3D CT analysis of femoral and tibial tunnel positions after modified transtibial single bundle ACL reconstruction with varus and internal rotation of the tibia

IntroductionWe analyzed the location of femoral and tibial tunnels by three-dimensional (3D) CT reconstruction images after modified transtibial single bundle (SB) anterior cruciate ligament (ACL) reconstruction, creating a femoral tunnel with varus and internal rotation of the tibia.Material and methodsData from 50 patients (50 knees) analyzed by 3D CT after modified transtibial SB ACL reconstructions were evaluated. 3D CT images were analyzed according to the quadrant method by Bernard at the femur and the technique of Forsythe at the tibia.ResultsThe mean distance of the femoral tunnel center locations parallel to the Blumensaat's line was 29.6% ± 1.9% along line t measured from the posterior condylar surface. The mean distances perpendicular to the Blumensaat's line were 37.9% ± 2.5% along line h measured from the Blumensaat's line. At the tibia, the mean anterior-to-posterior distance for the tunnel center location was 37.8% ± 1.2% and the mean medial-to-lateral distance was 50.4% ± 0.9%.DiscussionThe femoral and tibial tunnels after modified transtibial SB ACL reconstruction creating a femoral tunnel with varus and internal rotation of the tibia (figure-of-4 position) were located between the anatomical anteromedial and posterolateral footprints.     

Gender analysis of the anterior femoral condyle geometry of the knee

BackgroundNo study has used 3-D anatomic knee models to investigate the gender differences in anterior femoral condyles. Therefore, this study aims to determine the morphologic differences between genders in anterior femoral condyles of the knees using 3-D anatomic knee models.MethodsNinety-six male and sixty-five female 3D anatomic knee models were used to measure lateral and medial anterior condyle heights, anterior trochlear groove heights, and anterior condyle width, which were normalized by the anterior–posterior and medial–lateral dimensions of the knee, respectively. The shape of anterior condyle groove was also analyzed.ResultsThe mean lateral anterior condyle height, medial anterior condyle height and anterior condyle width of females were 6.6 ± 1.8 mm, 2.0 ± 2.3 mm, and 44.7 ± 4.2 mm, respectively. These data were significantly smaller (p < 0.05) than those of males (7.7 ± 1.8 mm, 2.9 ± 2.0 mm and 50.0 ± 3.4 mm). However, after normalizing by the femur size, the aspect ratios had no gender differences. Both the ranges of lateral and medial condyle of females were significantly smaller than those of males, and the geometry curve of anterior condyle was different between genders.ConclusionAlthough the gender differences in anterior femoral condyle sizes no longer existed after normalization with the femur size, the shape and the peak position of anterior condyle groove still have gender differences. The data may have important implications on the current debate of gender-specific TKAs.Clinical relevanceThis study provides a better understanding of gender differences in anterior femoral condyle geometry.     

Dynamic imaging with dual-source gated Computed Tomography (CT): Implications of motion parameters on image quality for wrist imaging

ObjectiveDynamic Computed Tomography (CT) promises insights into the pathophysiology of carpal instability by recording images of the carpus while it is in motion. The purpose of this study was to investigate the effect of motion velocity on image quality for dynamic carpal imaging applications using a clinical dual-source CT (DSCT) scanner.MethodsA phantom with targets in the axial, coronal and sagittal planes was attached to a motion simulator and imaged using a 64-slice DSCT scanner. Data was acquired when the phantom was stationary and during periodic linear motion. Spatial resolution, motion artifacts and banding artifacts were assessed.ResultsMean spatial resolution was 0.82 mm at 36 mm/s and 0.79 mm at 18 mm/s. Banding artifacts were mild at 36 mm/s and minimal at 18 mm/s. Motion artifacts were minimal at motion velocity of up to 36 mm/s in both the coronal and sagittal planes. Axial plane motion artifacts were moderate at 36 mm/s and mild at 18 mm/s.DiscussionSub-millimeter resolution is achievable with commercially available DSCT scanners with mild to moderate amounts of motion artifacts at velocities of 18 mm/s and 36 mm/s respectively.     

