Introduction. PSI technology have proved helpful in difficult primary Total Knee Replacement. However applying it to revision was impossible due to multiple factor. To Start with the landmark We usually destroy it. There is an extensive damage at the bone at the epiphysis, the implant prevent an accurate visualization and debridement usually change the surface of the bone as well which make applying the psi dyed impossible, we are proposing a new way of using psi in revision where we don't depend on the all masses adjusted in primary. However we depend on the metaphysical area of the bone. Material & method. We have reviewed 56 MRI & CT scans for cases posted for revision and showed clearly that in spite of the extensive bony destruction and metal presence the MRI / CT scan we were able to visualize well the metaphysical area in the intramedullary canal in both tibial and femoral we have established a special external guide that depends on the outside surface of the metaphysis of the femur. We have tried this model on six plastic bone and showed that this external guide can give the accurate details that the surgeon is looking for in a revision surgery. Result & discussion. We have performed revision surgery on six bony model utilizing the new external guide that depend on the metaphysical bone mark. In all cases we were able to have a good lock for the external guide enabling us to precisely indicate the flexion extension joint line as well as the femoral rotation accurately. The guide established to us were the trial component should be seated and the surgery after that was quite easy filling the gap with necessary block and augment based on the accurate joint line. Furthermore, performing the surgery this way enabled us to offreem in order to correct the deformity that may result from the fixed angle of the stem in both femoral and tibial component. Our suggested way of performing the revision surgery is to use the metaphysical guide to indicate the entry point for reaming. this will allow the surgeon to offream after which the external guide also block the phantom or trial component indicating both flexion and extension joint line and rotation. After that the surgeon build up to the joint line. Conclusion. Depending on a new landmark outside metaphysical and suggesting a new type of guide will make psi possible regardless of the amount of bony destruction in the epiphyseal area. Furthermore performing the surgery this way will decrease the error that is based on the judgment of the surgeon for his joint line and rotation and point of entry. We believe that further work and development is needed to make it durable for commercial

Introduction. PSI technology have proved helpful in difficult primary Total Knee Replacement. However applying it to revision was impossible due to multiple factor. To Start with the landmark We usually destroy it. There is an extensive damage at the bone at the epiphysis, the implant prevent an accurate visualization and debridement usually change the surface of the bone as well which make applying the psi dyed impossible, we are proposing a new way of using psi in revision where we don't depend on the all masses adjusted in primary. However we depend on the metaphysical area of the bone. Material & method. We have reviewed 56 MRI &CT scans for cases posted for revision and showed clearly that in spite of the extensive bony destruction and metal presence the MRI / CT scan we were able to visualize well the metaphysical area in the intramedullary canal in both tibial and femoral · we have established a special external guide that depends on the outside surface of the metaphysis of the femur. We have tried this model on six plastic bone and showed that this external guide can give the accurate details that the surgeon is looking for in a revision surgery. Result & discussion. We have performed revision surgery on six bony model utilizing the new external guide that depend on the metaphysical bone mark. In all cases we were able to have a good lock for the external guide enabling us to precisely indicate the flexion extension joint line as well as the femoral rotation accurately. The guide established to us were the trial component should be seated and the surgery after that was quite easy filling the gap with necessary block and augment based on the accurate joint line. Furthermore, performing the surgery this way enabled us to offreem in order to correct the deformity that may result from the fixed angle of the stem in both femoral and tibial component. Our suggested way of performing the revision surgery is to use the metaphysical guide to indicate the entry point for reaming · this will allow the surgeon to offream after which the external guide also block the phantom or trial component indicating both flexion and extension joint line and rotation. After that the surgeon build up to the joint line. Conclusion. Depending on a new landmark outside metaphysical and suggesting a new type of guide will make psi possible regardless of the amount of bony destruction in the epiphyseal area. Furthermore performing the surgery this way will decrease the error that is based on the judgment of the surgeon for his joint line and rotation and point of entry. We believe that further work and development is needed to make it durable for commercial

Introduction. Patient specific instrumentation (PSI) generates customized guides from an MRI- or CT-based preoperative plan for use in total knee arthroplasty (TKA). PSI software executes the preoperative planning process. Several manufacturers have developed proprietary PSI software for preoperative planning. It is possible that each proprietary software has a unique preoperative planning process, which may lead to variation in preoperative plans among manufactures and thus variation in the overall PSI technology. The purpose of this study was to determine whether different PSI software generate similar preoperative plans when applied to a single implant system and given identical MR images. Methods. In this prospective comparative study, we evaluated PSI preoperative plans generated by Materialise software and Zimmer Patient Specific Instruments software for 37 consecutive knees. All plans utilized the Zimmer Persona™ CR implant system and were approved by a single experienced surgeon blinded to the other software-generated preoperative plan. For each knee, the MRI reconstructions for both software programs were evaluated to qualitatively determine differences in bony landmark identification. The software-generated preoperative plans were assessed to determine differences in preoperative alignment, component sizes, and resection depth. PSI planned bone resection was compared to actual bone resection to assess the accuracy of intraoperative execution. Results. Materialise and Zimmer PSI software displayed differences in identification of bony landmarks in the femur and tibia. Zimmer software determined preoperative alignment to be 0.5° more varus (p=0.008) compared to Materialise software. Discordance in femoral component size prediction occurred in 37.8% of cases (p<0.001) with 11 cases differing by one size and 3 cases differing by two sizes. Tibial component size prediction was 32.4% discordant (p<0.001) with 12 cases differing by 1 size. In cases in which both software planned identical femoral component sizes, Zimmer software planned significantly more bone resection compared to Materialise in the medial posterior femur (1.5 mm, p<0.001) and lateral posterior femur (1.4 mm, p<0.001). Discussion. The present study suggests that there is notable variation in the PSI preoperative planning process of generating a preoperative plan from MR images. We found clinically significant differences with regard to bony landmark identification, component size selection, and predicted bone resection in the posterior femur between preoperative plans generated by two PSI software programs using identical MR images and a single implant system. Surgeons should be prepared to intraoperatively deviate from PSI selected size by 1 size. They should be aware that the inherent magnitude of error for PSI bone resection with regard to both planning and execution is within 2–3 mm. Users of PSI should acknowledge the variation in the preoperative planning process when using PSI software from different manufacturers. Manufacturers should continue to improve three-dimensional MRI reconstruction, bony landmark identification, preoperative alignment assessment, component size selection, and algorithms for bone resection in order to improve PSI preoperative planning process

