We performed positron emission tomography (PET) with . 18. fluorine-fluoro-2-deoxy-D-glucose (FDG) on 55 patients with tumours involving the musculoskeletal system in order to evaluate its role in operative planning. The standardised uptake value (SUV) of FDG was calculated and, to distinguish malignancies from benign lesions, the cases were divided into high (≥ 1.9) and low (< 1.9) SUV groups. The sensitivity of PET for correctly diagnosing malignancy was 100% with a specificity of 76.9% and an overall accuracy of 83.0%. The mean SUV for metastatic lesions was twice that for primary sarcomas (p < 0.0015). Our results suggest that the SUV may be useful in differentiating malignant tumours from benign lesions. However, some of the latter, such as schwannomas, had high SUVs so that biopsy or wide resection was selected as the first operation. Thus, some other quantitative analysis may be required for preoperative planning in cases of high-SUV neurogenic benign tumours. The reverse transcription-polymerase chain reaction revealed that the RNA message of a key enzyme in glucose metabolism, phosphohexose isomerase (PHI)/autocrine motility factor, was augmented in only high FDG-uptake lesions, suggesting that a high expression of the PHI message may be associated with accumulation of FDG in musculoskeletal tumours

Variations in pelvic anatomy are a major risk factor for misplaced percutaneous sacroiliac screws used to treat unstable posterior pelvic ring injuries. A better understanding of pelvic morphology improves preoperative planning and therefore minimises the risk of malpositioned screws, neurological or vascular injuries, failed fixation or malreduction. Hence a classification system which identifies the clinically important anatomical variations of the sacrum would improve communication among pelvic surgeons and inform treatment strategy. 300 Pelvic CT scans from skeletally mature trauma patients that did not have pre-existing posterior pelvic pathology were identified. Axial and coronal transosseous corridor widths at both S1 and S2 were recorded. Additionally, the S1 lateral mass angle were also calculated. Pelvises were classified based upon the sacroiliac joint (SIJ) height using the midpoint of the anterior cortex of L5 as a reference point. Four distinct types could be identified:. Type-A – SIJ height is above the midpoint of the anterior cortex of the L5 vertebra. Type-B – SIJ height is between the midpoint and the lowest point of the anterior cortex of the L5 vertebra. Type-C – SIJ height is below the lowest point of the anterior cortex of the L5 vertebra. Type-D – a subgroup for those with a lumbosacral transitional vertebra, in particular a sacralised L5. Differences in transosseous corridor widths and lateral mass angles between classification types were assessed using two-way ANOVAs. Type-B was the most common pelvic type followed by Type-A, Type-C, and Type-D. Significant differences in the axial and coronal corridors was observed for all pelvic types at each level. Lateral mass angles increased from Types-A to C, but were smaller in Type-D. This classification system offers a guide to surgeons navigating variable pelvic anatomy and understanding how it is associated with the differences in transosseous sacral corridors. It can assist surgeons’ preoperative planning of screw position, choice of fixation or the need for technological assistance

In the last years, 3d printing has progressively grown and it has reached a solid role in clinical practice. The main applications brought by 3d printing in orthopedic surgery are: preoperative planning, custom-made surgical guides, custom-made im- plants, surgical simulation, and bioprinting. The replica of the patient's anatomy, starting from the elaboration of medical volumetric images (CT, MRI, etc.), allows a progressive extremization of treatment personalization that could be tailored for every single patient. In complex cases, the generation of a 3d model of the patient's anatomy allows the surgeons to better understand the case — they can almost “touch the anatomy” —, to perform a more ac- curate preoperative planning and, in some cases, to perform device positioning before going to the surgical room (i.e. joint arthroplasty). 3d printing is also commonly used to produce surgical cutting guides, these guides are positioned intraoperatively on given landmarks to guide the surgeon to perform a specific surgical act (bone osteotomy, bone resection, implant position, etc.). In total knee arthroplasty, custom-made cutting guides have been developed to help the surgeon align the femoral and tibial components to the pre-arthritic condition with- out the use of the intramedullary femoral guide. 3d printed custom-made implants represent an emerging alternative to biological reconstructions especially after oncologic resection surgery or in case of complex arthroplasty revision surgery. Custom-made implants are designed to re- place the original shape and size of the patient's bone and they allow an extreme personalization of the treatment for every single patient. Patient-specific surgical simulation is a new frontier that promises great benefits for surgical training. a solid 3d model of the patient's anatomy can faithfully reproduce the surgical complexity of the patient and it allows to generate surgical simulators with increasing difficulty to adapt the difficulties of the course with the level of the trainees performing structured training paths: from the “simple” case to the “complex” case

