Mixed Reality has the potential to improve accuracy and reduce required dissection for the performance of peri-acetabular osteotomy. The current work assesses initial proof of concept of MR guidance for PAO. A PAO planning module, based on preoperative computed tomography (CT) imaging, allows for the planning of PAO cut planes and repositioning of the acetabular fragment. 3D files (holograms) of the cut planes and native and planned acetabulum positions are exported with the associated spatial information. The files are then displayed on mixed reality head mounted device (HoloLens2, Microsoft) following intraoperative registration using an FDA-cleared mixed reality application designed primary for hip arthroplasty (HipInsight). PAO was performed on both sides of a bone model (Pacific Research). The osteotomies and acetabular reposition were performed in accordance with the displayed holograms. Post-op CT imaging was performed for analysis. Cutting plane-accuracy was evaluated using a best-fit plane and 2D angles (°) between the planned and achieved supra (SA)- and retroacetabular (RA) osteotomy and retroacetabular and ischial osteotomies (IO) were measured. To evaluate the accuracy of acetabular reorientation, we digitized the acetabular rim and calculated the acetabular opening plane. Absolute errors of planned and achieved operative inclination and anteversion (°) of the acetabular fragment, as well as 3D lateral-center-edge (LCE) angles were calculated. The mean absolute difference between the planned and performed osteotomy angles was 3 ± 3°. The mean absolute error between planned and achieved operative anteversion and inclination was 1 ± 0° and 0 ± 0° respectively. Mean absolute error between planned and achieved 3D LCE angle was 0.5 ± 0.7°. Mixed-reality guidance for the performance of pelvic osteotomies and acetabular fragment reorientation was feasible and highly accurate. This solution may improve the current standard of care by enabling reliable and precise reproduction of the desired acetabular realignment

Osteoarthritis (OA) is a common cause of chronic pain. Subchondral bone is highly innervated, and bone structural changes directly correlate with pain in OA. Mechanisms underlying skeletal–neural interactions are under-investigated. Bone derived axon guidance molecules are known to regulate bone remodelling. Such signals in the nervous system regulate neural plasticity, branching and neural inflammation. Perturbation of these signals during OA disease progression may disrupt sensory afferents activity, affecting tissue integrity, nociception, and proprioception. Osteocyte mechanical loading and IL-6 stimulation alters axon guidance signalling influencing innervation, proprioception, and nociception. Human Y201 MSC cells, embedded in 3D type I collagen gels (0.05 × 106 cell/gel) in 48 well plastic or silicone (load) plates, were differentiated to osteocytes for 7 days before stimulation with IL-6 (5ng/ml) with soluble IL-6 receptor (sIL-6r (40ng/ml) or unstimulated (n=5/group), or mechanically loaded (5000 μstrain, 10Hz, 3000 cycles) or not loaded (n=5/group). RNA extracted 1hr and 24hrs post load was quantified by RNAseq whole transcriptome analysis (NovaSeq S1 flow cell 2 × 100bp PE reads and differentially expressed neurotransmitters identified (>2-fold change in DEseq2 analysis on normalised count data with FDR p<0.05). After 24 hours, extracted IL-6 stimulated RNA was quantified by RT-qPCR for neurotrophic factors using 2–∆∆Ct method (efficiency=94-106%) normalised to reference gene GAPDH (stability = 1.12 REfinder). Normally distributed data with homogenous variances was analysed by two-tailed t test. All detected axonal guidance genes were regulated by mechanical load. Axonal guidance genes were both down-regulated (Netrin1 0.16-fold, p=0.001; Sema3A 0.4-fold, p<0.001; SEMA3C (0.4-fold, p<0.001), and up-regulated (SLIT2 2.3-fold, p<0.001; CXCL12 5-fold, p<0.001; SEMA3B 13-fold, p<0.001; SEMA4F 2-fold, p<0.001) by mechanical load. IL6 and IL6sR stimulation upregulated SEMA3A (7-fold, p=0.01), its receptor Plexin1 (3-fold, p=0.03). Neutrophins analysed in IL6 stimulated RNA did not show regulation. Here we show osteocytes regulate multiple factors which may influence innervation, nociception, and proprioception upon inflammatory or mechanical insult. Future studies will establish how these factors may combine and affect nerve activity during OA disease progression

