Objective. In this study, we aim to compare total bone amount extracted in total knee arthroplasty in implant design and the bone amount extracted through intercondylar femoral notch cut. Material and Method. In this study, we implemented 10 implants on a total of 50 sawbones from 5 different total knee arthroplasty implant brands namely Nex-Gen Legacy (Zimmer, Warsaw, IN, USA), Genesis 2 PS (Smith&Nephew, Memphis, TN, USA), Vanguard (Biomet Orthopedics Inc., Warsaw, IN, USA), Sigma PS (De Puy, Johnson&Johnson, Warsaw, IN, USA), Scorpio NRG PS (Stryker Co., Kalamazoo, USA). Equal or the closest sizes of each brand on anteroposterior plane were selected, and cuts were made following standard technique(see Fig 1 and 2). Extracted bone pieces were measured in terms of volume and length on three planes, and statistically analysed. The volume of all pieces available after each femoral incision was measured according to Archimedes’ principles. Furthermore, the volume of each intercondylar femoral notch pieces was measured separately from other pieces but with the same method. The measurement of intercondylar femoral notch pieces on 3 planes (medial-lateral, anterior-posterior, superior-inferior) was made using Kanon slide gauge (Ermak Ltd, Istanbul, TR). Femoral notch incision pieces were scanned with CAD/CAM technology using three-dimensional scanner 1 SeriesTM (Dental Wings Inc, Montreal, QC, Canada), and the measurements were confirmed with DWOS CAD 4.0.1 software (Dental Wings Inc, Montreal, QC, Canada)(see figure 3a-e). The volume of 10 intercondylar femoral notch pieces performed through the set of each brand was averaged, and considered as the incision volume of that particular brand. Results. The comparison made by excluding femoral notch cuts did not produce any statistically significant difference between the amounts of bone extracted. The least volumetric value measured in extracted intercondylar femoral notch cut was obtained using Vanguard (3,6±0,4 cm3). The gradually increasing volumes were obtained from Nex-Gen (3,7±0,5 cm3), Sigma (5,7±0,4 cm3), Genesis 2 (6,3±0,3 cm3) and Scorpio NRG (6,7±0,7 cm3), respectively. There was no statistical difference between Genesis 2 and Scorpio NRG, and between Nex-Gen and Vanguard. Conclusion. There are significant differences among implant designs in terms of preserving bone stock, and much of these differences stems from intercondylar femoral notch incision

Patellofemoral complaints are the common and nagging problem after total knee arthroplasty. Crepitus occurs in 5% to over 20% of knee arthroplasty procedures depending on the type of implant chosen. It is caused by periarticular scar formation with microscopic and gross findings indicating inflammatory fibrous hyperplasia. Crepitus if often asymptomatic and not painful, but in some cases can cause pain. Patella “Clunk Syndrome” is less common and represents when the peripatella scarring is abundant and forms a nodule which impinges and “catches” on the implant's intercondylar notch. Patella Clunk was more common with early PS designs due to short trochlear grooves with sharp transition into the intercondylar notch. Clunks are very infrequent with modern PS implants. This syndrome has been reported in CR implants as well. Thorough debridement of the synovium and scarring at the time of arthroplasty is thought to reduce the occurrence of crepitus and clunks. Larger patella with better coverage of the cut bone may also be helpful. The diagnosis can be made on history and physical exam. X-rays are also helpful to assess patella tracking. MRI or ultrasound can be used to identify and confirm the diagnosis, but this is not mandatory. Painful crepitus and clunk syndrome that fail conservative management of NSAIDS and physical therapy may require surgery. Both crepitus and clunk can be treated with arthroscopic removal of the peripatella scar. Patella maltracking should also be assessed and treated. While recurrence may occur, it is uncommon

Patellofemoral complaints are the common and nagging problem after Total Knee Arthroplasty. Crepitus occurs in 5% to over 20% of knee arthroplasty procedure depending on the type of implant chosen. It is caused by periarticular scar formation with microscopic and gross findings indicating inflammatory fibrous hyperplasia. Crepitus if often asymptomatic and not painful, but in some cases can cause pain. Patella “Clunk Syndrome” is less common and represents a when the peripatella scarring is abundant and forms a nodule which impinges and “catches” on the implants intercondylar notch. Patella Clunk was more common with early PS designs due to short trochlear grooves with sharp transition into the intercondylar notch. Clunks are very infrequent with modern PS implants. This Syndrome has been reported in CR implants as well. Thorough debridement of the synovium and scarring at the time of Arthroplasty is thought to reduce the occurrence of crepitus and clunks. Larger patella with better coverage of the cut bone may also be helpful. The diagnosis can be made on history and physical exam. X-rays are also helpful to assess patella tracking. MRI or ultrasound can be used to identify and confirm the diagnosis but this is not mandatory. Painful crepitus and clunk syndrome that fail conservative management of NSAIDS and physical therapy may require surgery. Both crepitus and clunk can be treated with arthroscopic removal of the peripatella scar. Patella maltracking should also be assessed and treated. While recurrence may occur it is uncommon

