Aims. Excessive posterior pelvic tilt (PT) may increase the risk of anterior instability after total hip arthroplasty (THA). The aim of this study was to investigate the changes in PT occurring from the preoperative supine to postoperative standing position following THA, and identify factors associated with significant changes in PT. Methods. Supine PT was measured on preoperative CT scans and standing PT was measured on preoperative and one-year postoperative standing lateral radiographs in 933 patients who underwent primary THA. Negative values indicate posterior PT. Patients with > 13° of posterior PT from preoperative supine to postoperative standing (ΔPT ≤ -13°) radiographs, which corresponds to approximately a 10° increase in functional anteversion of the acetabular component, were compared with patients with less change (ΔPT > -13°). Logistic regression analysis was used to assess preoperative demographic and spinopelvic parameters predictive of PT changes of ≤ -13°. The area under receiver operating characteristic curve (AUC) determined the diagnostic accuracy of the predictive factors. Results. PT changed from a mean of 3.8° (SD 6.0°)) preoperatively to -3.5° (SD 6.9°) postoperatively, a mean change of -7.4 (SD 4.5°; p < 0.001). A total of 95 patients (10.2%) had ≤ -13° change in PT from preoperative supine to postoperative standing. The strongest predictive preoperative factors of large changes in PT (≤ -13°) from preoperative supine to postoperative standing were a large posterior change in PT from supine to standing, increased supine PT, and decreased standing PT (p < 0.001). Flexed-seated PT (p = 0.006) and female sex (p = 0.045) were weaker significant predictive factors. When including all predictive factors, the accuracy of the AUC prediction was 84.9%, with 83.5% sensitivity and 71.2% specificity. Conclusion. A total of 10% of patients had > 13° of posterior PT postoperatively compared with their supine pelvic position, resulting in an increased functional anteversion of > 10°. The strongest predictive factors of changes in postoperative PT were the preoperative supine-to-standing differences, the anterior supine PT, and the posterior standing PT. Surgeons who introduce the acetabular component with the patient supine using an anterior approach should be aware of the potentially large increase in functional anteversion occurring in these patients. Cite this article: Bone Joint J 2024;106-B(3 Supple A):74–80

Artificial intelligence and machine-learning analytics have gained extensive popularity in recent years due to their clinically relevant applications. A wide range of proof-of-concept studies have demonstrated the ability of these analyses to personalize risk prediction, detect implant specifics from imaging, and monitor and assess patient movement and recovery. Though these applications are exciting and could potentially influence practice, it is imperative to understand when these analyses are indicated and where the data are derived from, prior to investing resources and confidence into the results and conclusions. In this article, we review the current benefits and potential limitations of machine-learning for the orthopaedic surgeon with a specific emphasis on data quality.

Aims. Ideal component sizing may be difficult to achieve in unicompartmental knee arthroplasty (UKA). Anatomical variants, incremental implant size, and a reduced surgical exposure may lead to over- or under-sizing of the components. The purpose of this study was to compare the accuracy of UKA sizing with robotic-assisted techniques versus a conventional surgical technique. Methods. Three groups of 93 medial UKAs were assessed. The first group was performed by a conventional technique, the second group with an image-free robotic-assisted system (Image-Free group), and the last group with an image-based robotic arm-assisted system, using a preoperative CT scan (Image-Based group). There were no demographic differences between groups. We compared six parameters on postoperative radiographs to assess UKA sizing. Incorrect sizing was defined by an over- or under-sizing greater than 3 mm. Results. There was a higher rate of tibial under-sizing posteriorly in the conventional group compared to robotic-assisted groups (47.3% (n = 44) in conventional group, 29% (n = 27) in Image-Free group, 6.5% (n = 6) in Image-Based group; p < 0.001), as well as a higher rate of femoral under-sizing posteriorly (30.1% (n = 28) in conventional group, 7.5% (n = 7) in Image-Free group, 12.9% (n = 12) in Image-Based group; p < 0.001). The posterior femoral offset was more often increased in the conventional group, especially in comparison to the Image-Based group (43% (n = 40) in conventional group, 30.1% (n = 28) in Image-Free group, 8.6% (n = 8) in Image-Based group; p < 0.001). There was no significant overhang of the femoral or tibial implant in any groups. Conclusion. Robotic-assisted surgical techniques for medial UKA decrease the risk of tibial and femoral under-sizing, particularly with an image-based system using a preoperative CT scan. Cite this article: Bone Joint J 2021;103-B(4):610–618

