Planning Of Total Knee Arthroplasty Research Articles

Numerical study of osteophyte effects on preoperative knee functionality in patients undergoing total knee arthroplasty.

Osteophytes are routinely removed during total knee arthroplasty, yet the preoperative planning currently relies on preoperative computed tomography (CT) scans of the patient's osteoarthritic knee, typically including osteophytic features. This complicates the surgeon's ability to anticipate the exact biomechanical effects of osteophytes and the consequences of their removal before the operation. The aim of this study was to investigate the effect of osteophytes on ligament strains and kinematics, and ascertain whether the osteophyte volume and location determine the extent of this effect. We segmented preoperative CT scans of 21 patients, featuring different osteophyte severity, using image-based active appearance models trained to identify the osteophytic and preosteophytic bone geometries and estimate the cartilage thickness in the segmented surfaces. The patients' morphologies were used to scale a template musculoskeletal knee model. Osteophytes induced clinically relevant changes to the knee's functional behavior, but these were variable and patient-specific. Generally, severe osteophytic knees significantly strained the oblique popliteal ligament (OPL) and posterior capsule (PC) relative to the preosteophytic state. Furthermore, there was a marked effect on the lateral collateral ligament and anterolateral ligament (ALL) strains compared to mild and moderate osteophytic knees, and concurrent alterations in the tibial lateral-medial translation and external-internal rotation. We found a strong correlation between the OPL, PC, and ALL strains and posterolateral condylar and tibial osteophytes, respectively. Our findings may have implications for the preoperative planning in total knee arthroplasty, toward reproducing the physiological knee biomechanics as close as feasibly possible.

The coronal alignment differs between two-dimensional weight-bearing and three-dimensional nonweight bearing planning in total knee arthroplasty.

The goal of this study is (1) to assess differences between two-dimensional (2D) weight-bearing (WB) and three-dimensional (3D) nonweight-bearing (NWB) planning in total knee arthroplasty (TKA) and (2) to identify factors that influence intermodal differences. Retrospective single-centre analysis of patients planned for a TKA with patient-specific instruments (PSI). Preoperative WB long-leg radiographs and NWB computed tomography were analysed and following radiographic parameters included: hip-knee-ankle angle (HKA) (+varus/-valgus), joint line convergence angle (JLCA), femorotibial subluxation and bony defect classified according to Anderson. Preoperative range of motion was also considered as possible covariate. Demographic factors included age, sex, and body mass index. A total of 352 knees of 323 patients (66% females) with a mean age of 66 ± 9.7 years were analysed. The HKA differed significantly between 2D and 3D planning modalities; varus knees (n = 231): 9.9° ± 5.1° vs. 6.7° ± 4°, p < 0.001; valgus knees (n = 121): -8.2° ± 6° vs. -5.5° ± 4.4°, p < 0.001. In varus knees, HKA (β = 0.38; p < 0.0001) and JLCA (β = 0.14; p = 0.03) were associated with increasing difference between 2D/3D HKA. For valgus knees, HKA (β = -0.6; p < 0.0001), JLCA (β = -0.3; p = 0.0001) and lateral distal femoral angle (β = -0.28; p = 0.03) showed a significant influence on the mean absolute difference. The coronal alignment in preoperative 3D model for PSI-TKA significantly differed from 2D WB state and the difference between modalities correlated with the extent of varus/valgus deformity. In the vast majority of cases, the 3D NWB approach significantly underestimated the preoperative deformity, which needs to be considered to achieve the planned correction when using PSI in TKA. Level III.

Accuracy and reproducibility of two-dimensional computed tomography-based positioning of femoral component rotational alignment in preoperative planning for total knee arthroplasty