Patellofemoral arthroplasty (PFA) has higher revision rates than total knee arthroplasty (TKA) [Van der List, 2015; Dy, 2011]. Some indications for revision include mechanical failure, patellar mal-tracking, implant malalignment, disease progression and persistent pain or stiffness [Dy, 2011; Turktas, 2015]. Implant mal-positioning can lead to decreased patient satisfaction and increased revision rates [Turktas, 2015]. Morphological variability may increase the likelihood of implant mal-positioning. This study quantifies the morphological variability of the anterior-posterior (AP) and medial-lateral (ML) aspects of the patellofemoral compartment using a database of computed tomography (CT) scans. The analysis presented here used the custom CT based program SOMA (SOMA V.4.3.3, Stryker, Mahwah, NJ). SOMA contains a large database of 3D models created from CT scans. Anatomic analysis and implant fitting tools are also integrated into SOMA to perform morphometric analyses. A coordinate system is established from the femoral head center, the intercondylar notch, and a morphological flexion axis (MFA). The MFA is created by iteratively fitting circles to the posterior condyles and creating and axis through the circles' centers. The sagittal plane is created normal to this axis and through the notch. A coronal plane is created from the femoral head center and the flexion axis. The AP measurement is taken normal to the coronal plane from the anterior cortex sulcus to the intercondylar notch (Figure 1). A 5°-flexed anterior resection is created to run-out at the anterior cortex sulcus. The ML measurement is taken normal to the sagittal plane from the most medial to the most lateral points of the anterior resection (Figure 1). The ML measurements are broken down into medial and lateral components divided by a sagittal plane through the trochlea. Means and standard deviations of the AP and ML measurements are calculated. The mean and standard deviation for the AP measurement are 24.9mm and 2.8mm, respectively. The data predicts that 99.7% of the population will have an AP measurement between 16.5mm and 33.3mm. The mean and standard deviation for the ML measurement are 54.6 mm and 5.5mm, respectively. The data predicts that 99.7% of the population will have an ML measurement between 38.1mm and 71.1mm A Pearson Correlation value of 0.134 was calculated for AP/ML indicating a very weak positive correlation between the measures. The correlation value and the large measurement ranges indicate that there is high variability between the AP and ML measurements. A scatterplot was created to graphically represent the high variability between the AP and ML width measurements (Figure 2). A Pearson Correlation value of −0.649 was calculated for the medial and lateral components of ML (Figure 3). The results of this study suggest that patellofemoral morphology is highly variable with respect to the AP and ML dimensions. This variability may impact implant fit and positioning and should be taken into consideration in the design and use of prostheses for PFA. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. The aim of this radiographic study was to define the anatomical axis joint centre distance (aJCD) and anatomical axis joint centre ratio (aJCR) of the distal femur in the coronal plane for skeletally mature individuals. Materials and Methods. A cross-sectional radiographic study was conducted to calculate the horizontal distances between the anatomical axis and the centre of the knee at the level of the intercondylar notch and the joint line. Ratios relating these points to the width of the femur were then calculated. Results. A total of 164 radiographs were included: 91 male (55.5%) and 73 female patients (44.5%) with a mean age of 44.9 ± 18.0 years, with 79 right (48.2%) and 85 left (51.8%). The intercondylar width mean was 75.4 ± 6.8mm, the median aJCD at the notch was 3.6mm (interquartile range, IQR 2.1 – 5.1), the median aJCD at the joint line was 4.7mm (IQR 3.5 – 6.3), the aJCR at the notch 45.1 ± 2.7, and the aJCR at the joint line 43.5 ± 2.7. The intercondylar width was significantly different (p<0.001) between males (79.5 ± 5.0 mm) and females (70.4 ± 5.1 mm). A significant difference between the aJCR at the notch (p=0.003) and the aJCR at the joint line (p=0.002) was observed in males and females. No differences between the aJCD at the notch or aJCD at the joint line was observed between males versus females, left versus right and those younger versus those older than 65 years. Conclusions. This is the first objective description of the anatomic axis joint centre ratio (aJCR) of the distal femur in the coronal plane. This ratio can be used to aid the planning and execution of distal femoral deformity correction, retrograde femoral nailing, and total knee arthroplasty

Introduction. Alignment and positioning of implants is important in total knee arthroplasty (TKA). Identifying the femoral hip center (FHC) without fluoroscopy or computer navigation is considered difficult. The Complete Compass system (CoCo) is a femoral extramedullary guidance system designed to identify the FHC. This apparatus provides an accurate representation of the femoral functional axis in the coronal plane without a computer navigation system. We compared postoperative implant alignment of patients undergoing total knee arthroplasty between CoCo and intraoperative computer navigation. Materials and Methods. Twenty-five consecutive TKAs using CoCo were analyzed. CoCo has a pivotal arm with a pivotal shaft arranged to extend perpendicular to the coronal plane. A marker is attached to the pivotal arm to depict a circular arc on the marking plate with rotation of the pivotal arm. The pivotal shaft is placed at the intercondylar notch of the femur. The distance from the pivotal shaft to the marker is equal to the distance from the intercondylar notch of the femur to the FHC of the patient based on preoperative measurements in the coronal plane. This apparatus has a level of the horizontal plane and the condition of the pivotal shaft is able to match neutral positions in the sagittal and axial planes. The intersection of two arcs drawn by using CoCo with the hip joint in abduction and adduction indicates the FHC position. Postoperative coronal and sagittal views radiographs were obtained. Twenty-five TKAs implanted using computer navigation were also analyzed for postoperative alignment. For two groups, targeted implant position was 90° in both planes for the femoral functional axis. Results. In the CoCo group, mean absolute difference between planned and actual femoral placement was 0.5° (standard deviation (SD), 0.7) in the coronal plane and 2.8° (SD, 1.3) in the sagittal plane. For the computer navigation group, mean difference from ideal placement for the femur was 0.6° (SD, 0.7) in the coronal plane and 2.2° (SD, 1.4) in the sagittal plane. In all comparisons, no significant differences were seen between CoCo and computer navigation. Conclusion. In this study, the Coco group achieved accurate alignment and implant positioning without computer navigation, and results were comparable to computer navigation TKA. CoCo is a simple system, and has the possibility to take the place of expensive computer navigation systems

