Objective. As the aging society progresses rapidly in Japan, the number of elderly patients underwent TKA is increasing. These elderly patients do not expect to do sports, but regain independency in the activity of daily living. Therefore, we measured basic ambulatory function quantitatively using 3m timed up and go (TUG) test. We clinically experienced patient with medially unstable knee after TKA was more likely to result in the unsatisfactory outcome. We hypothesized that post-operative knee stability influenced ambulatory function recovery after TKA. In this study, we evaluated ambulatory function and knee stability quantitatively, and analyzed the effect of knee stability on the ambulatory function recovery after TKA. Materials & Methods. Seventy nine patients with varus type osteoarthritic knees underwent TKA were subjected to this study. The mean age of surgery was 72.4 years old. Preoperative standing coronal deformity was 9.6 degrees in varus. TUG test results in less duration with faster ambulatory function. TUG (seconds) was measured at 3 time periods; pre-operatively, at hospital discharge and 1year after surgery. To standardize TUG recovery time during 1 year after TKA, we defined TUG recovery rate as the percentage of recovery time to the pre-operative TUG as shown in the following equation. TUG recovery rate (%) = (TUG pre-op –TUG 1y po) / TUG pre-op ×100. We also evaluated the knee stability at hospital discharge and 1year after surgery. The knee stability at extension and flexion were assessed by varus and valgus stress radiography using Telos (10kg) and stress epicondylar view with 1.5kg weight at the ankle respectively. Image analyzing software was used to measure joint separation distance (mm) at medial as medial joint opening (MJO) and at lateral as lateral joint opening (LJO) at both knee extension and flexion. (Fig.1). The sequential change of TUG was analyzed using repeated measures ANOVA (p<0.05). The influence of joint opening distances (MJO and LJO at extension and flexion) on TUG 1y po and TUG recovery rate were analyzed using simple linear regression analysis (p<0.05). Results. The mean TUGs were 13.4, 13.7 and 10.8 seconds pre-operatively, at hospital discharge and 1 year after TKA respectively. Significant decrease was found at 1 year after surgery. TUG pre-op did not show significant correlation to any joint openings. TUG 1y po was positively correlated with both flexion and extension MJO at hospital discharge. (Fig.2) TUG recovery rate negatively correlated to flexion-MJO at hospital discharge. (Fig.3). Discussions. The most interesting findings in the present study were that both flexion and extension MJO at hospital discharge were positively correlated with TUG 1y po and negatively correlated with TUG recovery rate. This indicated that early post-operative medial stability played an important role in the recovery of ambulatory function. The early post-operative medial instability would cause pain and deteriorate functional recovery after surgery. There is some disagreement regarding the importance of pursuing the perfect ligament balance, which would be more likely to result in medial instability. Consequently, surgeons should prioritize medial stability for better ambulatory functional recovery after TKA

INTRODUCTION. Thorough understanding and feedback of the post-operative implant position relative to the pre-operative anatomy is missing in today's clinical practice. However, three dimensional insights in the local under or oversizing of the implant can provide important feedback to the surgeon. For the knee for instance, to identify a shift in the sagittal joint line that potentially links to mid-flexion instability or to identify zones at risk for soft tissue impingement. Despite a proven inferior outcome, clinical post-operative implant evaluation remains primarily based on bi-planar, static 2D x-rays rather than 3D imaging. Along with the cost, a possible reason is the increased radiation dose and/or metal artifact scatter in computed tomography (CT) and/or magnetic resonance imaging (MRI). These detrimental effects are now avoided by using recently released x-ray processing software. This technique uses standard-of-care post-operative x-rays in combination with a pre-operative CT and 3D file of the implant to determine the implant position relative to the pre-operative situation. The accuracy of this new technique is evaluated in this paper using patient cases. Therefore, the obtained implant position is benchmarked against post-operative CT scans. MATERIALS & METHODS. Retrospectively, 19 patients were selected who underwent total knee arthroplasty and received pre- and post-operative CT of their diseased knee. The CT scans were performed with a pixel size of 0.39 mm and slice spacing of 0.60 mm (Somatom, Siemens, München, Germany). All patients underwent TKA surgery using the same bi-cruciate substituting total knee (Journey II, Smith&Nephew, Memphis, USA). Following surgery, standard bi-planar standing x-rays of the operated knee was additionally performed as standard of care. To evaluate the implant position relative to the pre-operative situation, the 3D implants are first positioned on the post-operative CT slices. Using Mimics (Materialise NV, Leuven, Belgium), the pre-operative bone was subsequently automatically matched onto the post-operative scan to identify the implant location relative to the reconstructed pre-operative bone. This has been independently repeated by three observers to assess the inter-observer variability. Second, the post-operative bi-planar x-rays are combined with the reconstructed pre-operative bone and 3D file of the implant. This combination is performed using the 2D-to-3D conversion integrated in the recently launched X-ray module of Mimics. This module uses a contour based registration method to determine the implant and bone position using the post-operative x-rays. For both reconstruction methods, the implant position has been evaluated in six degrees of freedom using an automated Matlab routine; resulting in three translations and three rotations. RESULTS. From the evaluated implant positions, the root mean square error was derived between subsequent measurements. For the CT reconstruction based inter-observer evaluation, the median RMS error for all degrees of freedom is below 1 mm and 1 degree for both the femoral and tibial implant. Comparing the reconstructed CT implant position with the 2D-to-3D reconstruction, the median RMS difference between the implant positions remains below 1 mm and 1 degree except for the distraction/compression component and the internal/external rotation of the component. DISCUSSION. On average, the RMS difference between the 2D-to-3D conversion and the reconstructed post-operative CT exceeds the inter-observer RMS difference obtained using reconstructed post-operative CT. The differences are in line with previous cadaveric studies using the same reconstruction technique. The largest differences are seen for the femoral and tibial internal/external rotation. However, the obtained values are still within reasonable limits according to a recent review by De Valk et al., who reported an inter-observer variation of 3° for the femur and 2° for the tibia. In addition, the 2D-to-3D conversion displays a larger difference for the distraction/compression component. Since a true, golden standard measurement is lacking in our tests, it is not clear whether this error is attributed to the CT imaging or the 2D-to-3D conversion. Given the low inter-observer variation for this degree of freedom, it is hypothesized that this discrepancy is linked to the finite slice spacing for the CT scans. Apart from the obtained accuracy, the use of the 2D-to-3D module has the advantage of significantly reducing the radiation dose with approx. a factor 20. In addition, the imaging procedure needs no more than the standard imaging required by clinical practice