A computer-aided diagnosis approach for emphysema recognition in chest radiography

The purpose of this work is twofold: (i) to develop a CAD system for the assessment of emphysema by digital chest radiography and (ii) to test it against CT imaging. The system is based on the analysis of the shape of lung silhouette as imaged in standard chest examination. Postero-anterior and lateral views are processed to extract the contours of the lung fields automatically. Subsequently, the shape of lung silhouettes is described by polyline approximation and the computed feature-set processed by a neural network to estimate the probability of emphysema.Images of radiographic studies from 225 patients were collected and properly annotated to build an experimental dataset named EMPH. Each patient had undergone a standard two-views chest radiography and CT for diagnostic purposes. In addition, the images (247) from JSRT dataset were used to evaluate lung segmentation in postero-anterior view.System performances were assessed by: (i) analyzing the quality of the automatic segmentation of the lung silhouette against manual tracing and (ii) measuring the capabilities of emphysema recognition. As to step i, on JSRT dataset, we obtained overlap percentage (Ω) 92.7 ± 3.3%, Dice Similarity Coefficient (DSC) 95.5 ± 3.7% and average contour distance (ACD) 1.73 ± 0.87 mm. On EMPH dataset we had Ω = 93.1 ± 2.9%, DSC = 96.1 ± 3.5% and ACD = 1.62 ± 0.92 mm, for the postero-anterior view, while we had Ω = 94.5 ± 4.6%, DSC = 91.0 ± 6.3% and ACD = 2.22 ± 0.86 mm, for the lateral view. As to step ii, accuracy of emphysema recognition was 95.4%, with sensitivity and specificity 94.5% and 96.1% respectively. According to experimental results our system allows reliable and inexpensive recognition of emphysema on digital chest radiography.     

The quality of bone surfaces may govern the use of model based fluoroscopy in the determination of joint laxity

The assessment of knee joint laxity is clinically important but its quantification remains elusive. Calibrated, low dosage fluoroscopy, combined with registered surfaces and controlled external loading may offer possible solutions for quantifying relative tibio-femoral motion without soft tissue artefact, even in native joints. The aim of this study was to determine the accuracy of registration using CT and MRI derived 3D bone models, as well as metallic implants, to 2D single-plane fluoroscopic datasets, to assess their suitability for examining knee joint laxity.Four cadaveric knees and one knee implant were positioned using a micromanipulator. After fluoroscopy, the accuracy of registering each surface to the 2D fluoroscopic images was determined by comparison against known translations from the micromanipulator measurements. Dynamic measurements were also performed to assess the relative tibio-femoral error. For CT and MRI derived 3D femur and tibia models during static testing, the in-plane error was 0.4 mm and 0.9 mm, and out-of-plane error 2.6 mm and 9.3 mm respectively. For metallic implants, the in-plane error was 0.2 mm and out-of-plane error 1.5 mm. The relative tibio-femoral error during dynamic measurements was 0.9 mm, 1.2 mm and 0.7 mm in-plane, and 3.9 mm, 10.4 mm and 2.5 mm out-of-plane for CT and MRI based models and metallic implants respectively. The rotational errors ranged from 0.5° to 1.9° for CT, 0.5–4.3° for MRI and 0.1–0.8° for metallic implants.The results of this study indicate that single-plane fluoroscopic analysis can provide accurate information in the investigation of knee joint laxity, but should be limited to static or quasi-static evaluations when assessing native bones, where possible. With this knowledge of registration accuracy, targeted approaches for the determination of tibio-femoral laxity could now determine objective in vivo measures for the identification of ligament reconstruction candidates as well as improve our understanding of the consequences of knee joint instability in TKA.     

