Surgical navigation systems enable surgeons to carry out surgical interventions more accurately and less invasively, by tracking the surgical instruments inside human body with respect to the target anatomy. Currently, optical tracking (OPT) is the gold standard in surgical instrument tracking because of its sub-millimeter accuracy, but is constrained by direct line of sight (LOS) between camera sensors and active or passive markers. Electromagnetic tracking (EMT) is an alternative without the requirement of LOS, but subject to environmental ferromagnetic distortion. An intuitive idea is to integrate respective strengths of them to overcome respective weakness and we aim to develop a tightly-coupled method emphasising the interactive coupled sensor fusion from magnetic and optical tracking data. In order to get real-time position and orientation of surgical instruments in the surgical field, we developed a new tracking system, which is aiming to overcome the constraints of line-of-sight and paired-point interference in surgical environment. The primary contribution of this study is that the LOS and point correspondence problems can be mitigated using the initial measurements of EMT, and in turn the OPT result can provide initial value for non-linear iterative solver of EMT sensing module. We developed an integrated optical and electromagnetic tracker comprised of custom multiple infrared cameras, optical marker, field generator and sensing coils, because the current commercial optical or magnetic tracker typically consists of unchangeable lower level proprietary hardware and firmware. For the instrument-affixed markers, the relative pose between passive optical markers and magnetic coils is calibrated. The pose of magnetic sensing coils calculated by electromagnetic sensing module, can speed up the extraction of fiducial points and the point correspondences due to the reduced search space. Moreover, the magnetic tracking can compensate the missing information when the optical markers are temporarily occluded. For magnetic sensing subsystem comprised of 3-axis transmitters and 3-axis receiving coils, the objective function for nonlinear pose estimator is given by the summation of the square difference between the measured sensing data and theoretical data from the dipole model. Non-linear optimisation is computational intensive and requires initial pose estimation value. Traditionally, the initial value is calculated by equation-based algorithm, which is sensitive to noise. Instead, we get the initial value from the measurement of optical tracking subsystem. The real-time integrated tracking system was validated to have tracking errors about 0.87mm. The proposed interactive and tightly coupled sensor-fusion of magnetic-optical tracking method is efficient and applicable for both general surgeries as well as intracorporeal surgeries

Aims

This study aimed to assess the carbon footprint associated with total hip arthroplasty (THA) in a UK hospital setting, considering various components within the operating theatre. The primary objective was to identify actionable areas for reducing carbon emissions and promoting sustainable orthopaedic practices.

Retained polymethylmethacrylate (PMMA) debris in surgical instrument trays is a rare, but disquieting situation for the arthroplasty surgeon. Although retained debris could be considered to be sterile after autoclaving, there is no peer-reviewed literature to support this assumption. This uncertainty and subsequent fear of contamination from this bioburden often leads to operating room personnel turning over entire surgical tables and opening new surgical instruments, which consumes time and burdens a hospital's sterilization infrastructure. Consequently, the purpose of the current study was to determine if retained, heavily contaminated PMMA in surgical trays could be effectively sterilized through clinically utilized autoclave protocols. MSSA (Xen36, Perkin Elmer) biofilm was grown on identically sized PMMA (Palacos R) coupons for 72-hour duration. Following incubation, coupons were exposed to three commonly used sterilization protocols. Cobalt-Chrome (CC) coupons were included in the same tray, replicating instruments in proximity to retained PMMA. Autoclave protocols included: 1.) Single Instrument Flash protocol: Pre-vac, 270° F, 10 min exposure, 1 min drying, 2.) One Tray OR protocol: Pre-vac, 270° F, 4 min exposure, 1 min drying, and 3.) Standard Post-Operative protocol: Pre-vac, 270° F, 10 min exposure, 60 min drying. Control coupons did not undergo autoclaving. Coupons were then sonicated for 30 minutes in tryptic soy broth and plated to count CFUs. Experiments were performed in quadruplicate. Control coupons showed significant contamination with CFU counts in the range of 10. 6. CFU/mL. CFU counts of zero across all autoclaved PMMA and CC coupons revealed that each protocol was effective in completely eradicating culturable S. aureus, confirming clinical efficacy on orthopaedic cement sterilized in surgical trays. Our findings demonstrate that heavily contaminated PMMA and exposed metal in surgical trays can be effectively sterilized through several autoclaving protocols. Clinicians should feel confident in the efficacy of autoclave protocols in removing bacteria and its associated biofilm from othopaedic materials

An overview about 3D printing technology in orthopaedic applications will be given based on examples. The process from early prototypes to certified implants coming from serial production will be demonstrated also considering relevant surrounding conditions. Today's focus is mostly on orthopaedic implants, but there is a high potential for new implant-related surgical instrument solutions taking into account up-coming clinical demands and user needs accessible by actual 3D printing technologies

Introduction. Ilizarov fixators are reliant on tensioned fine wires for stability. The tension in the wires is generated using specific tensioning devices. Loss of wire tension over time may lead of loss a stability and complications. A series of in vitro experiments were undertaken to explore wire tensioner accuracy, the impact of fixation bolt torque and initial tension on loss of tension in ilizarov constructs under static and dynamic loads. Materials & Methods. Medical grade materials were applied to a synthetic bone analogue using surgical instruments in all experiments. Bolt torque was fixed at 6, 10 or 14 Nm using a torque limiting wrench. Wire tension was assessed using a strain measurement bridge. Wires were tensioned to 90, 110 and 130kg as measured by a commercial dynamometric tensioner. Static and dynamic testing was undertaken using an instron testing machine. Cyclical loads from 50–750N were applied for 5000 cycles. Results. Actual wire tension was approximately 15% less than indicated by the tensioner device. Using fixation bolt torques of 10Nm and 14Nm achieved final wire tensions of around 60% and 80% of that applied at 90 and 130kg of applied tension. Static load testing demonstrated self stiffening to similar levels in all pre-tensions. Dynamic testing demonstrated significant loss of tension, most of which occured in the first 3 cycles, inversely proportional to the tension initially applied. Conclusions. These experiments provides insight into the effect of initially applied wire tension on Illizarov mechanical performance. It is important surgeons understand how the different ways that these devices are applied affects mechanical performance. Further research examining what factors affect performance across different manufacturers equipment would therefore be relevant, alongside the development of novel fixation methods to reduce wire slippage and the further development of equipment for clinical use

Abstract. Background. Ultrasonic cutting of bone boasts many advantages over alternatively powered surgical instruments, including but not limited to: elimination of swarf, reduced reaction forces, increased precision in cutting and reduced adjacent soft tissue damage, reduced post-operative complications such as bleeding and bone fracture, reduced healing time, reduced intra-operative noise and ease of handling. Despite ultrasonic cutting devices being well established in oral and maxillofacial surgery, applications in orthopaedic surgery are more niche and are not as well understood. The aim of this study was to investigate the cutting speed (mm/s) and cutting forces (N) of orthopaedic surgeons using a custom-designed state of the art ultrasonic cutting tool to cut fresh human bone samples. Methods. A setup based on the Robot Operating System (ROS) and AprilTag was designed to track and to record the real time position of the ultrasonic cutting tool in space. Synchronised load cell axial force readings of three separate orthopaedic surgeons during ultrasonic cutting were recorded. Each surgeon was asked to find a comfortable position that reflects as close as possible their clinical handling of a cutting instrument used in surgery, and to perform two cuts in each of three samples of human cortical bone. Bone samples were obtained following ethical approval from an institutional review board (ethics approval number: SR1342) and prior informed consent was obtained from all patients. Bone samples were extracted from the femoral neck region of three hip osteoarthritis patients. During cutting, surgeons were allowed a total cutting time of one minute and cutting was conducted using an ultrasonic tool with frequency of a 35kHz (35.7 µm peak to peak displacement amplitude) under constant irrigation using a MINIPULS® 3 Peristaltic pump (38 revolutions per minute) using Phosphate-Buffered Saline (PBS) at 25°C. From the recorded data, the average instantaneous cutting velocity was calculated and the maximum cutting force was identified. Results. All surgeons assumed a back-and-forth cutting motion, variation in the applied cutting force was observed. The average vertical cutting speed, axial cutting force and cutting depth across all surgeons and all samples was 1.64 mm/s, 1.91 N and 0.73 mm, respectively. While increasing the axial cutting force resulted in a deeper cut, overloading of the ultrasound transducer occurred when the tool advanced too quickly into the bone tissue during cutting. The exact force threshold, or the optimal speed at which the surgeon can maintain a constant force during cutting, requires further investigation. Conclusions. In this study, all surgeons cut using a back-and-forth cutting motion, with variation in the applied cutting force which may ultimately inform which clinical applications in orthopaedic engineering are most suitable for this technology. Applying too much force caused overloading of the ultrasound transducer, which is a limitation with the current cutting tool. The results from this study may facilitate the eventual uptake of ultrasonic cutting tools for application in orthopaedic surgery. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Demographic changes will increase the number of surgical procedures in the next years. Therefore, quality assurance of clinical processes, such as the reprocessing of surgical instruments as well as intraoperative workflows will be of increasing importance to ensure patient safety. Surgical procedures are often complex and may involve risks for the patient. For fixation of screws, e.g. in case of pedicle screws, osteosynthesis plates or revision joint replacement surgery implants, the application of defined torques may be crucial in order to achieve optimal therapeutic results and minimal complication rates. In many cases a subjective rating of the surgeon is necessary as no adequate instrumentation is available. With the same subjective feeling, hammering or screwing in are performed to implant e.g. the acetabular component in THA. Our actual work is dedicated to the implementation of a functional prototypes of sensor- integrated instruments for specific types of intervention (especially in traumatology) and the evaluation of the sensor integrated surgical instruments in combination with RFID technology for smart process optimisation in the operating room as well as for reprocessing of surgical instruments and surgical management in combination with a knowledge-based planning, control and documentation system. Complementary (preferably wireless) sensors such for instrument identification, tracking or more complex measurements such as forces, torques, temperature or impacts during surgery as well as during reprocessing of reusable instruments could enable computer network based quality assurance in a much broader and comprehensive manner. Within the framework of the OR.NET initiative we follow the approach to integrate wireless sensors for measurement of temperature, force-torque as well as inertial sensors for orientation and impact control, depending on the specific type of application for monitoring of workflows during surgery as well as during reprocessing of reusable instruments and devices. The integration of smart surgical instruments into an open networked operating room based on the open communication standard IEEE 11073 knowledge-based workflow system, can help to improve the process and quality management

Abstract. Objectives. Accurate orientation of the acetabular component during a total hip replacement is critical for optimising patient function, increasing the longevity of components, and reducing the risk of complications. This study aimed to determine the validity of a novel VR platform (AescularVR) in assessing acetabular component orientation in a simulated model used in surgical training. Methods. The AescularVR platform was developed using the HTC Vive® VR system hardware, including wireless trackers attached to the surgical instruments and pelvic sawbone. Following calibration, data on the relative position of both trackers are used to determine the acetabular cup orientation (version and inclination). The acetabular cup was manually implanted across a range of orientations representative of those expected intra-operatively. Simultaneous readings from the Vicon® optical motion capture system were used as the ‘gold standard’ for comparison. Correlation and agreement between these two methods was determined using Bland-Altman plots, Pearson's correlation co-efficient, and linear regression modelling. Results. A total of 55 separate orientation readings were obtained. The mean average difference in acetabular cup version and inclination between the Vicon and VR systems was 3.4° (95% CI: −3–9.9°), and −0.005° (95% CI: −4.5–4.5°) respectively. Strong positive correlations were demonstrated between the Vicon and VR systems in both acetabular cup version (Pearson's R = 0.92, 99% CI: 0.84–0.96, p<0.001), and inclination (Pearson's R = 0.94, 99% CI: 0.88–0.97, p<0.001). Using linear regression modelling, the adjusted R. 2. for acetabular version was 0.84, and 0.88 for acetabular inclination. Conclusion. The results of this study indicate that the AescularVR platform is highly accurate and reliable in determining acetabular component orientation in a simulated environment. The AescularVR platform is an adaptable tracking system, which may be modified for use in a range of simulated surgical training and educational purposes, particularly in orthopaedic surgery. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Nowadays 80% of patients with bone sarcomas can benefit from limb salvage. Their disease-free life expectancy is not jeopardised by conservative surgery as long as safe margins are obtained. For this reason, the oncological result relies on the accuracy of pre-operative and per-operative surgical measurements. Pre-operative evaluation of tumours is now quite accurate with digital margins (computed tomography, MNR, digital angiography). However, surgeons are still using centimeters or conventional radiographs with their own technical limitations for per-operative evaluation. A more accurate technique is needed. The system is composed of three components: 1) a color, graphic computer workstation with software to calculate and present the location of the surgical instrument on a three-dimensional, reconstructed bone image, 2) a complete set of hand-held instruments containing infrared emitters, 3) an infrared receiver linked to the work station. This measuring system enables determination of the position and incidence of a surgical instrument in real time during surgery, with an accuracy of less than one mm. The system requires four steps: 1) recording data with C.T., N.M.R. or angiography, 2) creating a three-dimensional image displayed on the computer screen for preoperative simulation of a virtual operation, 3) recording the very important anatomical points of the patient and optimal incidences of the surgical instruments, 4) preoperative location of surgical instruments and control of their location on bone. This system is very useful for resection of bone tumours when the conventional location is uncertain (innonimate bone, rib), when very sharp accuracy is needed to preserve the growth plate of the distal femur in young children, and to avoid medullary damage in a spinal tumour. The frameless stereotactic device is also very accurate in the reconstructive phase of limb salvage. After an internal hemipelvectomy, the device permits localisation of the acetabular prosthesis in the precise location before resection. In our practice, the accuracy of the video guiding system is always within two mm as compared to conventional measurements usually between one or two cm for long bones and three to five cm for innominate bone. The use of a video guidance system is very beneficial for limb salvage surgery for pelvic bone tumours

Nowadays 80% of patients with bone sarcomas can benefit from limb salvage. Their disease-free life expectancy is not jeopardised by conservative surgery as long as safe margins are obtained. For this reason, the oncological result relies on the accuracy of pre-operative and per-operative surgical measurements. Pre-operative evaluation of tumours is now quite accurate with digital margins (computed tomography, MNR, digital angiography). However, surgeons are still using centimeters or conventional radiographs with their own technical limitations for per-operative evaluation. A more accurate technique is needed. The system is composed of three components: 1) a color, graphic computer workstation with software to calculate and present the location of the surgical instrument on a three-dimensional, reconstructed bone image, 2) a complete set of hand-held instruments containing infrared emitters, 3) an infrared receiver linked to the work station. This measuring system enables determination of the position and incidence of a surgical instrument in real time during surgery, with an accuracy of less than one mm. The system requires four steps: 1) recording data with C.T., N.M.R. or angiography, 2) creating a three-dimensional image displayed on the computer screen for preoperative simulation of a virtual operation, 3) recording the very important anatomical points of the patient and optimal incidences of the surgical instruments, 4) preoperative location of surgical instruments and control of their location on bone. This system is very useful for resection of bone tumours when the conventional location is uncertain (innonimate bone, rib), when very sharp accuracy is needed to preserve the growth plate of the distal femur in young children, and to avoid medullary damage in a spinal tumour. The frameless stereotactic device is also very accurate in the reconstructive phase of limb salvage. After an internal hemipelvectomy, the device permits localisation of the acetabular prosthesis in the precise location before resection. In our practice, the accuracy of the video guiding system is always within two mm as compared to conventional measurements usually between one or two cm for long bones and three to five cm for innominate bone. The use of a video guidance system is very beneficial for limb salvage surgery for pelvic bone tumours

