Transepicondylar Axis Research Articles

Effects of Femoral Component Design on the Deepest Point Position of the Trochlear Grove in Kinematically Aligned Total Knee Arthroplasty: A Comparison of Four Prothesis Designs.

The aim of the study is to explore and compare the differences in trochlear shape and knee anatomy between four types of prostheses and preoperative native knee matched with preoperative computed tomography (CT). Thirty patients were scheduled for primary kinematically aligned total knee arthroplasty (TKA) for varus knee osteoarthritis at our hospital and the region between their pelvis to ankle joint was simulated using a CT-based three-dimensional planning software. The axial plane containing the transepicondylar axis was set as Slice A, and the 10-mm distal plane from Slice A was set as Slice B. The distances to the deepest trochlear groove between the native knee and each prosthesis and the medial and lateral facet heights were compared among the four groups. The deepest femoral trochlear groove of the prostheses was located 1.6 to 3.0 mm more medial than that of the native knee, and in the Persona group, it was significantly more medial than in the e-motion or Triathlon groups on both Slices A and B. The native knee and the medial and lateral facet heights of the four prostheses on both Slices A and B were significantly lower than those of preoperative native knees when femoral prostheses were set in the kinematically aligned (KA)-TKA position. The deepest point of the trochlear groove of the Persona group was the most medial among the four prostheses studied, and the deepest points differed depending on the prosthesis design in KA-TKA. Thus, surgeons should carefully select the type of prostheses used in KA-TKA.

Sagittal femoral condylar shape varies along a continuum from spherical to ovoid: a systematic review and meta-analysis.

Considerable anatomic variations of sagittal femoral condylar shape have been reported, with a continuum between spherical (or single-radius) and ovoid (or multi-radius) condyles. The purpose of this systematic review and meta-analysis was to critically appraise and synthesise the available literature on the sagittal femoral profile. The hypothesis was that studies would reveal considerable variability among individuals, but also in their methodology to quantify sagittal profiles. This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. On 10 September 2021 two authors searched for Level I to IV studies that reported on the sagittal curvature of the medial and/or lateral femoral condyles using the MEDLINE®, EMBASE® and Cochrane Library. Results were summarised by tabulating means, standard deviations and/or ranges for the reported radii-of-curvature, or ellipsoidal semi-major and semi-minor lengths of the condyles. To quantify sagittal 'ovoidicity' and asymmetry, results were stratified according to coordinate reference frame (posterior condylar axis (PCA), clinical and surgical transepicondylar axis (cTEA and sTEA), unified sagittal plane (USP), or unclear) and summarised in forest plots as standardised mean differences (SMD). Thirty-eight articles wereeligible for full text extraction, quantifyingsagittal radii-of-curvature by best-fit circles (BFC), ellipsoids, polynomials, spherical or cylindrical fitting. Studies with clear definition of the measurement plane revealed that both condyles were generally ovoid, with considerably greater 'ovoidicity' at the medial condyle (SMD, 4.09) versus the lateral condyle (SMD, 3.33). In addition, distal condylar radii were greater medially when measured normal to the TEA (cTEA: SMD, 0.81; sTEA: SMD, 0.79), but greater laterally when measured in a USP (SMD, -0.83). Posterior condylar radii were greater laterally when measured in a USP (SMD, -0.60). Studies reported considerable variability of sagittal femoral condylar radii-of-curvature, which arenot incremental, but rathera continuum that ranges from spherical to ovoid. Although this variation could be accommodated by single-, dual- and multi-radii femoral components, a surgeon typically uses only one or two TKA designs. Hence, there is a risk of mismatch between the native and prosthetic sagittal profile that could result in mid-flexion ligament imbalance unless other parameters are changed. These findings support the drive towards patient-specific implants to potentially achieve accurate sagittal bone-implant fit through implant customisation. IV.

Tibial Tubercle to Trochlear Groove Distance Measured by Posterior Condylar Reference Line on MRI Can Over-Evaluate Lateralization Deformity of Tibial Tubercle in Patients with Recurrent Patellar Dislocation.