BackgroundPoor rotation of the femoral component in total knee arthroplasty (TKA) can result in various postoperative complications, underscoring the critical importance of preoperative planning.PurposeTo improve the accuracy of femoral component positioning during TKA, this study compared the accuracy and repeatability of different two-dimensional (2D) computed tomography (CT) measurement methods for measuring the posterior condylar angle (PCA) in preoperative TKA planning.MethodsA retrospective analysis was conducted on 75 patients (150 knees) who underwent bilateral lower extremity computed tomography angiography (CTA) at Fuyang People's Hospital from January 2021 to July 2021. Three different methods were used to measure the PCA based on 2D CT images (axial CT slices) and three-dimensional(3D) models (femoral models reconstructed from CT data) in this study. Method 1: Single-plane 2D CT measurement, measuring PCA in the most obvious single-plane CT slice of the surgical transepicondylar axis (sTEA); Method 2: multi-plane 2D CT measurement, identifying and locating anatomical landmarks in multiple 2D CT slices and measuring PCA; Method 3: 3D model measurement, measuring PCA in the reconstructed femur 3D model. Compare the differences in PCA measurements between the three measurement methods. A positive PCA measurement was recorded when the sTEA was externally rotated relative to the posterior condylar line (PCL). Any difference exceeding 3° between the PCA measurement in the 2D CT and the PCA reference value in the 3D model was classified as an outlier. The intraclass correlation coefficient (ICC) and Bland–Altman method were utilized to assess the intra- and inter-observer reproducibility of the three measurement methods.ResultsThe PCA measurement in the single-plane 2D CT was 1.91 ± 1.94°, with a measurement error of − 1.22 ± 1.32° and 12.7% of outlier values. In the multi-plane 2D CT, the PCA measurement was 2.96 ± 1.68°, with a measurement error of -0.15 ± 0.91° and 6.0% of outlier values. The PCA measurement in the 3D model was 3.12 ± 1.69°. The PCA measurement in single-plane 2D CT was notably smaller than that in multi-plane 2D CT and 3D models, with no significant difference between the latter two. The multi-plane 2D CT showed significantly lower measurement error and outlier values than the single-plane 2D CT. All three PCA measurement methods exhibited high reproducibility (ICC: 0.93 ~ 0.97).ConclusionsUsing of multi-plane 2D CT for measuring PCA in preoperative planning of TKA has high reproducibility and accuracy, with fewer outlier values. We recommend preoperative measurement of PCA using muti-plane 2D CT to improve the accuracy of positioning the femoral component rotational alignment during surgery.

Development and Validation of an Artificial Intelligence Preoperative Planning and Patient-Specific Instrumentation System for Total Knee Arthroplasty.

Accurate preoperative planning for total knee arthroplasty (TKA) is crucial. Computed tomography (CT)-based preoperative planning offers more comprehensive information and can also be used to design patient-specific instrumentation (PSI), but it requires well-reconstructed and segmented images, and the process is complex and time-consuming. This study aimed to develop an artificial intelligence (AI) preoperative planning and PSI system for TKA and to validate its time savings and accuracy in clinical applications. The 3D-UNet and modified HRNet neural network structures were used to develop the AI preoperative planning and PSI system (AIJOINT). Forty-two patients who were scheduled for TKA underwent both AI and manual CT processing and planning for component sizing, 20 of whom had their PSIs designed and applied intraoperatively. The time consumed and the size and orientation of the postoperative component were recorded. The Dice similarity coefficient (DSC) and loss function indicated excellent performance of the neural network structure in CT image segmentation. AIJOINT was faster than conventional methods for CT segmentation (3.74 ± 0.82 vs. 128.88 ± 17.31 min, p < 0.05) and PSI design (35.10 ± 3.98 vs. 159.52 ± 17.14 min, p < 0.05) without increasing the time for size planning. The accuracy of AIJOINT in planning the size of both femoral and tibial components was 92.9%, while the accuracy of the conventional method in planning the size of the femoral and tibial components was 42.9% and 47.6%, respectively (p < 0.05). In addition, AI-based PSI improved the accuracy of the hip-knee-ankle angle and reduced postoperative blood loss (p < 0.05). AIJOINT significantly reduces the time needed for CT processing and PSI design without increasing the time for size planning, accurately predicts the component size, and improves the accuracy of lower limb alignment in TKA patients, providing a meaningful supplement to the application of AI in orthopaedics.

Enhancing Precision and Efficiency in Knee Arthroplasty: A Comparative Analysis of Computer-Assisted Measurements with a Novel Software Tool versus Manual Measurements for Lower Leg Geometry.