In orthopaedic trauma surgery, X-ray fluoroscopy is frequently employed to monitor fracture reduction and to guide surgical procedures where implants are inserted to fix the fractures. Fluoro-navigation is the application of real-time navigation on intraoperatively acquired fluoroscopic images to achieve the same goals. The theoretical advantages of fluoro-navigation are:. Minimising exposure to X-ray on surgeons, operating room personells and patients,. Accurate positioning of implants,. Expanding the application of minimally invasive surgery,. Shortening the operation time. Fluoro-navigation is particular indicated in orthopaedic trauma as the fracture fragments are mobile and the orientations are not fixed before surgery. At this time, many procedures that require intraoperative fluoroscopic control can now be done with fluoro-navigation. These procedures include:. Fixation of femoral neck fractures with percutaneous cannulated screws,. Intramedullary locked nails for long bone fractures,. Intramedullary fixation of trochanteric fractures. Percutaneous fixation of sacro-iliac fractures dislocations. Percutaneous fixation of iliac wing fractures. Percutaneous fixation of acetabulum fractures. Insertion of Ilizarov tension wires for complex articular fractures. Many percutaneous fixation procedures that need fluoroscopic controls. Since 2001, we have been using fluoro-navigation orthopaedic trauma surgery. 535 different procedures of operative treatment of fractures were carried out. These operative procedures included. Operation, amount, success rate:. Femoral neck fractures, 65, 100%, Gamma nailing, 172, 100%, Femoral locked nails, 77, 98.5%, Tibial locked nails, 53, 100%, Sacro-iliac screws, 45, 95.1%, Pelvic acetabular fractures, 29, 96.1%, Ilizarov tension wires, 13, 100%, Percutaneous screws, 18, 100%, Distal locking without X-ray, 15, 100%, 3-D Navigation, 48 92.7%. Our clinical experience has confirmed the advantages and the extended applications of this technique benefited many of our patients by enhancing minimally invasive technique in orthopaedic trauma surgery, better implant position and significantly decreasing the radiation of the fluoroscopy (p< 0.05). We have modified the operative procedures in order to adapt better with the fluoro-navigation procedures. We also worked with the industrial partners to design specific instruments as well as modified the existing surgical instruments to facilitate the fluoro-navigation procedures. Most of the failure were due to poor quality fluoro-images, unstable operating system and poorly adapted surgical instruments in the early phase of the applications. Further improvement is expected in the system on the hardware and software for quicker image acquisition with improved quality, accurate and precise registration, increase interactivities and adaptation of surgical instruments as well as implants. There is a great need for the development of dedicated surgical instruments for orthopaedic trauma sugary in line with the further improvement of the navigation system. With the establishment of image libraries for implants and skeleton, further minimising the need for standard fluoroscopy will be possible. The combination of 3-D fluoroscopy and the navigation will improve percutaneous fixation of articular fractures. At the time, it is only possible to navigate the images obtained during the operation after fracture reduction or manipulation is completed. The possibility to navigate on each individual fracture fragment will extend the technique even more to real-time fracture reduction. The fluoro-navigation system will also play an important role in surgical training as well as assessment in the virtual surgical environment. We also developed specific training models for fluoro-navigation for preoperative training and practice of standard procedures. This will help to promote further application of fluoro-navigation in orthopaedic trauma. The recognition of its clinical significance will help to stimulate more research and thus encourages industries to devote more resources in the development of fluoro-navigation for orthopaedic trauma

INTRODUCTION. Due to increasing interest into taper corrosion observed primarily in hip arthroplasty devices with modular tapers, efforts towards characterizing the corrosion byproducts are prevalent in the literature [1–4]. As a result of this motivation, several studies postulate cellular induced corrosion due to the presence of remarkable features in the regions near taper junction regions and articulating surfaces [3–5]. Observations made on explanted devices from a retrieval database as well as laboratory tests have led to the alternative proposal of electrocautery-electrosurgery damage as the cause of these features. These surgical instruments are commonly used for hemostasis or different degrees of tissue dissection. METHODS. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to evaluate the features observed on retrieved devices. Retrieved devices consisted of OXINIUM and cobalt-chromium-molybdenum (CoCrMo) femoral implants, a Titanium-alloy hip stem, and a CoCrMo metal-on-metal femoral head. Electrocautery-electrosurgery damage was created using a SurgiStat II (Valleylab, Colorado) onto various components (CoCrMo, OXINIUM femoral heads as well as Ti-6Al-4V and CoCrMo alloy test stem constructs). Test components were evaluated using the same methods as the retrieved devices. RESULTS. Remarkable features were present on retrieved devices (Figure 1) which were similar to previous studies (3–5). The appearance of these features could be described as crater-like, pitted, scratched, molten or splattered material, and ruffled. These features were present on articulating and non-articulating regions as well as near taper junctions. Testing performed on samples using the SurgiStat II, created features that were similar in appearance (Figure 1). Additionally, material transfer that included an iron peak based on EDS in addition to the cobalt and chromium (present due to native material) was detected in the regions of contact (Figure 2). CONCLUSIONS. It was possible to re-create damage features similar to those previously characterized as remarkable features created by cellular-induced corrosion [3–5]. It is theorized that the high-voltage based electrocautery (commonly Bovie) or high-frequency based electrosurgical devices can result in localized degradation/alteration of oxides and passive regions of commonly used orthopaedic alloys. These surgical instruments, specifically the cutting electrodes, are frequently made of stainless steels which can result in iron transfer during contact with the device. During the surgical use of the electrocautery-electrosurgery instrument, it may be necessary to remove tissue, bone, or cauterize near the implant or explant which may have led to the damage features noted in this study and the previous literature [3–5]. If this damage occurs during the initial implantation of the devices, it may further exacerbate corrosion in the damaged region and/or alter the mechanical integrity of the constructs (i.e. fatigue performance)

Introduction. In hip arthroplasty, it has been shown that assembly of the femoral head onto the stem remains a non-standardized practice and differs between surgeons [1]. Pennock et al. determined by altering mechanical conditions during seating there was a direct effect on the taper strength [2]. Furthermore, Mali et al. demonstrated that components assembled with a lower assembly load had increased fretting currents and micromotion at the taper junction during cyclic testing [3]. This suggests overall performance may be affected by head assembly method. The purpose of this test was to perform controlled bench top studies to determine the influence of impaction force and compliance of support structure (or damping) on the initial stability of the taper junction. Materials and Methods. Test Specimens. Testing was performed on 36mm +5mm CoCr heads combined with prototype Ti6Al4V locking taper analogs both machined with approximately a 5.67º taper angle. To minimize sample variation, the locking taper analogs were dimensionally matched with CoCr femoral heads to maintain a uniform angle difference. Prior to testing, samples were cleaned with isopropanol and allowed to dry. Effect of Peak Force Magnitude. Testing was performed on a rigid setup where a 10N preload was applied to the femoral head axially. Heads were assembled with loads ranging from 2kN–10kN using an impaction tower and seating loads were recorded at a collection rate of 273kHz. After assembly, tensile loads were applied until the taper junction was fully disassembled and distraction loads were recorded at a collection rate of 500Hz. Effect of Damping. 40 durometer rubber pads were placed underneath the trunnions as well as to the striking surface of the impaction tower to simulate compliance in the supporting structure and the surgical instruments. Aside from the added damping, testing was performed identical to the rigid setup tests. Results. Taper stability (as assessed by disassembly forces) increased linearly with peak assembly force with an R2 value of 0.95 for both rigid and compliant groups (Figure 1). On average a 46% larger input energy was required in the compliant group to achieve a comparable impaction force to the rigid group (Figure 2). However, the correlation between the assembly load and distraction force was not affected. Discussion. As shown in previous studies, impact force has a large effect on initial taper stability. An interesting finding in this study was that system compliance has a large effect on the applied assembly force. The addition of a compliant setup was intended to simulate a surgical scenario where factors such as the patient's leg positioning, patient mass, surgical instruments, and surgical approach may influence the resulting compliance due to the dissipation of impaction energy and reducing the applied impaction force. Based on test results, surgical procedure as well as patient variables may have a significant effect of initial taper stability. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Purpose. When we perform total knee arthroplasty (TKA), the accurate osteotomy and implant setting is important as follows to improve long-term results. As means to perform osteotomy exactly, patient specific surgical instruments (PSI) patient specific surgical instruments planning based on pre-operative MRI (Signature, Materialise) and Image-free navigation system (Navi: Knee unlimited; BrainLAB) exist. However, there is not the report to compare which is exact for the same patient at the same time using two methods. We report to compare the osteotomy plans by two methods. Materials. Nine cases of TKA (Vanguard Complete Knee System, PS, BIOMET) operated on by one operator in our hospital from October 2012 to September 2013. 78.0 years average age (71–81 years old), sex was 6 cases women, 3 men. Methods. Intra-operatively measurements of α, β, γ, δ angle, rotation angle of the femoral component and the size of the components were evaluated between the two groups. Coronal cutting angles were considered as outlier the difference between the 3 ° or more from the preoperative planning on computed tomography (CT) scans made one week after surgery. Results. PSI cases were inclined with respect to Navi cases, coronal plane: average varus 0.4 ° (valgus 1.0° to varus 3.0°), sagittal plane: flexion 1.0° (flexion 5.0° to extension 3.5°), axial plane: internal rotation 0.9° (internal rotation 3.5° to external rotation 0.0°) in the femur. Coronal plane: average valgus 0.5 ° (valgus 1.5° to varus 4.5°), sagittal plane: backward tilt 0.9° (forward tilt 3.0° to backward tilt 4.5°) in the tibia. Three cases of femoral implant were different from PSI plan, 5 cases in tibia. One of PSI cases in the femur and 1 case in tibia is outlier. Discussion. In the femoral side, fitting of the PSI was good, and error is less. However, in the tibia, some cases of fitting were bad and large error. These PSI were not stable on the bone and looks like seesaw motion at the tibial side. It is necessary to final confirmation by using the extramedullary guide in PSI cases. Conclusion. Accuracy of Navi was higher than PSI in our study

Introduction. We are a high-volume arthroplasty unit performing over 800 primary THRs annually at an approximate reimbursement of £6.5 million to the Trust. 70% are hybrid and we have been using the Taperfit - Trinity combination (Corin, Cirencester) since March 2016. We aimed to investigate the potential cost-savings and clinical benefits of instrument rationalisation using this system following GIRFT principles. Methods. Taperfit (ODEP 10A) is a polished, collarless, double tapered stem available in multiple sizes/offsets. Trinity is a hemispherical porous titanium cementless shell. A prospective audit of implant size was performed for the first 50 cases. Based on these findings, instruments were reduced to a single tray per component based on predicted size, named ‘Corin Hip for the Osteoarthritic Patient’ (CHOP). A further re-audit was performed to confirm correct tray constituent sizes. Financial data were calculated using known TSSU costs of approximately £50 per tray. Results. The audit revealed 92% (46/50) of stem sizes 2 or smaller and 86% (43/50) of shell sizes 54 or smaller. Trays per case were then rationalised from 6 to 2. Each acetabular tray had seven reamers (‘CHOP 1’ 42, 46–56 or CHOP 2 46, 54–64) and each femoral tray had broaches sized 0–2 (CHOP 1) or 2–4 (CHOP 2). Re-audit confirmed the CHOP 1 sets covered approximately 85% of cases. A TSSU saving of £192/case was achieved. Additional benefits were: all trays easily kept under laminar flow, time spent counting instruments was reduced and theatre shelving space liberated. Conclusion. Rationalisation of surgical instruments has saved the Trust approximately £100,000/year. Fewer instruments potentially reduce the risk of ‘never events’ and infection. Industry savings on consigned instruments have been passed on with significant reduction in our implant procurement costs allowing the use of hybrid implants for the price of our all cemented combination

Total joint arthroplasty (TJA) is one of the most successful procedures in orthopaedics. Despite the excellent clinical and functional results, periprosthetic joint infection (PJI) following TJA is a feared complication. For instance, the reported PJI rate after primary total knee arthroplasty is about 0.5–1.9%. In general, prevention of periprosthetic joint and surgical site infections is of utmost importance. This can be reduced by strict antisepsis, adequate sterilization of the surgical instruments and meticulous surgical technique. An indisputable role in prevention of SSI in TJA has been the use of peri-operative systemic antibiotic prophylaxis. The most common recommended antibiotics for prophylaxis in TJA are cefazolin or cefuroxime. In contrast, routine use of commercial antibiotic-loaded bone cement (ALBC) in primary total joint arthroplasty is still a concern of open debate. The use of antibiotic-loaded bone cement delivers a high concentration of antibiotics locally and can decrease the infection rate, which is supported by several studies in the literature. In this context, we present the pros of routine use of commercial antibiotic-loaded bone cement

Objectives. Many studies have investigated the kinematics of the lumbar spine and the morphological features of the lumbar discs. However, the segment-dependent immediate changes of the lumbar intervertebral space height during flexion-extension motion are still unclear. This study examined the changes of intervertebral space height during flexion-extension motion of lumbar specimens. Methods. First, we validated the accuracy and repeatability of a custom-made mechanical loading equipment set-up. Eight lumbar specimens underwent CT scanning in flexion, neural, and extension positions by using the equipment set-up. The changes in the disc height and distance between adjacent two pedicle screw entry points (DASEP) of the posterior approach at different lumbar levels (L3/4, L4/5 and L5/S1) were examined on three-dimensional lumbar models, which were reconstructed from the CT images. Results. All the vertebral motion segments (L3/4, L4/5 and L5/S1) had greater changes in disc height and DASEP from neutral to flexion than from neutral to extension. The change in anterior disc height gradually increased from upper to lower levels, from neutral to flexion. The changes in anterior and posterior disc heights were similar at the L4/5 level from neutral to extension, but the changes in anterior disc height were significantly greater than those in posterior disc height at the L3/4 and L5/S1 levels, from neutral to extension. Conclusions. The lumbar motion segment showed level-specific changes in disc height and DASEP. The data may be helpful in understanding the physiologic dynamic characteristics of the lumbar spine and in optimising the parameters of lumbar surgical instruments. Cite this article: M. Fu, Q. Ye, C. Jiang, L. Qian, D. Xu, Y. Wang, P. Sun, J. Ouyang. The segment-dependent changes in lumbar intervertebral space height during flexion-extension motion. Bone Joint Res 2017;6:245–252. DOI: 10.1302/2046-3758.64.BJR-2016-0245.R1

Removal of femoral bone cement is required for preparation of proper implant bed for reimplantation of a new femoral component in revision total hip arthroplasty. Several devices and procedures have been developed for cement removal, including an extracorporal shock-wave lithotripter and YAG laser, as well as a high-powered drill or burr under the control of conventional fluoroscopic images and an intrafemoral endoscopy. Ultrasonic tools are efficient for removal of bone cement with minimal damage to bone. We use a high-powered burr to remove the deep femoral bone cement under the control of conventional fluoroscopic images, although the problem of this procedure is large exposure of X-ray and two dimensional viewing of burr position which can result in perforation in the third plane. Computer-assisted fluoroscopic navigation system allows the surgeons to provide positional information about surgical instrument to target bones during operations. Two-dimensional image data are obtained using the fluoroscope with a reference frame and stored on a computer workstation. A camera interfaced with the computer then tracks the position of the patient and registered surgical instruments during the procedure. Taking advantage of the real-time guidance of computer-assisted fluoroscopic navigation system, we introduce a valuable technique using computer-assisted fluoroscopic navigation system for performing removal of the cement of the femoral canal in revision cemented total hip arthroplasty

The use of surgical navigation in computer assisted or image guided procedures requires the precise measurement of the spatial position of surgical instruments. Investigations of several physical principles have turned out that two technologies are best feasible for application in clinical routines:. optical technology,. electromagnetic technology. Available systems based on either principle deliver measurement information for the 3D-position of a surgical instrument, expressed by the x-y-z coordinates of its tip, and for its 3D-orientation, described by the direction of the instrument axis towards the tip. It is therefore common terminology to describe such measurement systems as 3D/6D digitizing or localizing systems. The presentation will describe basic principles of both technologies, including their main technical features and the design of key components such as rigid bodies for optical systems and sensor coils for electromagnetic systems. The survey includes an overview of known challenges and problems, and how commercial systems cope with these. A comparison of both technologies outlines the advantages and drawbacks in different applications as well as possible future improvements. It leads to the conclusion that both technologies will co-exist for the foreseeable future

The use of surgical navigation in computer assisted or image guided procedures requires the precise measurement of the spatial position of surgical instruments. Investigations of several physical principles have turned out that two technologies are best feasible for application in clinical routines: a) optical technology, b) electromagnetic technology. Available systems based on either principle deliver measurement information for the 3D-position of a surgical instrument, expressed by the x-y-z coordinates of its tip, and for its 3D-orientation, described by the direction of the instrument axis towards the tip. It is therefore common terminology to describe such measurement systems as 3D/6D digitizing or localizing systems. The presentation will describe basic principles of both technologies, including their main technical features and the design of key components such as rigid bodies for optical systems and sensor coils for electromagnetic systems. The survey includes an overview of known challenges and problems, and how commercial systems cope with these. A comparison of both technologies outlines the advantages and drawbacks in different applications as well as possible future improvements. It leads to the conclusion that both technologies will co-exist for the foreseeable future

The December 2023 Wrist & Hand Roundup³⁶⁰ looks at: Volar locking plate for distal radius fractures with patient-reported outcomes in older adults; Total joint replacement or trapeziectomy?; Replantation better than revision amputation in traumatic amputation?; What factors are associated with revision cubital tunnel release within three years?; Use of nerve conduction studies in carpal tunnel syndrome; Surgical site infection following surgery for hand trauma: a systematic review and meta-analysis; Association between radiological and clinical outcomes following distal radial fractures; Reducing the carbon footprint in carpal tunnel surgery inside the operating room with a lean and green model: a comparative study.

