Tibial Mechanical Axis Research Articles

Basics of Coronal Plane Deformity Correction

High tibial osteotomy (HTO) and distal femoral osteotomy (DFO) are utilized to correct knee malalignment in patients with coronal plane deformities. Identifying the deformity of the lower extremity using a standardized, reproducible approach is critical prior to correction of lower limb malalignment with an osteotomy procedure. Appropriate radiographs, including bilateral long-leg standing films, are critical to measure the anatomical and/or mechanical axes and calculate the required degree of correction. The femoral and tibial mechanical axes, malalignment (varus or valgus), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) should be measured during coronal plane deformity analysis and accounted for during surgical planning. This paper focuses on the surgical technique for medial opening and lateral closing wedge HTO, as well as medial closing and lateral opening wedge DFO.

Predicting robotic-assisted total knee arthroplasty operating time : benefits of machine-learning and 3D patient-specific data.

AimsNo predictive model has been published to forecast operating time for total knee arthroplasty (TKA). The aims of this study were to design and validate a predictive model to estimate operating time for robotic-assisted TKA based on demographic data, and evaluate the added predictive power of CT scan-based predictors and their impact on the accuracy of the predictive model.MethodsA retrospective study was conducted on 1,061 TKAs performed from January 2016 to December 2019 with an image-based robotic-assisted system. Demographic data included age, sex, height, and weight. The femoral and tibial mechanical axis and the osteophyte volume were calculated from CT scans. These inputs were used to develop a predictive model aimed to predict operating time based on demographic data only, and demographic and 3D patient anatomy data.ResultsThe key factors for predicting operating time were the surgeon and patient weight, followed by 12 anatomical parameters derived from CT scans. The predictive model based only on demographic data showed that 90% of predictions were within 15 minutes of actual operating time, with 73% within ten minutes. The predictive model including demographic data and CT scans showed that 94% of predictions were within 15 minutes of actual operating time and 88% within ten minutes.ConclusionThe primary factors for predicting robotic-assisted TKA operating time were surgeon, patient weight, and osteophyte volume. This study demonstrates that incorporating 3D patient-specific data can improve operating time predictions models, which may lead to improved operating room planning and efficiency.Cite this article: Bone Jt Open 2022;3(5):383–389.

Use of Blumensaat's line for assessment of cranial tibial subluxation in dogs with cranial cruciate ligament deficiency.

This study aimed to determine whether Blumensaat's line, a consistently present radiographic feature delineating the peak of the femoral intercondylar fossa, could be used to assess for cranial tibial subluxation in canine stifles with cranial cruciate ligament disease. Thirty sequential, neutrally positioned, standing-angle stifle radiographs were taken from dogs presenting to a specialist referral centre for treatment of cruciate ligament disease. Thirty similarly positioned radiographs of healthy canine stifles were used as a control group. The radiographs were anonymised and submitted to blinded observers for measurement of the tibial plateau angle, patella tendon angle, Blumensaat's line length and the length of Blumensaat's line cranial to the tibial mechanical axis. Finding that the tibial mechanical axis intersects Blumensaat's line cranial to its midpoint, as a marker of cranial tibial subluxation, had a positive predictive value of 76% for subsequent surgical identification of cruciate ligament disease. Tibial cranial subluxation is detectable and quantifiable radiographically using the intersection of the tibial mechanical axis and Blumensaat's line. Once quantified, this measurement could be used both as a radiographic marker of cruciate ligament disease and to adjust tibial osteotomy procedures to minimise the risk of under advancement of the tibial tuberosity resulting in a persistently unstable stifle.

Smaller femoral neck anteversion in varus knees than in healthy and valgus knees.

