Femoral Rotational Alignment Research Articles

Impact of operative position on rotational alignment after intramedullary nailing of trochanteric fractures: a comparative analysis of lateral decubitus versus supine position.

Fixation of trochanteric fractures with an intramedullary nail in a non-physiological position can cause poor functional outcomes. The aim of this study is to evaluate the effect of intraoperative patient position on rotational alignment in intramedullary nail fixation of trochanteric fractures. The femoral rotational alignment of 84 trochanteric fracture patients who underwent intramedullary nailing was measured by computed tomography (CT) images. Patients were divided into two groups: the supine position on the fracture table (FT) (Group 1, n = 42) and the lateral decubitus (LD) position (Group 2, n = 42). Femoral malrotation angles were measured and divided into three subgroups: insignificant, significant,andexcessive.The number of intraoperative fluoroscopy images, preparation time, surgery time, and anesthesia time in both groups were compared. The malrotation degrees of patients in Group 1 ranged from 17° external rotation (ER) to 57° internal rotation (IR), with a mean of 10° IR. Of the patients in Group 1, 27 were insignificant, 5 were significant, and 10 were in the excessive subgroup. The malrotation degrees of patients in Group 2 ranged from 33° ER to 47° IR, with a mean of 11° IR. Of the patients in Group 2, 21 were insignificant, 12were significant, and 9 were in the excessive subgroup. There was no statistically significant relationship between patient position and malrotation angle. The number of intraoperative fluoroscopy images, preparation time, and anesthesia time were statistically lower in Group 2. There was no statistically significant difference between Group 1 and Group 2 in terms of surgery time. Intramedullary nailing in the LD position is a reliable and practical surgical method in the treatment of femoral trochanteric fractures since there is no need for the use of a FT, the surgeon is exposed to less radiation, there is no risk of complications related to the traction of the FT, and there is a shorter operation time.

Anatomical Reference of the Femur after Distal Resection Is Reliable for Rotational Alignment in Total Knee Arthroplasty.

The rotational alignment of the femoral component in total knee arthroplasty (TKA) is considered an important factor, but it is still difficult to assess intraoperatively. This study was conducted to identify anatomical parameters for femoral rotational alignment. A total of 204 patients who underwent primary TKA between 2015 and 2019 were enrolled. The femoral lateral (FLAP) and femoral medial anteroposterior (FMAP) lengths were measured as the widest lengths in the anteroposterior (AP) axis after distal femoral resection. The difference between FLAP and FMAP was defined as dFAP. The concordance correlation coefficient (CCC) was assessed for agreement between the cTEA-PCA and the value of femoral rotation using the linear regression analysis equation. HKA, FLAP, FMAP, and dFAP were significantly associated with femoral rotational alignment. The prediction equation combining the novel intraoperative anatomical references showed improved association with rotational alignment. If dFAP was 6.0 mm, the femoral rotation angle was calculated as 4.9° using this univariate regression equation. The CCC was 0.483, indicating moderate agreement. The dFAP showed an association with distal femoral rotational alignment. A 6 mm dFAP could be a reference for around 5° of femoral rotation. The equation developed in this study may be a reliable tool for intraoperative distal femoral rotational alignment.

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.

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.

Accuracy and reproducibility analysis of different reference axes for femoral prosthesis rotation alignment in TKA based on 3D CT femoral model

