Purpose of the study: We describe a surgery navigation system based on virtual fluoroscopy images established with a 3D optic localizer. The purpose of this work was to check the accuracy of the system for posterior spinal implants in comparison with conventional surgery. Duration of radiation and duration of surgery were compared. Material and methods: A 3D optic localizer was used to monitor the position of the instruments in the operative field, as well as the fluoroscopy receptor. The surgeon took two views, ap and lateral, with a total exposure of two seconds. The C arm was then removed. After image correction, the ap and lateral views were displayed on the work station screen where the computer superimposed to tools on each image. Twenty osteosynthesis procedures for implantation of pedicular screws via a posterior approach to the thoracolumbar spine were performed with this virtual fluoroscopy technique (20 patients, 68 screws). During the same study period, twenty other procedures were performed with the conventional technique (ap and lateral x-ray with the C-arm after drilling the pedicle, 20 patients, 72 screws). The position of the spinal implants was compared between the two series on the ap and lateral views and postoperative CT. Similarly time of exposure to x-rays and duration of the surgical procedure were recorded. Results: The rate of strictly intrapedicular implantation was less than 8% (5/68 screws) in the virtual fluoroscopy series versus 15% (11/72 screws) in the conventional series. Time of exposure to radiation was significantly lower in the virtual fluoroscopy series with a 1 to 3 improvement (3.5 s versus 11.5 s on average) over the conventional method. With training, this method is not more time consuming (10 min per screw for the conventional method versus 11.25 min for virtual fluoroscopy). Discussion and conclusion: Compared with conventional fluoroscopy, the virtual technique enables real time navigation while significantly reducing the dose of radiation, both for the patient and the surgery team. There are two types of advantages of virtual fluoroscopy over CT-based systems: first virtual fluoroscopy is immediately available without specific preoperative imaging and secondly it provides real non-magnified images acquired once during the procedure, after which the C-arm is removed. 3D virtual fluoroscopy is probably the next step but requires further experience

Introduction. The direct anterior approach (DAA) for total hip arthroplasty continues to gain popularity. Consequently, more procedures are being performed with the patient supine. The approach often utilizes a special leg positioner to assist with femoral exposure. Although the supine position may seem to allow for a more reproducible pelvic position at the time of cup implantation, there is limited evidence as to the effects on pelvic tilt with such leg positioners. Furthermore, the DAA has led to increased popularity of specific softwares, ie. Radlink or JointPoint, that facilitate the intra-op analysis of component position from fluoroscopy images. The aim of this study was to assess the difference in cup orientation measurements between intra-op fluoroscopy and post-op CT. Methods. A consecutive series of 48 DAA THAs were performed by a single surgeon in June/July 2018. All patients received OPS. TM. pre-operative planning (Corin, UK), and the cases were performed with the patient supine on the operating table with the PURIST leg positioning system (IOT, Texas, USA). To account for variation in pelvic tilt on the table, a fluoroscopy image of the hemi-pelvis was taken prior to cup impaction, and the c-arm rotated to match the shape of the obturator foramen on the supine AP Xray. The final cup was then imaged using fluoroscopy, and the radiographic cup orientation measured manually using Radlink GPS software (Radlink, California, USA). Post-operatively, each patient received a low dose CT scan to measure the radiographic cup orientation in reference to the supine coronal plane. Results. Mean cup orientation from intra-op fluoro was 38° inclination (32° to 43°) and 24° anteversion (20° to 28°). Mean cup orientation from post-op CT was 40° inclination (29° to 47°) and 30° anteversion (22° to 38°). Cups were, on average, 6° more anteverted and 2° more inclined on post-op CT than intra-op. These differences were statistically significant, p<0.001. All 48 cups were more anteverted on CT than intra-op. There was no statistical difference between pre- and post-op supine pelvic tilt (4.1° and 5.1° respectively, p = 0.41). Discussion. We found significant differences in cup orientation measurements performed from intra-op fluoro to those from post-op CT. This is an important finding given the attempts to adjust for pelvic tilt during the procedure. We theorise two sources of error contributing to the measurement differences. Firstly, the under-compensation for the anterior pelvic tilt on the table. Although the c-arm was rotated to match the obturator foramen from the pre-op imaging, we believe the manual matching technique utilised in the Radlink software carries large potential errors. This would have consistently led to an under-appreciation of the adjustment angle required. Secondly, the manual nature of defining the cup ellipse on the fluoro image has previously been shown to underestimate the degree of cup anteversion. These combined errors would have consistently led to the under-measurement of cup anteversion seen intra-operatively. In conclusion, we highlight the risk of over-anteversion of the acetabular cup when using 2D measurements, given the manual inputs required to determine a result

