Malreduction of the syndesmosis is a poor prognosticator following ankle fracture and has been documented in as many as 52% of patients following fracture fixation. The current standard for assessment of reduction of the syndesmosis is bilateral computed tomography (CT) scan of the ankle. Multiple radiographic parameters are utilized to define malreduction, however, there has been limited investigation into the accuracy of these measurements to differentiate malreduction from inherent anatomical asymmetry. The purpose of this study was to identify the prevalence of positive malreduction standards within the syndesmosis of native, uninjured ankles. Bilateral lower extremity CT scans including ankles were screened. Studies were excluded if the patient was skeletally immature, had pathology below the knee or if they had congenital neuromuscular syndromes. The resulting cohort consisted of 207 patients. The indication for bilateral CT scan was femoral acetabular impingement in 110 patients (53%), rotation assessment following arthroplasty in 32 patients (15%), rotation assessment following femoral fracture in 30 patients (14%), rotational assessment for patellar instability in 30 patients (14%) and five miscellaneous indications (2%). Fifty patients were reviewed by three observers independently and to determine inter-observer reliability. A single observer repeated the measurements within the same cohort four weeks later to evaluate intra-observer reliability. Three observers then measured the anterior syndesmotic distance, posterior syndesmotic distance, central syndesmotic distance, fibular rotation and sagittal fibular translation at 1cm from the distal tibial articular surface. Overall side to side variability between the left and right ankle were assessed. Previously studied malreduction standards were evaluated. These included: anterior to posterior syndesmotic distance > 2mm, central syndesmotic difference > 1.5mm, average syndesmotic distance > 2mm, fibular rotational difference > 10o and sagittal translational difference > 2mm. The inter- and intra-observer reliability was good to excellent for anterior, posterior and central syndesmotic distance, and fibular rotation measurements. Sagittal fibular translation had an ICC of 0.583, and thus was only of fair reliability. Side to side comparison revealed statistically significant difference in only anterior syndesmotic difference (p=0.038). A difference of anterior to posterior syndesmotic distance of greater than 2mm was observed in 43 patients (20.2%). Thirty eight patients (17.8%) had a central syndesmotic difference of greater than 1.5mm. A fibular rotational difference of greater than 10o was observed in 49 patients (23%). The average difference between the anterior and posterior syndesmosis was greater than 2mm in 17 patients (8.2%). Nine patients (4.2%) had sagittal translation of greater than 2mm. Eighty one patients (39%) demonstrated at least one parameter beyond previously set standards for malreduction. Only one parameters was anomalous in 54 patients (26%), 18 patients (8%) had two positive parameters, while eight patients (4%) had three. One patient was asymmetrical in all measured parameters. In this study there was no statistically significant asymmetry between ankles. However, 39% of native syndesmoses would be classified as malreduced on CT scan using previously studied malreduction limits. Current radiographic parameters are not sufficient to differentiate mild inherent anatomical asymmetry from malreduction of the syndesmosis

Introduction. Previous studies have demonstrated the need of accurate reduction of ankle syndesmosis. Measurement of syndesmosis is difficult on plain radiographs. Recently, a difference of 2mm in anterior and posterior measurements at incisura of the inferior tibio-fibular joint on CT has been described as a measure of malreduction (depicted as ‘G’ for ease of description). Our practice changed towards routine post operative bilateral CT following syndesmosis fixation to assess the reduction and identify potential problems at an early stage. The aim of this primarily radiological study was to determine if the use of bilateral cross sectional imaging brings additional benefit above the more conventional practice of unilateral imaging. Method. Between 2007 and 2009, nineteen patients with ankle fractures involving the syndesmosis were included in the study group who had bilateral CT post operatively. The values of ‘G’ and the mean diastasis (MD) were calculated, representing the average measurement between the fibula and the anterior and posterior incisura. Results. When compared to the normal side, eight out of nineteen (42%) cases were found to have a residual diastasis even after fixation across the syndesmosis, However, if a standard value of G(2mm) was used for the injured leg only, all of the nineteen cases would have abnormal values of ‘G’ following reduction. The value of G for the injured side was poorly correlated with the mean inter-limb diastasis (MD, R=0.23). Discussion. Our study has clearly demonstrated the need for individualising the assessment method to guide surgeons and radiologists prior to revision surgery. A standard value of ‘G’ of 2mm as the normal limit cannot be applied universally as apparent from the data presented in this study