BackgroundThere are many reference axes to determine the rotational positioning of the femoral prosthesis in total knee arthroplasty (TKA), mainly including the surgical transepicondylar axis (sTEA), anatomical transepicondylar axis (aTEA), Whiteside line, and the posterior condylar line (PCL), etc., but there is still no definite conclusion on which is the most accurate reference axis.ObjectiveTo explore the reproducibility of each reference axis of femoral external osteotomy based on the 3D CT femoral model, compare the deviation of the simulated femoral prosthesis rotation alignment, positioned based on each reference axis, with the gold standard sTEA, and analyze the accuracy of each reference axis.MethodsThe imaging data of 120 patients with knee osteoarthritis who underwent a 3D CT examination of the knee in our hospital from June 2018 to December 2021 were retrospectively collected. The 3D model of the femur was established by Mimics software. The line relative to PCL externally rotated 3° (PCL + 3°), aTEA, and the vertical line of the Whiteside line were constructed and compared with the gold standard sTEA. Intra-observer, as well as inter-observer reproducibility analysis, was performed by the intra-group correlation coefficient (ICC) and Bland-Altman method.ResultsThe angle ∠WS, between the vertical line of Whiteside and sTEA, was 2.54 ± 2.30°, with an outlier of 54.2%; the angle ∠aTEA, between aTEA and sTEA, was 4.21 ± 1.01°, with an outlier of 99.1%; the angle ∠PCL, between PCL + 3° external rotation and sTEA, was 0.50 ± 1.06°, with the highest accuracy and an outlier of 5.8%, and the differences among all three were statistically significant, P < 0.05. The intra-observer ICC values of ∠WS, ∠aTEA, and ∠PCL were 0.975 (0.964–0.982), 0.926 (0.896–0.948), and 0.924(0.892,0.946), respectively, and the reproducibility levels were excellent; the inter-observer ICC values of ∠WS, ∠aTEA, and ∠PCL were 0.968(0.955–0.978), 0.906 (0.868–0.934) and 0.970 (0.957,0.979), respectively, with excellent reproducibility levels; Bland-Altman plots suggested that the scatter points of intra-observer and inter-observer measurement differences more than 95% were within the limits of agreement.ConclusionThe reference axis for locating the distal femoral external rotation osteotomy based on the 3D CT femoral model has good reproducibility. The PCL is easy to operate, has the highest precision, and the lowest outliers among the reference axes is therefore recommended.

Virtual Joint Motion Simulator Accurately Predicts Effects of Femoral Component Malalignment during TKA.

Component alignment accuracy during total knee arthroplasty (TKA) has been improving through the adoption of image-based navigation and robotic surgical systems. The biomechanical implications of resulting component alignment error, however, should be better characterized to better understand how sensitive surgical outcomes are to alignment error. Thus, means for analyzing the relationships between alignment, joint kinematics, and ligament mechanics for candidate prosthesis component design are necessary. We used a digital twin of a commercially available joint motion simulator to evaluate the effects of femoral component rotational alignment. As anticipated, the model showed that an externally rotated femoral component results in a knee which is more varus in flexion, with lower medial collateral ligament tension compared to a TKA knee with a neutrally aligned femoral implant. With the simulation yielding logical results for this relatively simple test scenario, we can have more confidence in the accuracy of its predictions for more complicated scenarios.

Component Rotation in Well-Functioning, Gap Balanced Total Knee Arthroplasty Without Navigation

BackgroundMalalignment of total knee arthroplasty (TKA) components is a potential cause of clinical failure following TKA. Since the goal of a gap balancing (GB) technique is equal flexion and extension gaps secondary to soft-tissue balancing, and not necessarily component alignment, variation in component placement may exist. Our purpose was (1) to evaluate precision of component alignment in well-functioning GB TKAs performed without the aid of navigation using computed tomographic evaluation and (2) to determine any relationship between femoral version and/or tibial torsion and TKA component positioning. MethodsThere were 93 well-functioning TKAs performed with an extension gap first GB technique with a minimum 2-year follow-up evaluated using computed tomography to assess component rotational alignment, as well as osseous femoral version and tibial torsion. Femoral and tibial rotational alignment was assessed by previously described methods. ResultsThe mean Knee Society Score was 185.7 ± 21.7. The mean range of motion was 128.5 ± 7.8°. Femoral posterocondylar axis (relative to the transepicondylar axis) values ranged from −8.3 to 4.1° with a mean of −0.78 ± 2.7° (internal rotation). Mean tibial rotation was 17.2 ± 7.9° internal rotation relative to the tibial tubercle. No correlation was found between native femoral version and femoral component rotational alignment (Pearson’s correlation coefficient, r, 0.007). Weak correlation was found between native tibial torsion and tibial component alignment (r = 0.24). ConclusionDespite being only a secondary objective with the GB technique, most components evaluated were within the desired range of rotation. Alignment was not influenced by native osseous rotational geometry. Level of EvidenceLevel III, Retrospective Cohort Study.

Intraindividual variance of lower limb rotation in patients with bilateral knee osteoarthritis.