It is important to investigate anatomical differences of the femur and tibia three-dimensionally between varus and valgus knees to enhance surgical approaches and better understand structural factors related to specific patterns of osteoarthritis progression. Three-dimensional femoral and tibial bone models were reconstructed from transverse computed-tomography scans in varus osteoarthritis (43 knees), valgus osteoarthritis (40 knees), and healthy (32 knees) groups. Different coordinate systems were defined in each femoral bone model ("Knee" and "Hip" Coordinate System). Femoral neck inclination, lateral bowing, anterior bowing, and neck anteversion were measured and compared between knee and hip coordinate systems. Those parameters were also compared between varus, valgus, and healthy groups. The tibial anterior and lateral bowing, external torsion and the fibular axis relative to the tibial mechanical axis were measured and compared between varus and valgus groups. Femoral neck anteversion was significantly 1-2° greater in the hip coordinate system compared to the knee coordinate system. Femoral neck anteversion was significantly smaller in varus knees than in healthy or valgus knees, with average difference of approximately 5°. The knee and hip joint are often rotated externally relative to the trunk axis in patients with varus osteoarthritis, perhaps maintaining the geometric relations between pelvis and proximal femur (including peripheral hip muscles) regardless of knee deformities. The fibular axis was inclined slightly valgus and posteriorly in two groups. The results may inform hypotheses on, and future studies of, skeletal morphologic development and factors contributing to the progression of knee osteoarthritis.

Preliminary outcomes of the introduction of computer assistance in total knee arthroplasty at the Basse-Terre hospital center in Guadeloupe

Background: Computer-assisted total knee arthroplasty (TKA) is associated with significant precision during the surgical installation of prosthesis. We aimed to compare the radiological outcomes between the prostheses’ positioning assisted by a passive computer system and with the conventional technique.Methods: Participants included in this study were divided into two mixed groups based on the use of classical procedure and the computer navigated method during the positioning of implants during fractures. Clinical factors such as degrees of knee amplitude, knee IKS score and IKS function score and radiological features including the stage of osteoarthritis according to Ahlbäck classification, HKA and HKS angles, femoral and tibial mechanical axes, tibial slope prior and after the surgical procedure were measured in each group and then were compared.Results: Of a total of 92 patients, there were 63 women and 29 men; among which 42 patients for were treated with conventional TKA and 50 patients benefited from navigated TKA. 76 patients had stage IV osteoarthritis, 15 patients were at stage III of Albäck classification, and one patient at stage V. The postoperative HKA angle was found to be better in the navigated cohort with a statistically significant difference. The IKS knee and function scores are significantly better in the navigated cohort.Conclusions: Computer surgical navigation practiced during the total arthroplasty of the knee highlighted significant improvement in the positioning of the implants; and is associated with better functioning of the knees.

Steep lateral tibial slope measured on magnetic resonance imaging is the best radiological predictor of anterior cruciate ligament reconstruction failure.

To identify the radiological predictive risk factors for anterior cruciate ligament reconstruction (ACLR) failure, compare the diagnostic accuracies of different parameters of conventional radiographs and magnetic resonance imaging (MRI), and determine the cutoff values for patients at higher risk. Twenty-eight patients who were diagnosed as ACLR failure via MRI or arthroscopic examination were included in the study group. They were matched to 56 patients who underwent primary ACLR with the same surgical technique and without graft failure at the minimum 24-month follow-up by age, sex, and body mass index. On true lateral whole-leg radiographs, the posterior tibial slope (PTS) referenced to the tibial mechanical axis (PTS-mechanical), PTS referenced to the tibial proximal anatomical axis (PTS-anatomical), and anterior tibial translation (ATT) were measured. On the sagittal slices of MRI, the medial tibial slope (MTS), medial tibial plateau (MTP) subluxation (MTPsublx), lateral tibial slope (LTS), and lateral tibial plateau (LTP) subluxation (LTPsublx) were obtained. Receiver operator characteristic (ROC) curves were constructed to compare the diagnostic performance and determine the cutoff values of different radiological parameters. The study group demonstrated higher values of PTS-mechanical (10.7° ± 2.9° vs 8.7° ± 1.9°, p = 0.003), PTS-anatomical (13.2° ± 2.8° vs 10.5° ± 2.5°, p < 0.001), ATT (10.7 ± 3.3mm vs 8.9 ± 2.2mm, p = 0.014), LTS (9.4° ± 2.1° vs 5.5° ± 2.5°, p < 0.001), and LTPsublx (8.2 ± 2.8mm vs 6.8 ± 1.9mm, p = 0.009) as compared with the control group. The area under the ROC curve of LTS was significantly larger than that of PTS-mechanical (p = 0.006) and PTS-anatomical (p = 0.020). Based on the maximum Youden indexes, the cutoff values of PTS-mechanical, PTS-anatomical, and LTS were 10.1° (sensitivity, 64.3%; specificity, 78.6%), 12.0° (sensitivity, 71.4%; specificity, 71.4%), and 7.7° (sensitivity, 85.7%; specificity, 80.4%), respectively. Due to the morphological asymmetry of the MTP and LTP, steep LTS measured on MRI is the best radiological predictor of ACLR failure. Detailed measurement of the LTS on MRI is recommended to evaluate the risk of ACLR failure prior to the surgery. III.