Introduction. Intraoperative navigation systems for lumbar spine surgery allow to perform preoperative planning and visualize the real-time trajectory of pedicle screws. The aim of this study was to evaluate the deviation from preoperative planning and the correlations between screw deviation and accuracy. Method. Patients affected by degenerative spondylolisthesis who underwent posterior lumbar interbody fusion using intraoperative 3D navigation since April 2022 were included. Intraoperative cone-beam computed tomography (CBCT) was performed before screw planning and following implantation. The deviation from planning was calculated as linear, angular, and 3D discrepancies between planned and implanted screws. Accuracy and facet joint violation (FJV) were evaluated using Gertzbein-Robbins system (GRS) and Yson classification, respectively. Statistical analysis was performed using SPSS version28. One-way ANOVA followed by Bonferroni post-hoc tests were performed to evaluate the association between GRS, screw deviation and vertebral level. Statistical significance was set at p<0.05. Result. This study involved 34 patients, for a total of 154 pedicle screws. Mean age was 62.6±8.9 years. The mean two-dimensional screw tip deviation in mediolateral (ML), craniocaudal (CC), and anteroposterior (AP) was 2.6±2.45mm, 1.6±1.7mm, and 3.07±2.9mm, respectively. The mean screw tip 3D deviation was 5±3.3mm. The mean two-dimensional screw head deviation in ML, CC and AP was 1.83±1.8mm, 1.7±1.67mm and 3.6±3.1mm, respectively. The mean screw head 3D deviation was 4.94±3.2mm. 98% of screws were clinically acceptable (grade A+B), and grade 0 for FJV. Significant results were found between GRS and ML (p=0.005), AP (p=0.01) and 3D (p=0.003) tip deviations, and between GRS and AP and 3D head deviations (both p=0). Moreover, a significant correlation was found between GRS and vertebral level (p=0). Conclusion. Our results showed a reasonable rate of discrepancy between planned and positioned screws. However, accuracy was clinically acceptable in almost all cases. Therefore, pedicle screw fixation using intraoperative CBCT, 3D navigation and screw planning is safe and accurate

Preoperative planning for Total Hip Arthroplasty has been acknowledged as a vital step to facilitate a successful outcome. Templating ascertains the dimensions and positioning of the implants, minimizing both intraoperative and postoperative complications. The purpose of this study is to compare the accuracy of digital templating to acetate templating in the preoperative planning of Total Hip Arthroplasty. Preoperative planning was performed on 40 consecutive patients (mean age = 70.5 years), undergoing Total Hip Arthroplasty. Digital templating was performed by the Hip fellow 1, using Orthoview software (Jacksonville, FL, USA) and recorded the sizes of the cup and stem for each of the 40 patients. Subsequently, the same 40 patients were templated by Hip fellow 2, with X-rays done with a lead marker of known size by the side of the femur, using, acetate templating method. Templating results were compared to the actual sizes of the implants used, as noted in operative notes. Templating scores for the acetabular cup were 40% (16/40) with digital templating and 50% (20/40) with acetate templating. The templating scores for stem were 28% (11/40) with digital templating and 90% (36/40) with acetate templating. The differences between templating and actual implant sizes were plotted in Bland–Altman plot. Acetate templating proved to be statistically, significantly more accurate than digital templating (p value= 0.0083). Our results indicate that the traditional acetate method is solid and valid to use for preoperative planning. This method is accurate and offers a more affordable option for preoperative templating. Although the templated size is one, there is a tendency to increase cup size to use bigger heads, which is the recent National Joint Registries trend. We recommend that acetate templating should be used as the default option