(1) Background: The aim of this prospective study was to evaluate measurement software in comparison with manual measurements using inter-observer and intra-observer variability on radiographs in the preoperative planning of total knee arthroplasty. (2) Methods: Two independent observers retrospectively measured the mechanical lateral proximal femoral angle (mLPFA), the mechanical lateral distal femoral angle (mLDFA), the joint line convergence angle (JLCA), the mechanical medial proximal tibial angle (mMPTA), the mechanical lateral distal tibial angle (mLDTA), the hip-knee angle or mechanical tibial-femoral axis angle (HKA), and the anatomical-mechanical angle (AMA) on 55 long-leg anteroposterior radiographs manually twice, followed by measurements using dedicated software. Variability between manual and computer-aided planning was assessed, and all measurements were performed a second time after 14 days in order to assess intra-observer variability. (3) Results: Concerning intra-observer variability, no statistically significant difference was observed regarding the software-based measurements. However, significant differences were noted concerning intra-observer variability when measuring the mLDFA and AMA manually. Testing for statistical significance regarding variability between manual and software-based measurements showed that the values varied strongly between manual and computer-aided measurements. Statistically significant differences were detected for mLPFA, mLDFA, mMPTA, and mLPTA on day 1, and mLPFA, mMPTA, and mLPTA on day 15, respectively. (4) Conclusions: Preoperative planning of leg axis angles and alignment using planning software showed less inter- and intra-observer variability in contrast to manual measurements, and results differed with respect to manual planning. We believe that the planning software is more reliable and faster, and we would recommend its use in clinical settings.

WITHDRAWN: Comparison of the application value of 3D printed osteotomy guide plate and artificial intelligence 3D surgical planning in artificial total knee arthroplasty

In this study, we aimed to assess the impact of personalized 3D printing osteotomy guide plates and artificial intelligence (AI) three-dimensional surgical planning in total knee arthroplasty (TKA) for knee osteoarthritis. The clinical data of 60 knee osteoarthritis patients were collected, with 30 undergoing personalized 3D printing osteotomy guide plate-assisted TKA (3D-TKA) and 30 undergoing AI 3D surgical planning-assisted TKA (AI-TKA). Surgical outcomes were comprehensively evaluated, including operation time, intraoperative blood loss, postoperative drainage, hospitalization duration, surgical angles (HKA, FTC, FFC), pain scores (VAS), and Hospital for Special Surgery Scores (HSS).Significant differences emerged between the two groups, favoring the 3D-TKA approach. Notably, the 3D-TKA group exhibited a shorter operation time (81.4±8.9 min vs. 72.9±10.0 min), reduced intraoperative blood loss (160.1±24.3 ml vs. 174.7±25.7 ml), lower postoperative drainage (199.5±29.6 ml vs. 223.8±29.2 ml), and a shorter hospital stay (7.7±1.3 d vs. 6.8±1.6 d) (P<0.05). In the immediate postoperative period, the 3D-TKA group demonstrated significantly lower VAS scores (5.4±0.6 vs. 6.2±1.2) (P<0.05). However, there were no significant differences in measured angle deviations, pain scores, and HSS scores at various time points between the groups (P>0.05).Collectively, both 3D-TKA and AI-TKA approaches yielded improved surgical outcomes and precision for treating knee osteoarthritis. While AI-TKA demonstrated advantages in terms of operation time and hospitalization duration, the 3D-TKA approach proved superior in reducing perioperative blood loss and early postoperative pain. These findings underscore the potential of advanced technological interventions to optimize surgical efficacy and patient outcomes in total knee arthroplasty.

Preoperative Joint Distraction Imaging and Planning Protocol for Total Knee Arthroplasty

BackgroundCurrent preoperative total knee arthroplasty (TKA) planning strategies are bone-referencing and do not consider the ligamentous profile of the knee. This study assessed the mean Hip-Knee-Ankle (HKA) angle of the planned Distracted Alignment (DA), an alignment output using a joint distraction radiology and planning protocol, which incorporates preoperative evaluation of ligament laxity. MethodsA retrospective study of 144 knees undergoing TKA was performed. Each patient received a preoperative computer tomograph scan, a weight-bearing antero-posterior knee radiograph, and distracted knee radiographs in extension and flexion. The imaging was used to develop a preoperative DA plan aiming for medio-lateral and extension-flexion space balance. The mean DA, weight-bearing, and arithmetic HKA angles were compared to each other, and to the HKA of a healthy nonarthritic population. ResultsThe mean weight-bearing, arithmetic, and planned DA HKA angles were 4.8° (interquartile range [IQR] 6.5°) varus, 0.4° (IQR 4.5°) varus, and 2.2° (IQR 4.0°) varus, respectively. This compares to a healthy adult HKA angle of 1.3° varus. The difference between the planned DA and arithmetic HKA angles was greater than 3° for 36% of the patients in the study population. ConclusionsThe planned DA HKA angle was fundamentally different from the arithmetic HKA angle, but comparable to a healthy population. Considering both hard and soft tissue information of the knee, we believe the planned DA resulting from the joint distraction radiology protocol allows for optimized preoperative surgical planning in TKA. This protocol has been shown to be clinically viable.