Aims. The use of fluoroscopy in orthopaedic surgery creates risk of radiation exposure to surgeons. Appropriate personal protective equipment (PPE) can help mitigate this. The primary aim of this study was to assess if current radiation protection in orthopaedic trauma is safe. The secondary aims were to describe normative data of radiation exposure during common orthopaedic procedures, evaluate ways to improve any deficits in protection, and validate the use of electronic personal dosimeters (EPDs) in assessing radiation dose in orthopaedic surgery. Methods. Radiation exposure to surgeons during common orthopaedic trauma operations was prospectively assessed using EPDs and thermoluminescent dosimeters (TLDs). Normative data for each operation type were calculated and compared to recommended guidelines. Results. Current PPE appears to mitigate more than 90% of ionizing radiation in orthopaedic fluoroscopic procedures. There is a higher exposure to the inner thigh during seated procedures. EPDs provided results for individual procedures. Conclusion. PPE currently used by surgeons in orthopaedic trauma theatre adequately reduces radiation exposure to below recommended levels. Normative data per trauma case show specific anatomical areas of higher exposure, which may benefit from enhanced radiation protection. EPDs can be used to assess real-time radiation exposure in orthopaedic surgery. There may be a role in future medical wearables for orthopaedic surgeons. Cite this article: Bone Jt Open 2022;3(11):907–912

INTRODUCTION:. Stationary fluoroscopy has been a viable resource for determining in vivo knee kinematics, but limitations have restricted the use of this technology. Patients can only perform certain normal daily living activities while using stationary fluoroscopy and must conduct the activities at speeds that are slower than normal to avoid ghosting of the images. More recently, a Mobile Tracking Fluoroscopic (MTF) unit has been developed that can track patients in real-time as he/she performs various activities at normal speeds (Figure 1). Therefore, the objective of this study was to compare in vivo kinematics for patient's evaluated using stationary and mobile fluoroscopy to determine potential advantages and disadvantages for use of these technologies. METHODS:. The MTF is a unique mobile robot that can acquire real-time x-ray records of hip, knee, or ankle joint motion while a subject walks/manoeuvres naturally within a laboratory floor area. By virtue of its mechanizations, test protocols can involve many types of manoeuvres such as chair rises, stair climbing/descending, ramp crossing, walking, etc. Because the subjects are performing such actions naturally, the resulting fluoroscope images reflect the full functionality of their musculoskeletal anatomy. Patients in the study were initially fluoroscoped using a stationary unit and then using the MTF unit. RESULTS:. Initially, patients were requested to perform gait, stair-rise, stair descent, chair-rise and a deep knee bend under stationary fluoroscopy. Unfortunately, patients were not able to perform most of these activities, under normal conditions, using a stationary fluoroscopy unit. Therefore, only a deep knee bend, step-up and chair-rise were viable activities, but again, performed at slower than normal speeds. While using the MTF unit, all five activities were easily performed and patients received 50% less radiation due to the fact that five activities using the MTF required significantly less time than three activities using a stationary fluoroscopy unit (Figure 2). Also, walking up and down a ramp was also included in the protocol for the MTF analyses, leading to the inclusion of two new activities, not previously evaluated using stationary fluoroscopy. Interestingly, the kinematics for the patients using a stationary fluoroscopy unit produced less overall motion than compared to the MTF analysis, probably due to the slower speed required to perform the activities. While using the MTF unit, kinematic findings such as anteroposterior sliding and reverse axial rotation were more pronounced during each activity. DISCUSSION:. This study has revealed that there are distinct advantages for using a MTF unit, compared to a stationary unit. Patient exposure to radiation was significantly reduced and they were able to perform each activity quicker, while only one trial was required for each activity. Patients were able to perform multiple activities at normal speeds and these analyses seemed to produce more overall femorotibial motion than those assessed using a stationary fluoroscopy unit. Also, ghosting of the images, seen when using a stationary fluoroscopy unit were not evident when using the MTF. Future analyses with the MTF will involve more challenging activities, such as stop and start and sequential motion patterns

Utilization of C-arm fluoroscopy during direct anterior total hip arthroplasty (THA) is disruptive and potentially increases the risks of patient infection and cumulative surgeon radiation exposure. This pilot study evaluated changes in surgeon C-arm utilization during an initial 10 cases of direct anterior THA in which an imageless computer-assisted navigation device was introduced. This retrospective study includes data from 20 direct anterior THA cases performed by two orthopaedic surgeons (BC; SRE) in which an imageless computer-assisted navigation device was utilized (Intellijoint HIP®; Intellijoint Surgical, Waterloo, ON, Canada). Total C-arm image count was recorded in each case, and cases were grouped in sets of 5 for each surgeon. The mean C-arm image count was calculated for each surgeon, and combined C-arm image counts were calculated for the study cohort. Student's t-tests were used to assess differences. The use of intraoperative C-arm fluoroscopy decreased from a mean of 9.4 images (standard deviation [SD]: 8.6; Range: 3 – 23) to a mean of 2 images (SD: 2.9; Range: 0 – 7) for surgeon BC (P=0.10) and decreased from a mean of 10.75 images (SD: 1.2; range 9 – 12) to a mean of 6.7 images (SD: 8.3; range: 0 – 16) for surgeon SRE (P=0.36). Combined, an overall decrease in intraoperative C-arm image count from a mean of 11.3 images (SD: 6.9; range: 6 – 23) to a mean of 3.7 images (SD: 3.9; range: 0 – 8.5) was observed in the study cohort (P=0.06). The adoption of imageless computer-assisted navigation in direct anterior THA may reduce the magnitude of intraoperative C-arm fluoroscopy utilization; however further analysis is required

