A primary goal of shoulder arthroplasty is to place the components in anatomic version. However, traditional instrumentation does not accommodate glenoid wear patterns. Therefore, many investigators have attempted to use computer modeling or CT-based algorithms to create custom targeting guides to achieve this goal. There are some recent studies investigating the use of custom guides. Iannotti et al. published in JBJS-American in 2012 on the use of patient specific instrumentation. There were 31 patients included in the study. The authors found that the planning software and patient specific instrumentation were helpful overall, but particularly of benefit in patients with retroversion in excess of 16 degrees. In this group of patients, the mean deviation was 10 degrees in the standard surgical group and 1.2 degrees in the patient specific instrumentation group. Throckmorton presented a study at the AAOS in 2014 on 70 cadaveric shoulders. There was one high volume surgeon (>100 shoulder arthroplasties a year), two middle volume surgeons (20–50 shoulder arthroplasties a year), and two low volume surgeons (less than 20 shoulder arthroplasties per year). Overall, the custom guide was significantly more accurate than standard instrumentation. The custom guides were found to be especially more accurate among specimens with associated glenoid wear. There were no strong trends to indicate consistent differences between high, medium, and low volume surgeons. The authors concluded that custom guides have narrower standard deviation and fewer significant errors than standard instrumentation. Custom guides continue to evolve for use in shoulder arthroplasty including some guides that allow the surgeon to decide intra-operatively between anatomic shoulder arthroplasty and reverse arthroplasty. Additional studies will be necessary to further define the role of patient specific instrumentation in practice

Introduction:. Total knee arthroplasty (TKA) is an effective operation for the management of osteoarthritis of the knee. Conventional technique utilizing manual instrumentation (MI) allows for reproducible and accurate execution of the procedure. The most common techniques make use of intramedullary femoral guides and either extrameduallary or intrameduallary tibial guides. While these methods can achieve excellent results in the majority of patients, those with ipsilateral hardware, post-traumatic deformity or abnormal anatomy may preclude the accurate use of these techniques. Patient-specific instrumentation (PSI) is an alternative innovation for total knee arthroplasty. Utilizing magnetic resonance imaging (MRI) or computed tomography (CT), custom guide blocks are fabricated based on a patient's unique anatomy. This allows for the benefits of computer assisted navigation (CAN) but without the increased operative times or the high learning curve associated with it. Furthermore it allows the use of familiar cutting blocks and guides to check the accuracy of the PSI guide blocks. In this study we sought to evaluate the accuracy of PSI techniques in patients with previous ipsilateral hardware, which would make the use of MI technically challenging and possibly subject to inaccuracy. Methods:. After reviewing our database of 300 PSI total knee arthroplasty patients, 16 patients were identified (10 male, 6 female) using the Zimmer NexGen Patient Specific Instrumentation System. Fourteen patients included in the study had a preexisting total hip arthroplasty on the ipsilateral side, 1 had a preexisting sliding hip screw, and 1 patient had a preexisting cephalomedullary nail. Postoperative mechanical axis alignment measurements were performed using plain long-standing radiographs. The American Knee Society Score was used to evaluate clinical outcomes postoperatively. Results:. Sixteen total knee arthroplasties were performed using PSI, all in the setting of previous ipsilateral hardware placement. The average age at the time of surgery was 72, with patients ranging from 56 to 85 years of age. Eleven of the included knees had a preoperative varus alignment and 5 had valgus alignment. The average value of a deformity identified via the preoperative planning software was 7.85°. The average value of a deformity identified via preoperative radiographs was 10.1°. Average postoperative mechanical axis was 3.1° measured from plain radiographs. Average angle between the femoral mechanical axis and femoral component was 90.0°. The average angle between the tibial mechanical axis and tibial component was 90.6°. The average difference between the femoral mechanical and anatomic axes was 5.9°. The average discrepancy between medial and lateral joint space on an anterior-posterior standing radiograph was 0.4 mm. At an average of 4.5 months follow-up, American Knee Society knee scores show an aggregate average score of 82.94. Conclusion:. Patient specific instrumentation is an innovative technology in TKA that replaces the use of intramedullary femoral guides and either extramedullary or intramedullary tibial guides. This study demonstrates that PSI is capable of producing favorable radiographic and clinical outcomes despite preexisting ipsilateral hardware, which may preclude the use of customary manual instrumentation. We believe PSI is an accurate and effective tool for use in patients with preexisting ipsilateral hardware

INTRODUCTION:. Despite clear clinical advantages Unicompartimetal Knee Replacement still remain an high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how malalignment increases the rate of aseptic failure even more than in TKR. Computer-assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide despite no still proven clinical advantages. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested, even in partial knee reconstruction, as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of the study is to present a prospective study comparing 2 groups of UKR s using either a computer assisted technique or a CT-based Patient Specific Instrumentation. MATERIALS AND METHODS:. Since January 2010, 54 patients undergoing UKR because medial compartment arthritis were enrolled in the study prospectively. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or patient specific instrumentation group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA). In group B (27 knees) the implant (GMK Uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The surgical time and complications were documented in all cases. Six months post-operatively the patients underwent to the same radiological investigation to determine the frontal femoral component angle (FFC), the frontal tibial component angle (FTC), the hip-knee-ankle angle (HKA) and the sagittal orientation (slope) of tibial/femoral components. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients in each group with all 5 parameters within the desired range was calculated. Furthermore the 2 groups were clinically assessed using KSS and Functional score. RESULTS:. There were no differences in the clinical outcome. The mean surgical time was longer in the navigated group of a mean of 5.9 minutes without any statistical differences in complications. The mechanical axes, tibial slope the FTC angle were significantly better aligned in the navigated group. A statistically significant higher number of outliners was seen in the PSI group. The number of implants with all 5 radiological parameters aligned within the desired range was statistically higher in the navigated group. All the implants in the navigated group were correctly aligned in all the planned parameters. Discussion:. To our knowledge this is the first prospective study in literature assessing navigation compared to PSI technique in UKR surgery. Despite a slight not significant longer surgical time in the navigated group, at a short follow-up the results could not demonstrate any clinical differences between the 2 technologies However according to their results the Authors indicate navigation as more helpful in UKR surgery compared to PSI technology in terms of accuracy

Introduction:. Patient specific instrumentation (PSI) is an innovative technology in total knee arthroplasty. With the use of a preoperative MRI or CT scan, custom guide blocks are individually manufactured for each patient. Contrary to other TKA technologies such as computer-assisted surgery, PSI utilizes measured resection technique rather than a primarily ligament balancing technique. This has the potential to negatively affect the operating surgeon's ability to achieve optimal soft tissue balancing, which is especially critical in patients with severe lower extremity malalignment. Despite early research suggesting that PSI is accurate, has a low learning curve, and can reduce OR time, it remains unclear whether a surgeon using PSI can achieve optimal soft tissue balancing using a measured resection technique. The purpose of this study is to evaluate the efficacy of PSI in patients with severe preoperative limb alignment deformities. Methods:. Fifty PSI total knee arthroplasties were performed on 46 patients (21 male, 25 female) using the Zimmer NexGen Patient Specific Instrumentation system. Each patient included in the study had a minimum preoperative deformity of at least 10° varus or valgus measured on preoperative long leg standing radiographs, Zimmer preoperative software or both. Forty-three of the included knees had a varus deformity and 7 had a valgus deformity. Preoperative mechanical axis alignment measurements were obtained using the PSI preoperative planning software and were manually calculated using pre-operative long leg standing radiographs. Postoperative mechanical axis alignment measurements were calculated using plain long leg standing radiographs. The Knee Society Scoring System was used to evaluate clinical and functional outcomes at 1 to 6 months postoperatively. Results:. Average preoperative deformity as calculated with the PSI preoperative planning software and as measured on plain radiographs were 11.5° and 13.3°, respectively. Average postoperative mechanical axis was 3.4° (0.1°–14.4°)-measured from plain radiographs. The average angle between the femoral mechanical axis (FMA) and femoral component was 88.1° (79.3°–93.7°). The average angle between the tibial mechanical axis (TMA) and tibial component was 88.1° (78.4°–90.7°). The average difference between the femoral mechanical and anatomic axes was 6.2° (4.2°–9.1°). The average discrepancy between medial and lateral joint space on an anterior-posterior standing radiograph was 0.1 mm (0–1.9 mm). No patients required soft tissue releases intraoperatively. The American Knee Society criterion showed an aggregate average score of 81.5. Conclusion:. Patient specific instrumentation (PSI) is an innovative technology in TKA utilizing a measured resection technique. It has not been previously established whether or not this technology is effective at restoring optimal soft tissue balance in TKA, particularly in individuals with severe preoperative alignment deformities. This study demonstrates that PSI is capable of producing favorable radiographic and clinical outcomes in a subset of patients with at least 10° of malalignment pre-operatively

Introduction. Patient specific instrumentation (PSI) is an innovative technology in total knee arthroplasty (TKA). With the use of a preoperative MRI or CT scan, custom guide blocks are individually manufactured for each patient. Contrary to other TKA technologies such as computer-assisted surgery, PSI utilises measured resection technique rather than a primarily ligament balancing technique. This has the potential to negatively affect the operating surgeon's ability to achieve optimal soft tissue balancing, which is especially critical in patients with severe lower extremity malalignment. Despite early research suggesting that PSI is accurate, has a low learning curve, and can reduce operating room time, it remains unclear whether a surgeon using PSI can achieve optimal soft tissue balancing using a measured resection technique. The purpose of this study is to evaluate the efficacy of PSI in patients with severe preoperative limb alignment deformities. Methods. Fifty PSI total knee arthroplasties were performed on 46 patients (21 male, 25 female) using the Zimmer NexGen Patient Specific Instrumentation system. Each patient included in the study had a minimum preoperative deformity of at least 10° varus or valgus measured on preoperative long leg standing radiographs, Zimmer preoperative software or both. Forty-three of the included knees had a varus deformity and 7 had a valgus deformity. Preoperative mechanical axis alignment measurements were obtained using the PSI preoperative planning software and were manually calculated using preoperative long leg standing radiographs. Postoperative mechanical axis alignment measurements were calculated using plain long leg standing radiographs. The Knee Society Scoring System was used to evaluate clinical and functional outcomes at 1 to 6 months postoperatively. Results. Average preoperative deformity as calculated with the PSI preoperative planning software and as measured on plain radiographs were 11.5° and 13.3°, respectively. Average postoperative mechanical axis was 3.4° measured from plain radiographs. The average angle between the femoral mechanical axis (FMA) and femoral component, and between the tibial mechanical axis (TMA) and tibial component, was 88.1°. The average difference between the femoral mechanical and anatomic axes was 6.2°. The average discrepancy between medial and lateral joint space on an anterior-posterior standing radiograph was 0.1mm. No patients required soft tissue releases intraoperatively. The American Knee Society criterion showed an aggregate average score of 81.5. Conclusion. Patient specific instrumentation (PSI) is an innovative technology in TKA utilising a measured resection technique. It has not been previously established whether or not this technology is effective at restoring optimal soft tissue balance in TKA, particularly in individuals with severe preoperative alignment deformities. This study demonstrates that PSI is capable of producing favourable radiographic and clinical outcomes in a subset of patients with at least 10° of malalignment pre-operatively. Given the American Knee Society scores as well as the radiographic findings of an average mechanical axis of 3.4° post-operatively, we believe that this technique can achieve comparable results to techniques using intraoperative soft tissue balancing. We believe PSI is an accurate and effective tool for use in patients with severe preoperative angular deformities of the knee

