Introduction. Today TKR is considered one of the most successful operative procedures in orthopedic surgery. Nevertheless, failure rates of 2 – 10% depending on the length of the study and the design are still reported. This provides evidence for further development in knee arthroplasty. Particularly the oxide ceramics used now in THA show major advantages due to their excellent tribological properties, their significantly reduced third-body wear as well as their high corrosion resistance. A further advantage of ceramic materials is their potential use in patients with metal allergy. Metallic wear induces immunological reactions resulting in hypersensitivity, pain, osteolysis and implant loosening. The purpose of our study was to examine the safety of the tibial component of a novel all-ceramic TKR. Materials and Methods. We tested the tibial components of the primary knee implant BPK-S Integration Ceramic. Both the tibial and the femoral component consist of BIOLOX®delta ceramic The standards ISO 14879-1 and ASTM F1800-07 describe the test set-up for the experimental fatigue strength testing of tibial components from knee implants. We conducted the testing with a significantly increased maximum load of 5,300 N (900 N are required). A final burst strength test was carried out after the fatigue load testing in the same embedding and with the same test set-up. Results. No specimen failed during fatigue load testing. The subsequent post-fatigue burst strength testing showed a maximum strength against fracture of at least 9.7 kN for size 3 and at least 12.1 kN for size 6. Discussion. The good results of the strength testing of the tibial component of the BPK-S Integration Ceramic tibial plateau supported the good initial clinical outcome without any implant specific complications of this knee design. Further clinical studies have to show if this design fulfills the high expectations over long periods of time

Fractures of the prosthetic components after total knee arthroplasty (TKA) are rare but dangerous complications, sometimes difficult to diagnose and to manage. Aim of this study is to evaluate the incidence of component breakage and its treatment in our single institution's experience. We retrospectively review our institution registry. From 605 revision knee arthroplasties since 2000 to 2018, we found 8 cases of component breakage, of these 3 belonged to UKA, and 5 belonged to TKA. The UKA fractures were all on the metal tibial component; while 4 TKA fractures were ascribed to the liner (2 Posterior-Stabilized designs and 2 constrained designs) and only one case was on the femoral component. For every patient a revision procedure was performed, in two cases a tibial tubercle osteotomy was performed, while in one case (where the fracture was of the post cam) an arthroscopy was performed prior to the arthrotomy. All of the UKA fractures were treated with a standard revision implant. As regard the TKA, 2 liner fractures were treated with the only liner exchange, while the other 2 liner fractures and the fracture of the metallic component were treated with total knee revision. No intra- and post-operative complications were found. Component breakage after TKA is a serious complication. Its treatment, always surgical, can hide pitfalls, especially if the timing is not correct; indeed apart from the revision of one or more components, the surgeons must address any issues of management of bone defect and ligamentous stability

Companies manufacturing total knee arthroplasty (TKA) prostheses produce a variety of tibial and femoral components of different dimensions denoted by numbers or letters. Surgeons frequently implant components that are compatible but not of the same size on the femur and tibia. Recent studies suggest that equally sized femoral and tibial components produce better outcomes compared to size-mismatched components. In our study, we aim to explore the relationship between component size and outcome measured by oxford knee score at six weeks and one year following TKA. A cohort of twenty-four patients who underwent TKA and had well-functioning prosthesis were studied. Thirteen (54%) had equally sized TKA components implanted, seventy-four patients (42%) had components that were mismatched by one size, and one (4%) had components that were mismatched by more than one size. The Oxford Knee Score (OKS) obtained preoperatively, at six weeks and one year postoperatively were retrieved from an electronic database. All data were analysed using R software. A significant improvement in pre-operative and one-year postoperative OKS was observed. Patients who received one-size mismatched tibial and femoral components demonstrated a less pronounced improvement in OKS as compared with patients who received equally sized components. When possible, it may be best to utilise equally sized prosthetic tibial and femoral components when performing total knee arthroplasty. Manufacturers may be able to produce better patient outcomes by including prostheses that are between sizes as part of their production line