During a periacetabular osteotomy (PAO), intra-operative assessment of correction of acetabular parameters is typically performed using fluoroscopy of the hip, a technique that has not been shown to produce predictable measurements. Furthermore, paralysing agents are used in order to facilitate dissection and fragment mobilization. The effect of paralysing agents on spino-pelvic posture is yet to be investigated. This study aims to: 1. Compare the reliability of intra-operative x-rays versus hip fluoroscopy in the assessment of acetabular fragment correction and 2. Evaluate the effect of changes in spino-pelvic alignment on the assessment of acetabular correction. An IRB approved, retrospective review of all patients who underwent a PAO at our institution between 2006–2018 was performed. Patient demographic data was collected and all available imaging studies were retrieved. Patients were excluded if there was no available to review intra-operative AP pelvis x-ray or intra-operative fluoroscopic PA image of the hip. Using a validated hip analysis software (Hip2Norm), the lateral center edge angle (LCEA) and acetabular index (AI) of plain radiographs were measured. The sacro-femoral-pubic angle (SFP), along with the LCEA and AI of the fluoroscopic image were measured using ImageJ. A oneway ANOVA was used to detect differences between measured parameters in the intra-operative x-ray, the post-operative x-ray and the fluoroscopic image. A total of 93 patients were identified. 26 patients were excluded due to missing data. The mean LCEA in the post-operative, intra-operative, and fluoroscopic groups were as follows: 33.67° (range 5.3° to 52.4°), 30.71°(range 9° to 55.6°), and 29.23°(range 12.4° to 51.4°) respectively. The mean AI in the post-operative, intra-operative, and fluoroscopic groups were as follows: −0.65° (range −18.10° to 27.30°), 0.35°(range −16.10° to 17.20°), and 5.54°(range −11.66° to 27.83°) respectively. When comparing intra-operative to post-operative plain radiographs, there was no statistically significant difference in AI (ΔAI −1±1.29° p=0.71) or LCEA (ΔLCEA 2.95±1.38° p=0.09). When comparing fluoroscopy to post-operative plain radiographs, there was a statistically significant difference in AI (ΔAI −6.21±1.29° p < 0 .0001) as well as LCEA (ΔLCEA 4.44±1.38° p < 0 .0001). Statistical analysis revealed no influence of demographics (age, BMI, gender), on acetabular correction parameters. The mean SPF angles measured from intra-operative and post-operative x-rays were 69.32±5.11° and 70.45±5.52°. There was a statistically significant difference between these 2 measurements with a ΔSFP of 1.03° (p < 0 .0001). The results of our study show that the use of intra-operative x-ray for the assessment of LCEA and AI is more reliable than fluoroscopic images. Further, we found a difference in SFP angle, which offers an indirect assessment of pelvic tilt, between the intra-operative and the post-operative plain x-rays. This suggests that there are changes in pelvic tilt during the surgery, which can be attributed to either patient positioning or changes in spino-pelvic posture secondary to the paralysing agents used by the anesthetists. The use of intra-operative x-rays as well as the effect of paralysing agents on spino-pelvic alignment should be considered by surgeons performing PAO's

Study purpose and background. Kinematic variables have been identified as potential biomarkers for low back pain patients; however, an in-depth comparison between chronic (n=22), acute (n=15), and healthy controls (n=136) has not been done. This retrospective data analysis compared intervertebral lumbar motion parameters, angular range of motion, translation, maximum disc height, motion share inequality (MSI) and variability (MSV), and laxity, between these groups. Methods and results. Kinematic parameters were determined using video tracking techniques utilising quantitative fluoroscopy (QF), during both weight-bearing and recumbent controlled sagittal bending tasks. Data was analysed for normality, and appropriate statistical tests were applied to determine differences between groups. There were no significant differences between the groups for age, height, weight and sex. Whilst few differences were found between acute and healthy groups, differences were shown between both chronic and healthy, and acute and chronic groups for all six parameters. Of particular note were examples of differences in the motion share parameters between the acute and chronic populations, with an increased MSI in the chronic group during recumbent flexion, and MSV during recumbent extension, and inversely an increase in MSV in the acute group during weight-bearing flexion. Conclusion. Analysis of intervertebral lumbar motion provides valuable insights into kinematic differences between chronic, acute, and healthy control populations. These findings suggest that there is variation between the groups which is knowledge that may benefit management strategies. Further exploration of the time varying data is warranted to explore how such differences may relate to the motion share inequalities and variability shown. Conflicts of Interest. No conflicts of interest. Sources of Funding. No funding obtained