To determine the side-to-side difference in intraindividual rotation alignment of patients with bilateral varus-type knee osteoarthritis (OA) and compare it with control subjects. This retrospective study enrolled 60 patients with bilateral varus-type knee OA and 50 control subjects. All cases underwent bilateral lower limb CT angiography. Bilateral femoral and tibial rotation alignment were measured, and the overall lower limb rotation was calculated by two different methods. Method 1 was calculated by subtracting angle of the femoral torsion from the tibial torsion and method 2 was determined by relative rotation of the femoral neck angle to bimalleolar angle. The intraindividual variance and differences between the two groups were analyzed. Both OA and control samples showed significant differences between right and left for all measurements. Femoral torsion for control group was 10.4 ± 5.5°, tibial torsion was -22.1 ± 6.1°, and overall leg rotation by method 1 was -15.6 ± 7.2° and method 2 was -11.7 ± 8.2°. Femoral torsion, tibial torsion, method 1, and method 2 in the patients with OA were 8.2 ± 6.3°, -18.6 ± 4.1°, -14.9 ± 7.9°, and -10.4 ± 7.6°, respectively. Patients with OA showed a more pronounced retroversion in the femur (p = 0.008) and more internal rotation in the tibia (p < 0.001). No statistical significance of both methods was found between the two groups. Patients with OA had a greater median side-to-side absolute difference in all measurements, though the differences of both two methods of overall lower limb rotation were not statistically significant. The discrepancy of side-to-side differences of bilateral lower limb rotation ought to be noticed with caution in diagnosing and treating rotational deformities of the lower limb, especially for patients with bilateral knee OA.

Medial trochlea superior surface-a new bony landmark to assist the femoral rotational alignment in the total knee arthroplasty.

Medial trochlea superior surface-a new bony landmark to assist the femoral rotational alignment in the total knee arthroplasty.

Patient-specific instrumentation for total knee arthroplasty improves reproducibility in the planned rotational positioning of the tibial component

BackgroundThe purpose of this study was to evaluate the reproducibility of planned component positioning including tibial rotational alignment in patient-specific instrumentation (PSI) for total knee arthroplasty (TKA).MethodsA total of 100 knees of 100 patients underwent TKA using PSI (n = 50) or the conventional method (n = 50). Full-length anteroposterior radiographs of the lower limb were taken in the standing position, and the coronal alignments of the femoral and tibial components were measured. Computed tomography (CT) images of the lower limb were obtained preoperatively and postoperatively, and the rotational alignments of the femoral and tibial components were measured. The difference from the preoperative planning in tibial rotational alignment was measured using three-dimensionally merged pre- and postoperative images. The mean values and rates of outliers in each measurement were compared between the PSI group and the conventional group.ResultsThere were no significant differences in coronal alignment of the femoral and tibial components and rotational alignment of the femoral component between the two groups. With respect to rotational alignment of the tibial component from the preoperatively planned reference axis, the PSI group showed a lower rate of outliers (internal rotation > 10°) than the conventional group (p < 0.05).ConclusionsThis study demonstrated that the difference from the preoperative planning in tibial rotational positioning was accurately evaluated using novel three-dimensional measurement method, and PSI could reduce outliers in rotational alignment of the tibial component (internal rotation > 10°). PSI is a useful technique for improving the reproducibility of the planned tibial rotational positioning in TKA.

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.

A Newly Designed “SkyWalker” Robot Applied in Total Knee Arthroplasty: A Retrospective Cohort Study for Femoral Rotational Alignment Restoration

ObjectiveThis study explored whether robotic arm‐assisted total knee arthroplasty (RATKA) has the advantage of restoring femoral rotational alignment compared to conventional total knee arthroplasty (COTKA).MethodsSixty patients (45 women and 15 men) attending our department from May 2019 to December 2020 were selected and divided into two groups, with 30 patients in each group, according to whether they underwent COTKA or RATKA. Femoral rotational alignment results, such as, posterior condylar angle (PCA), patella transverse axis‐femoral transepicondylar axis angle (PFA), radiological findings, such as, hip‐knee‐ankle angle (HKA), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA), and operative data (operation time, intraoperative blood loss, tourniquet time, and length of stay (LOS), and clinical outcomes, such as maximum knee flexion angle (MKFA), Knee Society Score (KSS), and Western Ontario Mac Master University Index Score (WOMAC) were compared within and between the two groups.ResultsPCA and PFA in the RATKA group were (0.6 ± 0.3)° and (0.9 ± 0.3)°, respectively, which were smaller than (1.5 ± 2.0)° and (3.1 ± 1.1)° in the COTKA group (P < 0.05), and were closer to 0°; the differences in HKA, LDFA, and MPTA were not statistically significant. With the exception of the LDFA, the HKA, MPTA, PCA, and PFA improved in both groups after surgery (P < 0.05). The blood loss and the LOS of RATKA group were 192.3 ± 23.1 mL and 8.2 ± 1.4 days, which were less than 203.7 ± 29.8 mL and 9.3 ± 1.1 days of the COTKA group, but the operation time showed no statistically significant difference, and the tourniquet time was longer (P < 0.05). The MKFA in the RATKA group was (123.0 ± 3.7)°, which was greater than (116.3 ± 4.6)° in the COTKA group (P < 0.05). In terms of scores, the postoperative results were better than the preoperative results in both groups (P < 0.05). However, there was no statistically significant difference between the groups.ConclusionThe accuracy of femoral rotational alignment reconstructed achieved by RATKA is significantly better than that of COTKA and is more conducive to the recovery of knee flexion function after surgery; although RATKA reduces intraoperative blood loss and postoperative LOS, the short‐term clinical efficacy comparison has not yet demonstrated the advantages of robotic technology, and a more optimized design is needed to improve the efficiency of RATKA surgery.

