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

Patient specific instrumentation (PSI) uses advanced imaging of the knee (CT or MRI) to generate individualised cutting blocks aimed to make the procedure of total knee arthroplasty (TKA) more accurate and efficient. However, in this era of healthcare cost consciousness, the value of new technologies needs to be critically evaluated. There have been several comparative studies looking at PSI versus standard instrumentation. Most compare PSI with conventional instrumentation in terms of alignment in the coronal plane, operative time and surgical efficiency, cost effectiveness and short-term outcomes. Several systematic reviews and meta-analyses have also been published. PSI has not been shown to be superior compared with conventional instrumentation in its ability to restore traditional mechanical alignment in primary TKA. Most studies show comparative efficacy and no decrease in the number of outliers in either group. In terms of operative time and efficiency, PSI tended towards decreasing operative time, saving a mean of five minutes per patient (0 to 20). Furthermore, while some cost savings could be realised with less operative time and reduced instrumentation per patient, these savings were overcome by the cost of the CT/MRI and the cutting blocks. Finally, there was no evidence that PSI positively affected clinical outcomes at two days, two months, or two years. Consequently, current evidence does not support routine use of PSI in routine primary TKA. Cite this article: Bone Joint J 2016;98-B(1 Suppl A):78–80

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. Sagittal lumbar pelvic alignment alters with posterior pelvic tilt (PT) following total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH). The individual value of pelvic sagittal inclination (PSI) following rebalancing of lumbar-pelvic alignment is unknown. In different populations, PT regresses in a linear relationship with pelvic incidence (PI). PSI and PT have a direct relationship to each other via a fixed individual angle ∠γ. This study aimed to investigate whether the new PI created by acetabular component positioning during THA also has a linear regression relationship with PT/PSI when lumbar-pelvic alignment rebalances postoperatively in patients with Crowe type III/IV DDH. Methods. Using SPINEPARA software, we measured the pelvic sagittal parameters including PI, PT, and PSI in 61 patients with Crowe III/IV DDH. Both PSI and PT represent the pelvic tilt state, and the difference between their values is ∠γ (PT = PSI + ∠γ). The regression equation between PI and PT at one year after THA was established. By substituting ∠γ, the relationship between PI and PSI was also established. The Bland-Altman method was used to evaluate the consistency between the PSI calculated by the linear regression equation (ePSI) and the actual PSI (aPSI) measured one year postoperatively. Results. The mean PT and PSI changed from preoperative values of 7.0° (SD 6.5°) and -8.0° (SD 6.7°), respectively, to 8.4° (SD 5.5°) and -4.5° (SD 5.9°) at one year postoperatively. This change shows that the pelvis tilted posteriorly following THA. In addition, when lumbar-pelvic alignment rebalanced, the linear regression equation between PI and PT was PT = 0.45 × PI - 10.5°, and PSI could be expressed as PSI = 0.45 × PI - 10.5° - ∠γ. The absolute difference between ePSI and aPSI was less than 5° in 55 of 61 patients (90.16%). Conclusion. The new PI created by the positioning of the acetabular component significantly affects the PSI when lumbar-pelvic alignment changes and rebalances after THA in patients with Crowe III/IV DDH. Cite this article: Bone Joint J 2025;107-B(2):149–156

Aims. Total knee arthroplasty (TKA) using functional alignment aims to implant the components with minimal compromise of the soft-tissue envelope by restoring the plane and obliquity of the non-arthritic joint. The objective of this study was to determine the effect of TKA with functional alignment on mediolateral soft-tissue balance as assessed using intraoperative sensor-guided technology. Methods. This prospective study included 30 consecutive patients undergoing robotic-assisted TKA using the Stryker PS Triathlon implant with functional alignment. Intraoperative soft-tissue balance was assessed using sensor-guided technology after definitive component implantation; soft-tissue balance was defined as intercompartmental pressure difference (ICPD) of < 15 psi. Medial and lateral compartment pressures were recorded at 10°, 45°, and 90° of knee flexion. This study included 18 females (60%) and 12 males (40%) with a mean age of 65.2 years (SD 9.3). Mean preoperative hip-knee-ankle deformity was 6.3° varus (SD 2.7°). Results. TKA with functional alignment achieved balanced medial and lateral compartment pressures at 10° (25.0 psi (SD 6.1) vs 23.1 psi (SD 6.7), respectively; p = 0.140), 45° (21.4 psi (SD 5.9) vs 20.6 psi (SD 5.9), respectively; p = 0.510), and 90° (21.2 psi (SD 7.1) vs 21.6 psi (SD 9.0), respectively; p = 0.800) of knee flexion. Mean ICPD was 6.1 psi (SD 4.5; 0 to 14) at 10°, 5.4 psi (SD 3.9; 0 to 12) at 45°, and 4.9 psi (SD 4.45; 0 to 15) at 90° of knee flexion. Mean postoperative limb alignment was 2.2° varus (SD 1.0°). Conclusion. TKA using the functional alignment achieves balanced mediolateral soft-tissue tension through the arc of knee flexion as assessed using intraoperative pressure-sensor technology. Further clinical trials are required to determine if TKA with functional alignment translates to improvements in patient satisfaction and outcomes compared to conventional alignment techniques. Cite this article: Bone Joint J 2021;103-B(3):507–514

