Preliminary Clinical Study on the Treatment of Acetabular Quadrilateral Fractures With a Novel Anatomical Locking Plate

Eleven patients treated with AQALP in the First Affiliated Hospital of Chongqing Medical University, between December 2017 and June 2020, with acetabular fractures involving the quadrilateral plate, were prospectively recruited and regarded as an observation group. According to the fracture types clarified by the Judet-Letournel classification, a retrospective 1:1 matched-pair analysis was performed, and 11 acetabular fractures involving the quadrilateral plate treated with reconstruction plates were recruited and regarded as the control group, and each group included 3 anterior column fractures, 3 transverse fractures, 4 both column fractures, and 1 T-type fracture.

The following were the inclusion criteria: age ≥18; diagnosed with acetabular fracture involving the quadrilateral plate; treated with AQALP or reconstruction plates; and a fresh fracture.

Exclusion criteria included the following: age <18; patients with osteoarthritis or necrosis of the femoral head; pathological fractures; old fractures; dysfunction of the hip joint or lower limbs before the injury; and dysfunction of lower extremities caused by severe spinal cord or craniocerebral damage at the time of injury.

Ethical clearance was obtained from the Ethical Committee of First Affiliated Hospital of Chongqing Medical University (Number: 2020–278), and all procedures performed in this study were in accordance with the 1964 Helsinki Declaration.

The demographic data, time between injury and definitive surgery, surgical approaches, operation time, intraoperative blood loss volume, intraoperative blood transfusion volume, postoperative blood transfusion volume, fracture union time, reduction loss, and postoperative complications were recorded. The fracture reduction quality and hip function were respectively evaluated by Matta’s grading system and the modified Merle D’Aubigne-Postel grading system. The comparison was made to observe whether the 2 groups had differences in the preceding clinical parameters.

The novel acetabular anatomical quadrilateral locking plate is an integrated plate and consists of 1 central part, 1 extended anterior wall part, and 2 inner pelvis lateral wings (Fig. 1), of which the shape matches the upper margin of the true pelvis, acetabular anterior wall, and quadrilateral plate. The central part goes along the pelvic rim from the sacroiliac joint to the ipsilateral pubic tubercle, and the extended part covers the anterior wall of the acetabulum; meanwhile, the 2 lateral wings go down into the pelvic cavity to buttress the quadrilateral plate. Screw holes on the extended part are 2.7-mm locking holes, whereas those are 3.5-mm oval holes on the central part and lateral wings.

The demographic data, the time between injury and definitive surgery, as well as mechanisms of injury, are shown in Table 1. Under stable hemodynamics, according to weight, all patients received routine subcutaneous injections of low molecular weight heparin (LMWH) before the operation for the prevention of deep venous thrombosis (DVT). After admission, the complications were actively treated, and then surgery was performed under stable conditions. Both groups were treated with general anesthesia by endotracheal intubation. According to the type of acetabular fracture, a single anterior approach including the modified Stoppa approach, pararectus approach or ilioinguinal approach, or any of the previously mentioned anterior approaches combined with the posterior Kocher-Langenbeck approach was carried out. Patients took a supine position when choosing a single anterior approach or a “floating” position when choosing a combined approach. The performed approaches are shown in Table 2.