Introduction. Patient specific instruments (PSI) and computer-assisted surgery (CAS) are innovative technologies that offer the potential to improve the accuracy and reproducibility with which a total knee arthroplasty (TKA) is performed. It has not been established whether clinical, functional, or radiographic outcomes between PSI, CAS, and manual TKA differ in the hands of an experienced TKA surgeon. The purpose of this study was to evaluate clinical, functional and radiographic outcomes between TKA performed with PSI, CAS, and manual instruments at short-term follow-up. Our hypothesis was that at early follow-up, we would be unable to elucidate any significant differences between the groups using the most commonly utilized outcomes measures. Methods. 40 PSI, 38 CAS, and 40 manual TKA were performed by a single surgeon. The groups were similar in regards to age, sex, and preoperative diagnosis. The Knee Society Scoring System was used to evaluate patient clinical and functional outcome scores preoperatively and at 1 and 6 months postoperatively. Long-standing AP radiographs were obtained pre and postoperative to evaluate mechanical axis alignment. Results. PSI, CAS, and manual TKA produced similar interval improvements in clinical and functional outcomes at both 1 and 6-months postoperative. Knee Society Knee scores were on average 88.5, 72.5, and 69.3 for PSI, CAS, and manual TKA at 1 month and 99.4, 83.4, and 84.6 at 6 months postoperative. Knee Society Function scores were on average 65.9, 49.3, and 48.4 for PSI, CAS, and manual TKA at 1 month and 86.3, 66.2, and 61.2 at 6 months postoperative. Although PSI tended to have higher absolute Knee and Function scores at 1 and 6 months postoperative, the interval change from preoperative to postoperative between each group was similar. Postoperative mechanical axis alignment was not significantly different between PSI, CAS, and manual TKA (1.0â�°, 2.0â�°, and −0.2â�°, respectively). Discussion. This study suggests that in the hands of an experienced arthroplasty surgeon, PSI, CAS and manual TKA produce similar interval improvements in clinical, functional, and radiographic outcomes at short-term follow-up. These results may reflect the ability of an arthroplasty-trained academic surgeon to perform a TKA accurately with multiple technologies. These findings may also represent the lack of sensitivity and inability of commonly utilized evaluation tools, like plain radiographs and the Knee Society Scoring System, to adequately differentiate small differences in outcomes and limb alignment, if differences do indeed exist. Long-term follow-up will help establish whether these TKA technologies continue to demonstrate equivalent clinical and functional interval improvements

Navigation-assisted surgery has been reported to enhance resection accuracy in bone sarcoma surgery. Patient-specific instruments (PSIs) have been proposed as a simpler alternative with fewer setup facilities. We investigated the use of 3D surgical planning and PSI in realising computer planning of complex resections in bone sarcoma patients with regards to surgical accuracy, problems, and early clinical results. We retrospectively studied twelve patients with bone sarcoma treated surgically by PSIs with 3D planning. The procedure was planned using engineering software. The resection accuracy was accessed by comparing CT images of tumour specimens with the planned in seven patients. Mean age was 30.9 (9 – 64). Mean follow-up was 3.1 year (0.5 – 5.3). 31 planes of bone resections were successfully performed using the technique and were considered accurate. The mean time required for placing PSIs was 5.7 minutes (1 – 10) and performing bone osteotomies with the assistance of PSIs was 4.7 minutes (2 – 7). The mean maximum deviation error was 1.7mm (0.5 – 4.4). One PSI was broken during bone resection, and one patient needed re-resection using the same PSI. One pelvic patient died of local recurrence and lung metastases six months postoperatively. One patient developed a soft tissue local recurrence and lung metastasis at 20 months after surgery. The mean MSTS functional score was 27.9 (21 – 30). There were no complications related to 3D planning and PSIs. In selected patients, 3D surgical planning and PSIs replicate complex bone resections and reconstructions in bone sarcoma surgery. Comparative studies with conventional or navigation- assisted resections are required

