Anterior intrapelvic approach and suprapectineal quadrilateral surface plate for acetabular fractures with anterior involvement: a retrospective study of 34 patients

Background The purpose of the study is to evaluate the use of the suprapectineal quadrilateral surface (QLS) plates associated with the anterior intrapelvic approach (AIP) to the acetabulum in the surgical treatment of acetabular fractures with anterior involvement. Methods We did a retrospective study of patients surgically treated with QLS plates and AIP for acetabular fractures with the involvement of the anterior column, between February 2018 and February 2020, in our Hospital. The following data were recorded: mechanism of injury, the pattern of fracture, presence of other associated injuries, the time before performing the surgery, surgical approach, position on operating table, time of surgery, intraoperative bleeding, hospitalization time, intraoperative and postoperative complications. Follow-ups were performed at 1, 3, 6, 12 months, then annually. The clinical-functional outcome was assessed with the Merle d’Aubigne Postel score (MAP) modified by Matta; while the radiological outcome with the Matta Radiological Scoring System (MRSS). A Chi-square test was utilized to examine associations between parametric variables. Results We included 34 patients, mean age 62.1, with an average follow-up of 20.7 months. The most frequent traumatic mechanism was road trauma. There were 15 isolated anterior columns and 19 associated patterns. There were 5 cases of associated visceral injuries, and 10 cases of other associated skeletal fractures. All patients were in the supine position. The surgical approach used was the AIP in all cases, with the addition of the first window of the ilioinguinal approach in 16 cases and of the Kocher-Langenbeck approach in 2 cases. The average time before performing the surgery was 8.5 days. The mean time of the surgery and the mean length of stay after surgery were 227.9 min and 8.2 days, respectively. There weren’t cases of intra-operative complications, while there were postoperative complications in 5 patients. The MRSS was judged anatomical in 26 cases, imperfect in 7 cases and poor in 1 case. The average MAP value was 15.2. We observed a significant relationship between the radiological outcome and the clinical outcome (p < 0.05). Conclusions The QLS plates in association with the AIP approach represent an effective treatment strategy for the treatment of acetabular fractures with anterior involvement.


Background
Acetabulum fractures are uncommon fractures, about 5-8 per 100,000 person-years, that have always been a challenge for orthopedic surgeons.In recent decades there has been a rise in their incidence, especially in the elderly population, after a low energy trauma [1].
Acetabular fractures in the elderly usually present involvement of the anterior column of the acetabulum [2,3].
For the specific treatment of this fracture pattern of the acetabulum was introduced new hardware, the suprapectineal quadrilateral surface (QLS) plate, which is mainly used to fix fractures of the anterior column of the acetabulum with the involvement of the quadrilateral lamina.Extensions of indications are represented by fractures of the anterior column with posterior hemitransverse, T-type fractures, and fractures of both columns, which may require additional fixation of the posterior column with axial screws or Culemann screws [4][5][6].
The anterior intrapelvic approach to the acetabulum (AIP) has emerged, in the last two decades, as a promising approach for fixation of anterior acetabular fractures.The AIP approach is less invasive, with less bleeding and postoperative complications than the traditional approach, while guaranteeing good exposure of acetabular fractures with involvement of the anterior column [7,8].The purpose of this study is to evaluate the use of the suprapectineal QLS plates associated with the AIP approach in the surgical treatment of a series of 34 cases with acetabular fractures with predominantly anterior involvement.
Our prespecified hypothesis is that this hardware is secure and ensures stable fixation in this specific type of acetabular fracture and that the AIP approach is well tolerated by the elderly and does not present particular complications.