Coronal curvature of tibial leads to malalignment of tibial prosthesis after total knee arthroplasty

To investigate the effect of tibial coronal curvature on the alignment of tibial prosthesis in patients undergoing total knee arthroplasty (TKA). From July 2019 to April 2021, 100 patients with knee osteoarthritis were treated with total knee arthroplasty. Before operation, the full-length films of lower limbs were taken and the tibial bowing angle(TBA) was measured. TBA more than 2° was tibial bending, which was divided into tibial bending group and non bending group. There were 40 cases in tibial bending group, 9 males and 31 females, aged 56 to 84 years old with an average of (69.22±7.10) years. There were 60 cases in the non bending group, 19 males and 41 females, aged from 51 to 87 years old with an average of (70.80±7.21) years. The preoperative tibial length (TL) and medial proximal tibial angle (MPTA) were measured and compared between the two groups. The full-length X-rays of the lower limbs were taken again 3 days to 1 week after operation. The medial angle of the tibial component coronal aligement angle (TCCA) and the outilier rate of force line of the tibial prosthesis were measured and compared between the two groups. Pearson method was used to analyze the correlation between TCCA and age, TCCA and height, TCCA and weight, TCCA and BMI, TCCA and TBA, TCCA and TL, TCCA and MPTA; Spearman method was used to analyze the correlation between TCCA and gender, TCCA and Kellgren-Lawrence(K-L) grade. All 100 patients successfully completed the operation and obtained satisfactory full-length X-rays in standing position. There was no significant difference in TL, MPTA and TCCA between bending group and non bending group(P>0.05). The outilier rate of force line in tibial bending group was 22.5%, and that in non bending group was 6.67%, the difference was statistically significant(P<0.05). The correlation study found that TCCA was strongly correlated with TBA(r=-0.702, P<0.01), weakly correlated with MPTA(r=0.311, P<0.01), and had no correlation with other parameters(P>0.05). In patients with knee osteoarthritis undergoing total knee arthroplasty, tibial bending will lead to poor force line of tibial prosthesis. During operation, attention should be paid to osteotomy of proximal tibial vertical tibial mechanical axis and correct installation of prosthesis to avoid poor alignment of prosthesis.

Repeatability, reproducibility, and agreement of three methods for finding the mechanical axis of the human tibia

Background Identifying the center of the talocrural joint is crucial in defining the tibia’s mechanical axis, which is used in a variety of applications such as a reference for measuring alignment variables following total knee arthroplasty. The objectives of this study were to 1) describe a new method for determining the center of the talocrural joint, 2) determine the repeatability and reproducibility of the new method and two previously described methods for locating the center, 3) determine the limits of agreement between pairs of methods, and 4) determine angular differences in the coronal and sagittal planes between tibial mechanical axes generated by the different methods. Methods The new area centroid method identified the center of the talocrural joint as the centroid of the distal tibia’s articular surface. Previously described methods included the diagonal intersection and biplanar methods. For each method, the medial-lateral, anterior-posterior, and proximal-distal coordinates of the talocrural joint center and angular differences between tibial mechanical axes were determined in thirteen 3D full tibia bone models. Results For the area centroid method, ICC values indicated excellent repeatability (0.97) and reproducibility (0.92). For the biplanar method, ICC values indicated good repeatability (0.86) and fair reproducibility (0.40). For the diagonal intersection method, ICC values indicated moderate repeatability (0.71) and fair reproducibility (0.46). Limits of agreement were tightest between the area centroid and diagonal intersection methods (± 4.1 mm). Angular differences between tibial mechanical axes were limited to 3°. Conclusion The area centroid method locates the anatomic center of the talocrural joint, offers better repeatability and reproducibility than existing methods, and is recommended when identifying the tibial mechanical axis.