The position of the centre of the femoral head relative to the midline of the pelvis: A consistent landmark in total knee replacement surgery

BackgroundFemoro-tibial malalignment in excess of 3° is a recognised contributor of early mechanical failure in total knee replacement (TKR). Knowledge of the location of the centre of the femoral head is a pre-requisite to identification of the mechanical axis of the femur and can facilitate optimal component orientation. We investigated variation in the location of the centre of the femoral head relative to the midline of the pelvis.MethodsWe analysed the pelvic radiographs of 150 patients with unilateral total hip replacements. The perpendicular distance from the centre of the femoral head of the non-operated hip to the centre of pubic symphysis was measured.ResultsThe mean distance from the centre of the femoral head to the pubic symphysis was 89.2 mm (standard deviation, 5.7 mm). Patient height strongly correlated with this distance (r = 0.53, p < 0.01), as did the diameter of the femoral head (r = 0.59, p < 0.01). The latter was significantly larger in men than in women (50.9 mm vs. 44.5 mm, p < 0.01).ConclusionThe results demonstrate that the position of the centre of the femoral head has very little variability, irrespective of patient age or body-mass index. If the gender-specific mean femoral head to midline distance is used to estimate the location of the femoral head centre, a line from this point to the centre of the femoral condyles will deviate from the true mechanical axis by no more than 1.5°, in 98% of cases.     

Recutting the distal femur to increase maximal knee extension during TKA causes coronal plane laxity in mid-flexion

BackgroundThe aim of this study was to quantify the effects of distal femoral cut height on maximal knee extension and coronal plane knee laxity.MethodsSeven fresh-frozen cadaver legs from hip-to-toe underwent a posterior stabilized TKA using a measured resection technique with a computer navigation system equipped with a robotic cutting guide. After the initial femoral resections were performed, the posterior joint capsule was sutured until a 10° flexion contracture was obtained with the trial components in place. Two distal femoral recuts of + 2 mm each were then subsequently made and the trials were reinserted. The navigation system was used to measure the maximum extension angle achieved and overall coronal plane laxity [in degrees] at maximum extension, 30°, 60° and 90° of flexion, when applying a standardized varus/valgus load of 9.8 [Nm] across the knee.ResultsFor a 10 degree flexion contracture, performing the first distal recut of + 2 mm increased overall coronal plane laxity by approximately 4.0° at 30° of flexion (p = 0.002) and 1.9° at 60° of flexion (p = 0.126). Performing the second + 2 mm recut of the distal femur increased mid-flexion laxity by 6.4° (p < 0.0001) at 30° and 4.0° at 60° of flexion (p = 0.01), compared to the 9 mm baseline resection (control). Maximum knee extension increased from 10° of flexion to 6.4° (± 2.5° SD, p < 0.005) and to 1.4° (± 1.8° SD, p < 0.001) of flexion with each 2 mm recut of the distal femur.ConclusionsRecutting the distal femur not only increases the maximum knee extension achieved but also increases coronal plane laxity in midflexion.     

A fracture risk assessment model of the femur in children with osteogenesis imperfecta (OI) during gait

Osteogenesis imperfecta (OI) is a heritable bone fragility disorder characterized by skeletal deformities and increased bone fragility. There is currently no established clinical method for quantifying fracture risk in OI patients. This study begins the development of a patient-specific model for femur fracture risk assessment and prediction based on individuals’ gait analysis data, bone geometry from imaging and material properties from nanoindentation (Young's modulus = 19 GPa, Poisson's ratio = 0.3). Finite element models of the femur were developed to assess fracture risk of the femur in a pediatric patient with OI type I. Kinetic data from clinical gait analysis was used to prescribe loading conditions on the femoral head and condyles along with muscle forces on the bone's surface. von Mises stresses were analyzed against a fracture strength of 115 MPa.The patient with OI whose femur was modeled showed no risk of femoral fracture during normal gait. The highest stress levels occurred during the mid-stance and loading responses phases of gait. The location of high stress migrated throughout the femoral diaphysis across the gait cycle. Maximum femoral stress levels occurred during the gait cycle phases associated with the highest loading. The fracture risk (fracture strength/von Mises stress), however, was low. This study provides a relevant method for combining functional activity, material property and analytical methods to improve patient monitoring.     

