Distal rotational alignment of the Chinese femur and its relevance in total knee arthroplasty

Femoral inherent torsion is more accurate than femoral anteversion angle in evaluating femoral torsion to determine whether combine derotational distal femoral osteotomy or not

BACKGROUND

Previous view is that femoral anteversion angle (FAA) is equivalent to femoral torsion (FT) and as an indication for derotational distal femoral osteotomy (DDFO) combined with medial patellofemoral ligament reconstruction (MPFLR), but posterior femoral condylar deformity affects FAA. Therefore, FAA is not accurate in assessing FT. Whether the femoral inherent torsion (FIT), which avoids the influence of the posterior condyle, can better reflect FT during surgery remains unknown. Meanwhile, the impact of the posterior femoral condyle on surgical outcomes remains unclear.

METHODS

Twenty-five patellar dislocation (PD) patients from 2017 to 2021 were conducted. All patients underwent both preoperative and postoperative computed tomography scans. Categorized by posterior condylar angle (PCA), they were divided into Group A (PCA ≤ 6.4°) and Group B (PCA > 6.4°). Radiographic measurements included FAA, femoral inherent torsion (FIT), patellar tilt angle, congruence angle and tibial tubercle-trochlear groove distance. For clinical outcomes, the Kujula score, Lysholm score, IKDC score to reflect the knee function. The Tegner activity score was used to assess the activity level. The VAS score was used to assess the pain control.

RESULTS

In both groups, the postoperative radiographic outcomes demonstrated a statistically significant improvement. Preoperatively, the FAA was similar in the two groups, but the FIT was greater in the Group A (21.7° ± 1.2° vs 18.4° ± 1 .3°, P < 0.001). However, there was no statistically significant difference between them in the postoperative period (7.4° ± 1.5° vs 7.1° ± 1.8°). In terms of clinical outcomes, both groups demonstrated a significant improvement in the postoperative period. However, the scores of the Group A significantly better (Kujula: 85.7 ± 5.0 vs 79.6 ± 4.8, P = 0.005; Lysholm: 86.8 ± 5.3 vs 80.2 ± 5.7, P = 0.006; IKDC: 86.1 ± 8.8 vs 75.5 ± 7.6, P = 0.004).

CONCLUSION

FIT may be a more reliable indicator than FAA for evaluating FT in PD to determine whether combine DDFO or not, especially in the presence of posterior femoral condylar deformity. Posterior femoral condylar deformity appeared to result in a pseudo-increase in FAA. Simultaneous evaluation of FIT and FAA to identify true posterior condylar deformity offers the potential to prevent enlargement of DDFO and enable precision treatment.

Assessment of average femoral component rotation for balancing functionally aligned total knee replacement in varus deformity: Robotic image guidance study

Introduction and purpose

Ensuring proper femoral component alignment post-Total Knee Arthroplasty (TKA) is crucial for normal patellofemoral (PF) kinematics. However, the customary 3° external rotation relative to the Posterior Condylar Axis (PC Axis) may not universally apply, and the expected final femoral component rotation remains unclear in functionally aligned knees. This study examines the relation between the Transepicondylar Axis (TEA) and PC axis, known as Posterior Condylar Angle (PCA) in Indian patients along with factors influencing PCA, and the feasibility of reproducing patient-specific PCA using image-guided Cuvis joint robot.

Methods

Forty patients (52 Knees) with primary osteoarthritis and varus deformity were prospectively evaluated. Native PCA was determined using CT-based J planner. Pre-operative patellar shape, PF tilt, PF shift, final femoral component rotation (representing post-operative PCA), final patellar tracking, and post-operative functional and radiological assessment at 3 months were recorded.

Results

Study participants averaged 64.3 years of age, with a female-to-male ratio of 23 to 17. Varus deformities varied, with IA2 being most prevalent, and sagittal plane deformities included fixed flexion (34.6 %) and hyperextension (44.2 %). The average PCA was 1.9° (range: 0°-7.3°), with most knees (41 out of 52) below 3°. The majority had Wiberg type 1 patellae, with pre-operative patellar tilt averaging 5.63°, reducing post-operatively to 4.43°. Most patients (37 out of 40) achieved excellent Knee Society functional scores at the 3-month mark. Complications included one case of delayed wound healing and one femoral array pin breakage. Notably, our study revealed a significant deviation in PCA from the commonly reported 3° in Western literature, underscoring the need for region-specific considerations in TKA planning.

Conclusion

PCA of our population is statistically different from customary 3° followed with jig system. Image guided Robotics helps to identify patients specific PCA and reproducing the same was more commonly possible in patients with reducible Varus deformity.

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

BACKGROUND

Poor rotation of the femoral component in total knee arthroplasty (TKA) can result in various postoperative complications, underscoring the critical importance of preoperative planning.

PURPOSE

To 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.

METHODS

A 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.

RESULTS

The 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).

CONCLUSIONS

Using 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.

Robotic arm-assisted unicondylar knee arthroplasty resulted in superior radiological accuracy: a propensity score-matched analysis

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) is an effective surgical treatment for medial compartment arthritis of the knee, yet surgical outcomes are directly related to surgical execution. Robotic arm-assisted surgery aims to address these difficulties by allowing for detailed preoperative planning, real-time intraoperative assessment and haptic-controlled bone removal. This study aimed to compare the clinical and radiological outcomes between conventional manual mobile bearing and robot arm-assisted fixed bearing medial UKA in our local population.

MATERIALS AND METHODS

This is a retrospective case-control study of 148 UKAs performed at an academic institution with a minimum of 1-year follow-up. 74 robotic arm-assisted UKAs were matched to 74 conventional UKAs via propensity score matching. Radiological outcomes included postoperative mechanical axis and individual component alignment. Clinical parameters included a range of motion, Knee Society knee score and functional assessment taken before, 6 and 12 months after the operation.

RESULTS

Robot arm-assisted UKA produced a more neutral component coronal alignment in both femoral component (robotic -0.2 ± 2.8, manual 2.6 ± 2.3; P = 0.043) and tibial component (robotic -0.3 ± 4.0, manual 1.7 ± 5.3; P < 0.001). While the postoperative mechanical axis was comparable, robot arm-assisted UKA demonstrated a smaller posterior tibial slope (robotic 5.7 ± 2.7, manual 8.2 ± 3.3; P = 0.02). Clinical outcomes did not show any statistically significant differences.

CONCLUSION

Compared with conventional UKA, robotic arm-assisted UKA demonstrated improved component alignment and comparable clinical outcomes. Improved radiological accuracy with robotic-arm assistance demonstrated promising early results.

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

BACKGROUND

There 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.

OBJECTIVE

To 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.

METHODS

The 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.

RESULTS

The 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.

CONCLUSION

The 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.

Changes in the femoral varus and rotational profiles are correlated in women with varus osteoarthritic lower limbs

INTRODUCTION

Previous studies have reported the relationship between coronal alignment of the lower limbs and the rotational profile of the femur and tibia. However, the relationship between coronal alignment of the femur and tibia and their rotational profiles in patients with varus osteoarthritic knees is unclear.

METHODS

One hundred women with varus osteoarthritic knees (varus OA group) and 50 women with neutrally aligned lower limbs without osteoarthritis (non-OA group) were evaluated retrospectively. The coronal alignment and rotational profile of the femur and tibia were evaluated, and the correlation between coronal alignment and rotational profile was analyzed, respectively.

RESULTS

The femoral anteversion, posterior condylar angle of the distal femur, and tibial torsion were significantly smaller in the varus OA group than in the non-OA group. In the varus OA group, the femoral anteversion and rotational profile of the distal femur had significantly negative correlations with the degree of femoral varus, while tibial torsion was not related to the degree of tibial varus. In the non-OA group, there was no relationship between coronal alignment and rotational profiles of the femur and tibia in both the varus OA and non-OA groups.

CONCLUSION

Femoral anteversion and the rotational profile of the distal femur were negatively correlated with the degree of femoral varus in Asian women with varus osteoarthritic knees. This study enhanced the understanding of the relationship between changes in coronal alignment of the femur and tibia and their rotational profiles in patients with varus osteoarthritic lower limbs, although this study was limited by the small sample sizes and methodological quality.