Abstract. Objective. Up to 20% of patients can remain dissatisfied following TKR. A proportion of TKRs will need early revision with aseptic loosening the most common. The ATTUNE TKR was introduced in 2011 as successor to its predicate design The PFC Sigma (DePuy Synthes, Warsaw, In). However, following reports of early failures of the tibial component there have been ongoing concerns of increased loosening rates with the ATTUNE TKR. In 2017 a redesigned tibial baseplate (S+) was introduced, which included cement pockets and an increased surface roughness to improve cement bonding. Given the concerns of early tibial loosening with the ATTUNE knee system, this study aimed to compare revision rates and those specific to aseptic loosening of the ATTUNE implant in comparison to an established predicate as well as other implant designs used in a high-volume arthroplasty centre. Methods. The Attune TKR was introduced to our unit in December 2011. Prior to this we routinely used a predicate design with an excellent long-term track record (PFC Sigma) which remains in use. In addition, other designs were available and used as per surgeon preference. Using a prospectively maintained database, we identified 10,202 patients who underwent primary cemented TKR at our institution between 01/04/2003–31/03/2022 with a minimum of 1 year follow-up (Mean 8.4years, range 1–20years): 1) 2406 with ATTUNE TKR (of which 557 were S+) 2) 4652 with PFC TKR 3) 3154 with other cemented designs. All implants were cemented using high viscosity cement. The primary outcome measures were all-cause revision, revision for aseptic loosening, and revision for tibial loosening. Kaplan-Meier survival analysis and Cox regression models were used to compare the primary outcomes between groups. Matched cohorts were selected from the ATTUNE subsets (original and S+) and PFC groups using the nearest neighbor method for radiographic analysis. Radiographs were assessed to compare the presence of radiolucent lines in the Attune S+, standard Attune, and PFC implants. Results. At a mean of 8.4 years follow-up, 308 implants underwent revision equating to 3.58 revisions per 1000 implant-years. The lowest risk of revision was noted in the ATTUNE cohort with 2.98 per 1000-implant-years where the PFC and All Other Implant groups were 3.15 and 4.4 respectively. Aseptic loosing was the most common cause for revision across all cemented implants with 76% (65/88) of involving loosening of the tibia. Survival analysis comparing the ATTUNE cohort to the PFC and All Other Cemented Implant cohorts showed no significant differences for: all-cause revision, aseptic loosening, or tibial loosening (p=0.15,0.77,0.47). Radiolucent lines were detected in 4.6%, 5.8%, and 5.0% of the ATTUNE S+, standard ATTUNE, and PFC groups respectively. These differences were not significant. Conclusion. This study represents the largest non-registry review of the original and S+ ATTUNE TKR in comparison to its predicate design as well as other cemented implants. There appears to be no significant increased revision rate for all-cause revision or aseptic loosening. Radiographic analysis also showed no significant difference in peri-implant radiolucency. It appears that concerns of early loosening may be unfounded. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Abstract. Background. Optimal acetabular component position in Total Hip Arthroplasty is vital for avoiding complications such as dislocation, impingement, abductor muscle strength and range of motion. Transverse acetabular ligament (TAL) and posterior labrum have been shown to be a reliable landmark to guide optimum acetabular cup position. There have been reports of iliopsoas impingement caused by both cemented and uncemented acetabular components. Acetabular component mal-positioning and oversizing of acetabular component are associated with iliopsoas impingement. The Psoas fossa (PF) is not a well-regarded landmark to help with Acetabular Component positioning. Our aim was to assess the relationship of the TAL and PF in relation to Acetabular Component positioning. Methods. A total of 12 cadavers were implanted with the an uncemented acetabular component, their position was initially aligned to TAL. Following optimal seating of the acetabular component the distance of the rim of the shell from the PF was noted. The Acetabular component was then repositioned inside the PF to prevent exposure of the rim of the Acetabular component. This study was performed at Smith & Nephew wet lab in Watford. Results. Out of the twelve acetabular components that were implanted parallel to the TAL, all had the acetabular rim very close or outside to the psoas notch with a potential to cause iliopsoas impingement. Alteration of the acetabular component position was necessary in all cadavers to inside the PF to prevent iliopsoas impingement. It was evident that the edge of PF was not aligned with TAL. Conclusion. Optimal acetabular component position is vital to the longevity and outcome following THA. TAL provides a landmark to guide acetabular component position. We feel the PF is a better landmark to allow appropriate positioning of the acetabular component inside bone without exposure of the component rim and thus preventing iliopsoas impingement at the psoas notch. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Introduction. Long term survivorship in Total Knee Arthroplasty is significantly dependent on prosthesis alignment. The aim of this study was to determine, compare and analyse the coronal alignment of the tibial component of a single implant system using 3 different techniques. Method. Retrospective study of cases from a prospectively collected database. Radiological assessment included measurement of the coronal alignment of tibial components of total knee arthroplasties, and its deviation from the mechanical axis. A comparison study of intramedullary, extramedullary and tibial crest alignment methods was performed. Results. 66 consecutive patients (3 groups of 22 each). Mean BMI was 26. The mean angle of deviation from the mechanical axis was significantly lesser (p< 0.05) in the Tibial crest alignment group patients compared to the other 2 groups. Moreover, the number of outliers (+/-3 degrees) were 2 and 4 in the intra and extramedullary group, whereas there were none in the tibial crest group. The inter and intraclass correlation coefficient was 0.8 and 0.9 respectively. Conclusion. The Tibial Crest Alignment Technique is an effective technique to produce consistent results to achieve optimal coronal alignment of the tibial component in TKA, even in patients with high BMI. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. Accurate orientation of the acetabular component during a total hip replacement is critical for optimising patient function, increasing the longevity of components, and reducing the risk of complications. This study aimed to determine the validity of a novel VR platform (AescularVR) in assessing acetabular component orientation in a simulated model used in surgical training. Methods. The AescularVR platform was developed using the HTC Vive® VR system hardware, including wireless trackers attached to the surgical instruments and pelvic sawbone. Following calibration, data on the relative position of both trackers are used to determine the acetabular cup orientation (version and inclination). The acetabular cup was manually implanted across a range of orientations representative of those expected intra-operatively. Simultaneous readings from the Vicon® optical motion capture system were used as the ‘gold standard’ for comparison. Correlation and agreement between these two methods was determined using Bland-Altman plots, Pearson's correlation co-efficient, and linear regression modelling. Results. A total of 55 separate orientation readings were obtained. The mean average difference in acetabular cup version and inclination between the Vicon and VR systems was 3.4° (95% CI: −3–9.9°), and −0.005° (95% CI: −4.5–4.5°) respectively. Strong positive correlations were demonstrated between the Vicon and VR systems in both acetabular cup version (Pearson's R = 0.92, 99% CI: 0.84–0.96, p<0.001), and inclination (Pearson's R = 0.94, 99% CI: 0.88–0.97, p<0.001). Using linear regression modelling, the adjusted R. 2. for acetabular version was 0.84, and 0.88 for acetabular inclination. Conclusion. The results of this study indicate that the AescularVR platform is highly accurate and reliable in determining acetabular component orientation in a simulated environment. The AescularVR platform is an adaptable tracking system, which may be modified for use in a range of simulated surgical training and educational purposes, particularly in orthopaedic surgery. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Purpose. Addressing posterior tibial plateau fractures is increasingly recognized as an important prognostic factor for functional outcome. The treatment of posterior tibial plateau fractures is rather demanding and the implants are still standard, off-the-shelf implants. This emphasizes the need for a more thorough morphological study of the posterior tibial plateau, in order to treat these posterior fractures more adequately. We aimed to demonstrate anatomical variations of the tibia in order to develop better implants. Method. After approval of the ethical committee 22 historically available CT scans of intact left tibia”s were segmented using Mimics (Materialise, Belgium). In order to perform principal component analysis, corresponding meshes are necessary. Mesh correspondence was achieved by deforming one selected source tibia to every other target tibia, through non rigid registration. The non-rigid registration algorithm was based on the algorithm described by Amberg et al (ref). After performing the non-rigid registration, principal component analysis was performed in Matlab (Mathworks, USA). Results. The first 3 components account for 98,1% of the anatomical shape variation of the tibia. The first principal component accounts for 95,4, the second accounts for 1,6% and the third component accounts for the remaining 1,1% of variation. In the first principal component the most marked variation was the length and the shaft width. Shorter tibia”s have a steeper and more angled posterior medial and lateral plateau as where longer tibia”s have a more rounded posterior tibia plateau. On the distal end, the tip of the medial malleolus is more prominent in shorter tibia”s than in longer tibia”s. The orientation of the tibiofibular joint is directed more posteriorly in larger tibias where it is orientated more laterally in smaller tibia”s. The slope of the medial and lateral tibia plateau is not related to the length or width of the plateau. The second principal component shows a relationship between a valgus shaped tibia shaft and its relation to a relatively smaller medial plateau”s compared with straight tibia”s of the same length. Valgus shaped, small tibia shafts have more posteriorly tilted lateral plateau”s compared with straight, broad shafted tibias. The third principal component shows that an angular shaped posterior tibia plateau is related to a more increased anterior bowing. The increase in the posterior tilt is mostly marked in the medial tibia plateau. Conclusion. The majority of tibia shape variations is directly related to the length of the shaft. The clinically known varus and valgus deformations represent only a small percentage of the total variation. Nevertheless, their variation within the second component is large and has a direct relation to the morphology of the tibia plateau. This data coud furthermore be used to improve implant design