According to the preoperative plan, a corresponding approach was performed. Fracture reduction was obtained in a routine method by using Matta clamps, ball spike pusher, Schantz pin, and Farabeauf clamps. For the observation group, the anterior or posterior wing of AQALP could be trimmed partially or totally based on the fracture line location of the quadrilateral plate, then AQALP was inserted from the pubic tubercle and went along the pelvic rim. During the operation, the anatomical morphology of AQALP was used for further reduction of the fracture. The anterior column of the acetabulum was fixed by screws inserted at the superior ramus of the pubis and true pelvic rim. One or 2 screws were inserted at the posterior wing of the AQALP to fix the posterior column and buttress the quadrilateral plate. The reconstruction plates were used to fix the fractures of the iliac wing or posterior wall of the acetabulum. For the control group, the fractures of the iliac wing or posterior wall were fixed in the same way. A 10- to 14-hole pre-bent reconstruction plate was applied to fix the anterior wall and anterior column, of which the anterior part was fixed at the pubic tubercle and superior ramus of the pubis; meanwhile, the posterior part was fixed at the ilium. Then a screw was inserted at the true pelvic rim through the reconstruction plate to fix the quadrilateral plate of which the fracture fragment was not comminuted and without obvious displacement. Otherwise, a reconstruction plate pre-bent to an “L” shape was inserted to fix the quadrilateral plate, of which the proximal was fixed at the ilium, and the distal part buttressed the quadrilateral plate in the pelvis. Meanwhile, an iliopectineal reconstruction plate was applied to strengthen the fixation.

The LMWH or rivaroxaban was routinely given for 3 weeks under stable hemodynamics. The analgesic strategy was adjusted according to the pain degree assessed by the visual analogue scale. The prophylactic antibiotic was applied after surgery, and the duration depended on the operation time. Generally, if the operation time was no more than 3 hours, the antibiotic was used for 24 hours; If the operation time was more than 3 hours, the antibiotic would be used for 3 days. Functional muscle contraction training began as early as 24 hours after surgery, and the continuous passive motion（CPM）exercise was performed from the first postoperative day. Patients were allowed to partially weight-bear after 4 to 6 weeks with the support of axillary crutches, and to fully weight-bear after 12 to 16 weeks.

Within 1 week after the operation, X-ray and computed tomography (CT) examinations of the pelvis were performed to evaluate the fracture reduction quality and the position of internal fixation. The fracture reduction quality was judged according to Matta standards⁸ : fracture displacement not exceeding 1 mm was an anatomic reduction, 1∼3 mm was an imperfect reduction, and exceeding 3 mm was a poor reduction. The percentage of the sum of anatomic reduction and imperfect reduction in the total number of patients was the satisfactory rate of fracture reduction. The patients were told to follow up at 6 weeks, 3 months, 6 months, 9 months, and 12 months after the operation to observe the wound healing, evaluate the function of the hip joint, and check the nerve injury. In addition, an X-ray was performed to identify the fracture healing, loss of fracture reduction, heterotopic ossification, osteonecrosis of the femoral head, traumatic arthritis, and so forth. At the same time, a vascular ultrasound examination was carried out to observe the occurrence of lower limb DVT. At the last follow-up, the heterotopic ossification was evaluated according to the Brooker classification⁹  (Table 3). The hip pain, range of motion, and walking ability were evaluated according to the modified Merle D’Aubigne-Postel score system¹⁰  (Table 4). According to the sum of the 3 scores, the hip function was rated as follows: 18 as excellent, 15∼17 as good, 13∼14 as fair, and <13 as poor. The hip function score was recorded at 12 months of follow-up, and if the follow-up time was less than 12 months, the hip function score at the last follow-up was recorded. The percentage of the total number of patients rated as excellent and good was the satisfactory rate of hip joint function.

All analyses were performed using SPSS software 26.0 (SPSS Inc., Chicago, Illinois). The metrological data of the 2 groups were expressed by mean ± standard deviation (x ± s), and the Shapiro-Wilk test was used to determine whether the data obeyed a normal distribution. If the normal distribution was satisfied, a paired t test was used for comparison; if the normal distribution was not satisfied, a rank sum test was used for comparison. The χ² test was used for the comparison of the composition ratio. The threshold for statistical significance was set at a P value less than 0.05.