Introduction. The increased prevalence of osteoporosis in the patient population undergoing reverse shoulder arthroplasty (RSA) results in significantly increased complication rates. Mainly demographic and clinical predictors are currently taken into the preoperative assessment for risk stratification without quantification of preoperative computed tomography (CT) data (e.g. bone density). It was hypothesized that preoperative CT bone density measures would provide objective quantification with subsequent classification of the patients’ humeral bone quality. Methods. Thirteen bone density parameters from 345 preoperative CT scans of a clinical RSA cohort represented the data set in this study. The data set was divided into testing (30%) and training data (70%), latter included an 8-fold cross validation. Variable selection was performed by choosing the variables with the highest descriptive value for each correlation clustered variables. Machine learning models were used to improve the clustering (Hierarchical Ward) and classification (Support Vector Machine (SVM)) of bone densities at risk for complications and were compared to a conventional statistical model (Logistic Regression (LR)). Results. Clustering partitioned this cohort (training data set) into a high bone density subgroup consisting of 96 patients and a low bone density subgroup consisting of 146 patients. The optimal number of clusters (n = 2) was determined based on optimization metrics. Discrimination of the cross validated classification model showed comparable performance for the training (accuracy=91.2%; AUC=0.967) and testing data (accuracy=90.5 %; AUC=0.958) while outperforming the conventional statistical model (Logistic Regression (LR)). Local interpretable model-agnostic explanations (LIME) were created for each patient to explain how the predicted output was achieved. Conclusion. The trained and tested model provides preoperative information for surgeons treating patients with potentially poor bone quality. The use of machine learning and patient-specific calibration showed that multiple 3D bone density scores improved accuracy for objective preoperative bone quality assessment

Aims. The aim of this study was to compare the biomechanical models of two frequently used techniques for reconstructing severe acetabular defects with pelvic discontinuity in revision total hip arthroplasty (THA) – the Trabecular Metal Acetabular Revision System (TMARS) and custom triflange acetabular components (CTACs) – using virtual modelling. Methods. Pre- and postoperative CT scans from ten patients who underwent revision with the TMARS for a Paprosky IIIB acetabular defect with pelvic discontinuity were retrospectively collated. Computer models of a CTAC implant were designed from the preoperative CT scans of these patients. Computer models of the TMARS reconstruction were segmented from postoperative CT scans using a semi-automated method. The amount of bone removed, the implant-bone apposition that was achieved, and the restoration of the centre of rotation of the hip were compared between all the actual TMARS and the virtual CTAC implants. Results. The median amount of bone removed for TMARS reconstructions was significantly greater than for CTAC implants (9.07 cm. 3. (interquartile range (IQR) 5.86 to 21.42) vs 1.16 cm. 3. (IQR 0.42 to 3.53) (p = 0.004). There was no significant difference between the median overall implant-bone apposition between TMARS reconstructions and CTAC implants (54.8 cm. 2. (IQR 28.2 to 82.3) vs 56.6 cm. 2. (IQR 40.6 to 69.7) (p = 0.683). However, there was significantly more implant-bone apposition within the residual acetabulum (45.2 cm. 2. (IQR 28.2 to 72.4) vs 25.5 cm. 2. (IQR 12.8 to 44.1) (p = 0.001) and conversely significantly less apposition with the outer cortex of the pelvis for TMARS implants compared with CTAC reconstructions (0 cm. 2. (IQR 0 to 13.1) vs 23.2 cm. 2. (IQR 16.4 to 30.6) (p = 0.009). The mean centre of rotation of the hip of TMARS reconstructions differed by a mean of 11.1 mm (3 to 28) compared with CTAC implants. Conclusion. In using TMARS, more bone is removed, thus achieving more implant-bone apposition within the residual acetabular bone. In CTAC implants, the amount of bone removed is minimal, while the implant-bone apposition is more evenly distributed between the residual acetabulum and the outer cortex of the pelvis. The differences suggest that these implants used to treat pelvic discontinuity might achieve short- and long-term stability through different biomechanical mechanisms. Cite this article: Bone Joint J 2024;106-B(5 Supple B):74–81

