Introduction. Varus alignment in total knee replacement (TKR) results in a larger portion of the joint load carried by the medial compartment. [1]. Increased burden on the medial compartment could negatively impact the implant fixation, especially for cementless TKR that requires bone ingrowth. Our aim was to quantify the effect varus alignment on the bone-implant interaction of cementless tibial baseplates. To this end, we evaluated the bone-implant micromotion and the amount of bone at risk of failure. [2,3]. Methods. Finite element models (Fig.1) were developed from pre-operative CT scans of the tibiae of 11 female patients with osteoarthritis (age: 58–77 years). We sought to compare two loading conditions from Smith et al.;. [1]. these corresponded to a mechanically aligned knee and a knee with 4° of varus. Consequently, we virtually implanted each model with a two-peg cementless baseplate following two tibial alignment strategies: mechanical alignment (i.e., perpendicular to the tibial mechanical axis) and 2° tibial varus alignment (the femoral resection accounts for additional 2° varus). The baseplate was modeled as solid titanium (E=114.3 GPa; v=0.33). The pegs and a 1.2 mm layer on the bone-contact surface were modeled as 3D-printed porous titanium (E=1.1 GPa; v=0.3). Bone material properties were non-homogeneous, determined from the CT scans using relationships specific to the proximal tibia. [2,4]. The bone-implant interface was modelled as frictional with friction coefficients for solid and porous titanium of 0.6 and 1.1, respectively. The tibia was fixed 77 mm distal to the resection. For mechanical alignment, instrumented TKR loads previously measured in vivo. [5]. were applied to the top of the baseplate throughout level gait in 2% intervals (Fig.1a). For varus alignment, the varus/valgus moment was modified to match the ratio of medial-lateral force distribution from Smith et al. [1]. (Fig.1b). Results. For both alignments and all bones, the largest micromotion and amount of bone at risk of failure occurred during mid stance, at 16% of gait (Figs.2,3). Peak micromotion, located at the antero-lateral edge of the baseplate, was 153±32 µm and 273±48 µm for mechanical and varus alignment, respectively. The area of the baseplate with micromotion above 40 µm (the threshold for bone ingrowth. [3]. ) was 28±5% and 41±4% for mechanical and varus alignment, respectively. The amount of bone at risk of failure at the bone-implant interface was 0.5±0.3% and 0.8±0.3% for the mechanical and varus alignment, respectively. Discussion. The peak micromotion and the baseplate area with micromotion above 40 µm increased with varus alignment compared to mechanical alignment. Furthermore, the amount of bone at risk of failure, although small for both alignments, was greater for varus alignment. These results suggest that varus alignment, consisting of a combination of femoral and tibial alignment, may negatively impact bone ingrowth and increase the risk of bone failure for cementless tibial baseplates of this TKR design

The concept of constitutional varus and controversy regarding placing the total knee arthroplasty (TKA) in a neutral versus physiologic alignment in varus osteoarthritic (OA) patients is an important current discussion. However, the physiologic mechanical alignment of a varus OA knee is unknown and the relative contribution of the femur and tibia to the mechanical axis is unknown. The goal of this study was to determine and analyse the physiologic mechanical axis of medial OA knees. Plain radiographs of the knee and full-leg standing radiographs of 1558 patients were reviewed for inclusion criteria; 313 patients with a non-arthritic knee and a contralateral varus end-stage OA knee were analysed in the coronal plane. The Hip-Knee-Ankle (HKA), Condylar-Hip (CH)(femoral), Condylar-Plateau (CP) (intra-articular) and Plateau-Ankle (PA)(tibial) angles were measured for both the arthritic and non-arthritic/physiologic knee. The relationship and contribution of all angles was analysed for every 2° degrees of progressive varus: from 4° valgus to 8° varus. The proportion of patients with constitutional varus was also determined for the sample population and correlated with increasing HKA. The mean CH (femoral) angle was valgus in all groups and decreased with progressive varus alignment (p< 0.0001), ranging from 3.8° ± 1.0° with HKA of 2–4° valgus, to 0.1° ± 1.5° with HKA of 6–8° varus. The mean PA (tibial) angle was varus in all groups and decreased from valgus to progressively varus alignment (p p<0.0001), ranging from 0.78° ± 1.4° with HKA 2–4° valgus, to 5.6° ± 1.9° with HKA 6–8° varus. The CP angle showed no difference between all groups (p=0.3). Forty five percent of males and 22% of females with arthritic HKA in varus alignment were found to have constitutional varus. Correlation of unilateral arthritic knees to the unaffected, physiologic aligned knee using full-leg radiographs indicates that it may be possible to understand the patient's physiologic, pre-arthritic coronal plane alignment. The mechanical axis of physiologic knees in a unilateral varus OA population demonstrates a variable contribution of the femur (CH) and tibia (PA) from overall valgus to varus alignment. In addition, a significant proportion of the sample population possessed constitutional varus. This may provide important information regarding the placement of physiologic TKA's and direct future research questions