Rotational abnormalities in dysplastic hips and how to predict acetabular torsion

ObjectivesThe aim of this study was to investigate the degree to which conventional radiography can represent the acetabular and femoral rotational alignment profile between dysplastic and borderline-dysplastic hips.MethodsA retrospective trial was conducted including 56 borderline-dysplastic and dysplastic hips at a mean age of 28.9 years (range from 18 to 46). Inclusion criteria consisted of symptomatic patients with hip dysplasia undergoing 2-dimensional radiography as well as computed tomography. On radiography, the lateral center edge angle, acetabular hip index, hip lateralization index, acetabular index angle, and the Sharp angle were measured, and the presence of a crossover sign was noted. In computed tomography, the full rotational profile of the lower limb was measured.ResultsSignificant correlations were observed in the overall analysis between the anteversion of the acetabulum and the hip lateralization index (mean 0.56, coefficient of regression (CoR) −32.35, p = 0.011) as well as the acetabular index angle with a mean of 11.50 (CoR 0.544, p = 0.018). Similar results were found in the subgroup of dysplastic hips with an acetabular index angle of 13.9 (p = 0.013, CoR 0.74). For the borderline-dysplastic group, no significant correlations between the pelvis radiography and rotational CT were seen.ConclusionAlthough the femoral and acetabular torsion cannot be predicted from x-rays, the anteversion of the acetabulum correlates with the acetabular index angle, the hip lateralization index, and eventually the beta angle in dysplastic hips. For borderline-dysplastic hips, such results did not show up, which strongly illustrates the need for computed tomography in these cases.Key Points• Much of the current literature focuses on rotational alignment especially with respect to the femur and tibia in healthy patients, although little is known about the acetabular, femoral, and tibial torsion in dysplastic hips.• This is the first study showing significant correlations between the anteversion of the acetabulum and the hip lateralization index as well as the acetabular inclination angle. Also, it is the first study to provide a mechanism for estimation of the torsion of the acetabulum with plain radiography in dysplastic hips.• In borderline-dysplastic hips, no significant correlation was found, which raises the question if a simple x-ray has enough validity to address the acetabular deformity with surgery.

The Presence of Cartilage Affects Femoral Rotational Alignment in Total Knee Arthroplasty.

ObjectiveTo assess the difference between the posterior condylar angle (PCA) and the mechanical lateral distal femoral angle (mLDFA) in the osseous and cartilaginous contours in a non-arthritic Chinese population.MethodsComputed tomography (CT) and magnetic resonance imaging (MRI) were obtained from 83 patients with knee injuries before arthroscopy, and femur and distal femoral cartilage three-dimensional (3D) models were constructed. The 3D cartilage model was arranged to share physical space with the 3D femoral model, and then PCA and mLDFA were measured on the osseous and cartilaginous contours, respectively. The differences between the measurements with and without cartilage were evaluated.ResultsThe average PCA with cartilage was 2.88 ± 1.35° and without was 2.73 ± 1.34°. The difference was significant in all patients and females but not in males. The average mLDFA with cartilage was 84.73 ± 2.15° and without cartilage was 84.83 ± 2.26°, but the difference was statistically insignificant in all groups.ConclusionPCA on the osseous and cartilaginous contours significantly differed with and without cartilage in the female group, suggesting that cartilage thickness should be considered during preoperative femoral rotational resection planning.