Consecutive case series. To evaluate the efficacy of a strict stepwise radioanatomical procedure protocol in avoiding neurological complications through tool malplacement in fluoroscopy guided percutaneous procedures of the thoracic spine. Fluoroscopy guided percutaneous access to thoracic vertebral bodies is technically demanding. There is a trend towards computed tomography (CT) guidance on grounds of perceived lesser risk of spinal canal instrument malplacement. CT is however not always readily accessible and a safe technique for fluoroscopy guided procedures therefore desirable. 350 consecutive fluoroscopy guided percutaneous procedures (biopsy, vertebroplasty or kyphoplasty) covering all thoracic vertebral levels T1-T12 were performed according to a strict stepwise radioanatomical protocol. The crucial step of the protocol was not to advance the tool beyond the anterior-posterior (ap) projection of the medial pedicle wall until the tip of the instrument had been verified to have reached the posterior vertebral cortex in the lateral projection. The neurological status of patients was assessed through clinical examination prior to, immediately after the procedure and before discharge. Percutaneous instrument placement in the targeted thoracic vertebral body was achieved in all cases and the stepwise radioanatomical protocol was followed in all cases. There was no case of neurological deterioration in the case series. Conclusion: Attention to radiographic landmarks, specifically not crossing the ap projection of the medial pedicle cortex prior to reaching the posterior vertebral wall in the lateral projection, allows neurologically safe performance of fluoroscopy guided percutaneous procedures of the thoracic spine. This simple protocol is particularly useful when access to CT is limited

An accurate geometrical three-dimensional (3D) model of human bone is required in many medical procedures including Total Knee Arthroplasty (TKA) and computer-assisted surgical navigation. Segmentation of Computed Tomography (CT) datasets is commonly used to obtain such models. However, such a method is expensive and time consuming. We herein propose a novel method for patient specific bone model reconstruction using standard x-ray fluoroscopy, a cheaper and widely available imaging alternative. Fluoroscopic images are taken at multiple arbitrary viewpoints to provide sufficient information for bone reconstruction. The viewpoints can be obtained by either rotating the imaging source and detector or the patient’s limb of interest. The bone’s pose within the radiological scene in each of the captured images can be estimated by tracking a set of metallic calibration markers within a calibration target, rigidly attached to the limb of interest. Having acquired the required calibration data, a complex iterative scheme is executed to optimize a statistical bone atlas of the bone of interest and the relative pose between the bone and the calibration target. In order to verify our method, we performed a cadaveric study. A set of rigidly attached fiducial markers were attached to a cadaveric leg. The leg was imaged using x-ray fluoroscopy while being rotated axially to provide us with the images required for bone model reconstruction. Distal femur and proximal tibia bone models were reconstructed from the fluoroscopy images. Furthermore, the leg was CT-scanned and segmented to provide us with the ground-truth required for reconstruction accuracy assessment. Results show the adequacy of the proposed method for surgical applications

2D/3D image registration techniques have supplanted RSA for kinematic analysis as they are faster, non-invasive and enable pre and post op studies. Improved algorithms have solved the problem of accuracy of out-of-plane translation [1,2]. The aim of this study is to apply these new algorithms to the post op case. In this study, Computer-Aided Design (CAD) models of the femoral and tibial components were registered to fluoroscopic images. The prosthesis (RBK knee, Global Orthopaedic Technology), was implanted into a sawbones knee. A perspex cage held the knee static while simultaneous fluoroscopy and dual X-rays were taken from 0 and 90 degrees flexion. Translations orthogonal to the fluoroscope were simulated by sliding the cage at 5 mm intervals. The CAD models were then registered with the fluoroscopy frames. Registration information was used to perform kinematic analysis. This study has demonstrated greater accuracy for the post operative than pre-operative registration applications. The standard deviation of error for flexion/extension was 0.23° with respect to RSA. The average standard deviation of error for out-of-plane rotations (i.e. abduction/adduction and internal/external rotation) was 0.46°. Translations such as anterior-posterior drawer, compression/distraction and medio-lateral shift had errors of 0.16 mm, 0.17 mm and 0.59 mm, respectively. Both the registration and kinematic analysis accuracies for prosthesis components were superior to those for registration of natural (e.g. cadaver) bones [1]. While rotation accuracies improved about 0.1°, improvement in translation was substantial. In particular, medio-lateral translation accuracy has improved from 1 mm (in our previous study) to 0.59 mm, which is promising. It is worth noting that the best reported accuracy for out-of-plane or medio-lateral translation has been 1.03 mm [2]. Hence, this technique is competitive with other 3D/2D registration methods reported in the literature. Our experiments show that our 3D CAD to 2D fluoroscopy registration method is sufficiently accurate to produce confident and reliable analysis of prospective kinematics studies