Background: The tibial tubercle to trochlear groove (TT-TG) distance is currently considered as an indication for tibial tubercle osteotomy. While the influence of femoral condylar morphology on such measurement remains unclear. Methods: A total of 86 patients with patellar dislocation (PD) and 86 healthy individuals were enrolled. Femoral condylar morphology and the TT-TG distance measured by anatomical transepicondylar axis (TT-TGa), by surgical transepicondylar axis (TT-TGs), and by posterior condylar reference line (TT-TGp) were assessed by MRI. Unpaired t-test, Spearman, and Pearson correlation analysis were conducted. We determined the pathological value of the parameters and established a binary regression model. Results: The interclass correlation coefficients of all the TT-TG distances were greater than 0.75 in all types of trochlear dysplasia. The lateral/posterior femoral condyle was shorter and the medial/posterior condyle was longer in the study group (28.5 ± 3.3 and 35.2 ± 2.8, respectively) than in the control group (30.9 ± 2.7 and 33.5 ± 2.3, respectively). In the study group, the TT-TGp distance was greater than TT-TGs and TT-TGa distance (p < 0.001). The pathological value of the TT-TG distance was 13.0 mm. Each TT-TG distance revealed a significant OR with regard to PD. Conclusion: The TT-TGa, TT-TGs, and TT-TGp distance can be reliably measured by MRI even in patients with trochlear dysplasia. While the TT-TGp distance may overestimate the lateralization deformity of the tibial tubercle. Posterior femoral condylar dysplasia may be a reason for such overestimating. These findings have not been correlated to clinical outcomes and further studies are required.

Open wedge high tibial osteotomy does not decrease patellar height relative to femur: A three-dimensional computer model analysis

BackgroundPatellar height, which decreases after open wedge high tibial osteotomy (OWHTO), has conventionally been assessed by tibial references using lateral radiographs of the knee; however, changes in the proximal tibia shape after OWHTO may affect this method. We aimed to evaluate the changes in patellar height position relative to the transepicondylar axis of the femur after OWHTO using in vivo three-dimensional (3D) computer models. MethodsFourteen patients who underwent 3D magnetic resonance imaging (MRI) at 30° and 50° knee flexion before OWHTO and after hardware removal were included. 3D computer models of the knee were created from the MRI scans and superimposed over the images taken in each position using voxel-based registration. For patellar height evaluation, a patellar reference point was established at each flexion angle and the femoral condylar planes (FCP) were set, including the transepicondylar axis. The patellar center angle was defined as the angle between an FCP that included the top of the intercondylar notch and an FCP that included the patellar reference point. The patellar center angle was evaluated at 30° and 50° knee flexion before and after OWHTO. ResultsThe patellar center angle at 30° and 50° knee flexion did not significantly decrease after OWHTO, whereas the Caton-Deschamps index and Blackburne-Peel index based on tibia-referenced measurements significantly decreased postoperatively. ConclusionPatellar height position relative to the femur in the 3D computer model did not decrease after OWHTO, whereas tibia-referenced conventional radiographic measurements significantly decreased. When evaluating patellar height, characteristics of each parameter should be considered.

Cartilage assessment using preoperative planning MRI for femoral component rotational alignment

BackgroundSurgical planning of posterior referencing total knee arthroplasty (TKA) using computed tomography (CT) might lead to over-rotation of the femoral component because CT could not detect cartilage thickness of the posterior femoral condyle. The purpose of this study was to examine the rotational alignment difference of the femoral component between magnetic resonance imaging (MRI) and CT. MethodsFor elderly varus osteoarthritic patients, 66 varus osteoarthritic knee patients that underwent primary TKA were selected. Twenty-seven young patients who underwent primary anterior cruciate ligament reconstruction were selected as control. After the transepicondylar axis (CEA), the surgical epicondylar axis (SEA) and the posterior femoral condylar line (PCL) were drawn on CT and on MRI at the same angles as CT. Then, the practical PCL was drawn on MRI considering the cartilage thickness (the cartilage PCL). The angle between the SEA and the cartilage PCL (the cartilage posterior condylar angle (PCA)) was measured as preoperative planning. To investigate the accuracy of preoperative MRI measurement, the cartilage thickness on posterior femoral condyles was directly measured during TKA. ResultsThe cartilage PCA for varus osteoarthritic patients averaged 1.3 ± 1.3°. The cartilage PCA was 1.8 ± 1.0° significantly smaller than the bone PCA (the PCA measured on CT). Meanwhile, the cartilage PCA was 0.2 ± 0.4° significantly larger than the bone PCA in young people. The preoperative angle measurement on MRI strongly correlated with the direct measurement of cartilage thickness during TKA. ConclusionThere was 1.8° of divergence between MRI and CT in varus osteoarthritic patients due to cartilage degeneration of the medial femoral condyle. Cartilage assessment using MRI was useful for femoral component rotational alignment.