Introduction. Patient Specific Instrumentation (PSI) has the potential to allow surgeons to perform procedures more accurately, at lower cost and faster than conventional instrumentation. However, studies using PSI have failed to convincingly demonstrate any of these benefits clinically. The influence of guide design on the accuracy of placement of PSI has received no attention within the literature. Our experience has suggested that surgeons gain greater benefit from PSI when undertaking procedures they are less familiar with. Lateral unicompartmental knee replacement (UKR) is relatively infrequently performed and may be an example of an operation for which PSI would be of benefit. We aimed to investigate the impact on accuracy of PSI with respect to the area of contact, the nature of the contact (smooth or studded guide surfaces) and the effect of increasing the number of contact points in different planes. Method. A standard anatomy tibial Sawbone was selected for use in the study and a computed tomography scan obtained to facilitate the production of PSI. Nylon PSI guides were printed on the basis of a lateral UKR plan devised by an orthopaedic surgeon. A control PSI guide with similar dimensions to the cutting block of the Oxford Phase 3 UKR tibial guide was produced, contoured to the anterior tibial surface with multiple studs on the tibial contact surface. Variants of this guide were designed to assess the impact of design features on accuracy. These were: a studded guide with a 40% reduction in tibial contact area, a non-studded version of the control guide, the control guide with a shim to provide articular contact, a guide with an extension to allow distal referencing at the ankle and a guide with a distal extension and an articular shim. All guides were designed with an appendage that facilitated direct attachment to a navigation machine (figure 1). 36 volunteers were asked to place each guide on the tibia with reference to a 3D model of the operative plan. The order of placement was varied using a counterbalanced latin square design to limit the impact of the learning effect. The navigation machine recorded deviations from the plan in respect of proximal-distal and medial-lateral translations as well as rotation around all three axes. Statistical analysis was performed on the compound translational and rotational errors for each guide using ANOVA with Bonferroni correction with statistical significance at p<0.05. Results. Contact points in greater than one plane led to a trend for increasing accuracy and precision of PSI guide placement with respect to rotational alignment, this achieved statistical significance relative to the control guide only with the guide that included articular and distal contact points (figure 2). No significant differences were found with respect to translation. Changes in contact area within the same plane and the use of smooth or studded contact points made no significant difference to accuracy. Conclusion. PSI guide design significantly impacts on accuracy of placement. PSI guides for UKR should endeavour to include widely separated reference points in different planes to maximise rotational accuracy

Introduction:. Patient specific instrumentation (PSI) generates customized guides from a magnetic resonance imaging based preoperative plan for use in total knee arthroplasty (TKA). PSI software must be able to accommodate differences in implant design. The purpose of the present study was to determine whether any differences in the accuracy of limb alignment, component alignment, component sizing, or bony resection could be identified in patients undergoing PSI TKA with identical PSI software and one of two different implant systems. Methods:. In this case-control study, two different implant systems from the same manufacturer were evaluated in 37 consecutive PSI TKA (Group 1) and 123 consecutive PSI TKA (Group 2) performed by a single surgeon. A third group (Group 3) consisted of 12 consecutive TKA performed with manual instrumentation and the same implant system as Group 1. Identical software was used to generate a preoperative plan from which planned limb alignment, component alignment, component sizes, and bony resection were determined. Intraoperatively, actual component sizes, bony resection, and recut frequency were determined. Long-standing and lateral radiographs were obtained preoperatively and 4-weeks postoperatively to evaluate limb and component alignment. Results:. Groups were similar with regard to age, gender, BMI, and preoperative alignment. No differences in the accuracy of limb alignment, component alignment, component sizing, or PSI-planned versus actual resection were found between Groups 1 and 2. The rate of recuts required was lower in Group 1 than Group 2 for the proximal tibia (3% vs. 35%; p < 0.05). No differences were found in limb alignment, component alignment, or bony resection between the Groups 1 and 3. Group 1 showed less variation than Group 3 in resection depth of the posterior femur (SD 1.4 mm vs. 2.1 mm) and proximal tibia (SD 1.5 mm vs. 2.3 mm). Discussion:. No discernible differences in the accuracy of limb alignment, component alignment, and component sizing were found between Groups 1 and 2. Group 1 required fewer recuts than Group 2 for the proximal tibia. There may be characteristics of implant design, e.g. the slope of the tibial plateau, that may influence the ability of PSI to accurately determine cut thickness. No differences in limb alignment, component alignment, or bony resection were identified between Groups 1 and 3. Group 1 showed less variability in resection depth than Group 3 in the posterior femur and proximal tibia. This study suggests that PSI can be equally accurate for different implant systems. For a given implant system, PSI shows less variation in resection depth when compared to manual instrumentation

Background. In our pursuit of surgical accuracy and precision we often neglect to evaluate our results objectively. With the use of Computerised Tomography (CT) in pre-operative planning we can use the same technology in order to evaluate surgical accuracy. Hypothesis. The use of Patient Specific Instrumentation (CT based) produces an accurate intra operative guide for precision cutting in knee arthroplasty. Method. A prospective study using Patient Specific Instrumentation (customized cutting blocks) was performed on 35 patients. The small cohort value is due to the high costs of post-operative CT. A CT based software was used to evaluate the pre-operative knee alignment. Surgery was planned and verified on a web based programme with the use of 3D models. Cutting blocks were custom made and used as intra operative guide to make the relevant cuts. Pre and post-operative CT scans were compared for AP and lateral alignment, femoral external rotation and flexion and tibial slope. Knee Society scores were also used to evaluate the clinical outcome. Results. The values for AP and lateral limb alignment, femoral external rotation and flexion were the same as the pre-operative values with no significant deviation (maximum 2 degree difference). The posterior tibial slope was the only value that showed significant deviation from the pre-planned values. Conclusion. There was a significant difference for the posterior tibial slope but otherwise we found no difference in pre and post-operative limb alignment measurements. Pre-operative planning with the use of CT based customised cutting blocks is a reliable and accurate option to obtain optimal alignment and prosthetic orientation in total knee arthroplasty. NO DISCLOSURES

Recent innovations in total ankle replacement (TAR) have led to improvements in implant survivorship, accuracy of component positioning and sizing, and patient outcomes. CT-generated pre-operative plans and cutting guides show promising results in terms of placement enhancement and reproducibility in clinical studies. The purpose of this study was to determine the accuracy of 1) implant sizes used and 2) alignment corrections obtained intraoperatively using the cutting guides provided, compared to what was predicted in the CT generated pre-operative plans.

This is a retrospective study looking at 36 patients who underwent total ankle arthroplasty using a CT generated pre-operative planning system between July 2015 and December 2017. Personalized pre-operative planning data was obtained from the implant company. Two evaluators took measurements of the angle corrected using pre- and post-operative weight bearing ankle AP X-rays. All patients had a minimum three-month follow-up with weightbearing postoperative radiographs. The actual correction calculated from the radiographic assessment was compared with the predicted angles obtained from pre-operative plans. The predicted and predicted alternative component sizes and actual sizes used were also compared. If either a predicted or predicted alternative size was implanted, we considered it to be accurate.

Average age for all patients was 64 years (range 40–83), with a body mass index of 28.2 ± 5.6. All surgeries were performed by two foot and ankle surgeons. The average total surgical time was 110 ± 23 minutes. Pre-operative alignment ranged from 36.7 degrees valgus to 20 degrees varus. Average predicted coronal alignment correction was 0.8 degrees varus ± 9.3 degrees (range, 18.2 degrees valgus to 29 degrees varus) and average correction obtained was 2.1 degrees valgus ± 11.1 degrees. Average post-op alignment was consistently within 5 degrees of neutral. There were no significant differences between the predicted alignments and the postoperative weightbearing alignments. The predicted tibia implant size was accurate in all cases. The predicted sizes were less accurate for talar implants and predicted the actual talar implant size used in 66% of cases. In all cases of predicted talar size mismatch, surgical plans predicted 1 implant size larger than used.

Preliminary analyses of our data is comparable to previous studies looking at similar outcomes. However, our study had higher pre-operative deformities. Despite that, post-op alignments were consistently within 5 degress of neutral with no significant difference between the predicted and actual corrections. Tibial implant sizes are highly accurate while talar implant sizes had a trend of being one size smaller than predicted. Moreover, this effect seems to be more pronounced in the earlier cases likely reflective of increasing surgeon comfort with the implant with each subsequent case. These results confirm that pre-operative cutting guides are indeed helpful in intra-operative implant selection and positioning, however, there is still some room for innovation.

INTRODUCTION

A preoperative planning for accurately predicting the size and alignment of the prosthetic components may allow to perform a precise, efficient and reproducible total knee replacement. The planning can be carried out using as a support digital radiographic images or CT images with three-dimensional reconstruction. Aim of this prospective study is to evaluate and compare the accuracy of two different types of pre-operative planning, in determining the size of the femoral and tibial component in total knee arthroplasty performed with Patient Specific Instrument (PSI). The two compared techniques were: digital radiography and “CT-Based”.

Aims

Accurate placement of the acetabular component during total hip arthroplasty (THA) is an important factor in the success of the procedure. However, the reported accuracy varies greatly and is dependent upon whether free hand or navigated techniques are used. The aim of this study was to assess the accuracy of an instrument system that incorporates 3D printed, patient-specific guides designed to optimise the placement of the acetabular component.

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

The medial opening-wedge high tibial osteotomy (OW-HTO) is an accepted option to treat the isolated medial compartment osteoarthritis (OA) in varus knee. Despite satisfactory outcomes were described in literature, consistent complication rate has been reported and the provided accuracy of coronal alignment correction using conventional HTO techniques falls short. Patient specific instrumentations has been introduced with the aim to reduce complications and to improve the intra-operative accuracy according to the pre-operative plan, which is responsible for the clinical result of the surgery. In this talk, an overview of the clinical results of HTO patient specific instrumentation available in literature will be performed. Moreover, preliminary intra-operative and clinical results of a new customised 3-D printed cutting guide and fixation plate for OW-HTO will be presented

CT-based three-dimensional (3D) pre-operative imaging along with 2D orthogonal sections defined by the plane of the scapula (axial, sagittal and coronal planes) has been demonstrated by many research groups to be a very accurate way to define the bone pathology and alignment/subluxation of the humeral head in relationship to the center line of the scapula or the center of the glenoid fossa. When 3D CT imaging is combined with 3D implant templating the surgeon is best able to define the optimal implant and its location for the desired correction of the bone abnormalities. The use and value of 3D imaging is best when the there is more severe bone pathology and deformity. Transferring the computer-based information of implant location to the surgical site can involve multiple methods. The three methods discussed in the literature to date including use of standard instrumentation in a manner specified by the pre-operative planning, use of single-use patient specific instrumentation and use of reusable patient specific instrumentation. Several cadaver and sawbone studies have demonstrated significant improvement in placement of the glenoid implant with both single use and reusable patient specific instrumentation when compared to use of 2D imaging and standard instrumentation. Randomised clinical trials have also shown that 3D planning and implant templating is very effective in accurate placement of the implant in the desired location using all three types of instrumentation. The optimal use of this technology is dependent upon the severity of the pathology and the experience and preference of the surgeon. With more severe pathology and less surgeon experience 3D pre-operative imaging and templating and use of some level of patient specific instrumentation provides more accurate placement of the glenoid implant

The emergence of patient specific instrumentation has seen an expansion from simple radiographs to plan total knee arthroplasty (TKA) with modern systems using computed tomography (CT) or magnetic resonance imaging scans. Concerns have emerged regarding accuracy of these non-weight bearing modalities to assess true mechanical axis. The aim of our study was to compare coronal alignment on full length standing AP imaging generated by the EOS acquisition system with the CT coronal scout image. Eligible patients underwent unilateral or bilateral primary TKA for osteoarthritis under the care of investigating surgeon between 2017 and 2022, with both EOS X-Ray Imaging Acquisition System and CT scans performed preoperatively. Coronal mechanical alignment was measured on the supine coronal scout CT scan and the standing HKA EOS. Pre-operative lower limb coronal alignment was assessed on 96 knees prior to TKA on the supine coronal scout CT scan and the standing HKA EOS. There were 56 males (56%), and 44 right knees (44%). The mean age was 68 years (range 53-90). The mean coronal alignment was 4.7 degrees (SD 5.3) on CT scan and 4.6 degrees (SD 6.2) on EOS (p=0.70). There was a strong positive correlation of coronal alignment on CT scan and EOS (pearson. 0.927, p=0.001). The mean difference between EOS and CT scan was 0.9 degrees (SD 2.4). Less than 3 degrees variation between measures was observed in 87% of knees. On linear regression for every 1° varus increase in CT HKA alignment, the EOS HKA alignment increased by 0.93° in varus orientation. The model explained 86% of the variability. CT demonstrates excellent reliability for assessing coronal lower limb alignment compared to EOS in osteoarthritic knees. This supports the routine use of CT to plan TKA without further weight bearing imaging in routine cases