Abstract. Objectives. Principal Component Analysis (PCA) is a useful method for analysing human motion data. The objective of this study was to use PCA to quantify the biggest variance in knee kinematics waveforms between a Non-Pathological (NP) group and individuals awaiting High Tibial Osteotomy (HTO) surgery. Methods. Thirty knees (29 participants) who were scheduled for HTO surgery were included in this study. Twenty-eight NP volunteers were recruited into the study. Human motion analysis was performed during level gait using a modified Cleveland marker set. Subjects walked at their self-selected speed for a minimum of 6 successful trials. Knee kinematics were calculated within Visual3D (C-Motion). The first three Principal Components (PCs) of each input variable were selected. Single-component reconstruction was performed alongside representative extremes of each PC to aid interpretation of the biomechanical feature reconstructed by each component. Results. Pre-operatively patient demographics included (age: 50.70 (8.71) years; height: 1.75 (.11) m; body mass: 90.57 (20.17) kg; mTFA: 7.75 (3.72) degrees varus; gait speed: 1.06 (0.23) m/s). The HTO cohort was significantly older and had a higher mass than the NP control participants. For knee kinematics the first three PCs explained 88%, 95% and 89% of the sagittal, frontal, and transverse planes, respectively. The main variances can be explained by sagittal plane magnitude differences, peak swing is associated with toe-off, a reduced knee flexion angle is associated with a longer time spent in stance, pre-HTO remain adducted during stance and pre-HTO patients remain more externally rotated during stance and latter part of swing. Conclusions. This study has introduced PCA in trying to better understand the biomechanical differences between a control group and a cohort with medial knee osteoarthritis varus deformity awaiting HTO. Further analysis will be undertaken using PCA comparing pre- and post-surgery which will be of importance in clinical decision making