Outcomes of Ilizarov Ring Fixator in Infected Nonunion of Tibia

Objective: This study was designed to evaluate the effectiveness of Ilizarov. We aimed to explore the infection rate, bony union, and functional outcomes of Ilizarov fixators.&#x0D; Methodology: This retrospective study was conducted in Orthopedic department of Bolan Medical Complex Hospital Quetta Pakistan from June 2020 to June 2021. In this timeframe total of fifty-five patients of infected nonunion tibia were enrolled for Ilizarov technique treatment. For surgical intervention, patients were placed in a supine position on a radiolucent table. Ilizarov fixator was prepared on the behalf of patient's limb length, infection site, and ankle and knee functional status. We applied assembled Ilizarov fixator at the tibial shaft while keeping in mind that the rings were positioned in on the proximal and distal fragments. The ring was placed parallel to the joints whereas pins were inserted perpendicular to the tibial mechanical axis.&#x0D; Results: A total of 55 patients were recruited for this study. The mean age of the selected participants was 45.65±16.69 years. The overall successful bone results of the ASAMI score were observed as 80% whereas 88% functional outcomes were achieved. In bone results, we observed 28 (50.9%) cases with excellent results, 16 (29%) with good, 7 (12.7%) with fair, and 3 (5.4%) with poor outcomes. On the other hand, 25 (45.4%) cases observed excellent functional results, 25 (45.4%) with good, 4 (7.6%) with fair, and 2 (3.6%) with poor outcomes.&#x0D; Conclusion: Our results show a high success ratio therefore we recommend Ilizarov external fixators for infected nonunion tibial fracture. This method helps to recover limbs without any amputations. However, the discomfort of patients is one of the main problems with this method of treatment.

Proposed Geometrical Tool for Cases of Laterally Adapted Tibial Tubercle during Total Knee Replacement.

The alignment of tibial component in total knee replacement operation must be achieved in three planes to ensure optimum results. In coronal plane, the alignment depends on three anatomical landmarks. These landmarks are tibial tuberosity, leg shin, and midtalar point. In eastern community, people get used to sit cross-legged which causes additional tension in the quadriceps muscle which is attached distally to the tibial tuberosity. This tension causes adaptation of the tuberosity laterally. Tuberosity adaptation causes the three anatomical landmarks being not collinear. In this work, eight cases of lateral adapted tubercle were diagnosed of this condition before the surgery and their X-ray images after the surgery were checked regarding tibial alignment. Tibial alignment has been checked by measuring the medial proximal tibial angle (MPTA) which is the angle between the mechanical tibial axis and the tibial component plateau. MPTAs for the eight cases were (86.9°–93.6°). Three cases had MPTA less than 90° indicating varus alignment and five of them had MPTA more than 90° indicating valgus alignment. A geometrical tool was designed using the DesignSpark Mechanical software as a proposed solution to solve the adaptation problem. The tool can give a method for fixing the tibial component precisely without any varus\\valgus malalignment.

Focal proximal fibular angle: A potential indicator of the tibial mechanical axis in opening-wedge high tibial osteotomy

BackgroundFor opening-wedge high tibial osteotomy, correct alignment is essential for a better prognosis. It is difficult to evaluate the mechanical axis of the lower extremity or tibia using a single fluoroscopic image. This study aimed to discuss the use of focal proximal fibular angle (FPFA), which can be assessed by a single fluoroscopic image, as an intraoperative indicator. MethodsEligible for analyses were 111 consecutively treated patients; for the final analyses 96 patients were included. The preoperative and postoperative medial proximal tibial angle (MPTA) and FPFA were measured. The relationship between these two angles, correction amount, weight-bearing line ratio and patient characteristics were analyzed. ResultsThe preoperative FPFA and MPTA were 96.5 ± 3.8° (mean ± standard deviation, SD) and 84.8 ± 3.0°, while the postoperative FPFA and MPTA were 87.6 ± 4.1° and 94.0 ± 3.5°, respectively. The preoperative and postoperative sums of the MPTA and FPFA were constant. The discrepancy was less than 3° in all knees, less than 2° in 92.7% knees and less than 1° in 68.8% knees. It was not correlated with age, sex, weight-bearing line ratio, or correction amount. ConclusionThe study findings confirmed the constancy of the sum of the MPTA and FPFA. The FPFA can be easily evaluated on a single fluoroscopic image of the knee. Use of the FPFA as guidance may simplify the procedure of opening-wedge high tibial osteotomy and approximately predict the tibial mechanical axis.