Tibial plateau fractures are common injuries. Displaced fractures are treated with open reduction and internal fixation (ORIF). Goals of treatment include restoration of extremity axial alignment, joint stability and congruity, allowing for early motion and prevention of osteoarthritis. Short term results of surgical fixation of tibial plateau fractures are good, however, longer term outcomes have demonstrated a higher risk of end-stage arthritis and total knee arthroplasty. Despite the vast literature around tibial plateau fractures, to our knowledge there are no series examining post-operative reductions using axial imaging. It is our goal to define the incidence of articular malreductions following surgical fixation of tibial plateau fractures, to identify patient or surgeon factors associated with malreductions, and to define any regional patterns of malreduction location. De-identified post operative computed tomography (CT) scans were reviewed to identify tibial plateau malreductions with a step or gap greater than 2 mm, or condylar width greater than 5 mm. Three independent assessors reviewed the scans meeting criteria using Osirix DICOM software. Steps and gaps were mapped onto the axial sequence at the level of the joint line. Images were then matched to side and overlaid as best fit in Photoshop software to create a map of malreductions. A grid was created to divide the medial and lateral plateaus into quadrants to identify the density of malreductions by location. A multi-variate regression model was used to assess risk factors for malreduction. Sixty five post-operative CT scans were reviewed. Twenty one reductions had a step or gap more than 2 mm for a malreduction incidence of 32.3%. The incidence in patients undergoing submeniscal arthrotomy or fluoroscopic assisted reduction was 16.6% and 41.4%, respectively (p <0.001). Side of injury, age, BMI, AO fracture type, and use of locking plates were not predictive of malreduction. Malreductions were heavily weighted to the posterior lateral tibial plateau. The incidence of articular malreductions was high at 32.3%. Fluoroscopic reduction alone was a predictor for articular malreduction with most malreductions located in the posterior lateral quadrants of the plateau

Ankle fractures are the fourth most common fracture requiring surgical management. The deltoid ligament is considered the primary stabilizer of the ankle against a valgus force. The management of the deltoid ligament in ankle fractures is currently a controversial topic no consensus exists regarding repair in the setting of ankle fractures. The purpose of this systematic review is to examine the role and indications for deltoid ligament repair in ankle fractures. A systematic database search was conducted with Medline, Pubmed and Embase for relevant studies discussing patients with ankle fractures involving deltoid ligament rupture and repair. The papers were screened independently and in duplicate by two reviewers. Study quality was evaluated using the MINORs criteria. Data extraction included post-operative outcomes, pain, range of motion (ROM), function, medial clear space (MCS), syndesmotic malreduction and complication rates. Following title, abstract and full text screening, 10 eligible studies published between 1987 and 2017 remained for data extraction (n = 528). The studies include 325 Weber B and 203 Weber C type fractures. Malreduction rate in studies with deltoid ligament repair was 7.4% in comparison to those without repair at 33.3% (p < 0.05). Eleven (4%) of deltoid ligament repair patients returned for re-operation to have implants removed in comparison to eighty three (42%) of those without repair (p < 0.05). There was no significant difference for pain, function, ROM, MCS and complication rates (p < 0.05). The mean operating time of deltoid ligament repair groups was 20 minutes longer than non-repair groups(p < 0.05). Deltoid ligament repair offers significantly lower syndesmotic malreduction rates and reduced re-operation rates for hardware removal when performed instead of transsyndesmotic screw fixation. When compared to non-repair groups, there are no significant differences in pain, function, ROM, MCS and complication rates. Deltoid ligament repair should be considered for ankle fracture patients with syndesmotic injury, especially those with Weber C. Other alternative syndesmotic fixation methods such as suture button fixation should be explored. A large multi-patient randomized control trial is required to further examine the outcomes of ankle fracture patients with deltoid ligament repair