Introduction. Intramedullary femoral alignment guide is mostly used in total knee arthroplasty (TKA). Accurate preoperative plan is critical to get good alignments when we use intramedullary femoral guide, because the center of femoral head cannot be looked directly during operation. Commonly, the planning is carried out using preoperative anteroposterior radiographs of the femur. The angles formed between mechanical axes of the femur and distal femoral anatomic axes (AMA) are measured as reference angles of resection of distal femur, and the entry points of intramedullary femoral guide are also planned. The purpose of this study is to investigate the influence of femoral position on radiographic planning in TKA. Materials and Methods. We examined 20 knees of 20 female patients who received TKA. Fourteen patients suffered from primary osteoarthritis of the knees, and 6 suffered from rheumatoid arthritis. Fifteen patients have varus knee deformities and 5 patients have valgus knee deformities. Long leg computed topography scans were performed in all cases before operations, and all images were stored in DICOM file format. The analyses were performed with computer software (3D template, JMM, Osaka, Japan) using DICOM formatted data. The planes containing the center of femoral head and transepicondylar axes were defined as reference planes, and the reference planes were fixed all through analyses. At first, to assess the influence of femoral rotation, the femur was rotated from 30 degrees external rotation to 30 degrees internal rotation in 5 degrees increments in full extension. After that, to examine the influence of knee flexion, the knee was bended from full extension to 30 degrees flexion in 5 degrees increments in neutral rotation. Reconstructed coronal planes parallel to the reference planes were made, the angles between mechanical axes of the femur and distal femoral anatomic axes (AMA) and the distance from entry points to the center of femoral intercondylar notch were measured in each position. The distal anatomic axes were made by connecting the center of femoral canal at 8 centimeters proximal to joint line and that at 16 centimeters proximal to joint line. The entry points of intramedullary femoral guide were defined the points where distal anatomic axes meets intercondylar notch. Results. The mean AMA was 6.8 degrees in neutral position, 7.1 degrees in 10 degrees external rotation, 7.3 in 20 degrees external rotation, 7.2 in 30 degrees external rotation, 6.2 in 10 degrees internal rotation, 5.5 in 20 degrees internal rotation, 4.6 in 30 degrees internal rotation, 6.9 in 10 degrees flexion, 7.2 in 20 degrees flexion, 7.8 in 30 degrees flexion, respectively. The entry points moved 3.9 millimeters laterally in 20 degrees external rotation and 3.6 millimeters medially in 20 degrees internal rotation relative to neutral position. Discussion and Conclusion. Femoral position affected on preoperative planning using anteroposterior radiographs. It is important to get a correct anteroposerior view of total femur, because the femur was easy to rotate in knee disorders

Purpose. Leg length discrepancy after total hip arthroplasty (THA) sometimes causes significant patient dissatisfaction. In consideration of the leg length after THA, leg length discrepancy is often measured using anteroposterior (AP) pelvic radiography. However, some cases have discrepancies in femoral and tibial lengths, and we believe that in some cases, true leg length differences should be taken into consideration in total leg length measurement. We report the lengths of the lower limb, femur, and tibia measured using the preoperative standing AP full-leg radiographs of the patients who underwent THA. Materials and methods. From August 2013 to February 2017, 282 patients underwent standing AP full-leg radiography before THA. Of the patients, 33 were male and 249 were female. The mean age of the patients was 65.7±9.4 years. We measured the distances between the center of the tibial plafond and lesser trochanter apex (A-L), between the femoral intercondylar notch and lesser trochanter (K-L), and between the centers of the tibial plafond and intercondylar spine of the tibia (A-K) on standing AP full-leg radiographs before THA operation. We examined the differences in leg length and the causes of these discrepancies after guiding the difference between them. Results. The mean A-L was 674±44 mm on the right and 677±43 mm on the left. The mean difference between the left and the right was 6.2±7 mm. The differences of ≥5 and ≥10 mm between the left and right were confirmed in 131 (46%) and 39 cases (14%), respectively. The mean K-L was 343±23 mm on the right and 343±23 mm on the left, with a mean difference of 4.4±4 mm. The lateral differences of ≥5 and ≥10 mm were confirmed in 88 (31%) and 22 (8%), respectively. The mean A-K was 325±22 mm on the right and 327±22 mm on the left, with a mean difference of 4±4.5 mm. The differences of ≥5 and ≥10 mm between the left and right were confirmed in 24 (9%) and 67 cases (%), respectively. Discussion. Considering the total length of the lower limbs beyond the little trochanter and the leg length after THA, we confirmed that 46% of the leg length differences of ≥5 mm were admitted to 14%. Thus, THA appeared effective. Perthes head, Crowe classifications 3 and 4, history of childhood paralysis, and so on may be factors for leg length differences beyond the lesser trochanter. Conclusion. We think that it would be preferable to prepare a preoperative plan to measure leg length after THA by measuring the total length of the lower extremity before surgery and determining the difference between the left and right sides

