Abstract

Objective

The aim of this study was to evaluate CT- and fluoroscopy-guided percutaneous screw fixation in the management of acetabular roof fractures.
Materials and Methods
Institutional review board approval and informed consent were obtained for this study. Fifty-two consecutive adult patients with a non-displaced and isolated acetabular roof fracture were prospectively treated by an interventional radiologist who made a percutaneous screw fixation under CT and fluoroscopy guidance. All these procedures were performed under local anesthesia. The post-operative follow-up ranged from 36 to 48 months.

Results

For each patient, two 6.5-mm Asnis III screws were inserted to fix the roof acetabular fracture.
The mean procedure time was 45min (range, 30 min – 90 min). No complication was observed. Follow-up CT imaging showed evidence of fracture healing. No evidence of secondary displacement, degenerative changes or screw failure was noted. Using the rating system of D’Aubigne and Postel, all patients had excellent results.

Conclusion

The results of our study showed that non-displaced acetabular roof fractures could be successfully treated by a minimally invasive technique with an excellent long-term outcome.

Keywords: Acetabular fracture. Screw fixation. CT and fluoroscopy guidance. Interventional radiology

Introduction

The treatment of acetabular fractures generally consists of either bed rest and traction for simple minimally displaced fractures, or open reduction and internal fixation for complex or significantly displaced fractures [1-4]. Although non-displaced or mild displaced acetabular fractures can be managed conservatively, internal fixation of these fractures could prevent secondary displacement and allow early weight bearing. However, traditional surgical treatment requires extensive exposure, which may be complicated by infection, blood loss, wound healing problems, abductor weakness, sciatic nerve palsy, and heterotopic ossification [5].
As a three-dimensional complex with susceptible structures crowded in a relatively small space, the pelvis provides only some narrow safe corridors for percutaneous screw fixation of acetabular fractures. Consequently, computed tomography (CT) imaging is routinely used to evaluate acetabular fractures and plan treatment [6]. Mutiplanar reconstructions have also been shown to be useful in the diagnosis and understanding of complex acetabular fractures. However, despite this planning with a pre-operative CT scan, only fluoroscopy-guided percutaneous screw fixation remains a technically demanding procedure which may be complicated by neural or vascular injuries [7-9]. Inaccurate insertion of screw can also jeopardize intrapelvic organs [9]. A third option would thus be CT-guided percutaneous screw fixation of acetabular fractures, which was first described by Gay et al. in 1992 [10].
This technique not only avoids extensive exposure but also allows to achieve maximum accuracy. The combination of CT and fluoroscopy guidance could reinforce its place in the therapeutic management of acetabular fractures. Indeed, it was shown that this dual guidance allowed to make percutaneous procedures (such as vertebroplasty or posterior arthrodesis of spine) rapid, safe and effective [11, 12].
The purpose of our study was to evaluate CT- and fluoroscopy-guided percutaneous screw fixation in the management of acetabular roof fractures.

Materials and methods
Patients

All procedures in this study were approved by the Institutional Review Board of our institution. Patients were enrolled after giving written informed consent. From January 2003 to January 2006, 52 consecutive adult patients with an acetabular roof fracture were prospectively treated in our department of radiology by percutaneous screw fixation under CT and fluoroscopy guidance. Patients were eligible for inclusion if they had on their CT scan a non-displaced or minimally displaced acetabular roof fracture which should also be isolated. Patients with significant subchondral impaction, free intra-articular fragments or displaced fractures were not included.
There were 30 men and 22 women. The mean age ± standard deviation (SD) was 47 ± 14 years (range, 19 – 88 years). The mechanisms of injury were a road traffic accident for 42 patients and a fall for ten.
A CT scan was performed for each patient prior to the intervention. Transverse acetabular fractures involving a single fracture line (with an antero-posterior orientation) which crossed the acetabulum through both posterior and anterior columns were identified. According to the AO and Orthopaedic Trauma Association Classification [13], these fractures were thus classified 62-B1. Neither comminution nor displacement was present, excluding the need for a reduction. The obturator ring was also intact, eliminating the possibility of an associated T-type fracture. Transverse fractures were then classified according to their relationship to the roof of the acetabulum: in our study, the fracture lines divided the roof of the acetabulum (i.e., transtectal). No displacement of the femoral head was observed.

