Kocher-Langenbeck approach) are usually applied [8][9][10], however, they occasionally show noteworthy drawbacks (e.g. long operating time and substantial blood loss) and complications (e.g. structure damage, infection, abductor weakness, and hernia) compared with other mini-invasive approaches [11][12][13]. As a less invasive approach, the anterior modi ed Stoppa approach with or without the lateral window of the classic ilioinguinal approach allows for easier accessing the entire anterior column and pelvic bone [8,14] and for additional exposure of the quadrilateral surface and posterior column [15,16]. Adequate reduction of the posterior column can be attained through such a combined anterior approach. Practically, an ilioischial plate bridging from Page 3/15 ilium to ischial ramus to x the quadrilateral plate or lag screws to x the detached posterior column can be used. Our previous case series showed that anterior ilioischial plating in 7 patients via the modi ed Stoppa approach provides reliable internal xation of complex acetabular fractures with posterior column detachments with limited invasion, little intraoperative bleeding and few complications at 6 months postoperatively [17].
Based on the widely-used Judet and Letournel classi cation [18], indications of such a simpli ed anterior approach include the elementary and associated displaced acetabular fractures involving predominantly the anterior, incongruency of the hip joint, involvement of the weight-bearing dome, impaction of the weight-bearing dome, comminution of the articular surface, unstable hip joint, associated proximal femoral injuries (femoral neck or trochanteric fractures), associated non-orthopaedic injuries (nerve de cits and/or bowel or bladder injuries) [19]. However, the Judet and Letournel classi cation is practically cumbersome and complex and results in various inaccuracies to guide clinical decisions [20][21][22]. A three-column classi cation for acetabular fractures (Table 1) has been recently proposed and validated with higher inter-and intra-observer reliability than the Judet and Letournel classi cation [23], which might be effective to identify more proper candidates of the modi ed Stoppa approach for complex acetabular fractures with posterior column detachments. Table 1 Three-Column classi cation for acetabular fractures [22]. Therefore, the present cohort study aimed to evaluate the mid-term outcomes of the anterior plating via the modi ed Stoppa approach to treat complex acetabular fractures with posterior column detachments and to identify its possible indications based on the newly established three-column classi cation.

Study design
Patients with complex acetabular fractures operated at our trauma center by the identical senior surgeon team between January 2013 and December 2019 were retrospectively reviewed with the approval of local ethics committee (No. HO1170195). Inclusion criteria were patients with acute acetabular fractures with posterior column detachments operated via a single modi ed Stoppa approach. Patients with only anterior wall/column or roof wall/column fractures and patients accompanied with osteoporosis, osteoarthritis, or other systemic illnesses (e.g. hyperthyroidism, hyperparathyroidism, androgen de ciency, malabsorption, and neoplasia) were excluded. All patients underwent a standardized assessment including medical history, clinical examination and imaging studies. Fracture type and displacement was assessed with plain radiographs and computed tomography with 3D reconstruction. The primary endpoints were postoperative reduction (perfect reduction, imperfect reduction, poor reduction) and hip function. The secondary endpoints were infection, never damage, blood loss, and duration of operation.

Surgical procedure
All patients underwent the modi ed Stoppa approach as previously described [24]. Patients were placed in a supine position on a radiolucent table allowing for unrestricted movements of the lower extremities. The affected lower extremity was sterilized and wrapped to the middle of the thigh. The hip and knee of the affected extremity were exed slightly to relax the iliopsoas and neurovascular bundle. The modi ed Stoppa approach with or without the 1st window of the ilioinguinal approach was performed as previously described [25,26]. Foley catheter and drainage system are used to improve visualization, protect bladder, and monitor uid balance. A transverse Pfannenstiel-type incision of 12-15 cm was achieved two ngerbreadths above the pubic symphysis and deepened to the abdominal fascia. The inner part of the pelvis was approached by dissecting the exposed rectus abdominis along the linea alba. Speci cally, the corona mortis was rstly identi ed and ligated, and fracture fragments were exposed via the subperiosteal dissection along the pelvic brim. Obturator nerve and vessels passing through the obturator foramen were identi ed and protected. A Schanz screw was inserted into the proximal femur allowing for intraoperative manual traction and fractures were reduced with assistance of different reduction instruments (e.g. ball spike and reduction forceps). Fragments were temporarily xated with Kirschner wires and anatomic reconstruction of the different fracture fragments was con rmed. Infrapectineal or suprapectineal plates (3.5 mm; 8 hole) contoured along the pelvic brim was anchored with cortical screws above the sciatic notch. Another plate, termed as the "ilioischial plate", was contoured over the pelvic brim to buttress comminution or counteract posterior column medial displacement (Fig. 1).
Displaced quadrilateral surface fragments were meticulously reduced and buttressed with the bridging effect of the ilioischial plate. Anchorage of the ilioischial plate was attained with cortical screws to the iliac fossa and the safe zone between the sciatic buttress and the ischial spine. For speci c cases with comminuted fragments of the posterior column, an additional lag screw was inserted from anterior to posterior direction within the safe zone to x those fragments to provide further stabilization of the posterior fragments. Operative data was recorded for each patient including interval between injury and surgery, operative time and intraoperative blood loss.

Postoperative management
Standardized postoperative care was provided for all patients. The operated limb was elevated slightly with both hip and knee appropriately exed. Wound drainage was removed 24-72 hours postoperatively. Oral administration of celecoxib was applied for pain control and heterotopic ossi cation prevention.
Low-molecular-weight heparin was used for thrombosis prevention. Rehabilitation was initiated after 24 hours postoperatively to improve blood circulation and prevent deep vein thrombosis and muscular atrophy. Ambulation with crutches was allowed at 3 days postoperatively. Patients are generally discharged at 5 days postoperatively, when they present no complications. Partial weight-bearing exercises and ambulation without crutches were started at the postoperative 6 and 12 weeks, respectively.