Aims. To evaluate how abnormal proximal femoral anatomy affects different femoral version measurements in young patients with hip pain. Methods. First, femoral version was measured in 50 hips of symptomatic consecutively selected patients with hip pain (mean age 20 years (SD 6), 60% (n = 25) females) on preoperative CT scans using different measurement methods: Lee et al, Reikerås et al, Tomczak et al, and Murphy et al. Neck-shaft angle (NSA) and α angle were measured on coronal and radial CT images. Second, CT scans from three patients with femoral retroversion, normal femoral version, and anteversion were used to create 3D femur models, which were manipulated to generate models with different NSAs and different cam lesions, resulting in eight models per patient. Femoral version measurements were repeated on manipulated femora. Results. Comparing the different measurement methods for femoral version resulted in a maximum mean difference of 18° (95% CI 16 to 20) between the most proximal (Lee et al) and most distal (Murphy et al) methods. Higher differences in proximal and distal femoral version measurement techniques were seen in femora with greater femoral version (r > 0.46; p < 0.001) and greater NSA (r > 0.37; p = 0.008) between all measurement methods. In the parametric 3D manipulation analysis, differences in femoral version increased 11° and 9° in patients with high and normal femoral version, respectively, with increasing NSA (110° to 150°). Conclusion. Measurement of femoral version angles differ depending on the method used to almost 20°, which is in the range of the aimed surgical correction in derotational femoral osteotomy and thus can be considered clinically relevant. Differences between proximal and distal measurement methods further increase by increasing femoral version and NSA. Measurement methods that take the entire proximal femur into account by using distal landmarks may produce more sensitive measurements of these differences. Cite this article: Bone Jt Open 2022;3(10):759–766

Talar body fractures are high energy intraarticular injuries that are best management by anatomical reduction and secure fixation to improve outcomes. The talus is relatively inaccessible surgically and requires extensive soft tissue dissection and/or osteotomies to gain adequate open visualisation. There are a small number of case reports on arthroscopic assisted fixation in the literature. This case series reports on the technique and early outcomes of six patients all of whom presented with significant intraarticular displacement and who were managed entirely arthroscopically. The fractures were of the main body of the talus involving the ankle and subtalar joints and all had preoperative CT scans. All six patients underwent posterior ankle and subtalar arthroscopy with cannulated screws used to stabilise the fractures after reduction. Visualisation of the fracture reduction was excellent. After 10 days in a backslab, the patients were protected in a boot and encouraged to actively move their ankles. Weight bearing was permitted once union appeared complete. There were no early complications of infection, avascular necrosis or VTE. There was one patient that had a non-clinically significant migration of a screw. Two patients were lost to follow up early due to being visitors. The mean length of follow up was 12 months in the remainder. The remaining four patients all returned to their preoperative level of activity. All had demonstrable subtalar stiffness. There was no early post-traumatic arthritis. This series represents the largest so far published. The main flaw in this report is the lack of long term follow up. While this report cannot state superiority over open techniques it is a safe, effective and acceptable technique that has significant conceptual benefits

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

The objective of this study was to use patient-specific finite element modeling to measure the 3D interfragmentary strain environment in clinically realistic fractures. The hypothesis was that in the early post-operative period, the tissues in and around the fracture gap can tolerate a state of strain in excess of 10%, the classical limit proposed in the Perren strain theory. Eight patients (6 males, 2 females; ages 22–95 years) with distal femur fractures (OTA/AO 33-A/B/C) treated in a Level I trauma center were retrospectively identified. All were treated with lateral bridge plating. Preoperative computed tomography scans and post-operative X-rays were used to create the reduced fracture models. Patient-specific materials properties and loading conditions (20%, 60%, and 100% body weight (BW)) were applied following our published method.[1]. Elements with von Mises strains >10% are shown in the 100% BW loading condition. For all three loading scenarios, as the bridge span increased, so did the maximum von Mises strain within the strain visualization region. The average gap closing (Perren) strain (mean ± SD) for all patient-specific models at each body weight (20%, 60%, and 100%) was 8.6% ± 3.9%, 25.8% ± 33.9%, and 39.3% ± 33.9%, while the corresponding max von Mises strains were 42.0% ± 29%, 110.7% ± 32.7%, and 168.4% ± 31.9%. Strains in and around the fracture gap stayed in the 2–10% range only for the lowest load application level (20% BW). Moderate loading of 60% BW and above caused gap strains that far exceeded the upper limit of the classical strain rule (<10% strain for bone healing). Since all of the included patients achieved successful unions, these findings suggest that healing of distal femur fractures may be robust to localized strains greater than 10%

