Beside spine and pelvis surgery, computer-assisted guidance systems are not used frequently for musculoskeletal injuries. Main reason is the dependence on a fixed reference array that must be firmly attached to all moving parts. We investigated a novel fluoroscopy-based image guidance system in orthopaedic trauma surgery that uses a different technique. This was a prospective, not randomised single centre case series at a level I trauma centre. 45 patients with 46 injuries (foot 12, shoulder 10, long bones 7, hand and wrist 7, ankle 7, spine and pelvis 4) were included. Different surgical procedures were examined following the basic principles of the AO/ASIF. Main outcome measurements were the number of trials for implant placement, total surgery time, usability via user questionnaire and system failure rate. Furthermore we wanted to test the ability of the new system to be integrated in existing surgical workflows. In all cases, the trajectory function was used, inserting a total of 56 guided implants. The trajectory was the most popular feature used by surgeons (n=43, 93.5%), followed by the length measurement tool (n=29, 63%) and the bending function (n=17, 37%). The functions could be freely activated by the performing surgeon. The system failed when used in pelvic and spinal injuries, resulting in a total failure rate of 6.5% (n=3) of all included cases. The overall usability was rated as good, scoring 84.3%. This study examined the clinical application of a fluoroscopy-based image guidance system for different musculoskeletal injuries. Its major advantage is the high integrability in the accustomed surgical workflow and its connectivity with existing technical equipment. It can hardly be compared to known navigation solutions, since instruments are not tracked and fixed reference arrays are not required. Expected advantages should be explored in randomised studies.

Minimally invasive placement of iliosacral screws (SI-screw) is becoming the standard surgical procedure for sacrum fractures. Computer navigation seems to increase screw accuracy and reduce intraoperative radiation compared to conventional radiographic placement. In 2012 an interdisciplinary hybrid operating theatre was installed at the University of Ulm. A floor-based robotic flat panel 3D c-arm (Artis zeego, Siemens, Germany) is linked to a navigation system (BrainLab Curve, BrainLab, Germany). With a single intraoperative 3D scan the whole pelvis can be visualised in CT-like quality. The aim of this study was to analyse the accuracy of SI-screws using this hybrid operating theater.

32 SI-screws (30 patients) were included in this study. Indications ranged from bone tumour resection with consecutive stabilisation to pelvic ring fractures. All screws were implanted using the hybrid operating theatre at the University of Ulm. We analysed the intraoperative 3D scan or postoperative computed tomography and classified the grade of perforation of the screws in the neural foramina and the grade of deviation of the screws to the cranial S1 endplate according to Smith et al. Grade 0 stands for no perforation and a deviation of less than 5 °. Grade 1 implies a perforation of less than 2 mm and a deviation of 5–10°, grade 2 a perforation of 2–4 mm and a deviation of 10–15° and grade 3 a perforation of more than 4 mm and a deviation of more than 15°. All patients were tested for intra- and postoperative neurologic complications and infections. The statistical analysis was executed using Microsoft Excel 2010.

32 SI-screws were implanted in the first 20 months after the hybrid operating theatre had been established in 2012. All 30 patients were included in this study (15 men, 15 women). The mean age was 59 years ±23 (13–95 years). 20 patients received a single screw in S1 (66.7%), 1 patient 2 unilateral screws in S1 and S2 (3.3%), one patient 2 bilateral screws in S1 (3.3%) and 8 patients a single screw stabilising both SI-joints (26.7%). 27 screws showed no perforation (84.4%), 1 screw a grade 1 perforation (3.1%) and 4 screws a grade 2 perforation (12.5%). There was no grade 3 perforation. Furthermore there was no perforation of the neural foramina or the ventral cortex in the axial plane of the SI-screws stabilising one SI-joint (24 screws). Only single SI-screws bridging both SI joints showed a perforation of the neural foramina (37% grade 0, 12.5% grade 1, 50% grade 2, 0% grade 3).

In the frontal plane 23 screws (71.9%) showed a deviation of less than 5°. In 5 screws a grade 1 deviation (15.6%) and in 4 screws a grade 2 deviation (12.5%) could be found. There was no grade 3 deviation. There were no infections or neurological complications.