In performing posterior cruciate ligament- retaining total knee arthroplasty (CR-TKA), the original surgical instrument was devised to obtain the range of motion and stability of the knee joint adequate for daily life of Japanese people. We have presumed the tentative joint line as intercondylar notch point of the distal femur, and performed surgery using surface replacement to resect metal width of the femoral component for the distal femur by setting the knee to the original position based on understanding of the shape of anterior curvature of the distal femur in Japanese people in case of implanting the femoral component. In order to obtain stability of the knee, we have minimally released the soft tissue and resected the anterior cruciate ligament (ACL), whereas completely preserved the posterior cruciate ligament (PCL) and maintained physiological ligament balance of the knee joint by resecting the medial condyle of the tibia (genu varus). Our surgical procedure enabled deep flexion knee (knee embracing) greater than 145 degrees in 9.7% and also allowed Japanese sitting in three different designs of total knee joints

Posterior stabilized (PS) total knee arthroplasty (TKA), wherein mechanical engagement of the femoral cam and tibial post prevents abnormal anterior sliding of the knee, is a proven surgical technique. However, many patients complain about abnormal clicking sensation, and several reports of severe wear and catastrophic failure of the tibial post have been published. In addition to posterior cam-post engagement during flexion, anterior engagement with femoral intercondylar notch can also occur during extension. The goal of this study was to use dynamic simulations to explore sensitivity of tibial post loading to implant design and alignment, across different activities. LifeModeler KneeSIM software was used to calculate tibial post contact forces for four contemporary PS implants (Triathlon PS, Stryker; Journey BCS and Legion PS, Smith & Nephew; LPS Flex, Zimmer Biomet). An average model of the knee, including cartilage and soft tissue insertion locations, created from MRI data of 40 knees was used to mount and align the component. The Triathlon femoral component was mounted with posterior and distal condylar tangency at: a) both medial and lateral condylar cartilage (anatomic alignment), b) at the medial condylar cartilage and perpendicular to mechanical axis (mechanical alignment with medial tangency), and c) at lateral condylar cartilage and perpendicular to mechanical axis (mechanical alignment with lateral tangency). The influence of implant design was assessed via simulations for the other implant systems with the femoral components aligned perpendicular to mechanical axis with lateral tangency. Five different activities were simulated. The anterior contact force was significantly smaller than the posterior contact force, but it varied noticeably with tibial insert slope and implant design. For Triathlon PS, during most activities anatomic alignment of the femoral component resulted in greater anterior contact force compared to mechanical alignment, but absolute magnitude of forces remained small (<100N). Mechanical alignment with medial tangency resulted in greater posterior contact force for deep knee bend and greater anterior force for chair sit activity. For all implants, peak posterior contact forces were greater for activities with greater peak knee flexion. The magnitude of posterior contact forces for the various implants was comparable to other reports in literature. Overall activity type, implant design and slope had greater impact on post loading than alignment method. Tibial insert slope was shown to be important for anterior post loading, but not for posterior post loading. Anatomic alignment could increase post loading with contemporary TKA systems. In the case of the specific design for which effect of alignment was evaluated, the changes in force magnitude with alignment were modest (<200N). Nonetheless, results of this study highlight the importance of evaluating the effect of different alignment approaches on tibial post loading

Introduction. Current techniques in total knee arthroplasty aim to restore the coronal mechanical axis to neutral. Preoperative planning has historically been based on long-leg standing films (LLSF) which allow surgeons to plan bony resection and soft tissue releases. However, LSSF can be prone to error if malrotated. Recently, patient-specific guides (PSG) utilizing supine magnetic resonance imaging (sMRI) have become an accepted technique for preoperative planning. In this study we sought to compare the degree of coronal deformity using LLSF and sMRI. Methods. Two hundred thirty knees underwent planning for total knee arthroplasty with sMRI and LLSF. Coronal plane deformity was determined based on the femoral-tibial angle (FTA) as defined by the angle formed between a line from the center of the femoral head to the intercondylar notch and a line from the middle of the tibial spines to the middle of the ankle joint. Mechanical axis values from the sMRI were compared with values obtained from LLSF. Results. There were 172 varus knees and 58 valgus knees. There was significant correlation (r=0.9215) between LLSF and sMRI for the measurement of coronal plane deformity for all knees. sMRI underestimated the severity of deformity by 2.19 degrees of varus (p<0.001). Additionally, as the severity of the deformity increased, there was also an increase in the discrepancy between sMRI and LLSF. There was a smaller discrepancy for valgus knees (−0.66 degrees) than varus knees (3.15 degrees, p<0.001). The discrepancy between the two modalities was not affected by gender (p=0.386). Conclusion. sMRI based imaging can help approximate coronal plane deformity in the preoperative planning of TKA but it has limitations. This MRI-based technique tended to underestimate deformity in varus knees and patients with extreme deformity. Surgeons may use sMRI for pre-operative planning but must understand that they tend to underestimate the severity of deformity