Tibial component rotation alters soft tissue balance in a cruciate retaining total knee arthroplasty

Our aim was to understand whether using different landmarks for tibial component rotation influenced articular contact pressures in a balanced total knee arthroplasty (TKA). Twelve patients underwent TKA (Triathlon CR, Stryker Inc., Mahwah, NJ) and contact pressures were assessed using a wireless sensor. Robotic arm assisted TKA using a functional alignment technique was performed, with balanced gaps between medial and lateral compartments. Compartment pressures were measured with the trial tibial component rotated to Akagi's line and to Insall's axis respectively. Rotating the tibial component to Akagi's line resulted in a significantly greater proportion of knees being balanced and lower contact pressures than when the tibial component was rotated to Insall's axis at 10°, 45° and 90° of flexion (p < 0.05). Medial compartment pressures were significantly increased in 10° of flexion, as were lateral compartment pressures in all positions when the tibial component was aligned to Insall's axis (p < 0.05). The mean difference in rotation observed with the two landmarks was 6.9° (range 4.1-9.1°). Rotational alignment of the tibial component using Akagi's line reduced contact pressures, improved balance and reduced the need for soft tissue release when compared with Insall's axis in robotic arm assisted TKA.

Anthropometric Comparison between Indian and Arabian Knees with Respect to Total Knee Replacement

Implants used for total knee replacement (TKR) in most Asian countries are not designed originally for the Asian population, and studies have shown anthropometric differences with respect to TKR among various ethnic groups. For this reason, implants designed for a specific population may not provide an anatomic fit when used in other populations. To avoid the consequences associated with such a misfit, the concept of ethnic-specific implant design is being introduced. In this study, the knee anthropometry of the Indian and Arabian patients was compared. They were operated with implants which were not ethnic-specific designs. Since the consequences associated with implant misfit apply equally to both the Indian and Arabian population, it is essential to compare the knee anthropometry of these two populations. Anthropometric measurements of the distal femur and proximal tibia of the Indian and Arabian knees were obtained intraoperatively using a Vernier caliper. Their respective aspect ratios (ARs) were calculated and statistically compared. It was found that the ARs of both tibia and femur of Indian and Arabian population did not show any statistical difference. There was no statistical difference between Indian and Arabian males (p = 0.345) and between Indian and Arabian females (p = 0.8210). However, a statistical difference in tibial AR (p-value = 0.049) and femoral AR (p-value = 0.003) was found significant when a comparison was made between the knees of Indian males and Indian females in the study. The above results suggested that TKR implants designed anatomically to suit the Indian population can also suit the Arabian population and vice versa. The obtained data can help implant designers to come up with ethnic-specific TKR implants.

The Relationships between the Rotational Axes of the Distal Femur in the Arthritic Caucasian Knee: A Magnetic Resonance Imaging Analysis

Four distal femoral axes have been described to aid in the accuracy of transverse plane component alignment in total knee arthroplasty (TKA). These include the surgical epicondylar axis (SEA), the posterior condylar axis (PCA), and the anteroposterior (AP) axis. Therefore, the primary purpose of this study is to identify the axial femoral relationship with the least variation in a Caucasian population awaiting TKA for osteoarthritis. Secondarily, we further plan to determine if these femoral axis relationships differ with respect to sex or preoperative coronal alignment. These anatomic relationships were measured using preoperative magnetic resonance imaging, which was performed within 2 months of the planned operation date for patient specific instrumentation templating. In terms of our primary outcome, the mean SEA/AP angle was 92.8 degrees (standard deviation [SD]: 2.5 degrees), the mean PCA/AP angle was 95.7 degrees (SD: 2.8 degrees), and the mean PCA/SEA angle was 3.4 degrees (SD: 1.8 degrees). Overall, the PCA/SEA relationship had the smallest variance, while the PCA/AP had the most variance for all comparisons. In terms of our secondary outcome, there was no statistical difference between femoral axis relationships based on preoperative coronal plane alignment. In terms of sex differences, the PCA/SEA was significantly higher in female knees compared with males. Females had a PCA/SEA relationship of 4.7 degrees (SD: 1.3 degrees) compared with 2.6 degrees (SD: 1.2 degrees) for males (p < 0.05). By using the PCA/AP axes, the AP axis was externally rotated by 96.7 degrees (SD: 2.3 degrees) in females, compared with 93.2 degrees (SD: 2.1 degrees) in males, from the PCA. In conclusion, our results demonstrate that the PCA/SEA relationship should be used to determine axial rotation in TKA as it shows the least variation. When using the PCA, approximately 5 degrees of external rotation for Caucasian women and 3 degrees of external rotation for the Caucasian men should be dialed into the femoral cutting block to restore anatomic axial rotation. Further evaluation is needed to determine to role of preoperative coronal alignment on distal femoral axial alignment.

An imaging measurement study of normal knee parameters in southeast China

BACKGROUND

Imaging measurement of distal femur and proximal tibia has been the hot point in the research of total knee arthroplasty and prosthesis development, which is an important treatment for patients with advanced knee joint disease. This study retrospectively investigated the digital imaging measurement of normal knee parameters in southeast China and evaluated their clinical value.

METHODS

From February 2010 to May 2014, and in accordance with the inclusion criteria, a total of 677 knees (334 female knees and 343 male knees) were categorized into 3 age groups. Clinical and digital imaging data, including the distal femoral condyle diameter (FCD), tibial plateau diameter (TPD), the distance between the medial tibial plateau and fibular head (DPF), tibiofemoral valgus angle, distal femoral valgus angle, proximal tibia (PT) varus angle and the angle from femoral condyle to tibial perpendicular (FT), were measured by using AutoCAD 10.0 software. All measured variables were statistically analyzed by SPSS statistical software (version 18.0).

RESULTS

Data are presented as the mean ± standard deviation. The normal female and male femoral condyle diameter was (7.69 ± 0.46) cm and (8.68 ± 0.55) cm, while the normal female and male tibial plateau diameter was (7.66 ± 0.46) cm and (8.60 ± 0.55) cm, respectively. The normal female and male DPF was (0.76 ± 0.36) cm and (0.79 ± 0.36) cm. For females and males, the tibiofemoral valgus angle and distal femoral valgus angle were (3.89 ± 2.20) ° and (3.29 ± 2.12) °, (9.03 ± 2.18) ° and (8.25 ± 2.20) °. As the two methods to measure tibial plateau varus angle, PT angle of normal female and male was (4.29 ± 1.86) ° and (4.84 ± 2.23) °, while the normal female and male FT angle was (5.34 ± 1.95) ° and (5.52 ± 2.07) °. Based on the data obtained, we found significant differences between the two genders in terms of the femoral condyle diameter and tibial plateau diameter in all age groups (P < 0.01). The DPF parameter showed an obvious difference between the young group and the middle-aged group (P < 0.05), and no significant difference was observed between the sides and genders (P > 0.05). The distal femoral valgus angle showed statistical differences between genders in the left side of the young group and middle-aged group (P < 0.05), while angle PT and FT showed no significant difference (P > 0.05).

CONCLUSION

A large number of knee measurements was obtained, and a local knee database was developed in this study. Imaging measurement prior to total knee arthroplasty is clinically important for increasing the accuracy and long-term efficacy of total knee arthroplasty. These data can also provide useful information for knee surgery and sports medicine as well as prosthesis development.

Analysis of Gender Differences in the Rotational Alignment of the Distal Femur in Kinematically Aligned and Mechanically Aligned Total Knee Arthroplasty

To compare the angle between the external rotation references of the femoral components in the axial plane by gender and lower limb alignment in Korean patients with osteoarthritis (OA). Magnetic resonance (MR) images of 1273 patients were imported into a modeling software and segmented to develop three-dimensional femoral bony and cartilaginous models. The surgical transepicondylar axis (sTEA), posterior condylar axis (PCA), the kinematically aligned axis (KAA), and anteroposterior axis were used as rotational references in the axial plane for mechanically aligned (MA) TKA. The relationship among axes were investigated. Among 1273 patients, 942 were female and 331 were male. According to lower limb alignment, the varus and valgus knee groups comprised 848 and 425 patients, respectively. All measurements, except PCA-sTEA, differed significantly between men and women; all measurements, except PCA-sTEA, did not differ significantly between the varus and valgus knee groups. In elderly Korean patients with OA, rotational alignment of the distal femur showed gender differences, but no differences were seen according to lower limb alignment. The concern for malrotation of femoral components during kinematically aligned TKA is less in Koreans than in Caucasians and relatively less in women than in men. In MA TKA, malrotation of the femoral components can be avoided by setting different rotational alignments for the genders.