Introduction. The current standard for alignment in total knee arthroplasty (TKA) is neutral mechanical axis within 3° of varus or valgus deviation [1]. This configuration has been shown to reduce wear and optimally distribute load on the polyethylene insert [2]. Two key factors (patient-specific hip-knee-ankle (HKA) angle and surgical component alignment) influence load distribution, kinematics and soft-tissue strains across the tibiofemoral (TF) joint. Improvements in wear characteristics of TKA materials have facilitated a trend for restoring the anatomic joint line [3]. While anatomic component alignment may aid in restoring more natural kinematics, the influence on joint loads and soft-tissue strains should be evaluated. The purpose of the current study was to determine the effect of varus component alignment in combination with a variety of HKA limb alignments on joint kinematics, loads and soft-tissue strain. Methods. A dynamic three-dimensional finite element model of the lower limb of a TKA patient was developed. Detailed description of the model has been previously published [4]. The model included femur, tibia and patella bones, TF ligaments, patellar tendon, quadriceps and hamstrings, and was virtually implanted with contemporary cruciate-retaining fixed-bearing TKA components. The model was initially aligned in ideal mechanical alignment with neutral HKA limb alignment. A design-of-experiments (DOE) study was performed whereby component placement was altered from neutral to 3° and 7° varus alignment, and HKA angle was altered from neutral to ±3° and ±7° (valgus and varus) (Figure 1). Results. HKA angle has a greater influence on kinematics, particularly PF medial-lateral (M-L) translation in early flexion and TF internal-external (I-E) rotation; at 60° flexion change in TF I-E rotation due to HKA angle was 12.4° compared to change due to component V-V alignment of 2.3° (Figure 1). Component alignment was the main factor in overall TF loads; varus component alignment increased the medial force, external torque and valgus torque acting on the insert. Shear force at the bone-implant interface increased by 15% (∼90N) with varus component rotation of 7°. Varus component alignment increased forces in the lateral structures and reduced forces in the medial structures (Figure 2). Both valgus HKA angle and varus component alignment altered M-L load distribution by reducing medial forces and increasing lateral forces (Figure 3). Discussion. Placement of TKA components in anatomic alignment has potential to better integrate the implants with the soft-tissues of the joint and may better reproduce natural kinematics. However, varus component alignment in conjunction with valgus HKA limb alignment substantially alters M-L distribution of load across the condyles, increasing the load on the lateral condyle. Varus component alignment will result in load distributions which are different from their mechanically aligned counterparts. As such, pre-clinical evaluation of components used in varus alignment should ensure that components are robust to loading conditions which will be encountered across the range of TKA patient HKA alignments

Background:. Appropriate positioning of total knee arthroplasty (TKA) components is a key concern of surgeons. Post-operative varus alignment has been associated with poorer clinical outcome scores and increased failure rates. However, obtaining neutral alignment can be challenging in cases with significant pre-operative varus deformity. Questions:. 1) In patients with pre-operative varus deformities, does residual post-operative varus limb alignment lead to increased revision rates or poorer outcome scores compared to correction to neutral alignment? 2) Does placing the tibial component in varus alignment lead to increased revision rates and poorer outcome scores? 3) Does femoral component alignment affect revision rates and outcome scores? 4) Do these findings change in patients with at least 10 degrees of varus alignment pre-operatively?. Patients and Methods:. 553 patients undergoing TKA for varus osteoarthritis were identified from a prospective database. Patients were divided into those with residual post-operative varus and those with neutral post-operative alignment. Revision rates and clinical outcome scores were compared between the two groups. Revision rates and outcome scores were also assessed based on post-operative component alignment. The analysis was repeated in a subgroup of patients with at least 10 degrees of pre-operative varus. Results:. At a mean follow-up of 5.7 years (range: 2 to 19.8 years), residual varus deformity did not yield significantly increased revision rates or poorer outcome scores. Varus tibial component alignment and valgus femoral component alignment were associated with poorer outcome scores. Results were similar in the significant varus subgroup. Conclusions:. Residual post-operative varus deformity after TKA does not yield poorer clinical results in patients with pre-operative varus deformities, providing tibial component varus is avoided

Using a tensor for total knee arthroplasty (TKA) that is designed to facilitate soft tissue balance measurements with a reduced patello-femoral (PF) joint, we examined the influence of pre-operative deformity on intra-operative soft tissue balance during posterior-stabilized (PS) TKA. Joint component gap and varus angle were assessed at 0, 10, 45, 90 and 135° of flexion with femoral trial prosthesis placed and PF joint reduced in 60 varus type osteoarthritic patients. Joint gap measurement showed no significant difference regardless the amount of pre-operative varus alignment. With the procedures of soft tissue release avoiding joint line elevation, however, intra-operative varus angle with varus alignment of more than 20 degrees exhibited significant larger values compared to those with varus alignment of less than 20 degrees throughout the range of motion. Accordingly, we conclude that pre-operative severe varus deformity may have the risk for leaving post-operative varus soft tissue balance during PS TKA