High femoral anteversion in osteoarthritic knees, particularly for severe valgus deformity

ObjectiveIncreased femoral anteversion (FA) has been correlated with less varus deformities in osteoarthritic (OA) knees, but the relationship between FA and the degree of valgus deformity in osteoarthritic (OA) knees is still largely unknown. We aimed to thoroughly analyze the distribution of FA in relation to varus or valgus deformities of the lower extremity in OA knees, and to further clarify the relationship between FA and trochlear morphology.Methods235 lower extremities with OA knees were divided into five groups according to the mechanical tibiofemoral angle: excessive valgus (< − 10°), moderate valgus (− 10° to − 3°), neutral (− 3° to 3°), moderate varus (3° to 10°), and excessive varus (> 10°). FA (measured using the posterior condylar axis [pFA] and the transepicondylar axis [tFA]) was measured, and the relationships of FA to the mechanical tibiofemoral angle and femoral trochlear morphology were identified.ResultsExcessive FA (pFA ≥ 20°) was observed in 30.2% of all patients and in 58.8% of patients in the excessive valgus group. pFA showed a strong correlation with mechanical tibiofemoral angle (p = 0.018). Both the pFA and the tFA of patients in the excessive valgus group were greater than those in other four groups (all p ≤ 0.037). There were significant correlations between tFA and trochlear parameters, including the sulcus angle (SA), lateral trochlear slope (LTS), and medial trochlear slope (MTS) (all p ≤ 0.028).ConclusionHigh FA is prevalent, particularly in severe valgus knees, and FA is significantly related to the femoral trochlear morphology in OA knees. With the aim of improving the patellofemoral prognosis and complications, high FA should be considered during total knee arthroplasty.

Failure modes in malrotated total knee replacement.

Achieving normal rotational alignment of both components in total knee arthroplasty (TKA) is essential for improved knee survivorship and function. However, malrotation is a known complication resulting in higher revision rates. Understanding malrotation of the components and its concomitant clinical and functional outcomes are important for early diagnosis and management. The purpose of this study was to evaluate the effect of malrotation on clinical outcomes and failure modes in both single and combined rotational malalignment. From our hospital database of 364 revisions, a cohort of 76 knees with patellar maltracking, stiffness, reduced range of motion and early aseptic failure were reviewed and investigated for component malrotation using computed tomography following Berger protocol. CT findings confirmed component malrotation in 70 of these patients. Investigations included (1) measurement of femoral component malrotation using surgical transepicondylar axis, (2) measurement of tibial component malrotation using anteroposterior axis and (3) measurement of combined component rotational errors. The correlation of CT analysis and clinical outcomes after primary TKA revealed association of patellar maltracking with femoral internal rotation, pain and instability with tibial internal rotation and knee stiffness in patients with combined component malrotation as the commonest mode of presentation. Our study showed that patients with isolated femoral, tibial and combined malrotation presented at a mean period of 3.4 ± 1.34, 1.7 ± 0.8 and 2.3 ± 0.69years, respectively, after the index surgery. Post-revision, the mean Knee Society Score and Oxford Knee Score improved from 29.1 to 78.7, and 10.5 to 32.8, respectively, and the mean range of motion improved from 74.9 ± 24.8 to 97.1 ± 12.7 degrees at a mean follow-up of 42months. Early detection of malrotation in TKA and its management with revision of both components can lead to better clinical and functional outcomes. III.

Metal Artifact Reduction Dual-Energy CT as an Accurate and Reliable Method for Measuring Total Knee Arthroplasty Femoral Component Rotation Compared to Conventional CT.