To Predict the Length of Hospital Stay After Total Knee Arthroplasty in an Orthopedic Center in China: The Use of Machine Learning Algorithms

Background and Objectives: Total knee arthroplasty (TKA) is widely performed to improve mobility and quality of life for symptomatic knee osteoarthritis patients. The accurate prediction of patients' length of hospital stay (LOS) can help clinicians for rehabilitation decision-making and bed assignment planning, which thus makes full use of medical resources.

Methods: Clinical characteristics were retrospectively collected from 1,298 patients who received TKA. A total of 36 variables were included to develop predictive models for LOS by multiple machine learning (ML) algorithms. The models were evaluated by the receiver operating characteristic (ROC) curve for predictive performance and decision curve analysis (DCA) for clinical values. A feature selection approach was used to identify optimal predictive factors.

Results: The areas under the ROC curve (AUCs) of the nine models ranged from 0.710 to 0.766. All the ML-based models performed better than models using conventional statistical methods in both ROC curves and decision curves. The random forest classifier (RFC) model with 10 variables introduced was identified as the best predictive model. The feature selection indicated the top five predictors: tourniquet time, distal femoral osteotomy thickness, osteoporosis, tibia component size, and post-operative values of Hb within 24 h.

Conclusions: By analyzing clinical characteristics, it is feasible to develop ML-based models for the preoperative prediction of LOS for patients who received TKA, and the RFC model performed the best.

Medio-Lateral and Flexion-Extension Gap Imbalances in Mechanically Aligned Total Knee Arthroplasty Using Measured Resection Technique in Korean Patients: 3D Simulation

Background: It is well known that the measured resection (MR) technique in mechanically aligned (MA) total knee arthroplasty (TKA) generates significant gap imbalances, but little is known about whether this applies to the knees of Asian patients. The aim of this study was to evaluate the medio-lateral and flexion-extension gap imbalances and to find the most optimal posterior femoral condyle resection method for operating on the knees of Asian patients. Methods: In total, 738 magnetic resonance imaging (MRI) scans of consecutive patients who underwent TKA were obtained. Four posterior femoral condylar resection methods were used: alignment by the surgical transepicondylar axis (TEA), Whiteside’s line (WSL), 3° external rotation to the posterior condylar axis (PCA), and flexion-extension axis (FEA). Results: For the medial compartments, there were significant differences between the flexion and extension gaps in the varus knee group in all four methods, but there were no differences between the flexion and extension gaps in the valgus knee group. For the lateral compartment, all the methods showed significant differences except for WSL of the valgus knee group and FEA of the varus knee group. Conclusions: In Asian patients, the use of the MA MR technique inevitably leads to medio-lateral or flexion-extension imbalances. Therefore, surgeons should consider which methods can minimize imbalances and choose the best method within the technically possible range.

Evaluating distal femoral torsion and posterior condylar line reliability for adjusting femoral component rotation in TKA, Egyptian population radiographic study

BACKGROUND

Femoral component rotational alignment is critical for successful TKA. The primary study objective is to measure the preoperative distal femoral torsion (DFT) of an Egyptian patient's cohort using a seated posteroanterior (PA) knee radiograph. The secondary objectives are to check the intraoperative reliability of using the posterior condylar line (PCL) as a reference for rotation and to measure postoperative component rotation using the same radiographic technique.

METHODS

100 arthritic knees, 22 males, 78 females, 95 Varus and five valgus. A long anteroposterior radiograph [Hip to knee to ankle (HKA)] for coronal alignment assessment, and the anatomical posterior condylar angle (aPCA) between the anatomical transepicondylar axis (aTEA) and the PCL was measured in the seated PA knee radiographs for evaluating the DFT and component rotation. Intraoperative rotation was adjusted to 3° external rotation to the PCL.

RESULTS

HKA improved from a preoperative mean 170.4° ± 6.2 to a postoperative mean 178.3° ± 1.5 (p < 0.005). DFT was internal in all knees; the mean aPCA was -4.5 ± 2.4 (0° to -9°), femoral component rotation significantly changed to a mean aPCA of -3.6 ± 2.3 (0° to -7°) (p = 0.005). Acceptable intraoperative patellar tracking in 94%, and patellar subluxation needed a lateral retinacular release in 2% (two valgus knees). The preoperative DFT was not affected by sex or direction of coronal deformity; more external DFT noticed in severe varus deformity.

CONCLUSIONS

All keens had an internal DFT not affected by sex, or coronal deformity direction. Using PCL as a guide to adjust femoral component rotation is a valid technique in our population.

Gender differences exist in rotational anatomy of the distal femur in osteoarthritic knees using MRI

PURPOSE

Optimal rotational alignment of the femoral component is essential for total knee arthroplasty (TKA). The femoral transepicondylar axis (TEA), Whiteside's line (WSL), and posterior condylar axis (PCA) are various intra-operative references that can be used to determine femoral rotation, and each has advantages and disadvantages. This study aimed to define the rotational anatomy of the distal femur and investigate its relationship with gender in osteoarthritic knees.

METHODS

Magnetic resonance imaging (MRI) was obtained from 1522 patients (1298 females and 224 males) with end-stage knee osteoarthritis prior to TKA. MRI was constructed into three-dimensional models. The angles between the TEA and WSL, WSL and PCA, and TEA and PCA were calculated for each patient. In addition, gender differences in femoral rotation were evaluated.

RESULTS

The PCA was 2.2° ± 1.0° internally rotated relative to the TEA. WSL was 1.2° ± 2.8° externally rotated relative to the TEA. The WSL to TEA relationship exhibited greater variability than the PCA to TEA relationship. PCA was more internally rotated and WSL was more externally rotated relative to TEA in female group than male group. Based on the standard reference rules of 3° external rotation from the PCA that has been conventionally used, 15.7% of patients showed external rotation lower 1° or greater than 5° external rotation from the PCA. In the mean external rotation of the TEA from the PCA (2.2°) from this population; however, the percentage of patients showing ± 2° from their TEA dropped to 5.1% of patients.

CONCLUSION

Gender difference and variability exist in distal femoral rotational anatomy. These data can be useful in consideration of femoral anatomy variability and gender difference. The same cutting angle may lead to malrotation of the femoral component.

LEVEL OF EVIDENCE

Consecutive patients, level III.

Editorial Commentary: Revision Anterior Cruciate Ligament Surgery, Unlike Cheese, Is Not Improved With Age but Nationality and Culture May Matter

Recurrent instability and future joint damage occur if there is a repeated anterior cruciate ligament injury after reconstruction. This prognostic declaration is said to those who have sustained a rupture to the repaired anterior cruciate ligament. Both younger and older patients seek stable knees to allow a return to stability and twisting activity without the risk of added joint damage. To achieve this goal, revision ligament surgery is needed.

Conservative treatment using a sponge cast for transfer fractures in nursing home patients

Background

Transfer fractures in the lower limbs of bedridden and chair-bound nursing home patients can result from trauma induced by the usual lifting, moving, turning, or transferring maneuvers. Treatment entails immobilization for pain control and position change; however, splints/hard casts increase the risk of pressure sores. Therefore, we evaluated the use of a sponge cast.

Materials and methods

Between March 2011 and October 2017, 17 patients with a lower limb transfer fracture due to transferring maneuvers in a nursing home were recruited. We evaluated the improvement in pseudo-motion and divided the patients as having bony union, fibrous union, or remaining pseudo-motion. We also investigated the occurrence of pressure sores due to immobilization up until the final follow-up.

Results

Femur fractures occurred in 15 patients and lower leg fractures in two. Six of the 15 femur fractures were periprosthetic (four hip arthroplasty and two knee arthroplasty). Pseudo-motion was improved in 15 of 17 cases, within an average of 17.3 weeks for the improvement (14–23 weeks; bony union: 11 cases and fibrous union: four cases). Pseudo-motion remained in two cases: one periprosthetic fracture around the knee arthroplasty and the other, a femur neck fracture. No pressure sores occurred.

Conclusions

A sponge cast appears to be one of the effective treatment options available for bedridden or chair-bound patients with a lower limb fracture due to its low risk of complications and satisfactory clinical results.

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Wider femoral and mediolaterally narrower tibial components are required for total knee arthroplasty in Turkish patients

PURPOSE

To evaluate the knee morphologic parameters in the Turkish population, compare them with known data, and identify new morphologic parameters.

METHODS

Magnetic resonance (MR) images of 1000 healthy subjects aged 18-50 years were included. One orthopedic surgeon and one experienced musculoskeletal radiologist reviewed MR images and measured 22 morphologic parameters. Sex and side differences were evaluated. Correlations between age and measurement parameters were assessed. The measured parameters were compared with known data. Femoral and tibial condylar height differences were identified.

