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

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

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

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