Introduction. This is a multi-centre, prospective, observational study of 503 INFINITY fixed bearing total ankle arthroplasties. We report the minimum two-year results of this prosthesis which was introduced to the UK Market in 2014 and is now the most used ankle arthroplasty in the National Joint Registry of England and Wales. Methods. Patients were recruited from 11 centres in the United Kingdom between June 2016 and November 2019. Demographic, radiographic, and functional outcome data (Ankle Osteoarthritis Scale, Manchester Oxford Foot Ankle Questionnaire and Euroquol 5D-5L) were collected preoperatively, at 6 months, 1 year and 2 years and 5 years. The average age was 67.8 (range 23.9 to 88.5) and average BMI 29.3 (18.9 to 48.0). The COFAS grading system was used to stratify deformity. There were 261 (51.9%) COFAS Type 1, 122 (24.2%) COFAS Type 2, 31 (6.2%) COFAS 3 and 89 (17.7%) COFAS type 4. 38 patients (7.6%) presented with inflammatory arthritis. 99 (19.7%) implantations utilised patient specific instrumentation. Complications and reoperations were recorded as adverse events. Radiographs were assessed for lucencies, cysts and/or subsidence. Results. The mean follow up was 34.2 months (range 24–64). 15 patients have died, 8 withdrawn and 3 lost to follow up. 8 implants (1.6%) have been revised. According to the Glazebrook classification there were low grade complications in 6.6%, medium grade in 1.4% and high grade in 1.6%. There have been an additional 13 non revision re-operations (2.6%) at the latest follow up. There was a significant (p < 0.01) improvement across all functional outcome scores at a minimum of 2yr follow up. Discussion and conclusion. This large cohort has shown a low early revision rate and high functional outcomes with a low-profile fixed bearing prosthesis

Aim. To asses the accuracy of total knee replacements performed using CT based patient specific instrumentation by postoperative CT scan. Method. Approval from the Ethics Committee at The University of New South Wales Sydney Australia was granted prior to commencement of this study. 50 patients who had undergone total knee replacement (Evolis, Medacta International) using CT-based patient specific instrumentation (MY KNEE Medacta International) were assessed postoperatively using a CT scan and a validated measurement technique. The mechanical axis of the limb in the coronal plane, the varus/valgus positioning of the femoral component, the varus/valgus positioning of the tibial component, the flexion/extension of the posterior flange of the femoral component and the posterior slope of the tibial base plate were recorded. These results were then compared to each patient's preoperative planning. The percentage of patients found to be within 3 degrees of planned alignment were calculated. This represents the most comprehensive prospective study to utilize CT assessment of postoperative alignment in patient specific instrumentation. All other studies, to our knowledge have utilized scanograms or scout images and not full CT protocol as performed in this study. Results. 96% of patients were within 3 degrees of planned alignment in the coronal plane reproducing the predicted mechanical axis. Predicted coronal plane orientation of the tibial and femoral component was achieved in 100% and 92% of patients, respectively. The flexion/extension of the posterior flange of the femoral component was within 3 degrees in 92% of patients. The planned posterior tibial slope was achieved in 92% of patients. As a result of difficulty in ascertaining the anatomical landmarks during measurement of the rotation of the femoral component, we are currently repeating the measurements using the original 3D software used for preoperative planning, using the same anatomical landmarks. This data will be available at the time of presentation. Conclusion. This study constitutes one of the largest series of patients who have undergone CT assessment following patient specific instrumented knee replacement. We have found that total knee replacement using patient specific instrumentation accurately reproduces preoperative planning in at least 5 out of the 6 parameters measured in this study

Contemporary techniques to perform total knee arthroplasty use either conventional instrumentation with intramedullary and extramedullary referencing or use a computer navigation system that requires insertion of femoral and tibial tracking pins and an intra-operative registration process. Much of the initial enthusiasm for computer navigation in TKA has waned as many of these systems have proved cumbersome, time consuming and expensive with no substantial evidence of a clinical benefit. Patient specific instrumentation is an additional option that is now widely available which seeks to harness some of the accuracy of computer navigation while improving intra-operative surgical efficiency. In 2015 there are now patient specific options available from multiple vendors and these vary in several different ways including: alignment goals; imaging modality; pin guide vs. cutting guide; all plastic vs. metal-plastic composite; and the degree of surgeon input into pre-operative planning. In all systems but one alignment is typically set relative to the mechanical axis; one system uses so-called kinematic alignment. Imaging can be done via CT, MRI, or MRI in conjunction with a hip-knee-ankle radiograph. The guides that are produced are typically made of a plastic material and in some cases are meant only to position pins onto which traditional metal cutting guides are then placed. In some systems the plastic guides come pre-assembled with an integrated metal cutting-guide that allows resection of the distal femur or proximal tibia in one step; in other systems cutting is intended to be carried out through a plastic captured guide. Finally there is wide variability in the degree of surgeon involvement in the pre-operative planning for the guides, ranging from no involvement in the so-called kinematic approach all the way to the ability for surgeons to dictate the depth, location, flexion-extension angle, varus-valgus angle, and rotation in some systems. At this point relatively little comparative data exists to objectively compare one system versus another. Surgeons most likely to find substantial benefit from patient specific instrumentation are those who perform moderate numbers of TKA each year but who have inconsistent surgical scrub teams. For those surgeons, substantial surgical inefficiency can be attributable to the scrub team's unfamiliarity with the complex instrumentation needed for TKA. Patient specific instrumentation can bypass many of those relatively complex instruments and allow the surgeon to complete TKA in a timely and efficient manner. For TKA subspecialists, patient specific instrumentation may have an appeal from a precision standpoint or from an ease-of-room turnover perspective but are unlikely to yield major intra-operative time savings at this point. In the future, combining patient specific instruments with size-specific disposable instruments that are financially and environmentally favorable may make this technology more applicable to even broader groups of surgeons

Introduction. Given the association of osteoarthritis with obesity, the typical patient requiring total knee arthroplasty (TKA) is often obese. Obesity has been shown to negatively influence outcomes following TKA, as it is associated with increased perioperative complications and poorer clinical and functional outcomes. Achieving proper limb alignment can be more difficult in the obese patient, potentially requiring a longer operation compared to non-obese patients. Patient specific instrumentation (PSI), a technique that utilizes MR- or CT-based customized guides for intraoperative cutting block placement, may offer a more efficient alternative to manual instruments for the obese patient. We hypothesize that the additional information provided by a preoperative MRI or CT may allow surgeons to achieve better alignment in less time compared to manual instrumentation. The purpose of this study was to assess whether PSI offers an improved operation length or limb alignment compared to manual instruments for nonmorbidly and morbidly obese patients. Methods. In this retrospective cohort study, we evaluated 77 PSI TKA and 25 manual TKA performed in obese patients (BMI≥30) between February 2013 and May 2015. During this period, all patients underwent PSI TKA unless unable to undergo MR scanning. All cases were performed by a single experienced surgeon and utilized a single implant system (Zimmer Persona™). PSI cases were performed using the MR-based Zimmer Patient Specific Instrumentation system. Tourniquet times were recorded to determine length of operation. Long-standing radiographs were obtained preoperatively and 4-weeks postoperatively to evaluate limb alignment. Cases were subdivided by nonmorbid obesity (30≤BMI<40) and morbid obesity (BMI≥40) to assess the effect of increasing obesity on outcomes. Results. PSI and manual cohorts were similar with regards to age, gender, and preoperative alignment. Tourniquet time was significantly shorter in the PSI group for nonmorbidly obese patients (PSI 49.8 minutes vs manual 58.3 minutes; p=0.005) (Figure 1). Postoperative mechanical axis was similar between groups for both nonmorbidly obese (PSI 1.8° vs manual 2.9°; p=0.338) and morbidly obese patients (PSI 4.0° vs manual 3.6°; p=0.922). Mechanical axis outliers (greater than 3° neutral), though nonsignificant, were fewer in the PSI group for nonmorbidly obese (PSI 21.8% vs manual 35.3%; p=0.318) and morbidly obese patients (PSI 46.1% vs manual 75.0%; p=0.362). Discussion. We found that PSI significantly shortened operation length for nonmorbidly obese patients compared to manual instruments. Obesity is strongly associated with increased perioperative infection rates, as is prolonged operation length. The decreased operation length achieved with PSI in the nonmorbidly obese patient may as a consequence decrease infection rates, though further study is necessary. Though not statistically significant, PSI showed a trend toward decreasing overall mechanical axis outliers for both nonmorbidly obese and morbidly obese patients. The use of patient specific instrumentation compared to manual instruments has been controversial in the literature. However, patient specific instrumentation may be favorable in the obese patient, offering a shorter operation length and possibly improved alignment

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

Accurate glenoid component placement continues to be a challenge. Knowledge that glenoid loosening is affected by malpositioning of the glenoid component has led to the development of patient specific instrumentation (PSI) in an attempt to optimise glenoid positioning. The ideal PSI would be reusable, reliable, cost-effective and robust enough to tolerate the stresses applied by the surgeon in the context of difficult glenohumeral exposure. The VIP system is a CT scan-based PSI with a reusable instrument. The subtle nuances of pre-operative planning will be discussed in a separate short video. The live surgery will incorporate use of the patient specific instrumentation during glenoid placement and the use of a short stemmed fourth generation total shoulder arthroplasty

High tibial osteotomy (HTO) is an effective surgical treatment for isolated medial compartment knee osteoarthritis; however, widespread adoption is limited due to difficulty in achieving the planned correction, and patient dissatisfaction due to soft tissue irritation. A new HTO system – Tailored Osteotomy Knee Alignment (TOKA®, 3D Metal Printing Ltd, Bath, UK) could potentially address these barriers having a custom titanium plate and titanium surgical guides featuring a unique mechanism for precise osteotomy opening as well as saw cutting and drilling guides. The aim of this study was to assess the accuracy of this novel HTO system using cadaveric specimens; a preclinical testing stage ahead of first-in-human surgery according to the ‘IDEAL-D’ framework for device innovation. Local ethics committee approval was obtained. The novel opening wedge HTO procedure was performed on eight cadaver leg specimens. Whole lower limb CT scans pre- and post-operatively provided geometrical assessment quantifying the discrepancy between pre-planned and post-operative measurements for key variables: the gap opening angle and the patient specific surgical instrumentation positioning and rotation - assessed using the implanted plate. The average discrepancy between the pre-operative plan and the post-operative osteotomy correction angle was: 0.0 ± 0.2°. The R2 value for the regression correlation was 0.95. The average error in implant positioning was −0.4 ± 4.3 mm, −2.6 ± 3.4 mm and 3.1 ± 1.7° vertically, horizontally, and rotationally respectively. This novel HTO surgery has greater accuracy and smaller variability in correction angle achieved compared to that reported for conventional or other patient specific methods with published data available. This system could potentially improve the accuracy and reliability of osteotomy correction angles achieved surgically

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

Understanding the long-term effects of total knee arthroplasty (TKA) on joint kinematics is vital to assess the success of the implant design and surgical procedure. However, while in vitro cadaveric studies quantifying post-operative biomechanics primarily reflect joint behaviour immediately after surgery,. 1. in vivo studies comprising of follow-up TKA patients often reflect joint behaviour a few months after surgery. 2. Therefore, the aim of this cadaveric study was to explore the long-term effects of TKA on tibiofemoral kinematics of a donor specimen, who had already undergone bilateral TKA, and compare them to post-operative kinematics reported in the literature. Two fresh-frozen lower limbs from a single donor (male, age: 83yr, ht: 1.83m, wt: 86kg), who had undergone bilateral TKA (Genesis II, Smith&Nephew, Memphis, USA) 19 years prior to his demise, were obtained following ethical approval from the KU Leuven institutional board. The specimens were imaged using computed tomography (CT) and tested in a validated knee simulator. 3. replicating active squatting and varus-valgus laxity tests. Tibiofemoral kinematics were recorded using an optical motion capture system and compared to various studies in the literature using the same implant – experimental studies based on cadaveric specimens (CAD). 1,4. and an artificial specimen (ART). 5. , and a computational study (COM). 6. . Maximum tibial abduction during laxity tests for the left leg (3.54°) was comparable to CAD (3.30°), while the right leg exhibited much larger joint laxity (8.52°). Both specimens exhibited valgus throughout squatting (left=2.03±0.57°, right=5.81±0.19°), with the change in tibial abduction over the range of flexion (left=1.89°, right=0.64°) comparable to literature (CAD=1.28°, COM=2.43°). The left leg was externally rotated (8.00±0.69°), while the right leg internally rotated (−15.35±1.50°), throughout squatting, with the change in tibial rotation over the range of flexion (left=2.61°, right=4.79°) comparable to literature (CAD=5.52°, COM=4.15°). Change in the femoral anteroposterior translation over the range of flexion during squatting for both specimens (left=14.88mm, right=6.76mm) was also comparable to literature (ART=13.40mm, COM=20.20mm). Although TKA was reportedly performed at the same time on both legs of the donor by the same surgeon, there was a stark difference in their post-operative joint kinematics. A larger extent of intraoperative collateral ligament release could be one of the potential reasons for higher post-operative joint laxity in the right leg. Relative changes in post-operative tibiofemoral kinematics over the range of squatting were similar to those reported in the literature. However, differences between absolute magnitudes of joint kinematics obtained in this study and findings from the literature could be attributed to different surgeons performing TKA, with presumable variations in alignment techniques and/or patient specific instrumentation, and the slightly dissimilar ranges of knee flexion during squatting. In conclusion, long-term kinematic effects of TKA quantified using in vitro testing were largely similar to the immediate post-operative kinematics reported in the literature; however, variation in the behaviour of two legs from the same donor suggested that intraoperative surgical alterations might have a greater effect on joint kinematics over time