Introduction. Evaluations of Computer-assisted orthopaedic surgery (CAOS) systems generally overlooked the intrinsic accuracy of the systems themselves, and have been largely focused on the final implant position and alignment in the reconstructed knee [1]. Although accuracy at the system-level has been assessed [2], the study method was system-specific, required a custom test bench, and the results were clinically irrelevant. As such, clinical interpolation/comparison of the results across CAOS systems or multiple studies is challenging. This study quantified and compared the system-level accuracy in the intraoperative measurements of resection alignment between two CAOS systems. Materials and Methods. Computer-assisted TKAs were performed on 10 neutral leg assemblies (MITA knee insert and trainer leg, Medial Models, Bristol, UK) using System I (5 legs, ExactechGPS®, Blue-Ortho, Grenoble, FR) and System II (5 legs, globally established manufacturer). The surgeries referenced a set of pre-defined anatomical landmarks on the inserts (small dimples). Post bone cut, the alignment parameters were collected by the CAOS systems (CAOS measured alignment). The pre- and post- operative leg surfaces were scanned, digitized, and registered (Comet L3D, Steinbichler, Plymouth, MI, USA; Geomagic, Lakewood, CO, USA; and Unigraphics NX version 7.5, Siemens PLM Software, Plano, TX, USA). The alignment parameters were measured virtually, referencing the same pre-defined anatomical landmarks (baseline). The signed and unsigned measurement errors between the baseline and CAOS measured alignment were compared between the two CAOS systems (significance defined as p<0.05), representing the magnitude of measurement errors and bias of the measurement error generated by the CAOS systems, respectively. Results. The measurement errors are presented [Table 1]. For unsigned measurement error, System II was higher in the tibial varus/valgus alignment and posterior slope (p≤0.01), and lower in the femoral varus/valgus alignment (p=0.03), compared to System I [Fig. 1]. System II exhibited higher error bias towards tibial varus alignment (up to 2.59°), more posterior slope (up to 1.41°), and more femoral hyper extension (up to 1.6°) than System I (p<0.01) [Fig. 1]. The mean signed and unsigned errors were generally less than 1°, except for System II in the measurement of tibial varus/valgus alignment (signed and unsigned mean errors=1.93°). Discussion. This study reported system-dependent bias and variability associated with intraoperative measurements of alignment parameters during TKA. The results showed that System I generally had lower variability and less bias than System II. Although the majority of the significant differences found were clinically irrelevant (<1° in means), System II was notably shown to produce on average ∼2° measurement errors in tibial varus/valgus alignment biased towards varus. Intra-operative measurement of surgical resection parameters during imageless computer-assisted TKA surgery is a critical step, in which a surgeon directly relies on the real-time data to prepare the bony resections and check the final realized cuts. Clinical-level accuracy in alignment outcomes has been shown to be system-dependent [2], this study further suggested there are differences in system-level accuracy between CAOS systems

Introduction. Knee joint should be aligned for reconstruction of the function in Total Knee Replacement(TKR). Although a surgeon try to correct the alignment of a knee joint, sometimes varus/valgus alignment has been tried in order to reconstruct function of knee joint. As a result, the varus or valgus alignment affects to ligaments and soft tissue, and the contact condition is changed between femoral component and tibial insert. One of important factor, wear characteristics of an implant can be changed due to the contact condition. In this study, we performed static contact tests from extension to flexion in varus and valgus to define the effect to contact condition when the alignment is varus or valgus. Methods. LOSPA TKR femoral component #6 and Tibial insert #5 manufactured by Corentec Co., Ltd. were used as test specimens. The tests have performed with adapting ASTM F2777–10 ‘Standard Test Method for Evaluating Knee Bearing (Tibial Insert) Endurance and Deformation under High Flexion’. The test set like as Fig. 1. The load is applied at 7:3 ratio of lateral-medial by adapting gait analysis. The 5° of jig is used to compare the result in neutral, varus and valgus. The fuji films were used in tests were scanned, and the results were analyzed the compressed area and contact stress as angles of flexion in neutral stance and varus/valgus from scanning. The tests were performed 5 times per each for a reliability. Results. The results of compressed area became decreasing as the angle of flexion was increased. The compressed areas in varus alignment was little smaller than the results in varus. The compressed areas in neutral stance were the greatest in all results. (Fig. 2.) There were little differences between the results in varus and valgus in view point of peak contact stress. (Fig. 3). Discussion. Because the neutral stance makes the compressed area become more increasing than varus/valgus alignment, so that the lowest contact stress is induced between femoral component and Tibial insert. There is little difference between varus and valgus in viewpoint of peak contact stress if the varus/valgus alignment is not excess. It is considered that the alignment is tried to correct because low contact stress makes wear improve

Femoral components used in total hip arthroplasty (THA) rely on good initial fixation determined by implant design, femoral morphology, and surgical technique. A higher rate of varus alignment may be of specific concern with short stem implants. Varus placement in uncemented femoral components has been proven not to be detrimental to clinical function; though long-term bone remodeling secondary to varus placement remains unknown. The goal of this study was to compare the clinical and radiographic outcomes in patients who underwent THA with one of two uncemented short stem metaphyseal engaging implants at minimum two-year follow-up. A review of 105 patients (average age 65 years; BMI 29 kg/m. 2. ) who underwent a total of 109 primary THAs using the ABG II short stem femoral implant (Stryker, Mahwah, NJ), and 160 hips in 149 patients (average age 70 years; BMI 28 kg/m. 2. ) who underwent primary THA using the Citation stem (Stryker, Mahwah, NJ). The same surgeon (SDS) performed all surgeries through a less invasive posterolateral approach. Pre-operative and post-operative Harris Hips Scores (HHS) and WOMAC scores were collected. Digital radiograph analysis was performed including measuring the stem alignment relative to the femoral shaft. A stem placed with greater than 5 degrees of varus was considered to be in varus. There was no significant difference in demographics (age, gender or BMI) or pre-operative HHS and WOMAC scores between the two groups. Follow-up HHS was 90 (range 63–100) and 94 (range 70–100) for the ABG II and Citation groups, respectively. Follow-up WOMAC scores were 10 (range 0–24) and 6 (range 0–43) for the ABG II and Citation groups, respectively. There was no statistically significant difference in any of the scores between the two groups (p>0.05). When looking at AP radiographs for postoperative intramedullary alignment, none of the ABG II implants were placed in varus (>5°), while a small number (4.9%) of Citation implants were implanted in varus alignment. No significant difference was observed in the alignment between the two groups (p>0.05). Average post-op alignment with the ABG was 1.10° (range −4.7–4.9°) and 0.88° (range −4.5–8.9°) with the Citation. The clinical results associated with the use of these stems in patients of all ages and bone types have been identical to those achieved by uncemented stems of standard length. Both implants in this study had excellent clinical and functional results in primary THA after a minimum 24-month follow up. In addition, postoperative radiographic analysis demonstrated that these stems can be reliably and reproducibly placed in neutral alignment despite their short length. The lateral flare on the Citation implant led to a greater number of implants in varus alignment, potentially affecting offset and leg-length, yet the relative increased incidence compared to the ABG II was not significant. Further research is needed in designing implants that optimize proximal femoral contact while maintaining alignment and overall hip kinematics