Proton beam radiation (PT) is getting an increasing role in the treatment strategy of complex tumour cases and especially in children. AT PSI, over 100 children were treated so far. In this analysis we present the evaluation of 62 children treated until the end of 2007 for sarcomatous tumours. Twenty-nine girls and 33 boys were included. Median age at time of diagnosis was 8.1 yrs. (range, 0.1–19.0). The histopathologies were embryonal RMS (n = 24), Chordoma (n = 10), Ewing sarcoma (n = 6), Chondrosarcoma (n = 5), unclassified/undifferentiated RMS (n = 5), Osteosarcoma (n = 4) and miscellaneous. All, but 2 patients had localized disease at time of diagnosis. Tumour site was head and neck in 43 patients, and spine or pelvis in 19 patients. In 50 out of the 62 patients, PT was performed after biopsy or incomplete resection. Forty-four patients had received chemotherapy before or during PT. Median dose of irradiation was 54 Gy (range, 45 – 74 Gy) with 1.8–2.0 Gy fraction dose 4 – 5 times weekly. Median FU time was 20 months (1.4 – 101). 54 children were still alive at the time of analysis. Twelve patients failed, of them 9 locally and 3 patients at distant site. Acute toxicity was exceeding grade 2 (RTOG/ EORTC) mainly for bone marrow in children with parallel chemotherapy (n = 23). In 6 children skin/mucosal reaction was exceeding grade 2. Late effects were not exceeding grade 2 in the majority of children. One serious adverse event was observed in a very young girl with a parameningeal sarcoma experiencing a lethal ischemia in the pontine area after surgery, chemotherapy and PT. In the vast majority of patients proton therapy was well tolerated. Local control and survival rates are promising. Longer follow-up time and a greater cohort will help to provide more reliable data

Introduction

Restoration of the femoral head centre during THR should theoretically improve muscle function and soft tissue tension. The aim of this study was to assess whether 3D planning and an accurately controlled neck osteotomy could help recreate hip anatomy.

Aims. It is unknown whether kinematic alignment (KA) objectively improves knee balance in total knee arthroplasty (TKA), despite this being the biomechanical rationale for its use. This study aimed to determine whether restoring the constitutional alignment using a restrictive KA protocol resulted in better quantitative knee balance than mechanical alignment (MA). Methods. We conducted a randomized superiority trial comparing patients undergoing TKA assigned to KA within a restrictive safe zone or MA. Optimal knee balance was defined as an intercompartmental pressure difference (ICPD) of 15 psi or less using a pressure sensor. The primary endpoint was the mean intraoperative ICPD at 10° of flexion prior to knee balancing. Secondary outcomes included balance at 45° and 90°, requirements for balancing procedures, and presence of tibiofemoral lift-off. Results. A total of 63 patients (70 knees) were randomized to KA and 62 patients (68 knees) to MA. Mean ICPD at 10° flexion in the KA group was 11.7 psi (SD 13.1) compared with 32.0 psi in the MA group (SD 28.9), with a mean difference in ICPD between KA and MA of 20.3 psi (p < 0.001). Mean ICPD in the KA group was significantly lower than in the MA group at 45° and 90°, respectively (25.2 psi MA vs 14.8 psi KA, p = 0.004; 19.1 psi MA vs 11.7 psi KA, p < 0.002, respectively). Overall, participants in the KA group were more likely to achieve optimal knee balance (80% vs 35%; p < 0.001). Bone recuts to achieve knee balance were more likely to be required in the MA group (49% vs 9%; p < 0.001). More participants in the MA group had tibiofemoral lift-off (43% vs 13%; p < 0.001). Conclusion. This study provides persuasive evidence that restoring the constitutional alignment with KA in TKA results in a statistically significant improvement in quantitative knee balance, and further supports this technique as a viable alternative to MA. Cite this article: Bone Joint J. 2020;102-B(1):117–124

Aim. Pin site infection (PSI) is a common complication of external fixators. PSI usually presents as a superficial infection which is treated conservatively. This study investigated those rare cases of PSI requiring surgery due to persistent osteomyelitis (OM), after pin removal. Method. In this retrospective cohort study we identified patients who required surgery for an OM after PSI (Checketts-Otterburn Classification Grade 6) between 2011 and 2021. We investigated patient demographics, aetiology of the OM, pathogen and histology, treatment strategies and complications. Infection was confirmed using the 2018 FRI Consensus Definition. Successful outcome was defined as an infection-free interval of at least 24 months following surgery, which was defined as minimum follow-up. Results. Twenty-seven patients were treated due to a pin site infection with an osteomyelitis (22 tibias, 2 humeri, 2 calcanei, 1 radius). 85% identified as male and the median age was 53.9 years. Eighteen infections followed external fixation of fractures, with 4 cases after Ilizarov deformity correction, 2 cases followed ankle fusion and 3 after traction pin insertion. Fifteen patients were classified as BACH Uncomplicated and 12 were BACH Complex. The median follow-up was 3.99 years (2.00–8.05 years). Staphylococci were the most common pathogens (16 MSSA, 2 MRSA, 2 CNS). Polymicrobial infections were present in 5 cases (19%). All surgery was performed in a single stage following the same protocol at one institution. This included deep sampling, debridement, implantation of local antibiotics, culture-specific systemic antibiotics and soft tissue closure. Seven patients required flap coverage (6 local, 1 free flap), which was performed in the same operation. 25 (93%) patients had a successful outcome after one surgery. Two had recurrence of infection which was successfully treated by repeat of the protocol. One patient suffered a fracture through the operated site after a fall. This healed without infection recurrence. Wound leakage after local antibiotic treatment was seen in 3/27 (11%) of cases. All resolved without treatment. After a minimum of 2 years follow up, all patients were infection free at the site of the former osteomyelitis. Conclusions. OM after PSI is uncommon but has major implications for the patient as 7 out of 27 patients needed flap coverage. This reinforces the need for careful pin placement and pin site care to prevent deep infection. These infections require appropriate surgery, not just curettage. All patients in our cohort were infection-free after a minimum follow-up of 2 years suggesting that this protocol is effective