The best treatment method of large acetabular bone defects at revision THR remains controversial. Some of the factors that need consideration are the amount of residual pelvic bone removed during revision; the contact area between the residual pelvic bone and the new implant; and the influence of the new acetabular construct on the centre of rotation of the hip. The purpose of this study was to compare these variables in two of the most used surgical techniques used to reconstruct severe acetabular defects: the trabecular metal acetabular revision system (TMARS) and a custom triflanged acetabular component (CTAC). Pre- and post-operative CT-scans were acquired from 11 patients who underwent revision THR with a TMARS construct for a Paprosky IIIB defect, 10 with pelvic discontinuity, at Royal Adelaide Hospital. The CT scans were used to generate computer models to virtually compare the TMARS and CTAC constructs using a semi-automated method. The TMARS construct model was calculated using postoperative CT scans while the CTAC constructs using the preoperative CT scans. The bone contact, centre of rotation, inclination, anteversion and reamed bone differences were calculated for both models. There was a significant difference in the mean amount of bone reamed for the TMARS reconstructions (15,997 mm. 3. ) compared to the CTAC reconstructions (2292 mm. 3. , p>0.01). There was no significant difference between overall implant bone contact (TMARS 5760mm. 2. vs CTAC 5447mm. 2. , p=0.63). However, there was a significant difference for both cancellous (TMARS 4966mm. 2. vs CTAC 2887mm. 2. , p=0.008) and cortical bone contact (TMARS 795mm. 2. vs CTAC 2560mm. 2. , p=0.001). There was no difference in inclination and anteversion achieved. TMARS constructs resulted on average in a centre of rotations 7.4mm more lateral and 4.0mm more posterior. Modelling of two different reconstructions of Paprosky IIIB defects demonstrated potential important differences between all variables investigated

Aims. The aim of this study was to analyze the true costs associated with preoperative CT scans performed for robotic-assisted total knee arthroplasty (RATKA) planning and to determine the value of a formal radiologist’s report of these studies. Methods. We reviewed 194 CT reports of 176 sequential patients who underwent primary RATKA by a single surgeon at a suburban teaching hospital. CT radiology reports were reviewed for the presence of incidental findings that might change the management of the patient. Payments for the scans, including the technical and professional components, for 330 patients at two hospitals were also recorded and compared. Results. There were 82 incidental findings in 61 CT studies, one of which led to a recommendation for additional testing. Across both institutions, the mean total payment for a preoperative scan was $446 ($8 to $3,870). The mean patient payment was $71 ($0 to $2,690). There was wide variation in payments between the institutions. In Institution A, the mean total payment was $258 ($168 to $264), with a mean patient payment of $57 ($0 to $100). The mean technical payment in this institution was $211 ($8 to $856), while the mean professional payment was $48 ($0 to $66). In Institution B, the mean total payment was $636 ($37 to $3,870), with a mean patient payment of $85 ($0 to $2,690). Conclusion. The total cost of a CT scan is low and a minimal part of the overall cost of the RATKA. No incidental findings identified on imaging led to a change in management, suggesting that the professional component could be eliminated to reduce costs. Further studies need to take into account the patient perspective and the wide variation in total costs and patient payments across institutions and insurances. Cite this article: Bone Joint J 2020;102-B(6 Supple A):79–84