Abstract. Objective. Open fracture management in the United Kingdom and several other countries is guided by the British Orthopaedic Association's Standards for Trauma Number 4 (BOAST-4). This is updated periodically and is based on the best available evidence at the time. The aim of this study is to evaluate the evidence base forming this guidance and to highlight new developments since the last version in 2017. Methods. Searches have been performed using the PubMed, Embase and Medline databases for time periods a) before December 31, 2017 and from 01/01/2018–01/02/2021. Results have been summarised and discussed. Results. Several contentious issues remain within the 2017 guideline. Antibiotic guidance, the use of antibiotic impregnated PMMA beads and intramedullary devices, irrigation in the emergency department, time to theatre and the use of negative pressure dressings and guidance regarding the management of paediatric injuries have all demonstrated no clear consensus. Conclusion. The advent of the BOAST-4 guideline has been of huge benefit, however the refinement and improvement of this work remains ongoing. There remains a need for further study into these contentious issues previously listed

Aims. The aim of the British Association for Surgery of the Knee (BASK) Meniscal Consensus Project was to develop an evidence-based treatment guideline for patients with meniscal lesions of the knee. Materials and Methods. A formal consensus process was undertaken applying nominal group, Delphi, and appropriateness methods. Consensus was first reached on the terminology relating to the definition, investigation, and classification of meniscal lesions. A series of simulated clinical scenarios was then created and the appropriateness of arthroscopic meniscal surgery or nonoperative treatment in each scenario was rated by the group. The process was informed throughout by the latest published, and previously unpublished, clinical and epidemiological evidence. Scenarios were then grouped together based upon the similarity of clinical features and ratings to form the guideline for treatment. Feedback on the draft guideline was sought from the entire membership of BASK before final revisions and approval by the consensus group. Results. A total of 45 simulated clinical scenarios were refined to five common clinical presentations and six corresponding treatment recommendations. The final guideline stratifies patients based upon a new, standardized classification of symptoms, signs, radiological findings, duration of symptoms, and previous treatment. Conclusion. The 2018 BASK Arthroscopic Meniscal Surgery Treatment Guidance will facilitate the consistent identification and treatment of patients with meniscal lesions. It is hoped that this guidance will be adopted nationally by surgeons and help inform healthcare commissioning guidance. Validation in clinical practice is now required and several areas of uncertainty in relation to treatment should be a priority for future high-quality prospective studies. Cite this article: Bone Joint J 2019;101-B:652–659

Aim. Bone and joint infection requires antimicrobial treatment for 6 to 12 weeks. When patients are well prepared and instructed regarding their therapy, they are more likely to have less side effects and improved compliance. Although side effects are common, this coaching is often not routinely performed when oral treatment is given. We developed a monitoring and guidance program for our outpatients who are on long term antimicrobial therapy, in which we can early signal side effects and treatment failure and coach the patients in their journey of infection treatment. Method. In our tertiary referral centre for orthopaedic infections, we started the outpatient monitoring of antimicrobial treatment (OMAT)- team for patients who will receive antimicrobial therapy for >2 weeks. Before discharge, our trained nurse gives instruction to the patient. Within 3 days after hospital discharge the patient is contacted by phone to, if necessary, clarify ambiguities in monitoring set up. During this contact, the nurse checks for side effects, addresses logistic problems regarding laboratory monitoring or future appointments and coaches patients for other questions. The patient is instructed how to recognize and who to contact in case of red flags and problems possibly related to the treatment. This is repeated after every laboratory check-up. Supervision is performed by an infectious disease specialist in close collaboration with the patient's surgeon. Results. The OMAT-team started in October 2020 and consists of 3 trained nurses and 3 ID specialist. In one year, 453 patients were proactively monitored for a mean of 11 weeks. Routinely, laboratory measurements were performed 1 week after the start of therapy and every 3–4 weeks thereafter, which resulted in 2711 contacts per year. In total, 64% of the patients reported side effects and 13% needed one or more extra laboratory measurement. This led to 40 additional outpatient consultations by the ID specialist because of complications of treatment and a switch of the antimicrobial agent in 31% of the patients. Conclusions. OMAT seems to improve the early signalling of complications regarding treatment, which is likely to improve compliance. The OMAT-team serves as a easy to access team to discuss any problem regarding antimicrobial therapy. Being proactive, the OMAT-team intervenes in an early stage of problems regarding side effects, logistics of the treatment and possible treatment failure. Future analysis of our data will show to what extend this will lead to prevention of re-hospitalization and improvement of success rate