Introduction and Objective. In recent years, along with the extending longevity of patients and the increase in their functional demands, the number of annually performed RSA and the incidence of complications are also increasing. When a complication occurs, the patient often needs multiple surgeries to restore the function of the upper limb. Revision implants are directly responsible for the critical reduction of the bone stock, especially in the shoulder. The purpose of this paper is to report the use of allograft bone to restore the bone stock of the glenoid in the treatment of an aseptic glenoid component loosening after a reverse shoulder arthroplasty (RSA). Materials and Methods. An 86-years-old man came to our attention for aseptic glenoid component loosening after RSA. Plain radiographs showed a complete dislocation of the glenoid component with 2 broken screws in the neck of glenoid. CT scans confirmed the severe reduction of the glenoid bone stock and critical bone resorption and were used for the preoperative planning. To our opinion, given the critical bone defect, the only viable option was revision surgery with restoration of bone stock. We planned to use a bone graft harvested from distal bone bank femur as component augmentation. During the revision procedure the baseplate with a long central peg was implanted “on table” on the allograft and an appropriate osteotomy was made to customize the allograft on the glenoid defect according to the CT-based preoperative planning. The Bio-component was implanted with stable screws fixation on residual scapula. We decided not to replace the humeral component since it was stable and showed no signs of mobilization. Results. The new bio-implant was stable, and the patient gained a complete functional recovery of the shoulder. The scheduled radiological assessments up to 12 months showed no signs of bone resorption or mobilization of the glenoid component. Conclusions. The use of bone allograft in revision surgery after a RSA is a versatile and effective technique to treat severe glenoid bone loss and to improve the global stability of the implant. Furthermore, it represents a viable alternative to autologous graft since it requires shorter operative times and reduces graft site complications. There are very few data available regarding the use of allografts and, although the first studies are encouraging, further investigation is needed to determine the biological capabilities of the transplant and its validity in complex revisions after RSA

The computational modelling and 3D technology are finding more and more applications in the medical field. Orthopedic surgery is one of the specialties that can benefit the most from this solution. Three case reports drawn from the experience of the authors’ Orthopedic Clinic are illustraded to highlight the benefits of applying this technology. Drawing on the extensive experience gained within the authors’ Operating Unit, three cases regarding different body segments have been selected to prove the importance of 3D technology in preoperative planning and during the surgery. A sternal transplant by allograft from a cryopreserved cadaver, the realization of a custom made implant of the glenoid component in a two-stage revision of a reverse shoulder arthroplasty, and a case of revision on a hip prosthesis with acetabular bone loss (Paprosky 3B) treated with custom system. In all cases the surgery was planned using 3D processing software and models of the affected bone segments, printed by 3D printer, and based on CT scans of the patients. The surgical implant was managed with dedicated instruments. The use of 3D technology can improve the results of orthopedic surgery in many ways: by optimizing the outcomes of the operation as it allows a preliminary study of the bone loss and an evalutation of feasibility of the surgery, it improves the precision of the positioning of the implant, especially in the context of severe deformity and bone loss, and it reduces the operating time; by improving surgeon training; by increasing patient involvement in decision making and informed consent. 3D technology, by offering targeted and customized solutions, is a valid tool to obtain the tailored care that every patient needs and deserves, also providing the surgeon with an important help in cases of great complexity

Despite past advances of implant technologies, complication rates of fixations remain high at challenging sites such as the proximal humerus [1]. These may not only be owed to the implant itself but also to dissatisfactory surgical execution of fracture reduction and implant positioning. Therefore, the aim of this study was to quantify the instrumentation accuracy of a highly standardised and guided procedure and its influence on the biomechanical outcome and predicted failure risk. Preoperative planning of osteotomies creating an unstable 3-part fracture and fixation with a locking plate was performed based on CT scans of eight pairs of low-density proximal humerus samples from elderly female donors (85.2±5.4 years). 3D-printed subject-specific guides were used to osteotomise and instrument the samples according to the pre-OP plan. Instrumentation accuracies in terms of screw lengths and orientations were evaluated by comparing post-OP CT scans with the pre-OP plan. The fixation constructs were biomechanically tested until cyclic cut-out failure [2]. Failure risks of the planned and the post-OP configurations were predicted using a validated sample-specific finite element (FE) simulation approach [2] and correlated with the experimental outcomes. Small deviations were found for the instrumented screw trajectories compared to the planned configuration in the proximal-distal (0.3±1.3º) and anterior-posterior directions (-1.7±1.8º), and for screw tip to joint distances (-0.3±1.1 mm). Significantly higher failure risk was predicted for the post-OP compared to the planned configurations (p<0.01) via FE. When incorporating the instrumentation inaccuracies, the biomechanical results could be predicted well with FE (R. 2. =0.70). Despite the high instrumentation accuracy achieved using sophisticated subject-specific 3D-printed guides, even minor deviations from the pre-OP plan significantly increased the FE-predicted risk of failure. This underlines the importance of intraoperative guiding technology [3] in tandem with careful pre-OP planning to assist surgeons to achieve optimal outcomes. Acknowledgements. This study was performed with the assistance of the AO Foundation via the AOTRAUMA Network