This article determines the accuracy and reliability of dual-energy computed tomography (DECT) with metal artifact reduction (MAR) in the evaluation of femoral component rotation after total knee arthroplasty (TKA), in comparison with conventional CT images. A total of 49 patients (mean age, 69 years; 42 women) who underwent TKA between January 2019 and March 2020 were retrospectively enrolled. Femoral component rotation, including the anatomic and surgical transepicondylar axes, was evaluated with preoperative conventional CT and postoperative conventional CT and DECT with MAR. Surgical femoral component rotation was also assessed as a reference standard. Accuracy was assessed using paired t-test, and inter- and intraobserver reliability using intraclass correlation coefficients (ICCs) based on postoperative conventional CT and DECT with MAR. Clinical outcomes were evaluated using the Knee Society objective and functional scores. Accuracy of femoral component rotation was not significantly different from that of surgical rotation with both conventional CT and DECT with MAR. However, inter- and intraobserver reliability were better for DECT with MAR (ICC: 0.953-0.966) than for conventional CT (ICC: 0.641-0.749). The Knee Society objective and functional scores improved 1 year postoperatively. CONCLUSION: DECT with MAR showed accurate and more reliable results than did conventional CT in the evaluation of femoral component rotation after TKA.

Accuracy of patellar tendon at the attachment as anatomic landmark for rotational alignment of tibial component

To investigate the accuracy of the modified Akagi line which referenced the patellar tendon at the attachment and the geometrical center point of the tibial osteotomy surface for tibial rotational alignment. Between July 2021 and December 2021, 72 patients who underwent three-dimension (3D) CT for varus osteoarthritis knees were enrolled. Among 72 patients, 18 were male and 54 were female with a mean age of 64.9 years (range, 47-84 years). The preoperative hip-knee-ankle angle ranged from 0° to 26°, with a mean of 9.3°. CT images were imported into Mimics 21.0 medical image control system to establish 3D models of the knees. The prominent point of lateral epicondyle and the medial epicondylar sulcus were identified in femoral 3D models to construct the surgical transepicondylar axis and the vertical line of its projection [anteroposterior (AP) axis]. In tibial 3D models, the patellar tendon at the attachment was used as anatomical landmarks to construct rotational alignment for tibial component, including the line connecting the medial border of the patellar tendon at the attachment (C) and the middle (O) of the posterior cruciate ligament insertion (Akagi line), the line connecting the point C and the geometric center (GC) of the tibial osteotomy plane [medial border axis of the patellar tendon (MBPT)], the line connecting the medial sixth point of the patellar tendon at the attachment and the point GC [medial sixth axis of the patellar tendon (MSPT)], the line connecting the medial third point of the patellar tendon at the attachment and point O [medial third axis of the patellar tendon 1 (MTPT1)], and the line connecting the medial third point of the patellar tendon at the attachment and point GC [medial third axis of the patellar tendon 2 (MTPT2)]. The angles between the five reference axes and the AP axis were measured, and the distribution of the rotational mismatch angles with the AP axis was counted (≤3°, 3°-5°, 5°-10°, and >10°). Relative to the AP axis, the Akagi line and MBPT were internally rotated (1.6±5.9)° and (2.4±6.9)°, respectively, while MSPT, MTPT1, and MTPT2 were externally rotated (5.4±6.6)°, (7.0±5.8)°, and (11.9±6.6)°, respectively. There were significant differences in the rotational mismatch angle and its distribution between reference axes and the AP axis ( F=68.937, P<0.001; χ 2=248.144, P<0.001). The difference between Akagi line and MBPT showed no significant difference ( P=0.067), and the differences between Akagi line and MSPT, MTPT1, MTPT2 were significant ( P<0.012 5). When the position of the posterior cruciate ligament insertion can not be accurately identified on total knee arthroplasty, MBPT can be used as the modified Akagi line in reference to the geometrical center point of the tibial osteotomy surface to construct a reliable rotational alignment of the tibial component.

Femoral anteversion measured by the surgical transepicondylar axis is a reliable parameter for evaluating femoral rotational deformities in patients with patellar dislocation.

To verify whether femoral anteversion measured by the surgical transepicondylar axis (S-FA) is a reliable parameter for evaluating femoral rotational deformities and to provide an indication for derotational distal femoral osteotomy (DDFO) in patients with patellar dislocation. Ninety patients with recurrent patellar dislocation and 90 healthy individuals were enrolled. The S-FA, the femoral anteversion measured by posterior condylar reference line (P-FA), the length of posterior femoral condyles, and the posterior condylar angle (PCA) were assessed by CT images. The unpaired t test and Pearson correlation analysis were conducted. Receiver operating characteristic curves and the area under the curve (AUC) were used to evaluate the diagnostic capacity of the parameters. The pathological value of the measurements was determined, and a binary regression model was established. The S-FA and P-FA were greater in the study group (14.2 ± 7.7° and 19.7 ± 7.3°, respectively) than in the control group (7.2 ± 8.0° and 12.2 ± 8.2°, respectively) (P < 0.001). The lateral/posterior condyle was shorter in patients with patellar dislocation (21.2 ± 2.5mm) than in healthy individuals (23.5 ± 2.7mm) (P = 0.001). The P-FA was correlated with PCA in the study group (P < 0.001). The S-FA and P-FA had AUCs of 0.734 and 0.767 for patellar dislocation, respectively. The pathological values of the S-FA and P-FA were 20.4° and 25.8°, respectively. The S-FA revealed a significant OR of 10.47 (P = 0.014) for patellar dislocation. The S-FA is a reliable parameter for identifying femoral rotational deformities in patients with patellar dislocation. DDFO is recommended when a pathological S-FA (> 20.4°) is presented. Retrospective cohort study (diagnostic), level II.

