Surgical Transepicondylar Axis Research Articles

The femoral anterior tangent line could serve as a reliable alternative reference axis for distal femoral rotational alignment in total knee arthroplasty: an MRI-based study.

This study aimed to evaluate the reference value of the femoral anterior tangent (FAT) line as a guidance of distal femoral rotation on magnetic resonance images (MRI). We retrospectively included 81 patients (106 knees) diagnosed as ailing from primary knee osteoarthritis. The indirect rotational axes including the FAT line, the perpendicular line to the anteroposterior axis (pAPA), and the posterior condylar axis (PCA) were identified on MRI, and their angles related to the clinical transepicondylar axis (cTEA) or surgical transepicondylar axis (sTEA) were measured. The patients were further divided into subgroups according to the Kellgren-Lawrence (K-L) grades, the joint-line convergence angle (JLCA), and the arithmetic hip-knee-ankle angle (aHKA) to assess the variance of different rotational reference axes. The FAT line was -11.8° ± 3.6° internally rotated to the cTEA and -7.5° ± 3.6° internally rotated to the sTEA. The FAT/cTEA angle and the FAT/sTEA angle shared a similar frequency distribution pattern but a little greater variance to the pAPA/cTEA angle and the PCA/cTEA angle. The PCA/cTEA angle in the JLCA |x| ≥ 6° subgroup was significantly smaller than in the two other JLCA subgroups. The pAPA/cTEA angle and the PCA/cTEA angle also presented statistical significance within the aHKA subgroups. While the FAT/cTEA angle and the FAT/sTEA angle demonstrated superior stability among the different K-L grades, JLCA subgroups, and aHKA subgroups. The FAT line was less affected by the degree of knee osteoarthritis and lower limb alignment, which could serve as a reliable alternative reference axis for the distal femoral rotational alignment in total knee arthroplasty.

Influence of Preoperative Deformity on Flexion Gap Asymmetry in Measured Resection Technique: A Theoretical Study in Navigated Gap Balancing Total Knee Arthroplasties, Done for Varus Knee Osteoarthritis.

Disagreement exists on (a) achieving a symmetrical flexion gap and (b) the influence of varus deformity on the flexion gap asymmetry (FGA) in measured resection (MR) total knee arthroplasty (TKA). We aimed to determine the FGA and influence of preoperative deformity on the FGA, based on the MR technique, in varus knee osteoarthritis. In 321 navigated TKAs, we released the soft tissues in extension. In 90° flexion, with the tensioner in situ, we calculated the FGA, the angle between the posterior femoral cut (planned 3° external rotation to the posterior condylar line, parallel to the surgical transepicondylar axis, or perpendicular to the Whiteside line) and the proximal tibial resection plane. The FGA values varied widely, and the risk of >2° and >3° FGA was present in at least 60% and 40% knees, respectively. These risks were high in knees with moderate and severe varus deformity. In varus knee osteoarthritis, the risk of FGA (based on the MR technique) was high, especially when the deformity was moderate to severe. Caution is required in MR TKA, and surgeons must consider safer alternatives (gap balancing or hybrid technique) to achieve a symmetrical flexion gap in these knees.

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.

Lateral trochlear inclination measured by the transepicondylar axis holds potential for evaluating trochlear dysplasia in patients with lateral patellar dislocation.

