Background. Variability in component alignment continues to be a major in total knee arthroplasty(TKA). In the long term, coronal plane malalignment has been associated with an increased risk of loosening, insatability, and wear. Recently, patient specific guide in total knee arthroplasty have been introduced, in which preoperative 3-dementional imaging is used to manufacture disposable cutting guide specific to a patient's anatomy. The goals of patient specific guide are to improve the accuracy of post operative alignment and eliminate outlier cases. The aim of this study is to evaluate clinical results and quantify the coronal plane alignment between a group of patients who underwent TKA using patient specific guide versus standard instrumentation. Patients and Method: An unselected consecutive series of seventy patients undergoing primary TKA using the same cruciate retaining cemented total knee system (Vanuard. TM. , Biomet, Inc, warsaw, Indiana USA) between April 2010 and September 2013 were studied. Patients were included only if they were deemed to be candidates for a. Cruciate retaining TKA. Patients were excluded if they had a flexion contracture greater than 40°, or severe valgus or varus deformity. Forty-nine knees was operated a TKA with standard instrumentation method. Subsequently twenty-one knees was received a TKA using CT-based patient specific guide(Signature. TM. ). Postoperatively standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, component angle were measured. The alignment goals were a neutral mechanical axis defined as a hip-to-ankle angle of 0°with the femoral and tibial components aligned perpendicular to the mechanical axis. The total operating time were quantified utilising an operating room database. The total operating time between TKAs performed with standard instrumentation and those performed with patient specific guides was compared in each group. All patients postoperatively was evaluated of clinical results the Japan Orthopedics Association(JOA) Knee scores. Postoperative blood loss volume and postoperative concentrations of D-dimer were also measured. Results. The mechanical axis angle in patient specific guide group was 1.8°, while the standard instrumentation group was 3.4°and there was no statistical significance. The number of outliers for mechanical axis angle was virtually identical between patient specific guide group 29.0% and the standard group 38.8%. The components angle between the two groups did not achieve statistical significance. The operative time in patient specific guide was 117.4 minutes and significantly less compared to the time of standard group 130.4 minutes. The JOA Knee score of standard instrumentation group was 80.8 points, and the score of patient specific guides group was 85.7 points. There was no statistical significance between the two groups on the clinical score. The blood loss volume of between the two group was no different substantially. The postoperative concentrations of D-dimer of patient specific guide group was 5.3(μg/ml), more less significantly than standard group 9.2 (μg/ml). Conclusion. patient specific guide improved operative time and postoperative concentrations of D-dimer in TKA, this study demonstrates patient specific guide to obtain same angle of overall mechanical axis angle and component alignment. The use of patient specific guide did achieve shorter operative time

We have investigated the benefits of patient specific instrument guides, applied to osteotomies around the knee. Single, dual and triple planar osteotomies were performed on tibias or femurs in 14 subjects. In all patients, a detailed pre-operative plan was prepared based upon full leg standing radiographic and CT scan information. The planned level of the osteotomy and open wedge resection was relayed to the surgery by virtue of a patient specific guide developed from the images. The mean deviation between the planned wedge angle and the executed wedge angle was 0° (-1 to 1, . sd. 0.71) in the coronal plane and 0.3° (-0.9 to 3, . sd. 1.14) in the sagittal plane. The mean deviation between the planned hip, knee, ankle angle (HKA) on full leg standing radiograph and the post-operative HKA was 0.3° (-1 to 2, . sd. 0.75). It is concluded that this is a feasible and valuable concept from the standpoint of pre-operative software based planning, surgical application and geometrical accuracy of outcome. . Cite this article: Bone Joint J 2013;95-B, Supple A:153–8

Aims

Patient-specific glenoid guides (PSGs) claim an improvement in accuracy and reproducibility of the positioning of components in total shoulder arthroplasty (TSA). The results have not yet been confirmed in a prospective clinical trial. Our aim was to assess whether the use of PSGs in patients with osteoarthritis of the shoulder would allow accurate and reliable implantation of the glenoid component.

Patient specific cutting guides generated by preoperative Magnetic Resonance Imaging (MRI) of the patient’s extremity have been proposed as a method of improving the consistency of Total Knee Arthroplasty (TKA) alignment and adding efficiency to the operative procedure. The cost of this option was evaluated by quantifying the savings from decreased operative time and instrument processing costs compared to the additional cost of the MRI and the guide. Coronal plane alignment was measured in an unselected consecutive series of 200 TKAs, 100 with standard instrumentation and 100 with custom cutting guides. While the cutting guides had significantly lower total operative time and instrument processing time, the estimated $322 savings was overwhelmed by the $1,500 additional cost of the MRI and the cutting guide. All measures of coronal plane alignment were equivalent between the two groups. The data does not currently support the proposition that patient specific guides add value to TKA

We report on a cadaveric study and early experience using patient specific drill guides to prevent cortex perforations and reduce the need for a trochanteric osteotomy in revision THA. Mimic software (Materialise) was used for 3D analysis of the cement mantle and cement plug. Based on the CT findings a Cannulated drill guide with the shape of the femoral stem was printed in medical graded nylon intraoperative findings and complications were recorded on videotape using a standard 5mm laparoscope for medullary inspection. Surgical Technique was to attain a pre-operative CT scan with MARS protocol of the proximal femur to evaluate the femoral stem positioning, the 3D anatomy of the cement mantle, the length of the cement plug and the quality of the surrounding bone. Subsequent a 3D printing of patient specific cannulated drill guide with the shape of the removed femoral component but an eccentric cannulation was made. Endoscopic inspection was performed of the inside of the cement mantle, then insertion of the autoclaved cannulated drill guide in the existing cement mantle. After perforation of the distal plug through the PSI drill guide using either a long drill or an ultrasound plug perforation tool (Zimmer Biomet, Warsaw) the excessive cement was removed with standard available flexible femoral shaft reamers (Zimmer Biomet). Further laproscopic examination of the femoral canal performed to verify completeness of the cement removal. Results. CT scans with 3D reconstruction of the existing cement mantle is possible using Modern CT with MARS protocols. After the training on sawbones and cadaveric bones a predictable plug perforation was obtained in all clinical cases. There were no intraoperative cortex perforations and no intraoperative femoral fractures. Conclusion. CT scan analysis of femoral cement mantles together with patient specific drill guides are promising tools to reduce the risk of femoral perforation in revision total hip arthroplasty

Abstract. Background. Distal femoral osteotomy is an established successful procedure which can delay the progression of arthritis and the need for knee arthroplasty. The surgery, however, is complex and lengthy and consequently it is generally the preserve of highly experienced specialists and thus not widely offered. Patient specific instrumentation is known to reduce procedural complexity, time, and surgeons’ anxiety levels. 1. in proximal tibial osteotomy procedures. This study evaluated a novel patient specific distal femoral osteotomy procedure (Orthoscape, Bath, UK) which aimed to use custom-made implants and instrumentation to provide a precision correction while also simplifying the procedure so that more surgeons would be comfortable offering the procedure. Presenting problem. Three patients (n=3) with early-stage knee arthritis presented with valgus malalignment, the source of which was predominantly located within the distal femur, rather than intraarticular. Using conventional techniques and instrumentation, distal femoral knee osteotomy cases typically require 1.5–2 hours surgery time. The use of bi-planar osteotomy cuts have been shown to improve intraoperative stability as well as bone healing times. 2. This normally also increases surgical complexity; however, multiple cutting slots can be easily incorporated into patient specific instrumentation. Clinical management. All three cases were treated at a high-volume tertiary referral centre (Istituto Ortopedico Rizzoli, Bologna) using medial closing wedge distal femoral knee osteotomies by a team experienced in using patient specific osteotomy systems. 3. Virtual surgical planning was conducted using CT-scans and long-leg weight-bearing x-rays (Orthoscape, Bath, UK). Patient specific surgical guides and custom-made locking plates were design for each case. The guides were designed to allow temporary positioning, drilling and bi-planar saw-cutting. The drills were positioned such that the drills above and below the osteotomy became parallel on closing following osteotomy wedge removal. This gave reassurance of the achieved correction allowed the plate to be located precisely over the drills. All screw lengths were pre-measured. Discussion. The surgical time reduced to approximately 30 minutes by the third procedure. It was evident that surgical time was saved because no intraoperative screw length measurements were required, relatively few x-rays were used to confirm the position of the surgical guide, and the use of custom instrumentation significantly reduced the surgical inventory. The reduced invasiveness and ease of surgery may contribute to faster patient recovery compared to conventional techniques. The final post-operative alignment was within 1° of the planned alignment in all cases. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

