Mixed Reality and Artificial Intelligence: A Holistic Approach to Multimodal Visualization and Extended Interaction in Knee Osteotomy.

OBJECTIVE: Recent advancements in augmented reality led to planning and navigation systems for orthopedic surgery. However little is known about mixed reality (MR) in orthopedics. Furthermore, artificial intelligence (AI) has the potential to boost the capabilities of MR by enabling automation and personalization. The purpose of this work is to assess Holoknee prototype, based on AI and MR for multimodal data visualization and surgical planning in knee osteotomy, developed to run on the HoloLens 2 headset. METHODS: Two preclinical test sessions were performed with 11 participants (eight surgeons, two residents, and one medical student) executing three times six tasks, corresponding to a number of holographic data interactions and preoperative planning steps. At the end of each session, participants answered a questionnaire on user perception and usability. RESULTS: During the second trial, the participants were faster in all tasks than in the first one, while in the third one, the time of execution decreased only for two tasks ("Patient selection" and "Scrolling through radiograph") with respect to the second attempt, but without statistically significant difference (respectively [Formula: see text] = 0.14 and [Formula: see text] = 0.13, [Formula: see text]). All subjects strongly agreed that MR can be used effectively for surgical training, whereas 10 (90.9%) strongly agreed that it can be used effectively for preoperative planning. Six (54.5%) agreed and two of them (18.2%) strongly agreed that it can be used effectively for intraoperative guidance. DISCUSSION/CONCLUSION: In this work, we presented Holoknee, the first holistic application of AI and MR for surgical planning for knee osteotomy. It reported promising results on its potential translation to surgical training, preoperative planning, and surgical guidance. Clinical and Translational Impact Statement - Holoknee can be helpful to support surgeons in the preoperative planning of knee osteotomy. It has the potential to impact positively the training of the future generation of residents and aid surgeons in the intraoperative stage.

Use of oxygen-ozone therapy to improve the effectiveness of antibiotic treatment on infected arthroplasty: protocol for a superiority, open-label, multicentre, randomised, parallel trial.

INTRODUCTION: Surgical site infections still remain a major public health challenge and have become an increasing universal risk, especially for the implantation of orthopaedic devices.Unfortunately, the discovery and increasingly widespread use (especially the misuse) of antibiotics have led to the rapid appearance of antibiotic-resistant strains today; more and more infections are caused by microorganisms that fail to respond to conventional treatments.Oxygen-ozone therapy has been extensively used and studied for decades across various potential medical applications and has provided consistent effects with minimal side effects.This study aims to determine the superiority of oxygen-ozone therapy in combination with oral antibiotic therapy in patients with wound infections after an orthopaedic device implantation when compared with antibiotic therapy alone. METHODS AND ANALYSIS: This is an open-label, multicentre, randomised, parallel-group study that aims to assess the efficacy and safety of oxygen-ozone therapy in combination with oral antibiotic therapy to treat infections in patients (male or female aged ≥18 years) having undergone surgery for the implant of an orthopaedic device. Patients must have at least one (but no more than three) postoperative wounds in the site of surgery (ulcers, eschars and sores) and at least one symptom (pain, burning, redness and malodour) and at least one sign (erythema, local warmth, swelling and purulent secretion) of infection of at least moderate intensity (score ≥2) in the target lesion at the screening visit (patients with wounds without signs of localised infection or with undermining wounds will be excluded).Patients (n=186) will be recruited from five Italian hospitals and studied for 7 weeks. All will be assigned to one of the two treatment groups according to a web-based, centralised randomisation procedure and placed into either the (1) intervention: oxygen-ozone therapy 2-3 times a week for 6 weeks (for a maximum of 15 sessions) simultaneously with an appropriate oral antibiotic therapy prescribed at baseline or (2) control: oral antibiotic therapy prescribed at baseline.The primary outcome is the efficacy and superiority of the treatment (ozone and oral antibiotic therapies); secondary outcomes include the resolution of signs and symptoms, modifications in lesion size and the treatment's safety and tolerability. ETHICS AND DISSEMINATION: This study has been reviewed and approved by the responsible Independent Ethics Committee (IEC) of COMITATO ETICO CAMPANIA NORD, located at 'Azienda Ospedaliera San Giuseppe Moscati di Avellino'.After completion of the study, the project coordinator will prepare a draft manuscript containing the final results of the study on the basis of the statistical analysis. The manuscript will be derived by the co-authors for comments, and after revision, it will be sent to a major scientific journal. Findings will be disseminated via online and print media, events and peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04787575.