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.

Effect of femoral component rotational alignment in total knee arthroplasty by using 3D-printed patient-specific instruments: a prospective randomized control study

Objective: To compare the difference between two total knee arthroplasty (TKA) techniques, patient-specific instrumentation (PSI) and conventional instrumentation (CI), regarding the rotational alignment of femoral components. Methods: A prospective, randomized controlled trial in 80 patients with severe knee osteoarthritis who underwent primary unilateral TKA from October 2018 to December 2019 in Peking University Third Hospital was carried out. There were 63 females and 17 males, with an average age of 69 years. The patients were assigned to either PSI-TKA group (n=40) or CI-TKA group (n=40) with bluster random method (block size 4). The femoral component rotation on the transepicondylar axis, the outlier rate of rotational alignment, the rate of anterior knee pain, and the clinical outcomes including HSS and WOMAC score at 1-year follow-up were documented and analyzed. Results: Although no significant difference in femoral component rotational alignment was found between the two groups (CI-TKA: 0.7°, PSI-TKA: 0.6°, P=0.279), the PSI-TKA group achieved less coefficient of variation of rotational alignment (1.50 vs 2.14) and the distributions of the outliers (19.4% vs 7.9%, P=0.185). Six patients (8.1%) experienced anterior knee pain at 1-year follow-up. No significant difference regarding the incidence of anterior knee pain, the HSS, and WOMAC score was found between the two groups one year after the operation (all P>0.05). Conclusions: The satisfied postoperative rotational alignment of femoral components can be attained with the application of PSI in comparison with conventional instrumentation. In addition, PSI offers a potential benefit in the reduction of alignment outliers.

Effect of robotic-arm assisted total knee arthroplasty on femoral rotation alignment and its short-term effectiveness

To investigate the improvement of femoral rotation alignment in total knee arthroplasty (TKA) by robotic-arm assisted positioning and osteotomy and its short-term effectiveness. Between June 2020 and November 2020, 60 patients (60 knees) with advanced osteoarthritis of the knee, who met the selection criteria, were selected as the study subjects. Patients were randomly divided into two groups according to the random number table method, with 30 patients in each group. Patients were treated with robotic-arm assisted TKA (RATKA) in trial group, and with conventional TKA in control group. There was no significant difference in gender, age, side and course of osteoarthritis, body mass index, and the preoperative hip-knee-ankle angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), posterior condylar angle (PCA), knee society score-knee (KSS-K) and KSS-function (KSS-F) scores between the two groups ( P>0.05). The clinical (KSS-K, KSS-F scores) and imaging (HKA, LDFA, MPTA, PCA) evaluation indexes of the knee joints were compared between the two groups at 3 months after operation. All patients were successfully operated. The incisions in the two groups healed by first intention, with no complications related to the operation. Patients in the two groups were followed up 3-6 months, with an average of 3.9 months. KSS-K and KSS-F scores of the two groups at 3 months after operation were significantly higher than those before operation ( P<0.05), but there was no significant difference between the two groups ( P>0.05). X-ray re-examination showed that the prosthesis was in good position, and no prosthesis loosening or sinking occurred. HKA, MPTA, and PCA significantly improved in both groups at 3 months after operation ( P<0.05) except LDFA. There was no significant difference in HKA, LDFA, and MPTA between the two groups ( P>0.05). PCA in trial group was significantly smaller than that in control group ( t=2.635， P=0.010). RATKA can not only correct knee deformity, relieve pain, improve the quality of life, but also achieve the goal of restoring accurate femoral rotation alignment. There was no adverse event after short-term follow-up and the effectiveness was satisfactory.