Introduction and Objective. After anterior cruciate ligament reconstruction one of the risk factors for graft (re-)rupture is an increased posterior tibial slope (PTS). The current treatment for PTS is a high tibial osteotomy (HTO). This is a free-hand method, with 1 degree of tibial slope correction considered to be equal to 1 or even 1.67 mm of the anterior wedge resection. Error rates in the frontal plane reported in literature vary from 1 – 8.6 degrees, and in the sagittal plane outcomes in a range of 2 – 8 degrees are reported when planned on PTSs of 3 – 5 degrees. Therefore, the free-hand method is considered to have limited accuracy. It is expected that HTO becomes more accurate with patient specific saw guides (PSGs), with an accuracy margin reported in literature of 2 degrees. This proof of concept porcine cadaver case study aimed to investigate whether the use of PSGs improves the accuracy of HTO to less than 2 degrees. Secondly, the reproducibility of tibial slope measurement was evaluated. Materials and Methods. Preoperative MRI images of porcine cadaver knees (n = 3) were used to create 3D anatomical bone models (Mimics, Materialise, Belgium). These 3D models were subsequently used to develop PSGs (3-Matic, Materialise, Belgium) to correct all tibias for 3 degrees PTS and 4 degrees varus. The PSG mediated HTOs were performed by an experienced orthopaedic surgeon, after which postoperative MRI images were obtained. 3D anatomical models of postoperative tibias were created, and tibial slopes were assessed on both pre- and postoperative tibias. The tibial slope was defined as the angle between the mechanical axis and 3D tibial reference plane in the frontal and sagittal plane. The accuracy of the PSG mediated HTO (median and range) was defined as the difference in all possible combinations of the preoperatively planned and postoperatively obtained tibial slopes. To ensure reproducibility, the pre- and postoperative tibial slopes were measured thrice by one observer. The intra-class correlation coefficients (ICCs) were subsequently calculated to assess the intra-rater reliability (SPSS, IBM Corp., Armonk, N.Y., USA). Results. An accuracy within 2 degrees was achieved in all three cases. The median and range in accuracy for each specimen were +0.46 (−0.57 – 1.45), +0.60 (−1.07 – 1.00), and +0.45 (−0.16 – 0.71) degrees in the frontal plane, and −0.45 (−1.97 – 1.22), −0.80 (−2.42 – 1.77), and 0.00 (−2.19 – 1.93) degrees in the sagittal plane. The pre- and postoperatively planned tibial slopes in the frontal and sagittal plane were measured with a good up to excellent reproducibility. The ICCs of the preoperative planned tibial slopes were 0.82 (95% CI, 0.11 – 1.0), and 0.77 (95% CI, 0.17 – 1.0) for the frontal and sagittal plane, respectively. Postoperative, the ICC for the frontal plane was 0.92 (95% CI, 0.43 – 1.0), and 0.67 (95% CI, −0.06 – 0.99) for the sagittal plane. Conclusions. This proof of concept porcine case study showed an accuracy for the PSG mediated HTO within 2 degrees for each specimen. Moreover, the tibial slopes were measured with a good up to excellent reproducibility. Therefore, the PSG mediated HTO seems to be accurate and might be better than the current used free-hand HTO method. These results offer perspective for implementation of PSG mediated HTO to correct PTS and metaphyseal varus

Summary Statement. In this study, excellent positioning of custom-made glenoid components was achieved using patient-specific guides. Achieving the preoperatively planned orientation of the component improved significantly and more screws were located inside the scapular bone compared to implantations without such guide. Introduction. Today's techniques for total or reverse shoulder arthroplasty are limited when dealing with severe glenoid defects. The available procedures, for instance the use of bone allografts in combination with available standard implants, are technically difficult and tend to give uncertain outcomes (Hill et al. 2001; Elhassan et al. 2008; Sears et al. 2012). A durable fixation between bone and implant with optimal fit and implant positioning needs to be achieved. Custom-made defect-filling glenoid components are a new treatment option for severe glenoid defects. Despite that the patient-specific implants are uniquely designed to fit the patient's bone, it can be difficult to achieve the preoperatively planned position of the component, resulting in less optimal screw fixation. We hypothesised that the use of a patient-specific guide would improve implant and screw positioning. The aim of this study was to evaluate the added value of a newly developed patient-specific guide for implant and screw positioning, by comparing glenoid implantations with and without such guide. Patients & Methods. Large glenoid defects, representative for the defects encountered in clinical practice, were created in ten cadaveric shoulders. A CT scan of each cadaver was taken to evaluate the defects and to generate three-dimensional models of the scapular bones. Based on these models, custom glenoid components were designed. Furthermore, a newly developed custom guide was designed for five randomly selected shoulders. New CT scans were taken after implantation to generate 3D models of the bone and the implanted component and screws. This enabled to compare the experimentally achieved and preoperatively planned reconstruction. The location and orientation of the glenoid component and screw positioning were determined and differences with the optimal preoperative planning were calculated. Results. An excellent component positioning (difference in location: 1.4±0, 7mm; difference in orientation: 2, 5±1, 2°) was achieved when using the guide compared to implantations without guidance (respectively 1, 7±0, 5mm; 5, 1±2, 3°). The guide improved component orientation significantly (P<0.1). After using the guide, all screws were positioned inside the scapular bone whereas 25% of the screws placed without guidance were positioned outside the scapular bone. Discussion/Conclusion. In this study, excellent positioning of custom-made glenoid components was achieved using patient-specific guides. Achieving the preoperatively planned orientation of the component improved significantly and more screws were located inside the scapular bone compared to implantations without such guide