Technique of percutaneous screw fixation

Procedure were decided only following an interdisciplinary meeting between interventional radiologists and orthopedic surgeons. All patients were treated by a senior interventional radiologist (with ten years of experience).
After haemostatic control, procedures were performed under surgical conditions of aseptia in an interventional CT room using CT (GE Lightview 8-row MDCT scanner; GE Healthcare, Milwaukee, Wis, USA) and lateral fluoroscopy (GE Stenescop C-arm) guidance. Patients were placed in a lateral decubitus position on the CT table, and stabilized with an Olympic Vac-Pac (Natus Medical, San Carlos, CA, USA).
The first part of the intervention was a CT acquisition of the pelvis with the following parameters: collimation, 8 x 1.25 mm at 100 kV and 250 mAs; rotation time, 0.5 second; pitch, 1.4; field of view, 500 mm, matrix, 512 × 512; standard soft-tissue kernel. Multiplanar reconstructions (with a slice thickness of 1.25 mm) were analyzed on a GE ADW 4.2 workstation to confirm the diagnosis and plan the approach. More precisely, this CT scan allowed to:
– analyze the anatomy of the acetabulum and the position of surrounding neurovascular structures.
– determine the best approach so that the direction of screws can be perpendicular to the plane of the fracture line to be fixed. An imaginary line of the proper screw trajectory avoiding the neurovascular structures was drawn on the CT image for guidance: a skin entry point was thus determined.
– and calculate the optimal length of the screws.
Radiopaque markers were put on the skin prior to the insertion of the hardware. Using a 20-gauge 20-cm Shiba needle (Cook Medical, Bloomington, IN, USA), local anesthesia (lidocaïne 1% [Xylocaïne; Astra, Sodertalge, Sweden]) was administered from subcutaneous tissues to bone contact under fluoroscopy guidance according to the angle previously determined. A CT acquisition confirmed the correct positioning of the tip of the needle (Fig. 1).
This needle was then used as a guide for an 13-gauge 10-cm Trocar t’am (Thiebaud, Thonon-les-Bains, France) which was inserted under fluoroscopy after the hub had been removed (Fig. 2).
Using fluoroscopy guidance, the Trocar perpendicularly transfixed the acetabular fracture line. A follow-up via axial CT scans (SmartStep system) confirmed the good progression of the Trocar which was stopped immediately before perforating distal cortex. In case of pain, a Shiba needle was inserted inside the cannula to infuse 1 cc of lidocaïne 1%. A 2.0 mm Kirschner guidewire (Synthes, West Chester, PA, USA) was placed through the cannula (Fig. 3).
Following the withdrawal of the cannula Trocar, a 6.5-mm cannulated self-drilling/tapping screw (Asnis III; Stryker, Mahwah, New Jersey, United States) was placed over the Kirschner guidewire under fluoroscopy guidance. Screw fixation was performed using a hollow screwdriver (Fig. 4). The correct length of the screw was estimated by measuring the distance between the proximal and distal cortices on the axial CT images. Once the good positioning of the screw was confirmed by a CT scan, the guidewire was withdrawn (Fig. 5).
When it was indicated to better stabilize the fragments, the same steps were repeated to place another screw parallel to the first one.
A pelvic CT scan was performed at the end of the procedure to confirm the correct fixation of the fracture and eliminate any locoregional complication.

Follow-up

The post-operative follow-up which was performed by an independent assessor, an orthopaedic surgeon, ranged from 36 to 48 months. At each visit, plain radiographs and CT scan were performed.
The clinical outcome of all patients was assessed at final follow-up using the rating system described by D’Aubigne and Postel [14]. This method of grading functional value of hip includes the following criteria: pain (scored from 0: pain intense and permanent to 6: no pain), mobility (from 0: ankylosis with bad position of the hip to 6: flexion of more than 90 degrees; abduction to 30 degrees) and ability to walk (from 0: none to 6: normal). Only absolute results were determined (the functional value of the hip was evaluated only after the intervention).