Experience of use of the individual cutting block «5 in 1» using total knee arthroplasty

BACKGROUND: Total knee arthroplasty is the most progressively developing direction in the modern orthopaedic world. With the new visualization technologies, a whole new field of computer-assisted orthopaedic surgery has emerged. Generally, three groups can be distinguished in computer-assisted orthopedic surgery. The 1st group the use of individual resection blocks, templates or guides remains the most relevant today. However, the use of currently existing individual resection blocks, according to the literature, has contradictory results.&#x0D; CLINICAL CASES DESCRIPTION: This work presents the author's developed technique of a new preoperative 3D modeling for total knee arthroplasty using individual resection blocks. The paper presents a clinical case demonstrating the effectiveness of the new technique.&#x0D; CONCLUSION: The strategy CT+MRI, in our opinion, is the optimal solution not only for competent preoperative planning of total knee arthroplasty, but also for designing individual resection blocks. Our individual resection blocks allowed us to improve the accuracy of total knee arthroplasty.

Patellar medial-lateral position can be used to correct the effect of leg rotation on preoperative planning in total knee arthroplasty for varus knees

BackgroundLower limb malrotations can be observed in long leg radiographs, affecting the measurement of the angle between the mechanical and anatomical axes. The purposes were to analyze the effect of limb rotation and to evaluate the accuracy of the corrected angle between the mechanical and anatomical axes based on the patellar ML position. HypothesisThe hypothesis was that the correction of the angle between the mechanical and anatomical axes according to the patellar ML position can reduce the error from the angle in the true AP view in most of the knees. Patients and methodsA total of 100 consecutive knees with varus deformity undergoing primary total knee arthroplasty were included. Computed tomography images were digitally reconstructed in the neutral position, and internally and externally rotated at 10° and 20°, respectively. The patellar ML position relative to the medial (0%) and lateral (100%) epicondyles and the angle between the mechanical and anatomical axes of the femur were measured. The corrected angle between the mechanical and anatomical axes was calculated using the averaged translational ratio. ResultsIn the neutral position, the patellar center position was 56.1% (standard deviation [SD]=4.7%), which was 31.4% (SD=7.2%) and 80.2% (SD=5.4%) in the 20° internal and external rotation, respectively. The angle between the mechanical and anatomical axes was 2.6° (SD=2.0°) and 8.1° (SD=2.1°) in the 20° internal and external rotation, respectively. On average, if the patellar center shifted 10%, the change of the angle between the mechanical and anatomical axes of the femur was 1.13°. Applying the corrected angle, a discrepancy from the neutral position decreased. ConclusionThe method to correct the angle between the mechanical and anatomical axes according to the patellar ML position can be used to reduce the measurement error for preoperative planning using a long leg radiograph. Level of evidenceIII.

Sagittal femoral bowing contributes to distal femoral valgus angle deviation in malrotated preoperative radiographs

BackgroundThe coronal whole-leg radiograph is generally used for preoperative planning in total knee arthroplasty. The distal femoral valgus angle (DFVA) is measured for distal femoral bone resection using an intramedullary guide rod. The effect of coronal and sagittal femoral shaft bowing on DFVA measurement in the presence of malrotation or knee flexion contracture has not been well reported. The objectives of this study were: (1) to investigate the effects of whole-leg malrotation and knee flexion contracture on the DFVA in detail, (2) to determine the additional effect of coronal or sagittal femoral shaft bowing.MethodsWe studied 100 consecutive varus and 100 valgus knees that underwent total or unicompartmental knee arthroplasty. Preoperative CT scans were used to create digitally reconstructed radiography (DRR) images in neutral rotation (NR, parallel to the surgical epicondylar axis), and at 5° and 10° external rotation (ER) and internal rotation (IR). The images were also reconstructed at 10° femoral flexion. The DFVA was evaluated in each DRR image, and the angular variation due to lower limb malposition was investigated.ResultsThe DFVA increased as the DRR image shifted from IR to ER, and all angles increased further from extension to 10° flexion. The DFVA variation in each position was 1.3° on average. A larger variation than 2° was seen in 12% of all. Multivariate regression analysis showed that sagittal femoral shaft bowing was independently associated with a large variation of DFVA. Receiver operating characteristic analysis showed that more than 12° of sagittal bowing caused the variation.ConclusionIf femoral sagittal bowing is more than 12°, close attention should be paid to the lower limb position when taking whole-leg radiographs. Preoperative planning with whole-leg CT data should be considered.