Background. High tibial osteotomy is a common procedure to treat symptomatic osteoarthritis of the medial compartment of the knee with varus alignment. This is achieved by overcorrecting the varus alignment to 2–6° of valgus. Various high tibial osteotomy techniques are currently used to this end. Common procedures are medial opening wedge and lateral closing wedge tibial osteotomies. The lateral closing wedge technique is a primary stable correction with a high rate of consolidation, but has the disadvantage of bone loss and change in tibial condylar offset. The medial opening wedge technique does not result in any bone loss but needs to be fixated with a plate and may cause tibial slope and medial collateral ligament tightening. Purpose. The purpose of this article is to examine correlation between femoral rotational angle and subjective satisfaction of high tibial osteotomy outcome of the range of motion of knee joint. Materials and methods. The subjects were 15 patients (6 males, 9 females) with primary osteoarthritis undergoing high tibial osteotomy from June of 2004 to August of 2008. They were CT tested on the knee joint before and after high tibial osteotomy. TEA and Akagi's line are analysed as percentages. The Kendall's and Spearman's nonparametric correlation coefficient were used for the statistical tests with 0.5 level of significance. Results. We observed a negative linear relationship (p = 0.0001) between the femoral component external rotation (measured by TEA) and active and passive ROM. Pearson Coefficient was −0.80, −0.57, respectively. We can find a negative linear relationship (p=0.001) between Akagi's line and passive ROM, and Pearson coefficient was −0.863. Preoperative flexion contracture, age, tibiofibula angle, pain, and other factors do not influence the ROM of the patient. Follow up duration do not influence the ROM of the patient. Conclusion. The result reveals that femoral rotational angle correlates with not the range of motion of knee joint but subjective satisfaction of the patients. In HTO, beside deformity correction in coronal plane, rotation of the femur contributes postoperative pain relief

Summary. The effect of polyethylene wear and lift-off between the tibial and femoral components on the mechanical axis was assessed in primary TKA (Total Knee Arthroplasty) based on retrieval data and full leg radiographs. Introduction. Controversy exist regarding performing a TKA with component placement in physiologic versus neutral alignment. Some literature indicates good survivorship and superior clinical outcome in undercorrected TKA's for varus osteoarthritic knees. However, other literature indicates decreased survivorship and coronal plane alignment is still one of the contributing factors to wear in total knee arthroplasty (TKA). The two determinants of the intra-articular deformity in TKA arepolyethylene wear and lift-off between the tibial and femoral compartment. The goal of this study was to evaluate the impact of wear and lift-off on the mechanical axis in neutral and varus aligned TKA's. Materials and methods. Seventy-six tibia inserts retrieved from neutral and varus aligned primary TKA's with a minimum 5 year in vivo time were assessed for the ratio of wear (RW) using a micrometer. Full-leg radiographs were assessed to determine the Hip-Knee-Ankle (HKA) and Condylar-Plateau (CP) angle, which is the intra-articular deformity. The HKA and CP angle was corrected for wear to a New-HKA angle (N-HKA) and the New-CP angle (New-CP), which was defined as lift-off. The RW and N-CP was subsequently assessed for neutral (0 ± 3°), mild varus (3 – 6°) and moderate varus (>6°) TKA's based on the mechanical axis. Results. Demographics of the study are shown in table 1. The RW correlated with frontal plane alignment, with increased wear being related to progressive varus alignment (p < 0.01). The difference from CP to N-CP and HKA to N-HKA was significant for the mild varus (p<0.01) and moderate varus (p<0.01) group. (table 2 and 3). The difference in N-CP (lift-off) among alignment groups was significant with increased lateral lift off with progressive varus alignment (p=0.02). Discussion. After correction of the intra-articular angle and the mechanical axis by the ratio of wear, coronal plane alignment significantly changed in the mild and moderate varus aligned TKA population. Both polyethylene wear and lift-off contribute to this, with progressive values in higher varus aligned TKA's. These results are important when targeting an undercorrection in TKA but should also be taken into account when describing the mechanical axis of TKA's. Conclusion. Lift-off between the tibia and femur and wear contribute significantly to the change in mechanical alignment in primary TKA's with higher values in progressive varus