Introduction. Acetabular component orientation is an important determinant of outcome following total hip arthroplasty (THA). Although surgeons aim to achieve optimal cup orientation, many studies demonstrate their inability to consistently achieve this. Factors that contribute are pelvic orientation and the surgeon's ability to correctly orient the cup at implantation. The goal of this study was to determine the accuracy with which surgeons can achieve cup orientation angles. Methods. In this in vitro study using a calibrated left and right sawbone hemipelvis model, participants (n=10) were asked to place a cup mounted on its introducer giving different targets. Measurements of cup orientation were made using a stereophotogrammetry protocol to measure radiographic inclination and operative anteversion (OA). A digital inclinometer was used to measure the intra-operative inclination (IOI) which is the angle of the cup introducer relative to the floor. First, the participant stated his or her preferred IOI and OA and positioned the cup accordingly. Second, the participant had to position the cup parallel to the anteversion of the transverse acetabular ligament (TAL). Third, the participant had to position the cup at IOI angles of 35°, 40° and 45°. Fourth, the participant used the mechanical alignment guide (45° of IOI and 30° of OA) to orient the cup. Each task was analysed separately and subgroup analysis included left versus right side and hip surgeons versus non-hip surgeons. Results. For the first task, hip surgeons preferred smaller IOI and larger OA than non-hip surgeons, but there was no significant difference in accuracy between both groups. When aiming for TAL, both surgeon groups performed similar, but accuracy on the non-dominant side was significantly better compared with the dominant side (mean deviation 0.6° SD 2.4 versus −2.6° SD 2.3) (p=0.004). When aiming for a specific IOI target of 35°, 40° or 45°, non-hip surgeons outperformed hip surgeons (mean deviation form target IOI 1.9° SD 2.7 versus −3.1° SD 3.8) (p<0.0001) with less variance (p=0.03). Contrary to version, accuracy on the dominant side was significantly better compared with the non-dominant side (mean deviation −0.4° SD 3.4 versus −2.1° SD 4.8). When using a mechanical guide, surgeons performed similar (0.6° SD 1.2 versus −0.4° SD 2.1 for inclination p=0.11 and −0.5° SD 2.6 versus −1.8° SD 3.3 for version p=0.22) and these values did not differ significantly from the actual IOI and OA of the mechanical guide. When using a mechanical guide, there was no difference in accuracy between the dominant and non-dominant side. Conclusion. There was no difference in accuracy between hip surgeons and non-hip surgeons when they aimed for their preferred IOI and OA or used a mechanical guide. When aiming for a specific IOI target, non-hip surgeons outperformed hip surgeons. Hip surgeons overestimate IOI and underestimate OA, presumably because this helps to achieve the desired radiographic cup orientation. Regarding accuracy, the non-dominant side was better for version and the dominant side for inclination. When aiming for a specific IOI and OA target, using a mechanical guide is significantly better than freehand cup orientation