Combined Edge Loss UNet for Optimized Segmentation in Total Knee Arthroplasty Preoperative Planning.

Bone segmentation and 3D reconstruction are crucial for total knee arthroplasty (TKA) surgical planning with Personalized Surgical Instruments (PSIs). Traditional semi-automatic approaches are time-consuming and operator-dependent, although they provide reliable outcomes. Moreover, the recent expansion of artificial intelligence (AI) tools towards various medical domains is transforming modern healthcare. Accordingly, this study introduces an automated AI-based pipeline to replace the current operator-based tibia and femur 3D reconstruction procedure enhancing TKA preoperative planning. Leveraging an 822 CT image dataset, a novel patch-based method and an improved segmentation label generation algorithm were coupled to a Combined Edge Loss UNet (CEL-UNet), a novel CNN architecture featuring an additional decoding branch to boost the bone boundary segmentation. Root Mean Squared Errors and Hausdorff distances compared the predicted surfaces to the reference bones showing median and interquartile values of 0.26 (0.19-0.36) mm and 0.24 (0.18-0.32) mm, and of 1.06 (0.73-2.15) mm and 1.43 (0.82-2.86) mm for the tibia and femur, respectively, outperforming previous results of our group, state-of-the-art, and UNet models. A feasibility analysis for a PSI-based surgical plan revealed sub-millimetric distance errors and sub-angular alignment uncertainties in the PSI contact areas and the two cutting planes. Finally, operational environment testing underscored the pipeline's efficiency. More than half of the processed cases complied with the PSI prototyping requirements, reducing the overall time from 35 min to 13.1 s, while the remaining ones underwent a manual refinement step to achieve such PSI requirements, performing the procedure four to eleven times faster than the manufacturer standards. To conclude, this research advocates the need for real-world applicability and optimization of AI solutions in orthopedic surgical practice.

Traditional Cultures versus Next Generation Sequencing for Suspected Orthopedic Infection: Experience Gained from a Reference Centre.

(Background) The diagnosis and the antimicrobial treatment of orthopedic infection are challenging, especially in cases with culture-negative results. New molecular methods, such as next-generation sequencing (NGS), promise to overcome some limitations of the standard culture, such as the detection of difficult-to-grow bacteria. However, data are scarce regarding the impact of molecular techniques in real-life scenarios. (Methods) We included cases of suspected orthopedic infection treated with surgery from May 2021 to September 2023. We combined traditional cultures with NGS. For NGS, we performed a metagenomic analysis of ribosomal 16s, and we queried dedicated taxonomic libraries to identify the species. To avoid false positive results, we set a cut-off of 1000 counts of the percentage of frequency of reads. (Results) We included 49 patients in our study. Our results show the presence of bacteria in 36/49 (73%) and 29/49 (59%) cases studied with NGS and traditional cultures, respectively. The concordance rate was 61%. Among the 19/49 discordant cases, in 11/19 cases, cultures were negative and NGS positive; in 4/19, cultures were positive and NGS negative; and in the remaining 4/19, different species were detected by traditional cultures and NGS. (Conclusions) Difficult-to-grow microorganisms, such as slow-growing anaerobic bacteria, were better detected by NGS compared to traditional culture in our study. However, more data to distinguish between true pathogens and contaminants are needed. NGS can be an additional tool to be used for the diagnosis of orthopedic infections and the choice of appropriate antimicrobial therapy.

CEL-Unet: a novel CNN architecture for 3D Segmentation of Knee Bones affected by Severe Osteoarthritis for PSI-Based Surgical Planning.