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

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

Introduction & aims. Resurfacing of the patella is an important part of most TKA operations, usually using an onlay technique. One common practice is to medialise the patellar button and aim to recreate the patellar offset, but most systems do not well control alignment of the patella button. This study aimed to investigate for relationships between placement and outcomes and report on the accuracy of patella placement achieved with the aid of a patella Patient Specific Guide (PSG). Method. A databse of TKR patients operated on by five surgeons from 1-Jan-2014 who had a pre-operative and post-operative CT scan and 6-month postoperative Knee Osteoarthritis and Outcome (KOOS) scores were assessed. Knees were excluded if the patella was unresurfaced or an inlay technique was used. All knee operations were performed with the Omni Apex implant range and used dome patella buttons. A sample of 40 TKRs had a patella PSG produced consisting of a replication of an inlay barrel shaped to fit flush to the patient's patella bone. The centre of the quadriceps tendon on the superior pole of the patella bone and the patella tendon on the inferior were landmarked. 3D implant and bone models from the preoperative CT scans were registered to the post-operative CT scan. The flat plane of the implanted patella button was determined and the position of the button relative to the tendon attachments calculated. Coverage of the bone by the button and patellar offset reconstruction were also calculated. The sample of 40 TKRs for whom a patella PSG was produced had their variation in placement assessed relative to the wider population sample. All surgeries were conducted with Omni Apex implants using a domed patella. Results. A total of 322 patients were identified in the database, and 82 were subsequently excluded as inlay rather than onlay patella. 59% (142) were female and the average age was 68.9 years (+/− 7.2). Coverage percentage of the cut patella surface by the button was 67% (± 7%), with 83% (200) knees having greater than 60%, and 40% (96) greater than 70%. Component position was on average centralised in terms of mediolateral position (0.09mm ± 1.93 lateral). When comparing the alignment of the patients whose knees used PSG guides with those who did not, it was found there was a statistically significant reduction in the variation that both external rotation error and flexional error had (p-values 0.048 and 0.022 respectively.). Excess medialisation of the patella button was found to weakly correlate with reduced postoperative KOOS symptoms scores (coefficient=0.14, p-value = 0.035). When subdivided into patients who reported knee clicking sometimes or more often and those who did not, patients with highly medialised buttons had a 1.5× likelihood of reporting clicking of their knee joint (p-value = 0.036). Conclusions. The patella-femoral joint remains a crucial component in the TKA knee, but the process of resurfacing the bone is not well controlled and can negatively influence patient outcomes. PSG's are one potential mechanism of controlling patella component alignment

PURPOSE. To validate the efficacy and accuracy of a novel patient specific guide (PSG) and instrumentation system that enables minimally invasive (MI) short stemmed total shoulder arthroplasty (TSA). MATERIALS AND METHODS. Using Amirthanayagam et al.'s (2017) MI posterior approach reduces incision size and eliminates subscapular transection; however, it precludes glenohumeral dislocation and the use of traditional PSGs and instruments. Therefore, we developed a PSG that guides trans-glenohumeral drilling which simultaneously creates a humeral guide tunnel/working channel and glenoid guide hole by locking the bones together in a pre-operatively planned pose and drilling using a c-shaped drill guide (Figure 1). To implant an Affinis Short TSA system (Mathys GmbH), novel MI instruments were developed (Figure 2) for: humeral head resection, glenoid reaming, glenoid peg hole drilling, impaction of cruciform shaped humeral bone compactors, and impaction of a short humeral stem and ceramic head. The full MI procedure and instrument system was evaluated in six cadaveric shoulders with osteoarthritis. Accuracy was assessed throughout the procedure: 1) PSG physical registration accuracy, 2) guide hole accuracy, 3) implant placement accuracy. These conditions were assessed using an Optotrak Certus tracking camera (NDI, Waterloo, CA) with comparisons made to the pre-operative plan using a registration process (Besl and McKay, 1992). RESULTS. 3D translational accuracy of PSG physical registration was: humeral PSG- 2.2 ± 1.1 mm and scapula PSG- 2.5 ± 0.7 mm. The humeral and scapular guide holes had angular accuracies of 6.4 ± 3.2° and 8.1 ± 5.1°, respectively; while the guide hole positional accuracies on the articular surfaces (which will control bone preparation translational accuracy) were 2.9 ± 1.2 mm and 2.8 ± 1.3 mm. Final implantation accuracy in translation was 2.9 ± 3.0 mm and 5.7–6.8 ± 2.2–4.0° across the implants’ three rotations for the humerus and in translation was 2.8 ± 1.5 mm and 2.3–4.3 ± 2.2–4.4° across the implants’ three rotations for the scapula (Figure 3). DISCUSSION. The overall implantation accuracy was similar to results of previously reported open, unassisted TSA (3.4 mm & 7–12°, Hendel et al., 2012, Nguyen et al., 2009). Analysis of the positional PSG registration accuracy very closely mirrors the final implantation accuracy (humerus:2.2 mm vs 2.9 mm, and scapula:2.2 mm vs 2.8mm), thus, this is likely the primary predictor of implantation accuracy. Furthermore, the greatest component of PSG registration error was mediolateral translation (i.e. along the guiding axis) and thus should not affect guide hole drilling accuracy. The drilled guide hole positional and angular error was low for the humerus (2.9 mm and 6.4°) but somewhat higher in rotation (8.1°) for the glenoid which may indicate a slight shift in the PSG prior to guide hole drilling due to the weight of the arm applied when the PSGs are locked together. In conclusion, this work has detailed the step-by-step surgical errors associated with the developed system and demonstrated that it achieves similar accuracy to open, unassisted TSA, while avoiding complications related to muscular transection and dislocation. Therefore, we believe this technique is worthy of clinical investigation

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. Methods. 100 consecutive THR patients received OPS. TM. 3D femoral planning. For each patient a 3D stem+head position was pre-operatively planned which restored the native head height, restored global offset after cup medialisation and reproduced anterior offset, in the superior-inferior, medial-lateral and anterior-posterior directions respectively. The femoral osteotomy was planned preoperatively and controlled intra-operatively with a patient specific guide. All procedures were performed through a posterior approach with a TriFit/Trinity uncemented implant combination. Post-op implant position was determined from CT. Results. The mean difference between planned and achieved head height was 0.9mm (−1.2mm to 4.6mm). The mean difference between planned and achieved medial offset was −0.9mm (−6.2mm to 3.1mm). The mean difference between planned and achieved anterior offset was 3.2mm (−0.4mm to 6.6mm). Resultant 3D change between the planned and achieved head centre was 4.4mm (0.6mm to 9.1mm). The change in anterior offset was strongly correlated (r=0.78) to the change in achieved stem anteversion in comparison to the plan; mean values of 16.3° and 10.5° respectively. Conclusions. In this single centre pilot study, femoral centre of rotation was accurately reproduced by using 3D templating and controlling the femoral neck osteotomy with a patient-specific guide

Alignment and soft tissue balance are two of the most important factors that influence early and long term outcome of total knee arthroplasty. Current clinical practice involves the use of plain radiographs for preoperative planning and conventional instrumentation for intra operative alignment. The aim of this study is to assess the Signature. TM. Personalised system using patient specific guides developed from MRI. The Signature. TM. system is used with the Vanguard. R. Complete Knee System. This system is compared with conventional instrumentation and computer assisted navigation with the Vanguard system. Patients were randomised into 3 groups of 50 to either Conventional Instumented Knee, Computer Navigation Assisted Knee Arthroplasty or Signature Personalised Knee Arthoplasty. All patients had the Vanguard Total knee Arthroplasty Implanted. All patients underwent Long leg X-rays and CT Scans to measure Alignment at pre-op and 6 months post-op. All patients had clinical review and the Knee Society Score (KSS) at 1 year post surgery was used to measure the outcome. A complete dataset was obtained for 124 patients. There were significant differences in alignment on Long leg films ot of CT scan with perth protocol. Notably the Signature group had the smallest spread of outliers. In conclusion the Signature knee system compares well in comparison with traditional instrumentation and CAS Total Knee Arthroplasty

Osteotomy is one of the oldest orthopaedic interventions and has evolved significantly over the years. The procedure is well established as a biomechanical solution in the treatment of arthritis and instability of the knee. The operation is technically demanding and carries risks of neurovascular injury, inadequate fixation and under- or overcorrection. These technical problems have given osteotomy significant headwind in the orthopaedic community. The relative success of knee arthroplasty (uni or total) in the past decade has fed the perception that this procedure is the only remaining treatment to be trusted for patients with knee arthritis. However, both registry data and single center studies often show disappointing results for knee arthroplasty in the young, active and demanding patient population. Osteotomy has a significant role for these patients, provided they have unicompartmental arthritis with constitutional malalignment. Also, more complex deformities as seen in the post-traumatic setting often need a biomechanical approach based upon osteotomy principles. Recently, technology was developed to allow the surgeon perform a three-dimensional evaluation of the deformity and prediction of postoperative alignment. Patient specific guides with a broad fit on the femur or tibia can guide the osteotomy and fixation accurately, within 2 degrees of accuracy. With this technological approach, a new dawn for osteotomy appears on the horizon

Introduction. Optimal orthopaedic implant placement is a major contributing factor to the long term success of all common joint arthroplasty procedures. Devices such as 3D printed bespoke guides and orthopaedic robots are extensively described in the literature and have been shown to enhance prosthesis placement accuracy. These technologies have significant drawbacks such as logistical and temporal inefficiency, high cost, cumbersome nature and difficult theatre integration. A radically new disruptive technology for the rapid intraoperative production of patient specific instrumentation that obviates all disadvantages of current technologies is presented. Methods. An ex-vivo validation and accuracy study was carried out using the example of placing the glenoid component in a shoulder arthroplasty procedure. The technology comprises a re-usable table side machine, bespoke software and a disposable element comprising a region of standard geometry and a body of mouldable material. Anatomical data from 10 human scapulae CT scans was collected and in each case the optimal glenoid guidewire position was digitally planned and recorded. The glenoids were isolated and concurrently 3D printed. In our control group, guide wires were manually inserted into 1 of each pair of unique glenoid models according to a surgeon's interpretation of the optimal position from the anatomy. The same surgeon used the guidance system and associated method to insert a guide wire into the second glenoid model of the pair. Achieved accuracy compared to the pre-operative bespoke plan was measured in all glenoids in both the conventional group and the guided group. Results. The technology was successfully able to intraoperatively produce sterile, patient specific guides according to a pre-operative plan in 5 minutes including device set up and planning, at a minimal cost. In the manual insertion group, average accuracy achieved was 6.8° and 1.58mm with respect to the plan compared to the guided group where an average of 0.74mm and 1.72 ° was achieved