RESULTS

A strong correlation was found among regarding all measurement parameters (p = 0.000 and k > 0.985 for all measurements) by both observers. A significant difference between the female and male subjects regarding the measurement parameters (p = 0.000) was found, except for the tibial coronal slope, posterior condylar angle (PCA), medial and lateral tibial slopes (MTS and LTS), and medial plateau depth. No measurement parameter was significantly correlated with age (n.s.). The femur surface ratio in male and female subjects was 1.29 ± 1.04 and 1.28 ± 1.12, respectively (n.s.). The tibial plateau aspect ratio was 61.4 ± 1.09 in males and 59.8 ± 1.57 in females (p = 0.004). The mean medial and lateral femoral condylar cartilage and bone height differences were 3.3 ± 1.1 and 3.1 ± 0.9 mm, respectively. The mean medial and lateral tibial condylar cartilage and bone height differences were 2.3 ± 0.3 and 1.6 ± 0.1 mm, respectively.

CONCLUSION

Compared to current designs, wider femoral and mediolaterally narrower tibial components are needed to provide well-fitting prosthesis and improve functional outcomes, especially in women. The data on femoral and tibial condylar height differences will be useful for future research on component design. In the clinical practice, the components developed based on these findings will have a substantial effect on postoperative outcomes and patient satisfaction.

LEVEL OF EVIDENCE

II.

Distal femoral torsion: Differences between caucasians and asians. A multicentre computed tomography study of 515 distal femurs

BACKGROUND

The posterior condylar angle (PCA) is formed by the posterior condylar line (PCL) and the clinical (or anatomic) transepicondylar line (TEL). The primary objective of this study was to compare the distribution of PCA values in Caucasians and Asians free of knee osteoarthritis. The secondary objectives were to assess PCA variability according to age, gender, and side.

HYPOTHESIS

PCA values differ between Caucasians and Asians.

METHODS

The study included the computed tomography scans of 515 healthy femurs, 259 from Asians in China and 256 from Caucasians in France. PCA values were determined based on four landmarks, namely, the two femoral epicondyles and the most prominent point of each condyle at the posterior aspect of the knee. The Mann-Whitney test was chosen to compare PCA values according to ethnic group, gender, and side and Spearman's correlation coefficient to assess correlations with age. Inter-observer and intra-observer variability of PCA measurements was assessed.

RESULTS

Mean PCA was 6.0°±2.5° (range, 0°-14°) overall, 6.4° (range, 0.31°-14.1°) in the Asians, and 5.5° (range, 0°-13.1°) in the Caucasians (p<0.0001). Chinese femurs are significantly more internally rotated. No differences in PCA values were found according to age (p=0.4307), gender (p=0.7113), or side (p=0.4304). Inter-observer and intra-observer variability was limited for each of the landmarks, indicating that PCA measurement was reliable.

CONCLUSION

PCA varies not only across individuals as reported previously, but also across ethnic groups. This finding further supports routine PCA measurement on imaging studies before total knee arthroplasty.

LEVEL OF EVIDENCE

III, comparative retrospective study.

Comparison of patellar tracking according to different angles of external rotation of femoral component in varus knee of Asians

PURPOSE

Racial difference in the femoral geometry may exist. Asian femurs may be more externally rotated. If anatomical differences in distal femur had existed between Caucasians and Asians, the group with 5° external rotation of the femoral component should have shown better results than the group with 3° external rotation of the femoral component have.

METHODS

598 patients underwent total knee arthroplasty in our institution, among whom 83 patients (115 knees) who had postoperative computed tomography (CT) were studied retrospectively. Sixty-two knees were set in 5° of external rotation of femoral component relative to the posterior condylar axis (group A) while the others (53 knees) were set in 3° (group B). The femoral component rotation (FCR) was measured and compared using CT. The patellar tilting (PT) and the lateral patellar displacement (LPD) were measured to evaluate the patellar tracking using Merchant view. And postoperative clinical scores were compared.

RESULTS

The mean FCRs showed no significant difference between two groups ( p > 0.05). The mean PT and LPD showed no statistically significant difference either ( p > 0.05). There were no statistical differences in clinical scores.

CONCLUSION

The difference in the patellar tracking between the two groups could not be demonstrated. There were no statistical differences in clinical scores either. We concluded there is no need to adhere to 5° external rotation.

Reliability evaluation of inter-eminence line, Akagi and Dalury lines for intraoperative tibial rotation: An osteology-based study

BACKGROUND

This large osteology study examined the reliability, reproducibility and correlation between previously described tibial tray rotation alignment lines (including Akagi and Dalury lines). In addition, it described a novel inter-eminence line utilising the tibial plateau inter-condylar eminences as a landmark.

METHODS

A total of 214 post-medieval (18-19th centuries) skeletal tibia were examined. The inter/intra-observer variation and correlation between reference lines were measured.

RESULTS

Inter-observer reproducibility was excellent and there were no differences between Akagi, Dalury, and inter-eminence lines. Similarly, intra-observer reliability was excellent for Akagi, Dalury, and inter-eminence lines. Qualitative review of tibial inter-condylar eminences suggested that these could be easily identifiable. When taking the medial angle from a medial-lateral reference line, the Akagi line showed a mean of 96.90° (±10.27), inter-eminence line 94.52° (±12.84), and Dalury line 88.06° (±11.75). The angle produced by the Dalury line was significantly different from both the Akagi and inter-eminence lines (P≤0.001). The Akagi line and inter-eminence line showed a strong correlation (r=0.74). The Dalury line showed a weaker correlation with both the Akagi line (r=0.69) and inter-eminence line (r=0.40).

CONCLUSION

This study suggested that tibial rotation lines showed excellent intra/inter-observer reliability and reproducibility. The novel and easily drawn inter-eminence line showed strong correlation with the Akagi line and could be used for tibial tray rotational alignment in total knee arthroplasty.

Variation in tibial tuberosity lateralization and distance from the tibiofemoral joint line: An anatomic study

BACKGROUND

To describe variation in tibial tuberosity position in a normal adult population and inter-rater reliability of measurements of tibial tuberosity position.

METHODS

Surface models of 161 proximal tibia specimens (83 female, 78 male; 80 black, 81 white; age 28.7years, SD 7.5) were created with a three-dimensional laser scanner. Percent lateralization, tuberosity-eminence angle, and distance from joint surface were measured for each specimen. Variation in tuberosity position by sex, race, age, height, and BMI was calculated. Multivariate regression was used to assess for demographic factors independently associated with tuberosity positioning.

RESULTS

Mean percent lateralization was 57.9% (SD 2.4, range 52.4-64.9%). Tuberosity-eminence angle mean was 11.03° (SD 2.8, range 0-18.7°). Percent lateralization and tuberosity-eminence angle were not influenced by sex, race, age, height or, BMI (p>0.05). Mean tuberosity distance from joint surface was 29.2mm (SD 3.5, range 16.6-38.6mm) and larger in males than females (30.7mm (SD 2.9), 27.6mm (SD 3.3); p<0.001). Tuberosity distance from joint surface increased 0.18mm on average per 1.0cm increase in height (p<0.001). Inter-rater reliability was high for distance from joint surface (Cronbach alpha=0.99) and percent lateralization.

CONCLUSIONS

Tibial tuberosity percent lateralization falls in a narrow range for individuals, whereas tuberosity-eminence angle and distance from joint line are more variable. Inter-rater reliability is high for percent lateralization and distance for the joint surface. Distance of tibial tuberosity from joint surface is associated with sex and height.

Distal Femoral Rotation Correlates With Proximal Tibial Joint Line Obliquity: A Consideration for Kinematic Total Knee Arthroplasty

BACKGROUND

We hypothesized that there is a correlation between the distal femoral rotation and proximal tibial joint line obliquity in nonarthritic knees. This has significance for kinematic knee arthroplasty, in which the target knee alignment desired approximates the knee before disease.

METHODS

Fifty computed tomography scans of nonarthritic knees were evaluated using three-dimensional image processing software. Four distal femoral rotational axes were determined in the axial plane: the transepicondylar axis (TEA), transcondylar axis (TCA), posterior condylar axis (PCA), and a line perpendicular to Whiteside's anterior-posterior axis. Then, angles were measured relative to the TEA. Tibial joint line obliquity was measured as the angle between the proximal tibial plane and a line perpendicular to the axis of the tibia.

