The Treatment Advantage of Complex Acetabular Fractures by the Pararectus Approach

Background: The surgical treatment of complex acetabular fractures is one of the most challenging procedures for orthopedic surgeons. The Pararectus approach, as a reasonable alternative to the existing surgical procedures, was performed for the treatment of complex acetabular fractures involving the anterior column. This study aimed to evaluate outcome using the Pararectus approach for acetabular fractures involving anterior columns. Methods: Thirty-seven with displaced complex acetabular fractures involving anterior columns were treated between July 2016 and October 2019 using the Pararectus approach. The functional outcomes (using the Merle d Aubigné and Postel scoring system, WOMAC and modied Harris scoring), the quality of surgical reduction (using the Matta criteria), and postoperative complications were assessed with about 26 months follow-up. Results: Thirty-seven patients (mean age 53 years, range: 30-71; 28 male) underwent surgery. Mean intraoperative blood loss was 840 ml (rang: 400-2000 ml) and mean operating time was 210 min (rang: 140-500 min). The modied Merle d Aubigné score was excellent and good in 27 cases (73%), fair in 6 cases (16%), and poor in 3 cases (12%). The mean score was 88.5 (range:77-96) for the modied Harris Hip scores, and 22 (range:7-35) for the WOMAC scores after operation. Postoperative functional outcomes were signicantly improved compared with preoperative outcomes (P<0.0001). The quality of reduction was anatomical in 21 cases (57%), satisfactory in 9 cases (24%), and unsatisfactory in 7 cases (20%). At follow-up, four patients developed a DVT, and heterotopic bone formation was observed in one patient. The hip osteoarthritis was not observed. Conclusion: The Pararectus approach achieved good functional outcomes and anatomical reduction in the treatment of complex acetabular fractures involving anterior column with minimal access morbidity.


Background
Anatomical reduction of complex acetabular fractures was crucial for good clinical outcomes [1]. It was important to obtain accurate reduction of acetabular fracture by an optimal surgical approach, as both were related to improved functional outcome [2]. Therefore, good exposure of operative eld through a surgical approach is required for achieving anatomic reduction of acetabular fractures owing to complex fracture patterns.
Management of anterior column acetabular fractures is becoming more challenging because of complex fracture patterns involving quadrilateral plate, medial displacement of the femoral head and superomedial dome impaction [3]. The ilioinguinal approach was regarded as the standard for the treatment of anterior column acetabular fractures [4]. However, the access morbidity of this approach was high on account of the extended access and without direct visualization of the articular acetabulum [5].
The modi ed Stoppa approach was viewed as a less invasive alternative for surgical access [6]. It was reported that modi ed Stoppa approach improved reduction quality of acetabular fractures compared with the ilioinguinal approach [7]. Rocca et al.[8] showed that the modi ed Stoppa approach was required in combination with the ilioinguinal approach to overcome their respective limitations. Existing surgical approaches do not provide good access that makes it di cult for surgeons to visualise all the components of acetabular fracture.
Recently, Keel et al. [9] described a novel anterior approach for complex acetabulum fracture that was called the Pararectus approach, which facilitated anatomical restoration and direct access to the quadrilateral plate and acetabular dome with minimal morbidity related to the surgical access. So far, only few studies have reported on this new approach about functional outcomes and complications. This retrospective study evaluated functional outcomes and anatomical restoration of the Pararectus approach in the treatment of displaced complex acetabular fractures involving the anterior column during the mid-term follow-up.

Methods
Patients A consecutive series of 37 patients included (mean age 53 years, range 30-71; 28 male) was treated between July 2016 and October 2019. All patients were treated by the Pararectus approach as a main surgical approach. Acetabular fractures were assessed preoperatively using CT and classi ed according to the Judet and Letournel classi cation as described previously [4]. Patients demographic including age, gender, mechanism of injury, fracture classi cation, and preoperative details were evaluated.
Inclusion criteria contained complex acetabular fractures less than three weeks after trauma involving the anterior column, and patients nally followed up 20 months at least after surgery. Exclusion criteria included patients younger than 18 years, patients suffering concomitant femoral fractures, bilateral acetabular fractures, or isolated posterior wall fractures, as well as patients with fracture-related nerve damage, and with pre-existing ipsilateral hip disease. Additional small incision was performed for xing the contralateral pelvic ring fracture if necessary.