Patient specific instruments have been developed in response to the conundrum of limited accuracy of intramedullary and extramedullary alignment guides and chaos caused by computer assisted orthopaedic surgery. This technology facilitates preoperative planning by providing the surgeon with a three dimensional (3-D) anatomical reconstruction of the knee, thereby improving the surgeon's understanding of the preoperative pathology. Intramedullary canal penetration of the femur and tibia is unnecessary, and consequently, any potential for fat emboli is eliminated. Component position and alignment are improved with a decrease in the number of outliers. Patient specific instruments utilise detailed magnetic resonance imaging (MRI) or computed tomography (CT) scans of the patient's knee with additional images from the hip and ankle for determination of critical landmarks. From these studies a 3-D model of the patient's knee is created and with integration of rapid prototyping technology, guides are created to apply to the patient's native anatomy to direct the placement of the cutting jigs and ultimately the placement of the components. The steps in considering utilization of patient specific guides are as follows: 1) the surgeon determines that the patient is a candidate for TKA, 2) an MRI or CT scan is obtained at an approved facility in accordance with a specific protocol, 3) the MRI or CT is forwarded to the manufacturer, 4) the manufacturer creates the 3-D reconstructions, anatomical landmarks are identified, implant size is determined, and ultimately femoral and tibial component implant placement is determined via an algorithm, 4) the surgical plan is executed, 5) the physician reviews and modifies or approves the plan, 6) the guides are then produced via rapid prototyping technology and delivered to the hospital for the surgical procedure. Guides generated from MRIs are designed to uniquely register on cartilage surface whereas guides produced from CT scans must register on bony anatomy. There are currently two types of guides produced: those which register on the femur and tibia and allow for the placement of pins to accommodate the standard resection blocks; and those produced by some manufacturers which accommodate the saw blade and therefore are a combination of resection and pin guides. The utilization of patient-specific positioning guides in TKA has several benefits. They facilitate preoperative planning, obviate the need for violation of the intramedullary canals, reduce operating times and improve OR efficiency, decrease instrumentation requirements and thereby reduce potential for perioperative contamination. They are easier to use than computer navigation with no capital equipment purchase and no significant learning curve. Most importantly, patient-specific guides facilitate accurate component position and alignment, which ultimately has been shown to enhance long-term survivorship in total knee arthroplasty

Patients presenting with arthrosis following high tibial osteotomy (HTO) pose a technical challenge to the surgeon. Slight overcorrection during osteotomy sometimes results in persisting medial unicompartmental arthrosis, but with a valgus knee. A medial UKA is desirable, but will result in further valgus deformity, while a TKA in someone with deformity but intact cruciates may be a disappointment as it is technically challenging. The problem is similar to that of patients with a femoral malunion and arthrosis. The surgeon has to choose where to make the correction. An ‘all inside’ approach is perhaps the simplest. However, this often means extensive release of ligaments to enable ‘balancing’ of the joint, with significant compromise of the soft tissues and reduced range of motion as a consequence. As patients having HTO in the first place are relatively high demand, we have explored a more conservative option, based upon our experience with patient matched guides. We have been performing combined deformity correction and conservative arthroplasty for 5 years, using PSI developed in the MSk Lab. We have now adapted this approach to the failed HTO. By reversing the osteotomy, closing the opening wedge, or opening the closing wedge, we can restore the obliquity of the joint, and preserve the cruciate ligaments. Technique: CT based plans are used, combined with static imaging and on occasion gait data. Planning software is then used to undertake the arthroplasty, and corrective osteotomy. In the planning software, both tibial and femoral sides of the UKA are performed with minimal bone resection. The tibial osteotomy is then reversed to restore joint line obliquity. The placing of osteotomy, and the angling and positioning in relation to the tibial component are crucial. This is more important in the opening of a closing wedge, where the bone but is close to the keel cut. The tibial component is then readjusted to the final ‘Cartier’ angle. Patient guides are then made. These include a tibial cutting guide which locates both the osteotomy and the arthroplasty. At operation, the bone cuts for the arthroplasty are made first, so that these cuts are not performed on stressed bone. The cuts are not in the classical alignment as they are based upon deformed bone so the use of patient specific guides is a real help. The corrective osteotomy is then performed. If a closing wedge is being opened, then a further fibular osteotomy is needed, while the closing of an opening wedge is an easier undertaking. Six cases of corrective osteotomy and partial knee replacement are presented. In all cases, the cruciates have been preserved, together with normal patello-femoral joints. Patient satisfaction is high, because the deformity has been addressed, restoring body image. Gait characteristics are those of UKA, as the ACL has been preserved and joint line obliquity restored

Achieving optimal acetabular cup orientation in Total Hip Replacement (THR) remains one of the most difficult challenges in THR surgery (AAOR 2013) but very little has been added to useful understanding since Lewinnek published recommendations in 1978. This is largely due to difficulties of analysis in functional positions. The pelvis is not a static reference but rotates especially in the sagittal plane depending upon the activity being performed. These dynamic changes in pelvic rotation have a substantial effect on the functional orientation of the acetabulum, not appreciated on standard radiographs [Fig1]. Studies of groups of individuals have found the mean pelvic rotation in the sagittal plane is small but large individual variations commonly occur. Posterior rotation, with sitting, increases the functional arc of the hip and is protective of a THR in regards to both edge loading and risk of dislocation. Conversely Anterior rotation, with sitting, is potentially hazardous. We developed a protocol using three functional positions – standing, supine and flexed seated (posture at “seat-off” from a standard chair). Lateral radiographs were used to define the pelvic tilt in the standing and flexed seated positions. Pelvic tilt was defined as the angle between a vertical reference line and the anterior pelvic plane (defined by the line joining both anterior superior iliac spines and the pubic symphysis). In the supine position pelvic tilt was defined as the angle between a horizontal reference line and the anterior pelvic plane. Supine pelvic tilt was measured from computed tomography. Proprietary software (Optimized Ortho, Sydney) based on Rigid Body Dynamics then modelled the patients’ dynamics through their functional range producing a patient-specific simulation which also calculates the magnitude and direction of the dynamic force at the hip and traces the contact area between prosthetic head/liner onto a polar plot of the articulating surface, Fig 2. Given prosthesis specific information edge-loading can then be predicted based on the measured distance of the contact patch to the edge of the acetabular liner. Delivery of desired orientation at surgery is facilitated by use of a solid 3D printed model of the acetabulum along with a patient specific guide which fits the model and the intra-operative acetabulum (with cartilage but not osteophytes removed) - an incorporated laser pointer then marks a reference point for the reamer and cup inserter to replicate the chosen orientation. Results and conclusions. The position of the pelvis in the sagittal plane changes significantly between functional activities. The extent of change is specific to each patient. Spinal pathology is a potent “driver” of pelvic sagittal rotation, usually unrecognised on standard radiographs. Pre-operative patient assessment can identify potential orientation problems and even suitability for hard on hard bearings. Optimal cup orientation is likely patient-specific and requires an evaluation of functional pelvic dynamics to pre-operatively determine the target angles. Post-operatively this technique can identify patient and implant factors likely to be causing edge loading leading to early failure in metal on metal bearings or squeaking in ceramic on ceramic bearings

Introduction. Appropriate acetabular cup orientation is an important factor in reducing instability and maximising the performance of the bearing after Total Hip Arthroplasty (THA). However, postoperative analyses of two large cohorts in the US have shown that more than half of cups are malorientated. In addition, there is no consensus as to what inclination and anteversion angles should be targeted, with contemporary literature suggesting that the orientation should be customised for each individual patient. The aim of this study was to measure the accuracy of a novel patient specific instrumentation system in a consecutive series of 22 acetabular cups, each with a customised orientation. Methodology. Twenty-two consecutive total hip replacement patients were sent for Trinity Optimized Positioning System (OPS) acetabular planning (Optimized Ortho, Sydney). The Trinity OPS planning is a preoperative, dynamic analysis of each patient performing a deep flexion and full extension activity. The software calculates the dynamic force at the hip to be replaced and plots the bearing contact patch as it traces across the articulating surface. The software modelled multiple cup orientations and the alignment which best centralised the load was chosen by the surgeon from the preoperative reports. Once the target orientations had been determined, a unique patient specific guide was 3D printed and used intra-operatively with a laser guided system to achieve the planned alignment, Fig 1. All patients received a post-operative CT scan at 3 months and the radiographic cup inclination and anteversion was measured. The study was ethically approved by The Avenue Hospital Human Research Ethics Committee, Trial Number 176. Results. The mean planned radiographic inclination, reference to the Anterior Pelvic Plane (APP), was 42.8° (range 36.2° – 50.1°). The mean planned radiographic anteversion, reference to the APP, was 28.3° (range 19.4° – 37.0°). Only 23% of the planned orientations fell within Lewinnek's “safe zone”, taking into consideration that that this safe zone is not comparable to the coronal plane of radiographs. However, all 22 cups were planned within a range of 40° ± 10° of inclination and 25° ± 10° of anteversion, when referenced to the coronal plane when supine. The mean inclination difference between the planned and achieved orientations was −1.3° (range −7.6° – 9.2°). The mean anteversion difference was 1.2° (range −5.3° – 7.0°). The mean absolute difference was 4.2° for inclination (range 0.4° – 9.2°) and 3.6° for anteversion (range 0.6° – 7.0°). All 22 cups were within ±10° of their intended target orientation, Fig 2. All 22 cups were within the range of 40° ± 10° of inclination and 25° ± 10° of anteversion, when reference to the coronal plane when supine, Fig 3. Conclusions. These are the early results of a new technology for planning and delivering a customised acetabular cup orientation. We expect further improvements in accuracy with current developments. However, the results suggest that Trinity OPS is a simple way to achieve a patient-specific cup orientation, with accuracy comparable to imageless navigation