RESULTS

There was a strong positive correlation between PCA-TEA and tibial joint line obliquity (r = 0.68, P < .001) as well as TCA-TEA and tibial joint line obliquity (r = 0.69, P < .001). In addition, the tibial joint line obliquity and TCA-TEA angles were similar, 3.7° ± 2.2° (mean ± standard deviation) and 3.5° ± 1.7°, respectively (mean difference, 0.2° ± 0.2°; P = .369).

CONCLUSION

Both PCA-TEA and TCA-TEA strongly correlated with proximal tibial joint line obliquity indicating a relationship between distal femoral rotational geometry and proximal tibial inclination. These findings could imply that the native knee in flexion attempts to balance the collateral ligaments toward a rectangular flexion space. A higher tibial varus inclination is matched with a more internally rotated distal femur relative to the TEA.

Morphologic features of the distal femur and tibia plateau in Southeastern Chinese population: A cross-sectional study

Morphologic measurements of the femoral and tibial features of western population have been done in several studies, which provides the fundamental data for the design of total knee arthroplasty prosthesis used globally, including China. However, researches on anatomic and morphologic features of the knee in Chinese populations of both sexes have never been conducted. Our study was aimed at investigating the anatomic and morphologic features of the knees of the Southeastern Chinese population by magnetic resonance imaging (MRI) scans, so as to provide parameters for sex- and ethnic-specific implant designs in the future.A total of 245 knees from 244 Chinese adults (130 females and 114 males, aging from 18 to 89 years) who received knee MRI scan from November 2014 to October 2015 were recruited and analyzed. A set of linear and angular parameters, and 6 normalized ratios were measured and calculated on the distal femur and proximal tibia.The knee size was significantly different between sexes. Compared with women, men have larger (P < .01) medial-lateral (ML) and anterior-posterior (AP) dimensions in both distal femur and proximal tibia. Differences in femoral shape, represented by the femur surface ratio, between both sexes were also identified (1.23 ± 0.07 vs 1.27 ± 0.07, P < .01), whereas the ML/AP ratios of the tibia are similar between both sexes (1.44 ± 0.07 vs 1.44 ± 0.09, P = .97). We also found substantial difference in the morphology of femur and tibia plateau in Southeastern Chinese population compared with data obtained from western populations.Our study measured the anatomic and morphologic features of the knees in Southeastern Chinese population, and identified knee morphologic differences between both sexes, as well as western and Chinese population. Further clinical studies are needed to determine other essential parameters for the design of prosthesis to the Chinese populations.

Geometric morphometric analysis reveals age-related differences in the distal femur of Europeans

Background

Few studies have looked into age-related variations in femur shape. We hypothesized that three-dimensional (3D) geometric morphometric analysis of the distal femur would reveal age-related differences. The purpose of this study was to show that differences in distal femur shape related to age could be identified, visualized, and quantified using three-dimensional (3D) geometric morphometric analysis.

Methods

Geometric morphometric analysis was carried out on CT scans of the distal femur of 256 subjects living in the south of France. Ten landmarks were defined on 3D reconstructions of the distal femur. Both traditional metric and geometric morphometric analyses were carried out on these bone reconstructions. These analyses were used to identify trends in bone shape in various age-based subgroups (<40, 40–60, >60).

Results

Only the average bone shape of the < 40-year subgroup was statistically different from that of the other two groups. When the population was divided into two subgroups using 40 years of age as a threshold, the subject's age was correctly assigned 80% of the time.

Discussion

Age-related differences are present in this bone segment. This reliable, accurate method could be used for virtual autopsy and to perform diachronic and interethnic comparisons. Moreover, this study provides updated morphometric data for a modern population in the south of France.

Conclusion

Manufacturers of knee replacement implants will have to adapt their prosthesis models as the population evolves over time.

Three-dimensional geometric morphometric analysis reveals ethnic dimorphism in the shape of the femur

Background

Ethnic dimorphism in the distal femur has never been studied in a three-dimensional analysis focused on shape instead of size. Yet, this dimorphism has direct implications in orthopedic surgery and in anthropology. The goal of this study was to show that differences in distal femur shape related to ethnic dimorphism could be identified, visualized, and quantified using 3D geometric morphometric analysis.

Methods

CT scans of the distal femur were taken from 482 patients who were free of any bone-related pathology: 240 patients were European (E) and 242 were Asian (A). Ten osteometric landmarks based on standard bone landmarks used in anthropometry were placed on these scans. Geometric morphometric analysis, principal component analysis (PCA), canonical variates analysis (CVA), and other discriminant analyses (Goodall’s F-test and Mahalanobis distance) were performed. A cross-validation analysis was carried out to determine the percentage of cases in which the ethnicity was correctly estimated.

Results

The shape of the E and A distal femur differed significantly (Goodall’s F = 94.43, P < 0.001 and Mahalanobis D2 distance = 1.85, P < 0.001). PCA identified a difference in distal femur shape between A and E. The CVA revealed that correct ethnicity was assigned in 82% of cases and the cross-validation revealed a 75% rate of correct ethnic group estimation.

Conclusion

The distal femur exhibits ethnic dimorphism. 3D geometric morphometric analysis made it possible to demonstrate these differences. The large number of subjects studied has helped modernize the references for certain bone measurements, with direct implication for orthopedic surgery and anthropology.

An assessment of femoral rotational alignment of mini-incision total knee arthroplasty: A comparison based on the transepicondylar line from the kneeling view and the intraoperative posterior condylar line

BACKGROUND

Rotational alignment of the distal femur is important in total knee arthroplasty. The purpose of this study is to use a roentgenographic technique to evaluate the accuracy of mini-incision total knee arthroplasty (MIS TKA) performed based on the transepicondylar line from the kneeling view.

METHODS

Totally 32 patients (aged from 64 to 80 years with an average of 70.9 years) with 46 cases of knee osteoarthritis received MIS TKA were registered. Before surgery, the condylar twist angle was measured from the kneeling view. The bone cut for the external rotation was completed, with regard to the condylar twist angle. The control group including 26 patients (aged from 50 to 89 years with an average of 69.7 years) with 42 cases of knee osteoarthritis underwent TKA with built-in cutting jig design 3 degrees of femoral external rotation. This study is a prospective continuous-time duration analysis study. The level of evidence is IIc.

RESULTS

The mean condylar twist angle was 5.1° in the experimental group and 5.4° in the control group. The mean postoperative angle between the clinical epicondylar axis and the posterior condylar line of the femoral component was 0.46°. The same postoperative angle of the built-in external rotation in the control group was 2.7°. The condylar twist angle was significantly more accurate than the built-in design.

CONCLUSION

Our result substantiates that the kneeling view is practicable and reproducible as the cutting reference for femoral external rotation. The accuracy of the kneeling view shows that the epicondylar axis can be used in smaller wound surgery, such as MIS TKA.

LEVEL OF EVIDENCE

Level IIc.

What Differences in Morphologic Features of the Knee Exist Among Patients of Various Races? A Systematic Review

BACKGROUND

Most TKA prostheses are designed based on the anatomy of white patients. Individual studies have identified key anthropometric differences between the knees of the white population and other major ethnic groups, yet there is limited understanding of what these findings may indicate if analyzed collectively.

QUESTION/PURPOSE

What are the differences in morphologic features of the distal femur and proximal tibia among and within various ethnicities?

METHODS

A systematic review of the PubMed database and a hand-search of article bibliographies identified 235 potentially eligible English-language studies. Studies were excluded if they did not include morphology results or had insufficient data for analysis, were unrelated to the distal femur or proximal tibia, were conducted in pediatric patients or those undergoing unicondylar knee arthroplasty, or bone surface measurements were obtained for trauma products. This left 30 eligible studies (9050 knees). Study quality was assessed and reported as good, fair, or poor according to the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Morphometric data for the distal femur and proximal tibia were available for four ethnic groups: East Asian (23 studies; 5543 knees), white (11 studies; 3111 knees), Indian (three studies; 283 knees), and black (three studies; 113 knees). Although relatively underrepresented, the knees from the Indian and black studies were maintained for hypothesis-generating purposes and to highlight crucial gaps in the data. The two key dimensions for selecting a suitable implant based on a patient's unique anatomy-AP length and mediolateral (ML) width-were assessed for the femur and tibia, in addition to aspect ratio, calculated by dividing the ML width by the AP length. Study measurement techniques were compared visually when possible to ensure that each pooled study conducted a similar measurement process. Any significant measurement outliers were reviewed for eligibility to determine if the measurement techniques and landmarks used were comparable to the other studies included.