Objectives. Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted through the patient’s surrounding tissues. Methods. A commercially available impaction tool was modified to assemble components in the laboratory using impactor tips with varying stiffness at different applied energy levels. Springs were mounted below the modular components to represent the patient. The pull-off force of the head from the stem was measured to assess stability, and the displacement of the springs was measured to assess the force transmitted to the patient’s tissues. Results. The pull-off force of the head increased as the stiffness of the impactor tip increased but without increasing the force transmitted through the springs (patient). Increasing the impaction energy increased the pull-off force but also increased the force transmitted through the springs. Conclusions. To limit wear and corrosion, manufacturers should maximize the stiffness of the impactor tool but without damaging the surface of the head. This strategy will maximize the stability of the head on the stem for a given applied energy, without influencing the force transmitted through the patient’s tissues. Current impactor designs already appear to approach this limit. Increasing the applied energy (which is dependent on the mass of the hammer and square of the contact speed) increases the stability of the modular connection but proportionally increases the force transmitted through the patient’s tissues, as well as to the surface of the head, and should be restricted to safe levels. Cite this article: A. Krull, M. M. Morlock, N. E. Bishop. Maximizing the fixation strength of modular components by impaction without tissue damage. Bone Joint Res 2018;7:196–204. DOI: 10.1302/2046-3758.72.BJR-2017-0078.R2

We compared the orientation of the acetabular component obtained by a conventional manual technique with that using five different navigation systems. Three surgeons carried out five implantations of an acetabular component with each navigation system, as well as manually, using an anatomical model. The orientation of the acetabular component, including inclination and anteversion, and its position was determined using a co-ordinate measuring machine. The variation of the orientation of the acetabular component was higher in the conventional group compared with the navigated group. One experienced surgeon took significantly less time for the procedure. However, his placement of the component was no better than that of the less experienced surgeons. Significantly better inclination and anteversion (p < 0.001 for both) were obtained using navigation. These parameters were not significantly different between the surgeons when using the conventional technique (p = 0.966). The use of computer navigation helps a surgeon to orientate the acetabular component with less variation regarding inclination and anteversion

Background. Trabecular metal (TM) cones are designed to fill up major bone defects in total knee arthroplasty. Tibial components can be implanted in combination with a stem, but it is unclear if this is necessary after reconstruction with a TM cone. Implanting a stem may give extra stability, but may also have negative side-effects. Aim of this study was to investigate stability and strain distribution of a tibial plateau reconstruction with a TM cone while the tibal component is implanted with and without a stem, and whether prosthetic stability was influenced by bone mineral density (BMD). Methods. Tibial revision arthroplasties were performed after reconstruction of an AORI 2B bone defect with TM cones. Plateaus were implanted in seven pairs of cadaveric tibiae; of each pair, one was implanted with and the other without stem. All specimens were loaded to one bodyweight alternating between the medial and lateral tibia plateau. Implant-bone micro motions, bone strains, BMD and correlations were measured and/or calculated. Results. Tibial components without a stem showed only more varus tilt (difference in median 0.14 degrees (P<0.05), but this was not considered clinically relevant. Strain distribution did not differ. BMD had only an effect on the anterior/posterior tilt ρ:-0.72 (P<0.01). Conclusions. Tibial components, with or without a stem, which are implanted after reconstruction of major bone defects using TM cones produce very similar biomechanical conditions in terms of stability and strain distribution. Additional stem extension of the tibial component may not be required after reconstruction of major bone defects using TM cones. Level of evidence. IIb. Disclosures. The department of Orthopaedics, University of Groningen, University Medical Center Groningen has received direct funding from the Anna Fonds (Oegstgeest, NL). Zimmer (Warsaw, IN, USA) has provided the instrumentation and tools for this study. The department of Orthopaedics, University of Groningen, University Medical Center Groningen receives research institutional support from InSpine (Schiedam, NL) and Stryker (Kalamazoo, Mich. USA). One of the authors (ALB) will be and has been paid as a consultant by Zimmer (Warsaw, IN, USA) for purposes of education and training in knee arthroplasty