Unet architectures are promising deep learning networks exploited to perform the automatic segmentation of bone CT images, in line with their ability to deal with pathological deformations and size-varying anatomies. However, bone degeneration, like the development of irregular osteophytes as well as mineral density alterations might interfere with this automated process and demand extensive manual refinement. The aim of this work is to implement an innovative Unet variant, the CEL-Unet, to improve the femur and tibia segmentation outcomes in osteoarthritic knee joints. In this network the decoding path is split into a region and contour-aware branch to increase the prediction reliability in such pathological conditions. The comparison between the segmentation results achieved with a standard Unet and its novel variant (CEL-Unet) was performed as follows: the Unet was trained with 5 different loss functions: Dice Loss, Focal Loss, Exponential Logarithmic Loss, Double Cross Entropy Loss and Distanced Cross Entropy loss. The CEL-Unet was instead trained with two loss functions, one for each of the network outputs, namely Mask and Edge, yielding the so-called Combined Edge Loss (CEL) function. A set of 259 knee CT scans was used to train the model and test segmentation performance. The CEL-Unet outperformed all other Unet-based models, reaching the highest Jaccard values of about 0.97 and 0.96 on femur and tibia, respectively. Clinical Relevance- With the increasing rate of Total Knee Arthoplasty deep learning-based methods can achieve fast accurate and automatic 3D segmentation of the knee joint bones to enhance new costumized pre-operative planning.

Septic arthritis following joint injections: a 17 years retrospective study in an Academic General Hospital.

BACKGROUND: Septic arthritis following intra-articular infiltrations is an uncommon devastating complication correlated  to high costs for the health service and often to poor outcomes. The purpose of this study is to assess a 17-years experience in a single academic multispecialist hospital managing this uncommon complication in Orthopaedic practice. METHODS: Patients with diagnosis of septic arthritis following joint injections treated in our hospital from January 2002 to December 2019 were included in the study. Clinical and demographic data, pathogens, injected agent, conservative/surgical treatments were reviewed. Patient were classified according to the ore operative Charlson Comorbidity Index (CCI) and the Cierny-Mader Classification(CMC). Furthermore follow-up outcome and time occurred to infection eradication were registered. RESULTS: We included in the study 11 patients with a median age of 74 years old (IQR= 61.5 - 79). The median CCI was 3  (IQR= 2 - 5) and the majority of patients belong to CMC = B class. Septic arthritis occurred mainly following corticosteroids injections and more frequently involving knees. The pathogen more often isolated was Staphylococcus aureus. Five (45%) patients referred an history of multiple intrarticular injections. 7 patients (64%) had a complete resolution following an arthroscopic debridement, 4 (36%) patients underwent to a 2-stage replacement and one of them hesitated in an arthrodesis because of a recurrent periprothesic joint infection and extensor apparatus insufficiency. CONCLUSION: The authors observed a potential increased risk of septic arthritis following joint injection in patients with history of multiple injections and poor health/immunological conditions. They recommend an early arthroscopic debridement as the treatment of choice especially in septic knees  performed in a multispecialist dedicated center.

SARS-CoV-2 in the knee joint: a cadaver study.

OBJECTIVES: Despite the considerable research efforts being made to learn more about COVID-19, little is known about the presence of SARS-CoV-2 genetic material in biological fluids other than respiratory droplets, blood, and feces. The aim of this post-mortem study was to assess the presence of SARS-CoV-2 RNA in the knee synovial fluid, synovial tissue, and bone tissue of COVID-19 patients in order to discover whether the joint is a possible route of transmission during orthopaedic surgical procedures, and clarify the possible role of SARS-CoV-2 as a directly arthritogenic virus. METHODS: Post-mortem synovial fluid, synovial tissue and bone tissue samples were collected from the knees of five patients who died of COVID-19 in our hospital between September and October 2020, and analysed for the presence of SARS-CoV-2 using a commercial real-time polymerase chain reaction (RT-PCR) panel. Quantitative RT-PCR was used to test post-mortem nasopharyngeal swabs of all of the patients. RESULTS: No SARS-CoV-2 RNA was detected in any of the knee samples, despite the positivity of the throat swab. CONCLUSIONS: Our findings indicate that SARS-CoV-2 was not detected in knee synovial fluid, synovial membrane or bone. This makes it unlikely that these are potential sources of contagion, and suggests that SARS-CoV-2 is not directly arthritogenic.

Postoperative outcomes in total hip arthroplasty following femoral head avascular necrosis in HIV-positive patients.