To verify that lateral trochlear inclination (LTI) measured by the transepicondylar axis can reliably be used to evaluate trochlear dysplasia (TD) on MRI and can serve as an objective indication of trochleoplasty for patients with lateral patellar dislocation (LPD). Eighty patients with recurrent LPD and eighty healthy subjects were included. TD, posterior condylar angle (PCA), and LTI measured by the posterior condylar reference line (LTIp), surgical transepicondylar axis (LTIs), and anatomical transepicondylar axis (LTIa) were assessed on MRI. The intraclass correlation coefficient (ICC) and Bland-Altman analysis were performed, the correlations and differences amongst the parameters were identified, and a binary logistic regression model was established. Each measurement had excellent inter- and intra-observer agreement. The LTIp, LTIs and LTIa were smaller in the study group than in the control group, with mean differences of 9.0°, 7.2° and 7.0°, respectively (P < 0.001). The PCA was larger in patients with LPD than in the control group (P < 0.001). LTIp was associated with PCA in the study group (r = -0.41, P < 0.001). The pathological values of LTIp, LTIs and LTIa were 11.7°, 15.3° and 17.4°, respectively. LTIs and LTIa were independent risk factors for LPD, with ORs of 7.33 (95% CI [1.06-52.90], P = 0.048) and 10.29 (95% CI [1.38-76.96], P = 0.023), respectively. The LTI can be reliably measured by MRI, but LTIp could potentially decrease the recorded value from the actual inclination angle. LTIs and LTIa are more appropriate to serve as trochleoplasty indications for patients with LPD, which could help orthopedists with surgical decision-making. Level III.

The use of an anatomic tibial baseplate in total knee arthroplasty optimizes coverage without compromising rotation: A propensity-matched evaluation

BackgroundThe aims of this study were (1) to compare in vivo coverage and rotational alignment of 2 tibial component designs: anatomic and symmetrical; and (2) to determine if coronal deformity and tibial torsion were related to rotation and coverage. MethodsPostoperative CT scans of 200 propensity score-matched patients who underwent TKA with either an anatomic (ATC) or symmetrical tibia component (STC) were analyzed. Rotation was measured using four axes: surgical transepicondylar axis (sTEA), Berger’s protocol, medio-lateral (ML) axis and posterior borders of the tibial plateau, while coverage was assessed by measuring fit and surface area. The relationship between coronal deformity, tibial torsion, rotation, and coverage was investigated. ResultsOverall, STCs had more internal rotation when measured using the sTEA (−0.6° ± 3.5 vs 0.5° ± 3.6, p = 0.03), Berger’s protocol (−21.6° ± 7.1 vs −17.9° ± 6.2, p = 0.000) and ML axes (2.9° ± 3.9 vs 8.1° ± 5.1, p = 0.000) compared to ATCs. STCs also had more posteromedial underhang (−3.3 mm ± 2.4 mm vs −1.7 mm ± 2.5 mm, p = 0.000) but smaller change in tibial torsion postoperatively (−18.4° ± 9.9° vs −13.1° ± 9.4°, p = 0.000). Tibial torsion was more pronounced in valgus than varus knees both preoperative (−25.4° ± 6.5° vs −20.2° ± 9.3°, p = 0.02) and postoperatively (−19.7° ± 7.2° vs −14.7° ± 10.3°, p = 0.04), but there was no difference in postoperative tibial torsion between ATCs and STCs in this subgroup. ConclusionThe use of an anatomic tibial baseplate optimizes coverage by reducing posterolateral overhang and posteromedial underhang. It also achieved better rotational profiles compared to STCs. However, it resulted in a larger change in tibial torsion after TKA.

Femoral coordinate system based on articular surfaces: Implications for computer-assisted knee arthroplasty

Osteoarthritis knee can be restored by total knee arthroplasty (TKA). Imageless TKA requires several anatomical points to construct a reference coordinate system to measure bone resections and implant placement. Inaccuracies in the definition of the coordinate system lead to malalignment and failure of the implant. While the surgical transepicondylar axis (sTEA) is a reliable anatomical axis to define the lateromedial axis for the femoral coordinate system (FCS), the presence of the collateral ligaments and deterioration of the medial sulcus (MS) make the registration of sTEA a challenging task. In this work, sTEA is assigned using the articular surfaces of the femoral condyles, independent of the lateral epicondyle (LE) and MS. A single 3D arc is marked on each condyle, which is transformed into a 2D arc to get the best-fit curve according to the profile of condyles. The turning point of each best-fit curve, when transformed back to 3D, defines an axis parallel to sTEA. The condyles-based sTEA is measured experimentally on a 3D-printed bone using an Optitrack tracking setup. Using the proposed method, the angle between the aTEA, sTEA, and Whiteside's line was (3.77, 0.55, and 92.72)°, respectively. The proposed method provides the same level of accuracy and improves the anatomical points registration efficiency, as there is no need to register the LE or MS.