In this study, 11 cases of acetabular fractures involving the quadrilateral plate were enrolled in each group, including 1 anterior column fracture, 1 transverse fracture with posterior wall, 1 T-shape fracture, 2 transverse fractures, 2 anterior column fractures with anterior wall fracture, and 4 double-column fractures. All the patients in the 2 groups were followed up. Among these patients, 2 patients in the observation group and 1 patient in the control group were followed up by telephone for a long time after the operation, and the rest of the patients were followed up in the outpatient clinic. As for the observation group, the mean operation time was 327.82 ± 137.46 min (range: 120～580 min; median: 323 min), the mean intraoperative blood loss volume was 1745.46 ± 2103.98 mL (range: 300～7000 mL; median: 1000 mL), and the mean intraoperative blood transfusion volume was 1526.18 ± 1617.46 mL (range: 0～5130 mL; median: 900 mL), and the mean postoperative blood transfusion volume was 254.55 ± 439.01 mL（range：0～1400 mL; median：0 mL). The postoperative follow-up period ranged from 9 to 28 months, with an average of 15.09 months. As for the control group, the mean operation time was 273.18 ± 99.15 min (range: 120～450 min; median: 270 min), the mean intraoperative blood loss volume was 1122.73 ± 469.77 mL (range: 300～1500 mL; median: 1500 mL), and the mean intraoperative blood transfusion volume was 608.55 ± 363.71 mL (range: 0～1086 mL; median: 758 mL), the mean postoperative blood transfusion volume was 281.82 ± 430.86 mL（range：0～1000 mL; median：0 mL). The postoperative follow-up period ranged from 9 months to 42 months, with an average of 15.36 months. The fractures of both groups healed after the operation. The fracture healing time of the observed group was 2∼4 months, with an average of 2.91 ± 0.54 months, and that for the control group was 2∼5 months, with an average of 3.09 ± 0.70 months. There was a significant difference in operation time between the 2 groups, and the operation time of the observation group was slightly longer than that of the control group. There was no significant difference in intraoperative blood loss, intraoperative blood transfusion, postoperative blood transfusion, and fracture healing time between the 2 groups (Table 5).

The overall reduction of the acetabular fracture in the observation group was anatomic in 4 cases, imperfect in 6 cases, and poor in 1 case, therefore the satisfactory rate of fracture reduction was 90.91%; however, that in the control group was anatomic in 2 cases, imperfect in 6 cases, and poor in 3 cases, and the satisfactory rate was 72.73%. As for hip function, in the observation group, the function score was 12∼18 (mean score: 16.18 ± 2.14), excellent in 5 cases, good in 4 cases, fair in 1 case, and poor in 1 case, and the satisfactory rate of hip function was 81.82%; in the control group, the function score was 8∼18 (mean score: 14.64 ± 2.91), was excellent in 1 case, good in 7 cases, fair in 0 case, and poor in 3 cases, and the satisfactory rate of hip function was 72.73%. According to statistical analysis, there was no significant difference in satisfactory rate of fracture reduction, hip joint function score, and satisfactory rate of hip function between the 2 groups (Table 6). The typical case of the observation group is shown in Figure 2. The postoperative X-ray examination and CT scan showed a satisfactory reduction and a rigid fixation.

In the observation group, 1 case of lipoliquefaction of the surgical incision was recorded, after a series of measures including debridement, changing of dressing, and intravenous infusion of cefuroxime, the wound healed; 1 case with ectopic ossification and traumatic arthritis was observed, of which the hip function was poor, and the symptoms were relieved after using nonsteroidal drugs and doing functional exercise. In the control group, 2 cases of traumatic arthritis and 1 case of avascular necrosis of the femoral head were recorded. These 3 patients took celecoxib for a long time to relieve pain, and all of them chose conservative treatment during the follow-up period. Other postoperative complications such as DVT, loss of fracture reduction, or deep infection of the surgical site were not observed in either group.

Current studies have shown that the long-term effect of patients with acetabular fractures is closely related to the accuracy of fracture reduction.¹¹  In the past, the literature has reported the conservative treatment of acetabular fracture has some limitations, such as rapid joint degeneration and poor long-term function. For acetabular fractures with displacement greater than 2 mm, ORIF is still the first choice.¹²  The quadrilateral plat is an important part of the medial wall of the hip joint. When the acetabular fracture involves the quadrilateral plate, if the quadrilateral fracture could not obtain an anatomic reduction and rigid fixation, traumatic arthritis often occurs.⁴  However, the quadrilateral plate is located in the true pelvis, with thin bone and complex anatomy, therefore, the intraoperative exposure and reduction and fixation of the quadrilateral plate are challenging.