Introduction: The use of mini C-arm systems has become established in hand surgery. Potential advantages of the mini C-arm include decreased radiation exposure by reducing screening time, increased distance from the beam, tighter beam collimation and surgeon control of the C-arm. Little has been written in the literature regarding their use in foot and ankle surgery. Aims: To compare the radiation dose and screening times delivered by the mini C-arm with standard fluoroscopy in elective foot and ankle surgical procedures. A secondary objective was to quantify the cost of both techniques. Patients and methods: We prospectively studied 137 patients who underwent fluoroscopic screening during various elective foot and ankle procedures. Of these 72 were screened using standard fluoroscopy and the remaining 55 using the mini C-arm. During each procedure screening time and radiation dose were prospectively recorded. The Dose Area Product (DAP) meters on both machines for the determination of radiation exposure and scatter to the operating theatre and staff were used. A cost benefit analysis for radiographer attendance and theatre delay was calculated. Results: The mean DAP for standard fluoroscopy was 7.43 CGycm2 (sd 9.41) whereas with the mini C-arm it was 3.46 CGycm2 (sd 3.51). There was a statistically significant reduction in the DAP (P = 0.0013). Mean screening time was 13 seconds (SD 14.7) with standard fluoroscopy and 14.5 seconds (SD 18.1) with the mini C-arm. No statistically significant difference was found between screening times. (p = 0.987). The potential total saving of the mini c-arm for 137 procedures was £4086. Conclusion: We recommend the use of the mini C-arm in foot and ankle surgery as it reduces radiation exposure and cost when compared to standard fluoroscopy. We acknowledge that there is a learning curve for surgeons to minimise screening time

The outcome following arthroscopic anterior cruciate (ACL) reconstruction is dependant on a combination of surgical and non-surgical factors. Technical error is the commonest cause for graft failure, with poor tunnel placement accounting for over 80% of those errors. A routine audit of femoral and tibial tunnel positions following single bundle hamstring arthroscopic ACL reconstruction identified apparent inconsistent positioning of the tibial tunnel in the sagittal plane. Intra-operative fluoroscopy was therefore introduced (when available) to verify tibial guide wire position prior to tunnel reaming. This paper reports a comparison of tibial interference screw position measured on post-operative radiographs with known tunnel position as shown on intra-operative fluoroscopic images in 20 patients undergoing routine primary ACL reconstruction between January and June 2009. Surgery took a mean of 5 minutes longer when intra-operative fluoroscopy was used. In 3/20 patients, fluoroscopy led to re-positioning of the tibial guide wire prior to tunnel reaming. The mean tibial tunnel position as indicated by the tunnel reamer was 41 +/− 2.7 % of the total plateau depth (range 37% to 47%). The mean position projected from the tibial screw on post operative radiographs was 46 +/− 9.2% (range 38% to 76%). A paired t-test showed a significant difference (p = 0.022) between true tunnel position and tibial screw position. 6/20 patients had post operative screw positions that were > 5% more posterior than the known position of the tibial tunnel. The position of the tunnel should be measured at its mid-point where this is evident. On most early radiographic images, the margins of the tunnel are not clear and therefore a line projected from the centre of the screw is used. This audit demonstrates the potential inaccuracy associated with this

Aim. The purpose of this study was to establish the diagnostic utility and spectrum of fluoroscopy guided percutaneous transpedicular biopsies of the thoraco-lumbar spine performed at our institution and to review some aspects regarding the diagnosis of spinal tuberculosis (TB). Methods. A retrospective study was performed on a consecutive series of 48 patients who underwent fluoroscopy guided percutaneous transpedicular biopsies of the spine performed at our institution. Biopsy specimens were sent for microscopy, culture and sensitivity (MC&S) as well as for TB microscopy, culture and polymerase chain reaction (PCR) and for histology. Results. There were 26 females and 22 males. The ages ranged from 23 to 79 years with a mean of 47 years. Fifteen biopsies were performed in the thoracic spine and 33 in the lumbar spine. A diagnosis was established in 83% of patients. The most common diagnosis, made in 58% of cases, was TB. The second most common diagnosis was metastatic disease, diagnosed in 15%. In 3 patients a diagnosis was made of concomitant TB and metastatic adenocarcinoma. No complications were encountered. Regarding the diagnosis of spinal TB we found that microscopy for alcohol and acid fast bacilli has a very low yield, with TB cultures, PCR and histology delivering a higher yield. TB PCR was also found to be positive in some cases where the TB cultures were negative which had implications for our institution's protocol regarding performance of TB PCR testing. Conclusion. Fluoroscopy guided percutaneous transpedicular biopsies of the thoraco-lumbar spine is a safe and effective tool in the diagnostic work-up of a patient with a spinal lesion of uncertain cause. We recommend that in all cases specimens should be send for histology and bacteriological studies and if spinal TB is suspected samples should be sent for histology, MC&S and PCR. NO DISCLOSURES