Over the past decades, computer-aided navigation system has experienced tremendous development for minimising the risks and improving the precision of the surgery. Nowadays, some commercially-available and self-developed surgical navigation systems have already been tested and proved successfully for clinical applications. However, all of these systems use computer screen to render the navigation information such as the real-time position and orientation of the surgical instrument, virtual path of preoperative surgical planning, so that the surgeons have to switch between the actual operation site and computer screen which is inconvenient and impact the continuity of surgery. In recent years, Augmented Reality (AR)- based surgical navigation is a promising technology for clinical applications. In the AR system, virtual and actual reality are mixed, offering real-time, high-quality visualisation of an extensive variety of information to the users. Therefore, in this study, a pilot study of a surgical navigation system for orthopaedics based on optical see-through augmented reality (AR-SNS) is presented, which encompasses the preoperative surgical planning, calibration, registration, and intra-operative tracking. With the aid of AR-SNS, the surgeon wearing the optical see-through head-mounted display can obtain a fused image that the 3D virtual critical anatomical structures are aligned with the actual structures of patient in intra-operative real-world scenario, so that some disadvantages of the traditional surgical navigation are overcome (For example, surgeon is no longer obliged to switch between the real operation scenario and computer screen), and the safety, accuracy, and reliability of the surgery may be improved

The October 2023 Knee Roundup³⁶⁰ looks at: Cementless total knee arthroplasty is associated with more revisions within a year; Kinematically and mechanically aligned total knee arthroplasties: long-term follow-up; Aspirin thromboprophylaxis following primary total knee arthroplasty is associated with a lower rate of early periprosthetic joint infection compared with other agents; The impact of a revision arthroplasty network on patient outcomes; Re-revision knee arthroplasty in a tertiary centre: how does infection impact on outcomes?; Does the knee joint have its own microbiome?; Revision knee surgery provision in Scotland; Aspirin is a safe and effective thromboembolic prophylaxis after total knee arthroplasty: a systematic review and meta-analysis; Patellar resurfacing and kneeling ability after total knee arthroplasty: a systematic review.

The critical relationship between airborne microbiological contamination in an operating theatre and surgical site infection (SSI) is well known. The aim of this annotation is to explain the scientific basis of using settle plates to audit the quality of air, and to provide information about the practicalities of using them for the purposes of clinical audit. The microbiological quality of the air in most guidance is defined by volumetric sampling, but this method is difficult for surgical departments to use on a routine basis. Settle plate sampling, which mimics the mechanism of deposition of airborne microbes onto open wounds and sterile instruments, is a good alternative method of assessing the quality of the air. Current practice is not to sample the air in an operating theatre during surgery, but to rely on testing the engineering systems which deliver the clean air. This is, however, not good practice and microbiological testing should be carried out routinely during operations as part of clinical audit.

Cite this article: Bone Joint J 2024;106-B(9):887–891.

Aims

Surgical approaches that claim to be minimally invasive, such as the direct anterior approach (DAA), are reported to have a clinical advantage, but are technically challenging and may create more injury to the soft-tissues during joint exposure. Our aim was to quantify the effect of soft-tissue releases on the joint torque and femoral mobility during joint exposure for hip resurfacing performed via the DAA.

Aims

Metal particles detached from metal-on-metal hip prostheses (MoM-THA) have been shown to cause inflammation and destruction of tissues. To further explore this, we investigated the histopathology (aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) score) and metal concentrations of the periprosthetic tissues obtained from patients who underwent revision knee arthroplasty. We also aimed to investigate whether accumulated metal debris was associated with ALVAL-type reactions in the synovium.

The June 2023 Wrist & Hand Roundup³⁶⁰ looks at: Residual flexion deformity after scaphoid nonunion surgery: a seven-year follow-up study; The effectiveness of cognitive behavioural therapy for patients with concurrent hand and psychological disorders; Bite injuries to the hand and forearm: analysis of hospital stay, treatment, and costs; Outcomes of acute perilunate injuries - a systematic review; Abnormal MRI signal intensity of the triangular fibrocartilage complex in asymptomatic wrists; Patient comprehension of operative instructions with a paper handout versus a video: a prospective, randomized controlled trial; Can common hand surgeries be undertaken in the office setting?; The effect of corticosteroid injections on postoperative infections in trigger finger release.

Aims

It is important to analyze objectively the hammering sound in cup press-fit technique in total hip arthroplasty (THA) in order to better understand the change of the sound during impaction. We hypothesized that a specific characteristic would present in a hammering sound with successful fixation. We designed the study to quantitatively investigate the acoustic characteristics during cementless cup impaction in THA.

Aims

It is important to analyze objectively the hammering sound in cup press-fit technique in total hip arthroplasty (THA) in order to better understand the change of the sound during impaction. We hypothesized that a specific characteristic would present in a hammering sound with successful fixation. We designed the study to quantitatively investigate the acoustic characteristics during cementless cup impaction in THA.

The use of artificial intelligence (AI) is rapidly growing across many domains, of which the medical field is no exception. AI is an umbrella term defining the practical application of algorithms to generate useful output, without the need of human cognition. Owing to the expanding volume of patient information collected, known as ‘big data’, AI is showing promise as a useful tool in healthcare research and across all aspects of patient care pathways. Practical applications in orthopaedic surgery include: diagnostics, such as fracture recognition and tumour detection; predictive models of clinical and patient-reported outcome measures, such as calculating mortality rates and length of hospital stay; and real-time rehabilitation monitoring and surgical training. However, clinicians should remain cognizant of AI’s limitations, as the development of robust reporting and validation frameworks is of paramount importance to prevent avoidable errors and biases. The aim of this review article is to provide a comprehensive understanding of AI and its subfields, as well as to delineate its existing clinical applications in trauma and orthopaedic surgery. Furthermore, this narrative review expands upon the limitations of AI and future direction.

Cite this article: Bone Joint Res 2023;12(7):447–454.

Aims

The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases.

Aims

Ankle fracture fixation is commonly performed by junior trainees. Simulation training using cadavers may shorten the learning curve and result in a technically superior surgical performance.

Aims

Gram-negative periprosthetic joint infection (PJI) has been poorly studied despite its rapidly increasing incidence. Treatment with one-stage revision using intra-articular (IA) infusion of antibiotics may offer a reasonable alternative with a distinct advantage of providing a means of delivering the drug in high concentrations. Carbapenems are regarded as the last line of defense against severe Gram-negative or polymicrobial infection. This study presents the results of one-stage revision using intra-articular carbapenem infusion for treating Gram-negative PJI, and analyzes the characteristics of bacteria distribution and drug sensitivity.

Total hip replacement in Germany has been performed in 227293 cases in 2015 and tendency is increasing. Although it is a standard intervention, freehand positioning of cup protheses has frequently poor accuracy. Image-based and image-free navigation systems improve the accuracy but most of them provide target positions as alphanumeric values on large-size screens beneath the patient site. In this case the surgeon always has to move his head frequently to change his eye-focus between incision and display to capture the target values. Already published studies using e.g. IPod-based displays or LED ring displays, show the chance for improvement by alternative approaches. Therefore, we propose a novel solution for an instrument-mounted small display in order to visualise intuitive instructions for instrument guidance directly in the viewing area of the surgeon. For this purpose a solution consisting of a MicroView OLED display with integrated Arduino microcontroller, equipped with a Bluetooth interface as well as a battery has been developed. We have used an optical tracking system and our custom-designed navigation software to track surgical instruments equipped with reference bodies to acquire the input for the mini-display. The first implementation of the display is adapted to total hip replacement and focuses on assistance while reaming the acetabulum. In this case the reamer has to be centred to the middle point of the acetabular rim circle and its rotation axis must be aligned to the acetabular centre axis by Hakki. By means of these references the actual deviations between instrument and target pose are calculated and indicated. The display contains a cross-hair indicator for current position, two bubble level bars for angular deviation and a square in square indicator for depth control. All display parts are furnished with an adaptive variable scale. Highest possible resolution is 0.5 degrees angular, 1 millimeter for position and depth resolution is set to 2 mm. Compared to existing approaches for instrument-mounted displays, the small display of our solution offers high flexibility to adjust the mounting position such that it is best visible for the surgeon while not constraining instrument handling. Despite the small size, the proposed visualisation symbols provide all information for instrument positioning in an intuitive way

Aims

To evaluate if, for orthopaedic trainees, additional cadaveric simulation training or standard training alone yields superior radiological and clinical outcomes in patients undergoing dynamic hip screw (DHS) fixation or hemiarthroplasty for hip fracture.

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The aim of this study was to determine the risk of tibial eminence avulsion intraoperatively for bi-unicondylar knee arthroplasty (Bi-UKA), with consideration of the effect of implant positioning, overstuffing, and sex, compared to the risk for isolated medial unicondylar knee arthroplasty (UKA-M) and bicruciate-retaining total knee arthroplasty (BCR-TKA).

Aims

In the UK, the NHS generates an estimated 25 megatonnes of carbon dioxide equivalents (4% to 5% of the nation’s total carbon emissions) and produces over 500,000 tonnes of waste annually. There is limited evidence demonstrating the principles of sustainability and its benefits within orthopaedic surgery. The primary aim of this study was to analyze the environmental impact of orthopaedic surgery and the environmentally sustainable initiatives undertaken to address this. The secondary aim of this study was to describe the barriers to making sustainable changes within orthopaedic surgery.

Aims

It is common practice for patients to have postoperative blood tests after total joint replacement (TJR). However, there have been significant improvements in perioperative care with arthroplasty surgery, and a drive to reduce the length of stay (LOS) and move towards day-case TJR. We should reconsider whether this intervention is necessary for all patients.

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To determine the major risk factors for unplanned reoperations (UROs) following corrective surgery for adult spinal deformity (ASD) and their interactions, using machine learning-based prediction algorithms and game theory.

Aims

Periprosthetic joint infections (PJIs) with prior multiple failed surgery for reinfection represent a huge challenge for surgeons because of poor vascular supply and biofilm formation. This study aims to determine the results of single-stage revision using intra-articular antibiotic infusion in treating this condition.

In performing posterior cruciate ligament- retaining total knee arthroplasty (CR-TKA), the original surgical instrument was devised to obtain the range of motion and stability of the knee joint adequate for daily life of Japanese people. We have presumed the tentative joint line as intercondylar notch point of the distal femur, and performed surgery using surface replacement to resect metal width of the femoral component for the distal femur by setting the knee to the original position based on understanding of the shape of anterior curvature of the distal femur in Japanese people in case of implanting the femoral component. In order to obtain stability of the knee, we have minimally released the soft tissue and resected the anterior cruciate ligament (ACL), whereas completely preserved the posterior cruciate ligament (PCL) and maintained physiological ligament balance of the knee joint by resecting the medial condyle of the tibia (genu varus). Our surgical procedure enabled deep flexion knee (knee embracing) greater than 145 degrees in 9.7% and also allowed Japanese sitting in three different designs of total knee joints

Computer assisted surgery is becoming more frequently used in the medical world. Navigation of surgical instruments and implants plays an important role in this surgery. OrthoPilot™ Hip Suite (BBraun Aesculap) is one such system used for hip navigation in orthopaedic surgery. However the accuracy of this system remains to be determined independently of the manufacturer. The manufacturer supplies a technical specification for the accuracy of the system (± 2 mm and ± 2°) and previous research has been undertaken to compare its clinical accuracy against conventional hip replacements by x-ray. This clinical validation is important but contains many sources of error or deviation from an ideal outcome in terms of the surgeons' use of the system, inaccurate palpation of landmarks, variation in actual cup position from that given by the navigation system and measurement of the final cup position. It is therefore not possible to validate the claims of the manufacturer from this data. There is no literature evaluating the technical accuracy of the software i.e. the accuracy of the system given known inputs. This study had two main aims 1) validating the accuracy of the OrthoPilot data while navigating the surgical instruments and 2) validating the accuracy of navigation algorithm inside the OrthoPilot system which determines cup implant placement. The OrthoPilot validation was performed and compared against the gold standard of a VICON movement analysis system. The system used was OrthoPilot™ with a Spectra camera from Northern Digital Inc. (Ontario, Canada). Software investigated was the Hip Suite THA cup only navigation software Version 3.1. The validation was performed and compared against the VICON Nexus version 1.4.116 with Bodybuilder software version 3.55. An aluminium pelvis phantom was used for measurement allowing accurate and repeatable inputs. The OrthoPilot system has three types of instruments sets; passive, active and hybrid. This study was carried out with the passive instruments set. Data were captured simultaneously from both the OrthoPilot and VICON systems for the supine position of the phantom. Distances between the anatomical land marks on the phantom were compared to test the data capturing accuracy of the OrthoPilot system. Anatomical land marks of right anterior superior iliac supine (RASIS), left anterior superior iliac supine (LASIS) and Pubic Symphasis (PS) were palpated to define the Anterior Pelvic Plane (APP). Distances between the anatomical landmarks of RASIS to LASIS, RASIS to PS and LASIS to PS were considered for comparison. Width and height of the pelvis was varied to examine different APPs. The width and height used were 170 mm and 53 mm, 230 mm and 88 mm, and 290 mm and 123 mm respectively. One hundred APP data sets were captured at each instance. The accuracy of the hip navigation algorithm was tested by applying similar algorithm to calculate the native anteversion and inclination angles of the acetabulum using the VICON system. Data were captured simultaneously from both OrthoPilot and VICON systems. Radiographic anteversion and inclination angles were obtained with phantom model, which had 14° of anteversion angle and 45° of inclination angle. APP of 230 mm in width and 88 mm in height was used to obtain anterior pelvic plane data. Position vectors for each anatomical land mark from the OrthoPilot system were extracted from relevant transformation matrices, while position vectors from the VICON system were extracted from static trial modelling. The distance data from both systems were compared with calibrated distance data from the phantom model. Mean values of the distances between anatomical landmarks were found to be similar for both OrthoPilot and VICON systems. In addition, these distances were comparable with the pelvic phantom model data, within 1 mm for all measured distances for the VICON and 2 mm for the OrthoPilot. Furthermore, the standard deviations were less than 1% of the measured value. Comparison was also made for the anteversion and inclination angles of the acetabulum of the pelvic model with OrthoPilot and VICON data. Both systems produced similar results for the mean angle values, within 0.5° of the known angles for the VICON and 1° for the OrthoPilot and with standard deviations of the measured values of less than 1%. All the data were captured simultaneously from both OrthoPilot and VICON systems under the same laboratory conditions. According to the above results it is clear that the distance readings obtained from the OrthoPilot are comparable to the results obtained from the gold standard VICON system and the calibrated distance readings of the phantom. In addition, acetabular angle results obtained from OrthoPilot are almost equivalent to results obtained from VICON and the calibrated phantom angles. Finally it is can be concluded that, both the data palpation with OrthoPilot system and acetabular angle calculation algorithm of the OrthoPilot system are accurate enough for the real world clinical tasks they are expected to perform