The position of the quadrilateral plate is deep, and it needs to be fully exposed during the operation to facilitate the anatomical reduction and stable fixation. The type of fracture, local soft tissue condition, age, the interval between injury and operation, and the operator's preference are the main factors that affect the choice of surgical approach for acetabular fracture.^13,14  The classic ilioinguinal approach, first proposed by Letournel et al,¹⁵  is still the most widely used approach at present, which can fully expose the ilium, acetabular anterior wall, and anterior column, and is suitable for anterior wall fractures, anterior column fractures, and transverse fractures. The ilioinguinal approach has a large incision and complex anatomical structure, which may damage the femoral vessels and lateral femoral cutaneous nerve during the operation. Because of the need to expose the superficial ring of the inguinal canal during the operation, an inguinal hernia may occur after the operation.^16,17  In recent years, Keel et al¹⁸  proposed a pararectus approach for acetabular fractures involving the quadrilateral plate. The advantage of this approach is that both the operator and the first assistant have a clear field of vision, the quadrilateral plate can be exposed from the pelvis, and the incidence of postoperative inguinal hernia is low. Ma et al¹⁹  have confirmed that the modified Stoppa approach can shorten the operation time and reduce the volume of intraoperative blood loss and blood transfusion. The K-L approach is a classic posterior approach, but there are few studies on the treatment of acetabular fractures involving the quadrilateral plate through a single K-L approach. K-L is often combined with the anterior approach to treat complex acetabular fractures. Other enlarged incisions are used less often because of the high incidence of complications.^16,20  At present, it has been reported that compared with the combined anterior and posterior approach, simultaneous fixation of the anterior and posterior column through a single anterior surgical approach can reduce the incidence of complications.²¹  In this study, the AQALP can be placed through 3 kinds of anterior approaches, and the fixation of the posterior column can be enhanced through the posterior wing of AQALP, so for the patients with no obvious displacement of the posterior column fracture, good reduction of the posterior column fracture can be obtained after the reduction of the anterior column, and fixation of double columns can be completed through a single anterior approach.

In acetabular fractures, the quadrilateral plate is the area with the highest failure rate of internal fixation.²²  How to select a suitable internal fixator to stabilize the quadrilateral plate and block its internal movement is still a major clinical difficulty. Fixation of quadrilateral fractures with screws has the advantage of less trauma, but it has the risk of penetrating into the articular cavity during placement, which is mainly suitable for simple nondisplaced fractures.²³  Cerclage wiring and cables can prevent internal fixation from entering the joint cavity, but it may cause injury to the superior gluteal vasculature and nerve. In addition, the wires may be stuck in the fracture line, and require repeated fluoroscopy during the operation.²⁴  Tile²⁵  and Mast et al²⁶  proposed using T-shaped plates, 1/3 tube plates, and reconstructed plates as buttress plates to support the medial wall of the acetabular quadrilateral plate. Cole and Bolhofner²⁷  used the infrapectineal plate to resist the internal displacement of the fracture fragments of the quadrilateral plate. These plates often require excessive pre-bending during the operation, but the shapes from the ilium to the quadrilateral plate are variable, and the shaping and placement of the spring plates are also difficult, both of which may cause a poor match affecting the stability of the fixation.²⁸  Based on the preceding situations, some scholars^28,29  put forward that an ideal internal fixation for fractures involving the quadrilateral plate should meet the following requirements: (1) can cover the most common fracture lines, (2) can resist the internal movement trend of the quadrilateral plate, (3) can avoid screws entering the hip, and (4) can better serve the bone surface. Fouad³⁰  believes that the anatomic plate should have a large enough contact area with the bone surface to better disperse the stress, especially for patients with osteoporosis. Therefore, based on summarizing previous literature reports, we designed and invented the AQALP for the acetabular fractures involving the quadrilateral plate, which can be placed through a single anterior approach, and its shape is consistent with the shape of the acetabulum, and has a large coverage area. It can fix the anterior and posterior column and quadrilateral plate of the acetabulum as a whole, and restrict the internal movement of the quadrilateral plate fractures.

