Application of a machine learning and optimization method to predict patellofemoral instability risk factors in children and adolescents.

PURPOSE: Conservative treatment remains the standard approach for first-time patellar dislocations. While risk factors for patellofemoral instability, a common paediatric injury, are well-established in adults, data concerning the progression of paediatric recurrent patellar dislocation remain scarce. A reproducible method was developed to quantitatively assess the patellofemoral morphology and anatomic risk factors in paediatric patients using magnetic resonance imaging (MRI) and machine learning analysis. METHODS: Data were analyzed from a retrospective review (2005-2022) of paediatric patients diagnosed with acute lateral patellar dislocation (54 patients) who underwent MRI and were compared with an age-based control group (54 patients). Patellofemoral, tibial, tibiofemoral and patellar height parameters were measured. Differences between groups were analyzed with respect to MRI parameters. The potential diagnostic utility of the parameters was assessed via machine learning and genetic algorithm analyses. RESULTS: Significant differences were observed between the two groups in six patellofemoral morphological parameters. Regarding patellar height morphological parameters, all methods exhibited significant between-group differences. Among the tibia and tibiofemoral morphological parameters, only the tibial tubercle-trochlear groove distance exhibited significant differences between the two groups. No sex-related differences were present. Significant variations were observed in patellar height parameters, particularly in the Koshino-Sugimoto (KS) index, which had the highest area under the curve (AUC: 0.87). Using genetic algorithms and logistic regression, our model excelled with seven key independent variables. CONCLUSION: KS index and Wiberg index had the strongest association with lateral patellar dislocation. An optimized logistic regression model achieved an AUC of 0.934. Such performance is considered clinically relevant, indicating the model's effectiveness for the intended application. LEVEL OF EVIDENCE: Level Ⅲ.

Reliability and modality analysis of patellar height measurement in pediatric knee.

Introduction: Various measurement methods and imaging technique are in use to measure patellar height in pediatric patients. However, there is no gold standard as to which measurement method and modality are the most reliable for pediatric patients. Therefore, the aim of this study was to determine the inter-observer reliability, intra-observer reliability, and applicability of various patellar height measurement methods in pediatric knee. Additionaly, we analyzed the reliability across different imaging modalities. Methods: Total 450 pediatric patients (age: 5-18 years) were evaluated using lateral knee radiographs and magnetic resonance imaging (MRI). The patellar height ratios were measured using five methods. Five methods were Insall-Salvati (IS), Koshino-Sugimoto (KS), Blackburne-Peel (BP), modified Insall-Salvati (MIS), and Caton-Deschamps (CD). The patients were categorized into two age groups: P (ages 5-13) and Q (ages 14-18). Each measurement was conducted twice by two raters. The intra-observer reliability, inter-observer reliability and inter-modality reliability were calculated. In addition, applicability was defined as the possibility to apply each measurement method to each age group. Results: The KS method showed the highest inter-observer reliability and intra-observer reliability when using MRI for both age groups. The inter-observer reliability and intra-observer reliability of the IS for lateral knee radiographs was highest among all observers for group Q. The CD method showed the highest inter-observer reliability in group P, while the KS showed the highest intra-observer reliability in group P using lateral radiographs. The KS method showed the highest inter-modality reliability in group P, while the IS showed the highest inter-modality reliability in group Q. The KS method was applicable to all patients when using lateral knee radiography, and the IS method was applicable to all patients when using MRI. Conclusions: Our results show that the reliability of various measurement method and imaging technique differed based on pediatric knee age group when measuring patellar height. Therefore, in the case of pediatric patients, reliability measurement methods and imaging techniques according to the patient's age should be applied.

Spontaneous Deltoid Tear in Cuff Tear Arthropathy and Its Effect on the Outcome of Reverse Total Shoulder Arthroplasty: A Comparison Using Propensity Score Matching.