Total knee arthroplasty is a successful procedure that reduces knee pain and improves function in most patients with knee osteoarthritis. Patient dissatisfaction however remains high, and along with implant longevity, may be affected by component positioning. Surgery in obese patients is more technically challenging with difficulty identifying appropriate landmarks for alignment and more difficult exposure of the joint. Patient specific instrumentation (PSI) has been introduced with the goal to increase accuracy of component positioning by custom fitting cutting guides to the patient using advanced imaging. A strong criticism of this new technology however, is the cost associated. The purpose of this study was to determine, using a prospective, randomized-controlled trial, the cost-effectiveness of PSI compared to standard instrumentation for total knee arthroplasty in an obese patient population. Patients with a body mass index greater than 30 with osteoarthritis and undergoing a primary total knee arthroplasty were included in this study. We randomized patients to have their procedure with either standard instrumentation (SOC) or PSI. At 12-weeks post-surgery patients completed a self-reported cost questionnaire and the Western Ontario and McMaster Osteoarthritis Index (WOMAC). We performed a cost-effectiveness analyses from a public health payer and societal perspective. As we do not know the true cost of the PSI instrumentation, we estimated a value of $100 for our base case analysis and used one-way sensitivity analyses to determine the effect of different values (ranging from $0 to $500) would have on our conclusions. A total of 173 patients were enrolled in the study with 86 patients randomized to the PSI group and 87 to the SOC group. We found the PSI group to be both less effective and more costly than SOC when using a public payer perspective, regardless of the cost of the PSI. From a societal perspective, PSI was both less costly, but also less effective, regardless of the cost of the PSI. The mean difference in effect between the two groups was −1.61 (95% CI −3.48, 026, p=0.091). The incremental cost-effectiveness ratio was $485.71 per point increase in the WOMAC, or $7285.58 per clinically meaningful difference (15 points) in the WOMAC. Overall, our results suggest that PSI is not cost-effective compared to standard of care from a public payer perspective. From a societal perspective, there is some question as to whether the decreased effect found with the PSI group is worth the reduced cost. The main driver of the cost difference appears to be time off of volunteer work, which will need to be investigated further. In future, we will continue to follow these patients out to one year to collect cost and effectiveness data to investigate whether these results remain past 12 weeks post-surgery

When removing femoral cement in revision hip surgery, creating an anterior femoral cortical window is an attractive alternative to extended trochanteric osteotomy. We describe our experience and evolution of this technique, the clinical and radiological results, and functional outcomes. Between 2006 and 2021 we used this technique in 22 consecutive cases at Whanganui Hospital, New Zealand. The average age at surgery was 74 years (Range 44 to 89 years). 16 cases were for aseptic loosening: six cases for infection. The technique has evolved to be more precise and since 2019 the combination of CT imaging and 3-D printing technology has allowed patient-specific (PSI) jigs to be created (6 cases). This technique now facilitates cement removal by potentiating exposure through an optimally sized anterior femoral window. Bone incorporation of the cortical window and functional outcomes were assessed in 22 cases, using computer tomography and Oxford scores respectively at six months post revision surgery. Of the septic cases, five went onto successful stage two procedures, the other to a Girdlestone procedure. On average, 80% bony incorporation of the cortical window occurred (range 40 −100%). The average Oxford hip score was 37 (range 22 – 48). Functional outcome (Oxford Hip) scores were available in 11 cases (9 pre-PSI jig and 2 using PSI jig). There were two cases with femoral component subsidence (1 using the PSI jig). This case series has shown the effectiveness of removing a distal femoral cement mantle using an anterior femoral cortical window, now optimized by using a patient specific jig with subsequent reliable bony integration, and functional outcomes comparable with the mean score for revision hip procedures reported in the New Zealand Joint Registry