Robotics versus personalized 3D preoperative planning in total knee arthroplasty: a propensity score-matched analysis

PurposeLower limb alignment is crucial in total knee arthroplasty (TKA). Previous studies have shown that robotics and personalized three-dimensional (3D) preoperative planning could improve postoperative alignment accuracy compared with conventional TKA, but comparison between the above two techniques has never been reported. The authors hypothesized that robotics may be superior to personalized 3D preoperative planning in terms of postoperative alignment in primary TKA, with similar patient-reported outcome measures (PROMs) but higher cost and longer operative time.MethodsA consecutive series of patients who received TKA in our center from September 2020 to January 2021 were enrolled retrospectively. After 1:2 matching, 52 and 104 patients were included and divided into study group for robotics and control group for personalized 3D preoperative planning, respectively. Multiple postoperative alignment angles were measured, and clinical features such as operation and tourniquet time, length of hospital stay and hemoglobin (Hb) were recorded. Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were used to evaluate clinical results.ResultsCompared with control group, robotics group had significantly lower frontal femoral component angle (FFC) and frontal tibial component angle (FTC) absolute deviation (P < 0.05). It also had less outliers in hip–knee–ankle angle (HKA), FTC, lateral femoral component angle (LFC) and lateral tibial component angle (LTC) (P < 0.05). Hb loss of robotics group was significantly lower than control group (P < 0.001), while the operation and tourniquet time were longer (P < 0.001). There was no significant difference in KSS and WOMAC scores between two groups.ConclusionCompared with control group, patients in robotics group had significantly less malalignment, malposition, Hb loss, but similar PROMs. The operations in robotics group spent longer operation time and cost more compared with control group.Trial registration: The Chinese Clinical Trial Registry, ChiCTR2000036235. Registered 22 August 2020, http://www.chictr.org.cn/showproj.aspx?proj=59300.Level of evidenceIII.

Preoperative planning of total knee arthroplasty: reliability of axial alignment using a three-dimensional planning approach.

Preoperative templating of total knee arthroplasty (TKA) can nowadays be performed three-dimensionally with software solutions using computed tomography (CT) datasets. Currently there is no consensus concerning the axial orientation of TKA components in three-dimensional (3D) planning. To assess intra-/inter-observer reliability of detection of different bony landmarks in planning axial component alignment using axial CT images and 3D reconstructions. Intra- and inter-observer reliability of determination of four predefined axial femoral and tibial axes was calculated using data from CT scans. Axes determination was performed on the axial slices and on the 3D reconstruction using preoperative planning software. In summary, 61 datasets were analyzed by one medical student (intra-observer reliability) and 15 datasets were analyzed by four different observers independently (inter-observer reliability). For the femur, clinical epicondylar axis and posterior condylar axis showed the best reliability with an inter-observer variability of 0.7° and 0.5°, respectively. For the tibia, posterior condylar axis provided best reliability (inter-observer variability: 1.7°). Overall variability was greater for tibial than for femoral axes. Reliability of axis determination was more accurate using axial CT slices rather than 3D reconstructions. The femoral clinical epicondylar axis is highly reliable. Landmarks for the tibia are not as easily identifiable as for the femur. The tibial posterior condylar axis presents the axis with highest reliability. Based on these results, clinical epicondylar axis for orientation of the femoral TKA component and posterior condylar axis for the tibial implant, both defined on axial slices can be recommended.

Efficacy Analysis of Selection of Distal Reference Point for Tibial Coronal Plane Osteotomy during Total Knee Arthroplasty: A Literature Review.

