Modified Stoppa as an alternative surgical approach for fixation of anterior fracture acetabulum: a randomized control clinical trial

Background Fracture acetabulum is a challenging, difficult to treat orthopedic injury due to its location and associated concomitant injuries. The modified Stoppa approach for reduction of fracture acetabulum improves access to quadrilateral surface and posterior column and is considered to be advantageous in many facets of the surgery. Methods A randomized controlled clinical study was conducted to provide an update on our experience with modified Stoppa as a favorable surgical approach in acetabular fractures. In the period between 2015 and 2017; 18 patients with acetabular fractures operated by the classical ilioinguinal approach were retrospectively reviewed through their medical records as a controlled group and selected 20 patients with acetabular fractures were operated in the period between 2017 and 2019 using the modified Stoppa approach, as a clinical case group. The two groups were compared regarding operative data and postoperative clinical data, complications, and follow up. Cases were operated in Al Zahraa University Hospital and Nasr City Insurance Hospital by the same surgeon and one of the co-authors. Results (Group A) those operated by ilioinguinal approach and (Group B) those operated using Stoppa approach. The whole study included 25 males (66%); mean age was 41.8 ± 8.42 (range 18-65) years. The mean follow-up period was 18.5 months with 5 patients lost to follow-up. Both column fractures were observed in most of the patients (45%). We observed anatomical reduction, excellent clinical outcome scores in 75% of patients of group B (p = 0.030), and less complications. Conclusion Our findings indicated that the modified Stoppa approach is the most convenient approach when surgery is required and achieved favorable results in the treatment of anterior acetabular fractures because it improves visualization in lateral compression injuries and allows treatment of both column fractures with single incision. Hence, it is recommended as an alternative to ilioinguinal approach in developing countries. Further, larger-scale comparative studies of the two surgical modalities for different acetabular fracture types and long-term complications are recommended. Trial registration A retrospective registration is proceeding through Clinicaltrials.gov. Level of evidence Level III, therapeutic clinical study


Introduction
Acetabular fracture is a serious orthopedic injury that is managed using anterior, posterior, extensile, and combined surgical approaches. The correct surgical approach is crucial for accurate reduction. Ilioinguinal approach and the modified Stoppa approach are commonly used anterior approaches. Initially, Rives et al. and Stoppa et al. employed the modified Stoppa approach in inguinal hernia surgery. Cole and Bolhofner and Hirvensalo et al. described it as a method to approach the anterior acetabulum and pelvic bone [1][2][3][4].
Modified Stoppa approach has been evaluated in many studies that reported similar clinical outcomes as the ilioinguinal approach [5][6][7][8][9][10]. It is advantageous in treating acetabular fractures with anterior column involvement and even considered a superior alternative to ilioinguinal approach [1][2][3]. The modified Stoppa approach has recently become popular in Europe as it is less invasive and provides better visualization to quadrilateral plate and the posterior column [1][2][3]5]. It allows direct (medial) buttressing of fractures with associated central protrusion of the femoral head.
There is extensive evidence available on early radiographic results, but long-term follow-up data is not sufficient [2,[5][6][7]. In this study, we evaluated operative technique of Stoppa approach, its clinical outcomes and complications compared to the classical ilioinguinal approach with respect to comminution of fractures. A total of 88 patients with acetabular fractures attended trauma section at Al Zahraa University Hospital and Nasr City Insurance Hospital in Cairo since June 2015 until end of May 2019; 30 of them whose operated using ilioinguinal approach in the period of June 2015 until July 2017 and fit inclusion criteria underwent retrospective review of their medical records by one of the co-authors considering technique, time of operation, and blood loss. Postoperative follow up of complications was assessed through contacting those patients but only 18 patients could be reached were included in our study as a GROUP A (12 males, 6 females). While twelve patients excluded from the study as ineligible and 5 with pathological fracture, 3 patients refused operation, 7 unfit for anesthesia due to cardiac problems, 6 died from internal hemorrhage, and 5 refused to sign consent. Only 20 patients included as a GROUP B, 13 males (65%) and 7 females (35%) (Fig. 1), with acetabular fractures between 2017 and 2019 were considered in the study. Their mean age was 36.8 ± 8.42 (20-73) years (Table 1). The patients underwent open reduction and internal fixation by reconstruction plate using modified Stoppa approach operated by the same co-author at Al Zahraa University Hospital and Nasr City Insurance Hospital in Cairo. The mean follow-up period was 18.5 months with 5 patients lost to follow-up. In most of the patients, both column fractures (45%) were observed. The two groups: (Group A) 18 patients with acetabular fracture treated with ilioinguinal approach as per reviewed medical records and (Group B) 20 patients with modified Stoppa approach with their operative data. The American Society of Anesthesiologists (ASA) physical status classification (ASAPS) for both the groups and operative variables are illustrated in Tables 2 and 3.

