CT-guided percutaneous screw fixation of a talar fracture

Abstract
We report the case of a talar neck fracture treated by CT- and fluoroscopy-guided percutaneous screw fixation. This intervention followed the surgical failure to fix the fracture owing to incorrect positioning of screws under only fluoroscopy. The crucial role of dual guidance, which made the intervention rapid, safe and effective, was confirmed in the therapeutic management of this talar fracture.

Keywords: Talar fracture; Screw fixation; Malunion; CT and fluoroscopy guidance.Introduction

The treatment of talar fractures generally consists of either a cast in neutral position of the foot and ankle for non-displaced fractures, or reduction and internal fixation for displaced fractures 1. Although non-displaced talar fractures can be managed conservatively, screw fixation of these fractures aims at compression across the fracture in order to prevent redislocation and allows for early motion 2, 3. However, surgical treatment may be complicated by superficial wound or deep soft tissues infection, avascular necrosis, malunion and nonunion of talus 1.
As a three-dimensional complex with susceptible structures crowded in a relatively small space, the hindfoot provides only some narrow safe approaches for internal fixation of talar fractures. Consequently, computed tomography (CT) imaging is routinely used to evaluate talar fractures and plan treatment. Mutiplanar reconstructions have also been shown to be useful in the diagnosis and understanding of complex talar fractures.
A third option would thus be CT- and fluoroscopy-guided percutaneous screw fixation which has already been described for the treatment of sacroiliac joint disruptions, acetabular or vertebral pedicle fractures 4-7. Indeed, it was shown that dual guidance allowed to make percutaneous procedures rapid, safe and effective.
However, to the best of our knowledge, such a case about the percutaneous fixation of a talar fracture has not been previously reported in the literature.Case report

A 28-year-old male patient visited our emergency department one hour following a fall from a wall. The result of this traumatic episode was a left ankle trauma. He was complaining of pain and an inability to weight bear. On examination, he had mild swelling around the left ankle. Radiographs and CT scan of the ankle revealed a minimally displaced fracture with a vertical line which passed through the talar neck. Neither comminution nor major displacement was present, excluding the need for a reduction. According to the Hawkins classification, this fracture was thus classified as a type I. Distal tibia and fibula were intact.
Initially, the patient was treated with elevation and icepack.
Surgery was performed through a minimal antero-medial incision. The fracture was fixed under fluoroscopy with two 4.0-mm diameter cannulated self-tapping screws (BCS, Biomet, Varsaw, In, USA).
However, follow-up CT scans showed no evidence of healing owing to the incorrect positioning of the two screws which were thus retrieved.
It was decided following an interdisciplinary meeting between interventional radiologists and orthopedic surgeons that percutaneous screw fixation would be performed.
Two months following surgery, the patient was treated by a senior interventional radiologist (with ten years of experience).
This procedure was performed under surgical conditions of asepsis in an interventional CT room using CT (GE Lightview 8-row MDCT scanner; GE Healthcare, Waukesha, Wis, USA) and lateral fluoroscopy (GE Stenescop C-arm) guidance. The patient was placed in dorsal decubitus on the CT table.
The first part of the intervention was a CT acquisition of the foot to confirm the diagnosis and plan the approach. Millimetric multiplanar reconstructions were analyzed on a GE ADW 4.2 workstation to determine the best possible angle for the trajectory of the guidewire and the positioning of the screws which should be perpendicular to the fracture line. These recontructions were also used to find an anterior path avoiding the vascular (anterior tibial artery), tendinous and nervous structures. Radiopaque markers were put on the skin prior to the insertion of the material. Under local anesthesia (lidocaïne 1% [Xylocaïne; Astra, Sodertalge, Sweden]), a 20-gauge 20-cm Chiba needle (Cook Medical, Bloomington, IN, USA) was inserted using an anterior approach under fluoroscopy until bone contact was obtained. A CT acquisition confirmed the correct positioning of the tip of the needle. Using the Chiba needle, a local anesthesia of the periosteum was then performed.
This needle was then used as a guide for an 13-gauge 10-cm Trocar t’am (Thiebaud, Thonon-les-Bains, France) which was placed under fluoroscopy after the hub had been removed (Fig. 1).
Using CT and fluoroscopy guidance, the Trocar perpendicularly transfixed the talar fracture line. A follow-up via axial CT scan acquisitions (SmartStep system) confirmed the good progression of the Trocar which was stopped immediately before perforating distal cortex. In case of pain, a Chiba needle was inserted inside the Trocar to infuse 1 cc of lidocaïne 1%. A 2.0 mm Kirschner guidewire (Synthes, West Chester, PA, USA) was placed through the cannula of the Trocar.
Following the withdrawal of the Trocar, a 4.0 mm cannulated self-drilling/tapping screw (Asnis III; Stryker, Mahwah, New Jersey, USA) was placed over the Kirschner guidewire under CT and fluoroscopy guidance and screwed with a hollow screwdriver (Fig. 2). 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 (Fig. 3), the guidewire was withdrawn.
To better stabilize the fragments, the same steps were repeated to place a second screw parallel to the first one.
The lengths of the first and second screws were 45 mm and 40 mm, respectively.
A CT scan of the foot was performed at the end of the procedure to confirm the correct fixation of the fracture and eliminate any locoregional complication (Fig. 4).
The procedural time was 60 min. The intervention performed only under local anesthesia was well tolerated by the patient. No haemorraghe was observed.
He was hospitalized for 48 hours in the department of orthopedic surgery. Range of motion exercises and continuous passive motion were started on the second postoperative day.
The patient was then discharged home continuing physiotherapy. He was followed by a senior orthopedic surgeon: at each visit, a CT scan was obtained. The wound healed without any skin complication in a below knee non-weight bearing cast for two weeks. For the next four weeks he was also non-weight bearing in a removable walker (aircast®) boot. He was then restricted to partial weight bearing (50% body weight) for a further six weeks. Full weight-bearing was allowed after 12 weeks when radiological union was evident.
At follow-up after 3 months the patient’s American Orthopaedic Foot & Ankle Society (AOFAS) hind foot score was 100 8. Indeed, he was asymptomatic with no tenderness over the ankle and foot and achieved full range of motion of ankle and subtalar joints. The patient could walk without any problem. Follow-up CT scans showed no evidence of avascular necrosis of the operated talus.
Discussion