Methods
We did a retrospective cohort study of all pelvic fractures surgically treated in the Department of Orthopaedics of our level II Trauma Centre, between February 2018 and February 2020, in the period preceding the Covid-19 pandemic which altered the normal working activity of our Hospital [9,10].
For the current study, we included only isolated anterior column fractures and associated patterns involving the anterior column according to Judet and Letournel classification, over 18 years of age, treated with open reduction and internal fixation using the AIP approach and suprapectineal QLS plate (PRO -Pelvis and Acetabulum System, Stryker, Kalamazoo, MI, USA) with a follow-up more than 1 year.Exclusion criteria were open fractures of the acetabulum, pathological fractures and fractures presenting after 1 month of injury [11].
All patients were examined before surgery with anteroposterior pelvis X-ray view, Judet X-ray views (obturator oblique view and iliac oblique view), and thin-slice CT with multi-planar reconstructions [12].
The following peri-operative data were taken into consideration: mechanism of injury, the pattern of fracture according to the Judet and Letournel classification, presence of other associated visceral injuries or skeletal fractures, the time before performing the surgery, surgical approach, the position adopted by the patient on the operating table, time of surgery, hospitalization time, intraoperative and postoperative complications.The surgery objectives were to obtain the anatomical reduction of the fractures and to obtain a stable and strong fixation.The radiolucent carbon table was used to allow intraoperative radiological visualization without interference.
The AIP approach is a minimally invasive intrapelvic and extraperitoneal approach that can expose the anterior column, the pelvic brim, the quadrilateral lamina and the medial portion of the posterior column.The AIP approach does not require dissection of the inguinal ligament, unlike the second window of the ilioinguinal approach described by Letournel and is particularly useful when a Cooper ligament repair has been performed or when the mesh was applied for a previous inguinal hernioplasty [7,8].
The QLS plate is indicated in fractures where the anterior column is disrupted and the quadrilateral surface is comminuted and disassociated from the posterior column.It provides the simultaneous fixation of both columns [11].
Postoperative clinical and radiographic examinations were performed at 1, 3, 6, 12 months, and then annually.The quality of surgical reduction was assessed in anteroposterior pelvis X-ray view and Judet X-ray views by measuring the residual postoperative displacement and according to the radiographic criteria by the Matta Radiological Scoring System (MRSS) they were classified as anatomical, imperfect, or poor.According to the postoperative displacement measured on X-rays, the quality of the reduction can be evaluated anatomical (0-2 mm), imperfect (2-3 mm), or poor (> 3 mm) [13].
At the last follow-up, the clinical-functional evaluation was performed with the Merle d' Aubigne and Postel (MAP) score modified by Matta to precisely explore the patients' pain, gait and mobility [14][15][16].
A Chi-square test was utilized to examine associations between parametric variables.We have analyzed the relationship between clinical outcome score (MAP) and radiological outcome (MRSS); and the relationship between the clinical outcome score (MAP) and the type of fracture according to Judet and Letournel classification.P-values < 0.05 were considered statistically significant.
All procedures performed in the current study were following the 1964 Helsinki declaration and its later amendments.Informed consent was obtained from all individual participants included in the study.The study design was approved by the Institute and School Council.

Results
A total of 34 patients, 26 men and 8 women, were included in the study.The average age is 62.1 years (range 27-87 years).The mean follow-up was 20.7 months (range 12-36 months).Four of 34 (11.8%)patients were followed up at 3 years, 13 (38.2%)were followed up at 2 years, the remaining 17 (50%) at almost 1 year.
The traumatic mechanism was in most cases a road trauma (20 cases -58.8%), followed by accidental fall (9 cases -26.5%), and fall from height (5 cases -14.7%).The 20 road injuries were specifically caused by accidents involving cars in 11 cases, motorcycles in 6 cases and bicycles in 3 cases.Accidental falls in all cases concerned elderly people (age over 65) while height drop (falls from a height greater than 1.5 m) occurred in the workplace.
All patients were operated on the supine position.The surgical approach used was the AIP approach in all cases.In 16 cases (47%) is also used the first window of the ilioinguinal approach, to place axial screws in the posterior column of the acetabulum.In 2 cases (5.9%) a second-time surgery in the prone position was required, in the same surgical procedure, using the Kocher-Langenbeck approach to reduce and fix the posterior column of the acetabulum, because it was not possible to achieve with an anterior approach.(Fig. 1).
The average time before performing the surgery was 8.5 days (range 3-20 days).The mean time of the surgery and the mean length of stay after surgery were 227.9 min (range 184-358 min) and 8.2 days (range 4-17), respectively.There have been no cases of intra-operative complications.(Table 2).
We observed postoperative complications in 5 patients (14.7%): one case of deep infection required surgical removal of the hardware; one case of intra-articular penetration of a screw from the anterior column requiring screw removal and 3 cases of deep venous thrombosis (1 posterior tibial vein, 1 superficial femoral vein, and 1 femoral vein) treated with low molecular weight heparin.
At the one-year radiographic follow-up, delayed union or malunion were not recorded.
We observed a significant relationship between the clinical outcome and the radiological outcome (p < 0.05), while we did not observe significant relationships between the clinical outcome and the type of fracture (p > 0.05).