Aims. The objective of this double-blind randomised controlled trial was to assess whether ultrasound guidance improved the efficacy of corticosteroid injections for Morton’s neuroma (MN). . Patients and Methods. In all, 50 feet (40 patients) were recruited for this study but five feet were excluded due to the patients declining further participation. The mean age of the remaining 36 patients (45 feet) was 57.8 years (standard deviation (. sd. ) 12.9) with a female preponderance (33F:12M). All patients were followed-up for 12 months. Treatment was randomised to an ultrasound guided (Group A) or non-ultrasound guided (Group B) injection of 40 mg triamcinolone acetonide and 2 ml 1% lignocaine, following ultrasound confirmation of the diagnosis. . Results. The mean visual analogue score for pain improved significantly in both groups (Group A – from 64 mm, . sd. 25 mm to 29 mm, . sd. 27; Group B – from 69 mm, . sd. 23 mm to 37 mm, . sd. 25) with no statistical difference between them at all time-points. The failure rate within 12 months of treatment was 11/23 (48%) and 12/22 (55%) in Groups A and B, respectively (p = 0.458). The improvement in Manchester Oxford Foot Questionnaire Index and patient satisfaction favoured Group A in the short-term (three months) that almost reached statistical significance (p = 0.059 and 0.066 respectively). However, this difference was not observed beyond three months. . Conclusion. This study has shown that ultrasound guidance did not demonstrably improve the efficacy of corticosteroid injections in patients with MN. Take home message: In the presence of a clear diagnosis of MN, a trained clinician who understands the forefoot anatomy may perform an injection without ultrasound guidance with good and safe results. Cite this article: Bone Joint J 2016;98-B:498–503

Tourniquet is a commonly used tool in orthopaedic practice. Incidence of complications is low but if any develops, it is devastating. Transient nerve damage, ischemia or skin burns are the possible tourniquet related complications. There is big variation in practice regarding the limb occlusion pressure. 51 procedures in 50 patients were reviewed retrospectively in our district general hospital. We looked at quality of documentation guided by the BOAST standard (The Safe Use of Intraoperative Tourniquets, published in October 2021). Limb occlusion pressure and ischemic time were analysed. Intra-operative and post-operative notes were reviewed to assess quality of documentation and post-operative complications. Although limb occlusion pressure was above the recommended range in more than 75% of cases, there were no significant complications observed. Two cases only developed transient neuropraxia in common peroneal nerve and median nerve following tibial plateau ORIF and trapeziectomy simultaneously. Tibial ORIF fixation case had prolonged ischemic time (more than 120 minutes) and the limb occlusion pressure for the hand case was above the recommended range. Both have recovered within few days with no long-term consequences. Minimum documentation threshold was not met with regarding tourniquet site condition, method of skin isolation and padding, and exsanguination method. This relatively new standard with no previous similar guidance needs time until it is followed by the health care professionals especially when there is no high incidence of complications related to the use of the tourniquet. However, it is crucial to increase the theatre staff awareness of such standards. This will prevent devastating complications specifically in vulnerable patients. Adjustments to theatre checklist have been suggested to improved documentation. Additionally, local teaching sessions will be delivered to theatre personnel aiming at improving our compliance to this standard