Introduction. Using the tibial extramedullary guide needs meticulous attention to accurately align the tray in total knee arthroplasty (TKA). We previously reported the risk for varus tray alignment if the anteroposterior (AP) axis of the ankle was used for the rotational direction of the guide. The purpose of our study was to determine whether aligning the rotational direction of the guide to the AP axis of the proximal tibia reduced the incidence of varus tray alignment when compared to aligning the rotational direction of the guide to the AP axis of the ankle. Materials and Methods. Clinical Study. A total of 80 osteoarthritis (OA) knees after posterior stabilized TKA were recruited in this study. From 2002 to 2004, the rotational alignment of the guide was adjusted to the AP axis of the ankle (Method A: Figure 1, N = 40 knees). After 2005, the rotational alignment of the guide was adjusted to the AP axis of the proximal tibia (Method B: Figure 1, N = 40 knees). The AP axis of the proximal tibia was defined as the line connecting the middle of the attachment of the PCL and the medial third border of the attachment of the patellar tendon. The guide was set at a level of 10 mm distal to the lateral articular surface. Postoperative alignment was compared between the two groups using full-lengthanteroposterior radiograph. Computer simulation. Computer simulation was performed to determine the effect of ankle rotation on tibial tray alignment, using three-dimensional bone and skin model reconstructed from CT images of 75 OA knees (Figure 2). The position of the distal end of the guide in Method B was evaluated on the coronal plane perpendicular to the AP axis of the proximal tibia and of the ankle respectively. <Displacement> was the distance from the distal end of the guide to the midpoint-malleolar points (+: medial position). <Distance ratio> was the ratio of <Displacement> dividing by the entire width of the malleolar. Results. The results of the postoperative alignment for both methods from the clinical study are shown in Table 1. The number of the knees with more than 3 degrees of varus aligned tibial component significantly decreased with the Method B from the Method A. The computer simulation showed that the position of the guide varied great among individuals in the direction of the AP axis of the ankle joint. Discussion. When an extramedullary alignment guide is used in TKA, a rotational mismatch between the proximal part of the tibia and the ankle joint can induce a varus alignment of the tibial component. Computer simulation also supported our conclusion that the surgeon should not evaluate the distal end of the guide in the direction of the ankle joint to minimize the effects of anatomic variation for proper coronal alignment

Background:. Polyethylene wear in total knee arthroplasty (TKA) is influenced by patient, surgeon and implant factors. The objective of this study is to assess the effect of limb alignment, implant position and joint line position on the pattern of wear in posterior stabilized (PS) tibial inserts. Methods:. This was a retrieval analysis of 83 PS liners collected from patients who underwent revision surgery from 1999 to 2011. Inserts were divided into 16 zones and a microscopic analysis of surface damage was carried out. We determined overall damage with a scoring system. Pre-revisions radiographs were reviewed and analyzed for correlation with the wear profile. Results:. The mean age was 73 years old (range 45 to 96 years old) and the mean duration of implantation was 3.5 years (range 0.1 to 10.6 years). The most common reason for revision was infection (71%, 59 of 83 liners), followed by aseptic loosening (6%, 5 of 83 liners) and instability (6%, 5 of 83 liners). The most common mode of wear was burnishing, followed by abrasion and pitting. The total damage score was significantly higher in knees with postoperative varus alignment more than 3 degrees (p = 0.03). Postoperative varus alignment was associated with significantly more wear in the medial compartment (p = 0.03). The total damage score to the post was significantly more in knees with joint line elevation more than 5 mm (9.7 ± 3.9, compared to 6.5 ± 3.7 in knees with less joint line elevation) (p = 0.05). The most commonly affected compartment was the medial compartment. Conclusion:. Limb malalignment and implant malposition resulted in more wear in PS TKA

INTRODUCTION. Over the past 40 years of knee arthroplasty, significant advances have been made in the design of knee implants, resulting in high patient satisfaction. Patellar tracking has been central to improving the patient experience, with modern designs including an optimized Q-angle, deepened trochlear groove, and thin anterior flange.[1–4] Though many of today's femoral components are specific for the left and right sides, Total Joint Orthopedics’ (TJO) Klassic® Knee System features a universal design to achieve operating room efficiencies while providing all the advancements of a modern knee. The Klassic Femur achieves this through a patented double Q-angle to provide excellent patellar tracking whether implanted in the left or the right knee (Figure 1). The present study examines a prospective cohort of 145 consecutive TKA's performed using a modern universal femur and considers patients’ pre- and post-operative Knee Society Clinical Rating System score (KSS). METHODS AND MATERIALS. 145 primary total knee arthroplasties (TKA) were performed during the study using a measured resection technique with a slope-matching tibial cut for all patients. The posterior cruciate ligament (PCL) was sacrificed to accommodate an ultra-congruent polyethylene insert. The distal femur was cut at five degrees (5°) valgus; the tibia was resected neutral (0°) alignment for valgus legs and in two degrees (2°) of varus for varus alignment. The patella was resurfaced for all patients. Patients were followed annually for up to 46 months and were evaluated using the KSS score on a 200-point scale. RESULTS. The final study group comprised 127 primary TKAs. The average age was 68 years (51–90) with 45 males and 68 females. The average weight was 110kg (range: 75–151kg) for men and 88kg (range: 50–129kg) for women. One patient deceased during the follow-up period, four required manipulation under anesthesia, and two required revision for periprosthetic joint infection. There were no failures due to patellar maltracking. No special soft tissue releases were required in any patient. Average pre-operative knee score was 107, improving to 182 at average follow-up of 41 months (36–46 months). Results are summarized in Table 1. DISCUSSION. The improvement in patient clinical experience demonstrates that a universal femoral design can achieve excellent results if it incorporates modern technologies. A double Q-angle design with a deepened trochlear groove and a thin anterior flange appears to provide excellent patellar tracking for all patients in this cohort. This study is limited to the experience of a single institution. Further study would improve the extensibility of these findings. It does show, however, that a femur using a universal design with modern patellar tracking can improve patient satisfaction with their knee following TKA. For any figures or tables, please contact the authors directly