A novel anteroposterior axis of the tibia for total knee arthroplasty: An upright weight-bearing computed tomography analysis

BackgroundThe traditional anteroposterior (AP) axis (i.e., Akagi’s line) has been widely used as the tibial component AP axis during total knee arthroplasty (TKA). However, this AP axis has been defined based on computed tomography (CT) in a non-weight-bearing supine position. In this study, AP axes of the tibial plateau from upright CT in weight-bearing and non-weight-bearing positions were determined and compared. MethodsThis study included 43 knees from 23 healthy volunteers. CT images were obtained in weight-bearing and non-weight-bearing standing positions using a 320-detector row upright CT scanner. The line perpendicular to surgical transepicondylar axis projected onto the tibia plateau was determined as the AP axis in upright weight-bearing and non-weight-bearing conditions. Angular differences between these two conditions were measured. ResultsThe upright weight-bearing AP axis was positioned in a mean of 7.4 ± 4.3° of internal rotation relative to the traditional AP axis. Distance between the traditional and upright weight-bearing AP axis was 2.9 ± 1.6 mm at the edge of the tibial plateau. The upright non-weight-bearing AP axis was positioned in a mean of 3.5 ± 4.1° of internal rotation relative to the traditional AP axis. Mean angular difference between weight-bearing and non-weight-bearing conditions was 3.9 ± 4.1°. ConclusionsThe upright weight-bearing AP axis was positioned in 7.4° of internal rotation relative to the traditional AP axis, showing one-seventh of the tibial tuberosity away from the medial border of the tibial tubercle, which represents a practical landmark for the tibial component AP axis during TKA.

Osseous Morphological Differences in Knee Osteoarthritis.

Improved understanding of the morphological characteristics of knees with osteoarthritis (OA) and various deformities can enable personalized implant positioning and balancing in total knee arthroplasty in an effort to continue improving clinical outcomes and optimizing procedural value. Therefore, the purpose of this study was to outline morphological differences in the medial and lateral distal femur and proximal tibia associated with varus and valgus deformities in knee OA. A large computed tomography (CT) database was used to identify 1,158 knees, which were divided into normal and osteoarthritic groups; the latter was further divided on the basis of deformity into neutral, varus, and valgus subgroups. Morphological measurements included the non-weight-bearing hip-knee-ankle angle (nwHKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), rotation of the posterior condylar axis (PCA) relative to the surgical transepicondylar axis (sTEA), ratio of medial to lateral posterior condylar offset, ratio of medial to lateral condylar radius, medial posterior slope (MPS), lateral posterior slope (LPS), medial coronal slope (MCS), and lateral coronal slope (LCS). Compared with the normal group, the OA group was in overall varus (nwHKA, -2.2° ± 5.0° compared with -0.2° ± 2.4°) and had a significantly smaller MPS (8.4° ± 4.0° compared with 9.2° ± 4.0°), larger LPS (9.2° ± 3.6° compared with 7.2° ± 3.3°), and smaller MCS (82.1° ± 4.3° compared with 83.9° ± 3.3°). Differences among the OA subgroups were also observed for the MCS and LCS. Compared with the normal group, the sTEA of the OA group was less externally rotated relative to the PCA (0.3° ± 1.5° compared with 1.2° ± 1.9°), and both the condylar offset ratio (1.01 ± 0.06 compared with 1.04 ± 0.07) and the condylar radius ratio (0.98 ± 0.07 compared with 1.03 ± 0.07) were smaller. Only the condylar radius ratio showed differences among the OA subgroups, with valgus deformity associated with a larger ratio. An analysis of CT scans of 965 healthy and 193 osteoarthritic knees revealed significant differences in PCA, condylar offset, and condylar radius as well as tibial slope in both the sagittal and coronal planes. There is a strong need to evolve toward a more personalized treatment for osteoarthritic knees that utilizes implants and technology to help tailor total knee arthroplasty on the basis of the patient's morphologic characteristics.