Clinical, haematological or economic benefits of post-operative blood salvage with autologous blood re-transfusion have yet to be clearly demonstrated for primary total hip replacement. We performed a prospective randomised study to analyse differences in postoperative haemoglobin levels and homologous blood requirements in two groups of patients undergoing primary total hip replacement. A series of 158 patients was studied. In one group two vacuum drains were used and in the other the ABTrans autologous retransfusion system. A total of 58 patients (76%) in the re-transfusion group received autologous blood. There was no significant difference in the mean post-operative haemoglobin levels in the two groups. There were, however, significantly fewer patients with post-operative haemoglobin values less than 9.0 g/dl and significantly fewer patients who required transfusion of homologous blood in the re-transfusion group. There was also a small overall cost saving in this group

BACKGROUND. The need for post-operative manipulation under anesthesia (MUA) for stiffness after primary total knee arthroplasty is a frustrating complication that can lead to suboptimal outcomes if range-of-motion to a functional level is not regained. Implant morphology and kinematics, PCL imbalance, and soft-tissue balancing can all contribute to post-operative stiffness. Utilization of total knee arthroplasty components that replicate the native knee's medial ball and socket kinematics may lead to easier maintenance of flexion post-operatively compared to conventional components. PURPOSE. To determine if a medial pivot total knee arthroplasty design can reduce the need for post-operative MUA after primary total knee arthroplasty. METHODS. A retrospective chart review of primary total knee arthroplasties performed between 2013 and 2016 by a single fellowship-trained joint replacement surgeon was performed. Cases that met criteria for inclusion were: primary total knee arthroplasty, identifiable implant based on operative report and/or post-operative radiographs, immediate post-operative passive flexion against gravity of at least 110 degrees, and availability of post-operative follow-up notes documenting range-of-motion that was either satisfactory or necessitating need for MUA. The need for a MUA was deemed necessary if post-operative flexion was not beyond 90 degrees within six weeks of surgery. The percentage of patients requiring MUA for a group implanted with the EVOLUTION Medial Pivot System was compared to a group implanted with all other designs (Stryker Triathlon CR, PS, TS). RESULTS. One hundred fifty-six cases met criteria for inclusion and were reviewed. The Triathlon system was used predominantly in the first half of the study period and accounted for 65 (42%) of the cases performed. Six patients in this group underwent MUA and two patients required repeated MUA. An additional patient in the Triathlon group met the criteria for MUA but had other conditions which prevented the investigators from performing it. The percentage of patients who met the indication for MUA in the Triathlon group was 10.8%. The EVOLUTION system was used predominantly in the second half of the study period and accounted for 91 (58%) of the cases performed. There were two patients (2.2%) who met criteria for MUA and both patients subsequently underwent MUA. There was a statistically significant reduction in the number of patients meeting criteria for MUA in the EVOLUTION group compared with the Triathlon group (p=0.024). CONCLUSION. Utilization of a medial ball and socket design for primary total knee arthroplasty allows the polyethylene implant to control the position of the femur on the tibia. This design possibly allows for improved early maintenance of post-operative flexion, which may minimize the need for post-operative MUA. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Arthrofibrosis remains a dominant post-operative complication and reason for returning to the OR following total knee arthroplasty. Trauma induced by ligament releases during TKA soft tissue balancing and soft tissue imbalance are thought to be contributing factors to arthrofibrosis, which is commonly treated by manipulation under anesthesia (MUA). We hypothesized that a robotic-assisted ligament balancing technique where the femoral component position is planned in 3D based on ligament gap data would result in lower MUA rates than a measured resection technique where the implants are planned based solely on boney alignment data and ligaments are released afterwards to achieve balance. We also aimed to determine the degree of mechanical axis deviation from neutral that resulted from the ligament balancing technique. Methods. We retrospectively reviewed 301 consecutive primary TKA cases performed by a single surgeon. The first 102 consecutive cases were performed with a femur-first measured resection technique using computer navigation. The femoral component was positioned in neutral mechanical alignment and at 3° of external rotation relative to the posterior condylar axis. The tibia was resected perpendicular to the mechanical axis and ligaments were released as required until the soft tissues were sufficiently balanced. The subsequent 199 consecutive cases were performed with a tibia-first ligament balancing technique using a robotic-assisted TKA system. The tibia was resected perpendicular to the mechanical axis, and the relative positions of the femur and tibia were recorded in extension and flexion by inserting a spacer block of appropriate height in the medial and lateral compartments. The position, rotation, and size of the femoral component was then planned in all planes such that the ligament gaps were symmetric and balanced to within 1mm (Figure 1). Bone resection values were used to define acceptable limits of implant rotation: Femoral component alignment was adjusted to within 2° of varus or valgus, and within 0–3° of external rotation relative to the posterior condyles. Component flexion, anteroposterior and proximal-distal positioning were also adjusted to achieve balance in the sagittal plane. A robotic-assisted femoral cutting guide was then used to resect the femur according to the plan (Figure 2). CPT billing codes were reviewed to determine how many patients in each group underwent post-operative MUA. Post-operative mechanical alignment was measured in a subset of 50 consecutive patients in the ligament balancing group on standing long-leg radiographs by an independent observer. Results. Post-operative MUA rates were significantly lower in the ligament balancing group (0.5%; 1/199) than in the measured resection group (3.9%; 4/102), p=0.051. 91.3% (42/46) of knees were within 3° and 100% (46/46) were within 4° of neutral alignment to the mechanical axis post-operatively in the ligament balancing group. Conclusions. Gap driven femoral based planning in TKA resulted in a significantly lower post-operative manipulation rate than in the measured resection approach, while maintaining acceptable overall alignment to the mechanical axis