RESULTS

White patients had larger femoral AP measurements than East Asians (62 mm, [95% CI, 57-66 mm] vs 59 mm, [95% CI, 54-63 mm]; mean difference, 3 mm; p < 0.001), a smaller femoral aspect ratio than East Asians (1.20, [95% CI, 1.11-1.29] vs 1.25, [95% CI, 1.16-1.34]; mean difference, 0.05; p = 0.001), and a larger tibial aspect ratio than black patients (1.55, [95% CI, 1.40-1.71] vs 1.49, [95% CI, 1.33-1.64]; mean difference, 0.06; p = 0.005).

CONCLUSIONS

This analysis uncovered differences of size (AP height and ML width of the femur and tibia) and shape (tibial and femoral aspect ratios) among knees from white, East Asian, and black populations. Future research is needed to understand the clinical implications of these discrepancies and to provide additional data with underrepresented groups.

Anthropometric measurements of tibial plateau and correlation with the current tibial implants

PURPOSE

The aim of the study was to make an anthropometric analysis at the resected surfaces of the proximal tibia in the Turkish population and to compare the data with the dimensions of tibial components in current use. We hypothesized that tibial components currently available on the market do not fulfil the requirements of this population and a new tibial component design may be required, especially for female patients with small stature.

METHODS

Anthropometric data from the proximal tibia of 226 knees in 226 Turkish subjects were measured using magnetic resonance imaging. We measured the mediolateral, middle anteroposterior, medial and lateral anteroposterior dimensions and the aspect ratio of the resected proximal tibial surface. All morphological data were compared with the dimensions of five contemporary tibial implants, including asymmetric and symmetric design types.

RESULTS

The dimensions of the tibial plateau of Turkish knees demonstrated significant differences according to gender (P < 0.05). Among the different tibial implants reviewed, neither asymmetric nor symmetric designs exhibited a perfect conformity to proximal tibial morphology in size and shape. The vast majority of tibial implants involved in this study tend to overhang anteroposteriorly, and a statistically significant number of women (21 %, P < 0.05) had tibial anteroposterior diameters smaller than the smallest available tibial component.

CONCLUSION

Tibial components designed according to anthropometric measurements of Western populations do not perfectly meet the requirements of Turkish population. These data could provide the basis for designing the optimal and smaller tibial component for this population, especially for women, is required for best fit.

LEVEL OF EVIDENCE

II.

Reference axes for optimal femoral rotational alignment in varus osteoarthritic Indian knees - A CT based study

BACKGROUND

Optimal rotational alignment of femoral component is important for longevity and success of total knee replacement. Whiteside line (WL), posterior condylar axis (PCA) and femoral transepicondylar axis are various intra-operative landmarks to guide femoral rotation. Each of these has its pros and cons. The aims of our study were to assess the relationship of posterior condylar axis and the antero-posterior axis of femur with the surgical epicondylar axis and evaluate whether degree of deformity or severity of osteoarthritis alters the rotational alignment of the femur when posterior condylar axis is taken as a reference. Are we justified in using a 3° external rotation with respect to posterior condylar axis in each knee?

METHODS

The study is a single-centre, CT-based, cross-sectional, radiological study in 56 bilateral osteoarthritic varus Indian knees. The following were deduced using a uniform standardised method: Whiteside-surgical transepicondylar angle and posterior condylar angle. The study population was subdivided based on age, sex, deformity and grade of osteoarthritis.

RESULTS

The mean posterior condylar angle (N = 112) was 3.25 ± 1.379° (95% CI). The posterior condylar angle ranged from '0' degrees to '6' degrees with only 27.7% having an angle of 3°. The mean Whiteside-transepicondylar angle (N = 112) is 89.72 ± 3.537° (95% CI).

CONCLUSIONS

PCA and the WL are comparable in establishing the rotational alignment of the femoral component with respect to the surgical transepicondylar axis. A fixed, 3° external rotation with respect to the PCA is an oversimplification and rotational alignment of the knees should be individualised.

Rotational landmarks of the distal femur in Indian population: A MRI-based study

Background

Femoral rotational landmarks may vary according to the population. Our aim is to find out the relationship of the landmarks used in total knee arthroplasty in an Indian population and compare it with reported landmarks in other ethnic populations.

Materials and methods

We retrospectively reviewed MR images of 124 knees in 124 patients to determine the relationship of bony landmarks by measuring the condylar twist angle (CTA), Whiteside-posterior condylar angle (W-PC), and Whiteside-epicondylar angle (W-EP). The difference between the genders and the sides was analyzed.

Results

The mean CTA, W-EP and W-PC were 5.92°, 88.99° and 94.09° respectively. The mean CTA, W-EP and W-PC in males were 5.77°, 89.16° and 94.22° and they were 6.24°, 88.61° and 93.82° in females. On the left side, the CTA, W-EP and W-PC were 5.90°, 89.37° and 94.45° while they were 5.93°, 88.65° and 93.73° on the right side. There was no statistically significant difference between the genders or the sides.

Conclusion

The CTA was around 6° in our study, and the posterior condylar angle (PCA) would be 3° as the difference between them is 3°. Hence, we conclude that the conventional jigs used in the measured resection technique using 3° external rotation in reference to the posterior condyles are still an appropriate option in normal and varus knees. And there is no difference between Indians and Caucasians, but there was a significant difference with Chinese populations. Although determining rotation based on the posterior condylar axis is more practical, it is prudent to combine it with other methods.

Distal femoral rotational alignment in the Indian population - An important consideration in total knee arthroplasty

OBJECTIVE

To measure the angular relationships of distal femoral rotational axes in the normal Indian population.

MATERIALS AND METHODS

Magnetic Resonance Imaging (MRI) scans of the knee of 40 Indian subjects were used to define the posterior condylar axis, the transepicondylar axis and the Whiteside's line (anteroposterior axis). The posterior condylar angle (PCA) - the angle between the posterior condylar axis and the transepicondylar axis, and the Whiteside-epicondylar angle (W-EP angle) were then calculated.

RESULTS

The mean posterior condylar angle in the Indian knee was 4.67° and the mean Whiteside-epicondylar angle was 92.7°.

CONCLUSION

There are differences in the distal femoral rotational axes among various races. The mean PCA and the W-EP angle are more externally rotated in the Indian than in the Western, population, but similar to the Chinese. Using fixed values to define the angular relationships between the axes could lead to malrotation of the femoral component. An understanding of the racial differences is essential while designing implants for the Indian population.

Rotational assessment of distal femur and its relevance in total knee arthroplasty: analysis by magnetic resonance imaging

Objective

To define the distal femur rotation pattern in a Brazilian population, correlating such pattern with the one suggested by the arthroplasty instruments, and analyzing the variability of each anatomic parameter.

Materials and Methods

A series of 101 magnetic resonance imaging studies were evaluated in the period between April and June 2012. The epidemiological data collection was performed with the aid of the institution’s computed imaging system, and the sample included 52 male and 49 female patients. The measurements were made in the axial plane, with subsequent correlation and triangulation with the other plans. The posterior condylar line was used as a reference for angle measurements. Subsequently, the anatomical and surgical transepicondylar axes and the anteroposterior trochlear line were specified. The angles between the reference line and the studied lines were calculated with the aid of the institution’s software.

Results

The mean angle between the anatomical transepicondylar axis and the posterior condylar line was found to be 6.89°, ranging from 0.25° to 12°. For the surgical transepicondylar axis, the mean value was 2.89°, ranging from –2.23° (internal rotation) to 7.86°, and for the axis perpendicular to the anteroposterior trochlear line, the mean value was 4.77°, ranging from –2.09° to 12.2°.

Conclusion

The anatomical transepicondylar angle showed mean values corresponding to the measurement observed in the Caucasian population. The utilized instruments are appropriate, but no anatomical parameter proved to be steady enough to be used in isolation.