Objective. Open-wedge high tibial osteotomy (OWHTO) involves performing a corrective osteotomy of the proximal tibia and removing a wedge of bone to correct varus alignment. Although previous studies have investigated changes in leg length before and after OWHTO using X-rays, none has evaluated three-dimensional (3D) leg length changes after OWHTO. We therefore used 3D preoperative planning software to evaluate changes in leg length after OWHTO in three dimensions. Methods. The study subjects were 55 knees of 46 patients (10 men and 36 women of mean age 69.9 years) with medial osteoarthritis of the knee or osteonecrosis of the medial femoral condyle with a femorotibial angle of >185º and restricted range of motion (extension <–10º, flexion <130º), excluding those also suffering from patellofemoral arthritis or lateral osteoarthritis of the knee. OWHTO was simulated from computed tomography scans of the whole leg using ZedHTO 3D preoperative planning software. We analyzed the hip-knee-ankle angle (HKA), flexion contracture angle (FCA), mechanical medial proximal tibial angle (mMPTA), angle of correction, wedge length, 3D tibial length, 3D leg length, and 3D increase in leg length before and after OWHTO. We also performed univariate and multivariate analysis of factors affecting the change in leg length (preoperative and postoperative H-K-A angle, wedge length, and correction angle). Results. Mean HKA increased significantly from −4.7º ± 2.7º to 3.5º ± 1.3º, as did mean mMPTA from 83.7º ± 3.3º to 92.5º ± 3.0º (p <0.01). Mean FCA was 4.7º ± 3.6° preoperatively and 4.8º ± 3.3º postoperatively, a difference that was not significant (p = 0.725). The mean correction angle was 9.1º ± 2.8º and the mean wedge length was 9.4º ± 3.2º mm. Mean tibial length increased significantly by 4.7 ± 2.3 mm (p <0.01), and mean leg length by 5.6 ± 2.8 mm (p <0.01). The change in leg length was strongly correlated with wedge length (R = 0.846, adjusted R. 2. = 0.711, p <0.01). Discussion and Conclusion. Mean 3D leg length after OWHTO increased significantly by 5.4 ± 3.1 mm. A difference in leg length of >5 mm is believed to affect back pain and gait abnormalities, and changes in leg length must therefore be taken into consideration. The 3D dimensional change in leg length was strongly correlated with wedge length, and could be predicted by the formula (change in leg length in mm) = [(wedge length in mm) ×0.75) − 1.5]. For any figures or tables, please contact authors directly

Non- or semi-constraint TKA implants do have their limitations in the absence of collateral ligaments, severe deformity, large osseous defects and gross flexion - extension instability or mismatch, even in primary TKA. Additionally instability is increasingly recognised as a major failure factor in primary and revision TKA. Historically most of the first pure hinged TKA implants have shown disappointing results, due to early loosening based on excessive force transmission from the hinge mechanism to the bone-cement interface, used the use of all metal articulation, suboptimal instrumentation or design. Consequently a hinged design was abandoned by most US surgeons. However, some European centres continued with the use of some early European designed pure- and rotating hinged implants. Although most indication in primary TKA can be solved with modular non- or semi-constrained implants, an adequate balancing might require a relevant soft tissue release or reconstruction with allografts. This consequently increases the complexity and operative time with less predictable results in the elderly patient with principal less healing potential, desirable early post-operative full weightbearing and full range of motion. Thus potential indications in the elderly for a rotating- or pure hinged implant in primary TKA include: . –. Complete MCL instability. –. Severe varus or valgus deformity (>25°) with necessary relevant soft tissue release. –. Relevant bone loss with insertions of collaterals. –. Gross flexion-extension in balance. –. Post-traumatic with distal femur or proximal tibia fracture. –. Stiff knee. –. Severe osteoporosis in the old patient. –. Post infectious for a one staged implantation with specific antibiotics in cement. While some authors showed excellent survival rates in of 96% after 15 years in primary TKA, some recent studies revealed high complication rates of up to 25%, including a high infection rate of 2.9%. This remains inconsistent with our clinical results in primary TKA, which revealed an overall survival rate in patients over 60 years of 94% after 13 years, while patients < 60 years revealed a survival rate of only 77%. Correlation between survival rate and deformity revealed in varus alignment a survival rate of 97%, whereas in valgus only a rate of 79%. Consequently we strictly reserve a rotational hinge for patients > 60 years with a combined varus alignment, whereas in severe valgus deformities a pure hinged should be used for our implant design. Limitations of most hinged implants are relatively rare. In our hands the main limitation is hyperextension and weak extensor mechanism, because this leads to early loosenings

Purpose. Coronal plane malalignment at the level of the tibiotalar joint is not uncommon in advanced ankle joint arthritis. It has been stated that preoperative varus or valgus deformity beyond 15 degrees is a relative contraindication and deformity beyond 20 degrees is an absolute contraindication to ankle joint replacement. There is limited evidence in the current literature to support these figures. The current study is a prospective clinical and radiographic comparative study between patients who underwent total ankle arthroplasty with coronal plane varus tibiotalar deformities greater than 10 degrees and patients with neutral alignment, less than 10 degrees of deformity. Method. Thirty-six ankles with greater than 10 degrees of varus alignment were compared to thirty-six ankles which were matched for implant type, age, gender, and year of surgery. Patients completed preoperative and yearly postoperative functional outcome scores including the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot scores, the Ankle Osteoarthritis Scale (AOS) and the Short Form-36 Standard Version 2.0 Health Survey. Weightbearing preoperative and postoperative radiographs were obtained and reviewed by four examiners (AC, AQ, TD, TT) and measurements were taken of the degree of coronal plane deformity. Results. After a mean follow-up of 27 months (9–54), the varus ankles improved significantly on the AOFAS (P<0.0001), AOS-Pain Score (P<0.0001), AOS-Disability Score (P<0.0001), and SF-36 Physical Component Score (P<0.0001). There was no improvement in SF-36-Mental Component Score. (P=0.722). There was no statistically significant differences between the two groups when comparing AOFAS (P=0.155), AOS-Pain Score (P=0.854), AOSDisability Score (P=0.593), SF-36-Physical Component Score (P=0.433), SF-36 Mental Component Score (P=0.633). Sixteen of Thirty-Six ankles in the varus group needed a secondary procedure (implant failure, infection, malalignment) which was approaching significance in comparison to eight ankles in the neutral group. (P = 0.079). Secondary procedures in the varus group included: tendon transfers, calcaneal / metatarsal / malleolar ostoetomies and ligament reconstructions. Radiographically, the pre-operative coronal plane varus tibiotalar deformity averaged 19.4 6.4 and postoperatively 1.44 2.6 (P< 0.0001). There was no statistical difference in post operative tibiotalar alignment between the varus and neutral groups (P<0.05). Conclusion. The clinical outcome of TAR performed in ankles with pre-operative varus alignment >10 degrees is comparable with that of neutrally aligned ankles. The increased number of secondary procedures in the varus group was attributed to the complexity of the deformity and the steep learning curve. Outcomes as measured radiographically and through validate scores were similar to patients without deformity suggesting that varus coronal plane deformity of the talus is not a contraindication to total ankle replacement