Aim. Perioperative hyperglycemia has many etiologies including medication, impaired glucose tolerance, uncontrolled diabetes mellitus (DM), or stress, the latter of which is common to post-surgical patients. This acute hyperglycemia may impair the ability of the host to combat infection. 1. Our study aims to investigate if post-operative day 1 (POD1) blood glucose level is associated with complications, including periprosthetic joint infection (PJI), after total joint arthroplasty (TJA) and to determine a threshold for glycemic control that surgeons should strive for during a patient's hospital stay. Method. A single-institution retrospective review was conducted on 24,857 primary TJAs performed from 2001–2015. Demographics, Elixhauser comorbidities, laboratory values, complications and readmissions were collected. POD1 morning blood glucose levels were utilized and correlated with PJI, as defined by the Musculoskeletal Infection Society criteria. The Wald test was used to determine the influence of covariates on complication rate. An alpha level of 0.05 was used to determine statistical significance. Results. The rate of PJI significantly increased linearly from blood glucose levels of 115 mg/dL onwards. We determined that blood glucose (OR 1.004, 95% CI: 1.001–1.006, p=0.001), male gender (OR 1.480, 95% CI: 1.185–1.848, p=0.001), body mass index (OR 1.049, 95% CI: 1.033–1.065, p<0.001), operative time (OR 1.004, 95% CI: 1.001–1.007, p=0.006), length of stay (OR 1.059, 95% CI: 1.038–1.080, p<0.001), post-operative hematocrit (OR 0.751, 95% ci: 0.621–0.909, p=0.003), peripheral vascular disease (OR 1.942, 95% CI: 1.042–3.617, p=0.037), liver disease (OR 2.576, 95% CI: 1.344–4.935, p=0.004), rheumatic disease (OR 1.991, 95% CI: 1.266–3.132, p=0.003), and alcohol abuse (OR 2.588, 95% CI: 1.096–6.110, p=0.030) were associated with PJI. The Youden index was used to determine an optimal blood glucose threshold of 132 mg/dL to reduce the likelihood of PJI. The PJI rate in the entire cohort was 1.59% (1.46% in non-diabetics compared to 2.39% in diabetics, p=0.001). Diabetics did not have an association between blood glucose level and PJI (OR 1.002, 95% CI: 0.998–1.006, p=0.331), although there was a linear trend for postoperative glucose predicting PJI. Conclusions. The relationship between POD1 blood glucose levels and PJI increased linearly, with an optimal cut off of 132 mg/dL. Immediate and strict post-operative glycemic control is critical in reducing post-operative complications, and we demonstrate that even mild hyperglycemia is significantly associated with PJI

Introduction. To achieve well aligned and balanced knee is essential for the post-operative outcome in total knee arthroplasty (TKA). Gap balancing technique can adjust the bone cut depending on the soft tissue balance in addition to soft tissue releases. Therefore, gap balancing technique would be more advantageous in soft tissue balance comparing to measured resection technique (MRT) in which soft tissue balancing relayed on soft tissue releases alone. Nevertheless, the influence of surgical technique on the post-operative knee stability has not been fully investigated. Objective. We introduced a new surgical technique (medial gap technique: MGT) according to modified gap technique regarding medial knee stability as important. The intra-operative soft tissue balance and post-operative knee stability were compared between MGT and MRT in posterior-stabilized (PS) TKA for varus type osteoarthritic knees. Materials & Methods. Sixty varus type osteoarthritis knees were involved in this study. PS type TKAs (NexGen LPS flexR) were performed using MGT in 30 knees (MGT group) and MRT in 30 knees (MRT group). The extension gap was made in the same manners in both groups. Both femoral and tibial bone cuts were perpendicular to the mechanical axis. Medial soft tissue releases were limited until the spacer block with the thickness corresponding to the resected lateral tibial condyle could be inserted. After extension gap was prepared, OFR-tensorR was used to assess soft tissue balance (center gap, varus angle) at extension and flexion prior to posterior femoral condyle bone resection. Both differences of the center gap and varus angle between at extension and flexion were calculated and used for size selection and external rotation angle of femoral component in MGT. The final joint component gaps were evaluated using OFR-tensorR with both femoral trial in place and patello-femoral joint reduced at 0, 10, 30, 45, 60, 90, 120 and 135 degrees of flexion. Quantitative stress radiographies were performed at 1 month, 6 months and 1 year post-operatively to assess joint stability. Joint opening distance (mm) at both medial and lateral joint compartment were measured with knee extension and flexion. Each parameter was compared between MGT and MRT group using unpaired t-test (p<0.05). Results. Pre-operative factors showed no significant differences between 2 groups. The joint component gaps were significantly larger in MRT group from 45 to 135 degrees of flexion (Fig.1). The joint opening at the lateral compartment was significantly larger than medial at both knee extension and flexion in both groups. The joint openings were significantly larger bilaterally in MRT group comparing to MGT group at both extension and flexion (Fig.2, 3). Discussions. Medial instability has been reported as a possible reason for the persistent knee pain after TKA in the varus knees. We proposed a new surgical technique (MGT) not to deteriorate medial stability and allow lateral looseness in TKA. Post-operative knee stability was superior in MGT group comparing to MRT group from one month to one year after surgery. The difference of the intra-operative soft tissue balance might play an important role on the post-operative knee stability