Introduction. The convincible wisdom is that the release of MCL in severe varus knee should be progressive. This release is usually carried on after resecting the osteophyte and gradually carried on until the MCL is well balanced. However, sometimes, extensive release and releasing the superficial MCL can lead to instability in flexion. On a personal communication with many Asian surgeons they have been doing a careful release of the posteromedial corner in the varus knee and in majority of cases such release is adequate. And even in severe cases of varus knee superficial MCL doesn't need to be released. 20 total knee replacements were performed by the same surgeon using ZimmerPS implant. In the varus deformity ranges from 15–35 degrees. The first bony section was made carefully. All osteophytes were removed and resected. The posterior bone osteophytes were also resected and the intercondylar notches were made along with the posterior release. After doing the bony cut in 18 of those cases the medial compartment was still tight and both flexion and extension. A careful release was carried in the postal medial corner-First using an osteotome around the posteromedial corner to release the soft tissue. After that the thick fibrous tissue that formed like pseudo meniscus was also resected until we were able to reach the posterior capsule. In some cases those scar tissues even extended to the capsule requiring the resecting of the postal medial capsule. We meticulously resected all those scar tissues and in many of those cases were able to visualize the MCL ligament which was well preserved. A tensioning device was used before and after the release. In all of those cases we were able to document an opening ranging from two to seven millimeter after the proper release. In all cases the superficial MCL were still intact and can be operated carefully. Result. This study clearly shows that we did not have to release the superficial MCL and the careful posteromedial release was adequate to obtain a good balance gap immediately and the knee was quite stable. The superficial MCL was maintained and preserved and tensioning device clearly document opening after releasing the postural medial corner. Discussion. In varus knee there is an extensive scar tissue which can sometimes tension the mcl ligament and releasing the deep mcl along with posture medial corner without releasing the superficial will preserve the stability of the knee allowing us to ambulate the patient immediately and preventing instability. Conclusion. Although MCL release has been described in diff ways in multiple literatures, little attention has been paid to the posture medial corner. This paper clearly shows that the complex anatomy of the posture medial corner along with scarring can lead to a tight mcl Releasing such structures would balance MCL&LCL without compromising the superficial MCL which normally lead to obvious flexion instability and a mid-section instability. We strongly recommend surgeon to do the posteromedial release before doing any release to the superficial mcl. Doing so will prevent the incidence of instability after extensive release in varus deformity

Objective. To explore whether good postoperative alignment could be obtained through simple individual valgus resection angle using common instruments in total knee arthroplasty with lateral bowing femur. Methods. Data of 46 TKAs with lateral bowing femur were collected prospectively, the center of the femoral intercondylar notch was the fixed drilling hole whether preoperative planning or intraoperative implementing. The intramedullary rod was put into the femur as deep as possible, until completely entrance or the distal point of the rod contact with the lateral cortical bone of the femur, which prevent the further entrance of the rod. Individual valgus resection angle ranging from 7°to 9°was performed according to preoperative planning, followed by meticulous assessment of matching between cutting surface and valgus resection angle. Postoperative hip-knee-ankle (HKA) angle?medial tibial plate angle and position of lower extremity alignment passing through the tibial plate were measured. Results. The preoperative measurement valgus resection angle include 14 cases of 8°, 13 cases of 9°, 5 cases of 10°, 2 case of 11°. The postoperative mean medial tibial plate angle was 89.5°±0.5°, mean HKA angle was 179.3°±0.8°. 27(79.4%), 23(67.6%) and 16 (47.1%) cases had restoration of mechanical axis to ±3°, ±2°and ±1°of neutral respectively, and there were 7 (15.2%) outlier (±3°). Excluding 3 cases of actual performed 9°valgus resection angle while preoperative measurement larger than 9°, both components were aligned within 3° of neutral in 88.2% of the knees. 27 (79.4%) cases had lower extremity alignment passing through the middle third of tibial plate, 7 (20.6%) cases pass through the medial third of the tibial plate. Conclusions. Excellent postoperative alignment could be obtained through simple individual valgus resection angle using common instruments in total knee arthroplasty with lateral bowing femur