Flexible fixation techniques combined with anatomic (open) syndesmosis reduction have demonstrated improved functional outcomes and rates of malreduction. Suture-button devices allow physiologic motion of the syndesmosis without need for implant removal, which may lower the risk of recurrent syndesmotic diastasis. There is limited longer-term assessment of the maintenance of reduction between static and flexible syndesmotic fixation using bilateral ankle CT evaluation. This is an a priori planned subgroup analysis of a multi-centre, randomized clinical trial comparing static syndesmosis fixation (two 3.5 mm screws) with flexible fixation (single knotless Tightrope) for patients with AO- OTA 44-C injuries. Patients who completed bilateral ankle CT scans at 3- and 12-month follow-up were included. The primary outcome measure was syndesmotic malreduction based on bilateral ankle CT scans, using the uninjured, contralateral ankle as a control. Anterior (ASD), middle (MSD), and posterior (PSD) syndesmosis distance were calculated to measure syndesmosis reduction. Secondary outcomes included re-operation, adverse events and functional outcomes including the EQ5D, Olerud-Molander Ankle Score (OM), Foot and Ankle Disability Index (FADI), and Work Productivity Activity Impairment Questionnaire (WPAI). Paired samples t-tests were used to compare injured to control ankles (R, v 3.5.1). 42 patients (24 Group S, 18 Group T) were included. ASD for Group T was 5.22mm (95%CI 4.69–5.77) at 3 months compared to 4.26mm (95%CI 3.82–4.71; p=0.007) in controls and 5.38mm (95%CI 4.72–6.04) at 12 months compared to 4.44mm (95%CI 3.73–5.16; p=0.048) in controls. ASD for Group S was 4.63mm (95%CI 4.17– 5.10) at 3 months compared to 4.67mm (95%CI 4.24–5.10; p=0.61) in controls, but significantly increased to 5.73mm (95%CI 4.81–6.66) at 12 months compared to 4.65mm (95%CI 4.15–5.15; p=0.04) in controls. MSD results were similar; Group T had a larger MSD than control ankles at 3 months (p=0.03) and 12 months (p=0.01), while the MSD in Group S was not different at 3 months (p=0.80) but increased at 12 months (p=<0.01). 88% (21/24) of Group S had broken or removed screws by 12 months. Unplanned re-operation was 15% in Group S and 4% in Group T (p=0.02), with an overall re-operation rate of 30% in Group S. There was no significant difference between treatment groups for EQ-5D, OM, FADI or WPAI at 3- or 12-month follow-up. Tightrope fixation resulted in greater diastasis of the ASD and MSD compared to contralateral, uninjured ankles at 3- and 12-months post-fixation. Group S initially had syndesmotic reduction similar to control ankles, but between 3- and 12-months post-fixation, there was significantly increased syndesmosis diastasis compared to controls. The majority of Group S (88%) had either broken screws or scheduled screw removal, which may explain the increased tibio-fibular diastasis seen at 12-months

The purpose of this project was to evaluate North American trauma surgeon preferences regarding patient positioning for antegrade fixation of mid shaft femoral shaft fractures. This project was a cross sectional survey taken of orthopaedic fellows and staff surgeons, belonging to three organizations across North America. An estimated sample size was calculated a priori, while various online techniques were utilized to reduce non responder and fatigue bias. The survey was distributed multiple times to optimize yield. Two hundred twelve (212) participants responded in full, 134 (56%) of whom practiced in Canada. The majority of surgeons worked in level one trauma centres (74%), while 72% treated more than one femoral shaft fracture per week. The most common patient position for mid shaft fixation amongst all surgeons was lateral positioning with manual traction (68%), however community surgeons were significantly more likely to use a fracture table. The most common difficulties faced with using a fracture table were inability to achieve fracture reduction and peroneal nerve palsies. The majority (64%) of surgeons quoted a complication rate with fracture tables of greater than 1 per 100 cases. Lateral position with use of manual traction is the preferred set up for antegrade fixation of femoral shaft fracture in this large North American cohort of trauma surgeons. However, a large subset of community and non academic surgeons still prefer use of the fracture table. Amongst all respondents, a high rate of fracture table complications, including malreduction, were quoted. To date, there is no prospective data comparing these two options for patient positioning, and a randomized controlled trial may be an appropriate next step