Evaluation of an operation support system using the femoral anterior tangent line to determine intraoperative femoral component rotation in total knee arthroplasty

BackgroundThe femoral anterior tangent (FAT) line refers to a line parallel to the anterior surface of the distal femur in the axial plane. This study aimed to evaluate the effectiveness of a new operation support system which uses the FAT line to set the femoral component rotational alignment in total knee arthroplasty (TKA). MethodsA total of 170 consecutive knees in 139 patients undergoing primary TKA with the JIGEN (Jig Engaged Three-dimensional (3D) Pre-Operative Planning Software for TKA) operation support system was examined. The JIGEN system creates 3D models of bones using computed tomography data, allowing for surgical simulations such as positioning of implants while calculating positions of the intramedullary alignment rod (IM rod) and surgical jig. We retrospectively analyzed the FAT line angle relative to the surgical epicondylar axis (SEA) on the axis plane perpendicular to the IM rod and evaluated the accuracy of the femoral component alignment after TKA with the 3D measurement system. ResultsThe FAT line was 9.6° ± 3.7° (range, 1.4°–20.4°) internally rotated relative to the SEA. The average absolute error was 1.4° ± 1.1° in the coronal plane, 2.0° ± 1.5° in the sagittal plane, and 1.6° ± 1.3° in the axial plane. The femoral component outliers (i.e., >3° away from the goal alignment) were 7.7% in the coronal plane, 20.6% in the sagittal plane, and 10.3% in the axial plane. ConclusionsOur findings suggest that the FAT line is a reliable and reproducibly identifiable axis for the accurate determination of proper rotational alignment in TKA. An operation support system which uses the FAT line for determining intraoperative femoral component rotation can effectively achieve highly accurate positioning of the femoral component in TKA.

Reliability of Imageless Computer-Assisted Navigation for Femoral Rotational Alignment in Total Knee Arthroplasty.

Introduction:The aim of this study was to evaluate the reliability of the femoral component rotation on intra-operative data recorded in a computer-assisted navigation system (CAN-FRA) compared with the post-operative femoral component rotation observed on computed tomography (CT-FRA).Material and method:Computer-assisted total knee arthroplasty (TKA) or primary osteoarthritis of the knee was performed in 51 knees in 36 patients with a mean age of 69.51 years. All procedures were performed by a single surgeon using the same implant design. The intraclass correlation coefficient (ICC) was used to compare the intra-operative CAN-FRA with the post-operative CT-FRA. The angle between the anatomical epicondylar axis and the posterior condylar axis of the implant (CT-FRA) was measured at two separate timepoints by three observers who were blinded to the intra-operative CAN-FRA. Internal rotation was defined as rotation in the negative direction, while external rotation was defined as positive.Results:The mean intra-operative CAN-FRA was 0.1° ± 2.8° (range -5.0° to 5.5°). The mean post-operative CT-FRA was -1.3° ± 2.1° (range -4.6° to 4.4°). The mean difference between the CAN-FRA and the CT-FRA was -1.3° ± 2.2° (range -7.9° to 2.4°). The respective ICC values for the three observers were 0.92, 0.94, and 0.93, while the respective intra-observer coefficients were 0.91, 0.85, and 0.90. The ICC for the intra-operative CAN-FRA versus the post-operative CT-FRA was 0.71.Conclusion:This study shows that using a computer-assisted navigation system in TKA achieves reliable results and helps to achieve optimal positioning of the femoral component and rotation alignment correction.

The posterior cortical axis as an alternative reference for femoral component placement in total knee arthroplasty

BackgroundAlthough several reference axes have been established for determining femoral rotational alignment during total knee arthroplasty (TKA), the most accurate axis is undetermined. This study determines the relationship between the posterior cortical axis (PCA) and the trochlear anterior line (TAL) of the femur in relation to the epicondylar axis.MethodsA total of 341 patients who underwent TKA for osteoarthritis were enrolled. Patients who had undergone previous bony surgery or replacement that might have changed the femoral geometry were excluded. Finally, 336 patients (200 females and 136 males) were included in the study. The angles between the transepicondylar axis (TEA) and TAL and TEA and the femoral PCA (FPCA) were evaluated. We also assessed whether there was any significant differences in variance and gender in these two angles. Student’s t tests were used to determine the significance of coronal alignment and any gender-based differences. The variances between the TAL/TEA and FPCA/TEA angles were compared using F tests.ResultsThe FPCA was externally rotated by 2.6° ± 3.6°, and the trochlear anterior line was internally rotated by 5.2° ± 5.5°, relative to the TEA. Gender-based differences were observed in the comparisons between anatomical references and TEA.ConclusionsThe FPCA is a more conservative landmark than the TAL for intraoperative or postoperative approximation of the TEA. When conventional reference axes, such as the posterior condylar axis and the anteroposterior axis, are inaccurate, surgeons can refer to this alternative reference. These findings demonstrate that the FPCA may be useful for determining the rotational alignment of the femoral component before and during TKA.