Total knee arthroplasty is an effective treatment for end‐stage knee osteoarthritis. The tibial platform osteotomy must take full account of the coronal plane, the sagittal plane, and the rotational alignment of the tibial prosthesis. During surgery, individual differences in the coronal alignment of the tibia need to be taken into account as poor alignment after surgery can lead to rapid wear of the tibial platform, reducing the longevity of the prosthesis and adversely affecting quality of life. Intraoperative tibial osteotomies are often performed using extramedullary alignment. When an extramedullary alignment approach is used, the proximal tibial osteotomy guide is usually placed in the medial third of the tibial tuberosity. There is no consensus on the most reliable anatomical landmarks or axes for achieving distal tibial coronary alignment. Anatomical points or reference axes that are highly reproducible and precise need to be identified. From available data it appears that most surgeons use the extensor hallucis longus tendon, the second metatarsal, and the anterior tibial cortex to determine the distal localization point. However, its accuracy has not been confirmed in clinical and radiographic data, and the alignment concept and preoperative planning for total knee arthroplasty has paid more attention to rotational alignment, but there are few studies on the coronal alignment of the tibia. This article reviews the recent use of the distal tibial coronal osteotomy reference point in total knee arthroplasty. However, due to there being only a small number of studies available, the evidence collected is insufficient to prove that a certain reference axis has obvious advantages and a combination of different reference points is needed to achieve the ideal lower extremity force line angle.

Preoperative TKA Planning on Long-Leg Hip-Knee-Ankle Radiographs and It’s Impact on Postoperative Coronal Knee Alignment

The importance of measuring of the angle between the mechanical and anatomical femoral axis (РУЛ) during the preoperative total knee arthroplasty (TKA) planning is not recognized by all. Some surgeons believe that it is acceptable to set distal femoral resection guide at 6° or 7° in all cases or adjust femoral resection guide FVA accordingly with patient height.We conducted two studies. One — retrospective analysis of radiographs of patients with TKA performed since 1.09.2014 till 31.01.2015 (n = 261, 273 TKA). In this cohort, we were looking for correlation between the parameters obtained on long hip-knee-ankle radiographs (FVA, coronal knee alignment) and gender, age, body mass index (BMI) and height, as well as the implant model and the level of constraint. After that we conducted a prospective, randomized trial with TKA performed since 1.02.2015 till 31.05.2015 (n = 225, 225 TKA). The patients were randomly divided into two groups. In the “individual FVA” group (n = 121), the distal femoral resection guide FVA was set accordingly with measured FVA, in the control group (n = 104) — at 7° (average FVA for the Sverdlovsk area patients’ population). We compared TKA x-ray results of both groups.Results. First stage. We found no correlation between FVA and age, BMI, height and sex of patients (p0.05). After TKA residual varus deformity of more than 3° (malalignment) (3.9±1.06) was observed in 7% of cases (19 joints). We found correlation between coronal knee malalignment after TKA and two factors: BMI and initial severity of varus deformity (p = 0.003 and p0.001). Second stage. In the control group we’ve seen femoral component deviation of more than 3° from the perpendicular to neutral mechanical axis (malposition) 3 times more often then in the “individual FVA” group (9 vs. 3, p = 0.021).Conclusions. We did not identify the dependence of FVA on sex, age, BMI and height. With initial varus of more than 20° and BMI of more than 30 kg/m2, the risk of coronal components malalignment is increased. The average FVA in patients of Sverdlovsk area is 6,7±1,5° (3-11°). Implementation of preoperative FVA measurement and following femoral distal cut adjustments improves femoral component positioning and overall leg alignment postoperatively.

Comparison of knee joint orientation in clinically versus biomechanically aligned computed tomography coordinate system