Introduction. Total knee arthroplasty is effective for the management of osteoarthritis of the knee. Conventional techniques utilizing manual instrumentation (MI) make use of intramedullary femoral guides and either extramedullary or intramedullary tibial guides. While MI techniques can achieve excellent results in the majority of patients, those with ipsilateral hardware, post-traumatic deformity or abnormal anatomy may be technically more challenging, resulting in poorer outcomes. Computer-assisted navigation (CAN) is an alternative that utilizes fixed trackers and anatomic registration points, foregoing the need for intramedullary guides. This technique has been shown to yield excellent results including superior alignment outcomes compared to MI with fewer outliers. However, studies report a high learning curve, increased expenses and increased operative times. As a result, few surgeons are trained and comfortable utilizing CAN. Patient-specific instrumentation is an alternative innovation for total knee arthroplasty. Custom guide blocks are fabricated based on a patient's unique anatomy, allowing for the benefits of CAN but without the increased operative times or the high learning curve. In this study we sought to evaluate the accuracy of PSI techniques in patients with previous ipsilateral hardware of the femur. Methods. After reviewing our database of 300 PSI total knee arthroplasty patients, 16 were identified (10 male, 6 female) using the Zimmer NexGen Patient Specific Instrumentation System. Fourteen patients included in the study had a preexisting total hip arthroplasty on the ipsilateral side [Figure 1], 1 had a sliding hip screw, and 1 patient had a cephalomedullary nail. Postoperative mechanical axis alignment measurements were performed using plain long-standing radiographs [Figure 2]. The American Knee Society Score was used to evaluate clinical outcomes postoperatively. Results. Sixteen total knee arthroplasties were performed using PSI, all in the setting of previous ipsilateral hardware placement. The average age at the time of surgery was 72, with patients ranging from 56 to 85 years of age [Table 1]. 11 of the included knees had a preoperative varus alignment and 5 had valgus alignment. The average value of a deformity identified via the preoperative planning software was 7.9°(1.5°–15.7°). The average value of a deformity identified via preoperative radiographs was 10.1°(2.2°–14.7°). Average postoperative mechanical axis was 3.1° (1°–5.3°) measured from plain radiographs. Average angle between the FMA and femoral component was 90.0° (85.3°–94.1°). The average angle between the TMA and tibial component was 90.6°(87.6°–92.9°). The average difference between the femoral mechanical and anatomic axes was 5.9°(3.4°–7.0°). The average discrepancy between medial and lateral joint space on an anterior-posterior standing radiograph was 0.4mm(0.0mm–1.1mm). At an average of 4.5 months follow-up, American Knee Society knee scores show an aggregate average score of 82.94. Conclusions. Patient specific instrumentation (PSI) is an innovative technology in TKA that replaces the use of intramedullary femoral guides and either extramedullary or intramedullary tibial guides. This study demonstrates that PSI is capable of producing favorable radiographic and clinical outcomes despite preexisting ipsilateral hardware, which may otherwise preclude the use of customary manual instrumentation. We believe PSI is an accurate and effective tool for use in patients with preexisting ipsilateral hardware

The use of Patient Reported Outcome Measures (PROMS) has been critical to the success of total joint arthroplasty (TJA). They have made possible the evaluations of new implants, materials and surgical techniques that have been essential to the development of these technologies. PROMS have had a major impact on the decisions that surgeons make regarding treatment and care of patients. However, there are serious limitations of PROMS. They are useless in the first few weeks after surgery. They provide very little objective functional information to which health care providers can respond in the early, critical post-operative period. PROMS do not objectively measure specific outcome measures (e.g. ROM, distance walked). PROMS are also cumbersome and time consuming to use. Joint specific surface sensors are emerging to allow objective measurements of specific functional outcomes of knee surgery. This allows an examination of the factors that might affect these functional outcomes. The purpose of this study was to examine the relationship of age, gender, BMI and pain following TKA on ROM and activity measured using a joint specific surface sensor. Methods. 40 patients who underwent primary cruciate retaining TKA using the same implant system and patient specific instrumentation (PSI) were followed for 3 weeks with a knee specific surface sensor (TracPatch. tm. ). The device was applied one day following surgery. Standard post-TKA care protocols were used. The ROM and distance walked was measured by the device. The relationship of these outcomes to patients’ age, gender, BMI and pain were examined. Results. All but one patient tolerated the device. This patient had a superficial, transient skin reaction to the adhesive and was not included in the study. Patients under 60 regained more motion and were more active in the first 3 weeks after surgery than patients 60–69 and patients 70+. Gender had no significant impact on ROM or activity for each age group. BMI under 30 had no impact on ROM or activity. BMI over 40 had a significant impact on both ROM and activity. Pain had very little impact on ROM and moderate impact on activity in the first 3 weeks after surgery. Summary. Joint specific sensors are becoming available to provide objective measurements of a joint's function. The knee specific sensors used in this study measured the number of steps taken and ROM in patients who underwent a primary, cruciate retaining TKA. The device was liked and well tolerated by patients. ROM was affected by age and BMI, but not by gender or, to a significant degree, by pain. The device will be useful in focusing therapy on those patients who most need it. Use of the device has the potential of making post-surgical care more effective and cost efficient

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

Introduction & aims. Patient specific instrumentation (PSI) is a useful tool to execute pre-operatively planned surgical cuts and reduce the number of trays in surgery. Debate currently exists around improved accuracy, efficacy and patient outcomes when using PSI cutting guides compared to conventional instruments. Unicompartmental Knee Arthroplasty (UKA) revision to Total Knee Arthroplasty (TKA) represents a complex scenario in which traditional bone landmarks, and patient specific axes that are routinely utilised for component placement may no longer be easily identifiable with either conventional instruments or navigation. PSI guides are uniquely placed to solve this issue by allowing detailed analysis of the patient morphology outside the operating theatre. Here we present a tibia and femur PSI guide for TKA on patients with UKA. Method. Patients undergoing pre-operative planning received a full leg pass CT scan. Images are then segmented and landmarked to generate a patient specific model of the knee. The surgical cuts are planned according to surgeon preference. PSI guide models are planned to give the desired cut, then 3D printed and provided along with a bone model in surgery. PSI-bone and PSI-UKA contact areas are modified to fit the patient anatomy and allow safe placement and removal. The PSI-UKA contact area on the tibia is defined across the UKA tibial tray after the insert has been removed. Further contact is planned on the tibial eminence if it can be accurately segmented in the CT and the anterior superior tibia on the contralateral compartment, see example guide in Figure 1. Contact area on the femur is defined on the superior trochlear groove, native condyle, femur centre and femoral UKA component if it can be accurately segmented in the CT. Surgery was performed with a target of mechanical alignment using OMNI APEX PS implants (Raynham, MA). The guide was planned such that the OMNI cut block could be placed on the securing pins to translate the cut. Component alignment and resections values were calculated by registering the pre-operative bones and component geometries to post-operative CT images. Results. Four UKA to TKA surgeries have been performed using revision PSI guides. The maximum difference from planned to achieved component alignments are: Femoral valgus = 2.4â□°, Tibial varus = 2.5â□°, Femoral internal rotation = 3.6â□°, Femoral flexion = 5.1â□° and tibial slope = 2.9â□°, see boxplot of results in Figure 2. All median values are within 2.5â□° of the planned alignment. A further five cases are to be analysed. Conclusions. A PSI guide designed for UKR to TKR revision surgery has been successfully used in surgery with acceptable errors. A larger study must be performed to determine the reliability and reproducibility of the design and method over a wide range of patient anatomy and UKA imaging flare

Patient specific instrumentation (PSI) for total knee arthroplasty (TKA) may improve component position and sizing. However, little has been reported about the accuracy of the default plan created by the manufacturer. The purpose of the study was to evaluate the reliability of the manufacturer plan and the impact of surgeon's changes on the final accuracy of the cutting guide sizes. The planned sizes of 45 TKAs were prospectively recorded from the in the initial manufacturer's proposal and from the final plan modified after surgeon's evaluation and compared to the actually implanted sizes. The manufacturer's initial proposal differed from the final implant in 20% of the femoral and 51.11% of the tibial components, while the surgeon's plan in 13.33% of the femoral and 26.67% of the tibial components. Surgeon's modifications in the pre-operative were carried out for 11.11% of the femoral components and 51.11% of the tibial ones (p = 0.0299). Appropriate modification occurred in of 88% and 76% of femoral and tibial changes respectively. The surgeon's accuracy to predict the final component size was significantly different from that of the manufacturer and changes on the manufacturer's plan were necessary to get an accurate preoperative plan of the implant sizes. Careful evaluation by an experienced knee surgeon is mandatory when planning TKA with PSI. Collaboration between surgeons and manufacturers may help obtain improved accuracy in PSI size planning

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

Objectives. To compare computer-assisted total knee arthroplasty with the conventional technique in operative time. Materials and Methods. 30 patients with different degrees and forms of knee osteoarthritis were divided into 2 groups. Group 1 (15 patients) had TKA using patient specific instrumentations (PSI). Group 2 (15 patients) had TKA using the conventional technique. Operative time was measured for each patient of each group. Results. In comparison to conventional group, patients in the PSI group had shorter operative time by 24.3 minutes which is statistically significance. Conclusion. PSI technique has advantage over conventional instrumentation as it reduces operative time

A recent proposed modification in surgical technique in total knee arthroplasty (TKA) has been the introduction of patient specific instrumentation or custom cutting guides (CCGs). With CCGs, preoperative three-dimensional imaging is used to manufacture cutting blocks specific to a patient's native anatomy, with proposed benefits including their ease of use; a decrease in operative times and instrument trays and improved cost-efficiency; the ability to preoperative plan component size, alignment, and position; and an improvement in postoperative alignment versus the use of standard instrumentation. However, to date the majority of reports have not confirmed these proposed benefits. Prior studies focusing on cost-efficiency have shown limited benefits in terms of operating and room turnover times, which fail to offset the additional cost of preoperative imaging and fabrication of the CCGs. Furthermore, a number of reports have noted the frequent need for surgeon-directed changes and alterations in alignment intraoperatively, along with errors in the predetermined implant size. The use of CCGs has also failed to improve overall mechanical and component alignment versus standard instrumentation in the majority of investigations. Perhaps most importantly, no investigation has demonstrated CCGs to improve clinical outcomes postoperatively. Therefore, in the absence of proven clinical or radiographic improvements, the continued implementation of CCGs must be questioned