Does the posterior condylar angle (PCA) affect the risk of an anterior cruciate ligament (ACL) tear? A case-control study in males aged 18-30

Introduction. Injuries of the ACL are the most common ligamentous injuries of the knee joint, highlighting the importance of tools to easily determine the patients from a risk group. Aims. The aims of this study were: to establish whether the posterior condylar angle (PCA) is a risk factor of ACL injury among 18-30 year-old males and to assess the differences in PCA among patients with isolated ACL injury vs. ACL injury combined with acute MCL, or meniscal injury. Methods and materials. A case group was formed, according to a priori power analysis (α = 0.05, β = 0.95), with 44 patients with an ACL injury and a control group with 44 healthy patients. Then, the case group was subdivided into three subgroups: the MCL and meniscal injured. Two lines were drawn on the axial MRI – the posterior condylar axis and the surgical transepicondylar axis. The PCA was defined as the angle between them. Statistical analyses included U Mann-Whitney, t-student independent-sample tests, linear regression models and correlation analyses. Results. The mean PCA in the control and study group was 1.90° ±1.25° and 1.30° ±2.49°(p = 0.178), respectively. Univariate analyses of PCA in isolated ACL injury vs. ACL injury combined with acute MCL, MM or LM injury had p values of 0.981, 0.814 and 0.813, respectively. Multivariable analysis had p values of 0.744, 0.421 and 0.873, respectively. Intrarater ICCs were 0.931 and 0.928 (excellent reliability) and interrater ICCs was 0.868 (good reliability). Conclusions. PCA is not associated with acute ACL injuries in the studied population. MCL or meniscal injuries did not alter PCA values among patients with an ACL injury.

Postoperative femoral component rotation using posterior condylar referencing is difficult to predict preoperatively in total knee arthroplasty

BackgroundMany modern total knee arthroplasty (TKA) systems use posterior condylar axis (PCA) to derive the surgical trans-epicondylar axis (sTEA), which is widely regarded as the gold standard for femoral component rotation. However, the previous imaging studies showed that cartilage remnants can alter component rotation. We therefore conducted this study to determine how the postoperative femoral component rotation deviated from the preoperative plan using three-dimensional (3D) computed tomography (CT) which does not consider cartilage thickness. MethodsA total of 123 knees of 97 consecutive osteoarthritis patients who underwent the same primary TKA system using PCA reference guide were included. External rotation was set at 3°or 5° according to the preoperative 3D CT plan. The number of varus knees (hip–knee–ankle (HKA) angle >5° varus) and valgus knees (HKA >5° valgus) were 100 and 5, respectively. The deviation from the preoperative plan was measured using overlapping pre- and postoperative 3D CT images. ResultsThe mean (standard deviation, range) deviation from the preoperative plan in varus group, external rotation setting of 3°, 5° in varus group and valgus group were 1.3° (1.9°, −2.6° − 7.3°), 1.0° (1.6°, −2.5° − 4.8°), 3.3° (2.3°, −1.2° − 7.3°), and −0.8° (0.8°, −2.0°−0.0°), respectively. No correlation was found between the deviation from the plan and the preoperative HKA angle in varus group (R = 0.15, P = 0.15). ConclusionsThe effect of asymmetric cartilage wear for rotation in the present study was supposed to be approximately 1° as mean value, but it can vary widely from patient to patient.