3D printing and rapid prototyping in surgery is an expanding technology. It is often used for preoperative planning, procedure rehearsal and patient education. There have been recent advances in orthopaedic surgery for the development of patient specific guides and jigs. The logical next step as the technology advances is the production of custom orthopaedic implants. I aimed to use freely available open source software and online cloud 3D printing services to produce a patient specific orthopaedic implant without requiring the input of a university department, specialised equipment or implant companies. Using standard CT scan DICOM data, a 3D surface reconstruction was made of a patient's uninjured radial head using open source DICOM viewer OsiriX. This was then manipulated in other open source software packages called Meshlabs and Netfabb to create a mirror image 3D model of the radial head with a stem to produce a prosthesis suitable to replace the contralateral fractured radial head. This was then uploaded and printed in stainless steel via cloud printing service . Shapeways.com. . The model produced was an exact replication of the patient's original anatomy, except a mirror image suitable for replacement of the contralateral side. The process did not involve any specialist equipment or input from an academic department or implant company. It took a total of 10 days to produce and cost less than £40. From this study I was able to show that production of patient specific orthopaedic implants is possible. It also highlights that the technology is accessible to all, and does not require any special equipment or large investment. It can be achieved quickly and for a very small financial outlay. As a proof of concept it has been very successful

A prospective randomized trial on 128 patients with end-stage osteoarthritis was conducted to assess the accuracy of patient-specific guides. In cohort A (n = 64), patient- specific guides from four different manufacturers (Subgroup A1 Signature ®, A2 Trumatch ®, A3 Visionaire ® and A4 PSI ®) were used to guide the bone cuts. Surgical navigation was used as an intraoperative control for outliers. In cohort B (n = 64), conventional instrumentation was used. All patients of cohorts A and B underwent a postoperative full-leg standing X-ray and CT scan for measuring overall coronal alignment of the limb and three-planar alignment of the femoral and the tibial component. Three-planar alignment was the primary endpoint. Deviation of more than three degrees from the target in any plane, as measured with surgical navigation or radiologic imaging, was defined as an outlier. In 14 patients (22%) of cohort A, the use of the patient-specific guide was abandoned because of outliers in more than one plane. In 18 patients (28%), a correction of the position indicated by the guide, was made in at least one plane. A change in cranial-caudal position was most common. Cohort A and B showed a similar percentage of outliers in long-leg coronal alignment (24.6%, 28.1%, p = 0.69), femoral coronal alignment (6.6%, 14.1%, p = 0.24) and femoral axial alignment (23%, 17.2%, p = 0.50). Cohort A had more outliers in coronal tibial alignment (14.6%) and sagittal tibial alignment (21.3%) than cohort B (3.1%, p = 0.03 and 3.1%, p = 0.002, respectively). These data indicate that patient specific guides do not improve accuracy in total knee arthroplasty

The current generation of knee replacements are based upon assumptions from kinematic studies that preceded their designs. These implants were further limited by practical restrictions imposed by affordability, materials and manufacturing, and finally by the methods available to surgeons to prepare the bone and implant them. The early designs of knee seldom distinguished left from right, as the early kinematic work had not appreciated the very different functions of the medial and lateral compartments. Trochlea shape and position within devices was also limited by the published work on the way the knee bends. Surgical insertion has been limited to landmark based registration, and adjustment of the kinematics by soft tissue releases. However accurately such operations were performed, they could not restore normal function, as the kinematics of the joint were quite different from the normal knee. Recently, we have begun to appreciate three distinct axes of the knee joint: the flexion axis, the extension axis and the trochlea axis. These can be reliably found from 3d imaging, but cannot be immediately established by eye, or by conventional jigs, which must rely on unreliable landmarks acquired in surgery. The current market leaders in knee joint sales do not reflect these three axes in their joint designs, so the instrumentation used to insert them cannot restore the kinematics of the normal knee. The emerging partial replacements can be designed to take the axes and their resulting kinematics into account. If they are then inserted using robotic assistance, or patient specific guides, they can restore joints to these axes reliably. Knee function following such conservative surgery reflects this improvement in kinematics with higher functional scores and faster top walking speeds than has ever been possible using conventional devices inserted using the conventional landmark based surgical techniques

Summary Statement. We are taking very expensive cutting edge technology, usually reserved for industry, and using it with the help of open source free software and a cloud 3D printing services to produce custom and anatomically unique patient individual implants for only £32. This is approx. 1/100. th. of the traditional cost of implant production. Introduction. 3D printing and rapid prototyping in surgery is an expanding technology. It is often used for preoperative planning, procedure rehearsal and patient education. There have been recent advances in orthopaedic surgery for the development of patient specific guides and jigs. The logical next step as the technology advances is the production of custom orthopaedic implants. Our aim was to use freely available open source software, a personal computer and consumer access online cloud 3D printing services to produce an accurate patient specific orthopaedic implant without utilising specialist expertise, capital expenditure on specialist equipment or the involvement of traditional implant manufacturing companies. This was all to be done quickly, cost effectively and in department. Methods & Materials. Using standard computed tomography (CT) scan and the standard file format of digital imaging and communications in medicine (DICOM) data, a 3D surface reconstruction was made of a cadaveric radial head using the software OsiriX (DICOM image processing software for Apple OS X). This data was then processed in Meshlabs (a system for the processing and editing of unstructured 3D triangular meshes) to create a mirror image 3D model of the radial head with a stem added to produce prosthesis suitable to replace the contra lateral radial head. Both packages are distributed under open-source licensing—Lesser General Public Licence (LGPL)—and are therefore free. This was then uploaded and 3D printed using a process of selective laser sintering (SLS) in stainless steel via the commercial cloud printing service . Shapeways.com. . Results & Conclusions. The model produced was an accurate mirror image replica of the patient's original anatomy (all measurements equal +/− 0.2mm using TS411212 Digital Vernier Expert Caliper 300mm P=0.001 Showing no significant statistical difference. Production from original CT scan took a total of 10 days and the total cost including shipping was £32. This was then re-implanted in to the contra lateral cadaveric radius. We achieved our aims and goals of quick, cost effective and accurate implant creation

Component and limb alignment are important considerations during Total Knee Arthroplasty (TKA). Three-dimensional positioning of TKA implants has an effect on implant loosening, polyethylene stresses, and gait. Furthermore, alignment, in conjunction with other implant and patient variables such as body mass index (BMI) influence osseous loading and failure rates. Fortunately, implant survivorship after TKA has been reported to be greater than 95% at 20 years, despite up to 28% of TKAs having component position greater than 3 degrees from neutral. How good are we at positioning TKA implants with standard instrumentation? Ritter, et al examined 6,070 primary TKAs and found that from 2 degrees – 7 degrees of valgus, the failure rate was 0.5% for limb alignment. Importantly 28% of the TKAs were outside the 2 degrees – 7 degrees range in the hands of experienced surgeons. What about cases with retained hardware or deformities that preclude IM or EM guides. Clearly there is room for improvement in surgical technique, but this improvement must be (1) time efficient and cost effective; (2) have a low complication rate, and (3) be reproducible with a minimal learning curve. One of the technologies that has been developed to help surgeons implant and position TKA components is a patient matched guide. Preoperative computerised planning of the arthroplasty, development of patient specific guides, combined with limited mechanical instruments has been a significant step forward for the surgeon and patient. “The logistical benefits include possible decreased operating room time, decreased turnover time, less time spent sterilising and preparing trays, less inventory, less strain on surgical technicians and nurses, and no capital cost associated with computer navigation. Patient benefits include potentially less tourniquet time, less surgical exposure, no requirement of intramedullary canal preparation, and improved mechanical alignment, which may translate to increased implant longevity. Surgeon benefits include potentially more accurate landmark registration than computer navigation, more efficient surgery, decreased intraoperative stress due to less required decision making, and the ability to perform more surgeries due to time saved.”. Ng, et al compared 569 TKAs performed with patient-specific positioning guides and 155 with manual instruments. The overall mean hip-knee-ankle angle for patient-specific positioning guides (180.6 degrees) was similar to manual instrumentation (181.1 degrees), but there were fewer ± 3 degrees hip-knee-ankle angle outliers with patient-specific positioning guides (9%) than with manual instrumentation (22%)

Early developments of computer assisted TKA focused on improving the technical aspects of proper registration, improved ease of use of instrumentation to ensure proper placement of cutting blocks and implants, and to document the technical improvements in alignment that come with the use of these technologies. There was minimal adoption of these technologies, as costs have been high and measured improvement in outcomes has not been demonstrated. Patient specific instrumentation (PSI), involving preoperative three dimensional imaging and engineering of patient specific guides have been more actively embraced by the orthopaedic community – with industry embracing the technology and promoting it vigorously. This has increased interest in the use of three dimensional technologies – with reported use by up to 14% of orthopaedists in the US- despite the fact that scientific evidence has been mixed. The next generation is merging these technologies, taking the best features of both to give the surgeon control of the patient specific TKA process. Sophisticated morphing technology coupled with innovative instrumentation now allows MONITORED real time PSI – affording the surgeon a means to fully understand the knee deformity being addressed, make decisions based on quantitative information that is accurate and easy to assess, and to resect and position parts as planned, confirming position easily (See Figure 1 & Figure 2). Additional ability to perform and monitor balancing is available if desired. From April 2012 to April 2013 sixty-two TKAs in 56 patients underwent TKA using the Exactech GPS system. Twenty-four knees had CR TKA for varus deformity, 5 for valgus deformity; 27 had PS TKA for varus deformity, 5 for valgus deformity. The average AP alignment was 4.0°; the average clinical ROM at the most recent follow-up for CR TKA was 107° vs. 112° for PS TKA which was not significantly different. One knee has been revised to a more constrained insert for CR deficiency. These cases were to validate the integrity of the instruments and software of a new navigation system. In April 2013, personalized instrumentation has been introduced to easily position femoral resection pins through a single, navigated instrument. Pin accuracy and cutting efficiency are easily documented, and proper femoral position in all planes is controlled. No additional imaging is needed, and the surgeon controls all aspects of decision making directly, monitored real-time patient specific TKA. It can easily be integrated for a balanced gap approach to implant positioning. This represents the newest application of three dimensional technologies and continues the field moving toward technologies that allow the surgeon to directly control all aspects of patient specific TKA