Revision anterior cruciate ligament (ACL) reconstruction is a technically demanding procedure, reporting poorer outcomes compared to the primary procedure. Identification of the cause of primary failure and a thorough pre-operative evaluation is required to plan the most appropriate surgical approach. 3D printing technology has become increasingly commonplace in the surgical setting. In particular, patient-specific anatomical models can be used to aid pre-operative planning of complicated procedures. We have conducted a qualitative study to gauge the interest amongst orthopaedic knee surgeons in using a 3D-printed model to plan revision ACL reconstructions. A tibia and femur model was printed from one patient who is a candidate for the procedure. The binder jetting printing technique was performed, using Visijet PXL Core powder. 12 orthopaedic knee surgeons assessed the usefulness of the 3D-printed model compared to conventional CT images on a likert scale. 6 key steps of preoperative planning were assessed, including the size and location of the tunnel defects, the need for notchplasty, and whether a staged revision was required. We found that surgeons preferred the 3D-printed model to conventional CT images only, and 83% of them would use such a model for both pre-operative simulation, and as an intra-operative reference. However, there were some variation in the perceived usefulness of the model in several areas assessed. This may reflect differences in individual approach towards planning of the procedure. Our findings suggest that 3D-printed models could be a versatile pre-operative and intra-operative tool for complicated arthroscopic knee surgery. While 3D printing technology is becoming increasingly accessible and affordable, in-depth cost-effectiveness studies need to be conducted before it can be integrated into clinical. Further study would be needed to determine the clinical utility and economic cost-effectiveness of the 3D-printed model in revision ACL reconstruction

Locking plates have led to important changes in bone fracture management, allowing flexible biological fracture fixation based on the principle of an internal fixator. The technique of locking plate fixation differs fundamentally from conventional plating and has its indications and limitations. Most of the typical locking plate failure patterns are related to basic technical errors, such as under-sizing of the implant, too short working length, and imperfect application of locking screws. After analysis of the fracture morphology and intrinsic stability following fracture reduction, a meticulous preoperative planning is mandatory under consideration of the principles of the internal fixator technique to avoid technical errors and inaccuracies leading to early implant failure

Summary Statement. This is the first report of a new technique for unicompartmental to total knee arthroplasty revision surgery in which patient specific guides are formed based on preoperative CT imaging. This technique can help to make revision surgery less technically demanding. Introduction. Unicompartmental to total knee arthroplasty revision surgery can be a technically demanding procedure. Joint line restoration, rotation and augmentations can cause difficulties. This study describes a new technique in which single way fitting guides serve to position knee system cutting blocks. Methods. Preoperatively an image of the distal femur and proximal tibia are formed using CT-scanning. This image is used to create patient specific guides that fit in one single position on the contours of the bone and prosthesis in situ. These guides are fixed with pins and thereafter removed. The pins determine the position of the cutting blocks. Ten consecutive revisions were performed using this technique. Results. All guides fitted well. All femoral prostheses were properly inserted using this technique. One proximal tibia however did not have not enough bonestock so that conversion to intramedular referencing was performed. This was to be expected after the preoperative planning. Postoperative position of the prosthesis was good in all cases. Discussion. This new technique can help to make unicompartmental to total knee arthroplasty less demanding. Problems such as the need for augmentations can be predicted in the preoperative planning. Radiation issues due to CT scanning are limited. The instrumentation needs to be redesigned in order to make this technique work in cases with minimal bonestock present