Introduction. Our purpose is to analyze the true costs associated with preoperative CT scans performed for robotic assisted TKA planning and also to determine the value of a formal radiologist reading of these studies. Methods. We reviewed 194 CT scans of 176 sequential patients who underwent primary RTKA by a single surgeon at a suburban teaching hospital. CT radiology reports were reviewed for the presence of incidental findings that might result in change of care to the patient. Actual payments for technical and professional components of the CT scans were retrieved for 170 of the 176 patients. Any patient payments for the CT scan were also recorded. Results. In no CT scan report was there any findings other than arthritis in the knee and nothing was identified that lead to a recommendation for any additional testing. The mean total payment for a preoperative CT scan was $253 (range 0 – 912). The mean technical payment was $206 (range 0 – 856). The mean professional component paid was $48 (range 0 – 66). On average patients personally paid $56 (range 0 – 618). In 99/170 cases (58 %), the patients made no payment. For the remaining 71 patients the mean payment made was $134 (range 10 – 618). Discussion and Conclusion. No CT scan identified any clinical problem other than arthritis – this suggests that the professional component cost of this specific CT scan could be eliminated without harm to patients. The cost of the CT scan – mean <$300 – is low and a minimal part of the total overall cost of a primary TKA. Patients understand the value of the CT scan - preoperative advanced imaging helps ensure a precise and accurate intraoperative experience – and they are willing to pay for any of their costs related to this preoperative test. For figures, tables, or references, please contact authors directly

Background: A classification of intra-articular fractures of the distal radius is described on the basis of observations of consistent patterns of fracture fragmentation and displacement. The Melone intra-articular classification system categorizes articular fractures into 4 types, with the medial complex assuming a pivotal position as the cornerstone of both the radiocarpal and distal radio-ulnar joints. The purpose of this study was to classify AO type-C3 fractures according to the Melone classification system using preoperative CT scan data. Methods: We retrospectively reviewed the clinical records of all patients who underwent open reduction and internal fixation (ORIF), according to the AO type-C3 classification. Between September, 2006, and May, 2009, 36 patients and a total of 38 fractures were identified. These intra-articular fractures were also classified according to the Melone classification system using preoperative CT scan data. We also investigated a bone fracture type and surgicalprocedures. Results: Nine fractures were divided into Melone type-1, 17 into type-2 (anterior displacement), 6 into type-2 (posterior displacement), 2 into type-3, and 4 into type-4. Thirty fractures were treated using plate fixation, and 8 fractures were treated using nail fixation. Melone type-1 fractures were usually treated with nail fixation, whereas type-2, -3, and -4 fractures were usually treated using plate fixation. Conclusions: Classification according to the Melone classification system using preoperative CT scan data enables the identification and elucidation of displacement in the major fracture components and enables the establishment of rational guidelines for the management of ORIF

Introduction. Both navigation and instrumented bone referencing use unreliable intraoperative landmark identification or fixed referencing rules which don't reflect patient specific variability. PSI, however, lacks the flexibility to adapt to soft tissue factors not known during preoperative planning, in addition to suffering error from guide fit. A novel method of recreating surgical cut planes that combines preoperative image based identification of landmarks and planning with intraoperative adjustability is under development. This method uses an intraoperative 3D scan of the bone in conjunction with a preoperative CT scan to achieve the desired cuts and so avoids issues of intraoperative identification of landmarks. Method. During TKA surgery, a reference device is placed on the exposed femur. The device is used to position a target block which is pinned to the bone (see Figure 1). The condyles and target block are then scanned, the process taking a second to complete. This 3D scan is filtered to remove extraneous bodies and noise leaving only the bony geometry and target block (see Figure 2). The scan is then reconciled to the known bone geometry taken from preoperative CT scans. A cutting block is then fixed to the target block with a reference array visible to the camera attached. Pre-planned cut planes on a computer model of the bone are compared to the position and configuration of the distal cutting guide. Software guides the surgeon in real-time on the necessary configuration changes required to align the cutting block. The cut is performed on the distal femur, the cutting guide removed from the target-block, and a second scan performed. The software repeats the filtering and alignment processes and provides the surgeon with data on how closely the performed cut matches the alignment planned. Results. Two patients underwent this method alongside traditional alignment techniques. The initial 3D scan of the distal femoral condyles of the patients was matched to their corresponding CT scans. The first case had a mean error of 0.65 mm with 85% of errors falling below a magnitude of 1.16 mm and 58% falling below the case mean (see Figure 3). The second case had a mean error of 0.39 mm with 84% of errors falling below 0.70 mm and 60% falling below the case mean. It should be noted that the error introduced was due to the omission of soft tissue such as the PCL in the CT scan. Exposed bone portions of the scan geometry matched well with the CT scan, with error magnitudes significantly below the mean. Discussion. The ability to obtain useful surgical alignment using preoperatively identified landmarks, alongside the small space requirements of a modern 3D scanner is sharply contrasted against the large space requirements and need for intraoperative probing of traditional navigation systems. Likewise, the use of preoperative planning and landmark identification to overcome intraoperative data capture variability mirrors that of PSI, but allows for potentially much greater accuracy of execution as the issue of guide fit and topology variation is avoided while intraoperative flexibility is maintained