Introduction:. Successful total joint arthroplasty requires accruate and reproducible acetabular component position. Acetabular component malposition has been associated with complications inlcuding dislocation, implant loosening, and increased wear. Recent literature had demonstrated that high-volume fellowship trained arthroplasty surgeons are in the “safe zone” for cup inclination and anteversion only 47% of the time. (1) Computer navigation has improved accuracy and reproducibility but remains expensive and cumbersome to many hospital and physicians. Patient specific instrumentation (PSI) has been shown to be effective and efficient in total knee replacements. The purpose of this study was to determine in a cadaveric model the anteversion and inclination accuracy of acetabular guides compared to a pre-operitive plan. Methods:. 8 fresh-frozen cadaveric pelvis specimens underwent Computer Tomography (CT) in order to create a 3D reconstruction of the acetabulum. Based on these 3D reconstruction, a pre-operative plan was made positioning the patient specific acetabulum guides at 40 degrees of inclination and 20 degrees of anteversion in the pelvis.(Figure 1) The guides were created based on the specific bony morphology of the acetabular notch and rim. The guides were created using a 3D printer which allowed for precise recreation of the virtual model. 7 cadaveric specimens underwent creation and implantation of a acetabular guide specific to each specimens bony morphology. Ligamentum, pulvinar, and labum were removed for each cadaver prior to implantation to prevent soft tissue obstruction. The guides were inserted into the acetabular notch with the final position based on the fit of the guide in the notch. (Figure 2) Post-implantation CT was then performed and inclination and anteversion of the implanted guide measured and compared to the preoperative plan. Results:. In 7 cadaveric specimens post-implantation CT scans were performed and anteversion and inclindation of each guide was calculated and compared to pre-operative plan of 20 degrees anteversion and 40 degrees of inclincation. On average, anteversion in the 7 cadavers measured 20.9 degrees with a standard deviation of 1.8 degrees. Inclincation measured 37.8 degrees with a standard deviation of 3.5 degrees. (Figure 3). Discussion and Conclusion:. This study demonstrates a proof of concept that patient specific acetabular guides based on pre-operative CT scans and implanted in the human pelvis accurately reproduce the preoperative plan. Guide position was 20.9 degrees of anteversion and 37.8 degrees of inclination with a SD of 1.8 and 3.5 degrees respectively. Soft tissue obstruction may result in increased error in some specimens. This study demonstrates that patient specific models can be made and implanted based on notch fit geometry. Further study is currently underway to using a instrument based on the angle of the cup face is order to guide final cup implanation

We present a new technique for TKA implantation which utilizes patient-specific femoral and tibial positioning guides developed from MRI to offer an individualized approach to total knee replacement. This is a prospective non controlled study which aims to analyse the precision of this technique, its advantages and inconvenients in comparison with the conventional instrumented technique. Material. The MRI provides a consistent three-dimensional data set of the patient's anatomy which allows for 3D axis identification. The ideal position and sizing is performed by the surgeon on this 3D model and the patient specific guides are manufactured in advance in order to reproduce the bone cuts corresponding to this positioning and implant size. There are no intramedullary nor extramedullary instruments during the surgery. Method. We compared 20 patients operated with this technique with 20 patients operated with the conventional technique. The hypothesis was a difference < 2° between the 2 techniques. The measured parameters were:. HKS, HKA, tibial slope, femoral rotation on CT. Duration, bleeding, pain on VAS and morphine consumption, active flexion, KSS, Oxford score, recovery of independant walking and delay of return to home. Both groups were identical for gender, age, BMI, etiology, comorbidities, pain and rehabilitation protocols. Results. There were no significant differences on HKA, HKS angles, femoral rotation, active flexion, pain, length of hospital stay. The surgery with the patient specific instruments was 10 minutes shorter than the conventional one (p < 0,05) and the bleeding was inferior with a ratio of 1/3 (p=0,02). There were no complications with this technique and the use of the conventional guides were never necessary with the patient specific instrumentation. Discussion and Conclusion. The patient specific instrumentation for TKA has a precision identical to that of the conventional technique, including for femoral rotation and ligament balance. The advantages of this method are:. Reduced per and post operative bleeding. Shortening of the operative procedure. It is reproducible, including for less experimented surgeons and allows teaching and assistance in a lower technological institution. The number of implant sizes is much inferior (2/9) just as the quantity of instruments to be sterilised. These advantages induce a cost reduction which could be inferior to the price of the procedure

The development of the High Reliability Organization focused on safety in organizations such as nuclear power plants, to avoid catastrophes in an environment where accidents might be expected due to risk factors and complexity. (Figure 1) The Agency for Healthcare Research and Quality applied High Reliability Concepts to hospitals in an effort to improve safety and quality. The Institute for Healthcare Improvement has further expanded this approach to include establishing processes to ensure highly reliable care through analysis, design or redesign, using a model for improvement, and supported by technology and the physical environment. These concepts can be applied to total knee replacement by identifying key processes, conducting regular measurement and analysis, and ensuring daily problem solving to create and maintain process reliability. The application of patient specific technology to our conventional total knee replacement procedures creates an opportunity to improve both quality and safety in total knee replacement procedures. Preoperative imaging and use of computer software allows the surgeon to develop an individual blueprint for each operative procedure. A patient specific cutting guide is fabricated for use in surgery. Intra-operative measurement of bone cuts with comparison to the planned blueprint allows correction of inaccurate bone cuts during surgery. Post operative CT scanning provides a final accurate check of limb, knee and implant alignment in 3 dimensions, with comparison to the preoperative plan. Feedback from the surgeon to the engineers involved in the planning process allows daily improvement of the guide fit, cut accuracy and accuracy of limb, knee and implant alignment for these procedures. Patient reported outcome measures such as the Oxford Knee Score or WOMAC score can be carried out preoperatively and at 6 months post op, to assess reduction of pain and functional improvements resulting from the operative procedure. Ongoing annual patient surveillance using the 12 questions on the Oxford Knee Score, one question about satisfaction, and one question asking if the patient has undergone further surgery on the operative knee, can help assess the durability of the patient outcomes and the longevity of the prosthesis. Use of patient specific cutting guides, coupled with preoperative software for planning a kinematically aligned TKA, has demonstrated improved RCT outcomes at the Phoenix VA. Figure 2 compares the distribution of WOMAC scores for kinematically aligned and mechanically aligned TKA. Individualizing the alignment for each patient has narrowed the distribution of the scores, with 87% of the kinematically aligned scores better than the median score for mechanically aligned patients. There have been additional recent preoperative, perioperative and postoperative processes and checklists designed to increase quality and safety of TKA. Medical team training for preoperative briefing and post operative debriefing, use of the AAOS new STEPPS training program, monitoring post operative results with the NSQIP/VASQIP program and database give us additional tools to improve safety and quality. Coupled with patient specific alignment technology, I believe we currently have an excellent opportunity to move toward High Reliability in total knee replacement

Background. Osteotomies around the knee have been used to correct lower limb mal-alignment for over 50 years. The procedure is technically demanding and carries specific risks of neurovascular injury, incorrect planning and execution, and insufficient fixation. In recent years, with the advent of locking plates, fixation techniques have improved significantly but the correct planning and execution of the operation remains difficult. Despite the availability of CT and MRI 3D imaging, surgical planning is still traditionally performed on 2D plain X-rays [1]. Especially with multi-planar deformities, this technique is prone to error. The aim of this clinical pilot study is to evaluate the feasibility of virtual pre-operative three-dimensional planning and correct execution of osteotomies around the knee with the aid of patient specific surgical guides and locking plates. Patients and methods. Eight consecutive patients, presenting with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software (Mimics® 3-matic®, Materialise, Leuven Belgium) [2]. These models were used to evaluate the required surgical correction. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment [3]. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation (see figure 1). Apart from guiding the osteotomy, the patient specific surgical guide also guided drilling of the planned screw holes. Post-operative assessment of the correction was obtained through planar X-rays, CT-scan and full leg standing X-ray. Results. One three-planar, three bi-planar and four single-plane osteotomies were performed. All guides could be used during surgery and served accurate guidance of the osteotomy plane and screwholes. The guides matched the bone very well in all cases without remaining toggle. The maximum deviation between the planned pre-operative wedge angle and the executed post-operative wedge angle was 1° in the coronal, sagittal and horizontal plane. The desired mechanical femorotibial axis on full-leg standing X-rays was achieved in 6 patients. Two patients were undercorrected by 1° and 2° respectively. No significant peri-operative complications occurred. Conclusion. 3D planning and guided correction of multi-planar deformity of femur or tibia is a feasible and accurate novel technique