Background: Deltoid function critically influences the results of reverse total shoulder arthroplasty (RTSA), and spontaneous deltoid attrition tears are frequently detected in cuff tear arthropathy (CTA) patients; however, the clinical impacts of these tears on RTSA outcomes are undetermined. Our aim was to determine the effect of spontaneous deltoid attrition tears on postoperative outcomes after RTSA without an additional deltoid procedure. Methods: Seventy-two patients who underwent RTSA for CTA with preoperative magnetic resonance imaging (MRI) and a minimum clinical follow-up of 1 year (mean, 32 months) were retrospectively reviewed in the study. Patients with a history of previous shoulder surgery or injury were excluded. The presence and location of deltoid attrition tears were determined in preoperative MRI. Propensity score matching (1:1) was performed to construct tear and no-tear groups. Finally, 21 patients, matched with respect to age, sex, hand dominance, symptom duration, medical comorbidity (obesity, diabetes mellitus, and coronary artery disease), Hamada grade, and implant type, were assigned to each group. Clinical outcomes (functional scores, isometric power, and range of motion) in the two groups were compared. Results: Deltoid attrition tears were detected in 21 of the 72 enrolled cases (29.1%). Anterolateral deltoid was the most frequent location and no tear was detected in the posterior deltoid. The tear rate increased with disease severity (Hamada G2, 4.8%; G3, 23.8%; > G4, 71.4%). No pre- or postoperative clinical variables differed significantly between the tear and no tear groups. Conclusions: Deltoid attrition tears were detected in 29% of CTA patients who underwent RTSA. The most common site was the anterolateral region and tear prevalence tended to increase with CTA progression. However, RTSA was found to provide satisfactory outcomes regardless of the presence of a deltoid attrition tear.

Evaluation of age group and sex differences in the measurement of patellar height of pediatric knee in a Korean population.

Introduction: Various methods based on bony landmarks are used to determine patellar height. This study analyzed five methods for patellar height measurement on lateral knee radiographs, namely, the Insall-Salvati, Koshino-Sugimoto, Blackburne-Peel, modified Insall-Salvati, and Caton-Deschamps methods. Methods: Overall, 425 pediatric participants (221 males, 204 females; age range 5-18 years) were included and were divided equally into three age groups (A, 5-10 years; B, 11-13 years; and C, 13-18 years). For the comparison of the applicability of each method, the applicable probabilities for each age group and sex-based differences were analyzed using logistic regression techniques. Intra-rater reliability and inter-rater variability were analyzed by two trained raters. Results: The Koshino-Sugimoto method was applicable to all patients. The 80% applicable age of female patients was lower than that of male patients for the Blackburne-Peel (male = 11.9, female = 11) and Caton-Deschamps (male = 11.9, female = 11.1) methods. However, in the Insall-Salvati (male = 12, female = 12.1) and modified Insall-Salvati (male = 12.6, female = 13.1) methods, the 80% applicable age in male patients was lower than that in female patients. The Koshino-Sugimoto method showed the highest variability in group B, while the Insall-Salvati showed the highest variability in group C. In terms of intra-observer reliability, the Caton-Deschamps method showed the same reliability as the Insall-Salvati method, in group C. Conclusions: Our results demonstrated differences in the reliability, variability, and applicability of patellar height measurement methods according to age group. The applicability of patellar height measurement methods also differed according to sex. Therefore, based on age group and sex, different methods should be used for patellar height measurement in pediatric patients.

Existence of Gender-Based Difference in Morphology of Convex Lateral Tibial Plateau in Korean Population Primary Knee Joint Osteoarthritis.

PURPOSE: Morphological differences in the knee joints of females and males have been reported in a previous study. These differences have realized the need of developing a gender-specific prosthesis. However, anatomical studies on gender-based differences in the proximal tibial plateau's sagittal curvature have rarely been conducted. Therefore, this study is aimed at evaluating the geometry of the sagittal curvature of the proximal tibial plateau in the Korean population. METHODS: Three-dimensional data for the sagittal curvature of the tibial plateau morphology from 1976 patients (i.e., 299 male and 1677 female) were assessed using magnetic resonance imaging. The sagittal profiles of the tibial plateaus were also evaluated. The independent t-test and paired t-test were used for statistical analysis. RESULTS: The proximal tibia had concave and convex surfaces in the medial and lateral plateaus, respectively, for both genders. In addition, the medial diameter of the tibial plateau was significantly greater than the lateral diameter for both genders. Gender-based difference was not found in the medial diameter of the tibial plateau but was observed in the lateral diameter. CONCLUSION: These results may provide guidelines for a suitable knee implant design for the Korean patients. The incorporation of this shape information in the medial and lateral sides in the prosthetics for a total knee arthroplasty and a lateral unicompartmental knee arthroplasty can improve knee range motion.