Mode of trauma
In the study groups, 9 patients in group B had motor car accidents (MCA) and 7 in group A, 4 patients had motor bike accidents (MBA) in group B and 5 in group A, 3 had road traffic accidents (RTA) in group B, while 1 only in group A, 2 patients had fall to the ground (FTG), and 2 fell from a height (FFH) in group B in contrast to 6 patients FFH in group A (Fig. 2).

Statistical analysis
Results are expressed as mean ± standard deviation or number (%). Comparison between values of different parameters in the studied groups was performed using Kruskal Wallis test followed by Mann-Whitney test as a post hoc test if significant results are recorded. Comparison between categorical data was performed using chi-square test. SPSS (Statistical Package for the Social Science; SPSS Inc., Chicago, IL, USA) (version 16 windows) was used for data analysis. P value less than or equal to 0.05 was considered significant and less than 0.01 was considered highly significant.

Operative data analysis
Operative variables among the two groups are illustrated in Table 3 which concludes that shorter operative time (duration of surgery), less blood loss, and blood transfusion needed were significantly noticed in group B   In order to access posterior column, the classic descriptive approach was used alone in 56% of cases with all types of fractures and exclusive with cases of anterior fracture type (Table 2).

Postoperative mobilization protocol for both groups
As soon as drain removed, in-bed passive hip movement exercises started to begin. Patients were then encouraged to engage in touch-down weight-bearing mobilization as early as possible for the operative side by taking into account each patient's general condition and concomitant injuries. Until the 8th week postoperatively, touch-down weight bearing was permitted and continued with partial weight bearing with two crutches and then one crutch until full weight bearing was achieved at the 12-16th week by considering each patient's radiological findings.
Patients with severe comminution of the acetabulum were subjected to skeletal traction for 2-3 weeks. Those patients who had bilateral acetabular fractures were advised to get engaged with in-bed and bedside exercises, passive hip movement exercises, and hip strengthening exercises with no weight-bearing until week 6-8 postoperatively. Mobilization was then continued with partial weight-bearing after considering each patient's radiological findings as follows: Static quadriceps exercises and ankle dorsiflexion exercises were started within 24 h after the surgery. Passive and active knee exercises while in recumbent position commenced from day 2 postoperative. Once the pain had subsided, the patient started gait training on a walker or axillary crutches. Without weight bearing on the affected side. Active flexion, extension, and abduction exercises while standing were encouraged. Physical therapy was directed towards regaining muscle strength around the hip and range of motion. Limitation of weight bearing was continued for 8-12 weeks postoperatively. 12 weeks: Full weight bearing ambulation was permitted only after fracture healing, evident by clinical and radiological union. This was usually achieved by about 12 weeks. Patient was then advised to gradually discard walking aids as tolerated and assessed in postoperative visits (Table 4).

Postoperative outcome results
Quality of reduction was estimated on anteroposterior (AP) pelvis and Judet views that taken immediately after surgery evaluated by Matta criteria; comparisons between the two groups are illustrated in Table 5 noticed that the quality of reduction is excellent with 75% of patients in group B treated with modified Stoppa approach (p = 0.03). Excellent clinical outcome was observed in 8 patients of group A, versus 11 patients of group B. Good in 4 patients of group A, versus 7 patients of group B, and poor clinical outcome in 6 patients of group A, versus 2 patients of group B (p = 0.05) (Fig. 4). Incidence of late postoperative residual subluxation of the femoral head was 55% in patients of group A, which was significantly low (30%) in patients of group B those treated with modified Stoppa ( Table 6). The mean modified Merle D'Aubinge and Postel score in both groups according to fracture types showed an excellent clinical results in patients of modified Stoppa approach especially with anterior column fracture type compared to patients underwent ilioinguinal approach for the same fracture type (Table 7). Lastly, postoperative complications were compared in the two groups emphasized that modified Stoppa approach is associated with significantly less incidence of complications that made it; the approach of choice when surgery is required ( Discussion Acetabular fractures are difficult to treat due to the difficulties associated with the surgical approach, associated  In the patient group of our study, the number of male patients was higher than female patients. Similar to our study, 16 studies on 609 patients to evaluate the Stoppa approach revealed that the male-female ratio was available for 566 patients, which was same as our study [5,[11][12][13][14][15][16][17][18][19][20][21][22][23]. Data for the remaining patients were unavailable due to various reasons. But the common fact in all these studies was the number of male patients was higher than that of female patients. The range of age in the 11 studies we cited was 10-88 years [5, 11-15, 17, 21-24] [11,[16][17][18][19][20]. The mean age in our study was much lower (36.8 ± 8.42 (range 20-73) years) compared to these observations. The difference could be mainly because our study had a smaller age range.

Delay in surgery
Time delay for surgery ranged from 0 day to 30 days in 8 studies [5,[11][12][13][14][15][16][17][18][19][20][21][22][23]. In comparison, Dailey et al. reported a mean time of 4.83 ± 3.74 from injury to surgery [20]. There were many reasons affecting the preoperative time  in our study. The most important was the time between the actual trauma and the date at which the patient presented to our hospital. Five patients included in this study presented to us after 4-7 days of trauma. Another factor was the availability of blood units for intraoperative transfusion. Three patients were of blood group Band two patients were of blood group AB-; this caused significant delay in the operative date. Another factor worth mentioning is the waiting list for the operative theater.