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

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

Patient specific instrumentation (PSI) for elective knee replacements in arthritic knees with severe deformities and in revision scenarios is becoming increasingly popular due to the advantage of restoring the limb axes, improved theatre efficiency and outcomes. Currently available systems use CT scan or MRI for pre-operative templating for design considerations with varied accuracy for sizing of implants. We prospectively evaluated 200 knees in 188 patients with arthritic knees with deformities requiring serial clinical assessment, radiographs and CT scans for PSI templating for TruMatch knee system (DepuySynthes, Leeds, UK). The common indications included severe arthritic deformities, previous limb fractures and in obese limbs with difficult clinical assessment. Surgical procedure was performed on standard lines with the customised cutting blocks. The ‘lead up’ time between the implant request and the operating date was 5 weeks on an average. We compared the pre op CT images and the best fit post-operative x- rays. The sizing accuracy for femur and tibia was 98.93 % and 95.75% respectively. All blocks fitted the femur and tibia. There were no bail outs, no cutting block breakage, 1 patient had residual deformity of 20 degrees, and 1 patient had late infection. The length of hospital stay, economic viability in terms of theatre turnover, less operating time, cost of sterilisation in comparison to conventional knee replacement surgery with other factors being unchanged was also assessed. The projected savings was substantial along with improved geometrical restoration of the knee anatomy. We recommend the use of PSI based on CT scan templating in difficult arthritic knees

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

Background. Virtual planning of shoulder arthroplasty has gained recent popularity. Combined with patients specific instrumentation, several systems have been developed that allow the surgeon to accurately appreciate and correct glenoid deformities in version and inclination. While each virtual software platform utilizes a consistent algorithm for calculating these measurements, it is imperative for the surgeon to recognize any differences that may exist amongst software platforms and characterize any variability. Methods. A case-control study of all CT scans of patients previously pre-operatively planned using MatchPoint SurgiCase® software were uploaded into the BluePrint software. The cohort represents surgical planning for total shoulder arthroplasty and reverse shoulder arthroplasty with varying degrees of glenoid deformity. Glenoid version and inclination will be recorded for each CT scan using both software platforms. Results. A total of 38 patient CT scans previously planned using MatchPoint Surgicase® software were uploaded into the BluePrint software. The mean difference for glenoid version between the two software programs was 2.497° (±1.724°) with no significant differences in measured glenoid version readings between BluePrint and SurgiCase software (p=0.8127). No significant differences were seen in the measured glenoid inclination between the two software programs (p=0.733), with a mean difference for glenoid inclination between the two software programs at 5.150° ± 3.733° (figure 1). A Bland-Altman plot determined the 95% limits of agreement between the two programs at −5.879 to 6.116 degrees of glenoid version and −12.05 to 12.75 degrees of glenoid inclination. There was a significant statistical agreement between the two software programs measuring glenoid version and inclination in relation to glenoid wear position for the centered (p=0.004), posterior (p<0.001, p=0.003), posterior-superior (p<0.001, p<0.001), and superior (p=0.027, p=0.034) positions, respectively. Conclusions. Both BluePrint and SurgiCase software platforms yield similar measurements for glenoid version and glenoid inclination. In the setting of glenoid wear in the posterior, posterior-superior or superior position, measurements of between two surgical platforms are in agreement

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

Treatment of osteoarthritis of the knee remains a challenging problem since the evolution of the disease may be different in each compartment of the knee, as well as the state of the ligaments. Total knee arthroplasty may provide a reliable long-lasting option but do not preserve the bone stock. In another hand, compartmental arthroplasty is a bone and ligament sparing solution to manage limited osteoarthritis of the knee affecting the medial, lateral or the patello-femoral compartment.1, 2, 3. Patient's selection and surgical indication are based on the physical examination and on the radiological analysis including full-length x-rays and stress x-rays. Clinical experience has shown the need for high flexion in patients who have both high flexibility and a desire to perform deep flexion. Additionally the shape differences related to anatomy or the patient expectations after the surgery may also affect the surgeon decision. 4. The limited incision into the extensor mechanism allows a quicker recovery which represents a functional improvement for the patient additionally to the cosmetic result. A dedicated physiotherapy starting on the following day allowing weight bearing exercises protected by crutches and focusing on early mobilization and range of motion combined to a multimodal pain management approach is critical despite the type of individualized solution chosen for the patient knee. 5. Since bony landmarks may be different form a patient to another one as well as anatomical shapes, several tools have been developed in order to provide the surgeons an assisted tool during the surgery adapted to each knee, this include navigation, patient specific instrumentation and robotic surgery

Background. Obtaining accurate alignment in total knee arthroplasty (TKA) remains a concern. Patient specific instrumentation (PSI) created using preoperative 3D modelling was developed to offer surgeons a simplified, reliable, efficient and customised TKA procedure. Methods. In this prospective study, 60 patients who underwent TKA with conventional instrumentation and 71 patients operated on using PSI were followed for 1 year.(Table 1) The primary endpoint was surgical time. Secondary endpoints included the number of instrument trays used, radiographic limb alignment and clinical outcomes. Results. Compared with conventional instrumentation, PSI significantly reduced total surgical time (mean, 8.9 minutes; ±3.3 minutes (standard deviation); p=0.038), OR time (8.6±4.2 minutes; p=0.043), and number of instrument trays (6 trays, p<0.001).(Table 2) Mechanical axis malalignment of the lower limb >3° was observed in 14% of PSI patients versus 29% with conventional instrumentation (p=0.043).(Figure 1) PSI predicted the size of the actual femoral and tibial components used in 85.9% and 78.9% of cases, respectively. There were no differences in VAS pain, EQ-5D and Oxford Knee Scores at 1-year follow-up. Conclusion. PSI improves alignment, surgical and OR time over conventional instrumentation, reduces the number of instruments trays used and results in fewer outliers in overall mechanical alignment in the coronal plane. No advantages in terms of clinical outcome were noticed up to 1 year of follow-up

The most recent Australian registry has a database of 547,407 knee arthroplasties, having added over 52,000 in 2016. Total knee arthroplasties (TKA) comprise 83.8%, revisions (RevTKA) 8.1% and “partials of all types” 8.1%. Since 2003, the percent of TKA has increased from 76.7%, RevTKA has stayed stable and partial replacements have declined from 14.5%. In the last year, however, TKA declined slightly. There is a slightly higher percentage of women (56.1%) undergoing TKA and this has remained very stable since 2003. Revision rates are slightly higher for men. Percentages of the youngest (<55) and oldest (>85) are small and stable. The 75–84 year olds have declined as 55–74 year olds have increased. This represents a gradual shift to earlier TKA surgery. More patella are resurfaced and this is a gradual trend with a cross over in 2010 when half were resurfaced. Computer navigation is progressively more popular and now accounts for almost 30% of cases. Cement fixation is also increasing and accounts for about 65% of cases. Crosslinked polyethylene is gradually replacing non crosslinked and in 2014 was used in 50% of cases. Revisions are performed most commonly for loosening and infection. Revision rates correlate directly with age. Loosening is the most common indication for revision in both genders, but males have a distinctly higher revision rate due to infection. Revision rates are slightly higher in all forms of mobile bearing than fixed bearing. Minimally constrained (cruciate retaining) devices are used in the majority of TKAs. Posterior stabilised implants are in slight decline, having peaked in about 2008–2010. Minimally constrained implants are in slight decline as medial pivot/medial congruent devices have been used more frequently. Revision rates are similar amongst all three implant types: PS implants are revised at a slightly higher rate. When an early Medial Pivot (MP) implant is excluded the newer version has better results. The reasons for revision are similar amongst all 3 groups with slightly higher loosening rates for PS designs. (Could this represent backside wear with older locking mechanisms, surface finish and non crosslinked poly?) The MP designs had slightly higher revision rates for “pain”, which is not recognised as a reasonable indication for revision. Revision rates are steadily higher for TKAs without patella resurfacing over 16 years, but the questions as to whether: i. the surgeries were secondary resurfacings or full revisions or ii. if secondary resurfacings eliminated pain are unknown. The combinations at greatest risk of revision were a posterior stabilised or medial pivot arthroplasty without patellar resurfacing. Cementless fixation leads to a higher revision rate. If age and computer navigation are evaluated in terms of revision rates, young patients with and without computer navigated arthroplasties failed at the highest rates, distinct from patients >65. However, if failure rates due only to loosening are evaluated, then computer navigation leads to a lower revision rate in the <65 group. This has been interpreted as the protective effect of better component position that only shows up in patients who use the arthroplasty more aggressively. Patient specific instrumentation (PSI) or Individual Designed Instrumentation (IDI) were revised at marginally higher rates than conventional instrumentation. Crosslinked polyethylene appears to be superior at 12 years (CRR= 4%) versus non crosslinked polyethylene (CRR>7%). This is the result of fewer failures due to loosening with crosslinked poly. The superiority of crosslinked poly was greater in the younger, more active patient

Accurate implant placement is important to the success of joint replacement surgery. Three dimensional pre-operative planning optimizing the ability to define the anatomy and select the desired implant and its location. Linking this information into implant and patient specific instrumentation has been termed smart instrumentation. Single use instruments contain the patient's topographical boney anatomy and implant information. This same information can be placed within a bone model and a reusable instrument placed onto the bone model can be adjusted to capture the information originally in the planning software. This instrument can then be placed into the surgical site, registered to the bone surfaces and used to modify the bone surfaces to replicate the surgical plan. These concepts, technology and devices have been developed and clinically tested in randomized clinical trials for shoulder arthroplasty

Retroversion, also referred to as posterior wear of the glenoid, can make resurfacing the glenoid challenging. However, careful pre-operative planning with three dimensional CT scanning can allow central placement of the glenoid component through removal of some of the anterior bone to allow contained placement and secure fixation within the glenoid vault. Since the scapula is not a fixed skeletal structure and moves substantially on the chest wall, the actual degree of posterior wear (retroversion) frequently is the result of extraneous biomechanical forces and structures. For example, the degree of kyphosis and shape of the rib cage can have a substantial impact on the relative position of the glenoid surface as it articulates with the humerus. Attempts to totally equalise this through implant augmentation have not, to date, been shown to be effective, and in some cases can be destabilising. Restoration of enough alignment to place the implant centrally can be achieved without need for augmentation even in some very hypoplastic glenoids. The technique for this straight-forward approach will be presented, including pre-surgical planning, in some cases, patient specific instrumentation, with demonstration of functional outcomes

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

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

The final alignment of Patient Specific Instrumentation (PSI) TKA relies on the accuracy and the correct placement of the 3-D moulds, precision of saw cuts, soft tissue balancing and cementing technique. We aimed to compare the predicted alignment between PSI and Articulated Surface Mounted (ASM) computer navigation. Eight consecutive patients underwent knee replacement using MRI based PSI (Zimmer) with planning of 0º femoral and tibial mechanical alignment. After placing the conventional cutting blocks over the pins (placed according to PSI), the predicted alignment of cuts was verified with ASM navigation. PSI technique was used regardless of navigation values and alignment was compared. Good correlation was found for tibial cuts (maximum variation: coronal plane – 1º, sagittal plane – 2º) and femoral cuts in the sagittal plane (maximum variation 2º). However, in two patients the coronal plane variation in femur was > 2º (3º and 4º respectively). Navigation predicted combined final alignment of 5º valgus and 4º valgus in these patients. However, long leg standing x-rays revealed neutral and 1º valgus alignment in those two patients respectively, matching closely with PSI prediction. Final alignment in long-leg standing x-rays were independently reported by a musculoskeletal radiologist. Six knees were in neutral mechanical alignment (including the 2 navigation predicted outliers). The remaining 2 knees had a maximum deviation of 2 degrees from neutral. We conclude that there was overall good correlation between PSI and navigation. Even in cases where navigation predicted more than 3º combined varus/valgus alignment, PSI prediction was more accurate on long leg views

Patient specific instrumentation (PSI) is the latest advancement in total knee arthroplasty (TKA), which claims to improve alignment, simplify the surgical process, forecasts the component size and reduces the operating time. We discuss our experience of preoperative planning using default settings and making changes where necessary. We analysed prospectively collected data in 100 consecutive PSI knee replacements (Zimmer®) performed in our institute during the period February to August 2012. All patients underwent MRI scans of the ipsilateral hip, knee and ankle joints. From the images, Materialise® (Leuven, Belgium) provided 3D model of the knee on which preoperative planning was done using PSI software. All default plans were checked and appropriate changes were made before the senior author approved final plan for preparation of patient specific moulds. We made 636 changes (6.36 changes per knee) preoperatively from the default settings. In only 4% of the patients, the primary cuts needed revision. Thus in 96% of the cases, the primary cuts allowed optimal alignment and gap balancing with appropriate soft tissue release. Our preoperative planning predicted 99% of femoral and 98% of tibial component sizes definitively implanted. Our results show the importance of the surgeon's input in approving preoperative planning with this technique