Surgical technique
Surgical interventions were performed by the same team of experienced senior surgeons in our hospital according to the reports by Keel et al. [9,10]. Brie y, skin incision started cranially at the junction of the lateral-middle thirds of the line connecting the anterior superior iliac spine with the umbilicus. The incision ended at the junction of the middle-medial third of the line connecting the anterior superior iliac spine with the symphysis (Fig. 1). The extraperitoneal space was entered after dissection of the rectus sheath and incision of the transversalis fascia in a longitudinal direction. The peritoneum was retracted cranially; the ilioinguinal nerve, lateral femoral cutaneous nerve, genitofemoral nerve and the obturator vessels were protected; spermatic cord and external iliac vessels were identi ed. The direct intraoperative vision into the quadrilateral plate and posterior column was provided clearly in order to anatomical reduction and positioning of internal xation plate (Fig. 2). It was noted that the vascular anastomosis (corona mortis) between the epigastric or external iliac and obturator vessels was identi ed, ligated and divided to allow good exposure during the procedure. For fracture xation, reconstruction plates and cortical screws were used, as reported by Culemann et al. [11]. Posterior column screws were inserted to enhance xation of the posterior column fracture according to the reports by Mu et al. [12]. In addition, patients with high iliac crest fractures required an additional small incision to reduce and x the fractures if necessary.
Intravenous antibiotic prophylaxis was administered for 48 hours after operation. Subcutaneous injection of low molecular weight heparin was provided daily during hospitalization and rivaroxaban was taken orally until ve weeks postoperatively after discharge as an antithrombotic prophylaxis. Rehabilitation training started immediately, and patients were allowed toe-touch weight-bearing after eight weeks postoperatively and proceeded to full weight-bearing after fracture healing.

Evaluation
The surgical details including the delay to surgery, operative time, blood loss, operative complications were assessed. Patients were routinely followed up at 1,3, 6, 12 and 24 months postoperatively. Final clinical follow-up outcomes were assessed using the modi ed Harris Hip Score [13], the Merle d Aubigne and Postel grading [14], and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [15]. Clinical outcomes were classi ed as excellent (18 points Radiological outcomes were assessed preoperatively and postoperatively by X-rays and CT scans. The "step" (vertical displacement of articular surface fragment) and "gap" (horizontal separation of the intraarticular fracture) were measured using CT scans for assessment of fracture reduction. We selected the maximum preoperative and postoperative sizes of the "step" and "gap" in three planes (axial plane, coronal plane and sagittal plane) as an assessment of fracture displacement. Quality of fracture reduction was assessed according to Matta criteria, including anatomic reduction (0-1 mm), satisfactory reduction (2-3 mm), or unsatisfactory reduction (>3 mm), based on CT measurements [17,18].

Statistical analysis
Preoperative and postoperative data were recorded and analyzed by SPSS 16.0 (SPSS Inc, Chicago, IL). Date was presented as the mean ±SD. An analysis of variance with post hoc test was performed to determine the statistical differences for preoperative and postoperative date of normal distribution. A P value < 0.05 was set as the level of statistical signi cance.

Results
Main characteristics of demographic and operative data were summarized in Table 1. The included 37 patients were followed up for a mean of 26 months (rang 20-46). In the study, the mean interval between injury and surgery was 8 (rang 5-16) days. The mean operating time was 210 (rang 140-500) mins, and the mean blood loss was 840 ml (range: 400-2000). All surgical incisions healed by rst intention. No inguinal or abdominal wall hernias occurred. No vascular and nerve damage during the operation. Four patients developed a deep venous thrombosis (DVT) on the injured side. None of the patients developed pulmonary embolism. Avascular necrosis of femoral head and hip osteoarthritis was not observed. Heterotopic bone formation was observed in one patient. Three patients presented with temporary mechanical ileus postoperatively and recovered within 36 hours by enema treatment. The complications are presented in Table 2.    Table 2.