Seven phenotypes of varus osteoarthritic knees can be identified in the coronal plane.

Recommendations for resecting distal femur and proximal tibia in mechanical and anatomical alignment techniques are standardized. Kinematic alignment propagates individualizing resection planes. Whether significant variation exists, to warrant departure from standardized resection planes, has not been shown thus far in a large cohort of knees and with a wide range of varus deformity. The null hypothesis of this study was that there was no phenotypic variation in varus osteoarthritic knees. The aim of this paper was to determine whether distinct phenotypes could be identified, based on variations in coronal femoral and tibial morphology, which could aid in surgical planning and categorizing varus knees for future studies. 2129 full-leg weightbearing radiographs were analyzed (1704 preoperative; 425 of contralateral arthritic knee). Measurements made were of HKA (hip-knee-ankle angle), VCA (valgus correction angle), mLDFA (lateral mechanical distal femoral angle), aLDFA (lateral anatomical distal femoral angle), MPTA (medial proximal tibial angle), MNSA (medial neck shaft angle), TAMA (angle between tibial mechanical and anatomical axes), and TPDR (percentage length of tibia proximal to extra-articular deformity). Seven distinct types were identified covering 2021 knees, reducible to 4 broad phenotypes: 11% were Type 1 'Neutral' knees showing values close to reported normal knees (mean VCA 5.5°, mLDFA 87°, aLDFA 81°). 38% were Type 2 'Intra-articular varus' with medial intra-articular bone loss (mean mLDFA 90.9°, MPTA 85.4°, VCA of 5.7°). 41% were Type 3 'Extra-articular varus' with extra-articular deformity (EAD). Type 3a had proximal tibial EAD; Type 3b had tibial diaphyseal EAD; Type 3c had femoral EAD (mean VCA 8.7°, HKA 166°), and severe medial bone loss (mean mLDFA 92°, MPTA 83°). 9% were Type 4 'Valgoid type' with features of valgus knees: Type 4a had medial femoral bowing (mean VCA 2.9°); Type 4b had significant distal femoral valgus (mean mLDFA 85.3°, aLDFA 78.6°). The null hypothesis that there was no phenotypic variation in varus osteoarthritic knees was rejected as considerable variation was found in coronal morphology of femur and tibia. Four broad phenotypic groups could be identified. Plane of the knee joint articular surface was quite variable. This has relevance to planning and performance of corrective osteotomies, unicompartmental and total knee arthroplasty. III, retrospective cohort study.

Custom TKA enables adequate realignment with minimal ligament release and grants satisfactory outcomes in knees that had prior osteotomies or extra-articular fracture sequelae.

To report the early clinical and radiographic outcomes of custom total knee arthroplasty (TKA) in knees that had prior osteotomies and/or extra-articular fracture sequelae. The authors retrospectively analysed a consecutive series of 444 knees that received custom TKA between 2016 and 2019 and identified 41 knees that had prior extra-articular events (osteotomies or fracture sequelae). Patients responded to pre- and post-operative (> 12months) questionnaires, including Knee Society Score (KSS), Oxford Knee Score (OKS), Forgotten Joint Score (FJS) and Knee injury and Osteoarthritis Outcome Score (KOOS). Net improvements were calculated by subtracting pre- from post-operative scores. In addition to a preoperative CT scan, pre- and post-operative long-leg weight-bearing radiographs were obtained, on which the hip-knee-ankle (HKA) angle, femoral mechanical angle (FMA, between femoral mechanical axis and joint line) and tibial mechanical angle (TMA, between tibial mechanical axis and joint line) angles were measured, and alignment was planned within a 'target zone' of FMA and TMA within 85°-95° and HKA angle within 175°-183°. Agreements between preoperative, planned and post-operative angles were calculated using intra-class correlation coefficients (ICC). From the initial 41 knees, 3 had incomplete post-operative data and 1 was revised for painful stiffness due to uncorrected rotational malunion, leaving 37 knees for analysis. Twenty had prior osteotomies (tibia, n = 18, femur, n = 2), 8 had isolated fractures (tibial, n = 3; femoral, n = 5), and 9 had both osteotomies and fractures. Postoperative coronal alignments were 90.4° ± 2.4° for FMA, 89.3° ± 2.6° for TMA and 179.9° ± 3.0° for HKA angle. Agreements between planned and achieved alignments were fair to excellent, and 29 (78%) knees were within the 'target zone'. At a mean follow-up of 15 ± 5months, all clinical scores had improved significantly (p < 0.001). Custom TKA granted satisfactory clinical outcomes and a low complication rate in knees that had prior osteotomies and/or extra-articular fracture sequelae. Using custom implants and strategies for coronal alignment, 29 (78%) of the 37 knees were successfully aligned within the 'target zone', and 35 (95%) of the 41 knees did not require ligament release. IV.