The purpose of this study is to evaluate accuracy of tibia cutting and tibia implantation in UKA which used navigation system for tibia cutting and tibia component implantation, and to evaluate clinical results. We performed 72 UKAs using navigation system from November, 2012. This study of 72 knees included 56 females and 16 males with an average operation age of 74.2 years and an average body mass index (BMI) of 24.8 kg/m2. The diagnosis was osteoarthritis (OA) in 67 knees and osteonecrosis (ON) in 5 knees. The UKA (Oxford partial knee microplasty, Biomet, Warsaw, IN) was used all cases. We evaluated patients clinically using the Japanese orthopaedic association (JOA) score, range of motion (ROM), operation time, the amount of bleeding and complications. Patients were evaluated clinically at preoperation and final follow up in JOA score and ROM. As an radiologic examination, we evaluated preoperative and postoperative lower limb alignment in FTA (femoro-tibial angle) by weightbearing long leg antero-posterior alignment view X-rays. Also we evaluated a tibial component implantation angle by postoperative CT, and tibia cutting angle by intraoperative navigation system. We defined the tibial angle which a tibia functional axis and the tibia component made in coronal plane, also tibial posterior slope angle which a tibia axis and tibia component made in sagittal plane by CT. We measured tibial angle and tibial posterior slope angle by 3D template system. We performed UKA in all cases mini-midvastus approach. At first we performed osteotomy of the proximal medial tibia using CT-Free navigation. At this procedure we performed osteotomy to do re-cut if check did cutting surface in navigation, and there was cutting error (>3°), and then to do check again in navigation. Next we did not use navigation and went the osteotomy of the distal femur with an IM rod and drill guide of microplasty system. And then we performed a trial and decided bearing gap and moved to cementing. At first we went cementing of the tibia component. At this procedure we went to drive implant again if check did implant surface in navigation, and there was implantation error(>3°), and to do check. We checked did tibia cutting, tibia implantation carefully in navigation. In addition, We sterilize a clips and use it came to be in this way possible for the check of the first osteotomy side exactly. ROM was an average of 122.7° of preoperation became an average of 128.2° at final follow up, and JOA score was an average of 50.5 points of preoperation improved an average of 86.6 points at final follow up after UKA. An average of the operation time was 94 minutes, an average of the amount of bleeding was 137.7ml, and complications were one proximal type deep venous thrombosis (DVT) and one pin splinter joining pain by navigation, .Asetic loosening(tibial component) was one case, and this conversed the TKA. In the radiologic evaluation, FTA was an average of 182.1° of preoperation corrected an average of 175.9°after UKA. In other words, an average of 6.2° were corrected by UKA. The tibia component implantation angle was an average of 90.18° in a measurement by the CT after UKA, intoraoperative tibia component implantation angle was an average of 90.32° in a measurement by the navigation system. These two differences did not accept the significant difference at an average of 1.33°.(P=0.5581). Similarly, the posterior slope angle were as follow; average of 5.65°by CT and average of 5.75°by navigation. These two differences did not accept the significant difference at an average of 1.33°. (P=0.6475). Discussion: We performed UKA using navigation and evaluated the implantation accuracy for tibia osteotomy, tibia implantation. They were good alignment with an average of 90.18°, and outliers more than 3° were two cases(2.8%). It will be necessary to examine long-term progress including clinical results complications in future. We are performed UKA now in femur side using PSI(patient specific instruments) and tbia side using Navigation

Background. Finite element (FE) models are frequently used in biomechanics to predict the behaviour of new implant designs. To increase the stability after severe bone loss tibial components with long stems are used in revision total knee replacements (TKR). A clinically reported complication after revision surgery is the occurrence of pain in the stem-end region. The aim of this analysis was the development of a validated FE-model of a fully cemented implant and to evaluate the effect of different tibial stem orientations. Methods. A scanned 4th generation synthetic left tibia (Sawbones) was used to develop the FE-model with a virtually implanted fully cemented tibial component. The 500 N load was applied with medial:lateral compartment distributions of 60:40 and 80:20. Different stem positons were simulated by modifying the resection surface angle posterior to the tibias shaft axis. The results were compared with an experimental study which used strain gauges on Sawbones tibias with an implanted tibial TKR component. The locations of the experimental strain gauges were modelled in the FE study. Results. Similar patterns and magnitudes of the predicted and experimentally measured strains were observed which validated the FE-model. An increase of strain at the most distal gauge locations were measured with the stem-end in contact to the posterior cortical bone. More uniform strain distributions were observed with the stem aligned to the intramedullary canal axis. The load distribution of 80:20 shifts the strains to tensile laterally and a large increase of compressive strain in the medial distal tibia. Conclusions. A contributory factor of the clinically reported stem-end pain is possibly the direct effect of contact of the tibial stem-end to the posterior region of the cortical bone. The increased load to the medial tibial compartment is more critical for the development of pain