Introduction:. Recently there has been interest in an alternative method of aligning a total knee arthroplasty (TKA) referred to as kinematic alignment. The theoretical appeal of this method is that alignment of each patient's knee can be individualized through the use of preoperative imaging and computer software, with the goal of achieving pre-arthritic alignment through restoration of the axes of rotation of each particular knee. Clinical studies have evaluated the outcomes of this new alignment technique, but to date there have been no randomized controlled trials comparing kinematic alignment to mechanical alignment. This randomized controlled trial was conducted to compare kinematically aligned and mechanically aligned TKA outcomes of knee pain, function and motion at two years' post-op, along with a comparison of limb, knee, and implant alignment of the two methods. Methods and Materials:. Forty-four patients were surgically treated with kinematically aligned TKA (figure 1) with the use of patient specific guides, and forty-four patients were surgically treated with mechanically aligned TKA with the use of conventional instruments. All patients underwent CT long leg scanograms after surgery, and outcomes data were collected at a minimum of 2 years. The patient, radiographic evaluator, and clinical evaluator were blinded as to the alignment method. Results. At a minimum of two years, all outcomes were better in the kinematically aligned group, as determined by the Oxford Knee Score of 41 which was 8 points better (p < 0.001), WOMAC score of 12 which was 13 points better (p = 0.002), Combined Knee Society Score of 164 which was 28 points better (p = 0.001) and flexion of 123 degrees which was 11 degrees better than the mechanically aligned group (p = 0.002). The odds ratio of having a pain free knee at 2 years with the kinematically aligned technique (Oxford and WOMAC pain scores) was 4.1 and 3.53 respectively, compared with the mechanically aligned technique. The hip-knee-ankle angle (0.3° difference; p = 0.693) and anatomicangle of the knee (0.8° difference; p = 0.131) were similar in the two groups. In the kinematically-aligned group, the angle of the femoral component was 2.4° more valgus (p < .001) and the angle of the tibial component was 2.3° more varus (p < .001) than the mechanically-aligned group (Figure 2). Discussion:. The Oxford Knee Score, WOMAC Score, Combined Knee Society Score and flexion were significantly better in the kinematic group at a minimum of two years. Oxford Knee and WOMAC pain scores were significantly better, and the number of pain free patients at 2 years was 3–4 times higher in the kinematically aligned group. The obliquity of the joint line was more anatomic in the kinematically aligned total knee replacement. This study showed that individualizing a total knee arthroplasty using 3-dimensional imaging, preoperative computer planning, and rapid prototyping technology in an attempt to replicate an individual patient's knee kinematics, provided better pain relief and restored better function and flexion compared to the mechanical alignment technique performed with conventional instruments

Introduction. In major orthopaedic departments, typically several total knee systems are used. Each system requires several sets of instruments, each set with many trays of complicated and expensive parts. The logistics and costs of maintainance are considerable. Our overall goal is to investigate the feasibility of autoclavable single-use 3D printed instruments made from a polymeric material, used for any type of total knee design. The procedure will be standardized and adjustments easy to implement. Each set will be packaged individually, and used for a single case. There are many aspects to this study; in this part, the aims are to identify suitable materials for autoclavability and strength, and then to compare the accuracy of a novel design of 3D printed tibial cutting guide with a current metallic guide. Methods. Test samples were designed to simulate shapes in current instruments, such as mating pegs and holes, threaded screws, and slotted blocks. Each set was produced in biocompatible materials, ABS-M30i, VeroClear (MED610), Ultem1010, and Nylon 12. Each part was laser scanned, and then imaged virtually using a reverse engineering software (GeoMagic). Manual measurements of key dimensions were also made using calipers. The parts were autoclaved using a standardized protocol, 30 minutes at 250° F. All parts were re-scanned and measured to determine any changes in dimensions. To test for strength and abrasion resistance, the slotted blocks were pinned to sawbones model tibias, and an oscillating saw used to cut through the slot. A compact 3D printed tibial cutting guide was then designed which fitted to the proximal tibia and allowed varus-valgus, tibial slope and height adjustments. A small laser attached to the guide projected to a target at the ankle. Tests were made on 20 sawbones, and compared with 20 with a standard metal cutting guide. Digitization was used to measure the angles of the cuts. Results. Prior to autoclaving, the mating parts of all parts were congruent, except for Nylon 12 which had processing debris in slots and screw threads. The ABS-M30i shapes became grossly deformed after autoclaving. The other materials experienced only small changes in dimensions without loss of overall shape, but the slot of the Nylon 12 block was stenotic, 1.4 mm compared to 0.9 mm before autoclaving. In saw blade testing, the VeroClear block fractured through the corner of the slot, while the Nylon 12 block deformed due to heating. The Ultem1010 block produced a small amount of debris, but maintained its shape without any structural damage. In the tests of the tibial cutting guide the 3D printed laser-guided tibial cutting guide resulted in a mean absolute error of 1.72°±1.31° and 1.19°±0.93°, for the tibial slope and varus-valgus respectively. For the conventional guides, these values were 3.78°±1.98° and 2.33°±0.98°, respectively. These measurements were found to be statistically significant with p values of 0.004 and 0.001, respectively. Conclusions. Thus far, apart from patient specific cutting guides and trial components, 3D printing has had limited applications in total knee surgery. As cost containment remains prominent, the use of 3D printing to produce standardized instruments may become viable. These instruments would not require pre-op planning such as CT or MRI, yet allow patient-specific angular settings. Our results indicated that Ultem1010 is a promising material, while a novel tibial cutting guide showed higher accuracy than standard, as well as being quicker to use. These initial tests indicated the viability of 3D printed instruments, but further work will include design and evaluation of the other cutting guides, manufacturing logistics such as in-house or company- based, and economics

A comparative study on CT- and MRI-based patient specific matched guides (PSG) from the same manufacturer for the implantation of total knee arthroplasty (TKA) has not been undertaken. A total of 64 knees operated with CT based PSG was divided into two groups, with (n=32, CT. HK. ) or without (n=32, CT. NA. ) a history of a knee operation, and matched with a control group operated with MRI based PSG(n=64). Alignment of the biomechanical axis of the leg (HKA angle) and accuracy of individual implant alignment were measured on digital long-standing AP and sagittal radiographs. HKA and implant angles <3° deviation of the preoperative planned alignment were defined as correct. Peroperative implant size, OR time (min) and blood loss (ml) were compared. The average HKA angle in the CT. HK. group (177.0, 170.5 to 181.5, p=0.016) and mean varus-valgus alignment of the tibia component in the MRI group (90.6, 85.6 to 94.1, p=0.003) were statistically significant different. None of the outcome on the frontal femoral and lateral tibial component were statistically significant different. Percentage <3° deviation of the preoperative planned femoral flexion-extension alignment was better in the MRI group (84%, p=0.002), compared to the CT. HK. and CT. NA. group (respectively 30% and 42%). Average operation time was statistically significant shorter in favour of the MRI group (53.1, 34 to 80, p≤0.00), compared to the CT. HK. (70.8, 44 to 114) and CT. NA. group (59.2, 41 to 78). There is discrepancy between CT and MRI based PSG from the same manufacture because of patients who were not suitable for MRI due to history of a knee operation in the past. Whether these differences are clinically relevant is questionable. Future research needs to emphasise whether one of these two modalities, MRI or CT is superior compared to the other

Anatomic and accurate placement of components is a primary goal in all arthroplasty procedures. Unique to total shoulder arthroplasty, challenging glenoid exposure and osteoarthritic glenoid deformity offer significant challenges and impediments to this goal. Despite thorough pre-operative planning strategies and contemporary cannulated pin-based shoulder systems, it is often times still difficult to accurately aim the guide pin to the medial border of the scapula when the deformity is substantial or exposure is difficult. Even small errors in guide pin position can result in problems with final component version, inclination and glenoid vault perforation. In addition, a malpositioned glenoid component has been shown to have a negative impact on implant longevity and clinical performance. Image-based patient specific instrumentation has been available in the lower extremity for nearly a decade with reliable results. The application of similar technology in the shoulder has demonstrated reliable positioning of the guide pin to a pre-operative plan with subsequent accurate placement of the glenoid component. This surgical demonstration will feature one of the currently available CT-based patient specific glenoid guides using a standard deltopectoral approach

Background. Surgeons are waiting for a hassle free, time saving, precise and accurate guide for hip arthroplasty. Industry are waiting for instruments to reduce manufacturing costs associated with washing, assembling, sterilization and transportation. Patient specific / custom made surgical guides may deliver these goals but current systems have had limited assessments. We comprehensively assessed a new guiding system for the acetabular component of hip replacement, “Bullseye”. Methods. Planning. We used either Computer Tomography (CT) (n=22) or Magnetic Resonance (MR) (n=6) imaging to plan the position of acetabular components into 28 acetabulums of cadavers (n=12) and dry bone models (n=16). 10 of the dry bone models had complex deformities (crowe 4 hip dysplasia or Paprosky 3A defects). Surgical positioning. Patient specific “Bullseye” guides were manufactured using 3D printing and standard instruments were used to ream the acetabulum, guided by Bullseye, and position cup components. Post surgery. The pelvises underwent CT scanning after implantation of acetabular cups. 3D software measured the “radiographic” (as opposed to operative or anatomic) cup inclination and version angles using the anterior pelvic plane as a reference. Achieved position was compared to the plan. Statistics. We used Bland Altman plots to quantify the strength of the agreement between the planned and achieved cup orientations in terms of fixed bias, correlation coefficient and 2 standard deviation limits of agreement. Results. Measurement of the cup position angles with 3D CT after implantation with the Bullseye hip instruments showed a median (Interquartile range) difference in degrees between planned and achieved position of 2.5 (1–6) for inclination and 8 (3–10) for version. The use of CT or MR imaging for planning produced similar results. Bland Altman plots for cup inclination and version angles respectively, showed a fixed bias of +3 and +6 degrees; in other words the guide increased the planned cup angles by consistent 3 and 7 degrees on average. The estimated bias, was 3.9 and 7 degrees respectively. The 95% (1.96 SD) limits of agreement were 7 and 10 respectively. Discussion. This robust assessment, involving the use of 3D CT, of the Bullseye hip instruments system showed good early results with 95% limits of agreement between planned and achieved cup angles of 7.3 and 10 degrees for inclination and version respectively. In other words, the Bullseye instruments can achieve better cup position than any published study of conventional techniques. Or put another way, a cup planned to be at the centre of Lewinnek's safe zone of acetabular cup position (inclination range between 30 and 50 degrees; version range between 5 and 25 degrees) would be achieved in 95% of cases. This could be improved further by adjusting for the fixed bias and choosing cases with simple bony anatomy. Conclusion. The Bullseye hip instruments have the potential to reduce the wide variation in the positioning of acetabular components during hip arthroplasty. It is now ready for a clinical evaluation