Comparison of Anterior-Posterior Axis Versus Transepicondylar Axis in Patients Undergoing Simultaneous Bilateral Total Knee Arthroplasty: One Technique per Knee

BackgroundIn primary total knee arthroplasty (TKA), the preferred reference line for setting femoral component rotation is debatable. This study compared the anterior-posterior axis line (APAL) versus the transepicondylar axis line (TEAL) in patients undergoing simultaneous bilateral TKA using a measured resection technique where one reference line was randomized to each knee. MethodsThis prospective study compared the two reference lines using posterior knee referencing with a cemented posterior stabilized knee. The study included 32 patients with osteoarthritis with both knees having similar varus knee deformities. All patients had the same surgical procedure with the only change being the selected femoral rotation axis line. Patients were followed up for a minimum of two years. ResultsThere was no significant difference in any of the measured radiographic, operative, and clinical parameters, except for a postoperative radiographic limb alignment (APAL 179.7° vs TEAL 180.1° P = .04). The mean femoral external rotation relative to the posterior condylar axis line (PCAL) was 3.0 degrees (0-7 degrees) using the APAL and 3.3 degrees (2-7 degrees) using the TEAL (P = .46). Two-year knee flexion and revised Oxford Knee Scores showed no difference. Seventy-five percent of patients stated no preference for either knee technique. ConclusionWhen using a measured resection, a posterior referencing technique, we found no difference in knee function and scores when setting femoral component rotation using the APAL versus TEAL. Level of Evidence2, Randomized prospective study.

Knee joint line related to bony landmarks of the knee: a radiologic study in a Thai population

BackgroundDuring revision total knee arthroplasty (TKA), knee joint line restoration may be difficult due to bone loss or structural changes. Although bony landmarks are consistent and can be used as references, there are limited data in Asian patients. We studied the knee joint line related to bony landmarks of the knee in a Thai population.Materials and methodsMagnetic resonance imaging (MRI) of 140 healthy knees of Thai patients (70 males, 70 females) were investigated. In all knees, a perpendicular line from knee joint line to the medial epicondyle (distance A) and the lateral epicondyle (distance B) in the coronal plane were measured. In the sagittal plane, a perpendicular line from the knee joint line to the fibular head (distance C), the tibial tubercle (distance D), and the inferior patellar pole (distance E) were measured. The femoral transepicondylar width (FW) was measured along the transepicondylar axis. The ratios of distances A, B, C, D, and E related to FW were evaluated (epicondylar ratio).ResultsThe mean and standard deviation (SD) of distances A, B, C, D, E, and FW were 27.1 ± 2.7 mm, 21.7 ± 2.5 mm, 12.6 ± 3 mm, 21.3 ± 3.6 mm, 7.6 ± 4.8 mm, and 76.7 ± 3.99, respectively. There was wide variation of measured values, with statistically significant differences between genders in distances A, B, C, and FW. The mean and SD of epicondylar ratios A/FW, B/FW, C/FW, D/FW, and E/FW were 0.35 ± 0.02, 0.29 ± 0.02, 0.16 ± 0.05, 0.28 ± 0.04, and 0.09 ± 0.04, respectively. All epicondylar ratios demonstrated less variation than all measured distances, with statistical differences between genders in the A/FW and D/FW ratios. However, the B/FW ratio had the highest consistent mean value. In addition, it had narrower SD than the rest (0.29 ± 0.02; range, 0.22–0.33).ConclusionsIn Thai knees, the measured distances from bony landmarks to the knee joint line had higher variation than the epicondylar ratio. Among all studied epicondylar ratios, the ratio between lateral epicondyle to joint line distance (distance B)/FW demonstrated the narrowest range of mean and SD values; therefore, this could be the most reliable landmark for intraoperative knee joint line verification by multiplying the FW of the patient by 0.29 to get distance B in that patient.

Inaccuracy of the intramedullary femoral guide: traditional instrumentation lacks precision and accuracy.