Outcome evaluation
Quality of the fracture reduction was evaluated with the modi ed Matta's criteria on the plain radiographs at 3 days postoperatively [27]. Reduction was classi ed as: excellent (anatomical reduction), good (0-1 mm residual displacement), fair (2-3 mm residual displacement), and poor (> 3 mm residual displacement). Function of the affected hip was evaluated using the modi ed Merle d'Aubigné and Postel scoring system over 1 year postoperatively [28]. Hip function was considered to be: excellent (no pain, a normal gait, a range of joint motion > 75%, no sign of arthritic changes or mild joint space narrowing or sclerosis on X-ray), good (mild pain, a normal gait, a range of joint motion > 50%, joint surface sclerosis or joint space narrowing or osteophyte formation), fair (moderate pain, mild abnormality of gait, a range of joint motion < 50%, signi cant joint space narrowing or joint surface sclerosis and osteophyte formation), and poor (severe pain, obvious gait abnormality, joint stiffness with deformity, signi cant arthritic changes or obvious dislocation of the femoral head).

Statistical analysis
Descriptive statistics are used to describe the results. Data are presented as the mean ± standard deviation, range, and percentage, where appropriate.

Functional outcomes
According to the modi ed Merle d'Aubigné and Postel scoring system, the function of the affected hip joint was excellent in 13 cases (68%), good in 3 cases (16%), fair in 2 cases (11%), and poor in 1 case (5%) ( Table 3). Two patients (10%) exhibited clinical evidences of obturator nerve injury, which were recovered fully after 3 months without special medical interventions. One patient (5%) developed a symptomatic osteoarthritis at 2 years postoperatively, which was well diminished by medications. No other speci c complications were reported in other patients, including internal xation failure, postoperative infection, and heterotopic ossi cation.

Discussion
This study showed that the solely anterior plating via modi ed Stoppa approach achieved clinically satisfactory mid-term outcomes for complex acetabular fractures with posterior column detachments. Preoperative fracture type identi cation based on the novel three-column classi cation is facilitative to identify the appropriate candidates for such a simpli ed approach.
The modi ed Stoppa approach with the lateral window of the classic ilioinguinal approach is practically convenient to access fracture fragments of posterior column effectively with advantages of less blood loss, shorter operation time, and fewer complications than other traditional approaches. The average intraoperative blood loss in our cohorts was 320 mL, which was signi cantly less than blood loss with a single ilioinguinal approach ranging from 760 mL to 1170 [26,29] or simultaneous anterior (Stoppa/iliac window approach) and Kocher-Langenbeck approach ranging from 586 ml to 1252 ml [30][31][32]. Similarly, the average operative time in our cohorts (2.1 hours) is considerably shorter than the single ilioinguinal approach (2.6-4.3 hours) [26,33] and the simultaneous anterior modi ed ilioinguinal/Stoppa approach (2.1-4.4 hours) [30,31,[34][35][36]. Moreover, no heterotopic ossi cation and only two obturator nerve injury (recovered within 3 months postop) was observed in our cohorts, which are also signi cantly less than the rates of heterotopic ossi cation (25.6%), traumatic nerve palsy (16.4%), and iatrogenic nerve palsy (8.0%) in 3670 patients reported by a recent meta-analysis [37].
Previous biomechanical experiments demonstrated that a single locking plating of the anterior column provided less stability than a traditional treatment with posterior column plating and anterior column screwing [38], however, the anterior xation with multiple spring plates, especially the ilioischial plate, practically allows for a direct buttressing of posterior column fractures and provides clinically comparable stability as a posterior plating. The additional lag screws positioned from anterior to posterior direction can x the fragments of the posterior columns and achieve a rigid xation [39,40].
Here, all patients achieved radiographic bone healing at 3 months postoperatively with good or excellent fracture abduction and xation in 90% cases, which are in good agreement with a previous study reporting congruent reduction in 89% cases treated with either single (anterior or posterior) approach or simultaneous anterior-  (8) and type C3, complicated 3-column fractures. Preoperative evaluation of patient status, fracture type, extent of the displacement, the surgeon's experience is crucial [34]. For patients with obesity or history of previous low abdominal surgeries with possible local adhesions, other approaches might be favorable. Moreover, imprudent manipulation with limited exposure might cause extensive soft tissue damages and hinder the satisfactorily reduction of fractures, possibly in uencing the long-term prognosis [11,43,44]. Therefore, surgeons are recommended to start using this modi ed Stoppa approach after mastering the ilioinguinal approach to avoid possible iatrogenic injuries of the perifracture structures.
Several limitations exist in this study. The sample size of our cohorts was relatively small, and the followup is also relatively short, which might not allow to draw rm conclusions about ultimate e cacy of the anterior plating for complex acetabular fracture with posterior column detachments. Secondly, the retrospective analysis cannot allow for a detailed investigation of characteristics of our cohorts and a comparison with a possible control group. Moreover, long-term comparisons with traditional treatments are required to con rm the possible bene ts of this procedure. Strengths of this investigation include the establishment of the indications of such a simpli ed approach based on the novel three-column classi cation and the representation of its corresponding mid-term outcomes.

Conclusions
The solely anterior plating via modi ed Stoppa approach achieved satisfactory mid-term outcomes for complex acetabular fractures with posterior column detachments. Based on the newly established threecolumn classi cation of complex acetabular fracture, the type B, C1, and C3 fractures might be the appropriate indications for such a simpli ed procedure.

Declarations
Availability of data and materials The data supporting your ndings can be found and have be presented within the manuscript.