Traditional screw fixation of the syndesmosis can be prone to malreduction. Suture button fixation however, has recently shown potential in securing the fibula back into the incisura even with intentional malreduction. Yet, if there is sufficient motion to aid reduction, the question arises of whether or not this construct is stable enough to maintain reduction under loaded conditions. To date, there have been no studies assessing the optimal biomechanical tension of these constructs. The purpose of this study was to assess optimal tensioning of suture button fixation and its ability to maintain reduction under loaded conditions using a novel stress CT model. Ten cadaveric lower limbs disarticulated at the knee were used. The limbs were placed in a modified external fixator frame that allows for the application of sustained torsional (5 Nm), axial (500 N) and combined torsional/axial (5Nm/500N) loads. Baseline CT scans of the intact ankle under unloaded and loaded conditions were obtaining. The syndesmosis and the deltoid ligament complex were then sectioned. The limbs were then randomised to receive a suture button construct tightened at 4 kg force (loose), 8 kg (standard), or 12 kg (maximal) of tension and CT scans under loaded and unloaded conditions were again obtained. Eight previously described measurements were taken from axial slices 10 mm above the tibiotalar joint to assess the joint morphology under the intact and repair states, and the three loading conditions: a measure of posterolateral translation (a, b), medial/lateral translation (c, g), a measure of anterior-posterior translation (f), a ratio of anterior-posterior translation (d/e), an angle (Angle 1) created by a line parallel to the incisura and the axis of the fibula, and an angle (Angle 2) created between the medial surfaces of two malleoli. These measurements have all been previously described. Each measurement was taken at baseline and compared with the three loading scenarios. A repeated measures ANOVA with a Bonferroni correction for multiple comparisons was used to test for significance. Significant lateral (g, maximum 5.26 mm), posterior (f, maximum 6.42 mm), and external rotation (angle 2, maximum 11.71°) was noted with the 4 kg repair when compared to the intact, loaded state. Significant posterior translation was also seen with the both the 8 kg and 12 kg repairs, however the incidence and magnitude was less than with the 4 kg repair. Significant overcompression (g, 1.69 mm) was noted with the 12 kg repair. Suture button constructs must be appropriately tensioned to maintain reduction and re-approximate the degree of physiological motion at the distal tibiofibular joint. If inserted too loosely, these constructs allow for supraphysiologic motion which may have negative implications on ligament healing. These constructs also demonstrate overcompression of the syndesmosis when inserted at maximal tension however the clinical effect of this remains to be determined

Nearly one quarter of ankle fractures have a recognized syndesmosis injury. An intact syndesmosis ligament complex stabilizes the distal tibio-fibular joint while allowing small, physiologic amounts of relative motion. When injured, malreduction of the syndesmosis has been found to be the most important independent factor that contributes to inferior functional outcomes. Despite this, significant variability in surgical treatment remains. This may be due to a poor understanding of normal dynamic syndesmosis motion and the resultant impact of static and dynamic fixation on post-injury syndesmosis kinematics. As the syndesmosis is a dynamic structure, conventional CT static images do not provide a complete picture of syndesmosis position, giving potentially misleading results. Dynamic CT technology has the ability to image joints in real time, as they are moved through a range-of-motion (ROM). The aim of this study was to determine if syndesmosis position changes significantly throughout ankle range of motion, thus warranting further investigation with dynamic CT. This is an a priori planned subgroup analysis of a larger multicentre randomized clinical trial, in which patients with AO-OTA 44-C injuries were