Introduction. The degree of glenoid bone loss associated with primary glenohumeral osteoarthritis can influence the type of glenoid implant selected and its placement in total shoulder arthroplasty (TSA). The literature has demonstrated inaccurate glenoid component placement when using standard instruments and two-dimensional (2D) imaging without templating, particularly as the degree of glenoid deformity or bone loss worsens. Published results have demonstrated improved accuracy of implant placement when using three-dimensional (3D) computed tomography (CT) imaging with implant templating and patient specific instrumentation (PSI). Accurate placement of the glenoid component in TSA is expected to decrease component malposition and better correct pathologic deformity in order to decrease the risk of component loosening and failure over time. Different types of PSI have been described. Some PSI use 3D printed single use disposable instrumentation, while others use adjustable and reusable-patient specific instrumentation (R-PSI). However, no studies have directly compared the accuracy of different types of PSI in shoulder arthroplasty. We combined our clinical experience and compare the accuracy of glenoid implant placement with five different types of instrumentation when using 3D CT imaging, preoperative planning and implant templating in a series of 173 patients undergoing primary TSA. Our hypothesis was that all PSI technologies would demonstrate equivalent accuracy of implant placement and that PSI would show the most benefit with more severe glenoid deformity. Discussion and Conclusions. We demonstrated no consistent differences in accuracy of 3D CT preoperative planning and templating with any type of PSI used. In Groups 1 and 2, standard instrumentation was used in a patient specific manner defined by the software and in Groups 3, 4, and 5 a patient specific instrument was used. In all groups, the two surgeons were very experienced with use of the 3D CT preoperative planning and templating software and all of the instrumentation prior to starting this study, as well as very experienced with shoulder arthroplasty. This is a strength of the study when defining the efficacy of the technology, but limits the generalizability of the findings when considering the effectiveness of the technology with surgeons that may not have as much experience with shoulder arthroplasty and/or the PSI technology. Conversely, it could be postulated that greater improvements in accuracy may be seen with the studied PSI technology, when compared to no 3D planning or PSI, with less experienced surgeons. There could also be differences between the PSI technologies when used by less experienced surgeons, either across all cases or based upon the severity of pathology. When the surgeon is part of the method, the effectiveness of the technology is equally dependent upon the surgeon using the technology. A broader study using different surgeons is required to test the effectiveness of this technology. Comparing the results of this study with published results in the literature, 3D CT imaging and implant templating with use of PSI results in more accurate placement of the glenoid implant when compared to 2D CT imaging without templating and use of standard instrumentation. In previous studies, this was most evident in patients with more severe bone deformity. We believe that 3D CT planning and templating provides the most value in defining the glenoid pathology, as well as in the selection of the optimal implant and its placement. However, it should be the judgment of the surgeon, based upon their experience, to select the instrumentation to best achieve the desired result

Introduction. The effectiveness of patient specific instrumentation (PSI) to perform total knee arthroplasty (TKA) remains controversial. Multiple studies have been published that reveal conflicting results on the effectiveness of PSI, but no study has analyzed the contact kinematics within knee joints replaced with the use of PSI. Since a departure from normal kinematics can lead to eccentric loading, premature wear, and component loosening, studying the kinematics in patients who have undergone TKA with PSI can provide valuable insight on the ability of PSI to improve functionality and increase longevity. The goal of the present study was to compare femoral and tibial component migration (predictive of long-term loosening and revision) and contact kinematics following TKA using conventional instruments (CI) and PSI based surgical techniques. Methods. The study was designed as a prospective, randomized controlled trial of 50 patients, with 25 patients each in the PSI and CI groups, powered for radiostereometric analysis (RSA). Patients in the PSI group received an MRI and standing 3-foot x-rays to construct patient-specific cut-through surgical guides for the femur and tibia with a mechanical limb alignment. All patients received the same posterior-stabilized implant with marker beads inserted in the bone around the implants to enable RSA imaging. Patients underwent supine RSA exams at multiple time points (two and six weeks, three and six months, and one and two years). At 2 years post-op, a series of RSA radiographs were acquired at different knee flexion angles, ranging in 20° increments from 0° to 120°, to measure the tibiofemoral contact kinematics. Migrations of the femoral and tibial components were calculated using model-based RSA software. Kinematics were measured for each condyle for magnitude of excursion, contact location, and stability. Results. There were no differences (p > 0.05) between the PSI and CI groups for demographics or pre- and post-operative patient reported outcome scores. Three patients in the PSI group and seven patients in the CI group (p = 0.28) had a post-operative limb alignment outside of the neutral target (>3° varus or valgus). There was no difference in the change of tibial slope from pre- to post-operation between groups (p = 0.49). There were no differences (p > 0.05) in translations or rotations in any individual plane across all time points for either the tibial or femoral components. Maximum total point motion (MTPM) at 6 months for the tibial component was 0.54 ± 0.25 mm in the CI group and 0.51 ± 0.22 mm in the PSI group (p = 0.77), placing both groups at the low end of the “at risk” category for predicted loosening. Change in MTPM from 6 months to 1 year and again from 1 year to 2 years was <0.2 mm, indicating both groups of implants had stable fixation. Femoral component MTPM was also not different (p > 0.05) between groups. There was no significant difference between PSI and CI groups with respect to magnitude of excursion on both medial (p = 0.54) and lateral (p = 0.81) condyles. There was also no difference in contact locations on both the medial and lateral condyles (p = 0.28 to 0.91) for all angles of flexion. There was no significant difference present between PSI and CI groups when comparing the stability for both the medial (p = 0.06) and lateral (= 0.85) condyles. Condylar separation was present in 3/20 CI patients and 0/16 PSI patients (p = 0.24). Conclusion. Using the latest RSA criteria for predicting failure from early migration, the use of PSI does not provide an advantage over CI for preventing aseptic loosening. Moreover, PSI did not provide any substantial advantage over CI for TKA surgery with respect to contact kinematics