The Definition of the Tibial Sagittal Plane and the Paradox of Imageless Navigation and Robotics: A Cadaveric Study

BackgroundThe accuracy, precision, and repeatability by which the tibial sagittal plane can be found with imageless technology is currently unknown. The purpose of this study was to identify any differences between imageless and image-based technology to define the sagittal plane of the tibia. MethodsA computed tomography (CT) was obtained of 18 cadavers with the knee fully extended. The surgical trans-epicondylar axis and several tibial rotation references were acquired on the CT scan. After a medial parapatellar approach, the same anatomical landmarks were acquired in vivo. In the horizontal plane, the angle between the surgical trans-epicondylar axis and the tibial rotational axes was assessed. ResultsHighest accuracy was found for posterior cruciate ligament (PCL)–anterior cruciate ligament (ACL, −1.48°, standard deviation [SD] 13.64; imageless), tibial medial condyle (TMC)–tibial lateral condyle (TLC, 1.72°, SD 4.24; image-based), the ACL-medial border of tibial tuberosity (MTT, −2.89°, SD 18.86; image-based). Highest precision was acquired with image-based technology: TMC-TLC (SD 4.24), PCL-ACL (SD 5.86), and PCL-medial third of tibial tuberosity (M3TT, SD 7.10). Excellent intraobserver and interobserver correlation coefficients were observed with image-based technology: PCL-MTT, anterior medial condyle (AMC)-anterior lateral condyle (ALC), and TMC-TLC (Intraobserver and interobserver correlation coefficients 0.90-0.98). ConclusionThe tibial sagittal plane could be defined with highest accuracy, precision, and repeatability on a preoperative CT. Imageless methodology lacked the precision and repeatability of image-based technology. With the current pursuit of high accuracy and precision in total knee arthroplasty, the reference frame used to quantify implant position should be highly accurate and precise as well. Level of evidenceIV, Case Series.

Femoral Anteversion Measured by the Surgical Transepicondylar Axis Is Correlated with the Tibial Tubercle–Roman Arch Distance in Patients with Lateral Patellar Dislocation

Background and Objectives: Various predisposing factors for lateral patellar dislocation (LPD) have been identified, but the relation between femoral rotational deformity and the tibial tubercle-Roman arch (TT-RA) distance remains elusive. Materials and Methods: We conducted this study including 72 consecutive patients with unilateral LPD. Femoral anteversion was measured by the surgical transepicondylar axis (S-tAV), and the posterior condylar reference line (P-tAV), TT-RA distance, trochlear dysplasia, knee joint rotation, patellar height, and hip-knee-ankle angle were measured by CT images or by radiographs. The correlations among these parameters were analyzed, and the parameters were compared between patients with and without a pathological TT-RA distance. Binary regression analysis was performed, and receiver operating characteristic curves were obtained. Results: The TT-RA distance was correlated with S-tAV (r = 0.360, p = 0.002), but the correlation between P-tAV and the TT-RA distance was not significant. S-tAV had an AUC of 0.711 for predicting a pathological TT-RA, with a value of >18.6° indicating 54.8% sensitivity and 82.9% specificity. S-tAV revealed an OR of 1.13 (95% CI [1.04, 1.22], p = 0.003) with regard to the pathological TT-RA distance by an adjusted regression model. Conclusions: S-tAV was significantly correlated with the TT-RA distance, with a correlation coefficient of 0.360, and was identified as an independent risk factor for a pathological TT-RA distance. However, the TT-RA distance was found to be independent of P-tAV.