randomized to either Tightrope or screw fixation. Bilateral ankle CT scans were performed at 1 year post-injury, while patients moved from maximal dorsiflexion (DF) to maximal plantar flexion (PF). In the uninjured ankles, three measurements were taken at one cm proximal to the ankle joint line in maximal DF and maximal PF: Anterior (ASD), middle (MSD), and posterior (PSD) syndesmosis distance, in order to determine normal syndesmosis position. Paired samples t-tests compared measurements taken at maximal DF and maximal PF. Twelve patients (eight male, six female) were included, with a mean age of 44 years (±13years). The mean maximal DF achieved was 1-degree (± 7-degrees), whereas the mean maximal PF was 47-degrees (± 8-degrees). The ASD in DF was 3.0mm (± 1.1mm) versus 1.9mm (± 0.8mm) in PF (p<0.01). The MSD in DF was 3.3mm (±1.1mm) versus 2.3mm (±0.9mm) in PF (p<0.01). The PSD in DF was 5.3mm (±1.5mm) versus 4.6mm (±1.9mm) in PF (p<0.01). These values are consistent with the range of normal parameters previously reported in the literature, however this is the first study to report the ankle position at which these measurements are acquired and that there is a significant change in syndesmosis measurements based on ankle position. Normal syndesmosis position changes in uninjured ankles significantly throughout range of motion. This motion may contribute to the variation in normal anatomy previously reported and controversies surrounding quantifying anatomic reduction after injury, as the ankle position is not routinely standardized, but rather static measurements are taken at patient-selected ankle positions. Dynamic CT is a promising modality to quantify normal ankle kinematics, in order to better understand normal syndesmosis motion. This information will help optimize assessment of reduction methods and potentially improve patient outcomes. Future directions include side-to-side comparison using dynamic CT analysis in healthy volunteers

Introduction. In this cohort study, the TightRope® fixation technique has been compared with the traditional screw fixation for ankle syndesmosis injuries, with respect to the accuracy of the syndesmotic reduction and their clinical correlation. Patients and Methods. This cohort study included consecutive patients treated for ankle syndesmotic diastases between July 2007 and June 2009. Single slice axial CT scans of both the ankles together were performed at the level of syndesmosis, 1 cm above the tibial plafond. More than 2 mm widening of syndesmosis as compared to normal contra-lateral ankle was considered as significant malreduction. Clinical outcomes were measured using AOFAS and FADI Scores. Results. Forty-six out of 55 eligible patients attended for the study. Twenty three patients were in the tightRope group and 23 in the syndesmosis screw group. Mean follow-up was 2.5 (1.5–3.5) years. Average age was 41.6 years in tightrope group and 39.8 years in syndesmosis screw group. The mean width of normal syndesmosis was 4.01 + 0.89 mm. In tightRope group the mean width of syndesmosis was 4.37 + 1.12 mm (t-test, p = 0.30) as compared to 5.16 + 1.92 mm in screw group (t-test, p = 0.01). Five (21.7%) out of 23 ankles in screw group had syndesmotic mal reduction, while none of the tightRope group showed mal-reduction on CT scans (fisher's exact test, p = 0.04). There was no significant difference in mean post operative AOFAS score (89.56 and 86.52) and FADI score (82.42 and 81.22) between two groups. Conclusion. The results of this study indicate that tightRope provides more accurate method of syndesmosis stabilization as compared with screw fixation. Syndesmosis malreduction is the most important independent predictor of clinical outcomes; therefore care should be taken to reduce the syndesmosis accurately

Purpose. Femoral shaft fractures are routinely treated using antegrade intramedullary nailing under fluoroscopic guidance. Malreduction is common and can be due to multiple factors. Correct entry point identification can help minimize malreduction and the risk of iatrogenic fracture. This study aims to compare landmark identification used to guide nail entry, the piriformis fossa (PF) and the trochanteric tip (T), via computer navigation and conventional fluoroscopy. Method. The location of the PF and T were digitized under direct visualization with a three-dimensional scribe on ten, fresh-frozen cadaveric right femora (two male, eight female) by three fellowship trained orthopaedic surgeons. To estimate inter- and intraobserver reliability of the direct measurements, an intraclass correlation coefficient was calculated with a minimum of two weeks between measurements. Under navigation, each