The high image quality and large field of view in combination with an advanced navigation system is a great benefit for the surgeon. All SI-screws stabilising only one joint showed completely intraosseous placement. Single SI-screws bridging 2 SI-joints intentionally perforated the neural foramina ventrally in 5 cases because of dysmorphic sacral anatomy. This makes image-guided implantation of SI-screws in a hybrid operating theatre a very safe procedure.

The internal fixation of scaphoid bone fractures remains technically difficult due to the size of the bone and its three- dimensional shape. Early rigid fixation, e.g with a screw, has been shown to support good functional outcome. In terms of stability of the fracture, biomechanical studies have shown a superior result with central screw placement in the scaphoid in comparison with an eccentric position, which can lead to delayed or non-union. Image-based navigation could be helpful for these cases. The main limitation of reference-based navigation systems is their dependence on fixed markers like used in modern navigation systems. Therefore it is limited in treatment of small bone fractures. In former experimental studies 20 artificial hand specimens were randomised into two groups and blinded with polyurethane foam: 10 were treated conventionally and 10 were image guided. For trajectory guidance a reduction of duration of surgery, radiation exposure and perforation rate compared to the conventional technique could be found. Accuracy was not improved by the new technique. The purpose of this study was to identify the possible advantages of the new guidance technique in a clinical setting.

In this prospective, non-randomised case series we tested the feasibility of the system into the accommodated surgical workflow. There was no control group. Three cases of scaphoid fractures were included. All of the patients were treated with a cannulated screw following K-wire placement via the percutaneous volar approach described. In addition, length measurements and screw sizes were determined using special features of the system. The performing surgeon and two attending assistant doctors (one assisting the surgical procedure, one handling the guidance system) had to rate the system following each procedure via a user questionnaire. They had to rate the system's integration in the workflow and its contribution to the success of the surgical procedure in percentages (0 %: totally unsuccessful; 100 %: perfect integration and excellent contribution). All of the clinical procedures were performed by the same surgeon.

The surgeons rated the system's contribution and integration as very good (91 and 94 % of 100 %). No adverse event occurred. An average of 1.3 trials ± 0.6 (1; 2) was required to place the K-wire in the fractured scaphoid bone. The dose-area product was 19 cGycm2 ± 3 (16; 22). The mean incision until suture time was 36.7 min ± 5.7 (30; 40). For clinical cases, the system was integrated and rated as very helpful by users.

The system is simple and can be easily integrated into the surgical workflow. Therefore it should be evaluated further in prospective clinical series.

INTRODUCTION

Isolated injuries of the sacral bone are rare. The pathomechanism of these injuries are usually high velocity accidents or falls from large heights. The computer-assisted implantation of iliosacral screws (SI-screw) becomes more important in the treatment of dorsal pelvic ring fractures. The advantage of the minimal-invasive screw placement is the reduction of the non-union and deep wound infection rate. Another advantage of computer-navigated SI-screw placement is the reduction of intraoperative radiation for the patient and the surgical staff. The purpose of this study was to analyse the position of navigated iliosacral screws.

In orthopaedic surgery, as in many other surgical fields, there is a clear tendency towards the use of minimally invasive procedures. These techniques are increasingly being implemented almost routinely for procedures such as spine and pelvis surgery. However, for fracture treatment and for applications involving small bones, such as hand and foot surgery, these systems are hardly ever used. We introduce a new system for image based guidance in traumatology.

We included 20 patients with a fracture of the fifth metatarsal. They were randomised on admission into two groups. Ten patients in the metatarsal group were operated conventionally and ten were operated with the assistance of a new image guidance system. This system is based on 2D-fluoro images which are acquired with a conventional c-arm and are transferred to the system workstation. After detecting marked tools, it can be used to display trajectories for K-wire guidance in the c-arm shot.

The average duration of surgery (time from incision to suture) in the image-based group was 12.7 minutes ± 5.5 (min. 6, max. 23), in the conventional group it was 17 minutes ± 6.5 (min. 7, max. 28) (p=0.086). The average duration of radiation was 18 seconds ± 8.5 (min. 6, max 36) in the image-based group vs. 32.4 seconds ± 19.4 (min. 12, max. 66) in the conventional group (p=0.057). An average of 4.7 C-arm shots ± 2 (min 2, max 9) were necessary in the image-based group to position the K-wire. For the conventional group, 8.2 shots ± 2.3 (min 4, max 12) were used (p=0.0073). It took 1.6 trials ± 0.7 (min.1, max. 3) to position the K-wire for the image-based procedures, in the conventional group 2.7 trials ± 0.9 (min. 1, max 4) were necessary (p=0.0084). There were no malfunctions or adverse events in any of the image-based navigational cases. No screws needed to be replaced in the image-based group. In the conventional group, two screws were replaced intra-operatively because they were too short in the control c-arm shot, and the screw threads did not bridge the fracture gap completely, leading to insufficient compression.