Intra- and interobserver reliability and agreement in three-dimensional computed tomography measurements of component positions after total knee arthroplasty

BackgroundAccurate evaluation of the postoperative position of total knee arthroplasty (TKA) components is crucial in the analysis of the association of alignments with clinical outcomes. The aim of this study was to investigate the reliability of measurements of component positions after TKA using three-dimensional computed tomography (3D-CT) reconstruction.MethodsTwo independent orthopedic surgeons (an attending surgeon and a fellow) examined 30 knees after primary TKA. The coronal, sagittal, and rotational positions of the femoral and tibial components were measured twice at an interval of six weeks on 3D-CT images reconstructed using ZedKnee software. Mean intra- and interobserver differences of measured angles were calculated, and the intra- and interobserver reliability was determined using intraclass correlation coefficients (ICCs), with agreement assessed by Bland–Altman analysis.ResultsThe mean intraobserver difference between alignment measurements for femoral and tibial components was < 2° (range 0.23–1.17°) and the mean interobserver difference was < 1° (range 0.22–0.97°). The intra- and interobserver ICCs were > 0.8 for all component positions. The only systematic bias found in the intra- and interobserver agreements occurred for the sagittal position of the femoral component.ConclusionThree-dimensional-CT measurements of component positions after TKA showed good intra- and interobserver reliability for the femoral and tibial components in coronal, sagittal and rotational positions. The intra- and interobserver agreements were favorable for all but the sagittal position of the femur. These results suggest that 3D-CT can be used to evaluate the alignment of all TKA components except for the sagittal position of the femur.     

A computed-tomography-scan-based template to place the femoral component in accurate rotation with respect to the surgical epicondylar axis in total knee arthroplasty

Background

Femoral rotational alignment is considered an essential factor for total knee arthroplasty because malrotation of femoral components results in poor outcomes. To obtain proper alignment, we developed a superimposable computed tomography (CT) scan-based template to intraoperatively determine the accurate surgical epicondylar axis (SEA), and evaluated the effectiveness of this CT template.

Robust automatic detection and removal of fiducial projections in fluoroscopy images: An integrated solution

Automatic detection and removal of fiducial projections in fluoroscopy images is an essential prerequisite for C-arm calibration. This paper presents an integrated solution to fulfill this task. A custom-designed calibration cage with a two-plane pattern of fiducials is utilized in our solution. The cage is attached to the C-arm image intensifier and acquired images are calibrated automatically by a three-step on-line calibration algorithm including fiducial projection detection, image calibration, and fiducial projection removal. A sequence of carefully designed image processing operations consisting of image binarization, connected-component labeling, region classification, adaptive template matching, and shape analysis, are developed for an accurate and robust localization of fiducial projections. A similarity measure that is proposed previously for image-based 2D–3D registration is employed in the adaptive template matching to improve the detection accuracy. Shape analysis based on the design information of the calibration cage is used to further improve the robustness of the detection. Thin-plate spline based vector transforms are used to correct the image distortion. The detected fiducial projections are then removed by an image inpainting technique based on the fast marching method for level set applications. Our in vitro experiments show on average 4 s execution time on a Pentium IV machine, a zero false-detection rate, a miss-detection rate of 1.6 ± 2.3%, and a sub-pixel localization error. Using a custom-made tool for checking accuracy, a forward projection error of 1.0 ± 0.4 pixels and a backward projection error of 0.3 ± 0.1 mm were found. We are confident that our solution is fast, robust, and accurate enough for image-guided interventional applications.     