Summary Statement. This study describes the design and preliminary in vitro testing of a novel patch for the repair of rotator cuff tendon tears. The laminated design incorporates woven and electrospun components. The woven element provides the patch with excellent mechanical strength and the electrospun layer improves cell attachment and promotes cell orientation and diferentiation. Introduction. Aligned nanofibrous electrospun scaffolds have been previously proposed as ideal scaffolds for tendon repair, replicating the anisotropy of tendon and providing a biomimetic design to encourage tissue regeneration (Hakimi et al., 2012). However, such scaffolds are still limited in terms of mechanical properties. This paper presents the design of a novel patch for rotator cuff repair in which the electrospun scaffold is supported by a woven component. Patients & Methods. Aligned polydioxanone (PDO) electrospun scaffolds were produced using a single nozzle electrospinning set-up with a rotating collector. The woven component was created by weaving PDO monofilaments with a manual loom. The woven and non-woven constituents were bound by a non-destructive method which preserves the surface morphology of the electrospun material. For each type of scaffold, a minimum of 3 specimens were tested to failure in tension using Zwick machine at rate of 0.3 mm/min until failure. For in vitro work, human-derived tendon cells were extracted from rotator cuff tendon tissue obtained during surgical repair, with appropriate ethical approval. Cells were cultured on the scaffolds for at least 14 days. Results. The contribution of the woven component to the tensile strength of the assembled patch is about 20 times more when compared to the electrospun scaffold. In vitro work shows that human tenocytes grown on the nanofibrous non-woven electrospun component align in the direction of the fibre orientation. The appearance of the woven component is shown. Discussion/Conclusion. While the woven component provides most of the mechanical strength, the aligned electrospun fibres enable cell orientation along the axis of the patch. These cells display a similar morphology to tenocytes in native tendons. With the combination of biomimetic features and good mechanical properties, this novel PDO patch is an excellent candidate material to support tendon repair

One of the most controversial issues in total knee replacement is whether or not to resurface the patella. In order to determine the effects of different designs of femoral component on the conformity of the patellofemoral joint, five different knee prostheses were investigated. These were Low Contact Stress, the Miller-Galante II, the NexGen, the Porous-Coated Anatomic, and the Total Condylar prostheses. Three-dimensional models of the prostheses and a native patella were developed and assessed by computer. The conformity of the curvature of the five different prosthetic femoral components to their corresponding patellar implants and to the native patella at different angles of flexion was assessed by measuring the angles of intersection of tangential lines. The Total Condylar prosthesis had the lowest conformity with the native patella (mean 8.58°; 0.14° to 29.9°) and with its own patellar component (mean 11.36°; 0.55° to 39.19°). In the other four prostheses, the conformity was better (mean 2.25°; 0.02° to 10.52°) when articulated with the corresponding patellar component. The Porous-Coated Anatomic femoral component showed better conformity (mean 6.51°; 0.07° to 9.89°) than the Miller-Galante II prosthesis (mean 11.20°; 5.80° to 16.72°) when tested with the native patella. Although the Nexgen prosthesis had less conformity with the native patella at a low angle of flexion, this improved at mid (mean 3.57°; 1.40° to 4.56°) or high angles of flexion (mean 4.54°; 0.91° to 9.39°), respectively. The Low Contact Stress femoral component had the best conformity with the native patella (mean 2.39°; 0.04° to 4.56°). There was no significant difference (p > 0.208) between the conformity when tested with the native patella or its own patellar component at any angle of flexion. The geometry of the anterior flange of a femoral component affects the conformity of the patellofemoral joint when articulating with the native patella. A more anatomical design of femoral component is preferable if the surgeon decides not to resurface the patella at the time of operation