Total knee arthroplasty (TKA) is a common procedure with good success rates. The literature shows resection accuracy plays a crucial role in device longevity. 1. Computer guidance is used by some surgeons to enhance accuracy. This study reports on a continuous series of Optetrak knee prostheses (Exactech Inc., FL, USA) implanted by three senior surgeons between October 2010 and December 2013. 324 TKA were implanted at the Joseph Ducuing Hospital, Toulouse, France (Site 1), the Cleveland Clinic, Cleveland, OH, USA (Site 2) and the Riverview Hospital, Noblesville, IN, USA (Site 3) using Exactech GPS (Blue-Ortho, Grenoble, FR), a new computer-assisted guidance system. Each centre in this study used different surgical profiles defined specifically for their surgeical preferences. Planned tibial and femoral cuts were compared to actual cuts digitised using GPS. Operating time was analyzed and post-operative leg alignment was compared to pre-operative. The mean error between planned and digitised proximal tibial cuts was 0.06°±0.89 of valgus and 0.53°±0.90 of anterior slope for Site 1, 0.18°±0.85 of varus and 0.25°±1.18 of posterior slope for Site 2, and 0.02°±0.51 of valgus and 0.60°±1.15 of anterior slope for Site 3. The mean error between planned and digitised femoral distal cuts was 0.14°±0.85 of valgus and 0.49°±0.93 of flexion for Site 1, 0.15°±0.96 of varus and 0.04°±1.54 of extension for Site 2, and 0.09°±0.54 of varus and 0.48°±1.21 of extension for Site 3. Average operating time was 29 minutes for Site 1, 39 minutes for Site 2, and 33 minutes for Site 3. Post-operative Hip-Knee-Ankle angle (HKA) varied between 172° and 184° with an average of 179° for Site 1, 177° to 183° with an average of 179° for Site 2, and 177° to 185° with an average of 180° for Site 3. Pre-operative HKA ranged from 162 to 189°. Site 1 was already reporting in the series presented at ISTA 2013. 2. Sites 2 and 3 were added later and could therefore benefit from the early feedback the analysis of site 1 cases provided. The use of the computer guidance at the new sites was associated with promising results and it did not take long to the surgeons to reach a reproducibility equivalent to the one of site 1. Average surgical time was similar in all three sites. GPS guidance added an average of 10 minutes to standard surgical times. All surgeons agreed the increased accuracy justified the additional time. Average post-operative HKA was 179°. HKA scores were within 3° of perfect alignment in 96% of the cases of Site 1, 99% of Site 2 and 97% of Site 3. According to the literature. 1. , HKA between 177° and 183° is linked with high implant survival. Participating surgeons still associated Exactech GPS with satisfactory immediate post-operative results

Introduction. Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning. 1. The use of computer-assisted orthopedic surgery (CAOS) can improve overall TKA accuracy. 2. This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) used in TKA. Materials and methods:. A high-resolution 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan seven knee models (MITA, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks (see Figure 1) prior to using the models to simulate knee surgery. The image-free CAOS guidance system was then used to acquire the same landmarks. After adjusting the position and orientation of the cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid (see Figure 2) and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (XOV & XOR, RapidForm, Lakewood, CO and UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner were compared with data sets from the guidance system. Given the accuracy of the 3D scanner, its measurements were used as the baseline for assessing CAOS system error. Results:. The CAOS system bone resection measurement errors had an overall mean of less than 0.35 mm. The mean errors for joint angle measurement was less than 0.6° (see Table I). Even considering the ranges, errors were no more than 1 mm for all bone resection measurements and no more than 1° for all joint angle measurements. The low variability is also supported by small standard deviation values. Discussion/Conclusion:. To our knowledge, this is the first study to use a high-resolution 3D scanner to assess the accuracy of surgical cuts made with image-free CAOS system assistance. Determining precise landmarks using CAOS for TKA has been shown to be of critical importance. 3. For this reason, the anatomical landmarks used by the scanner and guidance system were carefully identified and prepared to ensure consistency. The study demonstrated that the evaluated image-free CAOS system was able to achieve a high level of in-vitro accuracy (small mean errors) as well as a high level of precision (small error variability) when making femoral and tibial bone resections during TKA