Introduction. Patients undergoing total knee arthroplasty have expected blood loss during and after surgery. The current literature remains inconclusive in regards to which surgical instrumentation techniques in total knee arthroplasty are effective in minimising peri-operative blood loss. The primary objective of this retrospective review of a prospective randomized cohort study is to compare surgical and patient factors and their influence on blood loss and transfusions rates between one type of Patient Specific Instrumentation (PSI) (SignatureTM), Navigated Computer-Assisted Surgery (CAS) and Conventional Total Knee Arthroplasty (TKA) surgical techniques. Method. 128 matched patients (38 SignatureTM, 44 CAS, 46 Conventional surgeries) were compared. Pre-operative factors were analysed including; age, gender, Body Mass Index (BMI), pre-operative hemoglobin (g/L), International Normalized Ratio (INR), use of anticoagulants and co-morbid bleeding diathesis. Maximal hemoglobin drop were compared on Day 1 to 3, as well as, transfusion requirement. Peri-operative factors were collected including; surgical time, tourniquet time, drain output, insitu drain time, order of tibia or femoral cut and intra-operative loss from suction. Results. No significant differences were found between the three groups on the pre-operative patient demographics examined. The mean Hb pre-operative was 140 for PSI, 135 for CAS and 139 for Conventional. The mean post-operative Hb was 111 for PSI, 104 for CAS and 107 for conventional. Thereby calculating that the mean percentage drop was 21%, 23% and 23% respectively. The difference between Pre-Op Hb and the lowest of the Post-Op Hb readings does not significantly differ between the three groups (p=0.39). A significant difference is seen between the three groups with respect to Day 1 Hb drop (p=0.05). In the study, 4 patients required transfusion due to either hemoglobin <80g/l or clinically symptomatic. The 4 patients were all from the Conventional TKR group. Conclusion. Surgical technique does not appear to influence post-operative blood loss when comparing PSI, CAS and Conventional TKA. This is the first article to compare all three knee arthroplasty systems in a matched patient series. The surgeon's preference of drain use does not appear to influence post-operative blood loss

Introduction. Surgical planning for Patient Specific Instrumentation (PSI) in total knee arthroplasty (TKA) is based on static non-functional imaging (CT or MRI). Component alignment is determined prior to any assessment of clinical soft tissue laxity. This leads to surgical planning where assumptions of correctability of preoperative deformity are false and a need for intraoperative variation or abandonment of the PSI blocks occurs. The aim of this study is to determine whether functional radiology complements pre-surgical planning by identifying non-predictable patient variation in laxity. Method. Pre-operative CT's, standing radiographs and functional radiographs assessing coronal laxity at 20° flexion were collected for 20 patients. Varus/valgus laxity was assessed using the TELOS stress device (TELOS GmbH, Marburg, Germany, see Figure 1). The varus/valgus load was incrementally increased to either a maximum load of 150N or until the patient could not tolerate the discomfort. Radiographs were taken whilst the knee was held in the stressed position. CT scans were segmented and anatomical points landmarked. 2D–3D pose estimations were performed using the femur and tibia against the radiographs to determine knee alignment with each functional radiograph and so characterise the varus/valgus laxity. Results. The mean coronal alignment on CT and standing radiographs were 3.8° varus (SD, 5.6°) and 4.3° varus (SD, 6.7°) respectively. Of these, 5 of the knees were valgus aligned and 15 varus aligned in both standing and CT positions. The varus group had a mean of 5.9° in CT and 6.9° varus standing, while the valgus group had means of 4.4° valgus and 5.4° valgus in standing, indicating a collapse into further coronal malalignment while weightbearing. Each knee in the group had a laxity envelope calculated from the varus and valgus stressed radiographs. In the varus knees, the envelope ranged from 11.0° to 1.0° degree, with a mean of 5.1° (SD, 2.4°). In the valgus knees, the envelope ranged from 10.0° to 5.0° degrees, with a mean of 6.6° (SD, 2.3°), though this difference did not reach statistical significance. Using ±3° of neutral alignment as an indicator of correctable deformity, 7 of the 15 varus knees did not have a correctable deformity, while all of the valgus did. As determined by laxity limits, the CT and standing alignments were not well centered within their functional radiology groups. Specifically, for the valgus knees, 2 were near the valgus limit (lower quartile) of their laxity envelope, while for the varus knees, 9 were near their varus limit (upper quartile) and 2 at the valgus limit. In total, 65% of the knees did not have their standing alignment well centered on their functional laxity imits. Conclusions. Varus/valgus laxity in TKA appears to be subject specific and divorced from static radiological parameters. Surgical planning without reproducible clinical assessments of coronal laxity may not be sufficient to obtain a balanced TKA while avoiding ligament releases. Functional radiographs may be a viable method to individualise and refine the surgical plan in TKA on a per patient basis, incorporating objective information normally only available during the surgery itself. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Background. Patient specific instrumentation (PSI) for total knee replacement (TKR) has demonstrated mixed success in simplifying the operation, reducing its costs, and improving limb alignment. Evaluation of PSI with tools such as radiostereometric analysis (RSA) has been limited, especially for cut-through style guides providing mechanical alignment. The primary goal of the present study was to compare implant migration following TKR using conventional and PSI surgical techniques, with secondary goals to examine whether the use of PSI reduces operative time, instrumentation, and surgical waste. Methods. The study was designed as a prospective, randomized controlled trial of 50 patients, with 25 patients each in the PSI and conventional groups, powered for the RSA analysis. Patients in the PSI group received an MRI and standing 3-foot x-rays to construct patient-specific cut-through surgical guides for the femur and tibia with a mechanical alignment. All patients received the same posterior-stabilized implant, with marker beads inserted in the bone around the implants to enable RSA imaging. Intraoperative variables such as time, number of instrumentation trays used, and mass of surgical waste were recorded. Patients underwent supine RSA exams at multiple time points (2&6 weeks, 3&6 months and yearly) with 6 months data currently available. Migration of the tibial and femoral components was calculated using model-based RSA software. WOMAC, SF-12, EQ5D, and UCLA outcome measures were recorded pre-operatively and post-operatively. Results. There were no demographic differences between groups. One patient in the PSI group was revised for infection, and three patients required manipulation, with no revisions or manipulations in the conventional group. There was no difference in maximum total point motion between groups for the tibia (mean 0.50 vs. 0.50 mm, p = 0.98) or femur (mean 0.46 vs. 0.48 mm, p = 0.87). The PSI group displayed greater tibial posterior tilt (p = 0.048, Fig. 1) and greater femoral anterior tilt (p = 0.01) and valgus rotation (p = 0.04, Fig. 2) than the conventional group, but there were no other differences in migrations. The PSI group required less instrument trays than the conventional group (mean 4.8 vs. 8.1 trays, p < 0.0001), but procedure time was equivalent (mean 79 vs. 74 min, p = 0.06). The PSI group produced less recyclable waste (mean 0.3 vs. 1.4 kg, p < 0.001), but total waste (Fig. 3) was equivalent between groups (mean 10.1 vs. 10.6 kg, p = 0.32). At 6 months there was no difference between groups for SF-12, WOMAC, EQ5D, or UCLA scores. Discussion. At early RSA follow-up, the two groups were broadly similar in implant fixation except for small rotational changes in the tibial and femoral components. The PSI group provided minimal or no advantage over the conventional group for operative time, instrumentation used, or surgical waste produced. The observed increase in manipulations in the PSI group is concerning, and requires additional investigation. Further radiographic and economic analysis is underway to determine if there is any benefit to the use of PSI for TKR during the perioperative and early follow-up period. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Background. Bilateral leg alignment should be equal for preventing leg length discrepancy and diminishing limping in walking. The candidates for total knee arthroplasty (TKA) sometimes image bilateral TKA seems to get completely same shape and alignment of legs. The query that bilateral TKA, staged in a day and by one surgeon, has an advantage to reconcile one side alignment and component setting to another side, was investigated. Materials and methods. This retrospective investigation enrolled 408 knees of 204 patients (74 years old on average) underwent one day TKA and 48 knees of 24 cases (73 years old on average) underwent two days TKA. There were no history of trauma and surgery on both legs and no other obvious features. All components were same (Vanguard PS TKA, Biomet Inc. Warsaw IN). Surgical procedure is single (modified gap technique) with intramedullar rod for the femur and extramedullar system for the tibia without navigation system and patient specific instrumentation (PSI). Postoperative femorotibial angle (FTA), α, β, γ, δ angles were computed and the absolutes of differences between right and left were analyzed. (two sample t test). Results. Differences of postoperative FTA were 2.4 +/− 1.9 deg in one day, and 3.6 +/− 3.9 deg. in two days (p<0.05). Differences of α angle were 1.7 +/− 1.3 deg. in one day TKA and 2.5 +/− 3.4 deg. in two days TKA (p<0.05), β angle were 1.8 +/− 1.6 deg. and 1.7 +/− 1.4 deg. (ns), γ angle were 3.0 +/− 3.9 deg. and 3.0 +/− 2.6 deg. (ns), δ angle were 2.6 +/− 2.2 deg. and 2.7 +/− 2.5 deg. (ns) respectively. Discussion. Large volume surgeons purposely do fine adjustment of coronal alignment during operation even if they employ navigation system or PSI. The only landmark for the adjustment of the femur is impalpable femoral head that makes the adjustment difficult although there are several landmarks for the adjustment of the tibia that makes the adjustment reliable. The substitute method for the femoral adjustment is still inaccurate. Several factors such as more range of motion should be considered in sagittal alignment. The differences are wider in sagittal alignment as a result. In summary, bilateral TKA can reconcile one side alignment to other at coronal femoral alignment

Up until this point in time, total knee replacement implants have relied on standardised sizes and shapes. The design process for the ‘off-the-shelf’ implants has typically involved designing a standard size implant and then scaling the design up and down to provide a series of standard sizes. More recently, some suppliers have paid more attention to providing sizes that meet the particular needs for either women or men, but these implants are largely standard designs with adjustments to the medial to lateral width or the anterior to posterior depth. To design an implant that not only provides the correct size for every patient's knee, but more importantly to provide an implant that duplicated the patient's exact geometry is the goal. A CT scan is obtained of the patient's lower limb. The CT data is converted into a surface model of the knee joint with proprietary software. The surface model is then utilised to create a near exact match of the articular surface in a knee femoral component. The sagittal geometry is preserved for the medial, trochlear and lateral ‘J’ curves with correction for disease as required. The coronal trochlear and condyle geometries are engineered surfaces that respect the laws of knee design for low contact stress. The bone cuts are individualised for each femoral component based on maximising bone preservation and utilising design rules that are based on finite elemental analysis and fatigue testing. The tibial articular surface geometry is derived from the femoral component. Separate medial and lateral inserts are supplied in varying thicknesses that allow precise balancing of the joint. Patient specific instrumentation is supplied with the implant that allows either femur first or tibial first techniques

A feasibility study of the use of an MRI based patient specific knee arthroplasty system within the NHS. Introducing new technologies within a public funded health system can be challenging. We assess the use and potential benefit of customised jigs for knee arthroplasty. Outcomes assessed were safety and accuracy of implantation. Eight knee replacements using custom jigs were compared to 11 conventionally instrumented replacements matched to surgeon and operative day. Parameters measured include tourniquet time; drain output; hospital stay; adjusted change in haemoglobin; complications; and component position on post-operative long-leg alignment films. None of the parameters observed demonstrated a statistically significant difference from the conventional arthroplasty group. No complications were seen in either group. No significant differences were seen in alignment. Our early experiences show that this technology appears safe and allows accurate implantation of the prosthesis. There was a trend for decreased stay and blood loss. The health economic benefits of navigational arthroplasty have been demonstrated in other studies and come from the lack of instrumentation of the intramedullary canal. MRI based patient specific instrumentation is considered technically easier and more convenient than intra-operative navigation. A larger study is planned to assess the health economic implications of adopting this new technology