specimen was draped and antero-posterior (AP) and lateral radiographs of the proximal femur were taken with a c-arm and image intensifier. The c-arm was positioned in a neutral position (0 for AP, 90 for lateral) and rotated in 5 increments, yielding a range of acceptable images. Images, in increments of 5, within the AP range (with a neutral lateral) were loaded into a navigation system (Stryker, MI). A single surgeon digitized the T and PF directly based on conventional fluoroscopy, and again directed by navigation, yielding two measurements per entry point per specimen. This was repeated for the lateral range. Hierarchical linear modelling and a Wilcox rank test were used to determine differences in accuracy and precision, respectively, in the identification of PF and T using computer navigation vs. conventional fluoroscopy. Results. The average range of suitable images for both the AP and lateral images was 29 (range of 25 to 30). The location of the PF and T was found to be reliable for a single observer (0.98 and 0.99) and between observers (0.96 and 0.93). Similar accuracy was found in identifying PF under navigation and fluoroscopy (0.05 to 1.4 cm and 0.1 to 1.5 cm respectively, p = 0.26), whereas improved accuracy was found for T using fluoroscopy (0.07 to 2.5 cm) as compared to navigation (0.2 to 2.2 cm, p < 0.001). For both the PF and T, the navigation-based points had greater precision than those selected by fluoroscopy alone (p = 0.001 and p = 0.024). Conclusion. The ideal entry point, under direct visualization, was highly repeatable, indicating that the surgeons could identify their targeted point of entry for both the PF and T. However, there is an arc of approximately 30, through which acceptable AP and lateral images can be obtained. Throughout this range, the location of the PF and T can vary up to 1.5 and 2 cm, respectively. Navigation was less accurate than fluoroscopy in the T selection, yet had greater precision for both points. Thus, while navigation may decrease accuracy in selection of the T, it is more repeatable overall and equally accurate in selecting the PF

The outcome of 77 high energy tibial plateau fractures treated by locking or conventional plating was reviewed. The aim of the study was to determine if there was any advantage of locking plates in reducing the complication rates associated with fixation of these injuries. All patients had a high energy injury pattern (medial or bicondylar plateau fractures). There were 32 locked plates and 45 non-locking plates used. Compartment syndrome complicated 5 patients (16%) in the locked plate group and 3 (7%) in the non-locked group (p = 0.198). Superficial infection occurred in 4 (13%) patients with locked plates and 7 (16%) patients with non-locked plates. Thromboembolic complications occurred in 3 (7%) patients treated with non-locked plates. There were no thrombembolic complications in the locked plate group (p = 0.135). Overall, malunion of the plateau occurred in 10 (22%) patients treated with non-locked plates compared to 7 (22%) patients who received locked plates. This was due to residual malreduction in 4 (13%) patients in the locked plate group and 6 (13%) patients in the non-locked plate group at the time of surgery. In the remaining cases loss of reduction after fixation occurred in 4 (9%) patients who received non-locked plates and in 3 (9%) patients who were treated with locked plates. No statistically significant difference was noted in the treatment outcomes of patients managed with locked plates or non-locked plates, regardless of fracture severity. We concluded that there is no definite advantage associated with the use of locked plating for high energy tibial plateau fractures

Intramedullary nailing is the standard fixation method for displaced diaphyseal fractures of the tibia in adults. Anecdotal clinical evidence indicates that current nail designs do not fit optimally for Asian patients. This study aimed to develop a method to quantitatively assess the fitting of two nail designs for Asian tibiae. We used 3D models of two different tibial nail designs (ETN (Expert Tibia Nail) and ETN-Proximal-Bend, Synthes), and 20 CT-based 3D cortex models of Japanese cadaver tibiae. The nail models were positioned inside the medullary cavity of the intact bone models. The anatomical fitting between nail and bone was assessed by the extent of the nail protrusion from the medullary cavity into the cortical bone, which in a real bone would lead to axial malalignments of the main fragments. The fitting was quantified in terms of the total surface area, and the maximal distance of nail protrusion. In all 20 bone models, the total area of the nail