Background. Hip fractures affect 1.6 million people globally per annum, associated with significant morbidity and mortality. A large proportion are extracapsular neck of femur fractures, treated with the dynamic hip screw (DHS). Mechanical failure due to cut-out is seen in up to 7% of DHS implants. The most important predictor of cut-out is the tip-apex distance (TAD), a numerical value of the lag screw”s position in the femoral head. This distance is determined by the psychomotor skills of the surgeon guided by fluoroscopic imaging in theatre. With the current state of surgical training, it is harder for junior trainees to gain exposure to these operations, resulting in reduced practice. Additionally, methods of simulation using workshop bones do not utilise the imaging component due to the associated radiation risks. We present a digital fluoroscopy software, FluoroSim, a realistic, affordable, and accessible fluoroscopic simulation tool that can be used with workshop bones to simulate the first step of the DHS procedure. Additionally, we present the first round of accuracy tests with this software. Methods. The software was developed at the Royal National Orthopaedic Hospital, London, England. Two orthogonally placed cameras were used to track two coloured markers attached to a DHS guide-wire. Affine transformation matrices were used in both the anterior-posterior (AP) and cross table lateral (CTL) planes to match three points from the camera image of the workshop bone to three points on a pre-loaded hip radiograph. The two centre points of each marker were identified with image processing algorithms and utilised to digitally produce a line representing the guide-wire on the two radiographs. To test the accuracy of the system, the software generated 3D guide-wire apex distance (GAD) (from the tip of the guide-wire to a marker at the centre of calibration) was compared to the same distance measured with a digital calliper (MGAD). In addition, the same accuracy value was determined in a simulation scenario, from 406 attempts by 67 medical students. Results. The median absolute inaccuracy of FluoroSim with 270 measurements was 3.35mm (IQR = [1.15mm, 6.53mm]). The absolute inaccuracy showed a graded increase the further away the tip of the guide-wire was from the centre of calibration; MGAD ≤10mm, median absolute inaccuracy = 1.53mm; MGAD 10mm<x≤20mm, median absolute inaccuracy = 4.97mm; MGAD >20mm, median absolute inaccuracy = 7.23mm. Comparison between all three groups reached significance (p < 0.001). In a simulation scenario with medical students, FluoroSim had a significantly greater median absolute inaccuracy of 4.79mm compared to the testing scenario (p < 0.001). Conclusion. FluoroSim is a safe and inexpensive digital imaging adjunct to workshop bones simulation. To our knowledge this technology has not been explored in the context of DHS simulation, and has the potential to be extended to other orthopaedic procedures

Background. Dynamic measurement of continuous intervertebral motion in low back pain (LBP) research in-vivo is developing. Lumbar motion parameters with the features of biomarkers are emerging and show promise for advancing understanding of personalised biometrics of LBP. However, measurement of changes over time inevitably involve error, due to subjects' natural variation and/or variation in the measurement process. Thus, intra-subject repeatability of parameters to measure changes over time should be established. Methods. Seven lumbar spine motion parameters, measured using quantitative fluoroscopy (QF), were assessed for intra-subject repeatability: Intervertebral range-of-motion (IV-RoM), laxity, motion sharing inequality (MSI), motion sharing variability (MSV), flexion translation and flexion disc height. Intra-subject reliability (ICC) and minimal detectable change (MDC95) of baseline and 6-week follow-up measurements were obtained for 109 healthy volunteers (54 coronal and 55 sagittal). Results. Reliability was substantial to excellent for repeated measurements of IV-RoM, laxity, flexion translation and disc height during recumbent passive motion (ICC:0.69–0.95) and during active weight-bearing motion (ICC:0.64–0.92). MSI was moderate to excellent across both positions (ICC:0.43–0.91). The reliability of MSV was generally poorer for both positions (0.14–0.65). For all parameters, measurement error exceeded 42%. Conclusion. Recumbent IV-RoM, laxity and disc height demonstrated the best repeatability at 6-weeks suggesting they may be better outcome moderators in clinical studies than other variables. However measurement errors for all parameters were higher than the minimal changes of interest. These results are limited to healthy controls and should be regarded as reference values. Similar studies in CNSLBP patients are required. No conflicts of interest. Sources of Funding: Dr Rebecca Hemming received a Seedcorn Bursary from the Cardiff Institute of Tissue Engineering and Repair (CITER) and Professor Alan Breen received a project grant from the European Chiropractors Union Research Fund (ECURF)