Anthropometric difference of the knee on MRI according to gender and age groups

The purpose of this study was to analyze the anthropometric data from MRI images that were obtained from the non-arthritic knees in Asian adults, and to identify the existence of morphologic differences between age groups. This cross-sectional study included knee MR images of 535 patients (273 males, 262 females) taken for the evaluation of soft-tissue injuries, excluding cases with cartilage defect and malalignment. The age, gender, height, and BMI were also assessed. The patients were grouped into three different 20-year age groups (20-39, 40-59, and 60-79). The MRI analysis was performed on the anthropometric parameters of distal femur and posterior tibial slope. Age-related differences were found in femoral width, distance from the distal and posterior cartilage surface to the medial/lateral epicondyle, medial posterior condylar offset (PCO), and posterior condylar angle (PCA) (all P < 0.001), but not in lateral PCO, and medial/lateral tibial slopes. In the analysis of covariance analyses, significant interaction between gender and age groups was found in most parameters, but not in PCA, distance from the posterior cartilage surface to the medial epicondyle, or medial tibial slope. We found anthropometric differences among age groups exist in most of distal femoral parameters, but not in posterior tibial slope. The results of this study can be used by manufacturers to modify prostheses to be suitable for the future Asian elderly population.

Variability of the location of the tibial tubercle affects the rotational alignment of the tibial component in kinematically aligned total knee arthroplasty

PURPOSE

Our experience with computer plans of kinematically aligned total knee arthroplasty showed that the anteroposterior (AP) axis of the tibial component when viewed in an axial plane did not consistently intersect either the medial border or the medial 1/3 of the tibial tubercle. The purposes were (1) to determine the variability in the mediolateral location of the tibial tubercle with respect to the medial tibia on the magnetic resonance image (MRI) of the knee and (2) to determine whether the AP axis of the kinematically aligned tibial component intersects either the medial border or the medial 1/3 of the tibial tubercle.

METHODS

One hundred and fifteen knees in 111 consecutive subjects treated with total knee arthroplasty were studied. The mediolateral location of the tibial tubercle was measured from a magnetic resonance image (MRI) of the knee. The distances between the AP axis of the tibial component and the medial border of the tibial tubercle and between the AP axis and the medial 1/3 of the tibial tubercle were measured from a computer plan of the reconstructed knee.

RESULTS

On the MRI, the medial border of the tibial tubercle varied 15 mm from the medial border of the tibia. On the computer plan, the AP axis of the tibial component in an axial view of the tibia did not intersect either the medial border (p < 0.0001) or the medial 1/3 of the tibial tubercle (p < 0.0001). In 70 and 86 % of knees, the mediolateral distance of the AP axis of the tibial component was 2 mm or greater from the medial border of the tibial tubercle and the medial 1/3 of the tibial tubercle, respectively, which causes a clinically meaningful error in rotation of 5° or more.

CONCLUSIONS

Because the mediolateral location of the tibial tubercle varies, the medial border and medial 1/3 of the tibial tubercle are not reliable landmarks when the goal is to kinematically align the rotation of the tibial component on the tibia.

LEVEL OF EVIDENCE

IV.

Distal femur rotation relates to joint obliquity in ACL-deficient Chinese

BACKGROUND

The lower limb osteometry of Chinese differs from that of whites. The joint line of the knee in the coronal plane in Chinese is more medially inclined and the posterior condylar angle of the distal femur in the axial plane is larger. However, it is unclear whether there is any direct association between the coronal plane and axial plane osteometry.

QUESTIONS/PURPOSES

We asked whether the joint line obliquity of the knee is related to the posterior condylar angle of the distal femur in young Chinese subjects.

METHODS

Ninety-nine young Chinese patients with anterior cruciate ligament injuries were recruited. The lower limb alignment and joint line obliquity were measured using standing long radiographs of the whole lower limb. The rotational alignment of the distal femur was assessed in the axial cuts of the MRI.

RESULTS

The distal femur rotational alignment was associated with the obliquity of the knee in Chinese. The posterior condylar angle was 5° ± 2°. The knee was 5° ± 3° medially inclined.

CONCLUSIONS

The joint line of the knee in a group of young Chinese patients was more medially inclined than that of whites. The posterior condylar angle of the distal femur was larger. The presence of an association between distal femur rotational alignment and joint line obliquity in this group of young Chinese patients suggests a possible developmental cause explaining the difference in osteometry between races.

Clinical comparison of valgus and varus deformities in primary total knee arthroplasty following midvastus approach

The purpose of this retrospective study was to compare clinical parameters in preoperative, perioperative, and postoperative categories between valgus and varus deformities in primary total knee arthroplasty (TKA) following midvastus approach. We compared 83 patients (83 TKAs in valgus) with 949 patients (1084 TKAs in varus), with a mean follow-up of 72 months. In valgus deformity, mean age and body mass index at TKA were younger and smaller with more percentage of patellar subluxation. Cutting thickness from distal femur, tibial plateau, and lateral aspect of posterior femur were significantly different. The incidence of lateral release was 10.8% in valgus and 2.1% in varus. Although several significant differences were observed in preoperative and perioperative categories, the postoperative functional results were similarly evaluated by Knee Society knee and function scores.

Gender differences in distal femoral morphology and the role of gender specific implants in total knee replacement: a prospective clinical study

Gender differences in distal femoral morphology may affect femoral component fit using a standard range of prostheses. The clinical relevance of this is controversial. Standardised measurements were taken from the distal femora of 50 males and 50 females during total knee replacement (TKR). Corresponding measurements were taken from the respective gender specific and standard femoral components. No demographic differences were noted. Significant differences in both frequency and magnitude existed in the medial-lateral femoral component overhang between the sexes. In females, standard implants overhung at the anterior flange width (AFW) by >2mm in 24/50 (48%) and by >3mm in 17/50 (34%) (p<0.001). Also at the anterior medial-lateral width (MLA) 29/50 (58%) overhung by >2mm and 24/50 (48%) by >3mm (p<0.001). In males, standard implants overhung by >2mm in 1/50 (2%). In females, gender specific implants overhung by >2mm in 3/50 (6%). Females had a mean aspect ratio of 1.02 (0.82 to 1.35) and men 0.98 (0.79 to 1.19). Femoral component overhang can occur in females undergoing TKR and a gender specific implant would reduce the potential for medial-lateral overhang. Long term studies are awaited to quantify the clinical implications of overhang.

Three-dimensional morphology of the knee reveals ethnic differences

BACKGROUND

Studies have demonstrated sex differences in femoral shape and quadriceps angle raising a question of whether implant design should be sex-specific. Much of this research has addressed shape differences within the Caucasian population and little is known about differences among ethnic groups.

QUESTIONS/PURPOSES

We therefore asked: Do shape differences in the distal femur and proximal tibia exist among different ethnic groups and between the sexes in each ethnic population? And if ethnic differences exist, do they have a clinical impact on current TKA design?

SUBJECTS AND METHODS

We analyzed 1000 normal adult knees (80 African American, 80 East Asian, and 860 Caucasian). Three-dimensional surface models were created for each bone and added to three-dimensional statistical bone atlases. Statistical shape analysis was conducted with a process combining principal components and multiple discriminate analyses. Eleven femoral and nine tibial measurements were calculated.

RESULTS

We found differences in mean measurements between the sexes and ethnicities. Males had larger knees, with a mean 5-mm-larger anteroposterior dimension than females in all ethnicities. African American females had a 7.4-mm-deeper patellar groove, 2.3-mm-smaller tibial mediolateral dimension, and 2.5-mm-larger tibial anteroposterior dimension than Caucasian females. African American males had a 4.3-mm-larger femoral anteroposterior dimension, 10.1-mm-larger tibial mediolateral dimension, and 6-mm-larger tibial anteroposterior dimension than Asian males.

CONCLUSIONS

We identified differences in three-dimensional knee morphology among Caucasian, African American, and East Asian populations. Clinical studies will be required to determine whether these differences are important for implant design.

The anterior trochlear line as a reference for femoral component positioning in total knee arthroplasty

PURPOSE

A new radiographic method using the anterior and posterior femoral condyles as a landmark to determine the rotational alignment of the femoral component in TKA had been developed.

METHODS

The new radiograph presents an axial view of the distal femur. The patients were asked to lie in the supine position and flex the knee approximately 120° to 130°. Radiographs were applied at an inclination angle of 20° to 30°. The condylar twist angle (CTA), the external rotational angle between the posterior condylar (PC) line and the clinical transepicondylar axis (TEA), and the trochlear line angle (TLA), and the internal rotational angle between the anterior trochlear line and the clinical TEA were measured. Images were taken of 129 knees in 87 patients with osteoarthritis of the knee. The measurement values obtained using our method with those obtained using 3D reconstructed images from a 3-dimensional helical CT system (n = 35) were compared.