Introduction. Revision Total Hip Arthroplasties (THA) have a significantly higher failure rate than primary THA's and the most common cause is aseptic loosening of the cup. To reduce this incidence of loosening various porous metal implants with a rough surface and a porous architecture have been developed which are said to increase early osteointegration. However, for successful osteointegration a minimal micromotion between the implant and the host bone (primary stability) is beneficial. It has not been previously determined if the primary stability for the new Gription® titanium cup differs from that of the old Porocoat® titanium cup. Material and Methods. In 10 cadaveric pelvises, divided into 20 hemipelvises, bilateral THA's were performed by an experienced surgeon (RGB) following the implant manufacturer's instructions and with the original surgical instruments provided by the company. In randomized fashion the well established Porocoat® titanium implant was implanted on one side of each each hemipelvis whereas on the corresponding opposite side the modified implant with a Gription® coating was inserted. Radiographs were taken to confirm satisfactory operative results. Subsequently, the hemipelvis and cups were placed in a biomechanical testing machine and subjected to physiological cyclic loading. Three-dimensonal loading corresponded to 30% of the load experienced in normal gait was imposed reflecting the limited weight bearing generally prescribed postoperatively. The dynamic testing took place in a multi-axial testing machine for 1000 cycles. Relative motion and micromotion were quantified using an optical measurement device (Pontos, GOM mbh, Braunschweig, Germany). Statistical evaluation was performed using the Wilcoxon signed-rank test. Results and conclusion. The standard Porocoat® titanium cups showed a mean relative motion with respect to the host bone of 54.74µm (Range 26.04 – 127.06µm), while the porous Gription® titanium cup displayed a relative motion with respect to the host bone of 49.77µm (Range 24.69 – 128.37µm). The Wilcoxon test did not reveal a significant difference between the two surfaces. The in-vitro biomechanical evaluation of both acetabular cups under a physiologic loading scenario showed no significant difference with regard to primary stability. Both the extensively tried and clinically successful Porocoat® titanium cup and the newer Gription® coated cup showed very little micromotion and both implants should therefore allow good osteointegration

Introduction. Dislocation due to suboptimal cup positioning is a devastating complication in the early phase after total hip arthroplasty. Malpositioning can also result in other mechanical complications like subluxation, edge loading, increased debris, surface damage or squeaking in ceramic-on-ceramic hips. Preventing at least some of these complications in younger and more active patients is of paramount interest for the individual patient and for the society since optimized component orientation is an important determinant to reduce such risks and to further increase longevity of the implant. This study reports on two new surgical instruments that help the orthopedic surgeon to manually place both components within the optimized combined safe-zone (cSafe-Zone). Material and Methods. More than 900 minimal-invasive total hip arthroplasties (MIS-THA) have been performed between 2007 and 2015 in our institution using the minimal-invasive direct anterior approach (DAA) on an orthopedic table with foot holder. Cups were implanted applying the “stem-first” surgical technique i.e. the prosthetic stem dictates the orientation of the socket depending on the prosthesis design. A system-specific trial head which indicates the prosthesis-specific relative orientation of cup and stem and a modified cup impactor were used to finally seat the definitive acetabular socket manually during trial stem reduction while fully visually controlling the optimal orientation of the cup during impaction. This surgical technique drives both components into their optimal relative positions according to the combined version and the combined safe-zone concept in total hip arthroplasty. Results. Both new instruments, femoral trial head as well as the modified cup impactor, provide an easy way to manually control the optimal placement of the acetabular socket during impaction intraoperatively. The combined safe-zone is clearly indicated and the inverse interrelationship of stem and cup anteversion is ideally reflected by this simple mechanical system. In patients operated on with the “stem-first” technique the components were placed in the new cSafe-Zone in 94% of the cases and no squeaking or prosthetic impingement did occur in any of these patients. One early dislocation did occur and was treated by closed reduction. Conclusion. Stem-first technique using trial head-controlled impaction with a modified cup impactor is ideally suited for the minimal-invasive direct anterior approach in total hip arthroplasty to control the placement of both prosthetic components. It assists the surgeon in aligning the cup and the stem according to the cSafe-Zone in order to get the intended range of movement (iROM)

INTRODUCTION. Total knee replacement is mostly done with alignment rods in order to achieve a proper Varus / Valgus alignement. Other techniques are computer assisted navigation or MRI based preoperative planning. iASSIST™ is a computer assisted stereotaxic surgical instrument system to assist the surgeon in the positioning of the orthopaedic implant system components intra-operatively. It is imageless and the communication between the PC and the “Pod's” does not require any direct camera view, it is a bluethooth comunication system. This study presents preliminary results utilizing iASSIST™. The aim of this study was to test and compare radiographic alignment, functional outcomes, and perioperative morbidity of the iASSIST™ Knee system versus conventional total knee arthroplasty. METHODS. In a prospective randomized trial we investigated 60 patients with osteoarthritis of the knee joint. Each surgical procedure was conducted by highly experienced surgeons. In both groups the implant Legacy LPS-Flex Fixed Bearing Knee was used (Zimmer®, Warsaw, Indiana). The groups were equally divided and randomized by hazard. For clinical evaluation, the Short Form-36 and Knee Society Score were obtained. For the radiological assessment mediCAD® Classic, a digital measurement system, was used. The aim of the study was the comparison of results after 3 months. Results. 2 patients refused any further participation, and 5 cases required a switch to a conventional alignement technique intraoperatively due to technical problems. Average BMI and average age did not differ in both groups. Surgical time in the iASSIST™ group amounted to 100 minutes, in the conventional group to 76 min. Postoperative functional outcomes were statistically insignificant, showing slight improvements of the Combined Knee Society Score, Knee Society Knee Score, and Knee Society Function Score favouring the iASSIST method, and slight improvements of knee flexion. Short Form-36 physical scales slightly favoured the conventional method but not significantly. The mean deviation from neutral mechanical axis was 1.68°±1.9° within the iASSIST group, and 2.73°±2.1° within the conventional TKA group. Conclusion. IASSIST™ is a valuable computer navigation system. The 5 technical troubles were due to the learning curve. The clinical results after 3 months did not differ significantly, the radiological assessment showed a tendency of improved alignement in the iASSIST™ group

Aims

To determine the value of scoliosis surgery, it is necessary to evaluate outcomes in domains that matter to patients. Since randomized trials on adolescent idiopathic scoliosis (AIS) are scarce, prospective cohort studies with comparable outcome measures are important. To enhance comparison, a core set of patient-related outcome measures is available. The aim of this study was to evaluate the outcomes of AIS fusion surgery at two-year follow-up using the core outcomes set.

Aims

Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes.

The complex structural arrangement of bone gives rise to anisotropic, rate-dependent failure behaviour, which varies significantly depending on tissue composition and architecture. This presents significant challenges in the development of orthopaedic surgical cutting instruments, which are required to generate sufficient forces to penetrate bone tissue, while minimizing the risk of thermal and mechanical damage to the surrounding environment. Currently, instrument designers rely heavily on empirical-based strategies to understand tool-bone interactions, with significant amounts of prototyping and validation experiments required throughout the design process. The aim of this study is to develop an experimentally-validated predictive computational model of orthopaedic cutting processes in three dimensions to understand the role of various cutting parameters on cutting forces and chip formation. An experimental model of orthogonal cutting was developed, whereby an adaptable cutting tool fixture driven by a servo-hydraulic uniaxial test machine was used to carry out high-rate cutting tests on Sawbone® trabecular bone analogues. A three-dimensional computational model was also developed using Abaqus/Explicit. The constitutive model describing material behaviour considers strain-rate and pressure-dependant yield behaviour using a Drucker-Prager elastic-plastic damage model, with Strain-hardening and rate-dependent model constants determined through dynamic uniaxial high-strain rate compression tests of material cubes. An excellent correlation between experimental and computational models was found, with the computational model accurately predicting tool cutting forces and chip development ahead of the tool during the cutting process. It was identifying that lower tool rake-angles resulted in the formation of larger discontinuous chips and higher cutting forces, while higher rake angles tended to lead to more continuous chip formation and lower cutting forces

Aims

A growing number of fractures progress to delayed or nonunion, causing significant morbidity and socioeconomic impact. Localized delivery of stem cells and subcutaneous parathyroid hormone (PTH) has been shown individually to accelerate bony regeneration. This study aimed to combine the therapies with the aim of upregulating fracture healing.

Introduction. Anterior ankle arthroscopy currently provides the best chance of restricting local anatomy damage during ankle surgery. The anterior working area (AWA) of the ankle is restricted by the Dorsalis Pedis Artery (DPA) and the extensor muscle tendons when the procedure is conducted both in dorsiflexion and plantarflexion. During surgery, iatrogenic damage to the DPA can lead to the formation of a pseudoaneurysm, which can be difficult to identify intraoperatively. Our study investigates whether dorsiflexion or plantarflexion provides variability in the movement of the DPA to determine the positions at which anterior ankle arthroscopy provides the greatest anterior working area (AWA) without causing vascular damage. The current study expects the distance of the DPA from the inferior border of the medial malleolus (IBMM) (ankle joint) to be greater on ankle dorsiflexion than in ankle plantarflexion. Materials and Methods. Twelve cadaver ankles embalmed with a mixture of phenol and glycerol, allowing greater motion, were dissected to access the DPA. The ankles, while in a distracted position (in accordance with common surgical practice), were forced into dorsiflexion from a plantarflexion position at 5° intervals. The distance between the IBMM and the DPA was measured at the 5° intervals. Results. The mean amount of ankle flexion achieved was 24.58° (Range = 20–35). All twelve ankles showed positive range of movement (ROM) anteriorly from the IBMM with a mean ROM of 3.58mm (SE = 0.29mm) dorsiflexion. Discussion and Conclusion. Anterior movement of the Dorsalis Pedis Artery during dorsiflexion puts it at a lower risk of iatrogenic damage in a dorsiflexed position compared to plantarflexion. The increased AWA allows the surgeon more manoeuvrable space, possibly allowing the use of larger diameter surgical instruments

Aims

Current guidelines consider analyses of joint aspirates, including leucocyte cell count (LC) and polymorphonuclear percentage (PMN%) as a diagnostic mainstay of periprosthetic joint infection (PJI). It is unclear if these parameters are subject to a certain degree of variability over time. Therefore, the aim of this study was to evaluate the variation of LC and PMN% in patients with aseptic revision total knee arthroplasty (TKA).

This paper illustrates the concept of a versatile surgical assistance system which combines an optical navigation system and a robotic arm. The integrated system offers precise positioning and guiding of surgical instruments according to pre-operative planning. A unique feature results from its capability to track small motions of the patient in real time, eliminating the need to rigidly fix the anatomical structure to be operated. The modular system architecture facilitates the adaptation of a common basic hardware platform to various surgical applications by adding associated software modules as well as appropriate surgical tools mounted to the robotic arm. The arm can be regarded as a controlled machine actuator of a navigation system. Its operation is mainly controlled by interactive operating modes which are based on a versatile haptic interface. The system supports the surgeon in those parts of a procedure where human skills are limited, but always lets him take full control, for example by directly grasping and moving the arm at its wrist if he wants to push the arm aside

The ability to reliably balance a total knee replacement during surgery eliminates a number of postoperative issues often leading to recurrent joint pain and lower than expected clinical outcomes. Over the past few years a surgical instrument has been available to surgeons performing primary TKA’s to enhance their surgical ability to develop flexion space balance by customizing femoral rotation by developing equal relative forces in the medial and lateral femoral-tibial compartments instead of using rotational anatomic landmarks. Since this concept deviates from the current practice of using anatomic or “boney” landmarks, as in the TEA or AP axis to develop a balanced flexion space with femoral rotation, this study design evaluated the variation in femoral rotation between the force balanced rotation and the conventional external rotation developed from the TEA and AP axes. Using the premise from previous studies that; clinical instability presents itself when the flexion space is asymmetric by more than three degrees, data was analyzed on 50 total knee patients to establish the rotational difference between the force balanced rotation and the rotation using the two conventional axes. Computer navigation was used as the measuring tool in this study. The study results showed that flexion space asymmetry would have been greater than the targeted three degrees in 38% of the knees in the study when utilising conventional anatomic reference based femoral rotation. The force balanced rotation created additional external rotation from a half to three degrees in these knees, improving patellar tracking. Based on previous work evaluating laxity in total knee patients, the reliability offered by force sensing technology appears to improve the surgeon’s operative ability to balance a reconstructed knee within three degrees of symmetry in flexion. This new technique appears to improve reported postoperative complications associated with instability in a reconstructed total knee. Further studies utilizing CT scan data to validate the actual femoral rotation and clinical outcome studies are warranted to examine this potential improvement to clinical outcomes in primary TKA’s

In recent years 3D preoperative planning has become increasingly popular with orthopaedic surgeons. One technique that has shown to be successful in transferring this preoperative plan to the operating room is based on surgical templates that guide various surgical instruments. Such a patient-specific template is designed using both the 3D reconstructed anatomy and the preoperative plan and is then typically produced via additive manufacturing technology. The combination of a preoperative plan and a surgical template has the potential to result in a more accurate procedure than an unguided one, when the following three criteria are met: the template needs to achieve a stable fit on the surgical field, it needs to fit in a unique position, and the surgeon needs to be able to determine the correct, planned position during the surgery. When the template fails one of these conditions, it can be used incorrectly. Consequently the process could result in an inaccurate outcome. This research focuses on modelling the stability of a surgical template on bone. The relationship between the contact surface of the template and the resulting stability is investigated with a focus on methods to quantify the template stability. The model calculates a quality score on the designed contact surface, which reflects the likelihood of positioning the template on the bone in a stable position. The model used in this study has been experimentally validated to verify its ability to provide a reliable indication of the template stability. This was analysed using finite element analysis where multiple templates and support models with different contact surface shapes were created. The application of forces and moments in varying directions was simulated. Stability is then defined as the ability of a template to resist an applied force or moment. The displacements of the templates were computed and analysed. The results show a minimal displacement of less than 0.01 mm and a maximal displacement larger than 10 mm. The former is considered to be a very stable template design; the latter to be very unstable and hence, would result in an insecure contact. The geometry of the contact surface had a clear influence on the template stability. Overall, the coverage of curvature variations improved the stability of the template. The displacements of the different finite element simulations were used as criterion for ranking the tested template designs according to their stability on their corresponding model surface. This ranking is then compared to that resulting from the quality score of the stability model. Both rankings showed a similar trend. This evaluation phase thus indicates that the developed stability model can be used to predict the stability of a surgical template during the preoperative design process

We share our experiences in designing a complete simulator prototype and provide the technological basis to determine whether an immersive medical training environment for vertebroplasty is successful. In our study, the following key research contributions were realised: (1) the effective combination of a virtual reality surgical simulator and a computerised mannequin in designing a novel training setup for medical education, and (2) based on a user-study, the quantitative evaluation through surgical workflow and crisis simulation in proving the face validity of our immersive medical training environment. Medical simulation platforms intend to assist and support surgical trainees by enhancing their skills in a virtual environment. This approach to training is consistent with an important paradigm shift in medical education that has occurred over the past decade. Surgical trainees have traditionally learned interventions on patients under the supervision of a senior physician in what is essentially an apprenticeship model. In addition to exposing patients to some risk, this tends to be a slow and inherently subjective process that lacks objective, quantitative assessment of performance. By proposing our immersive medical simulator we offer the first shared experimental platform for education researchers to design, implement, test, and compare vertebroplasty training methods. We collected feedback from two expert and two novice residents, on improving the teaching paradigm during vertebroplasty. In this way, this limits the risks of complications during the skill acquisition phase that all learners must pass through. The complete simulation environment was evaluated on a 5-pt Likert scale format: (1) strongly disagree, (2) disagree, (3) neither agree nor disagree, (4) agree, and (5) strongly agree. When assessing all aspects of the realism of the simulation environment, specifically on whether it is suitable for the training of technical skills team training, the participating surgeons gave an average score of 4.5. Additionally, we also simulated a crisis simulation. During training, the simulation instructor introduced a visualisation depicting cement extravasation into a perivertebral vein. Furthermore, the physiology of the computerised mannequin was influenced by the instructor simulating a lung embolism by gradually lowering the oxygen saturation from 98% to 80% beginning at a standardised point during the procedure. The simulation was stopped after the communication between the surgeon and the anaesthetist occurred which determined their acknowledgment that an adverse event occurred. The realism of this crisis simulation was ranked with an average score of 4.75. To our knowledge this is the first virtual reality simulator with the capacity to control the introduction of adverse events or complication yielding a wide spectrum of highly adjustable crisis simulation scenarios. Our conclusions validate the importance of incorporating surgical workflow analysis together with virtual reality, human multisensory responses, and the inclusion of real surgical instruments when considering the design of a simulation environment for medical education. The proposed training environment for individuals can be certainly extended to training medical teams