Purpose. Measurements of patellar kinematics are essential to investigate the link between anterior knee pain following knee arthroplasty and patellar maltracking. A major challenge in studying the patellofemoral (PF) joint postoperatively is that the patellar component is only partially visible in the sagittal and close-to-sagittal radiographs. The narrow angular distance between these radiographs makes the application of conventional bi-planar fluoroscopy impossible. In this study a methodology has been introduced and validated for accurate estimation of the 3D kinematics of the PF joint post-arthroplasty using a novel multi-planar fluoroscopy approach. Method. An optoelectronic camera (Optotrak Certus) was used to track the motion of an ISO-C fluoroscopy C-arm (Siemens Siremobil) using two sets of markers attached to the X-ray source and detector housings. The C-arm was used in the Digital Radiography (DR) mode, which resembles an ordinary X-ray fluoroscopy image. A previously-developed technique (Cho et al., 2005; Daly et al., 2008) was adapted to find the geometric parameters of the imaging system. Thirty-eight DRs of the calibration phantom were obtained for the 190 of rotation of the C-arm at 5 rotational increments while data from motion markers were recorded continuously at a frequency of 100 Hz. A total knee replacement prosthesis was implanted on an artificial bone model of the knee, and the implant components and bones were rigidly fixed in place using a urethane rigid foam. For the purpose of validation, positions of the implant components were determined using a coordinate measuring machine (CMM). Sagittal and obliquely sagittal radiographs of the model were taken where the patellar component was most visible. For each DR the geometric parameters of the system were interpolated based on the location of the motion markers. The exact location of the projection was then determined in 3D space. JointTrack Bi-plane software (Dr. Scott Banks, University of Florida, Gainesville) was used to conduct 2D-3D registration between the radiographs and the reverse-engineered models of the implant components. Results of the registration were directly compared to the ground-truth obtained from the CMM to calculate the accuracies. Results. The accuracies for the PF were found to be 0.48 mm and 1.32 for position and orientation of the components. For the tibiofemoral joint these values were found to be 0.89 mm and 1.43, respectively. Conclusion. The multi-planar method can be used to assess the sequential kinematics of the patellofemoral and tibiofemoral joints including the mediolateral translation and tilt of the patellar component, which are obscured in standard 2D sagittal measurements and are not possible using the traditional bi-planar setup. A limitation is that it can only be used for static imaging of the joint. It has the advantage of a relatively low radiation dose. This methodology can be used to investigate the relationship between maltracking of the patella and anterior knee pain as well as other postoperative complications

Introduction: Image based navigation is able to increase precision and reduce intraoperative radiation time in drilling procedures in orthopeadic trauma indications. Due to specific anatomic conditions and necessary adequate fluoroscopic visualizing, specific indications need intraoperative 3-D fluoroscopy based navigation modalities. This kind of navigation has already been successfully used in several orthopaedic interventions. The complex anatomic structure of the scaphoid, the suggested minimal invasiveness and misplacement rates of the screws make 2-D based fluoroscopic navigation impossible. Missing options for a stable reference marker fixation at the scaphoid or carpus did not allow an intraoperative registration for the navigation. We report about the development of an adequate non invasive fixation technique of the reference marker for navigated interventions and the first implementation of 3-D fluoroscopy based scaphoid screws. Materials and method: Fixation of the reference marker was achieved by immobilisation of the complete hand and forearm in maximum dorsal extension of the wrist. We used a completely new developed radiolucent hand fixation device (HFD) fixed nonivasively to the carpus and a conventional navigation system (Brainlab, Germany) in combination with 3-D fluoroscopic imaging (Iso-C, Siemens, Germany). Tests were done on 10 intact specimen and the process included the initial drilling and final placement of an osteosynthetic screw. Postoperative placement was controlled with a 3-D scan. Results concerning a defined optimal screw positioning and drill failures attempts were done by another independent surgeon. Results: All 3-D scans were done without complications. The multiplanar reconstructions allowed a proper visualisation of the scaphoid in all cases. No additional movement of the fixed extremity occurred during the operation. No registration failures were detected. An optimally defined screw placement in the scaphoid was achieved in 9 cases. Two repeated drill attempts were necessary in one case, another case needed three drill attempts. The scaphoid was never perforated. Discussion: Our development of a new immobilizing device for the complete hand and forearm allows proper use of 3-D fluoroscopy based navigation at the scaphoid including a placement of an osteosynthetic screw. Further movements of the hand or fingers are intraoperatively only possible after the definite drill placement has been performed. The 3-D imaging modality allows a direct control of the reduction and screw placement intraoperatively. Our tests did not include simulated fracture conditions, a general use of our new technique can now only be implemented to non displaced fracture types, while clinical and further laboratory tests have to improve our findings for all types of scaphoid fractures