In vivo evaluation of femoral and tibial graft tunnel placement following all-inside arthroscopic tibial inlay reconstruction of the posterior cruciate ligament

BackgroundThe arthroscopic all-inside tibial inlay technique represents a novel procedure for posterior cruciate ligament (PCL) reconstruction. However, in vivo investigations that evaluate the accuracy of this technique regarding anatomic graft tunnel placement are few. The objective of this study was to analyse the femoral and tibial tunnel apertures using computed tomography (CT) and compare these findings to recommendations in the literature.MethodsCT scans were obtained in 45 patients following single-bundle PCL reconstruction. The centres of the tibial and femoral tunnel apertures were correlated to measurement grid systems used as a radiographic reference.ResultsThe centre of the femoral tunnel aperture was located at 42.9% ± 9.4% of the total intercondylar depth and at 12.9% ± 7.2% of the total intercondylar height. The angle α for the femoral tunnel position was measured at 64.2° ± 10.0°. The centre of the tibial tunnel aperture was found at 51.8% ± 4.1% of the total mediolateral diameter of the tibial plateau. The superoinferior distance of the tibial tunnel aperture to the joint line was 9.6 mm ± 4.4 mm on frontal and 9.3 mm ± 3.4 mm on sagittal 3D-CT scans. The distance of the tibial tunnel aperture to the former physis line averaged to 0.8 mm ± 3.4 mm. Comparison to the corresponding reference values revealed no statistically significant difference.ConclusionArthroscopic tibial inlay reconstruction is an efficient procedure for precise replication of the anatomical footprint of the PCL.Level of evidenceIV, prospective case series     

Screw insertion in trabecular bone causes peri-implant bone damage

Secure fracture fixation is still a major challenge in orthopedic surgery, especially in osteoporotic bone. While numerous studies have investigated the effect of implant loading on the peri-implant bone after screw insertion, less focus has been put on bone damage that may occur due to the screw insertion process itself. Therefore, the aim of this study was to localize and quantify peri-implant bone damage caused by screw insertion.We used non-invasive three-dimensional micro-computed tomography to scan twenty human femoral bone cores before and after screw insertion. After image registration of the pre- and post-insertion scans, changes in the bone micro-architecture were identified and quantified. This procedure was performed for screws with a small thread size of 0.3 mm (STS, N = 10) and large thread size of 0.6 mm (LTS, N = 10).Most bone damage occurred within a 0.3 mm radial distance of the screws. Further bone damage was observed up to 0.6 mm and 0.9 mm radial distance from the screw, for the STS and LTS groups, respectively. While a similar amount of bone damage was found within a 0.3 mm radial distance for the two screw groups, there was significantly more bone damage for the LTS group than the STS group in volumes of interest between 0.3–0.6 mm and 0.6–0.9 mm.In conclusion, this is the first study to localize and quantify peri-implant bone damage caused by screw insertion based on a non-invasive, three-dimensional, micro-CT imaging technique. We demonstrated that peri-implant bone damage already occurs during screw insertion. This should be taken into consideration to further improve primary implant stability, especially in low quality osteoporotic bone. We believe that this technique could be a promising method to assess more systematically the effect of peri-implant bone damage on primary implant stability. Furthermore, including peri-implant bone damage due to screw insertion into patient-specific in silico models of implant-bone systems could improve the accuracy of these models.     

In-vitro validation of a non-invasive dual fluoroscopic imaging technique for measurement of the hip kinematics

Measurement of accurate in vivo hip joint kinematics in 6-DOF is difficult. Few studies have reported non-invasive measurements of the hip kinematics. The objective of this study was to validate a non-invasive dual fluoroscopic imaging system (DFIS) for measurement of hip kinematics. Bi-lateral hip joints of a cadaveric pelvic specimen were CT scanned to create bone models of the femur and pelvis, and subsequently tested in static and dynamic conditions inside the DFIS. The poses of the hip in space were then determined by matching the bone models with the fluoroscopic images. The pose data was compared to those obtained using a radio-stereometric analysis to determine the accuracy of the DFIS. The accuracy ± precision for measuring the hip kinematics were less than 0.93 ± 1.13 mm for translations and 0.59 ± 0.82° for rotations in all conditions. The repeatability of the DFIS technique was less than ±0.77 mm and ±0.64° in position and orientation for measuring hip kinematics in both static and dynamic positions. This technique could thus be a promising tool for determining 6-DOF poses of the hip during functional activities, which may help to understand biomechanical factors in hip pathologic conditions such as osteoarthritis and femoroacetabular impingement before and after surgical treatment.     