Results

The mean interval between the injury and percutaneous screw fixation was 14 days (range, 2 – 30 days).
For each patient, two screws were inserted to fix the roof acetabular fracture. The mean length of screws was 54 mm (range, 40 mm – 65 mm). In all cases, screws were successfully placed in only one attempt (i.e., without intra-articular penetration and cortical perforation).
The mean procedure time was 45 min (range, 30 min – 90 min). The intervention was well tolerated by patients. No hemorraghe haemorraghe was observed.
They were hospitalized for 48 hours in the department of orthopedic surgery. Physiotherapy was started on the first postoperative day with continuous passive motion. Assisted active range of motion and isometrical exercises were initiated on the second postoperative day. All patients began to walk with crutches within 2 days of the procedure.
Follow-up CT imaging showed evidence of fracture healing. No superficial or deep infection occurred. No evidence of secondary displacement of the fragments, degenerative changes, screw failure or lucency adjacent to screws was noted. No heterotopic ossification was also observed.
Using the rating system of D’Aubigne and Postel [14], all patients had very good excellent results (score ? 16/18 with each criterion scored 5 or 6 out of 6), which corresponded to walk without cane (with no pain and no limp: pain + ability to walk = 12/12; with no pain but with slight limp: 11/12; or with no limp but with mild and inconstant pain: 11/12) and to mobility normal (6 : flexion of more than 90 degrees; abduction to 30 degrees) or nearly normal (5: flexion between 80 and 90 degrees: abduction of at least 15 degrees).

Discussion

The results of our study showed that non-displaced or minimally displaced acetabular roof fractures could be successfully treated by percutaneous screw fixation under CT and fluoroscopy guidance with an excellent long-term outcome. This technique of percutaneous fixation was first described by Gay et al. in 1992 [10]. In their report including six patients, they showed that it offered several advantages over open reduction and internal fixation of acetabular fractures. First, soft-tissue disruption with the potential for devascularization or denervation is virtually eliminated. Blood loss is also significantly decreased, and a lower risk of infection may be anticipated owing to decreased tissue trauma and the lack of an open wound. Second, functional recovery was improved: patients could begin more rapidly weight-bearing, avoiding decubitus complications Third, CT scans were useful to evaluate the severity and geometry of the fractures. Such imaging is in particular vital to exclude the presence of small free fragments of bone within the hip joint space [6]. When such fragments are identified, an open procedure is necessary because even small chips can cause significant damage to the joint with weight-bearing and movement. Three-dimensional reconstructions were also used to plan fixation procedure. The risks of the procedure are primarily those related to damage to neurovascular structures crowded in a relatively small space: the pelvis provides only some narrow safe corridors for percutaneous screw fixation of acetabular fractures. Consequently, the procedure must be planned so that the path of the hardware will not injure these structures.
In our study, percutaneous fixation performed only under local anesthesia was guided by the combination of CT and fluoroscopy. Gangi et al. [11] showed in vertebroplasty procedures that this dual guidance could allow to facilitate needle placement and reduce complications. The crucial role of dual guidance, which made the intervention rapid, safe and effective, was confirmed in various percutaneous interventions including extraction of foreign bodies from soft tissues, posterior arthrodesis of spine, and screw fixation of vertebral pedicle fractures [12, 15, 16]
Moreover, the hardware used in this procedure is available in most hospitals where orthopedic surgery is performed. Moreover, we attribute the absence of complications with this technique to the fact that insertion of the screws is technically easy under CT and fluoroscopy guidance, and the learning curve, therefore, is short. The good reproducibility of this technique was also strongly suggested by Gay et al. [10]: in their study, two radiologists, two orthopedic surgeons, and three orthopedic residents participated in the six procedures at various times, and only one technical failure occurred.
Lastly, the follow-up of our patients showed an excellent long-term outcome with a functional recovery which was not affected by the occurrence of hip degenerative changes.
Our study showed the accuracy of percutaneous screw fixation to treat non-displaced or minimally displaced acetabular roof fractures. New challenges would be the assessment of this minimally invasive technique to fix complex and displaced acetabular fractures, and the extension to the treatment of other pelvic ring fractures as already described for the screw fixation of sacroiliac joints disruptions [17, 18]. The place of such a technique in the therapeutic management of polytraumatized patients remains also to be defined in collaboration with orthopedists who tend increasingly to give priority to less invasive procedures by using two-dimensional and three-dimensional fluoroscopy- or CT-based navigation techniques for the percutaneous treatment of acetabular fractures [19-21].