BackgroundPreoperative planning of total knee arthroplasty is usually performed using knee-centred computed tomography (CT) data sets. The disadvantage of these data sets is having no account of the biomechanical axis of the lower extremity, known as Mikulicz line. It aligns the femoral head to the middle of the talocrural joint. For optimal prosthesis arrangement, the knee CT data set must therefore be brought in congruency with this line of loading to achieve the best results and eliminate rotational malalignments.This study aims to establish a relation between the knee-centred clinical coordinate system (CCS) and a biomechanical coordinate system (BCS) based on the Mikulicz line. MethodsCT data sets of 45 lower extremities were evaluated. Using VG Studio Max, a visualisation and measurement software program; each CT data set was aligned according to the CCS and BCS. After superimposing both the aligned data sets, the deviations of both coordinate systems in all three planes were measured with the centre of the knee defined as the origin. ResultsFor the coronal plane, the CCS was demonstrated to be 2.54° in adduction compared to the BCS [standard deviation (SD) = 1.8°]. In sagittal view, the CCS was demonstrated to be 0.3° retroversed (SD = 3.27°). Finally, the deviation in the axial plane showed an outward rotation of 3.39° (SD = 1.99°). The alignment as well as the measurements demonstrated high intraobserver and interobserver reproducibility. ConclusionBoth coordinate systems can be established in knee-centred CT data sets in a reproducible manner. Clearly, the CCS differs significantly from the BCS describing the biomechanical axis, but mathematical-based adaptations and corrections can be performed. The translational potential of this articleThe findings of this study allow a mathematical conversion of a knee CT to the biomechanical axis of the leg.

Radiographic Measurement of Femoral Lateral Bowing and Distal Femoral Condyle Resection Thickness: Variances and Effects on Total Knee Arthroplasty Planning.

Background:Accurate evaluation of the plain radiography of lower limb is critical for preoperative planning of total knee arthroplasty (TKA). We aimed to investigate the effect of femoral lateral bowing and rotation on the radiographic measurements of distal femoral condyle resection thickness (DRT) and the distal femoral resection valgus angle (FVA).Methods:We analyzed 246 three-dimensional femoral models generated from computed tomography images of 123 patients, acquiring projected contours in seven positions – 20° and 10° internal rotation; 0° rotation; 10°, 20°, 30°, and 40° external rotation – for each model. Medial and lateral condyle DRTs, femoral shaft lateral bowing angle (FBA), and distal FVA were determined for each position. Linear mixed effect model was used to determine the effect of degree of femur rotation on repeated measurements of DRT or FVA.Results:FBA significantly affected the FVA and DRT (Pearson's R = 0.767 and −0.408, respectively; P < 0.000). Samples were divided into three groups according to the FBA measured in neutral position: FBA <0°: DRT 3.75 ± 1.30 mm, FVA 4.53° ± 1.27°; FBA >0° but <3°: DRT 3.39 ± 1.31 mm, FVA 5.92° ± 1.31°; FBA >3°: DRT 2.22 ± 1.31 mm, FVA 7.37° ± 1.31°. From simulated 20° internal rotation to 40° external rotation in each femoral model, the average variation ranges of radiographically measured DRT, FVA, and FBA were 0.50 ± 0.28 mm, 2.93° ± 0.96°, and 10.33° ± 1.90°, respectively, with no significant differences among the FBA groups. The degree of femoral rotation significantly affected the FVA (F = 62.148, P < 0.000), whereas there was no effect on condyle resection thickness (F = 0.4705, P = 0.494).Conclusions:Axial femoral rotation has less effect on radiographic measurements of differences in the DRT than on those of the distal FVA.

The fibular head projection is of limited use as a radiographic landmark in preoperative planning of total knee arthroplasty.

The projection of the fibular head is recommended as a quality indicator of a correct radiographic projection. However, this landmark has yet to be sufficiently validated. The MRIs of 334 knee joints were included. On the MRIs, the distance between the FH and lateral tibial cortical bone was simulated in projections parallel to surgically relevant axes. Then, the Pearson correlation coefficient between the distance of the FH to the lateral tibial cortical bone and the projection plane causing this was determined. A projection of the knee joint perpendicular to Akagi's line projected the center of the fibular head on average 4.8±2.9mm laterally of the tibial cortical bone, parallel to the maximum mediolateral axis of the tibia 7.5±3.4mm, parallel to the posterior condylar axis 5.6±3.6mm and parallel to the surgical epicondylar axis 6.1±3.5mm laterally of the tibial cortical bone. An almost linear correlation was seen, with 1.9° tilting of the projection plane per mm change in distance between the fibular head and tibial cortical bone. At the same time, the interindividual scatter was over 60°. The rule of thumb for a partial overlap of the fibular head by the tibia in the case of a correct antero-posterior projection plane was also confirmed. However, a considerable interindividual variability of the position of the FH was found, which limits a conclusion regarding the quality of the radiographic projection on the basis of the position of the fibular head.