Discussion
Fractures of the pelvis are uncommon fractures, with bimodal distribution in the population, caused by highenergy trauma in the young, like motor vehicle collision, and by low-energy trauma in the elderly, as falling on the same level.In recent decades there has been a rise in the incidence of these fractures, thanks to the increase in the survival rates of the most critical patients and to the improvement of emergency care [1,2].
The treatment of acetabulum fractures needs an open approach for anatomical reduction and fixation of the fragment, also in the elderly [13,14,[17][18][19].
In older age there is an increase of specific patterns of fracture involving the anterior acetabular structures: anterior column, quadrilateral lamina fracture, medial dislocation of the femoral head, and roof impaction (with the specific Gull sign), differ from those in younger patients [20,21].
The anterior column is formed from a combination of the ilium and pubic bones.Anterior column fracture is an elementary fracture according to the Judet and Letournel classification that could be isolated or involved in an associated pattern of fractures with posterior hemitransverse, T-type, and both columns, that require a specific fixation technique [22].
A traditional fixation method of these fractures uses lag screws over a suprapectineal plate through the ilioinguinal approach described by Letournel.In addition, an infrapectineal plate could be used to provide a buttress effect against the protrusion of the femur into the pelvis.The combination of a standard pelvic brim plate with lag screws and an infrapectineal plate supporting the quadrilateral lamina resulted in a better fixation construct and provide better stability with the advantages in the prevention of construct failure in situations in which significant lateral to medial force is applied, such as patient falls on homolateral hip [23][24][25][26].
In recent years, new alternative hardware has been introduced for the treatment of anterior acetabular fractures, the suprapectineal QLS plate, which is an anatomic preshaped plate, that represents a valid alternative to the infrapectineal plates, providing a better dynamic buttress effect to the comminuted fragments of the quadrilateral lamina, and preventing the medial subluxation of the femoral head.This hardware allows the simultaneous fixation of the anterior column, with the suprapectinal portion of the plate, and the quadrilateral lamina, with the infrapectineal portion; so are useful in the treatment of different fracture patterns: anterior column, anterior column with posterior hemitransverse, T-type and both columns.They have been specifically designed to prevent secondary medial subluxation of the femoral head, especially in elderly patients with reduced partial load capacity; moreover, screws placed in the quadrilateral lamina extension were not in danger for intraarticular placement as demonstrated in CT scans [4,27,28].
In the literature is reported a great variability of osteosynthesis for the treatment of fractures of the anterior column of the acetabulum with the involvement of the quadrilateral surface, without consensus in the choices.
Boni G et al. use a suprapectineal plate with the addition of a stainless-steel locking calcaneal plate, through the modified Stoppa approach, to fix quadrilateral lamina; while Farid YR et al. proposed a cerclage wire-plate composite fixation with an extraosseous cerclage and a reconstruction plate over the pelvic brim [29,30].
Another possible treatment uses a 3.5 mm or 4.5 mm reconstruction plate on the pelvic brim partially protruding medially into the true pelvis and in addiction one or more buttress screws inserted through the plate holes, on the outside surface of the quadrilateral surface close to the edge of the pelvic brim [31].
Kulkarni et al. described the treatment of comminuted quadrilateral plate fractures of the acetabulum using a modified Stoppa approach and a spring buttressing plate with good scores in clinical and radiological outcome at 1 year follow up [32].