Introduction. Total Knee Replacement (TKR) is a highly effective treatment providing pain relief and improved function to patients experiencing advanced stage osteoarthritis. Tray fit or bone coverage is a critical design feature for both cemented and cementless designs affecting stability, load transfer and potential for infection. Many authors have attempted to characterise the relationship between the profile of the proximal tibia and gender and ethnicity. 1–3. As a consequence, a number of manufacturers have commercialised devices designed for specific gender and racial demographics. This study was initiated to compare the effect of the fixed minimum tibial resection depth prescribed by existing surgical instruments with that of a proportionate resection based on the size of the tibia. Method. A dataset consisting of 30 donor scans from a US cadaver tissue bank (ScienceCare, Memphis, US) was used for this study. The dataset consisted of 12 male and 18 female specimens. Due to the limited view of the diaphysis for most scans, the natural slope of the lateral compartment was used as a guide for orienting the resection. All scans were resected with a 3° posterior slope. For the first part of this study, an equal mediolateral (ML) resection of 9.5 mm, reflecting the minimum resection for the Unity TKR tibia (Corin, UK), was performed on all specimens (Figure 1). Following this, two proportionate resection depths (13.5 mm and 6.7 mm) were calculated based on the ML relationship between the smallest and largest available Unity components (59.5 mm: 84.5 mm). Two further resection depths (11.3 mm and 8.0 mm) were calculated based on a mid size (71.0 mm). Three resection depths (8.0 mm, 9.5 mm & 11.3 mm) were applied to four medium sized specimens. In addition to this two larger specimens were resected at 9.5 mm and 13.5 mm and two smaller specimens at 6.7 mm and 9.5 mm. A grid was applied to all cut surfaces and oriented using the posterior axis. The cut surface was divided based on lines drawn at 10%, 25%, 50%, 75% and 90% of the overall ML dimension and 10%, 25%, 50%, 75% and 90% of the overall anteroposterior (AP) dimension. Measurements were taken from the medial side and recorded from the points at which lines intersected the external profile of the cut tibia (Figure 2). Results. Results were presented as percentages relative to the AP and ML enabling the generation of 2D curve plots of the proposed profile (Figure 3). Discussion. Results from the fixed resection (9.5 mm) data depicted a good trend (R. 2. = 0.71–0.72) for the progression of the anterior profile as the tibia size increases. Similarly as the resection depth increased the same trend was observed. A weaker trend of R. 2. = 0.5 was also evident for the posterior profile. This methodology was applied to the development of the Unity tibia size range to optimise bone coverage and strain distribution

Many reports show good results following procedures, such as intervertebral body fusion using cage or total disc replacement, that restore adequate disc height. However, there have been no references regarding the range of normal lumbar disc height in Korean adults which can be used as a standard for the implant size. The purpose of our study is to measure the lumbar disc height on radiographs in normal Korean. 132 subjects (age range 20 to 40 years) who had no previous history of low back pain and no significant finding on physical examination were enrolled. Plain lateral lumbar spine radiograph in supine position were taken. Intervertebral disc heights were measured at anterior, middle and posterior portion of each lumbar disc. The average magnification rate was 115%, and the disc heights were corrected by the magnification rate in each segment. Lumbar disc height showed cranio-caudal pattern in both male and female groups. L4–5 disc heights were highest at anterior, middle and posterior portion in male. L4–5 disc heights were highest at middle and posterior portion in female. L5-S1 disc height was highest at anterior portion in female, but there was no statistically significant difference between L4–5 and L5-S1 disc height at anterior portion. There was no significant difference in disc height between male and female except anterior portion of L1–2 and L2–3 disc. Statistically significant decrease in disc height was not presented in overweight person at all measured site in male and female except posterior portion of L1–2 disc in male. This research is meaningful in that it is an attempt to provide a reference value of lumbar disc height in Korean adults, and the measured values may also be useful in manufacturing Korean modeled artificial lumbar disc prosthesis or surgical instruments for lumbar interbody fusion

INTRODUCTION. Rotational malalignment of the components in total knee arthroplasty has been linked to patellar maltracking, improper soft tissue balance, abnormal kinematics, premature wear of the polyethylene inlay, and subsequent clinical complications such as anterior knee pain (Barrack et al., 2001; Zihlmann et al., 2005; Lakstein at al., 2010). This study investigates an innovative image-based device that is designed to be used along with an intraoperative Isocentric (ISO-C) 3D imaging C-arm, and the conventional surgical instruments for positioning the femoral component at accurate rotational alignment angles. METHODS. The new device was tested on 5 replica models of the femur (Sawbones). Zimmer NexGen total knee replacement instruments were used to prepare the bones. After making the distal transverse cut on the femurs, the trans-epicondylar-axis (TEA) were defined by a line connecting the medial and lateral epicondyles which were marked by holes on the bone models. The 4-in-1 cutting jig was placed and pinned to the bones with respect to the TEA considering 5 different planned rotational alignments: −10°, −5°, 0°, +5°, and +10° (minus sign indicating external and plus sign internal rotation). At this point, the jig was replaced by the alignment device using the head-less pins as the reference, and subsequently an Iso-c 3D image of the bone was acquired using Siemens ARCADIS Orbic C-arm. The image was automatically analyzed using custom software that determined the angle between the TEA and the reference pins (Fig 1). The difference between the angle read from the device and the planned angle was then used to correct the locations of the reference pins through a custom protractor device. Preparation of the bone was continued by placing the 4-in-1 jigs on the newly placed pins. Three-dimensional images of the bones after completion of the cuts were acquired, and the angle between the final cut surface and the TEA was determined. RESULTS. The results are listed in Fig 2. The rotational angle read from the image-based device showed misalignments in the range of 0.53° to 5.94° (RMS error=3.67°). After alignments were corrected, the final cut accuracy was in the range of 0.3° to 0.74° (RMS error=0.5°). DISCUSSION. The introduced device was very accurate (0.5°) in correcting the rotational alignment of the femoral component. The range of errors for defining the boney landmarks through palpation and visualization is expected to be much larger than was observed in this work (RMS error =3.67°), due to soft tissue obstructions and time pressure during surgery. This would highlight the value of the device even more. The introduced technology is expected to add about 5 to 10 minutes to the surgery at a safe radiation dose comparable to a round transatlantic flight. The surgeon and staff can keep a safe distance during the short imaging time. CONCLUSION. The introduced device provides a fast and safe tool for improving component alignments in total knee arthroplasty

Many surgical techniques based on a distal osteotomy are used for the treatment of the symptomatic hallux valgus. We review the results of percutaneous distal osteotomy retrospectively. Between 1998 and 2003, 52 patients were operated on using a distal osteotomy for symptomatic hallux valgus. We investigated 35 females and nine males for a mean follow-up time of 4.6 years. We performed a percutaneous distal osteotomy (PDO) with a 2-mm Kirschner wire. Radiological analysis consisted of measuring the hallux valgus angle (HV) and the angle between the first and the second metatarsal (M). Clinical evaluation was performed with the AOFAS scale. Good bony contact was achieved and all the osteotomies united and no aseptic necrosis was found. According to the questionnaire, the pre-operative AOFAS score was 44.3 and 92.5 at the follow-up examination. Radiological analysis showed that the pre-operative HV angle was 13.7° and 9.8° at follow-up. The pre-operative M angle was 24.1° and 13.6° at follow-up. The PDO technique gives good results at a mean follow-up of 4.6 years. The positive aspects of this technique are: short surgical time, low incidence of complications and high patient compliance. A single 2-mm Kirschner wire is enough to achieve adequate stabilisation of the osteotomy, is less expensive than other surgical instruments for hallux valgus and is very easy to remove

Sufficient primary stability of the acetabular cup is essential for stable osseous integration of the implant after total hip arthroplasty. By means of under-reaming the cavities press-fit cups gain their primary stability in the acetabular bone stock. These metal-backed cups are inserted intra-operatively using an impact hammer. The aim of this experimental study was to obtain the forces exerted by the hammer both in-vivo and in-vitro as well as to determine the resulting primary stability of the cups in-vitro. Two different artificial bone models were applied to simulate osteoporotic and sclerotic bone. Polymeth-acrylamid (PMI, ROHACELL 110 IG, Gaugler & Lutz, Germany) was used as an osteoporotic bone substitute, whereas a composite model made of a PMI-Block and a 4 mm thick (cortical) Polyvinyl chloride (PVC) layer (AIREX C70.200, Gaugler & Lutz, Germany) was deployed to simulate sclerotic bone. In all artificial bone blocks cavities were reamed for a press-fit cup (Trident PSL, Size 56mm, Stryker, USA) using the original surgical instrument. The impactor of the cup was equipped with a piezoelectric ring sensor (PCB Piezotronics, Germany). Using the standard surgical hammer (1.2kg) the acetabular cups were implanted into the bone substitute material by a male (95kg) and a female (75kg) surgeon. Subsequently, primary stability of the implant (n=5) was determined in a pull-out test setup using a universal testing machine (Z050, Ziwck/Roell, Germany). For validation the impaction forces were recorded intra-operatively using the identical press-fit cup design. An average impaction force of 4.5±0.6kN and 6.3±0.4kN using the PMI and the composite bone models respectively were achieved by the female surgeon in vitro. 7.4±1.5kN and 7.7±0.8kN respectively were obtained by the male surgeon who reached an average in-vivo impaction force of 7.5±1.6kN. Using the PMI-model a pull-out force of 298±72N and 201±112N were determined for the female and male surgeons respectively. However, using the composite bone model approximately half the pull-out force was measured for the female surgeon (402±39N) compared to the male surgeon (869±208N). Our results show that impact forces measured in-vitro correspond to the data recorded in-vivo. Using the osteoporotic bone model the pull-out test revealed that too high impaction forces affect the pull-out force negatively and hence the primary implant stability is reduced, whereas higher impact forces improve primary stability considerably in the sclerotic bone model. In conclusion, the amount of impaction force contributes to the quality of the obtained primary cup stability substantially and should be adjusted intra-operatively according to the bone quality of each individual patient

Introduction: In 1971, Cloward wrote that after anterior cervical surgery, dysphagia occurs in all patients and is due to pressure on the oesophagus by the retractors. Recent studies indicate that dysphagia occurs in 54% of patients at 1 month and 13.6 % at 2 years. Recurrent laryngeal nerve injury occurs in 15 – 23 % producing hoarseness in one third of these. The continuing frequency of these complications even in experienced hands suggests that a review of retractor design and consideration of new designs is worthwhile. Methods: A Medline search of unlimited years in English using terms: retractors, surgical instruments, development and history was performed. Described retractors and their design principles were reviewed and a novel principle identified from which an anterior cervical device was developed and tested. Results: The novel general principle states that superior retraction is achieved by combining fixation onto bone with variable rotation of the retractor blade. Bone stabilization within the wound provides optimal stability and mechanical advantage for retraction while variable rotation allows retraction or tissue relaxation. Excluding the ubiquitous handheld retractors which lack stability, 7 different designs of anterior cervical retractors have been described. Anecdotally self retaining retractors are the most commonly used, but to be stable they require equal bilateral tissue counterforce and tissues that do not stretch. They are thus doubly ill suited for the asymmetrical anterior approaches to the anterior cervical spine. In the new anterior cervical retractor a small internal frame is fixed to the spine using standard Caspar screws. The frame slides with distraction. Routine surgery including plating is carried out within the frame. The frame provides stable axes for the independently rotating medial and lateral retractor blades. Discussion: In the spine intermittent relaxation of retraction has recently been shown to reduce muscle injury and pain after lumbar surgery. This is the first retractor system that can be released without sacrificing stability or exposure. Despite numerous authors implicating cervical retractors as a source of complications there are few investigations and no studies investigating different designs. Rather than accepting or denying common complications we should investigate even our most familiar tools

The paper presents the design of a mechatronic assistance system which started from the novel concept to integrate an optical navigation system and a robotic arm, combining the specific advantages of each of the two components. The integrated system offers precise positioning and guiding of surgical instruments according to pre-operative planning. A unique feature results from its capability to track small motions of the patient in real time, eliminating the need to rigidly fix the anatomical structure to be operated. The robot arm can be regarded as a controlled machine actuator of a navigation system. Its operation is mainly controlled by interactive operating modes which are based on a versatile haptic interface. The system supports the surgeon in those parts of a procedure where human skills are limited, but always lets him take full control, for example by directly grasping and moving the arm at its wrist if he wants to push the arm aside. In 2003 several clinical trials have been performed to demonstrate the technical and medical feasibility of the approach. Our mechatronic assistance system has been world’s first system to support the implantation of the acetabular cup in robot assisted hip surgery. The next steps have been concentrated on further developments in some key areas. Improvements of the man-machine interface in order to make the operation of the system faster, easier, and more robust, extension of the system application also to the femoral part of total hip replacement, including support for resurfacing implants, investigation of novel tool systems for bone preparation and prosthesis implantation that fully exploit the advantages of mechatronic, slip-away-safe tool guidance, further improvements for less invasive operating techniques. It has turned out that apart from proving the basic system functionality it is a time consuming task to design all system components in a way that they are robust and easy to handle to be acceptable for daily clinical application. After a partial redesign of the system architecture presently the implementation of improved modules to support both the acetabular and the femoral part in total hip replacement surgery by the mechatronic assistance system is in progress

Introduction: Most surgeons agree on basic parameters defining a successful joint replacement procedure. However, the process of acquiring the skills to achieve this level of success on a reproducible basis is much less straightforward. In reality, it is generally not possible to impart surgical training without some level of risk to the patient, particularly if a particular trainee or procedure has a long learning curve. In an attempt to address these issues, we have developed a new computer-based training system to measure the technical results of hip and knee replacement surgery in both the operating room and the Bioskills Lab. Description of the System: This system utilizes Surgical Navigation technology combined with data analysis and display routines to monitor the position and alignment of instruments and implants during the procedure in comparison with a preoperative plan. For bioskills training, the surgeon develops a preoperative plan on a computer workstation using accurate 3D computer models of the bones and appropriate implants. The surgeon then performs the entire procedure using the cadaver or sawbone model. During the procedure, the position and orientation of the bones, each surgical instrument, and the trial components are measured with a three-dimensional motion analysis system. Through analysis of this data, the surgeon is able to view each step of the surgical procedure, the placement of each instrument with respect to each bone, and the consequences of each surgical decision in terms of the final placement of the prosthetic components When errors are detected in the implementation of the preoperative plan, the surgeon is able to replay each step of the procedure to examine the precise placement of each instrument with respect to each bone and the consequences of each surgical decision in terms of leg length, alignment and range-of-motion. Conclusions: This system allows us to measure the technical success of a surgical procedure in terms of quantifiable geometric, spatial, kinematic or kinetic parameters. It also provides postoperative feedback to the surgeon by demonstrating the specific contributions of each step of the surgical procedure to deviations in final alignment or soft tissue instability. This approach allows surgeons to be trained outside the operating room prior to patient exposure. Once these skills have been developed, the surgeon is able to operate freely in the operating room without the risks associated with traditional surgical training, or the expense associated with intraoperative Surgical Navigation. The value of this approach in the training and accreditation of orthopedic staff warrants further investigation