Modelo predictivo para determinar el tamaño de los componentes femoral y tibial en artroplastia total de rodilla

PurposesObjectives technique of preoperative planning in total knee arthroplasty is to set up accurate components, prosthetic under a proper alignment, according to the axial axis of the limb to intervene. To determine the efficacy of the predictive model that sets the size of the femoral and tibial components with patients who underwent primary knee arthroplasty. Material and methodologyRetrospective, longitudinal study, observational, there were recruited patients submitted to total knee arthroplasty with the design Sigma PFC, realized between January, 2013 to December, 2014 in 80 women and 43 men registered with an age average of 67 years. The average in height, weight and CMI they were 1.65cm, 76.6kg and 28.4 Kg/m2 respectively. ResultsThe models predicted the size of the components exactly in 76% for the femur and 83% for the tibial. All the predictions were inside a size±1 number as regards the real components and that they were implanted at the moment of the surgery, with a prediction of 100%. For both models, the height was the most important predictor to determine the size of the components, continued by the genre and the age. ConclusionThis model predictive has the aptitude to be high precise although he allows to predict a better size, we must have all the sizes available in the surgical room. The prediction model facilitates the preparation of the femur and the shinbone with the final size of the components.

Contribution of patient-specific cutting guides to lower limb alignment for total knee arthroplasty

Patient-specific cutting guides (PSCG) are an extension of preoperative planning for total knee arthroplasty (TKA). We wanted to evaluate their contribution to postoperative lower limb alignment. This study involved primary TKA cases being performed with PSCG between 10/05/2010 and 05/03/2013 and then followed prospectively. The analysis involved the PSCG usage and postoperative measurement of the patient's HKA, medial distal femoral joint angle (MDFA) and medial proximal tibia joint angle (MPTA). Of the 104 eligible cases, 68 were included; 11 of these cases were not performed completely with the PSCG as initially planned. Thus we compared these 11 cases with the 57 where PSCG were used. The preoperative HKA in the included cases was 175.8°±7.8; the postoperative angles on average were 179.2°±2.9 for the HKA, 89.9°±1.6 for the MDFA and 89.0°±2.3 for the MPTA. The average postoperative deviation from the target values was 2.22°±2.14 for the HKA angle, 1.07°±1.15 for the MDFA and 1.66°±1.90 for the MPTA. There were no significant differences between the two groups in any of the measurements. The lower limb alignment goal was achieved in 50 cases (73%), with 41 of these achieved with PSCG (82%). Of the 18 cases where the target was not achieved, PSCG were used 16 times (88%). In this study cohort, lower limb alignment was not significantly closer to an HKA of 180° or achieved more often with the use of PSCG versus standard instrumentation. Since the results of the two groups can be superimposed, we found no evidence that use of PSCG improves postoperative lower limb alignment. Level of evidenceIV. Study typeCohort.

Digital templating in total knee and hip replacement: an analysis of planning accuracy

The aim of this study was to determine how well pre-operative size selection for total knee and hip arthroplasties based on the digital imaging with and without additional referencing correlated with the size actually implanted. Size selection planning of total knee arthroplasty by digital templating was documented in 46 cases with reference ball (group A) and in 48 cases without ball (group B). In addition, prospective analysis of pre-operative planning was conducted for 52 acetabular components with reference ball (group C) and 69 without ball (group D) as well as stem planning in 38 cases with ball (group E) and 54 cases without ball (group F). The data were analysed and compared with the size of the final component selected during surgery. The correlation between planned and implanted size for total knee arthroplasty in group A resulted in femoral anteroposterior (AP) r = 0.8622 and lateral r = 0.8333 and in group B AP r = 0.4552 and lateral r = 0.6950. Tibial in group A was AP r = 0.9030 and lateral r = 0.9074 and in group B AP r = 0.7000 and lateral r = 0.6376. For the acetabular components, the results in group C were r = 0.5998 and group D r = 0.6923. For stems, group E was r = 0.5306 and group F r = 0.5786. No correlation between BMI and the difference between planned and implanted size was found in any of the groups. In the case of total hip arthroplasty there was a relatively low correlation between planned and implanted sizes with or without reference ball. For total knee arthroplasties the already high precision of size planning was further improved by the additional referencing with a reference ball.