Aims. The aim of this study was to evaluate the accuracy of implant placement when using robotic assistance during total hip arthroplasty (THA). Patients and Methods. A total of 20 patients underwent a planned THA using preoperative CT scans and robotic-assisted software. There were nine men and 11 women (n = 20 hips) with a mean age of 60.8 years (. sd. 6.0). Pelvic and femoral bone models were constructed by segmenting both preoperative and postoperative CT scan images. The preoperative anatomical landmarks using the robotic-assisted system were matched to the postoperative 3D reconstructions of the pelvis. Acetabular and femoral component positions as measured intraoperatively and postoperatively were evaluated and compared. Results. The system reported accurate values for reconstruction of the hip when compared to those measured postoperatively using CT. The mean deviation from the executed overall hip length and offset were 1.6 mm (. sd. 2.9) and 0.5 mm (. sd. 3.0), respectively. Mean combined anteversion was similar and correlated between intraoperative measurements and postoperative CT measurements (32.5°, . sd. 5.9° versus 32.2°, . sd. 6.4°; respectively; R. 2. = 0.65; p < 0.001). There was a significant correlation between mean intraoperative (40.4°, . sd. 2.1°) acetabular component inclination and mean measured postoperative inclination (40.12°, . sd. 3.0°, R. 2. = 0.62; p < 0.001). There was a significant correlation between mean intraoperative version (23.2°, . sd. 2.3°), and postoperatively measured version (23.0°, . sd. 2.4°; R. 2. = 0.76; p < 0.001). Preoperative and postoperative femoral component anteversion were significantly correlated with one another (R. 2. = 0.64; p < 0.001). Three patients had CT scan measurements that differed substantially from the intraoperative robotic measurements when evaluating stem anteversion. Conclusion. This is the first study to evaluate the success of hip reconstruction overall using robotic-assisted THA. The overall hip reconstruction obtained in the operating theatre using robotic assistance accurately correlated with the postoperative component position assessed independently using CT based 3D modelling. Clinical correlation during surgery should continue to be practiced and compared with observed intraoperative robotic values. Cite this article: Bone Joint J 2018;100-B:1303–9