In case of spine tumors, when en bloc vertebral column resection (VCR) is indicated and feasible, the segmental defect should be reconstructed in order to obtain an immediate stability and stimulate a solid fusion. The aim of this study is to share our experience on patients who underwent spinal tumor en bloc VCR and reconstruction consecutively. En bloc VCR and reconstruction was performed in 138 patients. Oncological and surgical staging were performed for all patients using Enneking and Weinstein-Boriani-Biagini systems accordingly. Following en bloc VCR of one or more vertebral bodies, a 360° reconstruction was made by applying posterior instrumentation and anterior implant insertion. Modular carbon fiber implants were applied in 111 patients, titanium mesh cage implants in 21 patients and titanium expandable cages in 3 patients; very recently in 3 cases we started to use custom made titanium implants. The latter were prepared according to preoperative planning of en bloc VCR based on CT-scan of the patient, using three dimensional printer. The use of modular carbon fiber implant has not leaded to any mechanical complications in the short and long term follow-up. In addition, due to radiolucent nature of this implant and less artifact production on CT and MRI, tumor relapse may be diagnosed and addressed earlier in compare with other implants, which has a paramount importance in these group of patients. We did not observe any implant failure using titanium cages. However, tumor relapse identification may be delayed due to metal artifacts on imaging modalities. Custom- made implants are economically more affordable and may be a good alternative choice for modular carbon fiber implants. The biocompatibility of the titanium make it a good choice for reconstruction of the defect when combined with bone graft allograft or autograft. Custom made cages theoretically can reproduce patients own biomechanics but should be studied with longer follow-up

Background. Achieving optimal prosthesis alignment during total knee arthroplasty (TKA) is essential. Imageless computer-assisted surgery (CAS) is developed to improve knee prosthesis alignment and with CAS it is possible to perform intraoperative alignment measurements. Lower limb alignment measurements are also performed for preoperative planning and postoperative evaluation. A new stereoradiography system, called EOS, can be used to perform these measurements in 3D and thus measurement errors due to malpositioning can be eliminated. Since both CAS and EOS are based on 3D modeling, measurements should theoretically correlate well. Therefore, objective was to compare intraoperative CAS-TKA measurements with pre- and postoperative EOS 3D measurements. Methods. In a prospective study 56 CAS-TKAs were performed and alignment measurements were recorded two times: before bone cuts were made and after implantation of the prosthesis. Pre- and postoperative coronal alignment measurements were performed using EOS 3D. CAS measurements were compared with EOS 3D reconstructions. Measured angles were: varus/valgus (VV), mechanical lateral distal-femoral (mLDFA) and medial proximal tibial angle (mMPTA). Results. Significantly different VV angles were measured pre- and postoperatively with CAS compared to EOS. For preoperative measurements, mLDFA did not differ significantly, but a significantly larger mMPTA in valgus was measured with CAS. Conclusions. EOS 3D measurements overestimate VV angle in lower limbs with substantial mechanical axis deviation. For lower limbs with minor mechanical axis deviation as well as for mMPTA measurements, CAS measures more valgus compared to EOS. Results of this study indicate that differences in alignment measurements between CAS measurements and pre- and postoperative EOS 3D are mainly due to the difference between weight bearing and non-weight bearing position and potential errors in validity and reliability of the CAS system. Surgeons should be aware of these measurement differences and the pitfalls of both measurement techniques. Level of evidence. IIb. Disclosures. The department of Orthopaedics, University of Groningen, University Medical Center Groningen receives research institutional support from InSpine (Schiedam, NL) and Stryker (Kalamazoo, Mich. USA). One of the authors (ALB) will be and has been paid as a consultant by Zimmer (Warsaw, IN, USA) for purposes of education and training in knee arthroplasty

In patients with developmental dysplasia of the hip (DDH) chronic joint dislocation induces remodeling of the soft tissue with contractures, muscle atrophy, especially of the hip abductors muscles, leading to severe motor dysfunction, pain and disability (1). The aim pf the present work is to explore if a correct positioning of the prosthetic implants through 3D skeletal modeling surgical planning technologies and an adequate customized rehabilitation can be beneficial for patients with DDH in improving functional performance. The project included two branches: a methodology branch of software development for the muscular efficiency calculation, which was inserted in the Hip-Op surgical planning system (2), developed at IOR to allow surgical planning for patients with complex hip joint impairment; and a clinical branch which involved the use of the developed software as part of a clinical multicentric randomized trial. 50 patients with DDH were randomized in two groups: a simple surgical planning group and an advanced surgical planning with muscular study group. The latter followed a customized rehabilitation program for the strenghtening of hip abductor muscles. All patients were assessed before surgery (T0) and at 3 (T1) and 6 months (T2) postoperatively using clinical outcome (WOMAC, HHS, ROM, MMT, SF12, 10mt WT) and instrumental measures (Dynamometric MT). Pre- and post-operative musculoskeletal parameters obtained by the software (i.e., leg length discrepancy, hip abductor muscle lengths and lever arms) using Hip-Op during the surgical planning were considered. One Way ANOVA for ROM measurement showed a significant improvement at T2 in patients included in experimental group, as well as WOMAC, HHS and SF12 score. The Dynamometric MT score showed significant differences between at T2 (p<0.009). Spearman's rank correlation coefficients showed a significant correlation between both pre- and post-operative abductors lever arm (mm) and hip abductor muscle strength at T2 (ρ = −0.55 pre-op and ρ = −0.51 post-op, p p<0.012 and p<0.02 respectively) and between the operated pre-postoperative leg length variation (mm) and the hip abductor muscle strength (ρ = −0.55, p p<0.013). Results so far obtained showed an improvement of functional outcomes in patients undergoing hip replacement surgery who followed therapeutic diagnostic pathway sincluding a preoperative planning including the assessment of the abductiors lever arm and a dedicated rehabilitation program for the strenghtening of abductios. Particularly interesting is the inverse relationship between the strength of the hip abductor muscles and the variation of the postoperative abductor lever arm