Introduction This abstract describes the development of an effective procedure for removing as much nucleus as possible from an intervertebral disc with minimal disruption to the annulus. The procedure was developed on cadaveric sheep discs which are well established as a model for human discs in studies of this kind. The purpose of the study was to develop a method for removing the nucleus as part of a laboratory study of nucleus replacement; however, it is also intended to guide the development of procedures for the removal of residual nucleus when indicated in surgical procedures that involve replacing the nucleus with synthetic materials. Methods All procedures were performed via a 3 mm trocar. Four procedures were compared: (I) unilateral approach using rongeurs alone, (II) unilateral approach using rongeurs followed by chymopapain, (III) bilateral approach using rongeurs alone and (IV) bilateral approach using rongeurs followed by chymopapain. Chymopapain was administered as a solution (30 units in 0.1 cm. 3. de-ionised water) to a disc at 37°C. For each procedure (I–IV) 14 discs were used. Results The percentages of nucleus removed were: (I) 34 ± 2%, (II) 41 ± 2%, (III) 52 ± 3% and (IV) 75 ± 8%; ANOVA showed a significant differences between the four sets of results (P < 0.05). Conclusions Significantly more nucleus is removed using a bilateral than a unilateral approach; significantly more nucleus is removed if chymopapain is used in addition to rongeurs. A brush is useful in removing strands of nucleus loosened by chymopapain. For the purpose of these experiments a bottle brush with nylon bristles was trimmed to an overall diameter of about 10 mm, so that it could be inserted into the nuclear cavity via the trocar. Design of a surgical instrument for this purpose would be guided by a preliminary risk analysis

Purpose of the study: Percutaneous osteosynthesis of scaphoid fractures remains a difficult technique which requires a long learning curve. Complications remain a problem, even in experienced hands of specialized surgeons. The purpose of this work was to study the potential contribution of fluoroscopic navigation for precutaneous screwing of the carpal scaphoid. Material and methods: Right and left arm anatomic specimens from ten subjects were sectioned at the elbow level. Both wrists from each subject were prepared and each of the scaphoids was fixed by percutaneous screwing using regular fluoroscopic guidance for one and the other with fluoroscopic navigation. The regular fluoro-scopic guidance technique was used for the first wrist, selected randomly. Fluoroscopic navigation was used for the other side to achieve strict fixation of the wrist in the ideal screwing position using a stable radiotranspar-ent and flexible device. Using a calibraton grid displayed on the fluoroscope screen the system software corrected for distortions of the fluoroscope image. Reflecting patches on the surgical instruments were recognized by the 3D optical localization system. This enabled a real time screen display of instrument movement. Resolution was sufficient to align the screw with the scaphoid axis and calculate the length of the screw. The resolution of the reformated digital images enabled real time screen display of instrument movement at a resolution which enabled pin insertion in the scaphoid axis. The length of the perforated screw inserted percutaneously over the pin was measured on the screen. Results and discussion: Unlike the regular screwing method and excepting the image acquisition time which can be achieved without exposing the operator, exposure time to radiation was zero with fluoroscopic navigation. The duration of the operation was longer with navigation because the instruments had to be calibrated and because a learning curve is required. The quality of the screw fixation assessed on plain x-rays, computed tomography, and photographs of the entire scaphoid then sectional along the major axis after removal was similar between the two methods. Conclusion: In conclusion, fluoroscopic navigation is a reliable technique which protects both the operator and the patient from radiation exposure. The technique remains to be standardized to shorten the learning curve, improve the navigation software, and develop a calibrated instrumentation before it can be used in routine clinical practice

The correct placement of the acetabular cup is the most challenging part within hip arthroplasty. For fulfilling the biomechanical requirements the three-dimensional position of the acetabular cup must be exactly adapted to the patient’s anatomy. The amount of acetabular cup malpositioning is still too high. CAS (Computer Assisted Surgery) in hip arthroplasty offers the opportunity to have an online feed-back concerning the exact 3-D position of the cup, the surgical tools, and the patient’s pelvis. Preoperatively the surgeon plans and records with the system’s software the optimum cup position, and size. Within the operation theatre optoelectronic tools serve to the CAS-system for tracking. By using these data, the CAS-system delivers real-time optical information about the 3-D position of the patient’s pelvis, the orientation of the surgical instruments (reamer, cup positioner), and the acetabular component. This allows the surgeon to navigate by these tools and to find the exact inclination, ante-version, and depth of the cup. From Mars until December 1999, we could perform 80 CAS-system assisted cup placements. All 80 patients (80 hips) were operated on because of severe osteoarthritis. All operations were performed by one surgeon (KB). The average increase of the operation time was 20 minutes resulting an average of 70 minutes. The average loss of blood was 630 ml. No perioperative specific complications did occur. The therapeutic regimen had not to be changed in any case. There were no cases of early hip dislocation. Other early postoperative complications did not occur either. By postoperative CT scans we could evaluate the accuracy of the computer assisted cup placement. The deviation of the postoperative cup position from the preoperative planing was each 3–5° in average. This method is a reliable support for the surgeon to be able to implant the acetabular cup exactly in the planned position

Introduction The first ceramic knee implant in a human patient was used by Dr. G. Langer of the Orthopaedic Clinic at the University of Jena, Germany in 1972. In 1980, Drs. Oonishi and Hasegave began using a alumina femoral component on a polyethylene tibial component. These early attempts all involve the search for solutions to the wear and degradation problems. The application of ceramics was limited by:. polyethylene wear and degradation. demand of thin components. Excellent Scratch resistance AMC Ceramics is much harder than most surgical instruments. In comparison, metal components are easily scratched and damaged during surgery with the consequence of increasing wear. Surface quality: Surface quality of the articulation surfaces components made from AMC Ceramics provide excellent articulation surfaces. Low Friction: Knee Components made of AMC Ceramics show a low coefficient of friction. The resulting frictional forces on the prostheses are lower and offer the option for a reduction of aseptic loosening. Low Allergic Potential: Ceramics are generally not considered as elicitors of allergic reactions. Hypersensitive reactions – especially to nickel – in total joint replacement are discussed as one possible reason for postoperative syndromes. Surface Lubrication: AMC is a material with a very good surface lubrication capability. A low wetting angle is exhibited by the material. Conclusion: Knee implants have become an area of great interest in the past years. For more than 10 years ceramic femoral components are used in Japan. Published follow-up data in scientifically journals are promising. Leading orthopaedic surgeons are interested in this option today to reduce the risk of pitting and delamination of Polyethylene. Material improvements are required for young active patients and nickel sensitive patients. The novel AMC Ceramic offers a solution to minimise the allergic and wear related problems of knee implants. New concepts on the basis of hard on hard combination are technically already realised. The use of knee endoprosthesis with ceramic on ceramic combination is an option for ”zero” wear bearings in the knee

The most common reason for possible complications after total hip replacement (THR) surgery is improper positioning of the implant components within the hip joint. Systems for computer assisted planning and navigation during THR have been developed. However, these established modules focus on the acetabular implant component only; disrespecting the fact that proper implant functioning relies upon correct placement of both components relative to each other. Therefore, we developed an extension to the existing CT-based SurgiGATE-Prosthetics system (Medivision, Oberdorf, Switzerland) for planning and placing of the acetabular component to give the surgeon a tool, which can help him/her to also plan and insert the femoral implant. Preoperatively, the appropriate size and position as well as the orientation of both implants components were planned. Following navigated cup placement a dynamic reference base (DRB) was fixed to the thighbone and the registration procedure was executed. For the preparation of the femoral cavity a modular PPF rasp system (Biomet-Merck, Darmstadt, Germany) was developed. All surgical action was visualised graphically within the patient’s image data. In addition, the surgeon was provided with real-time information about the depth of tool insertion, antetorsion angle, varus/valgus deviation, and the postoperative change in leg length and lateralisation of the hip joint. After extensive validation and accuracy analyses performed on plastic models the presented system was used during one operation. An extended clinical study is currently being started. We expect that the developed application will help the surgeon to better plan the appropriate size and position of the both parts of a hip endoprosthesis and will supply intraoperative feedback of the position of the surgical instruments relative to the patients’ anatomy and to the preoperative plan. Safer and more accurate placement of the implants components during free-hand THR surgery may be expected from this technology

Background. Currently existing optical navigation systems have ergonomic disadvantages such as size, the “line of sight” problem and extended registration procedures. The operation room becomes crowded by additional installations and competitive supporting devices around the patient. These points reduce and limit the acceptance of navigation systems for further applications. But especially for surgical quality management, navigation systems have a high potential as objective measurement systems. Method. A miniaturised measuring and navigation system, which is directly fixed at the surgical tool, could overcome these limitations and fulfil the requirements demanded by current and future operation rooms. Minimising the distance between situ and camera promises an increased accuracy, a reduced “line of sight problem,” intuitive handling and one coordinate transformation (Tool2DRB) less. However, such a setting reduces the navigation working space available, needs a sterile system, a new marker design and special requirements for the cameras. The developed prototypes were tested in vitro using Synbones™ and ex vivo at anatomical specimen. Following surgical pilot applications were defined and considered during the studies: maxillofacial restoration osteotomy, hip replacement and unicondylar knee replacements (UKR). Special emphasis was placed on measured and recorded accuracy and miniaturised hardware. Results. Several miniaturised measuring system prototypes with high resolution cameras mounted directly onto a surgical instrument have been developed and tested. One prototype includes a laser device which is used in combination with the cameras to register 3D surfaces like the rotational centre of an acetabular cup from a prosthetic hip joint. Other prototypes demonstrate the miniaturising aspect of this development and their ergonomic advantages. Corresponding algorithm and software developments include calibration, marker identification, network components and surgical planning modules. Hard and software components have been tested for UKR application in an ex vivo study. Clinical trials for maxillofacial restoration osteotomy are prepared at the University Hospital Basel. The accuracy of the presented systems was evaluated in vitro with two setups. After intrinsic and extrinsic camera calibration with a 3D calibration specimen, the accuracy (RMS) of a single point of the 3D point coordinates of the calibration specimen could be determined with 0,020 mm in z-axis and 0,010 mm in x/y-axis. In another setup the accuracy was measured in 3D with a fixed camera system and two markers rigidly fixed together. The marker system was moved around working space. The repeat accuracy of the distances between the two markers was 0,025 mm (RMS). Discussion. The total development of the miniaturised measuring system, consisting of a video system, an optional laser scanner, calibration, image processing algorithms and planning modules was successful. The current prototype has proved to be accurate and usable. Users (surgeons) and suppliers of surgical implants, who have been exposed to the system, have expressed their keen interest, as it opens up new applications and fulfils their needs for improved ergonomics and smarter, cost reducing work flows. But of course there is still potential for improvements. In the next iteration of the development process, the usability and accuracy of the system could still be improved. The currently used optics limit the possible accuracy because the aperture of F = 2.8 is too large for photogrammetric applications and its optics distortions are too large. Therefore it will be exchanged by an optimised solution. Another optimisation target is the camera electronics. The currently used ones cannot be synchronised, which limits the usability, respectively reduces the accuracy, if it is moved during a measurement shot

Formal surgical skill assessment and critical path analysis are not widely used in orthopaedic surgical training due to the lack of technology for objective quantification, reliability, and the discrimination insensitivity of existing methods. Current surgical skill assessment methods also require additional instrumentation, cost and time. Such problems can be overcome by a novel method that records the motion of surgical instrumentation for the purposes of documentation, surgical-skill assessment, and safety analysis. This method uses an existing computer-aided-orthopedic-surgery (CAOS) navigation system and does not compromise its functions of real-time tracking, rendering, or simulation. The stored data allows realistic playback in 3D of the complete bone cutting/refining process. This concept and its sensitivity were previously tested and validated using a robotic arm as a reliable actuator for a surgical instrument moving in controlled paths. In this study, the system was used to evaluate the surgical skills of actual orthopaedic residents in a hospital/lab setting. Two chief orthopaedic surgery residents participated in the experiment. Each one cut all five distal cuts on four synthetic (right) femurs to accommodate the same femoral implant using NoMiss, an in-house built system for Navigated Freehand bone cutting. The motion of the surgical saw was recorded in real time by NoMiss during the whole procedure, but the real purpose of the experiment (and the recording) was not revealed to the residents until the end of all tests. Based on the data recorded by the navigation system, the following parameters were analyzed: cutting time, area-of-the-cut/time ratio, trajectory of the saw, errors in distance off the plane as well as errors in roll and pitch angles. While no significant difference among the two subjects was found in bone cutting time (mean 531s vs. 642s, p=0.099), subject 1 (S1) was faster than subject 2 (S2) in total time, which included cutting, reshaping of the bone, and implantation (mean 719s vs. 958 s, p=0.035). Area-of-the-cut/time ratio revealed higher (not significant) proficiency for S1 compared to S2 (mean 16 mm2/s vs. 13 mm2/s, p=0.084). Nevertheless considering individual cuts, there was significant difference in the posterior chamfer cut (mean 9 vs. 5 mm2/s, p=0.015). The analysis of the trajectory of the saw showed less conservative motion (and less consistency) for S1 than for S2 (average total length of trajectory 8.6m (sd=2.1m) vs. 8.1m (sd=0.4m), as well as larger paths in between cuts (average 39% vs. 33% of the total trajectory). The system/method was able to characterize different subjects without additional instrumentation, cost, time, awareness of or distraction to the user. Slightly better performance was detected for S1 compared to S2 presumably signifying superior skills. The main differences in this case appeared in the cutting of the chamfers, which might be considered the trickiest of the distal cuts in a navigated freehand cutting environment. A larger number of subjects with a wide level of expertise should be analyzed under similar conditions to establish quantitative acceptance limits (e.g. numerical determination for pass/fail criteria)

Aims: To determine the feasibility and short-term outcome after Total Hip Arthroplasty through a limited anterior approach. Methods: Done between April 2003 and August 2004, 100 patients (102 hips) requiring primary total hip arthroplasty comprise this study. A modification of the Smith-Peterson anterior approach developed by Robert Judet was used requiring a special fracture table (Pro-Fx, OSI) but no unique surgical instruments. A single incision was used; the natural interval between the sartorius and rectus muscles medially and the tensor muscle laterally was developed. SL-Plus stems and Plus-MPF or Encore cups were used in all cases. This series is entirely unselected: no patients were excluded because of size or body habitus. One third of the patients had a Body Mass Index greater than 30 (obese); the maximum BMI was 45.6. One third had type C bone and nearly one tenth were category 3 anesthetic risks. Average age was 72 (range 39 to 90). A naive definition of “minimally invasive” is met: the average incision length was 9.5 centimeters (range 6.5 to 13). Result: Time for the surgical procedure reduced from three and one half hours for the first arthroplasty to 70 minutes between the 15th and 20th operation. Previously, hospital stay averaged over 5 days using a conventional posterior approach; average stay with the “minimal” approach was less than 3 days. Only 20% of these patients required an intermediate care facility prior to returning home. There have been three complications requiring readmission: 1 dislocation, 1 unstable acetabulum, and 1 superficial wound breakdown. There has been a total of 3 dislocations-all within 4 days of surgery, none recurrent. One DVT has been detected. Conclusions: The early experience, “learning curve” and technical complications of the modified Smith-Peterson anterior approach are emphasized. Given the consistently reported 95% to 98% success rate of conventional hip arthroplasty it is imperative to make any change with foresight and then to document the consequence of that change. Surgical technique should not absolutely dictate implant choice. This report sheds light on the very early result of a change only to the surgical approach to total hip arthroplasty

Aim: The objective of this study was to compare the initial stability of an uncemented curved long stem femoral component (ABR, Zimmer, Warsaw Indiana) implanted using conventional broaching to an uncemented ABR implanted as a revision using morselized compacted allograft to fill a circumferential proximal bone defect. Materials and Methods: Primary: Eight fresh frozen human femurs were implanted with correctly sized ABR stems without cement using standard surgical instruments and 1mm distal overreaming. The implant was loaded cyclically at 3 hz on a MTS servohdraulic materials test frame in a direction representing the peak force of the stance phase of the gait (2.5 X body weight). A 3-dimensional motion measurement device with six linear variable transformers measure the relative motion between the bone and the prosthesis with an accuracy of 0.5μm. The contruct was loaded in ten cycle increments until the component was seated and then recoverable motion was recorded over a further ten loading cycles. Revision: In the revision case bone loss was modelled by removing all the cancellous bone from the proximal femur with 1mm distal overreaming. Morselized bone graft was impacted into the defect using specially prepared smooth tamps shaped to the geometry of the ABR stem. The original prosthesis was then reimplanted without the use of cement. The seating and testing cycles were repeated. Primary and revision vectors were compared using a paired students t – test. Results: There was no statistically significant difference in the magnitude of the resultant vector of the 3 translational components of the micro motion between the two methods of implantation (p=0.19). Conclusions: Initial stability of a cementless femoral implant is a requirement for bone ingrowth. The use of compacted morsellized allograft in a revision Total Hip Arthroplasty with a proximal circumferential defect can provide a stable bed for the implantation of an uncemented femoral component. The revised implant using the compacted allograft method was initially as stable as the primary implantation. This technique would be particularly applicable when the surgeon would like to avoid the use of cement in a revision setting. The use of this method for uncemented revision Total Hip Arthroplasty should be studied further in a clinical setting before it is advocated for widespread use

Aims

The primary aim of this study was to compare the postoperative systemic inflammatory response in conventional jig-based total knee arthroplasty (conventional TKA) versus robotic-arm assisted total knee arthroplasty (robotic TKA). Secondary aims were to compare the macroscopic soft tissue injury, femoral and tibial bone trauma, localized thermal response, and the accuracy of component positioning between the two treatment groups.