In our experience, the AIP approach is associated with the suprapectineal QLS plates.In some cases, if the fracture of the anterior column is high or very displaced can be combined with the first window, the lateral one, of the ilioinguinal approach described by Letournel [4,5,33].
In our series, we were able to achieve an anatomical reduction with a postoperative displacement < 1 mm in 26 of 34 cases.
Our clinical and radiographic results are comparable to those obtained by other authors.Archdeacon et al., using a combination of suprapectineal and infrapectineal plates, found an average MAP score of 16 and an excellent MRSS in 15, good in 3, poor in 3; while Tosounidis et al., using a quadrilateral plate reconstruction with a buttress plate through the ilioinguinal approach obtain in 30 patients an MRSS excellent in 11, good in 9, fair in 5 and poor in 5; while the overall Fig. 1 A case of a patient with both columns fracture pattern according to the Judet and Letournel classification of the right acetabulum.It was pre-operative examined with anteroposterior pelvis X-ray view and Judet X-ray views (obturator oblique view and iliac oblique view) (A), and thin-slice CT with 3D reconstructions (B).One-year radiographic follow-up with anteroposterior pelvis X-ray view and Judet X-ray views (C).Internal fixation was performed using the AIP approach and the QLS suprapectineal plate.Also, were used a percutaneous screw inserted with the cannulae of the pelvis pro system and an LC2 screw in the supraacetabular corridor functional score was excellent in 17, good in 4, fair in 6 and poor in 3 cases [23,26].
This shows that the QLS plate in combination with the AIP approach makes it possible to obtain a valid endopelvic exposure of the fracture that allows for a good reduction and consequently a stable fixation.
At the last clinical follow-up examination, all patients reported a good functional restore with no or mild pain and no or slight hip stiffness not particularly affecting their quality of life, but those with an anatomical reduction had an excellent clinical outcome.
The AIP approach utilizing the anatomical-preshaped suprapectineal plate allows anatomic or at least imperfect fracture reduction, according to Matta's radiological criteria, in 97% of cases of our study.
In our experience, the plates have shown an excellent anti-protrusion effect of the femoral head and quadrilateral lamina, without a record of delayed union or malunion.This procedure with the combination of a specific anesthesiology technique as the supra-inguinal fascia iliaca compartment block has become the standard procedure in our departments for the fracture of the acetabulum that involves the anterior column [34].
The strength of our study is that to our knowledge there is no case series in the literature of patients treated with the combined use of the AIP approach and QLS plate.
Limitations of the study are the small number of cases, different follow-up times, lack of a case-control treatment with an alternative fixation method and short-term follow-up.

Conclusions
From the literature analyzed and with our experience, it is possible to confirm that the suprapectineal QLS plates represent an effective and safe system of fixation for the treatment of acetabulum fractures involving the anterior column.The AIP approach to the acetabulum is demonstrated to be a safe, effective, and feasible alternative to the traditional ilioinguinal approach for acetabulum fractures which require an anterior approach.• fast, convenient online submission • thorough peer review by experienced researchers in your field • rapid publication on acceptance • support for research data, including large and complex data types • gold Open Access which fosters wider collaboration and increased citations maximum visibility for your research: over 100M website views per year

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Table 1
Patient demographics and injury characteristics

Table 2
Surgery characteristicsAIP Anterior intrapelvic approach to the acetabulum

Table 3
Patient post-operative complications, outcomes and follow-up MAP Merle d'Aubigne and Postel score, MRSS Matta Radiological Scoring System