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

Aims. The purpose of the present study was to compare patient-specific instrumentation (PSI) and conventional surgical instrumentation (CSI) for total knee arthroplasty (TKA) in terms of early implant migration, alignment, surgical resources, patient outcomes, and costs. . Patients and Methods. The study was a prospective, randomized controlled trial of 50 patients undergoing TKA. There were 25 patients in each of the PSI and CSI groups. There were 12 male patients in the PSI group and seven male patients in the CSI group. The patients had a mean age of 69.0 years (. sd. 8.4) in the PSI group and 69.4 years (. sd. 8.4) in the CSI group. All patients received the same TKA implant. Intraoperative surgical resources and any surgical waste generated were recorded. Patients underwent radiostereometric analysis (RSA) studies to measure femoral and tibial component migration over two years. Outcome measures were recorded pre- and postoperatively. Overall costs were calculated for each group. Results. There were no differences (p > 0.05) in any measurement of migration at two years for either the tibial or femoral components. Movement between one and two years was < 0.2 mm, indicating stable fixation. There were no differences in coronal or sagittal alignment between the two groups. The PSI group took a mean 6.1 minutes longer (p = 0.04) and used a mean 3.4 less trays (p < 0.0001). Total waste generated was similar (10 kg) between the two groups. The PSI group cost a mean CAD$1787 more per case (p < 0.01). Conclusion. RSA criteria suggest that both groups will have revision rates of approximately 3% at five years. The advantages of PSI were minimal or absent for surgical resources used and waste eliminated, and for meeting target alignment, yet had significantly greater costs. Therefore, we conclude that PSI may not offer any advantage over CSI for routine primary TKA cases. Cite this article: Bone Joint J 2019;101-B:565–572

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

Aims. We conducted a randomised controlled trial to assess the accuracy of positioning and alignment of the components in total knee arthroplasty (TKA), comparing those undertaken using standard intramedullary cutting jigs and those with patient-specific instruments (PSI). Patients and Methods. There were 64 TKAs in the standard group and 69 in the PSI group. The post-operative hip-knee-ankle (HKA) angle and positioning was investigated using CT scans. Deviation of > 3° from the planned position was regarded as an outlier. The operating time, Oxford Knee Scores (OKS) and Short Form-12 (SF-12) scores were recorded. Results. There were 14 HKA-angle outliers (22%) in the standard group and nine (13%) in the PSI group (p = 0.251). The mean HKA-angle was 0.5° varus in the standard group and 0.2° varus in the PSI group (p = 0.492). The accuracy of alignment in the coronal and axial planes and the proportion of outliers was not different in the two groups. The femoral component was more flexed (p = 0.035) and there were significantly more tibial slope outliers (29% versus 13%) in the PSI group (p = 0.032). Operating time and the median three-month OKS were similar (p = 0.218 and p = 0.472, respectively). Physical and mental SF-12 scores were not significantly different at three months (p = 0.418 and p = 0.267, respectively) or at one year post-operatively (p = 0.114 and p = 0.569). The median one-year Oxford knee score was two points higher in the PSI group (p = 0.049). Conclusion. Compared with standard intramedullary jigs, the use of PSI did not significantly reduce the number of outliers or the mean operating time, nor did it clinically improve the accuracy of alignment or the median Oxford Knee Scores. Our data do not support the routine use of PSI when undertaking TKA. Cite this article: Bone Joint J 2016;98-B:1043–9

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

The aim was to demonstrate that Supramalleolar osteotomy is a valuable treatment method in eccentric ankle arthritis in young and middle aged since it is an under-utilised procedure. We retrospectively analysed the outcome of it performed over 12 year period. We also compared the results of recently introduced computer-assisted PSI Integrated custom-made implants with standard implants. Data was analysed from 48 patients over a period of 12 years of which 40 were by standard implant and 8 by computer assisted custom implant. 31 varus, 18 valgus deformity. The mean age was 57 (26–79 y/o), male:female ratio was 27:19. Mean follow-up was 15.25 months for standard implants; For the computer-assisted procedures the follow up range is 24 to 2 months. TAS, TTS and TT angels were measured pre and post-operatively. Fixation using a plate with/without bone graft or custom-made implant was performed by a single surgeon. MOXFQ and AOFAS questionnaires were completed pre and post-operatively. All followed similar rehabilitation programme. Average radiological healing time was 24.3 weeks. MOXFQ score improved from 55.17 to 25.11 and AOFAS from 20.16 to 56.21. Complications were 2 non-unions, 1 delayed union, 1 stress fracture. 8 patients require fusion/replacement between 3–5 years. The PSI Integrated computer-assisted technique gave improved accuracy than standard freehand method with better scores and a smoother approach for the surgeon. Early results with this technique are encouraging as we were able achieve 3 dimentional correction compared to the 2 dimentional correction achieved by the freehand method. Our results are comparable to similar studies. Being a joint preserving technique, Supra Malleolar Osteotomy should be considered either as an interim or definitive procedure especially with the development of computer assisted technologies which makes the technique easier to reproduce

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

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

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