BACKGROUND: Few clinical studies have been published reporting the clinical outcomes of total hip replacement (THA) in HIV-positive patients affected by femoral head avascular necrosis (AVN) often with controversial results and often without any correlation with the immunological patient status. Our study aim is to retrospectively review the outcome of a HIV-positive patient series. MATERIAL AND METHODS: 24 THAs perfomed between 2007 and  2017 were assessed in the study. All patients have been classified with Charlson Comorbidity Index (CCI) and the CDC (Center for Disease Control and Prevention) HIV classification.  At the latest follow-up each patient have been evaluated using Harris Hip Score (HHS), WOMAC score, a numerical pain rating scale (NRS) and procedure-related complications were collected. RESULTS: At a mean mean follow up of 96,41 months the mean WOMAC score was 91,66  and the mean Harris Hip Score was 86,77 with  excellent results in 18 hips, good in 1 and poor in the 5. Post-operative complications were reported in 7 hips, 3 patients developed a periprosthetic joint infection (PJI) in patients with low CD4+ count and history of intravenous drug consumption. CONCLUSION: We registered a good outcome in HIV patient with femoral head AVN treated with Total Hip replacement. However, we reported a significant increase in complications and revision rate especially referred to PJI, in patient with history of intravenous drug consumption and low CD4+ count. The authors advocate further prospective multicentric studies with larger population in the future. (www.actabiomedica.it).

Case series of traumatic neglected Extensor Hallucis Longus lacerations: choice of surgical treatment based on injury type.

BACKGROUND AND AIM: Extensor Hallucis Longus (EHL) tendon rupture is a rare injury of the foot, representing only 1% of overall tendon rupture. Early diagnosis and surgical repair are recommended but there is still no consensus regarding the ideal treatment. The purpose of this study was to evaluate a case series of patients with neglected extensor hallucis longus (EHL) tendon rupture. METHODS: We report a case series of 3 patients affected by traumatic neglected EHL lacerations treated with reconstructive surgery using tissue scaffolds, between November 2019 and May 2020. Demographics data, mechanism of injury, zone of injury, tendon gap, time to surgery, type of surgical repair, preoperative and postoperative functional score were collected with a minimum follow-up of 8 months. RESULTS: The zone of injury (according to Al-Qattan classification) involved was in 1 case zone 2, in 1 case zone 4 and in the last case zone 5. The mean value of intraoperative tendon gap was of 3,4 cm. The elapsed time from injury to surgery was an average of 3,3 months. One tendon transfer surgery and two primary repairs with Krakow fashion were performed, all augmented with tissue scaffolds. The mean preoperative and postoperative American Orthopedic Foot and Ankle Society (AOFAS) scores were, respectively, 43 and 97. CONCLUSIONS: Our results highlight good functional result and satisfaction with active extension of the hallux restored in all patients. According to our experience, we recommend choosing reconstruction technique basing on the topographic zone of lesion and intraoperative tendon gap.

Humeral head necrosis associated to shaft non-union with massive bone loss: a case report.

Humeral non-union is a rare complication in shaft fractures, as well as humeral head necrosis is a possible complication in fracture involving the proximal third especially in four-part fractures. The presence of head osteonecrosis and diaphyseal non-union in the same arm represents a formidable challenge for an orthopaedic surgeon. We could not find any similar report in the literature dealing with this issue thus far. We present a case of a 65 years old woman referred to our hospital being affected by an atrophic humeral diaphyseal non-union with a massive bone loss (>10cm) associated to a humeral head osteonecrosis following a previous surgical procedures with a clear loosening of the hardware. At our institution,she was treated with hardware removal and insertion of a diaphyseal antibiotic spacer with Gentamycin for 2 months suspecting an active septic process at the union site despite negative cultural exams. Finally, she was treated with a cemented modular humeral megaprosthesis. At 20 months follow up, the patient, despite a reduced shoulder range of motion, referred to a pain-free recovery to an almost normal lifestyle, including car driving with no major disturbances. This case suggests that, in extreme selected cases following several failed treatments, megaprosthesis can represent a viable solution, especially in huge bone loss associated to joint degeneration, to ensure an acceptable return to a normal lifestyle.

Predicting Knee Joint Instability Using a Tibio-Femoral Statistical Shape Model.