Correlation of Femoral Trochlear Dysplasia With Anterior Cruciate Ligament Injury in Skeletally Immature Patients.

BACKGROUND: Reports of anterior cruciate ligament (ACL) injury in patients with skeletal immaturity have been increasing. Variations in knee joint anatomy have been linked to ACL injury risk factors. PURPOSE: To identify associations between ACL injury, patella alta, and femoral trochlear dysplasia in patients with skeletal immaturity by using magnetic resonance imaging (MRI). STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: This retrospective study included 231 patients with skeletal immaturity-116 with acute complete noncontact ACL injury and 115 without ACL injury (controls)-who underwent knee MRI. Cases of femoral trochlear dysplasia were divided into 4 types according to the Dejour classification scheme. Patellar height and patellar tendon length were measured via sagittal MRI, and the Insall-Salvati ratio (ISR) was calculated. RESULTS: In the ACL injury group, 56 (48.3%) knees exhibited trochlear dysplasia, including 51 (91.1%) that were Dejour type A; and in the control group, 12 (10.4%) knees exhibited trochlear dysplasia, 12 (100%) Dejour type A. The prevalence of femoral trochlear dysplasia was significantly higher in the ACL injury group than in the control group (P < .001). The ISR was not significantly different between the ACL injury and control groups (0.9 ± 0.2 vs 1 ± 0.2 mm; P = .16). The correlation between ISR >1.2 and presence of ACL injury was not significant. CONCLUSION: Femoral trochlear dysplasia was associated with ACL injury in patients with skeletal immaturity. In particular, Dejour type A femoral trochlear dysplasia was correlated with ACL injury patients with skeletal immaturity. Also, the possibility of ACL damage exists in patients with skeletal immaturity and femoral trochlear dysplasia.

Gender-Based Quantitative Analysis of the Grand Piano Sign in Mechanically Aligned Total Knee Arthroplasty in Asians.

In mechanically aligned (MA) total knee arthroplasty (TKA), the grand piano sign helps surgeons to further ensure the proper external rotation of the femoral component. The goal of this study was to determine the sex-related differences in the shape of the anterior resection surface using 3D magnetic resonance imaging (MRI) models. MRI scans were performed on 267 consecutive patients (202 women and 65 men) with osteoarthritis who underwent TKA in order to reconstruct a 3D model. Virtual anterior condylar resection was performed based on the surgical transepicondylar axis (sTEA), Whiteside's line (WSL), and flexion-extension axis (FEA). On the anterior resection surface, both lateral length (LatL) and medial length (MedL) were measured, and the ratio between the two (MedL/LatL) was calculated. The mediolateral width of the distal femur (ML) and anterior resection surface (M'L') were measured, and the ratio between the M'L' and ML (M'L'/ML) was calculated. Both the lateral deviation (LD) and the ratio between LD and ML (LD/ML) were also determined. Morphological classification of the anterior resection surface was conducted based on the presence of a definite medial peak. When based on the sTEA or WSL, the MedL/LatL of female subjects was significantly greater than that of male subjects (p < 0.001 and p < 0.05, respectively). The MedL/LatL of the FEA was consistently larger than that obtained using the sTEA or WSL. Among female subjects, the MedL/LatL of the sTEA was significantly greater than that of the WSL, although this was not the case in either the total study population or the male subjects alone. When based on the sTEA, the M'L'/ML was statistically greater in the female subjects (p < 0.01). The LD was greater in the male subjects (p < 0.01), but there was no difference between the male and female subjects when comparing the LD/ML (p = 0.93). The proportion of double- and single-peak types was not significantly different between the sexes (p = 0.196). Surgeons should be aware that the shape of the anterior resection surface may differ depending on the sex of the patient. The results of this study provide more consistent surgical outcomes as well as fundamental anatomical data for designing suitable prostheses applicable to the Korean population.

Anatomic Differences in the Sagittal Knee Joint Are Associated With ACL Injury: Results From a Skeletally Immature Korean Population.