Surgical time
In the 7 studies we cited, the surgical time ranged from 80 min to 568 min [5, 11-15, 17, 21-24]. Anderson et al. reported the surgical time from 3 h to 8 h 48 min, including the time until the physician reviews the after-surgery radiographs [5]. The mean operative time for our study in group A was 211.14 ± 25.0 min, which was longer compared to group B was 116.15 ± 21.6 min. Estimated blood loss reported in the 9 studies ranged from 100-5000 ml [5, 11-15, 17, 21-24]. Our results were also in agreement with these observations. In addition, the blood loss (856.5 ± 194.2) and need for intraoperative transfusion (100%) in group A, while less in group B (335 ± 115.4) ( Table 3).
Sagi et al. observed that the patients associated with both column fractures show poor fracture reduction (75%) [6]. Patients with anterior column fracture achieved the highest percentage of excellent reduction (92%), whereas patients with transverse fractures had the lowest percentage (67%). Results of Shazar et al. were also similar; except for the patients with anterior column with posterior hemitransverse fractures achieved the highest reduction (92.9%) of anatomical reduction was achieved in anterior column with posterior hemitransverse fractures [16].

Complications
The most frequent early complication from initial trauma reported is obturator nerve injury and the late complication from initial trauma is hip joint arthritis. Soni et al. reported an improvement in certain acetabular fractures and also concluded that the Stoppa approach may have lower rate of complications compared to extrapelvic extensile approaches. In comparison, Kima et al. estimated that the modified Stoppa approach is associated with 9% rate of obturator nerve injury from initial trauma [24]. The modified Stoppa approach may be helpful in releasing obturator nerve and consequently in obturator nerve injury (Table 8).
Therefore, the modified Stoppa approach is strongly recommended in patients with two-column acetabular fractures in the case of preoperative detection of obturator nerve injury.

Access to quadrilateral plate
In this study, we used the modified Stoppa approach along with lateral window. Soni et al. recommended using modified Stoppa approach as a substitute to total hip arthroplasty to support the quadrilateral plate in patients with fracture acetabulum involving anterior column and quadrilateral surface.

Access to posterior column
Modified Stoppa approach with lateral window of ilioinguinal enhances reduction and fixation of posterior column and quadrilateral surface with a better access. This approach is also helpful in the fixation of anterior column fracture extending into posterior column 8, 9, 12. Isaacson et al. reported a good functional outcome in 36 patients with acetabular fractures extending to posterior column after treating them with this approach; they also reported a lower rate of complications [6]. Additionally, the anterior approach alone has been reported to be difficult for the treatment but is a feasible option.

Variations of the approach
The modified Stoppa approach is either combined with other approaches or modified in the practice [9,13,15]. Rocca et al. combined it with proximal and lateral window of ilioinguinal approach (anterior combined endopelvic; ACE) [8]. The Stoppa approach was modified by Sagi et al. as anterior intrapelvic (AIP) approach. The Stoppa approach has resulted in a reduction in fractures along with comparable complication rates [6].

Comparison with ilioinguinal approach
Outcomes of Stoppa approach have been compared in five studies with ilioinguinal approach with respect to fixing the fracture acetabulum [13,[17][18][19]21]. Rocca et al. compared ACE approach (34 patients) with ilioinguinal approach (42 patients) to treat acetabular fracture [9]. They reported better clinical outcomes with ACE approach compared to the ilioinguinal approach. They also reported a lower complication rate with the ACE approach. In contrast, Hammad AS et al. reported a similar reduction in fracture and similar clinical scores with ACE and ilioinguinal approach [19]. Stoppa approach provides direct buttressing of quadrilateral surface and associated both column fractures. But associating the Stoppa approach with middle window of ilioinguinal approach improves access to anterior wall and transversely oriented fractures.
In the contrast, Elmadag et al. reported that the Stoppa approach does not provide any improvement in associated complication rates and bleeding compared to the ilioinguinal approach but has a cosmetically better scar [11]. Ma et al. also reported similar results but better operative time, wound drainage, and lesser blood loss, suggesting lesser blood transfusion with Stoppa approach [17].
Stoppa approach improves visualization in lateral compression injuries and allows treatment of bilateral fractures with single incision. Additionally, Shazar et al. reported a higher rate of anatomical reduction in lesser surgical time and comparable complication rate with Stoppa approach compared to ilioinguinal approach [16]. Soni et al. concluded that modified Stoppa approach is a better option for treating fracture acetabulum [23]. A lateral window without exposing the neurovascular bundle to treat the fractures extending to the iliac crest is another advantage of the Stoppa approach.
Finally, this study has limitations such as having limited number of patients over long study period, and short term follow-up.