Aim. Diagnosis of periprosthetic shoulder infections (PSI) is difficult as they are mostly caused by low-virulent bacteria and patients do not show typical infection signs, such as elevated blood markers, wound leakage, or red and swollen skin. Ultrasound-guided biopsies for culture may therefore be an alternative for mini-open biopsies as less costly and invasive method. The aim of this study was to determine the diagnostic value and reliability of ultrasound-guided biopsies for cultures alone and in combination polymerase chain reaction (PCR), and/or synovial markers for preoperative diagnosis of PSI in patients undergoing revision shoulder surgery. Method. A prospective explorative diagnostic cohort study was performed including patients undergoing revision shoulder replacement surgery. A shoulder puncture was taken preoperatively before incision to collect synovial fluid for interleukin-6 (IL-6), calprotectin, WBC, polymorphonuclear cells determination. Prior to revision surgery, six ultrasound-guided synovial tissue biopsies were collected for culture and two additional for PCR analysis. Six routine care tissue biopsies were taken during revision surgery and served as reference standard. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV; primary outcome measure), and accuracy were calculated for ultrasound-guided biopsies, and synovial markers, and combinations of these. Results. Fifty-five patients were included. In 24 patients, routine tissue cultures were positive for infection. Cultures from ultrasound-guided biopsies diagnosed an infection in 7 of these patients, yielding a sensitivity, specificity, PPV, NPV, and accuracy of 29.2%, 93.5%, 77.8%, 63.0%, and 65.6%, respectively. Ultrasound-guided biopsies in combination with synovial WBC increased the NPV to 76.7% and accuracy to 73.8%. When synovial WBC and calprotectin were combined with ultrasound-guided biopsies, it resulted in a better diagnostic value: sensitivity 69.2%, specificity 80.0%, PPV 69.2%, NPV 80.0%, and accuracy 75.8%. Ultrasound-guided biopsies in combination with calprotectin and ESR yielded a sensitivity of 50.0%, specificity of 93.8%, PPV of 80.0%, NPV of 78.9%, and accuracy of 79.2%. Synovial fluid was obtained in 42 patients. Sensitivities of WBC, PMN, IL-6, and calprotectin were between 25.0% and 35.7%, specificities between 89.5% and 95.0%, PPVs between 60.0% and 83.3%, NPVs between 65.4% and 69.4%, and accuracies between 64.5% and 70.6%. Conclusions. In this prospective study we showed that ultrasound-guided biopsies for cultures alone and in combination with PCR and/or synovial markers are not reliable enough to use in clinical practice for the preoperative diagnosis of low grade PSI

Computer Assisted Surgery (CAS) and Patient Specific Instrumentation (PSI) have been reported to increase accuracy and predictability of tumour resections. The technically demanding joint-preserving surgery that retains the native joint with the better function may benefit from the new techniques. This cadaver study is to investigate the surgical accuracy of CAS and PSI in joint-preserving surgery of knee joint. CT scans of four cadavers were performed and imported into an engineering software (MIMICS, Materialise) for the 3D surgical planning of simulated, multiplanar joint-preserving resections for distal femur or proximal tibia metaphyseal bone sarcoma. The planned resections were transferred to the navigation system (OrthoMap 3D, Stryker) for navigation planning and used for the design and fabrication of the PSI. Each of the four techniques (freehand, CAS, PSI and CAS + PSI) was used in four joint-preserving resections. Location accuracy (the maximum deviation of distance between the planned and the achieved resections) and bone resection time were measured. The results were compared by using t-test (statistically significant if P< 0.05). Both the CAS+PSI and PSI techniques could reproduce the planned resections with a mean location accuracy of < 2 mm, compared to 3.6 mm for CAS assistance and 9.2 mm for the freehand technique. There was no statistical difference in location accuracy between the CAS+PSI and the PSI techniques (p=0.92) but a significant difference between the CAS technique and the CAS+PSI (p=0.042) or PSI technique (p=0.034) and the freehand technique with the other assisted techniques. The PSI technique took the lowest mean time of 4.78 ±0.97min for bone resections. This was significantly different from the CAS+PSI technique (mean 12.78 min; p < 0.001) and the CAS technique (mean 16.97 min; p = < 0.001). CAS and PSI assisted techniques help reproduce the planned multiplanar resections. The PSI technique could achieve the most accurate bone resections (within 2mm error) with the least time for bone resections. Combining CAS with PSI might not improve surgical accuracy and might increase bone resection time. However, PSI placement on the bone surface depends only on the subjective feeling of surgeons and may not apply if the extraosseous tumor component is large. Combining CAS with PSI could address the limitations

Introduction. With the development of 3D printing technology, there are many different types of PSI in the world. The accuracy of patient specific instrumentation (PSI) in primary total knee arthroplasty (TKA) is dependent on appropriate placement of the cutting blocks. However, previous reports on one type of PSI measured the difference between postoperative prosthetic alignment and postoperative mechanical axis and thus these reports did not evaluate intraoperative comparison of PSIs between two different designs. The purpose of this study was to evaluate the intraoperative accuracy of two different designed PSIs (My knee, Medacta International, Castel San Pietro, Switzerland) with two examiners using CT free navigation system (Stryker, Mahwar, NJ, USA) in regards to sagittal and coronal alignment. Methods. We enrolled 78knees (66 patients) with a primary cemented TKA using two different designed CT-based PSIs (My knee, Medacta International, Castel San Pietro, Switzerland). All operations were performed by two senior surgeons who have experience with greater than 500 TKAs and greater than 200 navigated TKAs. Two examiners were same two surgeons. The study period was between June 2015 and November 2016. The local ethics' committee approved the study prior to its initiation, and informed consent was obtained from all patients. After placement of the PSI on the femur and tibia, the position of the PSI was evaluated by s intraoperative navigation. Two examiners placed two different types (STD(standard) and MIS(minimum invasive surgery)) of PSI on same joint. As required by the PSI, only soft- tissue was removed and osteophytes were left in place. Femoral MIS PSI was required partial remove of lateral cartilage. For the femur, the coronal position in relation to the mechanical axis were documented. For the tibia, the coronal alignment and the tibial slope were documented. Of note, intraoperative modifications to the PSI were not made based upon the results of the navigation. Rather, the findings of the intraoperative navigation were simply documented. Results. The mean age of the cohort was 72.9±7.5years (range, 55–85years). The study included 11men and 55women, with a mean height of 151±8.2cm (range, 135–175cm), mean weight of 59.4±4.3kg (range, 42–82kg), and a mean of Body Mass Index of 25.9±3.6 (range, 17.2–36.4). HKA angle (supine position) measured by CT was 170.8 ±4.4 degree(range, 162.5–182degree). Diagnosis was osteoarthritis in all patient. There was no statistically significant difference in PSI position alignment for femoral flexion, tibial coronal angle, tibial slope between the two groups with two examiners. However, the intraoperative coronal position using the femoral STD PSI significantly deviated from using femoral MIS PSI from both examiners. (PSI vs. MIS, examiner1 p = 0.02, examiner2 p=0.04)