[Objective]. The objectives of this study are to measure the morphometric parameters of pre-operative distal femur in Japanese patients who received TKA, to investigate the differences in distal femoral anatomy between the genders, and to compare the measurements with the dimensions of femoral implants current used in Japan. [Methods]. One-hundred seventy-nine Japanese patients who underwent TKA in Osaka Koseinenkin Hospital from April, 2009 to December, 2011 were included in this study. The genders and diagnoses were 25/ 154 patients (male/ female) and 143/ 36 patients [osteoarthritis (OA)/ rheumatoid arthritis (RA)], respectively. The mean age, height and body weight were 73.2 years, 152.2 cm and 56.7 kg, respectively. We measured the AP length, ML width, aspect ratio angle of distal femur. The measurement points on the medial condyle was 10 mm and on the lateral condyle was 8 mm from the lowest points of the medial and lateral posterior condyle to stimulate the optimal cutting thickness. We evaluated the relationship between AP length and ML width, or aspect ratio and ML width in diagnosis, alignment and gender. We also compared the measurements with the dimensions of femoral implants current used in Japan. Continuous variables were assessed using the Mann-Whitney's U test. Relationship between AP length and ML width, or aspect ratio and ML width were assessed using simple regression analysis. Regression lines were assessed using analysis of covariance. For all tests, probability values (p values) of < 0.05 were considered to indicate statistical significance. [Results]. The mean AP length, ML width, aspect ratio, SEA/PCA angle and Whiteside/SEA angle were 58.8 mm, 64.7 mm, 0.91, 3.5 degrees of external rotation and 1.6 degrees of external rotation, respectively. The both relationship between AP length and ML width, and aspect ratio and ML width were significant (p < 0.001). As the ML width was getting longer, AP length was getting shorter and aspect ratio was getting lower. Although analysis of covariance between OA and RA in the relationship between aspect ratio and ML width was not significant (p = 0.955), that of valgus alignment [femorotibial angle (FTA) < 170 degrees] and varus alignment (FTA > 176 degrees) were significant (p = 0.003). The AP length, ML width in male (63.6 mm, 72.7 mm) were longer than those in female (58.1 mm, 63.4 mm), and aspect ratio in male (0.88) were lower than that in female (0.92) significantly (all p < 0.001). Although analysis of covariance between male and female in the relationship between AP length and ML width, and aspect ratio and ML width were not significant (p = 0.985 and 0.555). [Conclusion]. The aspect ratio showed a higher ratio for smaller knees and a proportionally lower ratio for lager knees in Japanese. The tendency of aspect ratio change with ML width was different between valgus and varus alignment. As the tendency of aspect ratio change with ML width was not different between male and female, the gender difference of aspect ratio was related to the difference of skeleton size (ML width) between male and female

Introduction. Aligning the tibial tray is a critical step in total knee arthroplasty (TKA). Malalignment, (especially in varus) has been associated with failure and revision surgery. While the link between varus malalignment and failure has been attributed to increased medial compartmental loading and generation of shear stress, quantitative biomechanical evidence to directly support this mechanism is incomplete. We therefore constructed and validated a finite element model of knee arthroplasty to test the hypothesis that varus malalignment of the tibial tray would increase the risk of tray subsidence. Methods. Cadaver Testing. Fresh human knees (N = 4) were CT scanned and implanted with TKA cruciate-retaining tibial tray (Triathlon CR, Stryker Orthopaedics, New Jersey). The specimens were subjected to ISO-recommended knee wear simulation loading for up to 100,000 cycles. Micromotion sensors were mounted between the tray and underlying bone to measure micromotion. In two of the specimens, the application of vertical load was shifted medially to generate a load distribution ratio of 55:45 (medial:lateral) to represent neutral varus-valgus alignment. In the remaining two specimens, a load distribution ratio of 75:25 was generated to represent varus alignment. Finite element analysis. qCT scans of the tested knees were segmented using MIMICS (Materialise, Belgium). Material properties of bone were spatially assigned after converting bone density to elastic modulus. A finite element model of the tibia implanted with a tibial tray was constructed (Abaqus 6.8, Simulia, Dassault Syst`mes). Boundary conditions were applied to simulate experimental mounting conditions and the tray was subjected to a single load cycle representing that applied during cadaver loading. Results. The two cadaver specimens tested at 55:45 medial:lateral (M:L) force distribution survived the 100,000 cycle test, while both cadaver specimens tested at 75:25 M:L force distribution failed. The finite element model generated distinct differences in compressive strain distribution patterns in the proximal tibia. A threshold of 2000 microstrain was used for fatigue damage in bone under cyclic loading. Both specimens loaded under 75:25 M:L distribution demonstrated substantially larger cortical bone volumes in the proximal tibial cortex that were greater than this fatigue threshold. Discussion & Conclusion. We validated a finite element model of tibial loading after TKA. Local compressive strains directly correlated with subsidence and failure in cadaver testing. A significantly greater volume of proximal tibial cortical bone was compressed to a strain greater than the fatigue threshold in the varus alignment group, indicating an increased risk for fatigue damage. This model is extremely valuable in studying the effect of surgical alignment, loading, and activity on damage to proximal bone. Emerging techniques that customize tibial tray placement to the individual patient's pre-arthritic alignment run counter to the traditional recommendations for coronal alignment to the mechanical axis of the knee. A method that determines the risk of bone damage in a patient-specific manner can provide the surgeon with a safe range for component alignment and may even be applicable in preoperative planning