RESULTS

The average CTA was 5.7° ± 2.8° and the average TLA was -5.6° ± 3.2°. The CTA was negatively correlated with the tibiofemoral angle (TFA). The average TLA was positively correlated with the TFA. The average difference between the TLA values obtained with this view and those obtained using the 3D-CT was 0.5° ± 1.6°. The relationship between the radiograph and 3D-CT in TLA was higher than that in CTA.

CONCLUSIONS

This radiographic technique allows easy and simultaneous measurement of the CTA and TLA and may provide an alternative method for assessing the TEA of the femur during preoperative planning for TKA.

Differences of knee anthropometry between Chinese and white men and women

Whether there are differences in knee anthropometry between Asian and white knees remains unclear. Three-dimensional knee models were constructed using computed tomography or magnetic resonance imaging of healthy Chinese and white subjects. The morphologic measurements of the femur included mediolateral, anteroposterior dimensions, and aspect ratio. The tibial measurements included mediolateral, medial/lateral anteroposterior dimension, aspect ratio, and posterior slope of medial/lateral plateau. The results showed that Chinese knees were generally smaller than white knees. In addition, the femoral aspect ratio of Chinese females was significantly smaller than that of white females (1.24 ± 0.04 vs 1.28 ± 0.06). Tibial aspect ratio differences between Chinese and white males (1.82 ± 0.07 vs 1.75 ± 0.11), though significant, were likely a reflection of differences in knee size between races. These racial differences should be considered in the design of total knee arthroplasty prosthesis for Asian population.

Distal femoral rotational axes in Indian knees

PURPOSE

To measure the angular relationships of distal femoral rotational axes in 100 normal Indian knees.

METHODS

42 men and 8 women aged 26 to 40 (mean, 31) years, with 100 normal non-arthritic knees were recruited. Anatomic landmarks were measured using computed tomography. They included the posterior condylar axis, the transepicondylar axis, the anteroposterior axis (Whiteside's line), the posterior condylar angle (PCA), the Whiteside-epicondylar angle (W-EP), and the Whiteside-posterior condylar angle (W-PC).

RESULTS

The mean PCA, W-EP, and W-PC were 5, 90.8, and 95.8 degrees, respectively. The mean femorotibial alignment was 179.6 degrees. The differences between the left and right sides were significant only for the WEP and W-PC. Only the PCA and W-EP were weakly correlated (r=0.338, p=0.001).

CONCLUSION

There are differences in distal femoral rotational axes among Indian, Caucasian, and Japanese knees. Our data can be used to evaluate changes in those axes in ageing or arthritic patients.

Interobserver and intraobserver error in distal femur transepicondylar axis measurement with computed tomography

On 2 separate occasions at least 1 week apart, 6 independent observers studied errors in identification of the transepicondylar axis (TEA) using computed tomography in 10 cadaveric knees. The reference surgical TEA was established by dissection of specimens. We found an average error of 2.6 degrees (external rotation) when the TEA was identified by computed tomography. The error was significantly smaller when the TEA was identified by using a conventional axial image than when a 3-dimensional reconstruction image was used (P < .001, paired t test). No significant intraobserver error (P = .814, Wilcoxon rank test) was found when the measurement was performed using conventional 2-dimensional computed tomography images. However, significant interobserver difference was evident (P < .001, Friedman test).

Inter- and intra-observer errors in identifying the transepicondylar axis and Whiteside's line

PURPOSE

To assess inter- and intra-observer errors in identifying the transepicondylar axis and Whiteside's line in a cadaveric model mimicking total knee arthroplasty.

METHODS

Four cadaveric knees with intact soft tissues were used. The knees were exposed anteriorly using the Insall approach, with the patella everted laterally. Three observers (2 surgeons and one trainee) took turns to identify the anatomic landmarks of the transepicondylar axis and Whiteside's line. Each observer repeated the process 20 times. Each identification was photographed and referenced with the true values obtained from the knees after they were stripped of all soft tissue. Inter- and intra-observer errors in the anatomic landmarks were compared.

RESULTS

Inter-observer error was significant with both the transepicondylar axis and Whiteside's line (p<0.001, one-way ANOVA). The intra-observer variation was greater for Whiteside's line than the transepicondylar axis (standard deviation, 4.2 vs 2.5 degrees). The maximum potential errors in the transepicondylar axis and Whiteside's line were 13 degrees and 24 degrees, respectively.

CONCLUSION

The accuracy of rotational alignment of the transepicondylar axis and Whiteside's line were operator-dependent, and their intra-operative reproducibility was low.

The John Insall Award: gender-specific total knee replacement: prospectively collected clinical outcomes

Gender-specific total knee replacement design is a recent and debated topic. We determined the survivorship and clinical outcomes of a large primary total knee arthroplasty cohort, specifically assessing any differences between gender groups. A consecutive cohort of 3817 patients with 5279 primary total knee replacements (3100 female, 2179 male) with a minimum of 2 years followup were evaluated. Preoperative, latest, and change in clinical outcome scores (WOMAC, SF-12, KSCRS) were compared. While men had higher raw scores preoperatively, women had greater improvement in all WOMAC domains including pain (29.87 versus 27.3), joint stiffness (26.78 versus 24.26), function (27.21 versus 23.09), and total scores (28.35 versus 25.09). There were no gender differences in improvements of the SF-12 physical scores. Men had greater improvement in Knee Society function (22.1 versus 18.63) and total scores (70.01 versus 65.42), but not the Knee Society knee score (47.83 versus 46.64). Revision rates were 10.2% for men and 8% for women. Women demonstrated greater implant survivorship, greater improvement in WOMAC scores, equal improvements in SF-12 scores, and less improvement in only the Knee Society function and total scores. The data refute the hypothesis of inferior clinical outcome for women following total knee arthroplasty when using standard components.

LEVEL OF EVIDENCE

Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Anatomical assessment of the vastus medialis oblique muscle in patients with osteoarthritis of the knee

Minimally invasive total knee arthroplasty requires subluxation of patella laterally without eversion. The anatomy of the vastus medialis oblique muscle (VMO), which affects the surgical exposure of minimally invasive total knee arthroplasty, was investigated. There was no significant difference between men and women with respect to any parameter. The average fiber angle relative to the rectus femoris muscle was 52.9 degrees on anteroposterior view and 49.7 degrees on lateral view. The average insertion height and the distal portion of VMO belly were 17.3% and 38.4% of the patella length from the upper pole of patella, respectively. Female patients had lower VMO attachment and VMO belly, and a significant sex difference was demonstrated. All patients had attachments beneath the upper pole of the patella.

What patient and surgical factors contribute to implant wear and osteolysis in total joint arthroplasty?

Total joint arthroplasty has been a successful operation for decades. Our current patients are younger and more active than those in the past. They place higher demands on themselves and have expectations commensurate with their lifestyles. Time-limited longevity with the large number of anticipated total joint replacement procedures and their potential burden to health care is a growing concern. In the past two decades, implant wear and osteolysis have been identified as major causes for the failure of otherwise well-functioning implants. Osteolysis can be divided into several categories: patient-specific, implant-specific, and the result of surgical factors. Although these categories are interrelated and not mutually exclusive, they enable us to build a framework in which to further advance our understanding of osteolysis and apply this information in a clinically relevant manner.

Coronal bowing of the femur and tibia in Chinese: its incidence and effects on total knee arthroplasty planning

PURPOSES

To study the incidence of femoral or tibial bowing in the coronal plane in a Chinese population, and how it affects the accuracy of bone cuts for total knee replacement when an intramedullary alignment system is used.

METHODS

Standing radiographs of the entire lower limb of each patient with end-stage primary osteoarthritis of the knee were analysed. All radiographs were digitised and the extent of bowing in the coronal plane measured. A bowing was marked if an angulation was more than 2 degrees. The projected error of cutting was then calculated.

RESULTS

Of 93 lower limbs, 58 (62%) of the femurs had marked bowing in the coronal plane; 41 (44%) had a mean lateral bowing of 5.3 (standard deviation [SD], 3.2) degrees; 17 (18%) had a mean medial bowing of 4.4 (SD, 1.9) degrees. Marked tibial bowing in the coronal plane was less common (30 tibias, 32%). If a cutting error of more than 2 degrees was considered unacceptable, significantly more unacceptable cuts would ensue in the groups with marked bowing (p=0.003 for femurs and p<0.001 for tibia, respectively).

CONCLUSION

The incidence of femoral or tibial bowing in the coronal plane was high in a Chinese population with end-stage osteoarthritis of the knee. This phenomenon may increase bone cut errors in total knee replacement if an intramedullary alignment system is used and the extent of bowing is not recognised.