Aim of the study was the evaluation of the efficacy of the use of a new wearable AR video see-throught system based on Head Mounted Displays (HMDs) to guide the position of a working cannula into the vertebral body through a transpedicular approach without the use X-Ray images guidance. We describe a head mounted stereoscopic video see-through display that allows the augmentation of video frames acquired by two cameras with the rendering of patient specific 3D models obtained on the basis of pre-operative radiological volumetric images. The system does not employ any external tracker to detect movements of the user or of the patient. User's head movements and the consistent alignment of the virtual patient with the real one, are accomplished through machine vision methods applied on pairs of live images. Our system has been tested on an experimental setup that simulate the reaching of lumbar pedicle as in a vertebral augmentation procedure avoiding the employment of ionizing radiation. Aim of the study is to evaluate the ergonomics and the accurancy of the systems to guide the procedure. We performed 4 test sessions with a total of 32 kirschner wire implanted by a single operator wearing the HMD with the AR guide. The system accurancy was evaluated by a post-operative CT scan. The most ergonomic AR visualization comprise the use of a pair of virtual viewfinders (one at the level of the skin entry point and one at the level of the trocar's bottom) aligned according to the planned direction of the trocar insertion. With such AR guide the surgeon must align the tip of the needle to the center of the first viewfinder placed on the patient's skin. indeed the viewfinder barycenter provides a 2 degrees of freedom (DoFs) positioning guide corresponding to the point of insertion preoperatively planned over the external surface of the model. The second viewfinder is used by the surgeon to rotate and align the trocar according to the planned direction of insertion (2 rotational DOFs). After the first test series a clamping arm has been introduced to maintain the reached trocar's trajectory. The post-operative CT scan was registered to the preoperative one and the trajectories obtained with the AR guide were compared to the planned one. The overal results obtained in the 4 test session show a medium error of 1.18+/−0.16 mm. In the last year there was a growing interest to the use of Augmented Reality systems in which the real scene watched by the surgeon is merged with virtual informations extracted from the patient's medical dataset (medical data, patient anatomy, preoperative plannig). Wearable Augmented Reality (WAR) with the use of HDMs allows the surgeon to have a “natural point of view” of the surgical field and of the patient's anatomy avoiding the problems related to eye-hand coordination. Results of the in vitro tests are encouraging in terms of precision, system usability and ergonomics proving our system to be worthy of more extensive tests