A multi-tissue mass-spring model for computer assisted breast surgery

The aim of this work was to develop and validate a 3D female breast deformation model for computer assisted breast surgery. Magnetic resonance (MR) image data of a patient undergoing breast biopsy, were acquired using two different protocols with the patient in prone position: (i) uncompressed breast and (ii) compressed breast, with lateral single breast compression, realized with a movable slab. The acquired images were then segmented using a semi-automatic procedure and from the extracted volumes of interest tetrahedral meshes representing skin, fat and mammary glands were generated. Tissue deformation was ruled by a mass-spring model: first, an iterative approximation algorithm was implemented to estimate the spring's rest length and stiffness, accounting for gravity force; then the resulting parameters were used to deform the uncompressed breast model in order to reach the real compressed one (ground truth). Results showed that gravity force applied to the mesh was properly compensated by the internal elastic forces, leading to a distance between the deformed mesh and the reference data of 0.036 ± 0.092 mm (median ± inter quartile range). The point to mesh residual distance between the deformed mesh and the ground truth was 1.224 ± 2.202 mm (median ± inter quartile range). Further investigation on a larger patient dataset is required for a more robust confirmation of model accuracy in predicting breast deformations.     

Improved detection of synovial boundaries in ultrasound examination by using a cascade of active-contours

Rheumatoid arthritis (RA) is a chronic multisystemic autoimmune disease, with an unclear etiopathogenesis. Its early diagnosis and activity assessment are essential to adjust the proper therapy. Among the different imaging techniques, ultrasonography (US) allows direct visualization of early inflammatory joint changes as synovitis, being also rapidly performed and easily accepted by patients. We propose an algorithm to semi-automatically detect synovial boundaries on US images, requiring minimal user interaction. In order to identify the synovia-bone and the synovia-soft tissues interfaces, and to tackle the morphological variability of diseased joints, a cascade of two different active contours is developed, whose composition corresponds to the whole synovial boundary.The algorithm was tested on US images acquired from proximal interphalangeal (PIP) and metacarpophalangeal (MCP) finger joints of 34 subjects. The results have been compared with a consensus manual segmentation. We obtained an overall mean sensitivity of 85 ± 13%, and a mean Dice's similarity index of 80 ± 8%, with a mean Hausdorff distance from the manual segmentation of 28 ± 10 pixels (approximately 1.4 ± 0.5 mm), that are a better performance than those obtained by the raters with respect to the consensus.     

DXA predictions of human femoral mechanical properties depend on the load configuration

The aim of this study was to evaluate the ability of dual energy X-rays absorptiometry (DXA) areal bone mineral density (aBMD) measured in different regions of the proximal part of the human femur for predicting the mechanical properties of matched proximal femora tested in two different loading configurations.36 pairs of fresh frozen femora were DXA scanned and tested until failure in two loading configurations: a fall on the side or a one-legged standing. The ability of the DXA output from four different regions of the proximal femur in predicting the femoral mechanical properties was measured and compared for the two loading scenarios.The femoral neck DXA BMD was best correlated to the femoral ultimate force for both configurations and predicted significantly better femoral failure load (R² = 0.80 vs. R² = 0.66, P < 0.05) when simulating a side than when simulating a standing configuration. Conversely, the work to failure was predicted similarly for both loading configurations (R² = 0.54 vs. R² = 0.53, P > 0.05).Therefore, neck BMD should be considered as one of the key factors for discriminating femoral fracture risk in vivo. Moreover, the better predictive ability of neck BMD for femoral strength if tested in a fall compared to a one-legged stance configuration suggests that DXA's clinical relevance may not be as high for spontaneous femoral fractures than for fractures associated to a fall.     