Summary. Computer assisted surgery (CAS) during total knee arthroplasty (TKA) is known to improve prosthetic alignment in coronal and sagittal plane. In this systematic review, no evidence is found that CAS also improves axial component orientation when used during TKA. Introduction. Primary total knee arthroplasty (TKA) is a safe and cost-effective treatment for end-stage knee osteoarthritis. Correct prosthesis alignment is essential, since malpositioning of the prosthesis leads to worse functional outcome and increased wear, which compromises survival of the prosthesis. Computer assisted surgery (CAS) has been developed to enhance prosthesis alignment during TKA. CAS significantly improves postoperative coronal and sagittal alignment compared to conventional TKA. However, the influence of CAS on rotational alignment is a matter of debate. Therefore purpose of this review is to assess published evidence on the influence of CAS during TKA on postoperative rotational alignment. Patients and Methods. This review was performed according to the PRISMA Statement. An electronic literature search was performed in Pubmed, Medline and Embase on studies published between 1991 and April 2013. Studies were included when rotational alignment following imageless CAS-TKA was compared to rotational alignment following conventional TKA. At least one of the following outcome measures had to be assessed: 1) rotational alignment of the femoral component, 2) rotational alignment of the tibial component, 3) tibiofemoral mismatch, 4) the amount of rotational outliers of the femoral component, 5) the amount of rotational outliers of the tibial component. Study selection was performed in two stages and data extraction and methodological quality assessment was conducted independently by two reviewers. Standardized mean difference (SMD) with 95% confidence interval (95% CI) was calculated for continuous variables. The SMDs were interpreted according to Cohen: an SMD of 0.2–0.4 was considered a small effect; 0.5–0.7 was considered moderate; and ≥ 0.8 was considered a large effect. For the comparison of the amount of outliers for femoral and tibial component rotation, the Odds ratio (OR) and 95% CI was calculated. The OR represents the odds of outliers occurring in the CAS group compared with the conventional group. An OR of < 1 favors the CAS group. The OR is considered statistically significant when the 95% CI does not include the value of 1. Results. Seventeen studies met the inclusion criteria. One study was considered of high, 15 studies of medium and one study of low methodological quality. SMD for rotation of the femoral component was −0.07 (−0.19–0.04). For rotation of the tibial component, the SMD was 0.11 (−0.01–0.24). Regarding tibiofemoral mismatch, the SMD was −0.27 (−0.57–0.02). For femoral outliers, the OR was 1.05 (0.78–1.43) and for tibial outliers the OR was 1.12 (0.86–1.47). Discussion / Conclusion. Results of this review show no evidence that CAS-TKA leads to better rotational alignment of the femoral or tibial component or tibiofemoral mismatch. Also no evidence was found that CAS results in a decrease of the amount of outliers regarding femoral or tibial component orientation. However, these conclusions have to be interpreted with caution. The number of included studies was low and strong heterogeneity existed between the studies. Of the 17 included studies, only one study was considered of high methodological quality. Moreover, different methods for assessing tibial component rotation have been used in the studies included

The biomechanics of the patellofemoral joint can become disturbed during total knee replacement by alterations induced by the position and shape of the different prosthetic components. The role of the patella and femoral trochlea has been well studied. We have examined the effect of anterior or posterior positioning of the tibial component on the mechanisms of patellofemoral contact in total knee replacement. The hypothesis was that placing the tibial component more posteriorly would reduce patellofemoral contact stress while providing a more efficient lever arm during extension of the knee. We studied five different positions of the tibial component using a six degrees of freedom dynamic knee simulator system based on the Oxford rig, while simulating an active knee squat under physiological loading conditions. The patellofemoral contact force decreased at a mean of 2.2% for every millimetre of posterior translation of the tibial component. Anterior positions of the tibial component were associated with elevation of the patellofemoral joint pressure, which was particularly marked in flexion > 90°. From our results we believe that more posterior positioning of the tibial component in total knee replacement would be beneficial to the patellofemoral joint

Dislocation remains a major concern after total hip replacement, and is often attributed to malposition of the components. The optimum position for placement of the components remains uncertain. We have attempted to identify a relatively safe zone in which movement of the hip will occur without impingement, even if one component is positioned incorrectly. A three-dimensional computer model was designed to simulate impingement and used to examine 125 combinations of positioning of the components in order to allow maximum movement without impingement. Increase in acetabular and/or femoral anteversion allowed greater internal rotation before impingement occurred, but decreases the amount of external rotation. A decrease in abduction of the acetabular components increased internal rotation while decreasing external rotation. Although some correction for malposition was allowable on the opposite side of the joint, extreme degrees could not be corrected because of bony impingement. We introduce the concept of combined component position, in which anteversion and abduction of the acetabular component, along with femoral anteversion, are all defined as critical elements for stability