TKA is one of the most common orthopaedic operations performed worldwide and it is largely successful in pain relief and functional recovery. However, when pain persists post-operatively the thorough evaluation must be instituted. Extra-articular causes of knee pain include; hip pathology, lumbar spine degenerative disease or radicular symptoms, focal neuropathy, vascular disease, and chronic regional pain syndrome. Intra-articular causes of knee pain: infection, crepitation/ clunk, patella osteonecrosis, patella mal-tracking, soft tissue imbalance, malalignment, arthrofibrosis, component loosening, implant wear, ilio-tibial band irritation, and bursitis. Other causes of pain to rule out are component overhang with soft tissue irritation, recurrent hemarthrosis secondary to synovial impingement or entrapment, non-resurfaced patella, and metal sensitivity. A careful history may reveal previous knee surgeries with delayed healing or prolonged drainage, chronology of sign and symptoms, co-morbid medical conditions, jewel or metal sensitivity. Physical exam should help with specific signs in the operated knee. Targeted local anesthetic blocks are helpful and response to lumbar sympathetic blocks determines presence of CRPS. Lab tests are important: ESR, CRP, WBC, aspiration with manual cell count and diff, leukocyte esterase dipstick, RA titers, metal derm patch testing, nuclear scans, CT best for rotational malalignment,, and MARS MRI. More recently patient satisfaction as an outcome measure has shown TKA results not satisfactory in 11 – 18% of patients. A discordance of patient vs. surgeon satisfaction exists so the following factors may help improve this: correct patient selection, establishing and correlating surgeon-patient expectations, peri-operative optimisation of patient comorbidities to help avoid preventable complications, use of pre- and post-operative pathways. Satisfaction rates can best be improved by addressing the previous points with patients prior to TKA surgery

Purpose. Total knee arthroplasty (TKA) is one of the most successful surgeries with respect to relieving pain and restoring function of the knee. However, some studies have reported that patients are not always satisfied with their results after TKA. The aim of this study was to determine which factors contribute to patient's satisfaction after TKA. Methods. We evaluated 69 patients who had undergone 76 primary TKAs between March 2012 and June 2013, and assessed patient- and physician- reported scores using the 2011 Knee Society Scoring System and clinical variables before and after TKAs. We determined the correlation between patient satisfaction and clinical variables. Results. The mean (SD) pre-operative score was 8.2 (4.9) for symptoms, 11.5 (4.5) for patient's satisfaction, 13.1 (2.2) for patient's expectations, and 35.4 (18.2) for functional activities. The mean (SD) post-operative score was 16.3 (5.0) for symptoms, 20.7 (6.4) for patient's satisfaction, 9.1 (2.3) for patient's expectations, and 47.4 (19.6) for functional activities. We found that physician- reported scores were higher than patient- reported scores, and improvement in patient- reported scores was lower than that of physician- reported scores following TKA. We did not found a correlation between any pre-operative variables including expectation and post-operative satisfaction. Post-operative symptoms (r=0.51, p<0.01) and functions (r=0.39, p<0.01) correlated with post-operative satisfaction. The predictors of patient dissatisfaction after TKA were remaining symptoms and low postoperative activities. Conclusions. Our study demonstrates that to relieve pain and to restore activities is important for increasing patient satisfaction after TKA. The 2011 Knee Society Scoring System allows surgeons to appreciate differences in the priorities of patients with TKA

Background. The accurate positioning of the total knee arthroplasty affects the survival of the implants(1). Alignment of the femoral component in relation to the native knee is best determined using pre- and post-operative 3D-CT reconstruction(2). Currently, the scans are visualised on separate displays. There is a high inter- and intra-observer variability in measurements of implant rotation and translation(3). Correct alignment is required to allow a direct comparison of the pre- and post-operative surfaces. This is prevented by the presence of the prostheses, the bone shape alteration around the implant, associated metal artefacts, and possibly a segmentation noise. Aim. Create a novel method to automatically register pre- and post-operative femora for the direct comparison of the implant and the native bone. Methods. The concept is to use post-operative femoral shaft segments free of metal noise and of surgical alteration for alignment with the pre-operative scan. It involves three steps. Firstly, using principal component analysis, the femoral shafts are re-oriented to match the X axis. Secondly, variants of the post-operative scan are created by subtracting 1mm increments from the distal femoral end (Fig1). Thirdly, an iterative closest point algorithm is applied to align the variants with the pre-operative scan. For exploratory validation, this algorithm was applied to a mesh representing the distal half of a 3D scanned femur. The mesh of a prosthesis was blended with the femur to create a post-operative model. To simulate a realistic environment, segmentation and metal artefact noise were added. For segmentation noise, each femoral vertex was translated randomly within +−1mm,+−2mm,+−3mm along its normal vector. To create metal artefact random noise was added within 50 mm of the implant points in the planes orthogonal to the shaft. The alignment error was considered as the average distance between corresponding points which are identical in pre- and post-operative femora. Results. Figure 2 shows, that when the implant zone is completely ignored, the error reaches a minimum plateau to below 1mm level. Different levels of segmentation noise had low impact on error value. Conclusions. These preliminary results obtained within a simulated environment show that by using only the native parts of the femur, the algorithm was able to automatically register the pre- and post-operative scans even in presence of the implant. Its application will allow visualisation of the scans on the same display for the direct comparison of the perioperative scans. This method requires further validation with more realistic noise models and with patient data. Future studies will have to determine if correct alignment has any effect on inter- and intra-observer variability. For figures, please contact authors directly.