Statistical shape models (SSMs) are a well established computational technique to represent the morphological variability spread in a set of matching surfaces by means of compact descriptive quantities, traditionally called "modes of variation" (MoVs). SSMs of bony surfaces have been proposed in biomechanics and orthopedic clinics to investigate the relation between bone shape and joint biomechanics. In this work, an SSM of the tibio-femoral joint has been developed to elucidate the relation between MoVs and bone angular deformities causing knee instability. The SSM was built using 99 bony shapes (distal femur and proximal tibia surfaces obtained from segmented CT scans) of osteoarthritic patients. Hip-knee-ankle (HKA) angle, femoral varus-valgus (FVV) angle, internal-external femoral rotation (IER), tibial varus-valgus (TVV) angles, and tibial slope (TS) were available across the patient set. Discriminant analysis (DA) and logistic regression (LR) classifiers were adopted to underline specific MoVs accounting for knee instability. First, it was found that thirty-four MoVs were enough to describe 95% of the shape variability in the dataset. The most relevant MoVs were the one encoding the height of the femoral and tibial shafts (MoV #2) and the one representing variations of the axial section of the femoral shaft and its bending in the frontal plane (MoV #5). Second, using quadratic DA, the sensitivity results of the classification were very accurate, being all >0.85 (HKA: 0.96, FVV: 0.99, IER: 0.88, TVV: 1, TS: 0.87). The results of the LR classifier were mostly in agreement with DA, confirming statistical significance for MoV #2 (p = 0.02) in correspondence to IER and MoV #5 in correspondence to HKA (p = 0.0001), FVV (p = 0.001), and TS (p = 0.02). We can argue that the SSM successfully identified specific MoVs encoding ranges of alignment variability between distal femur and proximal tibia. This discloses the opportunity to use the SSM to predict potential misalignment in the knee for a new patient by processing the bone shapes, removing the need for measuring clinical landmarks as the rotation centers and mechanical axes.

Clinical outcome before and after COVID-19 quarantine in patients affect of knee and hip osteoarthritis.

BACKGROUND: The emergency caused by COVID-19 Pandemia has resulted in a complete suspension and consequent delay of common planned surgery such total hip replacement in patients affect by osteoarthritis. At the same time, the issue of the quarantine imposed changes to the normal lifestyle of these patients. The purpose of our study is to evaluate how the presence of these two factors affect the quality of live of patients living in the Italian red zone. METHODS: From outpatient pre-operative assessment we collect data about: demographic data, WOMAC score, NRS (Numeric rating scale 0-10), PCS SF12 and MCS SF12 score. Selected patients were therefore contacted by telephone call and re-assess using the same score. In addition, patients were asked if they intended to undergo the planned surgery again despite the current emergency Results:  14 patient have been recruited for the study. Male/female ration was 10/4, mean age was 70 years. Pre operative outpatient assessment mean WOMAC score was 44,86 (SD ± 8,52) , mean NRS was 8,07 (SD ± 1,33), PCS SF12 was  30,33 (SD ± 5,0) and MCS SF12 was 40,95 (SD ± 3,51).  At re-evalutation the mean WOMAC score was 32,86 (SD ± 17,88) , mean NRS was 5,79 (SD ± 3,66), PCS SF12 was  39,9 (SD ± 3,70) and MCS SF12 was 50,14 (SD ± 6,86) Conclusion:  The exceptionale pandemic from Covid-19 has profoundly changed our lifestyle, impacting normal daily activities but also on regular surgical activity in patients affected by osteoarthritis. Our study suggested that the lifestyle changes imposed by the situation led to an improvement of clinical score. This shows how an exceptional event can affect many aspects of daily life.

Representative 3D shape of the distal femur, modes of variation and relationship with abnormality of the trochlear region.