The discussion of outpatient unicompartmental knee arthroplasty (UKA) requires proof that it can be done safely and effectively, and also begs the question of whether it can be performed in an ambulatory surgery center (ASC) rather than a general hospital (which raises costs and is typically less efficient). Successful outpatient UKA requires carefully crafted algorithms/protocols, home support, preoperative planning and preparation, expectation management, risk stratification (not everyone is a candidate), perioperative pain management and buy-in from patients, support networks and the health care team. Relatively little data is available on the feasibility, safety and potential cost savings associated with this shift in care. We evaluated the costs and short term outcomes and complications of 150 consecutive UKAs performed in an ASC compared to those done in a general hospital both on an inpatient and outpatient basis. Determination of the setting of the outpatient surgery was made based on geographic preference by the patients; otherwise choice of inpatient or outpatient surgery in the hospital was left to the discretion of the surgeon and was primarily based on the patients' comorbidity profile and circumstances of home help. Total direct facility costs were calculated, including institutional supplies and services, anesthesia services, implants, additional PACU medications and services required, and costs associated with operating room use. Only total cost was evaluated, as it is the most consistent cost variable amongst the two institutions evaluated. The mean total direct cost of UKA in a general community hospital with an overnight stay was 1.24 and 1.65 times greater than the cost of UKA performed at the same hospital or an ASC on an outpatient basis, respectively. The mean total direct cost of outpatient UKA in a general hospital was 1.33 times greater than the mean total cost of UKA performed in an ASC. Semi-autonomous robotic technology has been introduced to optimise accuracy of implant positioning and soft tissue balance in UKA, with the expectation of resultant improvement in durability and implant survivorship. Currently, nearly 20% of UKA's in the U.S. are being performed with robotic assistance. It is anticipated that there will be substantial growth in market penetration over the next decade, projecting that nearly 37% of UKA's and 23% of TKA's will be performed with robotics in 10 years (Medical Device and Diagnostic Industry, March 5, 2015). First generation robotic technology improved substantially implant position compared to conventional methods; however, high capital costs, uncertainty regarding the value of advanced technologies, and the need for preoperative CT scans were barriers to broader adoption. Newer image-free robotic technology offers an alternative method for further optimizing implant positioning and soft tissue balance without the need for preoperative CT scans and with price points that make it suitable for use in an ASC. Currently, as a result of cost and other practical issues, <1% of first generation robotic technologies are being used in ASC's. Alternatively, more than 35% of second generation robotic systems are in use in ASC's for UKA, due to favorable pricing. In conclusion, UKA can be safely performed in the outpatient setting in select patients. Additionally, we demonstrated a substantial cost savings when UKA is performed in an outpatient setting and care is shifted from a general community hospital to an ASC. Finally, robotics can be utilised to optimise accuracy of implant placement and soft tissue balance in UKA, and newer image-free robotic technology is cost effective for outpatient UKA

The authors are not aware of any research comparing computed tomography (CT) and avascular necrosis (AVN) of the scaphoid bone. The primary aim of our study was to investigate the use of longitudinal CT in predicting AVN of the proximal pole of the scaphoid, and subsequent fracture nonunion following internal fixation. Thirty-two patients operated on by the senior author for scaphoid fracture were included. Preoperative CT scans were independently assessed for deformity, comminution, fracture position, proximal pole sclerosis, and bridging trabeculae. Intra-operative biopsy of the proximal pole was assessed independently by a blinded musculoskeletal histologist. AVN was determined by histology of a proximal pole biopsy, using the criteria described by Ficat. Post-operative CT scan was utilised to determine fracture union. Preoperative CT features which significantly correlated with AVN were, increased radiodensity of the proximal pole, the absence of any bridging trabeculae comminution, dorsal cortical angle, proximal fracture and age less than 20. Features predictive of subsequent nonunion were fractures of the proximal, increased radiodensity of the proximal pole, and AVN. Preoperative CT scan findings are significantly correlated with histologically confirmed AVN and fracture union. Preoperative longitudinal CT scan is of significant prognostic value and should be considered to assist in predicting outcome and assessing treatment options

Purpose of the study: The purpose of rotating the femoral piece, using an indepenent cut strategy, is to «correct» for epiphyseal torsion of the distal femur and thus obtain a biepicondylar axis parallel to the posterior bicondylar axis. It is known however that epiphyseal torsion of the distal femur is highly variable from one individual to another. Intraoperative identification of the biepicondylar line enables appropriate rotation, as long as the data collected are reliable. The purpose of this study was to determine the reliability of intraoperative biepicondylar axis measurements made with navigation systems and to compare the results with the preoperative scan taken as the gold standard. Material and methods: This prospective study included 60 degenerative knees undergoing total knee arthroplasty. The angle of epiphyesael rotation of the distal femur was measured on the preoperative computed tomography scan and intraoperatively with the navigation system which identified the biepicondylar line and the posterior bicondylar line. Statistical regression lines were determined. Results: The rotation measured on the preoperative scan was 7.1±2.4° and by the intraoperative navigation system 3.2±4.3°. There was a very weak statistical correlation between the preoperative measurement and the intraoperative navigation measurement (p=0.234, R =0.320). Discussion: Intraoperative identification of the biepicondylar axis is not reliable. Navigation does not enable an accurate assessment of the distal epiphyseal torsion of the femur and thus the proper rotation to give to the femoral piece. The only reliable measurement of the epiphyseal rotation of the distal femur is made on the preoperative computed tomography