Is Valgus Cut Angle Based on Radiographic Measurements in Total Knee Arthroplasty Really Inaccurate? A Comparison of Two- and Three-Dimensional Measurements.

Radiographs are widely used to measure distal femoral valgus cut angle (VCA) in total knee arthroplasty (TKA), but its accuracy is controversial. This study used three-dimensional (3D) reconstruction models to verify the accuracy of VCA measurements on radiographs, and explore the correlation of VCA with hip-knee-ankle (HKA) angle and lateral femoral bowing angle (FBA). A total of 444 osteoarthritis knees of 444 patients from August 2016 to June 2018 was included retrospectively. On radiographs, two-dimensional VCA (VCA-2D) was measured between the femoral mechanical axis and the distal femoral anatomical axis, and HKA was measured between the femoral mechanical axis and the tibial mechanical axis. On the coronal projection of computed tomography 3D models, the anatomical landmarks used for VCA-3D measurements were the same as those on the radiographs, FBA was measured between the proximal and distal femoral anatomical axis. The distributions of VCA-2D and VCA-3D were evaluated by means and variances. The correlation between HKA and VCA and between FBA and VCA was explored. There was a statistical difference between VCA-2D and VCA-3D (p < 0.001), but the deviation was very small (0.15 ± 0.69 degrees), 83.3% of the deviations were less than 1 degree. VCA would increase both in 2D and 3D with increasing of FBA and HKA varus. There was no statistically significant difference between VCA-2D and VCA-3D in patients with moderate varus knees (0-8 degrees of varus) and mild bowing femurs (FBA <5 degrees). Overall, the deviation caused by using radiography to measure VCA was negligible. VCA measurements using radiographs were accurate in patients with moderate varus knees and mildly bowed femurs. This study reflects level of evidence III.

Tibial Mechanical Axis Is Nonorthogonal to the Floor in Varus Knee Alignment.

BackgroundClassical models of the knee assume the joint line is parallel to the floor and the tibial mechanical axis (TMA) is orthogonal to the floor. Our study characterizes the angle subtended by the TMA and floor during bipedal stance, called the tibial axis orientation angle (TAOA), and tests the assumption that the TMA should be orthogonal to the floor.MethodsWe reviewed the nonoperative knee on full-length, standing radiographs in patients undergoing total knee arthroplasty between 2013 and 2017. Radiographic measurements were obtained for hip-knee-ankle axis, medial proximal tibial angle (MPTA), joint line orientation angle, and TAOA and correlated by regression analysis. The cohort was stratified by hip-knee-ankle axis alignment to determine statistical differences in knee angle values. Demographic data were collected to assess associations with knee angles.ResultsOur cohort included 68 patients, with 56% female and average age of 62.3 years. Varus knees comprised 56% of the cohort, with 7% neutral and 37% valgus. The cohort demonstrated an MPTA of 3.06°, TAOA of 2.67°, and joint line orientation angle of 0.36°. Varus knees had a higher MPTA (4.26°) and TAOA (4.74°) than valgus knees (P < .001). MPTA and TAOA were correlated on regression analysis (r2 = 0.465), and all angles were statistically different between sexes.ConclusionThe angle between the TMA and floor, called TAOA, is not orthogonal in normal knees, contrary to assumptions in classical biomechanics. Knee angles vary significantly between varus and valgus cohorts, and the distinction between these cohorts should be noted when evaluating normal joint line angles.