In this study, 11 cases of acetabular fractures involving the quadrilateral plate were treated with AQALP. As a result, the satisfactory rate of fracture reduction was 90.91% and the satisfactory rate of hip function was 81.82%, which showed the clinical effect was good. Compared with reconstruction plates, in terms of the operation time, it was slightly longer in the observation group, which may be related to the following factors: (1) AQALP is a new acetabular internal fixation device, which requires a certain learning curve; (2) AQALP is a 3-dimensional fixation device, and the position of the anterior and posterior wings should be determined by repeated palpation during the operation to ensure that the position of the plate is proper; and (3) the wings often need to be trimmed to be placed properly. Overall, there was no significant difference in intraoperative blood loss, intraoperative blood transfusion, postoperative blood transfusion, and satisfactory rate of hip function between the 2 groups. Although the satisfactory rate of fracture reduction had no significant difference, a numerically higher satisfactory rate was recorded in the observation group. Above all, these results show that the AQALP is a new choice for the treatment of acetabular fractures, which is suitable for acetabular fractures involving the quadrilateral plate, including anterior column and anterior wall fractures, transverse fractures, T-shaped fractures, double-column fractures, and so on. We believe that AQALP has the following advantages: (1) it is a 3-dimensional anatomical locking plate, which is compatible with the anterior column, anterior wall, and quadrilateral plate of the acetabulum, and has the structure of “1 central part, 1 extended part, and 2 lateral wings.” The central part goes along the upper pelvic rim from the sacroiliac joint to the ipsilateral pubic tubercle, which can be used to fix the fracture of the anterior column and anterior wall of the acetabulum; the lateral wings go down into the pelvic cavity to reduce the quadrilateral plate and block its redisplacement; the extended part with 2.7-mm locking holes goes forward and outward on the basis of the central part to fix the anterior wall fractures which usually are thin; (2) AQALP can work as a template to help the reduction of the fracture; (3) there is little need for pre-bending and shaping during the operation, which can effectively avoid the metal fatigue caused by pre-bending and shorten the operation time; (4) the integrated design can provide 3-dimensional spatial fixation and biomechanical stability; (5) the pre-bending groove on the plate is convenient for proper shaping during the operation to meet the clinical needs; (6) the plate can be trimmed according to the intraoperative situations; (7) for fractures of the anterior column, anterior wall, quadrilateral plate and posterior column, sometimes it can be fixed with just one plate, which not only shortens the operation time, but also reduces the medical cost.

This study also had several limitations: (1) the sample size of the study is relatively small; (2) it is a retrospective study; and (3) although the short-term effect of the AQALP in the treatment of acetabular fractures involving quadrilateral plate is good, the long-term outcomes of more than 10 years is more meaningful.

Runtao Zhou and Mingming Yang contributed equally to this work. Ethical clearance was obtained from the Ethical Committee of First Affiliated Hospital of Chongqing Medical University (Number: 2020–278), and all procedures performed in this study were in accordance with the 1964 Helsinki Declaration. All patients involved in this study gave their consent for the participation, and the informed consent was obtained from all participants. All patients involved in this study gave their consent for the anonymized data to be used for scientific purposes and published in a scientific journal. The datasets generated and analyzed during the current study are not publicly available due to the individual privacy of participants but are available from the corresponding author on reasonable request. The authors declare that there is no conflict of interest regarding the publication of this paper. This work was supported by the Science-Health Joint Medical Scientific Research Project of Chongqing (grant number 2020MSXM058).