The condylopatellar notch (CPN) represents the border between the patellofemoral articulation and the tibiofemoral articulation [Pao, 2001]. This could be a valuable landmark for establishing the boundaries of unicompartmental knee replacements. Its location on the distal femur has been described radiographically, but it has not, to our knowledge, been quantified with respect to anatomic landmarks [Hoffelner, 2015]. This study seeks to leverage a large database of computed tomography (CT) scans to quantify the location of the CPN with respect to well established anatomic landmarks of the knee. The analysis presented here used the custom CT based program SOMA (SOMA V.4.3.3, Stryker, Mahwah, NJ). SOMA contains a large database of 3D models created from CT scans. Anatomic analysis and implant fitting tools were also integrated into SOMA to perform morphometric analyses. 986 healthy distal femurs were analyzed. A coordinate system was established from the femoral head center, the intercondylar notch, and a morphological flexion axis (MFA). The MFA was created by iteratively fitting circles to the posterior condyles and creating and axis through the circles' centers. The sagittal plane was created normal to this axis and through the notch. A plane was created from the femoral head center and the flexion axis. A coronal plane was created from this plane and a point on the anterior cortex sulcus. Points were placed on a template bone model in the medial and lateral extents of the surface depressions of both the medial and lateral aspect of the CPN, where the depression of the CPN is most distinct. These points were then mapped to each of the 986 femoral specimens via a shape correspondence model. A line is created between the pairs of points representing the medial and lateral CPN's. The coordinates of the points are measured with respect to sagittal and coronal planes (Figure 1). Means and standard deviations of the anterior-posterior (AP) and medial-lateral (ML) coordinates of the CPN points are calculated. The mean coordinates for the lateral CPN line are (4.8±1.6, −33.6±6.8) and (29.1±5.4, −18.7±4.8). The mean coordinates for the lateral CPN are (−20.7±3.8, −2.2±4.4) and (−6.5±1.6, −29.7±3.2). The means with error bars representing two standard deviations are plotted on a scatter plot (Figure 2). Boxes representing the location of the CPN line for 95% of the population are included on the plots. Until now, the location of this anatomic feature of the knee has not been quantified with respect to known anatomical landmarks. The location of the CPN could serve as a valuable landmark for determining the border between the tibiofemoral and patellofemoral articulations. This data can be used to locate the CPN and inform the planning and design of compartmental knee replacements. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Introduction. Pelvic posterior tilt change (PPTC) after THA is caused by release of joint contracture and degenerative lumbar kyphosis. PPTC increases cup anteversion and inclination and results in a risk of prosthesis impingement (PI) and edge loading (EL). There was reportedly no component orientation of fixed bearing which can avoid PI and EL against 20°PPTC. However, dual mobility bearing (DM) has been reported to have a large oscillation angle and potential to withstand EL without increasing polyethylene (PE) wear against high cup inclination such as 60∼65°. Objective. The purpose of this study was to investigate the optimal orientation of DM-THA for avoiding PI and EL against postoperative 20°PPTC. Methods. Our study was performed with computer tomography -based three-dimensional simulation software (ZedHip. LEXI co. Japan). The CT data of hip was derived from asian typical woman with normal hips. Used prosthesises were 50mm cup and 42mm outer head of modular dual mobility system and Accolade II 127°(stryker). Femoral coordinate system was retrocondylar plane with z-axis from trochanteric fossa to intercondylar notch. Cup orientation was described as anatomical definition. The safe zone was calculated by the required hip range of motion which was defined as 130°flexion, 40°extension, 30°external rotation, and 50°internal rotation with 90°flexion and the maximum inclination of DM cup which was 60°in consideration of withstanding EL. Cup orientations withstanding 20°PPTC were defined as the primary cup orientation which changes consistently within the safe zone with the match of 20°PPTC. And among them cup orientation with lowest inclination was defined as the optimal cup orientation. result. The optimal orientations could be identified only within stem anteversion from 15°to 40°. The relationship between the optimal cup orientation and stem anteversion could be automatically identified. The correlation between stem anteversion and cup anteversion was linearly distributed and could be expressed as an approximated line of the formula that (stem anteversion)+(cup anteversion)=36.8. And likewise the relationship between stem anteversion and cup inclination was curved-linerly distributed and could be expressed as an approximated curved line of the formula that (cup inclination)=0.04(stem anteversion). 2. 2.18(stem anteversion)+74.8. Cup orientation calculated by the Widmer's combined anteversion theory is easily deviated from the safe zone by PPTC. The optimal cup orientation calculated in this study could be set more inclination and retroversion than it calculated by the Widmer's theory in contribution of large oscillation angle and admissibility of high inclination cup setting of DM. Therefore it could be possible to withstand 20°PPTC. Conclusion. Performing THA with considering postoperative PPTC is necessary for good long term outcome without dislocation and PE wear. The solution for 20°PPTC after THA is to apply dual mobility bearing and the formula of combined orientation theory calculated in this study