Comparison of medial distal tibial angle in EOS imaging and weightbearing X-ray

BackgroundThe medial distal tibial angle (MDTA) is used for measurement of ankle alignment. Standard to measure MDTA is weightbearing mortise view. EOS imaging becomes more popular for limb alignment analysis using low-dose radiation. As MDTA might vary in EOS, comparison between both radiographic techniques has been performed. MethodsMDTA was compared between both techniques in 43 cases by defining the mechanical tibial axis in different ways (X-ray low, EOS low, EOS high). For each method MDTA, intra- and interobserver reliability has been compared. ResultsThe correlation between the different methods were measured by ICC (intraclass coefficient) and were ICC 0.86 (X-ray low/EOS low), ICC 0.85 (X-ray low/EOS high) and ICC 0.97 (EOS low/EOS high). Intra- and interobserver reliability were in each case ICC > 0.95. ConclusionICC showed a substantial to excellent agreement between all methods. EOS is appropriate to determine MDTA and can be used for assessment of coronar deformities of the distal tibia.

Relationship between the bony correction angle and mechanical axis change and their differences between closed and open wedge high tibial osteotomy

BackgroundThe purpose of this study was to investigate the relationship between the bony correction angle and mechanical axis change and their differences between closed wedge high tibial osteotomy (CWHTO) and open wedge high tibial osteotomy (OWHTO).MethodsA total of 100 knees of 89 patients who underwent OWHTO (50 knees) or CWHTO (50 knees) between 2011 and 2015 with a clinical follow-up for 1 year and a radiological follow-up for 1 month were investigated in a case control study. Anteroposterior radiographs of the knee and full-length leg were taken in the standing position using digital acquisition. The femorotibial angle (FTA), % mechanical axis deviation (MAD), % anatomical tibial axis deviation (ATAD), % mechanical tibial axis deviation (MTAD), mechanical medial proximal tibial angle (mMPTA), and joint line convergence angle (JLCA) were measured on preoperative and postoperative radiographs using a dedicated software.ResultsCWHTO resulted in a greater variation between the tibial anatomical and mechanical axes than OWHTO (P < 0.05), and a greater soft tissue correction than OWHTO (P < 0.05). However, no significant difference was found between CWHTO and OWHTO in the ratio of MAD change to the correction angle. When the osteotomy was planned with the same bony correction angle, %MAD passed more laterally in OWHTO than in CWHTO (P < 0.05). These results suggested a lesser valgus bony correction ratio due to greater medial shift of the tibial axis and greater valgus compensation of the soft tissue in CWHTO compared to OWHTO.ConclusionsThe ratio of mechanical axis shift to the correction angle differed in preoperative planning, but postoperative alignment was comparable between opening wedge and closed wedge high tibial osteotomy.

Three‐point Method to Guide the Tibial Resection and Component Placing in Total Knee Arthroplasty

ObjectiveTo introduce a three‐point method combining the midpoint of the posterior cruciate ligament (PCL), the midsulcus of the tibial spines, and the midpoint of the anterior cruciate ligament (ACL) to determine appropriate tibial resection and component placing during TKA and to compare this method with Insall's 1/3 method.MethodsA consecutive series of 128 knees that underwent TKA from January 2015 to August 2018 were analyzed. In one group (64 knees), the medial 1/3 of tibial tubercle (the Insall's traditional method) was used for tibial component alignment. In the other group (64 knees), the three‐point line connecting the midpoint of the PCL, the midpoint of the tibial spines, and the midpoint of the ACL was used for tibial component alignment. Both groups used the anterior tibial tendon as the distal reference for tibial resection. The coronal alignment error of the tibial component was determined by the angle between the line parallel to the tibial component platform and the tibial mechanical axis measured on postoperative radiograph. The axial rotation error of the femoral or tibial component was the intersection angle between the transepicondylar axis (TEA) and a line tangent to the posterior edge of the femoral or tibial component measured on CT. The coronal and axial alignment errors were compared between the two groups.ResultsThe average coronal alignment error of the tibial component in the three‐point method group was 0.2° ± 1.4° versus − 0.9° ± 1.8°in the Insall's 1/3 method group (P < 0.001), and the mean absolute value in the three‐point method group reduced by 37.3% compared to Insall's traditional method group. The average axial rotation error of the femoral component was 0.2° ± 1.2° in the three‐point method group versus − 1.1° ± 1.7° in the Insall's 1/3 method group (P < 0.001), and the mean absolute value in three‐point method group decreased by 43.9% compared to Insall's traditional method group. The average axial rotation error of the tibial component was 0.4° ± 1.4° versus − 1.4° ± 1.8° in the Insall's 1/3 method group (P < 0.001), and the mean absolute value in the three‐point method group reduced by 35.5% compared to the Insall's traditional method group. The rates of rotation outliers were significantly lower in the three‐point method group (P < 0.05).ConclusionThe line connecting the midpoint of the PCL, the midsulcus of the tibial spines, and the midpoint of the ACL could be used as the reference for the tibial resection and component placing. This method appears to be more accurate than Insall's 1/3 method. The results of this study provide a candidate method for component orientation with little error.