Intra-operative 3-D fluoroscopy has limitations, including low resolution images, little soft tissue information and small working volume. Fusion of 3D data sets (MRI/ CT) had been developed in pre-operative planners. We employed the same principle and developed a new technique of navigation with fused images of pre-operative MRI/CT and intra-operative 3D fluoroscopy. Pre-op CT/MRI in DICOM was imported to the Stryker Leibinger Spine 3-D and segmentation of the intended bone performed. Patient tracker was mounted and 3-D fluoroscopy performed using Siemens ISO-C 3D. Fusion of CT/MRI with 3D fluoroscopy was performed using “surface matching image correlation” and this automatically registered the bone with MRI/CT. The fused images were then ready for 3D navigation procedures. Nine patients were included in the series. There were eight fracture cases and seven performed with fused CT and 3-D fluoroscopy (two PCL avulsion fractures, two tibial plateau fractures, one femoral condyle fracture and three pelvic-acetabular fractures). Total of twenty-three screws had been inserted without complication. One tibial plateau fracture fixation and one core decompression for avascular necrosis of femoral head were performed with fused MRI to 3D fluoroscopy. In conclusion, intra-operative 3-D navigated procedures with fused pre-operative MRI/CT and intra-operative 3-D fluoroscopy were all successful with (1) extended working volume (2) higher resolution images (3) more soft tissue information. We foresee more applications of this new technique in other areas of computer aided surgery

To better understand the functional effects of pathologies, a system to capture accurate real-time 3D imaging of functional activities, without the limitations of RSA, is desirable. To address this problem, a new registration algorithm was developed to automatically determine the 3D kinematics of the knee using commonly available imaging modalities. To evaluate this new registration algorithm, three cadaveric knees were implanted with 1mm tantalum beads to act as gold standard fiducial markers. The knees were flexed between 0 and 90° and fluoroscopy data was captured at a rate of 25 frames/sec and a resolution of 0.5 mm/pixel (Axiom Artis MP). “Pin-cushion” distortion and beam spreading were accounted for. CT data was captured using a Toshiba Aquillon 16 using bone and soft tissue algorithms. For every frame of the fluoroscopy data, the 3D femur and tibia data was individually registered to the fluoroscopy images using the new algorithm. This position data was then used to generate a kinematic 3D model. Similar fluoroscopy-to-CT registration techniques have been proposed for stationary image-guided surgery applications. The majority of these techniques use fluoroscopy images projected onto at least two different planes (with some systems using as many as 18 planes). Other techniques have been proposed that use a single-plane but require stochastic optimization procedures that perform in the order of 500 iterations to find the optimal 3-D registration. The reported average target registration errors (TREs) of these systems range from 0.5–1.2 mm. The newly developed registration technique requires only a single-plane fluoroscopy image and uses a novel gradient-descent optimization strategy that converges to the optimal 3-D position within 20–30 iterations. Preliminary results demonstrate that the performance of the new registration algorithm is able to align the bones of the knee with an average TRE of 0.57 mm. Up to 7 degrees of concurrent axial rotation was observed during flexion of the knees to 90°. The new registration algorithm developed for the project is capable of automatically determining the 3D kinematics of a knee joint using only single-plane fluoroscopy data. The new algorithm requires approximately one-tenth the number of iterations to find the optimal registration position when compared with existing single-plane techniques. Once it is established in vivo that this image registration technique has the accuracy of RSA, this method will permit real-time kinematic studies without tantalum beads. This will enable prospective longitudinal and controlled studies of reconstruction surgery, and conservative management of joint pathologies

Purpose and background. Static plain radiographs at the end of uncontrolled bending are the current standard of care for measuring translatory slip in back pain patients. Quantitative fluoroscopy systems (QF) that employ standardised bending protocols have been found to improve precision and reduce dose, but comparative data are lacking. We compared 4 QF methods with static radiographs in a control population, calculating ranges, population variation and measurement errors over 6 weeks. Methods. Fifty-four healthy controls (F=22, M=23) received passive recumbent and active weight bearing QF screenings during controlled motion, plus still fluoro imaging in neutral, flexion and extension. The translatory slip of all levels from L2-S1 was determined for each condition using bespoke image tracking codes (Matlab) and pooled to provide means and ranges of variation (+/-1.96SD). The pooled measurement error, or minimal detectable change (MDC. 95. ), reflecting the intra subject repeatability over 6 weeks was calculated. Ranges of translation for each level (L2-S1), for each type of motion were also calculated. Results. Static radiographs at the end of uncontrolled flexion gave the greatest variation and the worst repeatability, while QF recumbent passive and active weight bearing motion with flexion recorded during the motion had ¼ less variation and twice the repeatability. For individual levels, L2-3 had significantly higher flexion ranges in controlled motion than uncontrolled motion, whereas the converse was true at L4-5 (P<0.001). Conclusion. Dynamic QF measurement of flexion translatory slip gives ¼ less population variation and half the measurement error of static radiographs when measured in the same participants. No conflicts of interest. No funding obtained