The purpose of the study was to utilize a large-scale biomorphometric computer tomography (CT) database to determine the desirable starting point and angle for placement of the femoral intramedullary rod in the sagittal plane. A CT-based modeling and analytics system (SOMA, Stryker, Mahwah, NJ) was used to evaluate 1029 entire-femur CT scans. From this, 19,464 simulations were run to test whether a 20cm intramedullary rod, with a radius of 4mm, would successfully pass through the femoral canal before contacting cortical bone. First, modelling included varying angles from 0-6 degrees in the sagittal plane, at 1-degree intervals. Next, the start point was adjusted with an assumed 3 degrees of induced flexion in comparison to the mechanical axis. A total of 5012 simulations were able to place the femoral intramedullary rod 20cm into the canal. The angle of the rod that created the highest proportion of successful jig placement was at a 3-degree angle of induced flexion to the orthogonal plane of the transepicondylar axis (TEA), with 33.7% successful jig placements. The starting point for the greatest proportion of successful guide placements was 48.5% along the distance between the sTEA, slightly closer to the lateral side. In the AP plane, the average distance to the ideal start point was 12.1mm anterior to the PCL. By examining over a thousand femoral CT scans, an angle of 3 degrees of induced flexion was identified in the sagittal plane with the highest proportion of successful placement of an intramedullary rod before cortical contact. It is important to note the high rate of failure in completely inserting the 20mm rod. This is a prospective computer based model.

Reliability of the Posterior Condylar Axis as an Alternative Reference for Femoral Rotation in Japanese Patients with Varus Knee Osteoarthritis Undergoing Total Knee Arthroplasty

Background: This study aimed to assess the reliability of the posterior condylar axis (PCA), the most widely used alternative reference for the surgical transepicondylar axis (sTEA), as a reference for appropriate femoral rotational alignment in total knee arthroplasty (TKA) by comparing variances with other alternative reference axes. Methods: A total of 305 knees in 233 Japanese patients who underwent TKA due to varus knee osteoarthritis were assessed in this study. Variances and relationships between alternative references were determined. Angles of alternative reference axes relative to the sTEA in the axial plane were measured using computer software based on computed tomography. Results: The PCA line was 3.0°±1.8° (range, -2.1° to 8.8°) internally rotated relative to the sTEA. No significant differences were observed in the PCA angle relative to the sTEA angle between males and females. The variance with respect to the sTEA was significantly smaller in the order of anatomical transepicondylar axis (aTEA), PCA, and antero-posterior axis (APA). The variance of the APA and that of the femoral anterior tangent line (FAT) did not significantly differ, while the variance of the FAT was significantly smaller than that of the trochlear anterior line (TAL). The proportion of outliers for PCA (&gt;3° away from the average value) was 9.8%. The PCA was weakly correlated with the aTEA, APA, FAT, and TAL. Conclusions: In terms of variance with respect to the sTEA, the PCA was second to aTEA in reliability as an alternative reference axis, and was on average 3.0°±1.8° internally rotated relative to the sTEA. Our findings suggest that the PCA is a reliable and reproducibly identifiable alternative axis for accurately determining femoral rotational alignment in TKA.

Self-aligned Technique for Tibial Component Placement in Total Knee Arthroplasty Lessening Rotational Malalignment in Measured Resection and Gap-Balancing Techniques.

Femorotibial rotational mismatch can occur when there is a rotational malalignment in either the tibial or femoral component. Self-aligned technique was proposed for orienting the tibial component in relation to the femoral prosthesis to reduce rotational malalignment between components. Therefore, we aimed to compare the rotational angle of the femoral and tibial components, as well as the femorotibial rotational mismatch, between the measured resection (MR) and gap-balancing (GB) techniques when combined with a self-aligned technique. We conducted a nonrandomized, experimental study with 50 patients in each group. The femoral rotation was set to 3° external rotation relative to the posterior condylar axis in the MR group, whereas the femur was resected to obtain an optimal rectangular flexion gap in the GB group. The self-aligned method was used to set the tibial rotation in both groups. Femoral and tibial rotational alignments were evaluated compared to a surgical transepicondylar axis of the femur using computed tomography. Rotational mismatch was defined as a difference between the femoral and tibial rotational alignments. A positive value indicated that the component was externally rotated relative to the reference line. The femoral component of the GB group was more externally rotated than that of the MR group (1.52° ± 1.31° vs 0.28° ± 1.16°, p < 0.001). However, the tibial rotational angle was not statistically significantly different between the MR and GB groups (1.28° ± 3.17° vs. 1.86° ± 2.81°, p = 0.220), and the rotational mismatch was 1.00° ± 3.28° and 0.34° ± 2.71°, respectively (p = 0.306). Although the femoral component of the GB group had a greater degree of external rotation than that of the MR group, the use of a self-aligned technique for tibial component placement resulted in no significant difference in tibial rotational alignment or rotational mismatch. This technique helps align the tibial component with the femoral component and lessen the degree of rotational malalignment in both the MR and GB techniques.