Introduction. Patellar crepitus and clunk are tendofemoral-related complications predominantly associated with posterior-stabilizing (PS) total knee arthroplasty (TKA) designs [1]. Contact between the quadriceps tendon and the femoral component can cause irritation, pain, and catching of soft-tissue within the intercondylar notch (ICN). While the incidence of tendofemoral-related pathologies has been documented for some primary TKA designs, literature describing revision TKA is sparse. Revision components require a larger boss resection to accommodate a constrained post-cam and stem/sleeve attachments, which elevates the entrance to the ICN, potentially increasing the risk of crepitus. The objective of this study was to evaluate tendofemoral contact in primary and revision TKA designs, including designs susceptible to crepitus, and newer designs which aim to address design features associated with crepitus. Methods. Six PS TKA designs were evaluated during deep knee bend using a computational model of the Kansas knee simulator (Figure 1). Prior work has demonstrated that tendofemoral contact predictions from this model can differentiate between TKA patients with patellar crepitus and matched controls [2]. Incidence of crepitus of up to 14% has been reported in Insall-Burstein® II and PFC® Sigma® designs [3]. These designs, in addition to PFC® Sigma® TC3 (revision component), were included in the analyses. Primary and revision components of newer generation designs (NexGen®, Attune® and Attune® Revision) were also included. Designs were evaluated in a patient model with normal Insall-Salvati ratio and a modified model with patellar tendon length reduced by two standard deviations (13mm) to assess worst-case patient anatomy. Results. During simulations with normal patellar tendon length, only PFC® Sigma® and PFC® Sigma® TC3 showed tendofemoral contact within the trochlea, and no design showed contact at the transition to the ICN (Figure 2). In simulations with patella baja, Insall-Burstein® II, PFC® Sigma®, and PFC® Sigma® TC3, demonstrated tendofemoral contact across the trochlea at the transition into the notch. In contrast, NexGen®, Attune® and Attune® Revision showed tendon contact for approximately half the width of the transition to the notch (Figure 3). PFC® Sigma® and Attune® demonstrated very similar tendofemoral contact to their equivalent revision components, although the shorter trochlear groove of Attune® Revision marginally increased contact at the transition. Discussion. Insall-Burstein® II, PFC® Sigma®, and PFC® Sigma® TC3 designs showed full contact with the quadriceps tendon at the anterior border of the ICN when combined with a short patellar tendon. NexGen®, Attune® and Attune® Revision had a more gradual transition between the trochlea and the notch, which resulted in less exposure to tendon contact. Even with the shorter trochlear groove required for revision components, Attune® Revision showed minimal difference in tendofemoral contact when compared with Attune®. There appears to be distinct benefit in a femoral design which reduces tendofemoral contact at the transition to the ICN; this may be of particular importance for patients with patella baja

OBJECTIVE. The purpose of this study was to investigate the postoperative change of hematological values between post cam type posterior stabilized (PS) and deep dish cruciate substituting (CS) type total knee arthroplasty (TKA). MATERIALS AND METHODS. From June 1999 to December 2013, 322 patients with TKA due to osteoarthritis or rheumatoid arthritis were enrolled. In all knees, posterior cruciate ligament (PCL) were resected, and either Scorpio NRG PS knee (Stryker Orthopaedics) or Triathlon CS knee (Stryker Orthopaedics) were implanted. The PS group included 183 patients (183 knees) consisting of 4 men (4 knees) and 179 women (179 knees) with a mean age of 68.5 years (range 31 – 86 years). And the CS group included 139 patients (139 knees) consisting of 27 men (27 knees) and 112 women (112 knees) with a mean age of 75 years (range 42 – 98 years). Simultaneous bilateral TKA were excluded in this study. No case had blood transfusion in perioperative period. The changes of hemoglobin (Hb), d-dimer (DD) and c-reactive protein (CRP) were compared at pre-operative value, 1, 4, 7 and 14 days after surgery in two groups. RESULT. In both groups, Hb was lowest at 4 days after surgery. CRP was highest at 4 days after surgery, and DD bimodal change high in one day and 14 days after surgery. In comparison with PS group and CS group. The values of Hb were significantly lower in PS group at 1, 4, and 7 days after surgery. The values of CRP changes were significantly higher in PS group than CS group at 1, 4, 7 days after surgery. And the values of DD were not significantly different in two groups. CONCLUSION. In this study, PCL were resecte in all knee. The difference of surgical procedure in PS knee and CS knee was bone resection of femoral intercondylar notch. In PS knee, for the space of post cam mechanism, we had to remove some amount of the bone from the notch. In contrast, we did not have to remove the bone in CS knee. The difference of the procedure could be the causes of lower amount of bleeding and less surgical invasiveness presented by CRP changes in CS knee

Purpose:. Anterior positioning of a cephomedullary nail (CMN) in the distal femur occurs in up to 88% of cases. Conventionally, this is considered to occur because of a mismatch between the radius of curvature (ROC) of the femur and that of available implants. The hypothesis for this study was that the relative thicknesses of the cortices of the femur, particularly the posterior cortex are important in determining the final position of an intramedullary implant and that the posterior cortical thickness corresponds to the linea aspera anatomically. The aim was to determine if these measurements changed with age. Method:. This study used the data from CT scans undertaken as part of routine clinical practice in 919 patients with intact left femora (median age 66 years, range 20–93 years; 484 male and 435 female). The linea aspera was defined manually on the template bone by consensus between two orthopaedic surgeons and two anatomists. The length of the femur was measured from the tip of the greater trochanter proximally to the intercondylar notch distally. Transverse intervals were plotted on the femur between 25%–60% femoral bone length (5% increments). The linea aspera was then defined at each interval on the template bone and mapped automatically to all individual femora in the database. Results:. The linea aspera was found to be internally rotated as compared to the sagittal plane referenced off the posterior femoral condyles. An age related change in the posterior/anterior cortical thickness ratio was demonstrated. This ratio increases in all age groups from 25–60% bone length being maximal around 45–55% bone length. The ≥80 year old cohort shows a disproportional posterior/anterior ratio increase of 70.0% from 25–50% bone length as compared to 48.1% for the <40 year old cohort which is statistically significant (Mann-Whitney-Test p<0.05, α = 5%). Conclusion:. This study presents a novel method of investigating femoral anatomy with directly relevance to orthopaedic procedures. This study has shown that assessment in the sagittal plane may be inaccurate because the linea aspera changes in this plane throughout the length of the femur. It also shows the loss of the centering influence of the corticies with age with a relative thinning of the anterior cortex with a concomitant thickening of the posterior cortex moving distally in the femur. This has a very direct and significant influence on the positioning of intramedullary femoral implants explaining the preponderance of anterior malpositioning of intramedullary implants in the elderly