Introduction. Patient-specific cutting guides entered into clinical practice few years ago, first introduced in total knee replacement and recently also for other joint replacements. Advantages claimed are improving accuracy and repeatability in implant placement. New patient-specific guides to perform an accurate femoral neck resection and provide a precise alignment reference for acetabular reaming in total hip arthroplasty (THA) were recently developed by Medacta International: MyHip Technology. To date femoral guides can be designed for both anterior and posterior approaches, whereas acetabular guides are available only for posterior approach. Evaluation of the repeatability and reproducibility of MyHip guides placement on cadavers is performed using a navigation system. Accuracy of femoral MyHip guides is evaluated also through one author's clinical experience (RP). Materials and Methods. During each cadaveric session one body (2 hips) was available. A pre-operative CT scan has been obtained and used in order to create the 3D bone model of the pelvis and proximal femurs. Afterwards, a surgical planning for THA has been performed for each case, and, once it was approved by the surgeons, the designed patient-specific blocks were made. Intraobserver and interobserver agreement in positioning the guides was assessed getting measures of femoral head resection height (mm), femoral head plane inclination/anteversion (°) and acetabular reaming axis orientation (°). 9 surgeons, through 2 cadaveric sessions, positioned each guide, removed it and re-positioned it 5 times alternatively. The system is judged as accurate if all measures differ less than 3mm and 5°for lengths and angles respectively from the average among all the acquisitions. Clinical experience includes 68 THA which were performed between March 2014 and April 2015. Anterior femoral MyHip guides were used for the femoral head resection, while the acetabular side was prepared using the standard metal instrumentation for minimally invasive anterior approach. Intra-operative complications, as well post-operative leg length difference and implant positioning are assessed. Results. During cadaveric sessions, all measures taken meet the acceptance criteria with the exception of two measures, which are −5,98° and −5,57°, in femoral head plane anteversion and inclination respectively with femoral anterior guides. Looking at intraobserver variation, MyHip Femoral anterior guide positioning average deviation was between −0.91 mm and 1.44 mm (resection height), −1.25° and 1.41° (anteversion), and −0.85° and 0.82° (inclination); MyHip Femoral posterior guide positioning average deviation was between −0.47 mm and 0.67 mm (resection height), −1.33° and 1.50° (anteversion), −0.66° and 1.50° (inclination); MyHip Acetabular posterior guide had an average z-axis deviation from the mean value between −0.91° and 0.91°. All surgeries were successfully performed. The surgeon feels a good fitting and stability of the guide during each surgery. A preliminary analysis suggests optimal outcomes in terms of accurate prosthetic component positioning and reduction of occurrence of leg length inequality. Conclusion. Cadaveric sessions show intraobserver and intraobserver agreement, demonstrating reproducibility and repeatability in placement of MyHip patient specific cutting guides. Clinical experience confirms the advantages claimed by this technique, suggesting a possible reduction of complications usually linked to implant malpositioning, such as wear, impingement, risk of luxation

Introduction. Patient specific surgical guide (PSSG) is a relatively new technique for accurate total knee arthroplasty (TKA), and there are many reports supporting PSSG can reduce the rate of outlier in the coronal plane. We began to use PSSG provided by Biomet (Signature®) and have reported the same results. Before using Signature, we performed TKA by modified gap technique (parallel cut technique) to get the well balanced flexion gap. Signature is the one of the measured resection technique using the anatomical landmarks as reference points on the images of CT or MR taken before surgery. We usually measure the center gap width and gap balance during operation with the special device “knee balancer”(Fig. 1) that can be used on patella reposition. After cutting all of the bone with Signature, gap balance in the extension position was very good but the gap balance was shown slight lateral opening in the 90 degrees flexion position. So we have changed the surgical procedure. We use Signature for cutting only distal femur and proximal tibia to get extension gap and apply the modified gap technique to decide the rotation of the femoral component (Signature with modified gap technique). The purpose of this study is to compare the gap balance between the two techniques. Materials & Methods. From November, 2012 through March, 2014, 50 CR type TKA (Vanguard Knee®, Biomet) in osteoarthritis patients were performed using Signature. 25 TKA were performed using only Signature (group S) and other 25 TKA were done using Signature with modified gap technique (group SG). After all osteotomies of femur and tibia were completed, applying femoral trial, center gap width and gap balance (plus means lateral opening angle) were measured using knee balancer with respect to 30 degrees of the knee flexion angle from zero to 120 degrees (Fig. 2). Results. From knee flexion angle 0 to 120 degrees, gap width was 10.8, 11.9, 11.3, 11, 2 10.8mm in group S, 11.9, 12.6, 11.9, 12.0, 11.8mm in group SG, the range of the gap width was small, 1.1mm and 0.8mm. Gap balance was 0.4, 0.6, 1.0, 2.6, 3.6 degrees in group S and 0.1, 0.1, 0.5, 0.6, 2.6 degrees in group SG. Discussion. With both techniques, Signature and Signature with gap technique, center gap width stayed constant. When it comes to gap balance, in Signature with gap technique group, gap balance were good and constant in knee flexion angle from zero to 90 degrees. But in Signature group, the more flexion angle increased, the more lateral opening angle enlarged. So Signature with gap technique is better than only Signature to get good gap balances during knee movement

Accurate implant alignment, prolonged operative times, array pin site infection and intra-operative fracture risk with computer assisted knee arthroplasty is well documented. This study compares the accuracy and cost-effectiveness of the pre- operative MRI based Signature custom made guides (Biomet) to intra-operative computer navigation (BrainLab Knee Unlimited). Twenty patients from a single surgeon's orthopaedic waiting list awaiting primary knee arthroplasty were identified. Patients were contacted and consented for the study and their suitability for MRI examination assessed. An MRI scan of the hip, knee and ankle was performed of the operative side following a set scanning protocol. Following MRI, patient specific femoral and tibial positioning cutting guides were manufactured. Patients then underwent arthroplasty and intra-operative computer navigation was used to measure the accuracy of the custom made, patient specific cutting guides. A cost analysis of the signature system compared with computer navigation was made. Our provisional results show that the accuracy of the pre-operative MRI patient specific femoral and tibial positioning guides was comparable to computer navigation. Pre-operative, patient specific implant positioning cutting guides were as accurate as computer navigation from analysis of our preliminary results. The potential advantages of the MRI based system are accurate pre-operative planning, reduced operating times and avoidance of pin site sepsis. However, further larger studies are required to examine this technique

Osteotomies around the knee are traditionally templated on 2D plain X-rays. Results are often inaccurate and inconsistent and multiplanar osteotomies are hard to perform. The aim of this study is to evaluate the feasibility and accuracy of virtual three-dimensional CT-based planning and correct execution of osteotomies around the knee with the aid of patient specific surgical guides and locking plates. Eight consecutive patients with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation. The osteotomy was fixed with locking plates and screws. Post-operative assessment included planar X-rays, CT-scan and full leg standing X-rays. One three-planar, three bi-planar and four single-plane osteotomies were performed. Maximum weightbearing mechanical femoro-tibial coronal malalignment varied between 7° varus and 14° valgus (mean 7.6°, SD 3.1). Corrective angles varied from 7°–15° (coronal), 0°–13° (sagittal) and 0°–23° (horizontal). The maximum deviation between the planned pre-operative wedge angle and the executed post-operative wedge angle was 1° in the coronal, sagittal and horizontal plane. The desired mechanical femorotibial axis on full-leg standing X-rays was achieved in 6 patients. Two patients were undercorrected by 1° and 2° respectively. Conclusion. 3D planning and guided correction of multi-planar deformity of femur or tibia is a feasible and accurate novel technique

Introduction. Osteotomies around the knee are traditionally templated on 2D plain X-rays. Results are often inaccurate and inconsistent and multiplanar ostetomies are hard to perform. The aim of this study is to evaluate the feasibility and accuracy of virtual three-dimensional CT-based planning and correct execution of osteotomies around the knee with the aid of patient specific surgical guides and locking plates. Methods. Eight consecutive patients with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation. The osteotomy was fixed with locking plates and screws. Post-operative assessment included planar X-rays, CT-scan and full leg standing X-rays. Results. One three-planar, three bi-planar and four single-plane osteotomies were performed. Maximum weightbearing mechanical femoro-tibial coronal malalignment varied between 7° varus and 14° valgus (mean 7.6°, SD 3.1). Corrective angles varied from 7°-15°(coronal), 0°–13°(sagittal) and 0°–23°(horizontal). The maximum deviation between the planned pre-operative wedge angle and the executed post-operative wedge angle was 1° in the coronal, sagittal and horizontal plane. The desired mechanical femorotibial axis on full-leg standing X-rays was achieved in 6 patients. Two patients were undercorrected by 1° and 2° respectively. Conclusion. 3D planning and guided correction of multi-planar deformity of femur or tibia is a feasible and accurate novel technique

