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

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

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

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 & 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

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

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

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

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

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.

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.

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

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. 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

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

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

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.

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

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