The anatomy of the distal femur has a predominant influence on the mechanics of both patello- and tibio-femoral joints. Especially, the morphological degeneration of the trochlear region dramatically affects the overall knee biomechanics and, from a clinical point of view, the staging of such a degeneration is fundamental to tailor the optimal therapeutic solution. The description of morphological variability and pathological inter-subject differences of the trochlea can be achieved by means of statistical shape modeling of a set of three-dimensional surfaces. This representation encodes information, spread into the dataset, in terms of modes of variations that model global, regional and even local morphological features. In view of that, the aim of this study was to develop a statistical shape model of the distal femur to capture the variability of the trochlear region into specific modes of variation and to study the interplay between the variation of the trochlea and the condylar regions. Using CT scans of patients affected by different levels of abnormality of the trochlear region, the distal femur geometries were co-registered to a reference shape using the pair-wise correspondence approach and principal component analysis provided the key modes of variation (MoVs). Apart from the first two MoVs, which described the global magnitude of the femur and the shaft length, the main following ones showed high correlation with sulcus depth (r2=0.70), sulcus angle (r2=0.70), lateral trochlear inclination (r2=0.66), and height of the two condylar facets in the anterior direction (r2=0.66), whose abnormal variations are typical signs of trochlear degeneration. High interplay between trochlear abnormalities and notch width (r2=0.71), lateral condylar size (r2=0.67), and medial condylar size (r2=0.99) was found. Interestingly, the model predicted morphological associations not included in the training dataset, nonetheless difficult to demonstrate physiologically. Interestingly from a biomechanical point of view, the distribution of some MoVs was found statistically different across the patients featuring physiological and pathological ranges of hip-knee-ankle alignment, femoral internal-external rotation and tibial slope. However, no linear correlation was found between the angular indexes and such MoVs. As a result, we can assert that statistical modeling of the distal femur are to date an effective way to visualize and quantify abnormalities of the trochlear regions supporting the introduction of advanced analysis, diagnostic and treatment support tools to elucidate physiologic and pathological variability in the morphology, to drive the staging and assist the selection of the optimal treatment option tailored to the patient.

Pair-wise vs group-wise registration in statistical shape model construction: representation of physiological and pathological variability of bony surface morphology.

Statistical shape models (SSM) of bony surfaces have been widely proposed in orthopedics, especially for anatomical bone modeling, joint kinematic analysis, staging of morphological abnormality, and pre- and intra-operative shape reconstruction. In the SSM computation, reference shape selection, shape registration and point correspondence computation are fundamental aspects determining the quality (generality, specificity and compactness) of the SSM. Such procedures can be made critical by the presence of large morphological dissimilarities within the surfaces, not only because of anthropometrical variability but also mainly due to pathological abnormalities. In this work, we proposed a SW pipeline for SSM construction based on pair-wise (PW) shape registration, which requires the a-priori selection of the reference shape, and on a custom iterative point correspondence algorithm. We addressed large morphological deformations in five different bony surface sets, namely proximal femur, distal femur, patella, proximal fibula and proximal tibia, extracted from a retrospective patient dataset. The technique was compared to a method from the literature, based on group-wise (GW) shape registration. As a main finding, the proposed technique provided generalization and specificity median errors, for all the five bony regions, lower than 2 mm. The comparative analysis provided basically similar results. Particularly, for the distal femur that was the shape affected by the largest pathological deformations, the differences in generalization, specificity and compactness were lower than 0.5 mm, 0.5 mm, and 1%, respectively. We can argue the proposed pipeline, along with the robust correspondence algorithm, is able to compute high-quality SSM of bony shapes, even affected by large morphological variability.

Non artheritic bilateral anterior ischaemic optic neuropathy (NAION) as devastating complication following Total Hip Arthroplasty: a case report.

INTRODUCTION: Postoperative vision loss (PVL) is an extremely rare complication following major surgical procedures. Patients with systemic hypertension, diabetes, coronary diseases and smokers are generally predisposed to this complication. More frequently, it is caused by ischemic optic neuropathy (ION), central retinal artery occlusion or retinal vein occlusion. Rare cases of unilateral PVL following total joint arthroplasty surgery have been recently described in literature. CASE REPORT: This case report describes the first reported bilateral non-arteritic anterior ischemic optic neuropathy (NAION), which occurred 3 days following a total hip arthroplasty with a consequent post-operative hypotension. CONCLUSIONS: Orthopedic surgeons should be aware that in hip joint replacement procedures, selected patients present an higher risk of ION following intra/postoperative hypotension and prolonged surgical times. (www.actabiomedica.it).

Stacked sparse autoencoder networks and statistical shape models for automatic staging of distal femur trochlear dysplasia.