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 (PSCG) built from imaging of the extremity can improve the accuracy of bone cuts during total knee replacement (TKR). Some reports have suggested that PSCG offer only marginal improvement in the accuracy of alignment and component positioning in TKA. We compared outcomes between TKRs done with PSCG versus standard, intramedullary-based instrumentation. Methods:. Blood loss, duration of surgery, alignment of the mechanical axis of the leg, and implant position on standing, long-leg, and standard lateral digital radiographs were compared between a CT-guided, custom-built TKA implant (n = 50; ConforMIS iTotal, Boston, MA) implanted with PSCG, versus an off-shelf posterior stabilized TKA implanted with standard instrumentation (n = 50; NKII total knee, Zimmer, Warsaw, IN). The fraction of outliers (>3 degrees) was calculated for the two groups. Results:. The mean mechanical axis of iTotal was 181 degrees with a fraction of outliers of 0.2, versus 178 degrees for NKII with fraction of outliers of 0.7. For frontal plane positioning of femoral components, fraction of outliers for iTotal was 0.04, versus 0.6 for NKII. For tibial components, corresponding values were 0.1 and 0.6, respectively. Sagittal plane outliers were 0.2 and 0.9, respectively, for femoral components; and 0.2 and 0.6 for tibial components. Surgery duration was 5 minutes less and blood loss was 100 mL less for iTotal than for intramedullary-aligned NKII. Conclusion:. Patient specific instrumentation and custom-built implants showed a trend toward improved accuracy of alignment, reduction in blood loss and operating time, when compared to standard, off-the-shelf TKA implants with intramedullary alignment, with fewer radiographic outliers. Larger, randomized trials are necessary to evaluate this technology further, but the initial outcomes appear favorable, with no cost disadvantage to the custom-built implant

Total knee arthoplasty (TKA) remains a standard treatment for advanced knee arthritis. The aim of the procedure is to restore function and relieve pain ideally for the rest of patient's life. Patient matched templating (PMT) or patient specific instrumentation (PSI) is a recent development for alignment of TKA components that uses disposable guides. The users of PSI claim it to be the optimum balance of new technology and conventional technique by reducing the complexity of conventional alignment and sizing tools. To assess the clinical and radiological outcome of Primary TKA done with PSI. More than 200 cases of TKA have been done in our unit using PSI and we analysed the radiographic outcome of these cases postoperatively. We also reviewed the clinical outcome of 103 patients with 1 year and 43 patients with 2 year follow-up. Data was collected prospectively: pre-operatively and at 1 year and 2 years post-operatively including Oxford knee score (OKS), WOMAC and American knee society score (AKS). Standard AP and lateral films were done pre-operatively and post-operatively. Mean age was 66 years. There were 56 female and 47 male patients. Mean post-operative angles on standard films were: Alpha = 95.6, Beta = 88.4, Saggittal femur = 3.4 and Saggittal tibia = 90.8. Of the 103 cases with 1 year follow-up, there was significant improvement in all clinical outcome scores. Mean OKS improved from 18 to 39 at 1 year and remained the same at 2 years, WOMAC improved from 40 to 18 in both 1 and 2 years post-op. AKS Total improved from 79 to 173 at 1 year and 170 at 2 years. Performing TKA using PSI is safe and provides good radiological alignment in the coronal and sagittal plane. Significant improvement in outcome scores were seen at one and two year follow up and reached levels that compared favourably with other reported series of TKA outcome from our unit

Introduction. The goal of tibial tray placement in total knee arthroplasty (TKA) is to maximize tibial surface coverage while maintaining proper rotation. Maximizing tibial surface coverage without component overhang reduces the risk of tibial subsidence. Proper tibial rotation avoids excess risk of patellar maltracking, knee instability, inappropriate tibial loading, and ligament imbalance. Different tibial tray designs offer varying potential in optimizing the relationship between tibial surface coverage and rotation. Patient specific instrumentation (PSI) generates customized guides from an MRI- or CT-based preoperative plan for use in TKA. The purpose of the present study was to utilize MRI information, obtained as part of the PSI planning process, to determine, for anatomic, symmetric, and asymmetric tibial tray designs, (1) which tibial tray design achieves maximum coverage, (2) the impact of maximizing coverage on rotation, and (3) the impact of establishing neutral rotation on coverage. Methods. In this prospective comparative study, MR images for 100 consecutive patients were uploaded into Materialise™ PSI software that was used to evaluate characteristics of tibial component placement. Tibial component rotation and surface coverage was analyzed using the preoperative planning software. Anatomic (Persona™), symmetric (NexGen™), and asymmetric (Natural-Knee II™) designs from a single manufacturer (Zimmer™) were evaluated to assess the relationship of tibial coverage and tibial rotation. Tibial surface coverage, defined as the proportion of tibial surface area covered by a given implant, was measured using Adobe Photoshop™ software (Figure 1). Rotation was calculated with respect to the tibial AP axis, which was defined as the line connecting the medial third of the tibial tuberosity and the PCL insertion. Results. When tibial surface coverage was maximized, the anatomic tray compared to the symmetric/asymmetric trays showed significantly higher surface coverage (82.1% vs 80.4/80.1%; p<0.01), significantly less deviation from the AP axis (0.3° vs 3.0/2.4°; p<0.01), and a significantly higher proportion of cases within 5° of the AP axis (97% vs 73/77%). When constraining rotation to the AP axis, the anatomic tray showed significantly higher surface coverage compared to the symmetric/asymmetric trays (80.8% vs 76.3/75.8%; p<0.01). No significant differences were found between symmetric and asymmetric trays. Discussion. We found that the anatomic tibial tray resulted in significantly higher tibial coverage with significantly less deviation from the AP axis compared to the symmetric and asymmetric trays. When rotation was constrained to the AP axis, the anatomic tray resulted in significantly higher tibial coverage than the symmetric and asymmetric trays. Tibial rotation is recognized as an important factor in the success of a total knee replacement. Maximizing coverage with the least compromise in rotation is the goal for tibial tray design. In this study, the anatomic tibia seemed to optimize the relationship between tibial surface coverage and rotation. This study additionally illustrates the way by which advanced preoperative planning tools (ie. MRI/computer reconstructions) allow us to obtain valuable information with regard to implant design

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

Optimal alignment of the acetabular cup component is crucial for good outcome of total hip arthroplasty [THA]. Increased accuracy of implant positioning may improve clinical outcome. To achieve this, patient specific instrumentation was developed. A patient-specific guide manufactured by 3D printing was designed to aid in positioning of the cup component with a pre-operatively defined anteversion and inclination angle. The guide fits perfectly on the acetabular rim. An alignment K-wire in a pre-operatively planned orientation is used as visual reference during cup implantation. Accuracy of the device was tested on 6 cadaveric specimens. During the experiment, cadavers were positioned for a THA procedure using a posterolateral approach. A normal-sized incision was made and approach used as in the conventional surgical procedure. The PSI was subsequently fitted onto the acetabular rim and secured into its unique position due to its patient specific design. The metallic pin was placed in a drill hole of the PSI. Post-operative CT image data of each acetabulum with the placed pin were transferred to Mimics and the 3D model was registered to the pre-operative one. The anteversion and inclination of the placed pin was calculated and compared to the pre-operatively planned orientation. The absolute difference in degrees was evaluated. A secondary test was carried out to assess the error during impaction while observing the alignment K-wire as a visual reference. In a laboratory setting, error during impaction with a visual reference of the K-wire was measured. Deviation from planning showed to be on average 1.04° for anteversion and 2.19° for inclination. By visually aligning the impactor with this alignment K-wire, the surgeon may achieve cup placement as pre-operatively planned. The effect of the visual alignment itself was also evaluated in a separate test-rig showing minimal deviations in the same range. The alignment validation test resulted in an average deviation of 1.2° for inclination and 1.4° for anteversion between the metallic alignment K-wire used as visual reference and the metallic K-wire impacted by the test subjects. The inter-user variability was 0.9° and 0.8° for anteversion and inclination respectively. The intra-user variability was 1.6° and 1.0° for anteversion and inclination respectively. Tests per test subject were conducted in a consecutive manner. We investigated the accuracy of two factors affecting accuracy in the cup insertion with PSI, i.e. accuracies of the errors of bony fitting and cup impaction. Since the accuracy of the major contributing factors to the overall accuracy of PSI for cup insertion with linear visual reference of a metallic K-wire was within the acceptable range of 2 to 3 degrees, we state that the PSI we have designed assists to achieve the preoperatively planned orientation of the cup and as such leads to the reduction of outliers in cup orientation. This acetabular cup orientation guide can transfer the pre-operative plan to the operating room

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

The goal of tibial tray placement in total knee arthroplasty (TKA) is to maximise tibial surface coverage while maintaining proper rotation. Maximising tibial surface coverage without component overhang reduces the risk of tibial subsidence. Proper tibial rotation avoids excess risk of patellar maltracking, knee instability, inappropriate tibial loading, and ligament imbalance. Different tibial tray designs offer varying potential in optimising the relationship between tibial surface coverage and rotation. Patient specific instrumentation (PSI) generates customised guides from an MRI- or CT-based preoperative plan for use in TKA. The purpose of the present study was to utilise MRI information, obtained as part of the PSI planning process, to determine, for anatomic, symmetric, and asymmetric tibial tray designs, (1) which tibial tray design achieves maximum coverage, (2) the impact of maximising coverage on rotation, and (3) the impact of establishing neutral rotation on coverage. MR images for 100 consecutive patients were uploaded into Materialise™ PSI software that was used to evaluate characteristics of tibial component placement. Tibial component rotation and surface coverage was analysed using the preoperative planning software. Anatomic (Persona™), symmetric (NexGen™), and asymmetric (Natural-Knee II™) designs from a single manufacturer (Zimmer™) were evaluated to assess the relationship of tibial coverage and tibial rotation. Tibial surface coverage, defined as the proportion of tibial surface area covered by a given implant, was measured using Adobe Photoshop™ software. Rotation was calculated with respect to the tibial AP axis, which was defined as the line connecting the medial third of the tibial tuberosity and the PCL insertion. When tibial surface coverage was maximised, the anatomic tray compared to the symmetric/asymmetric trays showed significantly higher surface coverage (82.1% vs 80.4/80.1%; p<0.01), significantly less deviation from the AP axis (0.3° vs 3.0/2.4°; p<0.01), and a significantly higher proportion of cases within 5° of the AP axis (97% vs 73/77%). When constraining rotation to the AP axis, the anatomic tray showed significantly higher surface coverage compared to the symmetric/asymmetric trays (80.8% vs 76.3/75.8%; p<0.01). No significant differences were found between symmetric and asymmetric trays. We found that the anatomic tibial tray resulted in significantly higher tibial coverage with significantly less deviation from the AP axis compared to the symmetric and asymmetric trays. When rotation was constrained to the AP axis, the anatomic tray resulted in significantly higher tibial coverage than the symmetric and asymmetric trays. Tibial rotation is recognised as an important factor in the success of a total knee replacement. Maximising coverage with the least compromise in rotation is the goal for tibial tray design. In this study, the anatomic tibia seemed to optimise the relationship between tibial surface coverage and rotation. This study additionally illustrates the way by which advanced preoperative planning tools (ie. MRI/computer reconstructions) allow us to obtain valuable information with regard to implant design