protruding from the medullary cavity was smaller for the ETN-Proximal-Bend (average 540 mm2) compared to the ETN (average 1044 mm2). Also, the maximal distance of the nail protruding from the medullary cavity was smaller for the ETN-Proximal-Bend (average 1.2 mm) compared to the ETN (average 2.7 mm). The differences were statistically significant (p < 0.05) for both the total surface area and the maximal distance measurements. For all bone models, the nail protrusion occurred on the posterior side in the middle third of the tibia. For 12 bones the protrusion was slightly lateral to the centre of the shaft, for seven bones it was centred, and for one bone it was medial to the shaft. The ETN-Proximal-Bend shows a statistical significantly better intramedullary fit with less cortical protrusion than the original ETN. The expected clinical implications of an improved anatomical nail fit are fewer complications with malreduction and malalignments, a lower likelihood for fracture extension and/or new fracture creation during the nail insertion as well as an easier handling for the nail insertion. By utilising computer graphical methods we were able to conduct a quantitative fit assessment between implanted nail and bone geometry in 3D. In addition to the application in implant design, the developed method could potentially be suitable for pre-operative planning enabling the surgeon to choose the most appropriate nail design

In foot and ankle surgery incorrect placement of implants, or inaccuracy in fracture reduction may remain undiscovered with the use of conventional C-arm fluoroscopy. These imperfections are often only recognized on postoperative computer tomography scans. The apparition of three dimensional (3D) mobile Imaging system has allowed to provide an intraoperative control of fracture reduction and implant placement. Three dimensional computer assisted surgery (CAS) has proven to improve accuracy in spine and pelvic surgery. We hypothesized that 3D-based CAS could improve accuracy in foot and ankle surgery. The purpose of our study was to evaluate the feasibility and utility of a multi-dimensional surgical imaging platform with intra-operative three dimensional imaging and/or CAS in a broad array of foot and ankle traumatic and orthopaedic surgery. Cohort study of patients where the 3D mobile imaging system was used for intraoperative 3D imaging or 3D-based CAS in foot and ankle surgery. The imaging system used was the O-arm Surgical Imaging System and the navigation system was the Medtronic's StealthStation. Surgical procedures were performed according to standard protocols. In case of fractures, image acquisition was performed after reduction of the fracture. In cases of 3D-based CAS, image acquisition was performed at the surgical step before implants placement. At the end of the operations, an intraoperative 3D scan was made. We used the O-arm Surgical Imaging system in 11 patients: intraoperative 3D scans were performed in 3 cases of percutaneus fixation of distal tibio-fibular syndesmotic disruptions; in 2 of the cases, revision of reduction and/or implant placement were needed after the intraoperative 3D scan. Three dimensional CAS was used in 10 cases: 2 open reduction and internal fixation (ORIF) of the calcaneum, 1 subtalar fusion, 2 ankle arthrodesis, 1 retrograde drilling of an osteochondral lesion of the talus, 1 Charcot diabetic reconstruction foot and 1 intramedullary screw fixation of a fifth metatarsal fracture. The guidance was used essentially for screw placement, except in the retrograde drilling of an osteochondral lesion where the guidance was used to navigate the drill tool. Intraoperative 3D imaging showed a good accuracy in implant placement with no need to revision of implants. We report a preliminary case series with use of the O-arm Surgical Imaging System in the field of foot and ankle surgery. This system has been used either as intraoperative 3D imaging control or for 3D-based CAS. In our series, the 3D computer assisted navigation has been very useful in the placement of implants and has shown that guidance of implants is feasible in foot and ankle surgery. Intraoperative 3D imaging could confirm the accuracy of the system as no revisions were needed. Using the O-arm as intraoperative 3D imaging was also beneficial because it allowed todemonstrate intraoperative malreduction or malposition of implants (which were repositioned immediately). Intraoperative 3D imaging system showed very promising preliminary results in foot and ankle surgery. There is no doubt that intraoperative use of 3D imaging will become a standard of care. The exact indications need however to be defined with further studies