Introduction. Navigation of acetabular component orientation is still not commonly performed despite repeated studies that show that more than ½ of acetabular components placed during hip arthroplasty are significantly mal-positioned and that intra-operative radiographic assessment is unreliable. The current study uses postoperative CT to assess the accuracy of a smart mechanical navigation instrument system for cup alignment. Patients and Methods. Thirty seven hip replacements performed using a smart mechanical navigation device (the HipXpert System) had post-operative CT studies available for analysis. These post-operative CT studies were performed for pre- operative planning of the contralateral side, one to three years following the prior surgery. An application specific software module was developed to measure cup orientation using CT (HipXpert Research Application, Surgical Planning Associates Inc., Boston, Massachusetts). The method involves creation of a 3D surface model from the CT data and then determination of an Anterior Pelvic Plane coordinate system. A multiplaner image viewer module is then used to create an image through the CT dataset that is coincident with the opening plane of the acetabular component. Points in this plane are input and then the orientation of the cup is calculated relative to the AP Plane coordinate space according to Murray's definitions of operative anteversion and operative inclination. The actual cup orientation was then compared to the goal of cup orientation recorded when the surgery was performed using the system for acetabular component alignment. Results. For the thirty seven hips replacements, mean operative anteversion error was 1.1 degrees (SD 3.6, range −5.5 to 8.2). Mean operative inclination error was − 1.7 degrees (SD 3.0, range −8.0 to 5.6). There were no outliers in either anteversion or inclination. Conclusion. The current study demonstrates that the mechanical navigation system produces accurate cup alignment results as measured by post-operative CT and confirms the prior accuracy study performed using 2D/3D matching. This improved accuracy compared to robotic systems may be due to the wide-based nature of the docking mechanism and the elimination of the cumulative errors of registration and tracking inherent to more complex systems

Background. Component positioning in total hip arthroplasty (THA) is critical to achieve optimal patient outcomes. Recent literature has shown acetabular component positioning may be inaccurate using traditional techniques. Robotic-assisted THA is a recent platform introduced to decrease the risk of malpositioned components. However, to date, a paucity of data is available comparing the intra-operative component position generated by the navigation system to post-operative radiographs. Purpose. The purpose of this study was to compare the component position measurements of a navigation system, used during robotic-assisted THA, to component position measurements obtained on post-operative radiographs. Methods. Intra-operative component position measurements for acetabular inclination, acetabular anteversion, leg length change, and offset change for 145 patients were recorded. Pre-operative and post-operative radiographs of the same 145 patients were then measured for the same parameters. A comparison of component position provided by the navigation system and radiographic data was then performed. Sub-group analyses of posterior and direct anterior measurements were performed. Results. Correlation between the navigation system and post operative radiographs was within 10° for 95.9% of cases for inclination and 96.6% for anteversion. Correlation within 10 mm of radiographic-measured values occurred in 97.7% of cases for change in leg length and 94.0% for change in global offset. 100% of the cases ended up with radiographic leg length discrepancy of less than 10 mm. Conclusion. The intra-operative component position data obtained from the navigation system utilized during robotic-assisted THA demonstrated correlated well with component position data obtained from radiographs