For any image guided surgery, independently of the technique which is used (navigation, templates, robotics), it is necessary to get a 3D bone surface model from CT or MR images. Such model is used for planning, registration and visualization. We report that graphical representation of patient bony structure and the surgical tools, inter-connectively with the tracking device and patient-to-image registration, are crucial components in such system. For Total Shoulder Arthroplasty (TSA), there are many challenges. The most of cases that we are working with are pathological cases such as rheumatoid arthritis, osteoarthritis disease. The CT images of these cases often show a fusion area between the glenoid cavity and the humeral head. They also show severe deformations of the humeral head surface that result in a loss of contours. These fusion area and image quality problems are also amplified by well-known CT-scan artefacts like beam-hardening or partial volume effects. The state of the art shows that several segmentation techniques, applied to CT-Scans of the shoulder, have already been disclosed. Unfortunately, their performances, when used on pathological data, are quite poor. In severe cases, bone-on-bone arthritis may lead to erosion-wearing away of the bone. Shoulder replacement surgery, also called shoulder arthroplasty, is a successful, pain-relieving option for many people. During the procedure, the humeral head and the glenoid bone are replaced with metal and plastic components to alleviate pain and improve function. This surgical procedure is very difficult and limited to expert centres. The two main problems are the minimal surgical incision and limited access to the operated structures. The success of such procedure is related to optimal prosthesis positioning. For TSA, separating the humeral head in the 3D scanner images would allow enhancing the vision field for the surgeon on the glenoid surface. So far, none of the existing systems or software packages makes it possible to obtain such 3D surface model automatically from CT images and this is probably one of the reasons for very limited success of Computer Assisted Orthopaedic Surgery (CAOS) applications for shoulder surgery. This kind of application often has been limited due to CT-image segmentation for severe pathologic cases and patient to image registration. The aim of this paper is to present a new image guided planning software based on CT scan of the patient and using bony structure recognition, morphological and anatomical analysis for the operated region. Volumetric preoperative CT datasets have been used to derive a surface model shape of the shoulder. The proposed planning software could be used with a conventional localisation system, which locates in 3D and in real time position and orientation for surgical tools using passive markers associated to rigid bodies that will be fixed on the patient bone and on the surgical instruments. 20 series of patients aged from 42 years to 91 years (mean age of 71 years) were analysed. The first step of this planning software is fully automatic segmentation method based on 3D shape recognition algorithms applied to each object detected in the volume. The second step is a specific processing that only treats the region between the humerus and the glenoid surface in order to separate possible contact areas. The third step is a full morphological analysis of anatomical structure of the bone. The glenoid surface and the glenoid vault are detected and a 3D version and inclination angle of the glenoid surface are computed. These parameters are very important to define an optimal path for drilling and reaming glenoid surface. The surgeon can easily modify the position of the implant in 3D aided by 3D and 2D view of the patient anatomy. The glenoid version/inclination angle and the glenoid vault are computed for each postion in real time to help the surgeon to evaluate the implant position and orientation. In summary, preoperative planning, 3D CT modelling and intraoperative tracking produced improved accuracy of glenoid implantation. The current paper has presented new planning software in the world of image guided surgery focused on shoulder arthroplasty. Within our approach, we propose, to use pattern recognition instead of manual picking of landmarks to avoid user intervention, in addition to potentially reducing the procedure time. A very important role is played by 3D data sets to visualise specific anatomical structures of the patient. The automatic segmentation of arthritic joints with bone recognition is intended to form a solid basis for the registration. The results of this methodology were tested on arthritic patients to prove that it is not just easy and fast to perform but also very accurate so it realises all conditions for the clinical use in OR

Introduction: Fluoroscopy is routinely used for real-time intra-operative localization of patient anatomy and surgical instrument positioning. Using this radiographic information the orthopedic surgeon inserts different implants into bone. Despite its utility, however, fluoroscopy does have disadvantages. The most notable is potential occupational radiation exposure. Conventional fluoroscopy usually provides only one plane at a time, whereas at least two planes are needed for optimal placement of an implant. By combining a standard C-arm fluoroscopy with computer aided surgical technology, radiation exposure can be eliminated and four different planes can be visualized simultaneously. This study presents data of preliminary clinical experience using this new technology. Material and methods: The Stealth Station Treatment Guidance Platform System by Medtronic was used. The calibration target was attached to a C-arm fluoroscope. The static reference arc which was attached to the patient and various surgical tools. All with affixed light emitting diodes (LEDs) which were seen by the Infra Red camera. After a short registration process in which the relevant anatomy images were acquired, the C-arm was withdrawn and the entry point to the operated anatomy was determined using the navigation capabilities of the system. During a period of six months, 31 patients underwent different surgical procedures in which a guided wire was used for: percutaneous fixation of unstable pelvis and hip fractures (13 patients), inserting and locking of an intrameduallry nail (12 patients), inserting pedicular screws (2 patients), or removing foreign-bodies or internal fixations (4 patients). In all cases the placement of the hardware was approved by conventional fluoroscopy as well. Results: Excellent correlation between the virtual fluoroscopic imaging and live fluoroscopy was observed, thus the placement of the wire in all cases was satisfactory and there was no need to change the position of the wire following the live fluoroscopic confirmation. The number of fluoroscopic buttoning was smaller than the average number in similar surgery using conventional fluoroscopy. Discussion: According to our preliminary clinical experience it seems that virtual fluoroscopy offers several advantages over conventional fluoroscopy while providing acceptable targeting accuracy. Our impression is that its saves fluoroscopic radiation exposure and improves exactness of the procedure. However, since currently only one reference arc can be detected at a time by the guidance system it can be used only in a stable anatomical situations (such as non-displaced fractures or pedicular screw placements). The use of better-oriented surgical instrumentation and more than one reference point detection will significantly improve the clinical potential of this method

Introduction: Fluoroscopy is routinely used for real-time intra-operative localization of patient anatomy and surgical instrument positioning. Using this radiographic information the orthopedic surgeon inserts different implants into bone. Despite its utility, however, fluoroscopy does have disadvantages. The most notable is potential occupational radiation exposure. Conventional fluoroscopy usually provides only one plane at a time, whereas at least two planes are needed for optimal placement of an implant. By combining a standard C-arm fluoroscopy with computer aided surgical technology, radiation exposure can be eliminated and four different planes can be visualized simultaneously. This study presents data of preliminary clinical experience using this new technology. Material and methods: The Stealth Station Treatment Guidance Platform System by Medtronic was used. The calibration target was attached to a C-arm fluoroscope. The static reference arc which was attached to the patient and various surgical tools. All with affixed light emitting diodes (LEDs) which were seen by the Infra Red camera. After a short registration process in which the relevant anatomy images were acquired, the C-arm was withdrawn and the entry point to the operated anatomy was determined using the navigation capabilities of the system. During a period of six months, 31 patients underwent different surgical procedures in which a guided wire was used for: percutaneous fixation of unstable pelvis and hip fractures (13 patients), inserting and locking of an intrameduallry nail (12 patients), inserting pedicular screws (2 patients), or removing foreign-bodies or internal fixations (4 patients). In all cases the placement of the hardware was approved by conventional fluoroscopy as well. Results: Excellent correlation between the virtual fluoroscopic imaging and live fluoroscopy was observed, thus the placement of the wire in all cases was satisfactory and there was no need to change the position of the wire following the live fluoroscopic confirmation. The number of fluoroscopic buttoning was smaller than the average number in similar surgery using conventional fluoroscopy. Discussion: According to our preliminary clinical experience it seems that virtual fluoroscopy offers several advantages over conventional fluoroscopy while providing acceptable targeting accuracy. Our impression is that its saves fluoroscopic radiation exposure and improves exactness of the procedure. However, since currently only one reference arc can be detected at a time by the guidance system it can be used only in a stable anatomical situations (such as non-displaced fractures or pedicular screw placements). The use of better-oriented surgical instrumentation and more than one reference point detection will significantly improve the clinical potential of this method

Aims

In the UK, fasciectomy for Dupuytren’s contracture is generally performed under general or regional anaesthetic, with an arm tourniquet and in a hospital setting. We have changed our practice to use local anaesthetic with adrenaline, no arm tourniquet, and perform the surgery in a community setting. We present the outcome of a consecutive series of 30 patients.

Aims

Inadvertent soft tissue damage caused by the oscillating saw during total knee arthroplasty (TKA) occurs when the sawblade passes beyond the bony boundaries into the soft tissue. The primary objective of this study is to assess the risk of inadvertent soft tissue damage during jig-based TKA by evaluating the excursion of the oscillating saw past the bony boundaries. The second objective is the investigation of the relation between this excursion and the surgeon’s experience level.

During the pandemic of COVID-19, some patients with COVID-19 may need emergency surgeries. As spine surgeons, it is our responsibility to ensure appropriate treatment to the patients with COVID-19 and spinal diseases. A protocol for spinal surgery and related management on patients with COVID-19 has been reviewed. Patient preparation for emergency surgeries, indications, and contraindications of emergency surgeries, operating room preparation, infection control precautions and personal protective equipments (PPE), anesthesia management, intraoperative procedures, postoperative management, medical waste disposal, and surveillance of healthcare workers were reviewed. It should be safe for surgeons with PPE of protection level 2 to perform spinal surgeries on patients with COVID-19. Standardized and careful surgical procedures should be necessary to reduce the exposure to COVID-19.

Continuous technical improvement in spinal surgical procedures, with the aim of enhancing patient outcomes, can be assisted by the deployment of advanced technologies including navigation, intraoperative CT imaging, and surgical robots. The latest generation of robotic surgical systems allows the simultaneous application of a range of digital features that provide the surgeon with an improved view of the surgical field, often through a narrow portal.

There is emerging evidence that procedure-related complications and intraoperative blood loss can be reduced if the new technologies are used by appropriately trained surgeons. Acceptance of the role of surgical robots has increased in recent years among a number of surgical specialities including general surgery, neurosurgery, and orthopaedic surgeons performing major joint arthroplasty. However, ethical challenges have emerged with the rollout of these innovations, such as ensuring surgeon competence in the use of surgical robotics and avoiding financial conflicts of interest. Therefore, it is essential that trainees aspiring to become spinal surgeons as well as established spinal specialists should develop the necessary skills to use robotic technology safely and effectively and understand the ethical framework within which the technology is introduced.

Traditional and more recently developed platforms exist to aid skill acquisition and surgical training which are described.

The aim of this narrative review is to describe the role of surgical robotics in spinal surgery, describe measures of proficiency, and present the range of training platforms that institutions can use to ensure they employ confident spine surgeons adequately prepared for the era of robotic spinal surgery.

Cite this article: Bone Joint J 2020;102-B(5):568–572.

To compare the number of airborne bacteria and particles under laminar airflow (LAF) versus turbulent airflow (TAF) with 100% and 50% reduced fresh air exchange during simulated total hip arthroplasty (THA). Two equally dimensioned operating rooms (OR) build in 2009 with modern ventilation systems of LAF and TAF respectively were used during 32 simulated THA-operations under four different ventilation conditions: LAF or TAF with either full (n=8+8) or 50% reduced (n=8+8) fresh air exchange volume. We followed a protocol controlling the complete perioperative setup including interior cleaning, sterile materials, OR-personnel procedures, surgical clothing, instruments and 50-minute surgical procedure on a full-sized dummy at 37°C. Microbial contamination was determined intra-operatively by ISO-validated Microbiological Active Sampler (MAS-100, Merck, 100 L/min) at two 10-minute intervals in 30 cm distance of the operating field. Blood-agar plates from each operation were incubated for 2 days at 35°C and the microbial concentration was determined by viable counting of colony-forming units (CFU) per m3 air. Furthermore airborne particulate (0,5–10 µm) was sampled with ISO-validated light scattering particle analyzer (MET-one, Beckman Coulter, 28,3 L/min) during the 50-minute surgical procedure (1,42 m3/operation). Large particle sizes (>5 µm) are correlated with microbial contamination (Stocks, 2010). According to standards large-sized particle number must not exceed a 2.900/m3-threshold for cleanroom operations. Microbial air concentration (mean CFU/m3 ±standard deviation) under LAF conditions with full and 50% reduced fresh air exchange were 0,4±0,8 and 0,4±0,4 respectively, whereas air contamination under TAF conditions were significantly higher with 7,6±2,0 and 10,3±8,1 (p<0,05). Large (>5 µm) airborne particulate (mean no./m3 ±standard deviation) under LAF conditions with full and 50% reduced fresh air exchange were 1.581±2.841 and 1.018±1.084 respectively, whereas particulate under TAF conditions were 7.923±5.151 and 6.157±2.439 respectively. Microbial air contamination was significantly lower under LAF ventilation compared to TAF during simulated THA under both full and 50% reduced fresh air exchange in modern operating theatres used in daily clinic. The number of particles measured under TAF conditions exceeded the threshold for cleanroom operations in 12/16 simulated operations. These findings indicate that LAF reduces the airborne microbial risk factor of surgical site infection in comparison to TAF

Introduction

Studies have addressed the issue of increasing prevalence of work-related musculoskeletal (MSK) pain among different occupations. However, contributing factors to MSK pain have not been fully investigated among orthopaedic surgeons. Thus, this study aimed to approximate the prevalence and predictors of MSK pain among Saudi orthopaedic surgeons working in Riyadh, Saudi Arabia.

Aims

Patient-specific instrumentation has been shown to increase a surgeon’s precision and accuracy in placing the glenoid component in shoulder arthroplasty. There is, however, little available information about the use of patient-specific planning (PSP) tools for this operation. It is not known how these tools alter the decision-making patterns of shoulder surgeons. The aim of this study was to investigate whether PSP, when compared with the use of plain radiographs or select static CT images, influences the understanding of glenoid pathology and surgical planning.

Aims

In the absence of an identified organism, single-stage revision is contraindicated in prosthetic joint infection (PJI). However, no studies have examined the use of intra-articular antibiotics in combination with single-stage revision in these cases. In this study, we present the results of single-stage revision using intra-articular antibiotic infusion for treating culture-negative (CN) PJI.