Appropriate determination of the surgical transepicondylar axis can be achieved following distal femur resection in navigation-assisted total knee arthroplasty

BackgroundMany surgeons have determined the surgical transepicondylar axis (sTEA) after distal femur resection in total knee arthroplasty (TKA). However, in most navigation systems, the registration of the sTEA precedes the distal femur resection. This sequential difference can influence the accuracy of intraoperative determination for sTEA when considering the proximal location of the anatomical references for sTEA and the arthritic environment. We compared the accuracy and precision in determinations of the sTEA between before and after distal femur resection during navigation-assisted TKA.MethodsNinety TKAs with Attune posterior-stabilized prostheses were performed under imageless navigation. The sTEA was registered before distal femur resection, then reassessed and adjusted after distal resection. The femoral component was implanted finally according to the sTEA determined after distal femur resection. Computed tomography (CT) was performed postoperatively to analyze the true sTEA (the line connecting the tip of the lateral femoral epicondyle to the lowest point of the medial femoral epicondylar sulcus on axial CT images) and femoral component rotation (FCR) axis. The FCR angle after distal femur resection (FCRA-aR) was defined as the angle between the FCR axis and true sTEA on CT images. The FCR angle before distal resection (FCRA-bR) could be presumed to be the value of FCRA-aR minus the difference between the intraoperatively determined sTEAs before and after distal resection as indicated by the navigation system. It was considered that the FCRA-bR or FCRA-aR represented the differences between the sTEA determined before or after distal femur resection and the true sTEA, respectively.ResultsThe FCRA-bR was −1.3 ± 2.4° and FCRA-aR was 0.3 ± 1.7° (p < 0.001). The range of FCRA-bR was from −6.6° to 4.1° and that of FCRA-aR was from −2.7° to 3.3°. The proportion of appropriate FCRA (≤ ±3°) was significantly higher after distal femur resection than that before resection (91.1% versus 70%; p < 0.001).ConclusionsThe FCR was more appropriate when the sTEA was determined after distal femur resection than before resection in navigation-assisted TKA. The reassessment and adjusted registration of sTEA after distal femur resection could improve the rotational alignment of the femoral component in navigation-assisted TKA.Level of evidenceIV.

The bicipital groove as a landmark for humeral version reference during shoulder arthroplasty: a computed tomography study of normal humeral rotation.

Accurate reproduction of humeral version is important in shoulder arthroplasty. Traditional referencing relative to the transepicondylar axis (TEA) is prone to error as it is absent on preoperative imaging and inaccurately reproduced intraoperatively. The bicipital groove is present on preoperative imaging and in the operative field and thus may be a useful landmark for accurate reproduction of humeral version. Two trained observers analyzed 101 full-humerus computed tomography scans of patients undergoing a myeloma screening protocol. Measurements of humeral retroversion relative to the TEA (angle A), humeral articular axis retroversion relative to the bicipital groove (angle B), and the bicipital groove axis relative to the TEA (angle C) were made with comparison of the measurement properties of each. Humeral retroversion relative to the TEA was 23.7° ± 8° (range, 0.2°-48.7°; 95% confidence interval, 22°-26°). The humeral articular axis was retroverted to the bicipital groove axis (angle B) by 33.5° ± 9.4° (range, 15.5°-61.7°; 95% confidence interval, 32°-35°). Overall inter-rater reliability was 0.88. Measurement of humeral head retroversion relative to the bicipital groove is not inferior to the gold-standard measurement. The bicipital groove is present both on preoperative imaging and in the operative field, making it a potential reference landmark for accurate reproduction of humeral version in shoulder arthroplasty.

Biomechanical consequences of tibial tubercle osteotomy in a 3D-printed model of patellofemoral dysplasia (207)

Biomechanical consequences of tibial tubercle osteotomy in a 3D-printed model of patellofemoral dysplasia (207)