A computed tomographic evaluation of femoral and tibial rotational reference axes in total knee arthroplasty

The surgical trans epicondylar axis (sTEA) is considered the gold standard for optimum rotation of the femoral component; however, no consensus exists on tibial component positioning. The objectives of this study were to determine the relationship of sTEA to various femoral and tibial reference axes in varus osteoarthritis (OA) knees and (ii) to study the intra-observer and inter-observer variability of the axis relationships. The study was done on preoperative computerised tomogram (CT) scans of 110 varus knees to assess the rotational relationships respectively of femoral side sTEA with whitesides line (WSL), posterior condylar axis (PCA), clinical trans epicondylar axis (cTEA) and on the tibial side sTEA with posterior tibial margin (PTM), anterior condylar axis (ACA), Akagi's line and line from the geometric centre of the tibial plateau to 1/3rd tibial tubercle (line GC 1/3rd TT). On the femoral side the mean angles of sTEA with WSL, PCA, cTEA were 95.64°±2.85°, 1.77°±1.88°, 4.19°±0.99° respectively. On the tibial side, the mean angles of sTEA with, PTM, ACA, Akagi's line, and line GC 1/3rd TT were 1.10°±4.69°, 11.98°±4.51°, 2.43°±4.35°, 16.04°±5.93° respectively. Contrary to the generalization, TEA has variable relationships. The surgical trans epicondylar axis was not at the assumed 3° of external rotation to PCA in 85% of knees, nor perpendicular to WSL in >95%of knees. Of the four tibial axes, Akagi's line was the least variable with sTEA. Furthermore, surgeons should also be aware of the multiple reference axes and the range of deviation from sTEA to optimize the rotational alignment of components.

Surgical Transepicondylar Axis Is Not a Reliable Reference when there Was Lateral Femoral Bowing.

The surgical transepicondylar axis (sTEA) is believed to be a consistent reference for femoral rotation axis, and the reliability of its orientation seriously affects the accuracy and outcome of total knee arthroplasty (TKA). This study was designed to investigate the relationship between the orientation of sTEA and femoral bowing angle (FBA) and posterior condylar line (PCL) using three-dimensional (3D) computed tomography (CT) reconstruction models to verify its reliability. This study retrospectively collected lower extremity images of 443 southern Chinese osteoarthritic patients (347 women, 96 men; 234 left, 209 right; mean age 66.5 ± 9.3 years) from August 2016 to June 2018. The hip-knee-ankle angle (HKA) was measured on anteroposterior weight-bearing full lower extremity standing radiographs. Measurements on 3D CT models of the femurs included lateral angle between the femoral mechanical axis and sTEA coronal angle, angle between sTEA and distal joint line (distal condylar axis angle, DCA); angle between sTEA and PCL (sTEA axial angle); angle between anatomical axis of proximal femur and anatomical axis of distal femur in the plane they form (actual FBA) and its projection on the coronal (lateral FBA) and sagittal (anterior FBA) planes. The correlations between sTEA coronal angle, sTEA axial angle and actual FBA, lateral FBA, anterior FBA, HKA, DCA were explored using the Spearman correlation test. The mean value of actual FBA is (14.4± 3.6)°, of lateral FBA is (6.0 ± 4.0)°, and of anterior FBA is (12.7± 3.0)°. The mean value of sTEA coronal angle is (88.7± 3.6)°, of sTEA axial angle is (2.1± 2.8)°. The sTEA coronal angle was positively correlated with actual FBA (r=0.320, P < 0.01), lateral FBA (r=0.448, P < 0.01), anterior FBA (r=0.113, P < 0.05), HKA (r=0.482, P < 0.01) and DCA (r=0.486, P < 0.01). The sTEA axial angle was positively correlated with DCA (r=0.168, P < 0.01), but not significantly correlated with all FBAs and HKA (NS). The sTEA cannot be used as a stable reference when there was an obvious femoral bowing deformity. As the lateral femoral bowing increases, the orientation of sTEA becomes more varus, no matter the knee is varus or valgus.