Introduction. Fixation has been shown to be the primary indicator of an implant's long-term success. Failure to achieve attachment, especially in acetabular and TKR, has been attributed to a lack of initial stability and gaps between the implant and bone. Gaps greater than 150 microns allow fibrous tissue to form. Properly addressing implant design features can help avoid adverse outcomes. ASTM International Standards (F1854-09) do not assess the relationship between porosity of the coating and that of cancellous bone, which can lead to an absence of mechanical interlock. This study developed a virtual program that uses human cancellous bone to predict potential skeletal attachment for implants properly placed for TJR. The goal of the Virtual Paradigm was to assess initial contact surface area at the time of implantation. Methods. Seven human femurs and tibias were used. Bones from 11 males and 3 females were used, ages ranging from 40 to 61. Five porous coatings were assessed: Biofoam (Wright Medical), Fiber Mesh, CSTI, Tantalum (Zimmer), and P² (DJO Global). Specimen Processing. Each bone was resected 2 mm beyond the articulating surface into the cancellous host using surgical TKA instruments. The specimens and coatings were embedded in PMMA. For Part 1, the specimens and coatings were cut perpendicular to the neutral axis, displaying a surface view for scanning electron microscopy (SEM). For Part 2, the coatings were cross-sectioned for SEM, ground, and polished to optical finish. Imaging: Part 1. The bone and coating sections displaying the surface view were imaged using SEM under backscatter (BSE) at 22x. Three images were taken of each tibia section, resulting in 12 images. Three images were taken of each femur section, resulting in 9 images. Analysis: Part 1. Each bone image was overlaid onto each coating image. Using various computer programs (IQ Materials, Fastone Image Viewer, Corel Photopaint X3), available bone was normalized to 100% and bone-implant contact was marked red (Figure 1). Imaging: Part 2. The cross-sectioned coatings were imaged with SEM-BSE at 30x. For each implant, 3 images were taken and assembled together (Microsoft Research ICE). Analysis: Part 2. Using the programs, bone images were overlaid onto each coating to establish a 200-micron region of initial contact. The surface of the coating within this region was calculated to represent surface roughness (Figure 2). Results. Bone porosity ranged from 14.04%-23.04% in the femur and 11.85%-23.68% in the tibia. Percent contact between the implant and bone ranged from 3.28%-43.47% (Figure 1). Surface roughness ranged from 5.4–11.1 mm (Figure 2). Opening porosity of the coatings ranged from 52.54%-94.97% (Figure 3). Discussion. Long-term success of cementless TJR depends on mechanical stability and bone attachment. This virtual study addressed fixation and contact between coatings and cancellous bone, and it can be used to evaluate innovative materials intended for TJR. This program challenged the limits of ASTM Standards for screening coatings. The results of this study demonstrated that the Virtual Bone-Implant Surface Contact Paradigm could be used in the early phases of implant development and testing to assess clinical success

Aims

The purpose of the present study was to compare patient-specific instrumentation (PSI) and conventional surgical instrumentation (CSI) for total knee arthroplasty (TKA) in terms of early implant migration, alignment, surgical resources, patient outcomes, and costs.

Aims

Arthroplasty skills need to be acquired safely during training, yet operative experience is increasingly hard to acquire by trainees. Virtual reality (VR) training using headsets and motion-tracked controllers can simulate complex open procedures in a fully immersive operating theatre. The present study aimed to determine if trainees trained using VR perform better than those using conventional preparation for performing total hip arthroplasty (THA).

Aims

The aim of this study was to assess the effects of transferring patients to a specialized arthroplasty centre between the first and second stages (interstage) of prosthetic joint infection (PJI) of the knee.

Aims

This aim of this study was to assess the feasibility of designing and introducing generic 3D-printed instrumentation for routine use in total knee arthroplasty.

Aims

Robotic-assisted unicompartmental knee arthroplasty (UKA) promises accurate implant placement with the potential of improved survival and functional outcomes. The aim of this study was to present the current evidence for robotic-assisted UKA and describe the outcome in terms of implant positioning, range of movement (ROM), function and survival, and the types of robot and implants that are currently used.

Study Design: Retrospective study with clinical and radiological evaluation of 29 patients with congenital scoliosis who underwent 31 short segment anterior instrumented fusions of lateral hemivertebrae. Objective: To evaluate the safety and efficacy of early surgical anterior instrumented fusion with partial preservation of the HV in the treatment of progressive congenital scoliosis in children below the age of 6. Summary of background data: A variety of treatments have been described in the literature for the treatment of HV. We report the results of a novel technique. Materials and Methods: Between 1996 and 2005, 29 consecutive patients with 31 lateral HV and progressive scoliosis underwent short segment anterior instrumentation and fusion with preservation of the HV. Mean age at surgery was 2.9 years. Mean follow-up period was 6.3 years. Results: Preoperative segmental Cobb angle averaging 39°, was corrected to 150 after surgery, being 15º at the last follow up (60% of improvement). Compensatory cranial and caudal curves corrected by approximately 50% and did not change significantly on follow up. The angle of segmental kyphosis averaged 13º before surgery, 12º after surgery, and 12° at follow up. There was 2 wound infection requiring surgical debridment, 1 intraoperative fracture of the vertebral body and 1 case lost correction due to implant failure. All went on to stable bony union. There were no neurologic complications. Conclusions: Early diagnosis and early and aggressive surgical treatment are mandatory for a successful treatment of congenital scoliosis and to prevent the development of secondary compensatory deformities. Anterior instrumentation is a safe and effective technique capable of transmitting a high amount of convex compression allowing short segment fusion which is of great importance in the growing spine

Aims

Single-stage revision is not widely pursued due to restrictive inclusion criteria. In this study, we evaluated the results of single-stage revision of chronically infected total hip arthroplasty (THA) using broad inclusion criteria and cementless implants.

Deep infection was identified as a serious complication in the earliest days of total hip arthroplasty. It was identified that airborne contamination in conventional operating theatres was the major contributing factor. As progress was made in improving the engineering of operating theatres, airborne contamination was reduced. Detailed studies were carried out relating airborne contamination to deep infection rates.

In a trial conducted by the United Kingdom Medical Research Council (MRC), it was found that the use of ultra-clean air (UCA) operating theatres was associated with a significant reduction in deep infection rates. Deep infection rates were further reduced by the use of a body exhaust system. The MRC trial also included a detailed microbiology study, which confirmed the relationship between airborne contamination and deep infection rates.

Recent observational evidence from joint registries has shown that in contemporary practice, infection rates remain a problem, and may be getting worse. Registry observations have also called into question the value of “laminar flow” operating theatres.

Observational evidence from joint registries provides very limited evidence on the efficacy of UCA operating theatres. Although there have been some changes in surgical practice in recent years, the conclusions of the MRC trial remain valid, and the use of UCA is essential in preventing deep infection.

There is evidence that if UCA operating theatres are not used correctly, they may have poor microbiological performance. Current UCA operating theatres have limitations, and further research is required to update them and improve their microbiological performance in contemporary practice.

Cite this article: Bone Joint J 2018;100-B:1264–9.

Study Design: Retrospective study with clinical and radiological evaluation of 15 patients with congenital kyphosis or kyphoscoliosis who underwent anterior instrumented spinal fusion for posterolateral or posterior hemivertebae (HV). Objective: To evaluate the safety and efficacy of early surgical anterior instrumented fusion with partial preservation of the HV in the treatment of progressive congenital kyphosis in children below the age of 3. We discuss the management of patients presenting with neurological compromise. Summary of background data: A variety of treatments have been described in the literature for the treatment of congenital kyphosis due to HV. We report the results of our technique. Materials and Methods: Between 1997 and 2005 we have treated 15 consecutive patients with progressive congenital kyphosis with anterior instrumented fusion and strut grafting. 13 patients had a single posterolateral HV and 2 patients a single posterior HV. Of the 15 patients in the study, 5 were girls and 10 boys. Mean age at surgery was 22 months (range 8–33). Mean follow-up period was 6.8 years. 13 HV were located in the thoracolumbar junction (T10-L2) and 2 in the thoracic spine. Results: The average operating time was procedure was 150 minutes (range, 130 to 210 minutes). The average blood loss 180 mL (range, 100 to 330 mL), equivalent to a mean external blood volume loss of 15% (range, 11 to 24%). Preoperative segmental Cobb angle averaging 34 º at last follow up. Compensatory coronal cranial and caudal curves corrected by 50%. The angle of segmental kyphosis averaged 39º (range, 20º to 80º) before surgery and 21 º (range, 11º to 40º) at last follow up. This represents a 43% of improvement of the segmental kyphosis, and a 64% of improvement of the segmental scoliosis at last followup. One case with initial kyphosis of 80 º continued to progress and required revision anterior and posterior surgery. There were no neurologic complications. Key points:. In progressive congenital kyphoisis, early diagnosis and aggressive surgical treatment are mandatory for a successful result. Early treatment minimizes the risks of surgery. Anatomical and physiological pitfalls in the treatment of congenital kyphosis are discussed. Anterior instrumented fusion of congenital kyphosis provides sagital and coronal correction in very young children with low risk of complications

INTRODUCTION. Nowadays, longevity of total knee arthroplasties is very acceptable. Survivorship analyses demonstrate a success in a range of 80% to more than 95% over a period of more than ten years (1–4). However, long-term results largely depend, amongst other factors, on restoration of physiological alignment of the lower limb (5–11). Jeffery et al. (12) reported a three percent loosening rate over eight years when knees were correctly aligned whereas insufficient alignment lead to prosthetic loosening in 24 percent. Rand and Coventry (13) found a 90 percent survivorship rate at ten years when the mechanical axis was aligned in a range from nought to four degrees of valgus. Valgus position of more than four degrees or varus alignment resulted in only 71 percent and 73 percent of survivorship respectively. Recently, computer aided instrumentation systems (14,15) became available and preliminary results of small series were reported (16–17). The purpose of this study was to assess the accuracy of computer integrated instrumentation for knee alignment. MATERIAL AND METHOD. The OrthoPilot. ®. represents a computer controlled image supported alignment system. A 3-D Optotrak™ camera localizes infra-red diodes fixed to rigid bodies within the surgical field. Thereby a spatial coordinate reference system is provided. The localizer is linked to a UNIX work station which performs the operative protocol using a graphical interface and a foot pedal. The rigid bodies are fixed to the bones by bicortical screws. An intraoperative kinematic analysis and various additional landmarks lead to definition of the centres of hip, ankle and knee joint and sizing of endoprosthetic components. With the use of LED-equipped alignment instruments the femoral and tibial resection planes are determined. The OrthoPilot. ®. navigation system is not dependant on CT data and no additional preoperative planning is therefore necessary. A prospective comparative multicentre study in five institutions, four in Germany and one in France, was carried out. 821 patients with primary tricompartimental knee arthroplasty using the SEARCH LC knee (B|Braun AESCULAP) were included in the study. The OrthoPilot. ®. Navigation system was used in 555 cases and 266 knees were implanted with the use of conventional instrumentation. At the three months follow-up alignment was assessed using standardized one leg stance radiographs with regard to the mechanical axis and the femoral and tibial angels in the coronal plane. For the lateral femoral and tibial angels standard lateral x-rays were used. Prosthetic alignment was verified by an independent observer. RESULTS. The radiographically assessed results were subdivided into three groups. An error of ± one degree in the radiographical measurements and small deviations caused by the play of surgical instruments have to be considered. With respect to the femoral and tibial angels in the ap and lateral view the group of very good clinical results was, therefore, defined in the range between ninty degrees and ± two degrees. Deviations of three and four degrees from the optimum were classified as being clinically acceptable. Aberrations of more than four degrees were classified as outliers. When measuring the mechanical axis deviations from fully precise femoral and tibial angels may add up. For this reason zero degrees ± three degrees were rated as a very good result, deviations of four to five degrees were considered to be acceptable and alignment beyond five degrees from the optimum was classified as an unsatisfactory result. Mechanical axis:. 35. 2% of the navigated cases were aligned at exactly zero degrees. This was achieved in only 24. 4% of the manual cases. 88. 6% of cases using navigation and 72. 2% in the manual group showed zero degrees and varus or valgus angles of up to three degrees. 8. 9% and 18. 1% of cases respectively showed deviations of four or five degrees of valgus or varus alignment representing an acceptable clinical result. In only 2. 5% of the navigation group aberrations of more than five degrees occurred. The rate of dissatisfying results was 9. 8% in the manual group. Femoral axis (coronal plane):. In the navigation group 48. 1% of cases showed an alignment at exactly 90 degrees which was the case in only 33. 5% of the control group. Altogether, in 89. 4% of the navigated cases a very good result was observed. In the conventionally instrumented cases only 77. 1% very good results were found. There were 1. 6% outliers beyond the limits of four degrees in the navigation group in comparison to 4. 9% amongst the control cases. Femoral axis (sagittal plane):. Very good results with up to two degrees of deviation from a ninety degree position were obtained in 75. 5% of navigated cases and 70. 7% of manual cases. 37. 3% and 34. 6% respectively showed an ideal alignment of exactly ninety degrees. Unsatisfactory results were observed in 9. 5% of the navigated cases and 9. 4% of the manual cases. Tibial axis (coronal plane):. 58. 7% of the computer assisted and 40. 6% of the reference cases were exactly aligned at rectangles. All in all, in 91. 9% navigated and only 83. 5% manual cases a very good result was obtained. Only 1. 1% outliers had to be observed in the navigation group whereas 3. 4% unsatisfactory results were registered with manual technique. Tibial axis (sagittal plane):. 44. 3% of the navigated cases and only 26. 7% of cases in the control group were aligned perpendicular to the dorsal tibial cortex, thus showing no posterior slope. Altogether, 81. 3% could be classified as very good clinical results in the computer assisted group. The corresponding rate of the manual group was 69. 9%. Equivalent values of 8. 6% in the navigation group and 8. 3% in the reference group were registered beyond the limits of four degrees deviation. The additional operation time for the use of the navigation system is calculated between eight and ten minutes after having passed through the learning curve. CONCLUSIONS. Knee navigation facilitates proper alignment of endoprosthetic components and with the use of the Ortho-Pilot. ®. system results are clearly more favourable in comparison to conventional instrumentation technique. In addition, the data obtained from literature demonstrate that the use of this navigation system contributes to reducing outliers in number. With the learning curve the OrthoPilot. ®. alignment system proved to gain in reliability. Deviations from perfect alignment are still difficult to be classified into surgical or technical deficiencies. Many technical and software improvements which were introduced in the meantime will, in addition, contribute to reliability and time saving. Comparative studies with different navigation systems are not yet available. They might allow an even more profound insight into the possibilities and advantages or disadvantages of computer assisted knee alignment. LITERATURE. (1) Knutson K, Lindstrand A, Lidgren L. Survival of knee arthroplasties, a nation-wide multicenter investigation of 8000 cases. J Bone Joint Surg. 1986; 68B: 795-803 . (2) Scuderi GR, Insall JN, Windsor RE, Moran MC. Survivorship of cemented knee replacement. J Bone Joint Surg. 1989; 798-409 . (3) Nafei A, Kristensen O, Knudson HM, Hvid I, Jensen J. Survivorship analysis of cemented total condylar knee arthoplasty. J Arthoplasty 11, 1996;07-10 . (4) Ranawat CS, Flynn WF, Saddler S, Hansraj KH, Maynhard MJ. Long-term results of total condylar knee arthroplasty. A 15-years survivorship study. Clin Orthop 1993; 286:94-102 . (5) Lotke PA, Ecker ML. Influence of positioning of prosthesis in total knee replacement. J Bone Joint Surg 1977;59-A:77-79 . (6) Hood RW, Vanni M, Insall JN. The correction of knee alignment in 225 consecutive total condylar knee replacements. Clin Orthop 1981;160:94-105 . (7) Bargren JH, Blaha JD, Freeman MAR. Alignment in total knee arthroplasty. Clin Orthop 1983;173:178-183. . (8) Hvid I, Nielsen S. Total condylar knee arthroplasty. Acta Orthop Scand 1984;55:160-165 . (9) Tew M, Waugh W. Tibial-femoral alignment and the results of knee replacement. J Bone Joint Surg 1985;67-B:551-556 . (10) Jonsson B, Astrom J. Alignment and long-term clinical results of a semi-constrained knee prosthesis. Clin Orthop 1988;226:124-128 . (11) Ritter MA, Faris PM, Keating EM, Meding JB. Postoperative alignment of total knee replacement its effect on survival. Clin Orthop 1994;299:153-156 . (12) Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. J Bone Joint Surg 1991;73-B:709-714 . (13) Rand JA, Coventry MB. Ten-year evaluation of geometric total knee arthroplasty. 1988;232:168-173 . (14) Leitner F, Picard F, Minfelde R, Schulz HJ, Clinquin P, Saragaglia D. Computer assisted knee surgical total replacement. In: CVRMed-MRCAS. Troccaz J, Grimson E, Mösges R (Eds). 1997; 630-638, Springer . (15) Delp SL, Stulberg SD, Davies BL, Picard F, Leitner F. Computer assisted knee replacement. Clin Orthop 1998; 354:49-56 . (16) Picard F, Saragaglia D, Montbarbon E, Chaussard C, Leitner F, Raoult O. Computer assisted knee arthroplasty - preliminary clinical results with the Ortho-Pilot System. Abstract, 4th International CAOS Symposium, Davos, Switzerland, 1999 . (17) Miehlke RK, Clemens U, Jens J-H, Kershally S. Navigation in der Knieendoprothetik - vorläufige klinische Erfahrungen und prospektiv vergleichende Studie gegenüber konventioneller Implantationstechnik, Z Orthop 2001; 139: 109-116