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

Percutaneous fixation of scaphoid fractures has become popular in recent years, mainly due to its reduced complexity compared to open surgical approaches. Fluoroscopy is currently used as guidance for this percutaneous approach, however, as a projective imaging modality, it provides only a 2D view of the complex 3D anatomy of the wrist during surgery, and exposes both patient and physician to harmful X-ray radiation. To avoid these drawbacks, 3D ultrasound has been suggested to provide imaging for guidance as a widely available, real-time, radiation-free and low-cost modality. However, the blurred, disconnected, weak and noisy bone responses render interpretation of the US data difficult so far. In this work, we present the integration of 3D ultrasound with a statistical wrist model to allow development of an improved ultrasound-based guidance procedure. For enhancement of bone responses in ultrasound, a phase symmetry based approach is used to exploit the symmetry of the ultrasound signal around the expected bone location. We propose an improved estimation of the local phase symmetry by using the local spectrum variation of the ultrasound image. The statistical wrist model is developed through a group-wise registration based framework in order to capture the major modes of shape and pose variations across 30 subjects at different wrist positions. Finally, the statistical wrist model is registered to the enhanced ultrasound bone surfaces using a probabilistic registration approach. Feasibility experiments are performed using two volunteer wrists, and the results are promising and warrant further development and validation to enable ultrasound guided percutaneous scaphoid fracture reduction

Background. Total Shoulder Arthroplasty (TSA) has been shown to improve the function and pain of patients with severe degeneration. Recently, TSA has been of interest for younger patients with higher post-operative expectations; however, they are treated using traditional surgical approaches and techniques, which, although amenable to the elderly population, may not achieve acceptable results with this new demographic. Specifically, to achieve sufficient visualization, traditional TSA uses the highly invasive deltopectoral approach that detaches the subscapularis, which can significantly limit post-operative healing and function. To address these concerns, we have developed a novel surgical approach, and guidance and instrumentation system (for short-stemmed/stemless TSA) that minimize muscle disruption and aim to optimize implantation accuracy. Development. Surgical Approach: A muscle splitting approach with a reduced incision size (∼6–8cm) was developed that markedly reduces muscle disruption, thus potentially improving healing and function. The split was placed between the infraspinatus and teres-minor (Fig.1) as this further reduces damage, provides an obvious dissection plane, and improves access to the retroverted articular surfaces. This approach, however, precludes the use of standard bone preparation methods/instruments that require clear visualization and en-face articular access. Therefore, a novel guidance technique and instrumentation paradigm was developed. Minimally Invasive Surgical Guidance: 3D printed Patient Specific Guides (PSGs) have been developed for TSA; however, these are designed for traditional, highly invasive approaches providing unobstructed access to each articular surface separately. As the proposed approach does not offer this access, a novel PSG with two opposing contoured surfaces has been developed that can be inserted between the humeral and scapular articular surfaces and use the rotator cuff's passive tension to self-locate (Fig.2). During computer-aided pre-operative planning/PSG design, the two bones are placed into an optimized relative pose and the PSG is constructed between and around them. This ensures that when the physical PSG is inserted intra-operatively, the bones are locked into the preoperatively planned pose. New Instrumentation Paradigm: With the constraints of this minimally invasive approach, a new paradigm for bone preparation/instrumentation was required which did not rely on en-face access. This new paradigm involves the ability to simultaneously create glenoid and humeral guide axes – the latter of which can guide humeral bone preparation and be a working channel for tools – by driving a short k-wire into the glenoid by passing through the humerus starting laterally (Fig.3). By preoperatively defining the pose produced by the inserted PSG as one that collinearly aligns the bones’ guide axes, the PSG and an attached c-arm drill guide facilitate this new lateral drilling technique. Subsequently, bone preparation is conducted using novel instruments (e.g. reamers and drills for creating holes radial to driver axis) powered using a trans-humeral driver and guided by the glenoid k-wire or humeral tunnel. Conclusion. To meet the expectations of increasingly younger TSA patients, advancements in procedural invasiveness and implantation accuracy are needed. This need was addressed by developing a novel, fully integrated surgical approach, PSG system, and instrumentation paradigm, the initial in-vitro results of which have demonstrated acceptable accuracy while significantly reducing invasiveness