Variations in medial and lateral slope and medial proximal tibial angle.

The primary objective of this study was to quantify the variations of the medial posterior tibial slope (MPTS) and the lateral posterior tibial slope (LPTS), as well as of the medial proximal tibial angle (MPTA), and to determine the fraction of patients for which standard techniques including different alignment techniques would result in alteration of the patient's individual posterior tibial slope (PTS) and MPTA. Furthermore, it was of interest if a positive correlation between PTS and MPTA or between medial and lateral slope exists. A retrospective study was performed on CT-scans of 234 consecutively selected European patients undergoing individual total knee replacement. All measurements were done on three-dimensional CAD models, which were generated on the basis of individual CT-scans, including the hip, knee, and ankle center. Measurements included the medial and lateral PTS and the MPTA. PTS was measured as the angle between the patient's articular surface and a plane perpendicular to the mechanical axis of the tibia in the sagittal plane. MPTA was defined as the angle between the tibial mechanical axis and the proximal articular surface of the tibia in the coronal plane. Analysis revealed a wide variation of the MPTS, LPTS, and MPTA among the patients. MPTS and LPTS varied significantly both interindividually and intraindividually. The range of PTS was up to 20° for MPTS (from - 4.3° to 16.8°) and for LPTS (from - 2.9 to 17.2°). The mean intraindividual difference between MPTS and LPTS in the same knee was 2.6° (SD 2.0) with a maximum of 9.5°. MPTA ranged from 79.8 to 92.1° with a mean of 86.6° (SD ± 2.4). Statistical analysis revealed a weak positive correlation between MPTA and MPTS. The study demonstrates a huge interindividual variability in PTS and MPTA as well as significant intraindividual differences in MPTS and LPTS. Therefore, the question arises, whether the use of standard techniques, including fixed PTSs and MPTAs, is sufficient to address every single patient's individual anatomy. III.

Reliability of EOS compared to conventional radiographs for evaluation of lower extremity deformity in adult patients.

The purpose of this study was to compare reliability of lower extremity imaging measurements using EOS and conventional X-ray (CR) of adult patients with mechanical axis malalignment. Ten patients (20 lower limbs) of mean age of 31.6years (range 21-39) with post-traumatic deformities who presented for evaluation of osteotomies and/or ligament and cartilage reconstructions were prospectively enrolled. Two independent observers performed full-length anterior-posterior (AP) measurements 2weeks apart on both CXR and two-dimensional (2D) EOS images. Measurements included weight-bearing axis (WBA), varus/valgus angle (V/V), femoral length (FL), tibial length (TL), femoral mechanical axis (FMA), tibial mechanical axis (TMA), and total limb length (TLL). Reliability was determined with random effects modeling of intraclass correlation coefficients (ICC) set to consistency. Three statistical operations were performed to compare interrater validity in CXR and EOS: students' two-sample t test, paired two-sample t test, and Pearson's correlative r-statistical agreement. There was a statistically significant difference for V/V, FL, and TLL (all p< 0.01) between CXR and EOS. A relatively large proportion of the population consistently had larger V/V measures for EOS compared to CXR. In contrast, the FL and TLL measures were consistently larger for CXR compared to EOS. The differences between CXR and EOS measurements were statistically significant, though the small differences in values were not clinically meaningful. Agreement of all measures remained high (r= 0.84-0.99). Using 2D EOS for lower extremity measurements is reproducible, reliable, and comparable to the gold standard, standing long leg radiographs.