Could surgical transepicondylar axis be identified accurately in preoperative 3D planning for total knee arthroplasty? A reproducibility study based on 3D-CT

BackgroundSurgical transepicondylar axis (sTEA) is frequently used for positioning of femoral component rotation in total knee arthroplasty (TKA). Previous studies showed that intraoperative identification of sTEA was not reliable. While surgeons or engineers need to identify sTEA with three-dimensional (3D) computer-aid techniques pre- or intraoperatively, the reproducibility of sTEA identification on preoperative 3D images has not been explored yet. This study aimed to investigate the reproducibility of identifying sTEA in preoperative planning based on computed tomography (CT).MethodsFifty-nine consecutive patients (60 knees involved) who received TKA in our center from April 2019 to June 2019 were included in this study. Six experienced TKA surgeons identified sTEA three times on 3D model established on the basis of knee CT data. The projection angle of each sTEA and the posterior condyle axis on the transverse plane were measured and analyzed.ResultsThe overall intra-observer reproducibility was moderate. The median intra-observer variation was 1.27°, with a maximum being up to 14.07°. The median inter-observer variation was 1.24°, and the maximum was 11.47°. The overall intra-class correlation coefficient (ICC) for inter-observer was 0.528 (95% CI 0.417, 0.643).ConclusionThe identification of sTEA on a 3D model established on the basis of knee CT data may not be reliable. Combined with the previous cadaveric and surgical studies, caution should be exercised in determining femoral component rotation by referencing sTEA both preoperatively and intraoperatively.Level of evidenceIII

Comparison of Tibial Tubercle Landmark Technique and Range of Motion Technique in Primary Total Knee Arthroplasty: A Retrospective Cohort Study.

There is not a standard for rotational alignment of the tibial component in total knee arthroplasty (TKA). For now, the most commonly methods are tibial-tubercle -landmark technique (TTL) and range-of-motion technique (ROM). The study is aimed to compare clinical outcomes and radiographic data of patients who undergone primary TKA with TTL or ROM technique. This single-surgeon retrospective cohort study includes 60 patients with TTL technique and 60 with ROM technique from December 2017 to January 2019. All patients were evaluated clinically using Hospital for Special Surgery Knee Score (HSS), Feller patellar score, visual analogue scale (VAS) and maximum knee flexion and extension angle before and after surgery at both 6 months and 12months postoperatively. Radiographic data contain hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), posterior slope angle (PSA) on pre and postoperative X-ray and rotation angle of femoral component (relative to surgical trans-epicondylar axis) and tibial component (relative to surgical trans-epicondylar axis, tibial posterior condylar line and Akagi') on postoperative computed tomography (CT) scan. Clinical outcomes and radiological data were compared between the two groups. One hundred twenty patients (120 knees) were enrolled in this study, including 38 males and 82 females, aged from 58 to 78, with an average of 65.7 years. There was no significant difference in demographics and preoperative X-ray data between the two groups (P > 0. 05). Clinical scores of the TTL group were better than those in the ROM group at 6 and 12months after surgery, when comparing HSS (83.57 ± 5.00 vs 75.90 ± 4.89, F=59.004, P < 0.001; 90.53 ± 4.31 vs 82.83 ± 4.98, F=54.509, P < 0.001), Feller patellar score (21.43 ± 2.54 vs 19.10 ± 2.52, F=14.864, P=0.001; 26.27 ± 1.98 vs 23.20 ± 2.31, F=42.204, P < 0.001) and VAS (3.70 ± 0.62 vs 4.38 ± 0.92, F=14.508, P=0.001; 2.10 ± 0.90 vs 2.79 ± 0.80, F=11.554, P=0.002). But there was no significant difference in the flexion and extension angle between the two groups. In imaging evaluation, no statistical difference was found in pre- and postoperative HKA, mLDFA, mMPTA and PSA. Rotational angles of tibial component only did relative to Akagi' have statistical difference in two groups (2.33 ± 4.3 vs 4.41 ± 3.2, t=2.143, P < 0.05) (Positive value represented external rotation). The results of our study showed that both methods were reliable, and TTL technique provided better clinical scores and larger external angle of tibial component, compared to ROM technique.

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.

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.

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.