Fractures of the femoral head are a challenging problem. The most often performed head preserving procedure worldwide is closed reduction and insertion of cannulated screws under fluoroscopic control. The use of navigation is still experimental in general trauma since rigid reference markers must be attached to all fragments. The examined system (Surgix®, Tel Aviv, Israel) is a fluoroscopy based image analysing system. It consists of a workstation and X-ray opaque markers in surgical tools. When the tool is visible in a C-arm shot a trajectory is displayed as additional layer in the image to serve as guidance for the surgeon. Forty synthetic femurs (Synbone®, Malans, Switzerland) were used and placed inside foam to simulate the soft tissue of the thigh. The models were equipped with 4.5mm radio-opaque markers at the fovea capitis femoris as target point. The aim was to bring the tip of a K-wire as close as possible to the target point entering the bone at the lateral base of the greater trochanter in a center-center position. Twenty were done under image guidance and 20 were operated the conventional way. Outcome measures included the accuracy (the distance between the tip of the wire and the target in a CT), the number of guide wire insertions, procedure duration, radiation exposure and learning curve. In the image guided group optimal guide wire placement was accomplished on first pass in 65% of the cases as compared to 5% in the conventional group (p = < 0.0001). The average number of trial and error was significantly lower in the guided group (1.7 vs. 5.8, p = < 0.0001). Consequently the average duration of the guided procedure was significantly shorter (p = 0.0008) along with radiation exposure time reduced by over 70% (p = 0.0002). The guidance system hit averaged 5.8 mm off target as compared to 5.3 mm for the freehand method (p = 0.3319). Image based guidance significantly shortened the procedure, reduced the radiation exposure and the number of trials without changing the surgeons workflow and can be used in trauma cases were reference marker based navigation is not applicable

Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning. The use of computer-assisted orthopedic surgery (CAOS) can improve overall TKA accuracy. This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) used in TKA. A high-precision 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan seven knee models (MITA, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks prior to using the models to simulate knee surgery. The Exactech GPS was then used to acquire the same landmarks. After adjusting the Exactech GPS cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (XOV & XOR, RapidForm, Lakewood, CO and UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner were compared with data sets from the guidance system. Given the accuracy of the 3D scanner, its measurements were used as the baseline for assessing CAOS system error. The CAOS system bone resection measurement errors had an overall mean of less than 0.35 mm. The mean errors for joint angle measurement was less than 0.6°. Even considering the ranges, errors were no more than 1 mm for all bone resection measurements and no more than 1° for all joint angle measurements. The low variability is also supported by small SD values. To our knowledge, this is the first study to use a high-resolution 3D scanner to assess the accuracy of surgical cuts made with image-free CAOS system assistance. Determining precise landmarks using CAOS for TKA has been shown to be of critical importance. For this reason, the anatomical landmarks used by the scanner and guidance system were carefully identified and prepared to ensure consistency. The study demonstrated that the evaluated image-free CAOS system was able to achieve a high level of in-vitro accuracy (small mean errors) as well as a high level of precision (small error variability) when making femoral and tibial bone resections during TKA

Cite this article: Bone Joint J 2024;106-B(1):6–8.