No, Neutral mechanical axis has never been regarded as “necessary” to the success of TKA. In fact it has never been established as “ideal” with published data. Tibial femoral alignment after TKA is important, but it is also an issue that we do not understand completely. Neutral mechanical alignment refers to the relationship between the mechanical axes of the femur and tibia as shown on full length radiographs. “Neutral” means that these axes are collinear, i.e. that a line may be drawn from the center of the hip to the center of the ankle and it will intersect the center of the knee joint. The allure of the “straight line” has led many surgeons to regard a neutral mechanical axis as “perfection” for TKA surgery, but indeed, it is not the usual “normal” alignment for most human knees, nor is it the target for many conventional knee replacements. The “neutral mechanical axis” represents OVERCORRECTION for most knees. Moreland demonstrated in 1987 that few human knee joints are naturally aligned “in neutral”, but with the line from center of hip to center of ankle passing through the medial compartment. This tendency to relative varus mechanical axis in most human knees was corroborated by Bellemans et al in 2012. They substituted the word “constitutional varus” for what would otherwise be known as “normal alignment”. In general, patients with pathologic or significant varus alignment, whose arthroplasties have been performed competently, are at greatest risk for failure by wear, osteolysis and loosening. This is the prototypical failure mechanism that pre-occupied the surgeons responsible for making knee arthroplasty successful in the 1970s. The first paper to identify varus TKA alignment and failure due to loosening was Lotke and Ecker in 1977. They worked from short radiographs and ushered in an era of careful attention to valgus TKA alignment-not neutral alignment. Correction of varus deformity combined with ligament balancing was probably responsible for making condylar type knee arthroplasties work durably in the early days. Full length radiographs, used by Kennedy and White in 1987 to study alignment in unicompartmental arthroplasties, provide a more sophisticated method of evaluating knee alignment. These studies must be aligned with correct rotation to be valid. Computerised navigation was probably responsible for some surgeon's dedication to the neutral mechanical axis. The study of Parratte et al from Mayo has received much attention and argued that a neutral mechanical axis did NOT improve success rates at 15 years. It should be noted that these TKA's were expertly performed and even the less well-aligned cases were not “excessively” malaligned. This study does not state that alignment is irrelevant to the success of TKA, but rather that a range of alignments (with stability) might be expected to produce a durable arthroplasty. Concurrent with these developments has been an interest in “under-correcting” knee deformity or allowing osseous anatomy (with compensation for cartilage loss) guide component position. In truth, it is inaccurate to describe conventional “align and balance” techniques as necessarily seeking a neutral mechanical axis. Most classical alignment techniques do, however, alter the angle of component position from the original articular surface angles and theoretically may not function as well with the native soft tissue environment. Surgeons who would align the TKA identically to the arthritic knee may credit previous generations with improving the technology such that this is a possibility. If every patient is to be aligned with this technique, however, this suggests that soft tissue pathology does not exist. As with all complex issues, glib answers are to be avoided and deep analysis is appropriate

Introduction. There have been concerns regarding the quality of training received by Orthopaedic trainees. There has been a reduction in working hours according to the European working times directive. National targets to reduce surgical waiting lists has increased the workload of consultants, further reducing the trainees' surgical experience. Navigation assisted procedures are successfully used in orthopaedics and provides useful feedback to the surgeon regarding precision of implant placement. We investigated the use of navigation aids as an alternative source of training surgical trainees. Methods. We choose a navigation assisted knee replacement (TKR) model for this study. A first year Orthopaedic registrar level trainee was taught the TKR procedure by a scrubbed consultant in 5 cases. He was then trained in use of non-CT based navigation surgery. The Trainee then performed navigation assisted non-complex primary TKR surgery. A consultant Orthopaedic surgeon was available throughout for advice and support. Data collected included pre and post procedure valgus and varus alignment of the knee, total operative time and WOMAC scores pre and post operatively. Results. A total of 42 TKRs were performed. Intra-operative review by the consultant surgeon was necessary on 3 occasions in the first 10 cases and two occasions in the remaining cases. The average operative time reduced from 184.25 minutes in the first 10 cases to 163.11 minutes in the next 20 cases and 150.33 minutes in the next 12 cases. The varus/valgus alignment was corrected to within 8 degrees in all cases. A significant improvement in WOMAC scores was recorded for all patients (p< 0.05). Conclusion. We believe that this model can be used as a training aid in various orthopaedic surgical procedures