Discussion
As we all know, accurate reduction and internal xation of complex acetabular fractures are di cult because of its complicated anatomical structure and deep location. Therefore, it is necessary to perform good exposure of operative eld through a surgical approach to achieve anatomic reduction of acetabular fractures. In this study, we demonstrated that the Pararectus approach provided anatomical reduction and obtained good clinical outcomes with fewer complications in the treatment of complex acetabular fractures involving the anterior column and the quadrilateral plate. We thought that the Pararectus approach can be recommended as an alternative access to treat displaced complex acetabular fractures involving the anterior column.
The ilioinguinal approach was once regarded as the standard approach for the treatment of acetabular fractures involving the anterior column. But this approach did not allow a direct view of the quadrilateral plate and acetabular dome fracture fragments, which could result in a mal-reduction of the fracture. The modi ed Stoppa approach was introduced as a less invasive alternative to the ilioinguinal approach, but mostly combined with the outer window of the ilioinguinal approach [19]. Shazar et al. demonstrated that the modi ed Stoppa approach offered better exposure and improved reduction quality of acetabular fractures compared with the ilioinguinal approach [7]. Furthermore, the Pararectus approach has been introduced to treat acetabular fractures involving the anterior column and the quadrilateral plate [20], and was considered to combine the advantages of the ilioinguinal approach and the Stoppa approach [21].
It was important to obtain accurate reduction of the fracture which is possible, with a less invasive surgical approach, as both were related to improved functional outcome [2]. In this study, we demonstrated that acetabular fracture reduction was greatly improved using the Pararectus approach. In the presented study, the quality of reduction was classi ed as at least satisfactory in thirty patients (81%) and unsatisfactory in seven patients (19%). Our results are consistent with Ochs et al. who reported an overall rate of anatomical reduction of 64% with Pararectus approach [22]. Shazar et al. reported the treatment of 122 patients using the ilioinguinal approach, of whom eight (40%) had an anatomical reduction, and nine (45%) had a satisfactory and three (15%) a poor reduction [7]. Keel et al. reported a series of 20 patients, of whom 84 patients (68.9%) had an anatomical reduction [9]. Based on presented studies, the Pararectus approach achieved at least or higher reduction quality compared to other approaches [11]. The quality of reduction was related to the complexity of the fracture [17]. Patients with preoperative fracture comminution or postoperative unsatisfactory reduction usually had a poor functional outcome [23]. Jang et al. demonstrated that acetabulum dome impaction and wide residual gaps (>3 mm) were identi ed as risk factors for poor outcomes [24]. Therefore, orthopaedic surgeons should strive to achieve the anatomical reduction of the articular surface in the treatment of acetabular fractures. In this study, the mean "step" and "gap" were signi cantly decreased by fracture reduction from 4.9 mm and 9.5 mm preoperatively to 1.3 mm and 1.8 mm postoperatively, respectively. It was concluded that the Pararectus approach can achieve a satisfactory reduction rate.
At a follow-up of two years, functional outcome was excellent in 8 patients (22%), good in 19 patients (51%), and fair in 6 patients. The presented outcome obtained using the Pararectus approach was equal to that obtained the modi ed Stoppa approach for acetabular fracture management [25][26][27]. But the access morbidity in our study was low only in four patients with a DVT and one patient with heterotopic bone. Antithrombotic treatment was used for three months, and no cases of pulmonary embolism occurred. In the Pararectus approach, no dissection of the inguinal canal was performed, which reduced the risk of inguinal hernia postoperatively. There was no formation of an inguinal hernia postoperatively, which has been reported by the ilioinguinal approach [28]. Though the major complications in patients treated via the Pararectus approach are the peritoneum and obturator nerve injuries, no peritoneal perforations and obturator nerve injuries were observed in our study. No patients underwent total hip arthroplasty due to avascular necrosis of the femoral head and hip osteoarthritis. However, it should be noted that a long-term study to evaluate hip osteoarthritis is therefore necessary.
The advantage of Pararectus approach was that it created the ve windows with less invasive tissue dissection for direct exposure to the quadrilateral plate and acetabular dome, rare need for an additional incision [21]. It was not necessary to change any window during reduction and xation of fracture, and just mild traction of neurovascular structures was applied. Thus, this approach resulted in better quality of reduction and fewer complications. In comparison with the ilioinguinal approach, the Pararectus approach achieved better reductions quality and had no signi cant differences in complications [29]. Bastian et al. demonstrated that the Pararectus approach provided a nearly 13% increase in bone exposure and facilitated a greater surgical access in the inner pelvis compared to the modi ed Stoppa approach [30]. In the present study, we believed that the improved clinical outcome was largely related to the accurate reduction of fracture through the Pararectus approach, which improved direct visual control and access of the quadrilateral plate and acetabular dome.
This study has some limitations. The study was a retrospective design, and lacked a historical comparison group. It was an insu cient statistical power because of few reported cases and relatively short follow-up time. Although no comparison to other approaches, the presented data provide evidence that the Pararectus approach improved a higher anatomical reduction rate and obtained good clinical outcomes with fewer complications at the midterm. Figure 1 Diagram for the incision. The umbilicus, the symphysis, and the anterior superior iliac spine (ASIS) were marked. The red line represented the location of the surgical incision.

Figure 3
Preoperative and postoperative imaging evaluation. A, B Three-dimensional CT showed acetabular fractures involving both columns. C The coronal CT scan showed a dome impaction and a large "gap" of fragment preoperatively. D, E The sagittal and axial CT scan showed large "gap" and "step" of fragment preoperatively. F-H Postoperative CT scans showed the anatomical reduction and xation with reconstruction plates. I, J Postoperative obturator oblique and iliac oblique views.