Introduction. Clinical outcomes for total knee arthroplasty (TKA) are especially sensitive to lower extremity alignment and implant positioning. 1. The use of computer-assisted orthopaedic surgery (CAOS) can improve overall TKA accuracy. 2. This study assessed the accuracy of an image-free CAOS guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) in both a synthetic leg with a normal mechanical axis and legs with abnormal mechanical axis. Materials and methods. A high-resolution 3D scanner (Comet L3D, Steinbichler, Plymouth, MI) was used to scan varus-deformed (n=12), neutral (n=12), and valgus-deformed (n=4) knee inserts (Mita M-00566, M-00598, M-00567; respectively, Medical Models, Bristol, UK) and collect pre-identified anatomical landmarks prior to using the models to simulate knee surgery. The image-free CAOS guidance system was then used to acquire the same landmarks. After adjusting the position and orientation of the cutting block to match the targets, bone resections were performed, and the knee models were re-scanned. The 3D scans made before and after the cuts were overlaid and the resection parameters calculated using the pre-identified anatomical landmark data and advanced software (UG NX, Siemens PLM, Plano, TX). Data sets obtained from the 3D scanner (see Figure 1A) were compared with data sets from the guidance system (see Figure 1B). Given the accuracy of the 3D scanner (<50μm), its measurements were used as the baseline for assessing CAOS system error. Results. Table I shows errors in bone resection thickness orientation measurement errors as well as CAOS system confidence intervals (CI) for both the tibia and femur, depending on deformity type. Regardless of knee deformity and other parameters, the mean error of the CAOS system was systematically less than 0.5 mm for bone resection measurements and 1° for joint angle measurements. The 95% CI were in the range of −1.54 to 0.67mm for bone resection measurements and −0.64° to 1.67° for joint angle measurements. No statistical differences were detected between different deformity groups in the Error Indexes for both the tibia and femur. Discussion. This study represents an extension of a previous evaluation of the same CAOS system, where only a limited number of neutral models (n=6) were investigated. The current study was performed to reassess the accuracy and precision of the CAOS system using the same methodology with a larger number of knee models (n=28) exhibiting different types of deformities affecting the mechanical axis. In conclusion, this study demonstrates a high level of in-vitro accuracy for the CAOS system, regardless of leg-alignment deformity type. The mean error of the CAOS system, characterized as the difference between the measured and checked values, was systematically less than 0.5 mm for bone resection measurements and 1° for joint angle measurements

Introduction. The Birmingham Hip Resurfacing (Smith & Nephew London, UK) is the most popular hip resurfacing (HR) in the UK. However, it is now subject to two Medical Device Alerts (MDA) from the Medicines and Healthcare products Regulatory Agency (MHRA). Patients/Materials & Methods. A cross-sectional survey of primary metal-on-metal hip procedures recorded on the National Joint Registry for England, Wales and Northern Ireland (NJR) until 5. th. November 2013 was performed. Cost-analysis was based on an algorithm for surveillance of HR at a tertiary referral centre and followed previous MHRA guidance. NIHR NHS Treatment costs were used. The local protocol encompassed: patient outcome scoring (Oxford hip score), blood metal ion measurement (cobalt, chromium), cross-sectional imaging (MRI) and discussion at an internet-enabled multidisciplinary team meeting (iMDT) in addition to routine hip surveillance. Results. A total of 33996 patients have Hip Resurfacings in the UK. 18478 have BHR and 9457 are female or small men. Costs:. Cobalt and Chromium levels £34.64. Single site MRI scan £438.91. Review of medical notes is £97.98. New Patient Appointment £137. Every patient requires at least 1 set of blood tests, an MRI and discussion in iMDT in our unit at a minimum cost of £571.53. This excludes clinic appointments; repeat testing, or costs of revision surgery and litigation. Total minimum cost to NHS £5.4 million. Discussion. It is important to not ignore nationally delivered guidance and therefore this patient group now requires comprehensive follow up as described by the MHRA. Other HR devices may now need to be considered to require further follow-up with inherently increased costs to the NHS. Conclusion. We recommend a streamlining of review via regional iMDTs in order to effectively manage MDA's and minimise potential costs