This case showed that a minimally displaced talar fracture could be successfully treated by percutaneous screw fixation under CT and fluoroscopy guidance. This technique was first described for the fixation of sacral and acetabular fractures 6, 7. In these reports, the authors showed that CT-guided percutaneous fixation offered several advantages over open reduction and internal fixation. 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 imaging is essential for exact assessment and classification of the fracture and pre-operative planning. Multiplanar reconstructions allow also to rule out a significantly displaced fracture or minor step-off in the affected joint(s).
In our report, the surgical failure to fix the talar fracture could be explained by the fact that the fracture line was hardly visualized under fluoroscopy guidance, leading to the misplacement of screws. In contrast to surgery, percutaneous fixation was guided by the combination of CT and fluoroscopy. Gangi et al. 9 showed in vertebroplasty procedures that this dual guidance allowed 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 posterior arthrodesis of spine, extraction of foreign bodies from soft tissues and screw fixation of sacroiliac joint disruptions 4, 5, 10, 11. Percutaneous fixation could allow here to avoid a malunion or nonunion, one of the main complications of talar fractures. Talar malunions and non-unions which mostly occur after inadequate treatment are debilitating conditions that should usually be treated by surgical correction 1. Treatment options include corrective osteotomy by recreating the former fracture with secondary fixation, free or vascularised bone grafting and salvage procedures by arthrodesis of the ankle, subtalar and/or talonavicular joints 12-14. Given the immense importance of the anatomical integrity of the talus and its joints, talar malunions almost invariably lead to disabling impairment of global foot function. Typical features of malunited talar fractures include varus malalignment of the talar neck leading to a significant decrease of subtalar and mid-tarsal motion, residual step-offs in the articular surface with gradual progression to post-traumatic arthritis, impingement of posterior tibial tendon and tarsal tunnel or sinus tarsi syndrome secondary to prominent malaligned bone fragments 1, 2.
Lastly, percutaneous screw fixation of this talar fracture was easy to carry out. The procedure was performed only under local anesthesia. Moreover, the hardware used in this intervention is available in most hospitals where orthopedic surgery is performed.
This case showed the accuracy of percutaneous screw fixation to treat a non- or minimally displaced talar fracture. A study would be required to assess this minimally invasive technique in the therapeutic management of talar fractures.
Captions for figures

Figure 1. A 13-gauge 10-cm Trocar t’am (Thiebaud, Thonon-les-Bains, France) which was placed under fluoroscopy using an anterior approach.
Figure 2. The placement of a screw. a. A 4.0 mm cannulated self-drilling/tapping screw (Asnis III; Stryker, Mahwah, New Jersey, USA) was placed over the Kirschner guidewire (Synthes, West Chester, PA, USA) and screwed with a hollow screwdriver. b. A follow-up via axial CT scan acquisitions (SmartStep system) confirmed the good progression of the screw.
Figure 3. A sagittal CT reconstruction: one of the two screws (indicated by an arrow) which transfixed the talar fracture line.
Figure 4. An axial CT reconstruction (using the Maximum Intensity Projection technique) that showed the placement of the two screws after percutaneous fixation.