Background and Motivation. Accurate placement of glenoid components in reverse and total shoulder arthroplasty has been shown to reduce the risk of implant failure (1, 2, 6). Surgical techniques and literature describe methods to determine favorable positions for implant placement (3, 4, 5) but achieving that position surgically remains a challenge. Placement of glenoid components is faced with the challenge of variable glenoid morphology on which conventional instrumentation does not always provide a reliable reference (6, 7, 8). Limited surgical exposure is another challenge since many anatomic landmarks are not visible to the surgeon to use as spacial reference. Anatomic landmarks and angles can be more reliabily selected on CT scans with 3-dimentional reconstruction (9,10) yet few methods allow for the reproducible translation of these plans to surgery. Navigation has produced better accuracy and lower variability than conventional instrumentation (11), yet its regular usage remains limited, especially in the shoulder. Methods. A patient specific planning and guiding system has been developed for glenoid implant placement of total and reverse shoulder arthoplasty procedures. This method allows for preoperative planning on a patient specific virtual 3D model of the scapula derived from CT images (Figure 1), and guided placement of a pin which which serves as the central axis for determining proper implant position. An initial implant position was presented on the virtual model based on the methods described by the surgical technique of the corresponding procedure. These plans were either approved or adapted to a desired position within the planning software by the surgeons. Using this planned position as input, patient specific surgical guides were created which fit onto the exposed anatomy and guide the drilling of the pin (Figure 1). This method was tested on 14 cadavers, with attention directed to translation of the starting point from the original plan, the ability to reproduce the intended degree of inferior tilt, and the ability to reproduce the glenoid version angle. Results. The ability to reproduce the surgical plan was found to be highly accurate for the 14 cadaveric specimens. Translational accuracy amongst the 14 cadavers was found to be 1.01 ± 0.53 mm, tilt was 0.46 ± 0.53 degrees, and the accuracy of version was found to be 1.16 degrees ± 1.15 degrees. Conclusion. Surgical planning on patient specific virtual bone models and the corresponding surface matched drilling guides for glenoid implant positiong provide surgeons with an accurate method to achieve the desired surgical implant position. The measured accuracy compares favorably to both conventional and navigated techniques

The clinical success and long-term outcomes of total knee arthroplasty (TKA) depend not only on the accuracy of femoral and tibial components positioning, but also on the restoration of a proper mechanical axis (MA). Coronal and rotational mal-alignment may affect significantly the final result of a knee replacement. Patient specific cutting guides and intra-operative Computer-Assisted Surgery (CAS) have recently been introduced as options to improve implant alignment during TKA. The purpose of this study was to compare the alignment accuracy and implant positioning of Patient Matched technique to CAS system in patients with primary TKA. A cohort of 68 consecutive patients who underwent TKA was enrolled for this study: 34 patients received a TKA using CAS system while 34 patients received a TKA using a MRI-based Patient Matched system. Mechanical axis and kinematics were digitally measured pre- and post-operatively in all knees using the intra-operative navigation system but data were blinded for the operating surgeon in the Patient Matched group. A post-operative CT-scan evaluation was performed in all patients to analyse the prosthetic components alignment (coronal, sagittal and axial alignment according to Perth Protocol from CT-scan). CT-scan measurements were used as landmarks as this tool is considered the gold standard. MA, posterior tibial slope (PTS) and femoral component rotation (FCR) in CAS group were compared to data of Patient Matched group. All patients also underwent a clinical evaluation with Knee Society Score (KSS) and Knee injury and Osteoarthritis Outcome Score (KOOS) at 6 and 12 months of follow up. KSS, KOOS and range of motion were comparable in the two groups after surgery. Operative time was significantly shorter in the Patient Matched group. No differences were found regarding complications rate. Mean angles, respectively for CAS and Patient Matched groups, were the following: MA was 1,7° (SD 0,9°) vs 0.8° (SD 2.1°); PTS was 3.1° (SD 0.9°) vs 3.4° (SD 2.1°); FCR was 1.5° (SD 2.2°) vs 1.36° (DS 1.2°). The outcomes of the CT scan evaluation were the following: MA was 1.5° (SD 0.8°) vs 1.0° (DS 1.5°); PTS was 2.3° (SD 0.8°) vs 3.0° (SD 2.6°); FCR was 0.4° (SD 0.8°) vs 0.2° (SD 0.3°). MA was within 3° of neutral alignment in 94% of patients for CAS group and in 97% of knees for Patient Matched group. After a short follow up, there weren't statistically significant differences between CAS and Patient Matched techniques as regards clinical and functional scores. Both the systems achieved the goal of neutral alignment within 3° of varus and valgus. We only observed greater precision for Patient Matched technique in optimizing femoral component rotation. Actually it is unpredictable if this difference may determine long term effects. Patient Matched technique and CAS for TKA surgery will certainly continue to have an impact in the future. Studies are needed to define which technique is better, in terms of long term results, failure rate and cost-effectiveness

Introduction. Regarding TKA, patient specific cutting guides (PSCG), which have the same fitting surface with patient's bones or cartilages and uniquely specify the resection plane by fitting guides with bones, have been developed to assist easy, low cost and accurate surgery. They have already been used clinically in Europe and the USA. However little has been reported on clinical positioning accuracy of PSCG. Generally, the methods of making PSCG can be divided into 3 methods; construct 3D bone models with Magnetic Resonance (MR) images, construct 3D bone models with Computed Tomography (CT) images, and the last is to construct 3D bone models with both MR and CT images. In the present study, PSCG were made based on 3D bone models with CT images, examined the positioning accuracy with fresh-frozen cadavers. Materials and Methods. Two fresh-frozen cadavers with four knees were scanned by CT. Image processing software for 3D design (Mimics Ver. 14, Marialise Inc.) was used to construct 3D bone model by image thresholding. We designed femoral cutting guides and tibial cutting guides by CAD software (NX 5.0, Siemens PLM Software Co.). CT free navigation system (VectorVision Knee, BrainLab, Inc.) was used to measure positioning error. Average absolute value of positioning error for each PSCG was derived. Results. The average absolute value of positioning error in femoral PSCG was 1.5±0.8° for varus/valgus, 2.3±1.9° for extension/flexion, 1.2±1.8 mm for bone resection. The stability of femoral PSCG was satisfactory. The average absolute value of positioning error in tibial PSCG was 4.3±2.5° for varus/valgus, 5.2±3.3° for anterior slope/posterior slope, 2.6±1.1 mm for bone resection. The stability of tibial PSCG was not sufficient. Discussion. PSCG of the present study were made based on CT images, mainly designed to be fit with cortex, keeping away from cartilage or osteophytes. The fitting surfaces of distal femoral PSCG covered anterior femoral cortex. Also, the fitting surface of tibial PSCG fit to anterior medial cortex of horizontal tibial tuberosity. The average absolute value of positioning error by tibial PSCG varied widely. The main cause for this was their contacts with patellar tendon. Lateral sides of PSCG were contacted with patella tendon near the tibial tuberosity, they were pushed medially. Positioning accuracy of the femoral PSCG is thought to be enough for clinical application

Summary Statement. Our data suggest that postoperative component positioning in TKA with PSPG is not consistent with pre-operative software planning. More studies are needed to rule out possible learning curve in this study. Introduction. Patient specific positioning guides (PSPGs) in TKA are based on MRI or CT data. Preoperatively, knee component positions can be visualised in 3-dimensional reconstructed images. Software allows anticipation of component position. From software planning PSPGs are manufactured and those PSPGs represent intra-operative component alignment. To our knowledge, there are no studies comparing pre-operative software planning with post-operative alignment. Aim of this study is to investigate the correlation between pre-operative planning of component positioning and the post-operative achieved alignment with PSPG technique. Patients & Methods. The first 25 TKA (cemented Vanguard® Complete Knee System, Biomet) with PSPG (Signature™ Biomet) performed at Telemark Hospital in 2009–2010 and the first 17 TKA with PSPG performed at Oslo University Hospital in 2010–2011 were included. A postoperative CT scanning and measurement protocol was used (Perth protocol). CT measurements were performed by 2 independent observers and comparative with pre-operative software (Materialise) planning. Component position angles of femur and tibia were measured. Mechanical axis for both femoral and tibial component angles in all planes was defined as zero degrees. Target angle for femoral component in sagittal plane was set to 2,8 degrees flexion on average and for the tibial tray to 3 degrees of posterior slope. Tibial rotation was in most cases obtained by using extra-medullary guide and therefore not included in this study. Results. In respectively coronal, sagittal and axial plane the femoral component angle was on average 1.2° in varus, SD 1.6 (1.7° valgus −4.5° varus), 4.4° in flexion, SD 3.9 (17.3° flexion −1.6° extension) and 0.5° in external rotation, SD 0.1 (2.3° internal rotation −4.3° external rotation). For the tibial component angle the component was on average 0,5° in varus (3.5° valgus −7.3° varus) and 3.7° posterior slope, SD 2.3 (8.8° flexion −2.4° extension). Intra-class correlation (ICC) between the 2 independent observers was for femoral component in coronal, sagittal and axial plane 0.85, 0.93 and 0.63 and tibial component in coronal and sigittal plane 0.94 and 0.95. Discussion/Conclusion. We expected that our measurements would be close to the pre-operative values. Although the mean values of post-operative measurements are close to pre-operative software planning, we found a considerable spread. Possible explanation might be error levels in pre-operative wrong identification of landmarks from MRI and/or different identification of bony landmarks on CT and intra-operative errors. All measurements were performed from the first Signatures performed in both hospitals. An early learning curve might explain some of the outliers. Time between manufacturing date and performed operation was in most cases several months, but less than the advocated 6 months. This time gap can theoretically provide a less proper fit in some cases due to slight change of anatomy in a progressive osteoarthritis. Our data suggest that postoperative positioning is not consistent with preoperative planning. This may be caused by the an early learning curve. It is uncertain whether this inconsistency is of clinical relevance. More data is necessary to prove any benefit of PSPG compared to existing procedures for TKA

Aims

The aim of this study was to investigate differences in pain, range of movement function and satisfaction at three months and one year after total knee arthroplasty (TKA) in patients with an oblique pattern of kinematic graph of the knee and those with a varus pattern.

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.