Objective. The goal of total knee arthroplasty (TKA) is to achieve a stable and well-aligned tibiofemoral and patello-femoral (PF) joint, aiming at long-term clinical patient satisfaction. The surgical principles of both cruciate retaining (CR) and posterior stabilized (PS) TKA are accurate osteotomy and proper soft tissue balancing. We have developed an offset-type tensor, and measured intra-operative soft tissue balance under more physiological joint conditions with femoral component in place and reduced PF joint. In this study, we measured intra-operative soft tissue balance and assessed the post-operative knee joint stability quantitatively at one month, six months and one year after surgery, and compared these parameters between CR and PS TKAs. Material and Method. Sixty patients with varus osteoarthritis of the knee underwent TKAs (30 CR TKAs: CR and 30 PS TKAs: PS). Mean varus deformity in standing position was 11.1 degrees in CR, and 12.6 degrees in PS. All TKAs were performed by a single surgeon with measured resection technique. The external rotation of posterior femoral condyle osteotomy was performed according to surgical epicondylar axis in pre-operative CT. We measured intra-operative soft tissue balance using an offset-type tensor with 40 lbs of joint distraction force at 0, 10, 30, 45, 60, 90, 120 and 135 degrees of flexion. The joint component gap (mm) and varus angle (degrees) were measured at each flexion angles. One month, six months and one year after surgery, we evaluated the knee stability at extension by varus and valgus stress radiography using Telos (10kg) and at flexion by epicondylar view with 1.5kg weight at the ankle. We measured joint separation distance at medial as medial joint looseness (MJL) and at lateral as lateral joint looseness (LJL). Intra-operative measurements and post-operative joint stabilities were compared between CR and PS using unpaired t-test. The change of joint looseness in each group was analyzed using repeated measures ANOVA. Result. Joint gap kinematics was different between CR and PS (Fig. 1). Joint component gap in PS were significantly higher than CR from 30 to 120 degrees of flexion. Post-operative MJL and LJL changes are shown in figure 2 with knee extension, and in figure 3 with knee flexion. PS showed significantly higher joint looseness than CR at both extension and flexion at three time periods after surgery. There were no significant post-operative changes in both MJL and LJL in CR and PS TKAs. Discussion. We found significant differences in gap kinematics and also in the one year post-operative joint stability between CR and PS. The different characteristics of the intra-operative soft tissue balance between CR and PS TKAs would be a possible reason for the differences in the post-operative knee stability. Our results suggested that TKAs performed by measured resection technique have significantly higher joint stability with CR TKAs comparing to PS TKAs. These findings would be important issues in choosing prosthesis and surgical technique. Conclusion. With measured resection technique, CR TKAs had more consistent joint gap kinematics and higher joint stability after surgery comparing to PS TKAs

Objective. Although both accurate component placement and adequate soft tissue balance have been recognized as essential surgical principle in total knee arthroplasty (TKA), the influence of intra-operative soft tissue balance on the post-operative clinical results has not been well investigated. In the present study, newly developed TKA tensor was used to evaluate soft tissue balance quantitatively. We analyzed the influence of soft tissue balance on the post-operative knee extension after posterior-stabilized (PS) TKA. Materials and Methods. Fifty varus type osteoarthritic knees implanted with PS-TKAs were subjected to this study. All TKAs were performed using measured resection technique with anterior reference method. The thickness of resected bone fragments was measured. Following each bony resection and soft tissue releases, we measured soft tissue balance at extension and flexion of the knee using a newly developed offset type tensor. This tensor device enabled quantitative soft tissue balance measurement with femoral trial component in place and patello-femoral (PF) joint repaired (component gap evaluation) in addition to the conventional measurement between osteotomized surfaces (osteotomy gap evaluation). Soft tissue balance was evaluated by the center gap (mm) and ligament balance (°; positive in varus) applying joint distraction forces at 40 lbs (178 N). Active knee extension in spine position was measured by lateral X-ray at 4 weeks post-operatively. The effect of each parameter (soft tissue balance evaluations, thickness of polyethylene insert and resected bone) on the post-operative knee extension was evaluated using simple linear regression analysis. P<0.05 was considered statistically significant. Results. The thickness of resected bone, flexion center gap and ligament balance at extension and flexion had no correlations to the knee extension angle. Thickness of polyethylene insert correlated positively to knee extension (r=0.38, p=0.007). Significant positive correlation were found between extension center gap in both osteotomy and component gap evaluation to the post-operative knee extension. The coefficient of correlations were 0.33 (p=.02) with osteotomy gap and 0.47 (p=0.0007) with component gap evaluation. Discussion and Conclusion. In the present study, extension center gap was found to positively correlate to the early post-operative knee extension. The extension center gap could be considered as the summation of the simultaneous gap from bone resections and the elongation of soft tissue envelope under joint distraction force applied by tensor. The soft tissue with the lower stiffness would be elongated more, and result in the larger center gap. Accordingly, the stiffness of the soft tissue envelope might play an important role on the magnitude of extension center gap and the post-operative knee extension. Furthermore, the center gap in component gap evaluation had higher coefficient of correlation comparing to that in osteotomy gap. Proposed component gap evaluation in soft tissue balance measurement might be more physiological and relevant to the joint condition after TKA, and useful to predict post-operative clinical results

The aim of an anterior cruciate ligament (ACL) reconstruction is to regain functional stability of the knee following ACL injury, ideally allowing patients to return to their pre-injury level of activity. The purpose of this study was to assess clinical, functional and patient-centered outcomes a minimum of 1-year following ACL reconstruction. This study assessed for relationships between post-operative ACL graft laxity, functional testing performance, and scores on the ACL Quality of Life (ACL-QOL) questionnaire. A prospective cohort study design (n = 1938) was used to gather data on clinical laxity, functional performance and quality of life outcomes. Post-operative ACL laxity assessment using the Lachman and Pivot-shift tests was completed independently on each patient by a physiotherapist and an orthopaedic surgeon at a minimum of 12-months post-operatively. A battery of functional tests was performed including single leg balance, single leg landing, 4 single-leg hop tests, and tuck jumps. The hop tests provided a comparative assessment of limb-to-limb function including a single hop for distance, a 6m timed hop, a triple hop for distance, and a triple crossover hop. Patients com¬pleted the ACL-QOL at the 12-month and 24-month post-operative appointments. Descriptive and demographic data were collected for all patients. The degree and frequency of post-operative laxity was calculated. A Pearson r correlation coefficient was employed to determine the relationship between the presence of post-operative laxity and the ACL-QOL scores, between the battery of functional tests and the ACL-QOL scores, as well as between the functional tests and the laxity assessments. Data was gathered for 1512/1938 patients (78%). At clinical assessment a minimum of 1-year post-operatively, 13.2% of patients demonstrated a positive Lachman and/or Pivot-shift test. The mean ACL-QOL score for patients with no ACL laxity was 80.8/100, for patients with a positive Lachman or Pivot-shift test the mean score was 72.3/100, and for patients with both positive Lachman and Pivot-shift tests the score was 66.9/100. Pearson r correlation coefficient demonstrated a significant relationship between the presence of ACL graft laxity and ACL-QOL score (p < 0.05). Statistically significant correlations were evident between all of the operative limb single-leg hop tests and the post-operative ACL-QOL scores (p < 0.05). Statistically significant correlations were evident between the operative limb triple-hop tests and presence of ACL graft laxity (p < 0.05). Patients with clinically measurable ACL graft laxity demonstrate lower ACL-QOL scores as well as lower performance on a battery of functional tests. The disease-specific outcome measure was strongly correlated to the patient's ability to perform single-limb functional tests, indicating that the ACL-QOL score accurately predicted level of function