INTRODUCTION. In total knee arthroplasty (TKA), the effectiveness of the mechanical alignment (MA) within 0°±3° has been recently questioned. A novel implantation approach, i.e. the kinematic alignment (KA), emerged recently, this being based on the pre-arthritic lower-limb alignment. In KA, the trans-cylindrical axis is used as the reference, instead of the trans-epicondylar one, for femoral component alignment. This axis is defined as the line passing through the centres of the posterior femoral condyles modeled as cylinders. Recently, patient specific instrumentation (PSI) has been introduced in TKA as an alternative to conventional instrumentation. This provides a tool for preoperative implant planning also via KA. Particularly, KA using PSI seems to be more effective in restoring normal joint kinematics and muscle activity. The purpose of this study was to report preliminarily joint kinematic and electromyography results of two patient groups operated via conventional MA or KA, the latter using PSI. PATIENT AND METHODS. Twenty patients recruited for TKA were implanted with Triathlon® prosthesis (Stryker®-Orthopaedics, Mahwah, NJ-USA). Seventeen patients, eleven operated targeting MA using the convention instrumentation (group A) and six targeting KA (group B) using PSI (Stryker®-Orthopaedics), were assessed at 6 month follow-up clinically via IKSS and biomechanically. Knee kinematics during stair-climbing, chair-rising, and extension-against-gravity were evaluated using three-dimensional mono-planar video-fluoroscopy (CAT® Medical-System, Monterotondo, Italy) synchronised with electromyography (Wave-Wireless, Cometa®, Milan, Italy). Component pose was reconstructed to calculate knee flexion/extension (FE), ad/abduction (AA), internal/external-rotation (IE), together with the rotation of the contact-line (CLR), i.e. line connecting the medial (MCP) and lateral (LCP) tibio-femoral contact points. MCP and LCP antero-posterior translations were calculated and reported in percentage (%) of the tibial base-plate length. RESULTS. Postoperative clinical scores were better in group B. Knee/functional scores were 78±20/80±23 in group A and 91±12/90±15 in group B. AA range was found smaller than 3°, and physiological ranges of FE and IE were found in both groups. From extension to flexion, MCP translations were all anterior of about 13.8±5.6% anterior, 17.0±6.6% posterior and 15.4±6.6.9% posterior in group A, and 13.0±3.4%, 16.6±5.3% and 16.6±5.6% in group B; corresponding values for LCP were all posterior of about 9.5±3.6%, 11.1±4.3% and 8.7±2.6% in group A, and 102±2.1%, 13.7±8.6% and 14.6±9.8% in group B. These resulted in a CLR equal to 8.2°±3.2°, 10.2°±3.7° and 8.8°±5.3° in group A, and 7.3°±3.5°, 12.6°±2.6° and 12.5°±4.2° group B. Much more consistent patterns of motion were observed in group B. A prolonged activation of the vastus medialis and lateralis was observed in group A. DISCUSSION. These preliminary results show that better scores can be expected using PSI via KA. Although not relevant kinematic differences were observed between groups, more consistent patterns were observed in using PSI via KA. Furthermore, the observed less prolonged activation of the knee extensor muscles suggest that a more natural soft tissue balance is experienced in this group. These findings show a good efficacy of KA using PSI in TKA. The clinical/functional analysis of more patients and a longer follow-up are necessary to establish the claimed superiority of the novel approach

Surgical instrumentation for total knee arthroplasty has improved the accuracy, reproducibility and reliability of the procedure. In recent years, minimally invasive surgery introduced instrumentation that was reduced in size to fit within the smaller operative field; with this move the impact and influence of technology became proportionately larger. The introduction of computer navigation is an attempt to improve the surgeon’s visibility in a limited operative field, improve the position of the resection guides, and ultimately the position of the final components. While it may be appealing to rely on computer navigation to perform a TKA, it is not artificial intelligence and does not make any of the surgical decisions. The procedure still is surgeon directed with navigation serving as a tool of confirmation with the potential for improvements in surgical accuracy and reproducibility. The accuracy of TKA has always been dependent upon the surgeon’s judgment, experience, ability to integrate images, utilize pre-operative radiographs, knowledge of anatomic landmarks, knowledge of knee kinematics, and hand eye co-ordination. Recent advances in medical imaging, computer vision and patient specific instrumentation have provided enabling technologies, which in a synergistic manner optimize the accurate performance of the surgery. The successful use of this technology requires that it not replace the surgeon, but support the surgeon with enhanced intra-operative feedback, integration of pre-operative and intra-operative information, and visual dexterity during the procedure. In developing smart tools or robotic systems, the technology must be: safe; accurate; compatible with the operative field in size and shape, as well be able to be sterilized; and must show measurable benefits such as reduced operative time, reduced surgical trauma and improved clinical outcomes. Advocates believe this is attainable and robotic assisted TKA can achieve levels of accuracy, precision and safety not accomplished by computer assisted surgery. Smart instruments and robotic surgery are helping us take the next step into the operating room of the future. The role of robots in the operating room has the potential to increase as technology improves and appropriate applications are defined. Joint replacement arthroplasty may benefit the most due to the need for high precision in placing instruments, aligning the limb and implanting components. In addition, this technology will reduce the number of instruments needed for the procedure potentially further improving efficiency in the operating room. As technology advances, robots may be commonplace in the surgical theater and potentially transform the way total knee arthroplasty is done in the future. Robotic surgery and smart tools are new innovative technologies and it will remain to be seen if history will look on its development as a profound improvement in surgical technique or a bump on the road to something more important

Introduction. Proper femoral component rotation is a crucial factor in successful total knee arthroplasty (TKA). Femoral component rotation using anatomic landmarks has traditionally been established by referencing the transepicondylar axis (TEA), Whiteside's Line (WSL), or the posterior condylar axis (PCA). TEA is thought to best approximate the flexion-axis of the knee, however WSL or PCA are commonly used as surrogates of the TEA in the operating room due to their accessibility. The relationship of these anatomic landmarks has been previously investigated in anatomic and computed tomography based studies. The relatively few knees evaluated have limited the power of these studies. Patient Specific Instrumentation (PSI) utilizing magnetic resonance imaging (MRI) is an emerging technology in total knee replacement. The purpose of this study was to use magnetic resonance imaging based planning software to assess the relationship of WSL and PCA to the TEA and to determine if the relationships were influenced by the magnitude of the pre-operative coronal deformity. Methods. Five hundred sixty total knee replacements were performed in 510 patients utilizing PSI. The Materialize preoperative planning software was utilized to determine the rotational relationships of TEA, WSL, and PCA (Fig 1). The coronal plane deformity of each patient was also evaluated utilizing the MRI-based imaging and planning software. Results. The WSL is externally rotated by 90.36 degrees (SD ±2.3 degrees) compared to the TEA and the PCA is 2.38 degrees (SD ±1.6 degrees) internally rotated compared to the TEA in the overall population (p<0.001). The relationship of WSL to TEA has more variability than the relationship of PCA to TEA. In the overall population only 77% of WSL and 74% of PCA based resection will be within 2 degrees of the TEA. The PCA is more internally rotated in females and in valgus knees (P<0.001) however is not affected by the degree of valgus deformity (p = 0.211). Discussion. Femoral component rotation is determined based on one of three axis options. Classic studies have shown that the TEA is perpendicular to the WSL and the PCA is 3 degrees internally rotated to the TEA. However, there is wide variation in the relationships. Our MRI based evaluation shows that both WSL and PCA approximate the TEA in valgus knees regardless of the degree of deformity. Our study also shows that on average the PCA is 2.38 degrees internally rotated compared to the TEA, not the previously assumed 3 degrees. Our study indicates that the PCA is more internally rotated compared to the TEA in female patients and patients with valgus deformity. Males with varus knees may only require a 2 degree internal rotation correction rather than the historically established 3 degrees. WSL also shows more variability in its relationship to the TEA compared to the PCA. Advanced imaging can assist surgeons in assessing their options for femoral component rotation in TKA. Our data indicates that the relationships of axis options and historical assumptions may need to be reassessed as imaging technology advances

INTRODUCTION. Despite clear clinical advantages Unicompartimetal Knee Replacement (UKR) still remain a high demanding and less forgiving surgical procedure. Different Authors in literature pointed out how in coronal tibial malalignment beyond 3° as well as tibial slope beyond 7° increase the rate of aseptic failure. Likewise, overcorrection in the coronal plain is a well recognised cause of failure because of an overweighting on the controlateral compartment. Furthermore it has been shown how in UKR surgery even using short narrow intramedullary guide this can cause errors in both coronal planes. Computer assisted surgery has been proposed to improve implant positioning in joint replacement surgery with no need of intramedullary guide. Likewise more recently Patient Specific Instrumentation (PSI) has been suggested as a new technology capable of new advantages such as shorter surgical times and lower blood losses maintaining at least the same accuracy. Aim of this prospective study is to present comparing 2 groups of UKRs using either a computer assisted technique or a CT based PSI. MATERIALS AND METHODS. Since January 2010 54 patients undergoing UKR because of medial compartment arthritis were prospectively enrolled in the study. Before surgery patients were alternatively assigned to either computer-assisted alignment (group A) or PSI group (group B). In the group A (27 knees) the implant (Sigma, Depuy Orthopaedics Inc, Warsaw, Indiana, USA) was positioned using a CT-free computer assisted alignment system specifically created for UKR surgery (OrthoKey, Delaware, USA USA). In group B (27knees) the implant (GMK uni, Medacta, Castel San Pietro, Switzerland) was performed using a CT-Based PSI technology (MyKnee, Medacta, Castel San Pietro, Switzerland). In both the groups all the implants were cemented and using always a fixed metal backed tibial component. The duration of surgery and all the complications according to Kim classification were documented in all cases. Six months after surgery each patient had long-leg standing anterior-posterior radiographs and lateral radiographs of the knee. The radiographs were assessed to determine the Frontal Femoral Component angle (FFC), the Frontal Tibial Component angle (FTC), the Hip-Knee-Ankle angle (HKA) and the sagittal orientation (slope) of both tibial and femoral component. The number and percentage of outliners for each parameter was determined. In addition the percentage of patients from each group with all 5 parameters within the desired range was calculated. Furthermore at the latest follow-up the 2 groups were clinically assessed using KSS and Functional score. RESULTS. At the last assessments there were no differences in the clinical outcome. The mean surgical time was longer in the navigated group of a mean of 5.9 minutes without any statistical differences in complications. The mechanical axis, tibial slope the FTC angle were significantly better aligned in the navigated group. A statistically significant higher number of outliners was seen in the PSI group. The number of implants with all 5 radiological parameters aligned within the desired range was statistically higher in the navigated group. All the implants in the navigated group were correctly aligned in all the planned parameters. DISCUSSION. To our knowledge this is the first prospective study in literature assessing navigation compared to PSI technique in UKR surgery. Despite a slight not significant longer surgical time in the navigated group, at a short follow-up the results could not demonstrate any clinical diffences between the 2 technologies However according to their results the Authors indicate navigation as more helpful in UKR surgery compared to PSI technology in terms of accuracy

Aims

This is a multicentre, non-inventor, prospective observational study of 503 INFINITY fixed bearing total ankle arthroplasties (TAAs). We report our early experience, complications, and radiological and functional outcomes.

Aims

Iliac wing (Type I) and iliosacral (Type I/IV) pelvic resections for a primary bone tumour create a large segmental defect in the pelvic ring. The management of this defect is controversial as the surgeon may choose to reconstruct it or not. When no reconstruction is undertaken, the residual ilium collapses back onto the remaining sacrum forming an iliosacral pseudarthrosis. The aim of this study was to evaluate the long-term oncological outcome, complications, and functional outcome after pelvic resection without reconstruction.

The cause of dissatisfaction following total knee arthroplasty (TKA) remains elusive. Much attention has been focused on static mechanical alignment as a basis for surgical success and optimising outcomes. More recently, research on both normal and osteoarthritic knees, as well as kinematically aligned TKAs, has suggested that other specific and dynamic factors may be more important than a generic target of 0 ± 3º of a neutral axis. Consideration of these other variables is necessary to understand ideal targets and move beyond generic results.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):81–3.

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

This review examines the future of total hip arthroplasty, aiming to avoid past mistakes

Mechanical alignment has been a fundamental tenet of total knee arthroplasty (TKA) since modern knee replacement surgery was developed in the 1970s. The objective of mechanical alignment was to infer the greatest biomechanical advantage to the implant to prevent early loosening and failure. Over the last 40 years a great deal of innovation in TKA technology has been focusing on how to more accurately achieve mechanical alignment. Recently the concept of mechanical alignment has been challenged, and other alignment philosophies are being explored with the intention of trying to improve patient outcomes following TKA.

This article examines the evolution of the mechanical alignment concept and whether there are any viable alternatives.

Smart trials are total knee tibial trial liners with load bearing and alignment sensors that will graphically show quantitative compartment load-bearing forces and component track patterns. These values will demonstrate asymmetrical ligament balancing and misalignments with the medial retinaculum temporarily closed. Currently surgeons use feel and visual estimation of imbalance to assess soft-tissue balancing and tracking with the medial retinaculum open, which results in lower medial compartment loads and a wider anteroposterior tibial tracking pattern. The sensor trial will aid the total knee replacement surgeon in performing soft-tissue balancing by providing quantitative visual feedback of changes in forces while performing the releases incrementally. Initial experience using a smart tibial trial is presented.