Preoperative planning is a crucial step for total hip arthroplasty (THA), and 2D X-ray images are commonly used. The planning aims to provide the correct implant size, restore functional biomechanical conditions and avoid early complication such as dislocation, leg length discrepancy or abductors insufficiency. Limitations of 2D planning, besides the low accuracy in sizing, concerns the inability of planning the anteversion of both acetabular and femoral component on axial plane. Also, the verification of the planning intraoperatively is wholly left to qualitative measurements and the surgeon's experience. The need for having a more accurate and functional preoperative planning has been addressed using 3D models. The MyHip Planner (MHP) (Medacta International, Castel San Pietro, Switzerland), is a preoperative planning software which through artificial intelligent algorithm converts the CT scans into a 3D model that perfectly match the patient's anatomy. Then, automatic positioning of the implants is performed following the personal settings of the surgeon which will check and validate the planning, a personalized simulation of six daily activities to detect impingement of implants and bones. The MyHip Verifier (MHV) intraoperatively verifies the execution of the planning in terms of leg length and offset using two fluoroscopic images. Also, the size and cup angles can be calculated. The purpose of the present study was to validate the accuracy of the MHP [Fig 1] and MHV [Fig 2]. The dataset consisted of 13 patients who underwent primary uncemented THA. Each patient had a preoperative CT scan, intraoperative fluoroscopy, and postoperative CT scan after the surgery. The CT protocol used was low radiation (0,2 mm slicing for the pelvis, 0,5 mm for knees and ankles). The patients have been preoperatively planned used the MPH, and the accuracy of the components size prediction has been evaluated by comparing the preoperative planned values with the surgical reports. The MVH calculated the leg length and offset in terms of the difference between the preoperative and postoperative position of the femur concerning the pelvis. The accuracy of the measurements has been evaluated using postoperative CT scans. The MPH was able to predict the implanted size in 83% of the patient for the femoral stem and 96% for the acetabular component. The accuracy of the MVH in measuring the leg length was under 2 mm (1,6 ± 0,7 mm) while the offset was 2,5±1,6 mm. The cup angles were 5±1,1deg and 2,3±1,3deg for the anteversion and inclination, respectively. The average cup anteversion was 28,3°, mean cup inclination was 42,6°; femoral offset and leg length was restored in 96,5% of patients within a range of ±3 mm concerning the preoperative position. The results demonstrated the reliability of the MPH in predicting the implant size, and the accuracy of the MVH to verify the execution of the plan intraoperatively. The two software can be used in the clinical routine to improve the clinical outcome in THA. Limitations of this study are represented mainly by the small cohort of patients involved. For any figures or tables, please contact the authors directly

Image-guided TKR requires a three-dimensional model of the patient, traditionally provided by preoperative CT scans. Recent developments have focused on navigation systems that eliminate the need for preoperative CT scan. This paper aims to assess the comparative accuracy of prosthesis planning using CT-based and CT-free navigation systems. Four half-body cadavers were implanted with fiducial markers, four per limb, to provide accurate registration points. Eight orthopaedic surgeons then proceeded to plan the anatomy on each limb twice, using CT scan. The CT-free planning involved digitalisation of the fiducial markers, followed by attachment of trackers to the femur and tibia. Several kinematic and digitalisation steps were taken to produce a set of anatomical coordinates for each limb. Again each surgeon repeated this procedure twice on each limb. Calculation of reproducibility of the mechanical axis as defined by both methods was thus possible. The overall differences related to varus/valgus placements between the two methods were minor, with a mean of 0.04° (−0.20° to 0.28°) for the femur and 0.19° (−0.009° to 0.39°) for the tibia. The mean angular difference in flexion/extension placement was –0.27° (−0.59° to −0.08°) for the femur and −0.08° (−0.40° to 0.24°) for the tibia. Results for varus/valgus and flexion/extension, as measured by CT-based and CT-free systems, showed a high degree of concordance. There was no observable bias in either system, as shown by the approximately equal spread of data points on either side of the line of equality. The data show a high degree of reproducibility between CT-free navigation systems and CT-based procedures