Introduction. From pre-operative planning to final implant cementation, total knee arthroplasty (TKA) can be defined by a succession of individual steps, each presenting potential errors that can result in devices being implanted outside the desired range of alignment. Our study used an image-free computer-assisted orthopedic surgery (CAOS) guidance system (Exactech GPS, Blue-Ortho, Grenoble, FR) to evaluate alignment discrepancies occurring during different steps of a typical TKA procedure. Materials and methods:. A surgical profile was established to define resection parameters and steps for proximal tibial and distal femoral cuts (see Figure 1A) to be made on seven synthetic knee models (MITA, Medical Models, Bristol, UK). First, the guidance system was used to acquire pre-identified landmarks. Next, a cutting block was adjusted to match the resection targets and then fixed to the bone using locking pins. Bone cuts were performed and then checked. Data was collected from the guidance system at three steps: (1) cutting block adjusted but not pinned to bone (see Figure 1B), (2) cutting block adjusted and pinned to bone (see Figure 1C), and (3) after checking cuts (see Figure 1D). These data were then compared to the resection target parameters to assess potential discrepancies. Results:. Discrepancies for all cuts were minimal, as the differences in bone resection thickness and angular measurement were less than 1 mm and 1°, respectively (see Table I). For each parameter, the mean value was close to nominal, demonstrating a well-centered distribution. This being said, there was a consistent derivative of the distal femoral parameters in extension (up to 0.9°), resulting in lower than expected amount of distal femur resection (up to 0.9 mm). Discussion/Conclusion:. In general, discrepancies at each step seemed random, and there was no apparent accumulation trend except for the flexion/extension of the distal femoral cut. There was a slight discrepancy in extension during the pinning of the block, possibly due to the offset weight of the tracker acting on the adjustable instrumentation. There was also a consistent discrepancy in extension during the cut, likely resulting from the saw skiving during cuts. Such a discrepancy can result in a slightly tighter joint in extension than expected. The guidance system did not exhibit substantial alignment discrepancies during procedure steps, reflecting its robustness

Background: To assess the accuracy of pedicle instrumentation placement using an image guidance system ( Medi Vision) in a pig cadaveric model. Methods: A 4mm diameter (10cm long) screw was inserted transversely into the spinous process of a pig cadaver percutaneously using fluoroscopic guidance. The dynamic reference base (DRB) of the image guidance system was then attached to the screw. Using the navigation system both pedicles at each level were identified and 3.2mm guide wires inserted percutaneously. This process was performed for each level from D7 to L4. Actual wire placement was recorded using standard anteroposterior and lateral fluoroscopic images. Virtual trajectories generated by the image guidance system were recorded on the guidance system database. Accuracy of wire placement was then evaluated in an automated way by linear correlation between corresponding images. Results: 20 pedicles were instrumented at 10 levels from D7 to L4. Mean estimate of accuracy for dorsal levels AP and lateral (mm). Mean = 1.452mm, standard deviation 1.57mm. Mean for lumber levels= 1.047mm, standard deviation 1.187mm. Conclusion: Lumbar pedicle instrumentation showed more accuracy when compared to dorsal pedicle instrumentation. The error of navigation that was accommodated by the image guidance system was 2mm. There was correlation between fluoroscopic copies and virtual trajectories. This image guidance system may not only aid in the placement of pedicle instrumentation but also assist the senior surgeon in trainee supervision

Introduction. Accurate component placement in total hip arthroplasty (THA) improves post-operative stability and reduces wear and aseptic loosening. Methods for achieving accurate stem placement have not been as extensively studied as cup placement. Objectives. The purpose of this study is to determine how consistently femoral stem version can be corrected to an ideal of 15 +/− 5 degrees using robotic guidance. Furthermore, the study aims to identify other factors related to approach and patient demographics, which may influence the degree of correction obtained. Methods. 175 consecutive patients who underwent MAKO robotic guidance THA were included in the study with a mean age of 57.9 years and a mean body mass index (BMI) of 30.41kg/m2. 48% of the population was male and 74% of the procedures were performed through an anterior approach. The absolute difference between 15 degrees of anteversion and native femoral version as well as 15 degrees of anteversion and femoral stem version was calculated for each patient. A smaller absolute value post-operatively reflects a closer femoral stem version to a target of 15 degrees. Results. The mean native femoral version was 6.39+/−9.14 degrees. The mean stem version was 9.23+/−8.57 degrees. With respect to achieving a target version of 15 degrees the mean absolute difference between native version and 15 degrees was 10.46+/−6.94 degrees and mean absolute difference between the stem version and 15 degrees was 8.37+/−6.03 degrees. This difference was statistically significant. 69% of patients were able to have their native femoral version corrected to a target of 15 degrees. Conclusions. Robotic guidance in THA was effective in correcting native femoral version towards a target of 15 degrees. This is can be achieved using both the anterior and posterior approach and is not affected by BMI