BACKGROUND: The quantitative morphological analysis of the trochlear region in the distal femur and the precise staging of the potential dysplastic condition constitute a key point for the use of personalized treatment options for the patella-femoral joint. In this paper, we integrated statistical shape models (SSM), able to represent the individual morphology of the trochlea by means of a set of parameters and stacked sparse autoencoder (SSPA) networks, which exploit the parameters to discriminate among different levels of abnormalities. METHODS: Two datasets of distal femur reconstructions were obtained from CT scans, including pathologic and physiologic shapes. Both of them were processed to compute SSM of healthy and dysplastic trochlear regions. The parameters obtained by the 3D-3D reconstruction of a femur shape were fed into a trained SSPA classifier to automatically establish the membership to one of three clinical conditions, namely, healthy, mild dysplasia, and severe dysplasia of the trochlea. The validation was performed on a subset of the shapes not used in the construction of the SSM, by verifying the occurrence of a correct classification. RESULTS: A major finding of the work is that SSM are able to represent anomalies of the trochlear geometry by means of specific eigenmodes of variation and to model the interplay between morphologic features related to dysplasia. Exploiting the patient-specific morphing parameters of SSM, computed by means of a 3D-3D reconstruction, SSPA is demonstrated to outperform traditional discriminant analysis in classifying healthy, mild, and severe trochlear dysplasia providing 99%, 97%, and 98% accuracy for each of the three classes, respectively (discriminant analysis accuracy: 85%, 89%, and 77%). CONCLUSIONS: From a clinical point of view, this paper contributes to support the increasing role of SSM, integrated with deep learning techniques, in diagnostics and therapy definition as quantitative and advanced visualization tools.

Bi-unicompartmental versus total knee arthroplasty: long term results.

The purpose is to demonstrate that Bi-Unicom- partmental knee arthroplasty (Bi-Uni) can produce equivalent long-term outcomes to total knee arthroplasty (TKA) in patients with bicompartmental knee osteoarthritis involving both the medial and lateral tibio-femoral compartments. A total of 37 patients with bicompartmental tibio- femoral osteoarthritis of the knee treated between January 1999 and March 2005 underwent either Bi-Uni or TKA. Nineteen patients who underwent simultaneous implantation of 2 unicompartmental knee arthroplasties (UKA) were matched and compared with 18 patients who had undergone a computer assisted TKA. At latest follow-up no statistically significant differences were seen between the 2 patient groups for KSS, Function scores and WOMAC Arthritis Index (pain score). The patients undergoing Bi-Uni did showed a statistically significant superior outcome for function (P < 0.05) and stiffness (P < 0.01) WOMAC indexes compared with the TKA group. The results of this study suggest that Bi-Uni is a valid alternative to address medial and lateral tibio- femoral osteoarthritis of the knee in selected cases. Bi-Uni replacement produces results equivalent TKA in patients with bicompartmental knee osteoarthritis involving both the medial and lateral tibio-femoral compartments and could represent a new frontier in modern knee reconstructive surgery. Level of Evidence: Level IV, retrospective comparative study.

2D/3D reconstruction of the distal femur using statistical shape models addressing personalized surgical instruments in knee arthroplasty: A feasibility analysis.

BACKGROUND: Personalized surgical instruments (PSI) have gained success in the domain of total knee replacement, demonstrating clinical outcomes similar or even superior to both traditional and navigated surgeries. The key requirement for prototyping PSI is the availability of the digital bony surface. In this paper, we aim at verifying whether the 2D/3D reconstruction of the distal femur, based on statistical shape models (SSM), grants sufficient accuracy, especially in the condylar regions, to support a PSI technique. METHODS: Computed tomographic knee datasets acquired on 100 patients with severe cartilage damage were retrospectively considered in this work. All the patients underwent total knee replacement using the PSI-based surgical technique. Eighty out of 100 reconstructed distal femur surfaces were used to build the statistical model. The remaining 20 surfaces were used for testing. The 2D/3D reconstruction process was based on digital reconstructed radiographies (DRRs) obtained with a simulated X-ray projection process. An iterative optimization procedure, based on an evolutionary algorithm, systematically morphed the statistical model to decrease the difference between the DRR, obtained by the original CT dataset, and the DRR obtained from the morphed surface. RESULTS: Over the 80 variations, the first ten modes were found sufficient to reconstruct the distal femur surface with accuracy. Using three DRR, the maximum Hausdorff and RMS distance errors were lower than 1.50 and 0.75 mm, respectively. As expected, the reconstruction quality improved by increasing the number of DRRs. Statistical difference (P < 0.001) was found in the 2 vs 3, 2 vs 4 and 2 vs 5 DRR, thus proving that adding just a single displaced projection to the two traditional sagittal and coronal X-ray images improved significantly the reconstruction quality. The effect of the PSI contact area errors on the distal cut direction featured a maximum median error lower than 2° and 0.5° on the sagittal and frontal plane, respectively. Statistical difference was found (P < 0.0001) in the reconstruction accuracy when comparing SSM built using pathologic with respect to non-pathologic shapes (cadavers), meaning that, to improve the patient-specific reconstruction, the morphologic anomalies, specific to the pathology, must be embedded into the SSM. CONCLUSIONS: We showed that the X-ray based reconstruction of the distal femur is reasonable also in presence of pathologic bony conditions, featuring accuracy results similar to earlier reports in the literature that reconstructed normal femurs. This finding discloses the chance of applying the proposed methodology to the reconstruction of bony surfaces used in the PSI surgical approach.