Introduction. Navigation of acetabular component orientation is still not commonly performed despite repeated studies that show that more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned. 1. The current study uses postoperative CT to assess the accuracy of a smart mechanical navigation instrument system for cup alignment. Patients and Methods. Thirty seven hip replacements performed using a smart mechanical navigation device (the HipXpert System) had post-operative CT studies available for analysis. These post-operative CT studies were performed for pre-operative planning of the contralateral side, one to three years following the prior surgery. An application specific software module was developed to measure cup orientation using CT (HipXpert Research Application, Surgical Planning Associates Inc., Boston, Massachusetts). The method involves creation of a 3D surface model from the CT data and then determination of an Anterior Pelvic Plane coordinate system. A multiplaner image viewer module is then used to create an image through the CT dataset that is coincident with the opening plane of the acetabular component. Points in this plane are input and then the orientation of the cup is calculated relative to the AP Plane coordinate space according to Murray's definitions of operative anteversion and operative inclination. The actual cup orientation was then compared to the goal of cup orientation recorded when the surgery was performed using the system for acetabular component alignment. Results. For the thirty seven hips replacements, mean operative anteversion error was 1.1 degrees (SD 3.6, range −5.5 to 8.2). Mean operative inclination error was −1.7 degrees (SD 3.0, range −8.0 to 5.6). There were no outliers in either anteversion or inclination. Conclusion. The current study demonstrates that the mechanical navigation system produces accurate cup alignment results as measured by post-operative CT and confirms the prior accuracy study performed using 2D/3D matching. This improved accuracy compared to robotic systems. 4. may be due to the wide-based nature of the docking mechanism and the elimination of the cumulative errors of registration and tracking inherent to more complex systems

Introduction. Navigation of acetabular component orientation is still not commonly performed despite repeated studies that show that more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned1. The current study uses postoperative CT to assess the accuracy of a smart mechanical navigation instrument system for cup alignment. Patients and Methods. Twenty nine hip replacements performed using the HipXpert Navigation System had post-operative CT studies available for analysis. These post-operative CT studies were performed for pre-operative planning of the contralateral side, one to three years following the prior surgery. The patients included 17 men and 11 women. An application specific software module was developed to measure cup orientation using CT (HXR Application 1.3 Surgical Planning Associates Inc., Boston, Massachusetts). The method involves creation of a 3D surface model from the CT data and then determination of an Anterior Pelvic Plane coordinate system. A multiplaner image viewer module is then used to create an image through the CT dataset that is coincident with the opening plane of the acetabular component. Points on this plane are input and then the orientation of the cup is calculated relative to the AP Plane coordinate space according to Murray's definitions of operative anteversion and operative inclination. The actual cup orientation was then compared to the goal of cup orientation recorded when the surgery was performed using the HipXpert navigation system for acetabular component alignment. Results. Mean operative anteversion error was 1.7 degrees (SD 3.4, range −6.5 to 8.5). Mean operative inclination error was −2.3 degrees (SD 3.1, range −8.9 to 3.9). There were no outliers in either anteversion or inclination. Conclusion. The current study demonstrates that the mechanical navigation system produces accurate cup alignment results as measured by post-operative CT and confirms the prior accuracy study performed using 2D/3D matching. This accuracy, compared to traditional navigation and robotic systems, may be due to the wide-based nature of the docking mechanism and the elimination of the cumulative errors of registration and tracking inherent to more complex systems

Acute peri-operative blood loss warranting transfusion is a frequent consequence of major joint replacement (TJR) surgery. Significant peri-operative anemia can contribute to hypotension, dyspnea, coronary ischemia and other peri-operative medical events that can result in increased risk of peri-operative complications, readmissions and impair the patient's ability to mobilise after surgery resulting in a longer length of stay (LOS) and increase skilled nursing facility (SNF) utilization. The risks associated with allogeneic blood transfusions (ABT) administered to treat symptomatic peri-operative anemia are numerous and extend beyond the concerns of transmission of communicable disease (HIV, hepatitis, other). Patients receiving ABTs have been shown to have a longer hospital LOS, higher risk of infection, and higher mortality after TJR than those who do not require transfusion after surgery. As a result, many different pre-operative, peri-operative and post-operative strategies have been utilised to minimise peri-operative blood loss and transfusion need for patients undergoing TJR. Several studies have shown that the strongest predictor of the need for ABT in the TJR patient is the pre-operative hematocrit (Hct). As a result, all patients with unexplained pre-operative anemia should be evaluated for an underlying cause prior to elective TJR surgery. In recent years, focus has shifted towards peri-operative reduction of blood loss with the use of pharmacologic agents like tranexamic acid (TXA). These agents work by inhibiting fibrinolysis and activating plasminogen. Numerous studies have shown that TXA given IV, applied topically into the surgical wound or given orally have been shown to reduce peri-operative bleeding and ABT after both THA and TKR. Regardless of route of administration, all appear to be more efficacious and considerably more cost-effective in reducing the need for ABT than other methods discussed previously. Despite concerns about the potential increased thromboembolic risk in patients undergoing TJR, there does not appear to be any conclusive evidence suggesting an increased risk of venous thromboembolic disease (VTED) in TJR patients who receive peri-operative TXA. Although it may be unnecessary, many TJR surgeons still, however, avoid use of TXA in patients with a past history of VTED, stroke, coronary artery disease (including coronary stents), renal insufficiency, hypercoagulable state and seizure disorder. The use of topical TXA may be safer in some of these high risk patients since systemic absorption is minimal when administered via this route. Although the optimal method of administration (IV, topical, oral or combined) has not yet been determined based on safety, cost and reduction of need for ABT, incorporation of tranexamic acid into a blood conservation program is clearly the standard of care for all TJR programs that should nearly eliminate the need for ABT for patients undergoing TJR