Joint line position in revision total knee arthroplasty: the role of posterior femoral off-set stems

BackgroundElevation of the joint line frequently occurs in revision total knee arthroplasty (RTKA) because of a wider flexion space than extension space. One solution to balance this flexion-extension space involves the introduction of couplers between the stem and femoral components, and the use of posteriorly offset femoral stems that we hypothesized would improve gap balancing and facilitate joint line restoration.MethodsWe retrospectively reviewed a selected series of 43 RTKA. Postoperative joint line height was subtracted from intended height using postoperative lateral radiographs. The value was negative if the joint line position was lowered, and positive if raised.ResultsForty knees were followed for a mean of 3.5 years. Mean postoperative joint line position change from intended position was 1.5 mm (range ? 2.5–7.5 mm). In 28 knees (70%), the joint line position was restored to within ± 2 mm of the intended position; in eight knees (20%), from 2–4 mm; and in four knees (10%), > 4 mm. Joint line position was raised in 32 knees (80%) and lowered in eight (20%). In the offset stem knees, the intended joint line position was 0.9 mm (range ? 1.2–3.4 mm) as compared with 3.2 mm (range ? 2.5–7.5 mm) for the straight stem knees.ConclusionsA coupler system between the femoral stem and femoral component restored the joint line in 70% of cases. The posterior offset stem provided increased posterior condylar offset, addressed the wider flexion space, provided better positioning of the stem, and restored the joint line.Level of evidenceTherapeutic Study Level IV     

Gender differences of the morphology of the distal femur and proximal tibia in a Korean population

PurposeWe conducted this study to determine whether the sizes of distal femurs and proximal tibiae in Korean men and women are different, and to assess suitability of the sizes of prostheses currently used in Korea.Materials and methodsWe performed morphological analysis of proximal tibia and distal femur on 115 patients (56 male, 59 female) using MRI to investigate a gender difference. Tibial mediolateral dimension (tMAP), tibial medial anteroposterior dimension (tMAP), tibial lateral anteroposterior dimension (tLAP) femoral mediolateral dimension (fML), femoral medial anteroposterior dimension (fMAP), and femoral lateral anteroposterior dimension (fLAP) were measured. The ratio of tMAP and tLAP to tML (plateau aspect ratio, tAP/tML × 100%), and that of fMAP and fLAP to fML (condylar aspect ratio, fAP/fML × 100%) were calculated. The measurements were compared with the similar dimensions of four total knee implants currently used.ResultsThe tML and tAP lengths showed a significant gender difference (P < 0.05). The plateau aspect ratio (tMAP/tML) revealed a significant difference between male (0.74 ± 0.05) and female (0.68 ± 0.04, P < 0.05). For morphotype of distal femur, males were found to have significantly large values (P < 0.05) in the parameters, except for fLAP. With regards to the ratio of the ML width to the AP length, the women showed a narrower ML width than the men. Both genders were distributed within the range of the dimensions of the prostheses currently used prostheses.ConclusionsKorean population revealed that women have smaller dimensions than male counterparts. In both genders, a relatively small size of prostheses matches distal femur and proximal tibia better among the implants currently used in Korea.     

Three-dimensional reconstruction of the lower limb from biplanar calibrated radiographs

Three-dimensional (3D) reconstruction of lower limbs is essential for surgical planning and clinical outcome evaluation. 3D reconstruction from biplanar calibrated radiographs may be an alternative to irradiation issues of CT-scan. A previous study proposed a two-step reconstruction method based on parametric models and statistical inferences leading to a fast Initial Solution (IS) followed by manual adjustments. This study aims to improve the IS using a new 3D database, a novel parametric model of the tibia and a different regression approach. The IS was evaluated in terms of shape accuracy on 9 lower limbs and reproducibility of clinical measurements on 22 lower limbs. Reconstruction time was also evaluated. Comparison to the previous method showed an improvement of the IS in terms of shape accuracy (1.3 vs. 1.6 and 2 mm respectively for both femur and tibia) and reproducibility of clinical measurements (i.e. 3.1° vs. 8.3° for neck-shaft-angle; 4.2° and 5° vs. 5° and 6° for tibial and femoral torsion respectively). The proposed approach constitutes a considerable step towards an automatic 3D reconstruction of lower limb.