In this pilot study with only a small sample size, the image-based guidance system could be integrated into the existing surgical workflow and was used for applications, where existing navigation systems are not commonly used. The technology gives the surgeon additional information and can reduce the number of trials for perfect implant positioning. This potentially increases the safety of the surgical procedure and spares intact bone substance which is essential for the footing of implants in small bones and fragment fixation. Whether these factors contribute to a reduction in complications or revision rate must be confirmed in larger prospective studies.

Fractures of the femoral head are a challenging problem. The most often performed head preserving procedure worldwide is closed reduction and insertion of cannulated screws under fluoroscopic control. The use of navigation is still experimental in general trauma since rigid reference markers must be attached to all fragments. The examined system (Surgix®, Tel Aviv, Israel) is a fluoroscopy based image analysing system. It consists of a workstation and X-ray opaque markers in surgical tools. When the tool is visible in a C-arm shot a trajectory is displayed as additional layer in the image to serve as guidance for the surgeon.

Forty synthetic femurs (Synbone®, Malans, Switzerland) were used and placed inside foam to simulate the soft tissue of the thigh. The models were equipped with 4.5mm radio-opaque markers at the fovea capitis femoris as target point. The aim was to bring the tip of a K-wire as close as possible to the target point entering the bone at the lateral base of the greater trochanter in a center-center position. Twenty were done under image guidance and 20 were operated the conventional way. Outcome measures included the accuracy (the distance between the tip of the wire and the target in a CT), the number of guide wire insertions, procedure duration, radiation exposure and learning curve.

In the image guided group optimal guide wire placement was accomplished on first pass in 65% of the cases as compared to 5% in the conventional group (p = < 0.0001). The average number of trial and error was significantly lower in the guided group (1.7 vs. 5.8, p = < 0.0001). Consequently the average duration of the guided procedure was significantly shorter (p = 0.0008) along with radiation exposure time reduced by over 70% (p = 0.0002). The guidance system hit averaged 5.8 mm off target as compared to 5.3 mm for the freehand method (p = 0.3319).

Image based guidance significantly shortened the procedure, reduced the radiation exposure and the number of trials without changing the surgeons workflow and can be used in trauma cases were reference marker based navigation is not applicable.

Computer assisted surgery (CAS) is used in trauma surgery to reduce radiation and improve accuracy but it is time consuming. Some trials for navigation in small bone fractures were made, but they are still experimental. One major problem is the fixation of the dynamic reference base for navigation. We evaluated the benefit of a new image based guidance-system (Surgix®, Tel Aviv, Israel) for fracture treatment in scaphoid bones compared to the conventional method without navigation. The system consists of a workstation and surgical devices with embedded radio opaque markers. These markers as well as the object of interest must be on the same C-arm shot. If a tool is detected in an image by the attached workstation additional information such as trajectories are displayed in the original fluoroscopic image to serve the surgeon as aiming device. The system needs no referencing and no change of the workflow.

For this study 20 synthetic hand models (Synbone®, Malans, Switzerland) were randomised in two groups. Aim of this study was a central guide-wire placement in the scaphoid bone, which was blindly measured by using postoperative CT-scans. Significant distinctions related to the duration of surgery, emission of radiation, radiation dose, and trials of guide-wire positioning were observed.

By using the system the surgery duration was with 50 % shortened (p = 0.0054) compared to the conventional group. One reason might be the significant reduction of trials to achieve a central guide-wire placement in the bone (p = 0.0032). Consequently the radiation exposure for the surgeon and the patient could be shortened by reduction of radiation emission (p = 0.0014) and radiation dose (p = 0.0019).

By using the imaged based guidance system a reduction of surgery duration, radiation exposure for the patient and the surgeon can be achieved. By a reduced number of trials for achieving a central guide-wire position the risk of weakening the bone structure can be minimised as well by using the system. The system seems helpful where navigation is not applicable up to now. The surgical workflow does not have to be chanced.