Patient-specific modeling of the trochlear morphologic anomalies by means of hyperbolic paraboloids.

Diagnostic and therapeutic purposes are issuing pressing demands to improve the evaluation of the dysplasia condition of the femoral trochlea. The traditional clinical assessment of the dysplasia, based on Dejour classification, recognized 4 increasing (A, B, C, D) levels of severity. It has been extensively questioned in the literature that this classification methodology can be defective suggesting that quantitative measures can ensure more reliable criteria for the dysplasia severity assessment. This study reports on a novel technique to model the trochlear surface (TS), digitally reconstructed by 3D volumetric imaging, using three hyperbolic paraboloids (HP), one to describe the global trochlear aspect, two to represent the local aspects of the medial and lateral compartments, respectively. Results on a cohort of 43 patients, affected by aspecific anterior knee pain, demonstrate the consistency of the estimated model parameters with the morphologic aspect of the TS. The obtained small fitting error (on average lower than 0.80 mm) demonstrated that the ventral aspect of the trochlear morphology can be modeled with high accuracy by HPs. We also showed that HP modeling provides a continuous representation of morphologic variations in shape parameter space while we found that similar morphologic anomalies of the trochlear aspect are actually attributed to different severity grades in the Dejour classification. This finding is in agreement with recent works in the literature reporting that morphometric parameters can only optimistically be used to discriminate between the Grade A and the remaining three grades. In conclusion, we can assert that the proposed methodology is a further step toward modeling of anatomical surfaces that can be used to quantify deviations to normality on a patient-specific basis.

Navigated "small implants" in knee reconstruction.

PURPOSE: At the beginning of this century, unprecedented interest in the concept of using less invasive approaches for the treatment of knee degenerative diseases was ignited. Initial interest in this approach was about navigated and non-navigated knee reconstruction using small implants and conventional total knee arthroplasty. METHODS: To this end, a review of the published literature relating to less invasive compartmental arthroplasty of the knee using computer-based alignment techniques and on soft tissue-dedicated small implants is presented. The authors present and compare their personal results using these techniques with those reported in the current literature. These involved the use of a shorter incision and an emphasis sparing. However, nowadays most surgeons look at compartmental knee resurfacing with the use of small implants as the new customized approach for younger and higher-demand patients. The aim of this paper is to stimulate further debate. RESULTS: Since the beginning of 2000, computer-assisted surgery has been applied to total knee arthroplasty (TKA) and later to compartmental knee arthroplasty. Recent studies in the literature have reported better implant survivorship for younger patients using navigation in TKA at longer-term follow-up. Only one published report was identified showing superior clinical outcomes at short-term follow-up using computer-assisted technology compared with conventional alignment techniques in small implant surgery. No studies were found in the literature that demonstrated similar clinical advantages with navigated small implants at long-term follow-up. Two published meta-analyses were identified reporting better implant and limb alignment and no increase in complications using a navigated unicompartmental knee arthroplasty. However, neither meta-analysis showed superior clinical outcomes or survivorship with the navigated techniques. CONCLUSION: In conclusion, we can assert that replacing just the damaged compartment and preserving the normal biomechanics will require not only new implant designs but also new technologies allowing the surgeon to make extremely precise adjustments to implant alignment and providing continuous feedback during surgery. LEVEL OF EVIDENCE: IV.