The United States is in the midst of an opioid epidemic, with the World Health Organization reporting that American's consume 99% of the world's supply of hydrocodone and 83% of the world's oxycodone. Additionally, pre-operative opioid use has been associated with worse clinical outcomes and higher rates of complications following TKA. This is especially important in the TKA population given that approximately 15% of patients are either dissatisfied or very dissatisfied at least one year after their TKA procedure. Given the concerning rise is opioid use the American Academy of Orthopaedic Surgeons (AAOS) has recently released an information statement with practice recommendations for combating this excessive and inappropriate opiate use. However, little is known regarding peri-operative opioid use for TKA patients. Therefore, the purpose of this study was to: 1) identify rates of opioid use prior to primary TKA, 2) evaluate post-operative trends in opioid use throughout the year following TKA and 3) identify risk factors for prolonged opioid use following TKA. Overall, 31% of TKA patients are prescribed opioids within 3-months prior to TKA; this percentage has increased over 9% during the years included in this study. Pre-operative opioid use was most predictive of increased refills of opioids following TKA, however, other intrinsic patient characteristics were also predictive of prolonged opioid use. These characteristics remained predictive after controlling for opioid user status. The increasing rates of opioid prescribing prior to TKA are concerning, especially given literature concluding opioids have minimal effect on pain or function in patients with osteoarthritis and pre-operative opioid use is associated with poor outcomes and more complications following TKA. This data provides an important baseline for opioid use trends following TKA that can be used for future comparison and identifies risk factors for prolonged use that will be helpful to prescribers as the AAOS works to decreased opioid use, misuse and abuse within the United States. Our data on THA and unicompartmental arthroplasty is similar with an increase in pre-THA use of 9% with 38% receiving narcotics within 3 months of surgery and continued use in opioid users (9 times non-opioid users at 12 months)

Introduction. Recently, there are increasing literatures of the in vivo kinematics of total knee arthroplasty (TKA). Those previous studies have been reported in regard of either intra-operative kinematics or post-operative kinematics. However, the direct correlation between intra- and post-operative kinematics of TKA has not been revealed. There are no evidences that intra-operative kinematics can lead to post-operative kinematics. Purpose. The purpose of this study is to verify the direct correlation between intra- and post-operative kinematics of TKA. Materials and Methods. We investigated 6 knees (1 male and 4 females; mean age, 74.5 years [range, 69 to 85 years]) implanted with cruciate-retaining TKA caused by osteoarthritis. The one operator evaluated intra-operative passive un-loading kinematics after implanting all components using navigation system by hand throughout knee flexion. The postoperative active loading kinematics was obtained by fluoroscopic images and was analyzed by the 2D/3D registration technique. Both kinematics showed axial rotation angles at 10°intervals of knee flexion. Though flexion angle using navigation system was decided on mechanical axes of femur and tibia, flexion angle using 2D/3D matching method was based on the position of femoral and tibial components. Because the gap of knee flexion angle between both kinematics was approximately 7.3°from postoperative radiographs, we corrected 10°addition to each flexion angle in postoperative kinematics. Moreover, after axial rotational position was changed to axial rotational variation within each interval, we investigated the correlation directly. We noticed also that while the intra-operative kinematics showed axial rotation of tibia against femur showed, the post-operative kinematics showed that of femur against tibia. So, post-operative axial rotations were reversed. Results. Axial rotational patterns between intra- and post-operative kinematics, which tibial component against femoral component rotated externally in the initial flexion and switched internally from the mid-flexion to the terminal flexion, demonstrated high correlation with 0.786 of Pearson correlation coefficient (p<0.05). Discussion. To the best of our knowledge, there is no past report of the direct comparison between the in vivo kinematics of TKA intra-operatively and postoperatively. This is a first study to verify the direct correlation between them. In this study, they depended on different indicator, therefore the comparison of the volumes of rotational angles was not beneficial. We investigated the transition patterns of rotational angle variations at every 10°of knee flexion and the correlation between the intra- and post-operative kinematics was excellent in TKA in despite of un-loading and loading. Though this result doesn't always demonstrated high correlation for all cases, it was noted that intra-operative kinematic evaluation using navigation system is useful information to be referred. Conclusion. We believe that the analysis of intra-operative kinematics using knee navigation system in TKAs will enable to bring us the useful information to predict the postoperative kinematics