INTRODUCTION. Bone tumour resection and subsequent reconstruction remains challenging for the surgeon. Obtaining adequate margins is mandatory to decrease the risk of local recurrence. Improving surgical margins quality without excessive resection, reducing surgical time and increasing the quality of the reconstruction are the main goals of today's research in bone tumour surgical management. With the outstanding improvements in imaging and computerised planning, it is now a standard. However, surgical accuracy is essential in orthopaedic oncologic surgery (Grimmer 2005). Patient specific instruments (PSI) may greatly improve the surgeon's ability to achieve the targeted resection. Thanks to its physical support, PSI can physically guide the blade yielding to a better control over the cutting process (Wong, 2014). Surgical time might significantly be reduced as well when compared to conventional method or navigated procedure. Finally, reconstruction may gain in rapidity and quality especially when allograft is the preferred solution as PSI can be designed as well for allograft cutting (Bellanova, 2013). Since 2011, PSI have systematically been used in our institution for bone tumour resection and when applicable allograft reconstruction. This paper reports the mid- to long-term medical outcomes on a large series. MATERIALS AND METHODS. Between 2011 and 2016, we systematically used PSI to remove bone tumours in 30 patients. The pre-operative planning involved the tumour delineation drawn on MRI by the surgeon. The MRI and obtained tumour volume were transferred to the CT-scan by image fusion (co- registration). Cutting planes were positioned around the tumour including a safe margin. The PSI were designed to ensure a sufficient stability but kept thin enough to limit the bone exposure. The PSI was manufactured by 3D-printing in a biocompatible and sterilisable material. PSI has been intraoperatively to cut the bone with predetermined margins. Medical files were reviewed for large data collection: type, size and site of the tumour, pre-and post-operative metastatic status, bone and soft tissues resection margins, local recurrence, use of an allograft and a PSI for graft adjustment or not for the reconstruction, the fusion of the allograft when applicable, the follow-up time and early/late complications. RESULTS. Over a period of 5 years, 30 patients were operated on with PSI (10 osteosarcomas, 4 chondrosarcomas, 10 Ewing sarcomas and 6 other types of bone tumours). Mean follow-up was 27±20 months. 18 cases out of 30 have more than 2 years follow-up and 13 out of 30 have more than 3 years of follow-up. Mean operating time was 6h02±3h44. Mean size of the tumours was 8,4±4,7cm and location was the upper limb in 5 cases, inferior limb in 15 cases and the pelvis in 10 occurrences. Metastatic disease developed postoperatively in 5 patients. Surgical margins in the bone were R0 in all cases but one case where a R1 surgery was planned to preserve a nerve root. We did not observe any local recurrence in the bone. Within soft tissues, margins were classified as R0 in 28 patients and R1 in 2 patients. In 26 cases, an allograft was used to reconstruct the bone defect. In 23 of those patients, the allograft was selected by CT scan and cut using a PSI. In the 3 allografts cut free-handily, only one demonstrated a fusion. Of the 23 cut with a guide, 12 fused completely, 2 demonstrated a partial fusion and 9 were not fused at the last follow-up. At the last follow-up, 2 patients were dead of disease, 5 were alive with metastatic disease and 23 were alive without disease. DISCUSSION. Oncology is probably the field where PSI can bring the largest advantage when compared to the conventional procedure. Several papers have reported the use of PSI for bone tumour resection. All of them have shown very promising results on in-vitro experiments (Cartiaux 2014), cadaver experiment (Wong 2012) or small clinical series (Bellanova 2013, Gouin, 2014). None of these papers report a large patient series associated with a clinically relevant follow-up. This series is the first mid- to long-term follow-up series involving PSI tumour surgery. These results are showing strong evidences of clinical improvements. It comes into contradiction with PSI for total knee arthroplasty where controversial results on the patient's outcome has been reported (Thienpont 2014). R0 margin has been systematically obtained for all bone cuttings, and local recurrence has been strongly decreased (3%) when compared to the usual recurrence rates published in the literature (from 15% to 35% according to the location). Allograft fusion seems improved as well thanks to the shape-matching of the selected allograft and a close contact between host and allograft at bony junctions. With a longer follow-up, these evidences should be stronger to definitely make PSI the best option for bone tumour resection