Instability following total hip arthroplasty (THA) is an unfortunately frequent and serious problem that requires thorough evaluation and preoperative planning before surgical intervention. Prevention through optimal index surgery is of great importance, as the management of an unstable THA is challenging even for an experienced joints surgeon. However, even after well-planned surgery, a significant incidence of recurrent instability still exists. Moreover leg-length discrepancy (LLD) after THA can pose a substantial problem for the orthopaedic surgeon. Such discrepancy has been associated with complications including nerve palsy, low back pain, and abnormal gait. Consequently we may use a big femoral head or increase femoral offset (FO) in unstable THA for avoiding LLD. However we do not know the relationship between FO and STT. The objective of this study is to assess hip instability of three different FOs in same patient undergoing THA during an operation. We performed 70 patients who had undergone unilateral THA using CT based navigation system at a single institution for advanced osteoarthoritis from May 2013 to May 2014. We used postero-lateral approach in all patients. After cup and stem implantation, we assessed soft tissue tensioning in THA during operation. Trial necks were categorized into one of three groups: standard femoral offset (sFO), high femoral offset (hFO, +4mm compared to sFO) and extensive high femoral offset (ehFO, +8 mm compared to sFO). We measured distance of lift-off about each of three femoral necks using CT based navigation system and a force gauge with hip flexed at 0 degrees and 30 degrees under a traction of lower extremity. Traction force was 40% of body weight. Forty patients had leg length restored to within +/− 3mm of the contralateral side by post-operative CT analysis. We examined these patients. Traction force was 214±41.1Nm. The distances of lift-off were 8.8±4.5mm (sFO), 7.4±4.1mm (eFO), 5.1±3.9mm (ehFO) with 0 degrees hip flexion and neutral abduction(Abd) / adduction(Add) and neutral internal rotation(IR)/ external rotation(ER). The distance of lift-off were 11.5±5.9mm (sFO),10.5±5.5mm (eFO),9.1±5.9mm (ehFO) with 30 degrees hip flexion and neutral Abd / Add and neutral IR/ER. Significant difference was observed between 0 degrees hip flexion and 30 degrees hip flexion on each FO (p<0.05). On changing the distance of lift-off, hFO to ehFO (2.2±1.6mm)was more stable than sFO to hFO (1.4±1.7mm)with 0degrees hip flexion.(p<0.05). On the other hands, hFO to ehFO (1.4±1.6mm) was more stable than sFO to hFO (1.0±1.3mm) with 30 degrees hip flexion. However, we did not find significant difference (p=0.18). Hip instability was found at 30 degrees hip flexion more than at 0 degrees hip flexion. We found that changing ehFO to sFO can lead to more stability improvement of soft tissue tensioning than sFO to eFO, especially at 0 degrees hip flexion. Whereas In a few cases, the distance of lift-off did not change with increasing femoral offset by 4mm. When you need more stability in THA without LLD, We recommend increasing FO by 8mm

Soft tissue balancing is critical to successful knee arthroplasty. Pre-operative planning ensures that the surgeon is prepared for any eventuality. We report a large femoral exostosis resulting in gross instability, requiring revision to a constrained implant. An 81 year old female presented with osteoarthritis of the left knee. Xray showed a medial bony mass. CT noted a large bony exostosis arising from the posteromedial femoral condyle. Review showed the exostosis was not related to the medial collateral ligament (MCL). At surgery, the exostosis was noted to be tenting the MCL – excision resulted in complete flaccidity. A trial of the Biomet AGC prosthesis revealed gross medial instability. The decision was taken to convert to a DePuy Sigma TC3 system. Whilst removing TC3 trial components, a lateral condyle fracture occurred. This was fixed with a 1/3 tubular plate and interfragmentary screw. The TC3 system and an AGC patellar button were found to be congruent. A small lateral release was performed, the deep MCL was replaced with tagging sutures through the MCL and the pes anserinus. At 9 weeks post operatively, the patient was pain free and mobilising independently. The knee was stable, with range of movement from 0 to 110 degrees. To our knowledge, this is the first report of such a complication in the literature. It highlights that despite optimal preoperative planning, the surgeon must be prepared to adapt to the situation at hand. It also highlights the importance of having ‘bail out’ options available on shelf when performing routine surgery

Digital radiographs are routinely used for preoperative planning, both in trauma and elective patients; particularly in preoperative templating for total hip replacement. Traditional wisdom holds that radiographs are oversized, though the degree to which this occurs is unclear. Although digital templating systems offer the use of calibration markers, this option is not always availed. We aimed to ascertain the typical magnification in departmental xrays of the hip, both to determine the typical degree of magnification as well as ascertain its consistency. All patients undergoing dynamic hip screw fixation (DHS) in our unit over the past 12 months were identified. Using the PACS system, subsequent xrays of the patient with the implant in situ were identified; both anteroposterior abdominal and pelvic films were used. The width of a standard DHS screw (12.5 mm) was compared with the width measured on the xrays to determine a magnification factor. 164 patients were identified, of these 39 had undergone DHS fixation with subsequent xrays. 3 films were focused on the abdomen but provided good coverage of the hip also. 2 xrays were excluded – both due to limited quality. The average magnification was 26.4% (range 15.5%–42%). There was limited consistency between images. Radiographs are a core investigation in the assessment of the orthopaedic patient. The advent of picture archiving and communications systems (PACS) has allowed the enterprising surgeon to pre-emptively plan their surgical technique and implant use. However, the utility of non-calibrated images in planning implant size is limited by variation in magnification. Surgeons should be cautious in using such images to guide their implant usage