Performance and durability of total knee arthroplasty is optimised when bone surfaces are prepared with the knee in neutral varus-valgus alignment in the anteroposterior (AP) plane. For the femur, this means resecting the surface perpendicular to the mechanical axis of the femur, which passes through the center of the femoral head and center of the knee. Because the center of the femoral head is not a reliable landmark during the operation, the distal femoral surface can be resected at 5 degrees valgus to the long axis of the femur using an intramedullary (IM) alignment rod to establish the position of the femur's long axis. The IM rod also provides the landmark for alignment of the femoral component in the flexion-extension position. Tibial alignment is established by cutting the upper surface of the tibia perpendicular to the long axis. An extramedullary (EM) rod easily can span the distance between the centers of the tibial surface at the knee and ankle to establish a reference for upper tibial surface resection via the long axis of the tibia. In cases with femoral deformity or bone disease that prevents use of an IM rod as a landmark for the long axis of the femur, plain film radiographs can be used along with intraoperative measurements and hand-held tools that are readily available in the standard total knee instrument set. Using an AP radiograph taken to include the femoral head and knee: 1.) Mark the centers of the femoral head and knee. 2.) Draw a line to connect the centerpoints. 3.) Mark the high points of the medial and lateral femoral condylar joint surfaces. 4.) Draw a line perpendicular to the mechanical axis that crosses the mark on the high point of the most prominent femoral condyle. This marks the position and alignment of the femoral implant surface. 5.) To measure the distal thickness of the femoral component and adding 10% to account for magnification of the radiograph, mark two points proximal to the two high points of the condyles and draw a line perpendicular through these two points to mark the resection line for the distal femoral surfaces. Less than the thickness of the implant will be resected from the least prominent condyle. 6.) Measure the thickness of bone to be resected and the distance between the bone surface and distal surface line. This distance represents the space between the distal femoral cutting guide and the joint surface of the deficient condyle. 7.) Insert a threaded pin into the bone surface with the measured distance protruding from the surface to set this position. 8.) Seat the distal femoral cutting guide against the protruding pin on the low side and against the surface of the femur on the high side. This aligns the distal femoral cutting guide perpendicular to the mechanical axis of the femur. 9.) Draw the AP axis from the center of the intercondylar notch posteriorly to the deepest point of the patellar groove, and use the combined cutting guide to finish the femur. 10.) Make the anterior, posterior, and bevel cuts perpendicular to the AP axis. 11.) Finally, align the tibial surface, with an IM or EM rod, to resect perpendicular to the long axis of the tibia in the AP plane and sloped 4 degrees posteriorly in the lateral plane. 12.) Once the bone surfaces are resected at the proper angle, insert the trials or spacer blocks and finish the arthroplasty with release of tight ligaments

The cornerstone to correct ligament balancing is correct varus and valgus alignment in flexion and extension. For alignment in the extended position, fixed anatomic landmarks such as the intramedullary canal of the femur and long axis of the tibia are accepted. When the joint surface is resected at an angle of 5° to 7° valgus to the medullary canal of the femur and perpendicular to the long axis of the tibia, the joint surfaces are perpendicular to the mechanical axis of the lower extremity, and roughly parallel to the epicondylar axis. In the flexed position, anatomic landmarks are equally important for varus-valgus alignment. Incorrect varus-valgus alignment in flexion not only malaligns the long axes of the femur and tibia, but also incorrectly positions the patellar groove both in flexion and extension. Finding suitable landmarks for varus-valgus alignment has led to efforts to use the posterior femoral condyles, epicondylar axis, and anteroposterior (AP) axis of the femur. The posterior femoral condyles often are not reliable rotational alignment landmarks because the femoral joint surface has been worn or otherwise distorted by developmental abnormalities or the arthritic process. As with the distal surfaces, the posterior femoral condylar surfaces sometimes are damaged or hypoplastic (more commonly in the valgus than in the varus knee) and cannot serve as reliable anatomic guides for alignment. The epicondylar axis is anatomically inconsistent and in all cases other than revision total knee arthroplasty with severe bone loss, is unreliable for varus-valgus alignment in flexion just as it is in extension. The AP axis, defined by the centre of the intercondylar notch posteriorly and the deepest part of the patellar groove anteriorly, is highly consistent, and always lies within the median sagittal plane that bisects the lower extremity, passing through the hip, knee, and ankle. When the articular surfaces are resected perpendicular to the AP axis, they are perpendicular to the AP plane, and the extremity can function normally in this plane throughout the arc of flexion. Once the knee is set up in correct alignment, ligament balancing can be done with simple procedures based on basic anatomy. Anterior structures tighten in flexion, and posterior structures tighten in extension. Release of tight structures in a controlled fashion completes the aligned and balanced knee