Introduction. Patient-specific instruments (PSI) and surgical-guiding templates are gaining popularity as a tool for enhancing surgical accuracy in the correction of oblique bone deformities Three-dimensional virtual surgical planning technology has advanced applications in the correction of deformities of long bones and enables the production of 3D stereolithographic models and PSI based upon a patient's specific deformity. We describe the implementation of this technology in young patients who required a corrective osteotomy for a complex three-plane (oblique plane) lower-limb deformity. Materials and Methods. Radiographs and computerized tomographic (CT) scans (0.5 mm slices) were obtained for each patient. The CT images were imported into post-processing software, and virtual 3D models were created by a segmentation process. Femoral and tibial models and cutting guides with locking points were designed according to the deformity correction plan as designed by the surgeon. The models were used for preoperative planning and as an intraoperative guide. All osteotomies were performed with the PSI secured in the planned position. Results. A total of 17 patients (9 males and 8 females, average age 14.7 years [range 8–24]) comprised the study group. All of the PSI were excellent fits for the planned bone surfaces during surgery. The osteotomies matched the preoperative planning simulation and allowed for easy fixation with pre-chosen plates. No intra- or postoperative complications were encountered. Surgery time was shortened (101 minutes) and intraoperative blood loose was less compared to historical cases. Clinical and radiographic follow-up findings showed highly satisfactory alignment of the treated extremities in all 17 patients. Conclusions. The use of 3D-printed models and patient-specific cutting guides with locking points increases accuracy, shortens procedure time, reduces intraoperative blood loss, and improves the outcome of osteotomies in young patients with complex oblique bone deformities

Background. Cup anteversion and inclination are important to avoid implant impingement and dislocation in total hip arthroplasty (THA). However, it is well known that functional cup anteversion and cup inclination also change as the pelvic sagittal inclination (PSI) changes, and many reports have been made to investigate the PSI in supine and standing positions. However, the maximum numbers of subjects studied are around 150 due to the requirement of considerable manual input in measuring the PSIs. Therefore, PSI in supine and standing positions were measured fully automatically with a computational method in a large cohort, and the factors which relate to the PSI change from supine to standing were analyzed in this study. Methods. A total of 422 patients who underwent THA from 2011 to 2015 were the subjects of this study. There were 83 patients with primary OA, 274 patients with DDH derived secondary OA (DDH-OA), 48 patients with osteonecrosis, and 17 patients with rapidly destructive coxopathy (RDC). The median age of the patient was 61 (range; 15–87). Preoperative PSI in supine and standing positions were measured and the number of cases in which PSI changed more than 10° posteriorly were calculated. PSI in supine was measured as the angle between the anterior pelvic plane (APP) and the horizontal line of the body on the sagittal plane of APP, and PSI in standing was measured as the angle between the APP and the line perpendicular to the horizontal surface on the sagittal plane of APP (Fig. 1). The value was set positive if the pelvis was tilted anteriorly and was set negative if the pelvis tilted posteriorly. Type of hip disease, sex, and age were analyzed with multiple logistic regression analysis if they were related to PSI change of more than 10°. For accuracy verification, PSI in supine and standing were measured manually with the previous manual method in 100 cases and were compared with the automated system used in this study. Results. The median PSI in the supine position was 5.1° (interquartile range [IQR]: 0.4 to 9.4°), and the median PSI in the standing position was −1.3° (IQR: −6.5 to 4.2°). There were 79 cases (19%) in which the PSI changed more than 10° posteriorly from supine to standing with a maximum change of 36.9° (Fig. 2). In the analysis of the factors, type of hip disease (p = 0.015) and age (p = 0.006, Odds Ratio [OR] = 1.035) were the significant factors. The OR of primary OA (p = 0.005, OR: 2.365) and RDC (p = 0.03, OR: 3.146) were significantly higher than DDH-OA. In accuracy verification, the automated PSI measurement showed ICC of 0.992 (95% CI: 0.988 to 0.955) for supine measurement and 0.978 (95% CI: 0.952 to 0.988) for standing measurement. Conclusions. PSI changed more than 10° posteriorly from supine to standing in 19% of the cases. Age and diagnosis of primary OA and RDC were related to having their pelvis recline more than 10° posteriorly. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Abstract. Background. Conventional TKR aims for neutral mechanical alignment which may result in a smaller lateral distal femoral condyle resection than the implant thickness. We aim to explore the mismatch between implant thickness and bone resection using 3D planning software used for Patient Specific Instrumentation (PSI) TKR. Methods. This is a retrospective anatomical study from pre-operative MRI 3D models for PSI TKR. Cartilage mapping allowed us to recreate the native anatomy, enabling us to quantify the mismatch between the distal lateral femoral condyle resection and the implant thickness. Results. We modelled 292 knees from PSI TKR performed between 2012 and 2015. There were 225 varus knees and 67 valgus knees, with mean supine hip-knee-angle of 5.6±3.1 degrees and 3.6±4.6 degrees, respectively. In varus knees, the mean cartilage loss from medial and lateral femoral condyle was 2.3±0.7mm and 1.1±0.8mm respectively; the mean overstuffing of the lateral condyle 1.9±2.2mm. In valgus knees, the mean cartilage loss from medial and lateral condyle was 1.4±0.8mm and 1.5±0.9mm respectively; the mean overstuffing of the lateral condyle was 4.1±1.9mm. Conclusions. Neutral alignment TKR often results in overstuffing of the lateral condyle. This may increase the patello-femoral pressure at the lateral facet in flexion. Anterior knee pain may be persistent even after patellar resurfacing due to tight lateral retinacular structures. An alternative method of alignment such as anatomic alignment may minimise this problem