BACKGROUND: Differences in tibiofemoral articular morphology are associated with risks of anterior cruciate ligament (ACL) injury. PURPOSE: To determine whether bony and cartilaginous morphological characteristics are related to ACL injury in pediatric patients and to investigate any differences according to sex. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 200 skeletally immature Korean patients from a single institution were included in this study; 100 patients had an ACL injury, and 100 had an intact ACL. Condylar morphology and tibial slopes were evaluated and compared between the groups, and differences between sexes were evaluated in the ACL-injured group. RESULTS: The lateral femoral curvature was significantly greater and the lateral and medial tibial curvatures were significantly smaller in the ACL-injured group than in the intact group (P < .01 for all). In addition, the lateral and medial femoral curvatures as well as the lateral tibial curvature were significantly smaller in female than in male patients (P < .01 for all). Both the medial and lateral tibial slopes were greater in the ACL-injured versus intact group (medial slope, 5.5° vs 5.0°; lateral slope, 3.0° vs 1.3°, respectively); this difference was statistically significant for lateral tibial slope (P = .026). No sex-based differences were found for medial or lateral tibial slope. CONCLUSION: Femoral and tibial curvatures as well as lateral tibial slope were significantly different between the ACL-injured and ACL-intact patients, and the lateral tibial curvature was significantly smaller in female than in male patients. Medial and lateral tibial slopes were not associated with a significant difference in ACL injury between male and female patients.

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.

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

BACKGROUND: Although 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. METHODS: A 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. RESULTS: The 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. CONCLUSIONS: The 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.

Effect of the presence of the articular cartilage on the femoral component rotation in total knee arthroplasty in female and varus osteoarthritis knees.

PURPOSE: Surgical techniques for total knee arthroplasty (TKA) require femoral rotational corrections that alter the position of the surface of the posterior femoral joint especially in kinematic alignment. However, preoperative planning of TKA based on computed tomography (CT), without knowing the femoral cartilage thickness, may cause post-surgery failures in femoral rotation. Therefore, this study aimed to evaluate the effects of posterior condyle cartilage thickness on rotational alignment in the femoral component. METHODS: Three-dimensional magnetic resonance imaging (MRI) scans were obtained for 139 male and 531 female osteoarthritis patients. The angles defined by the femoral posterior condylar axis (PCA) and the surgical transepicondylar axis (TEA) were evaluated with respect to the presence of cartilage. Additionally, these effects were evaluated with respect to patient gender and varus/valgus condition. RESULTS: In all patients, the angle between the TEA and PCA was significantly greater in the presence of cartilage than in the absence of cartilage. This result was also seen in female patients. However, there was no difference in the TEA/PCA angle in male patients based on the presence of cartilage. The TEA/PCA angle was significantly greater in the presence of cartilage than in the absence of cartilage in the female varus group. However, there were no differences in the TEA/PCA angle based on the presence of cartilage in the male varus/valgus and female valgus groups. Cartilage thickness in the posterior femoral condyle was significantly greater on the lateral side than on the medial side in all and male patients. However, there was no difference between the genders regarding cartilage thickness. CONCLUSION: Surgical planning for TKA based on CT does not consider articular cartilage and could lead to external malrotation of the femoral implant. Therefore, the effect of the remaining posterior condylar cartilage should be considered by surgeons to prevent over-rotation of the femoral component, especially in female varus knees.

Femoral trochlear morphology is associated with anterior cruciate ligament injury in skeletally immature patients.

PURPOSE: Knee joint morphology is a known contributor to anterior cruciate ligament (ACL) injury, and the shape of the distal femur condyle is one of the associated factors. However, the relationship between femoral trochlear morphology and ACL injury is unclear, especially in pediatric patients. Therefore, the present study aimed to evaluate the effect of femoral trochlear morphology on ACL injury in pediatric patients and investigate the possibility of gender differences. METHODS: In total, 116 skeletally immature children aged 3-18 years with primary ACL injuries were matched with a control group of 116 skeletally immature children. Lateral trochlear inclination, trochlear facet asymmetry, trochlear depth, and sulcus angle were evaluated using magnetic resonance imaging (MRI). Differences between patient groups and gender were investigated. Receiver-operating characteristic (ROC) curves were constructed to obtain the sensitivity and specificity of all parameters. RESULTS: A significant difference was observed in the sulcus angle and trochlear inclination between the ACL injury and control groups (p < 0.05). No significant difference was observed between the ACL injury and control groups with respect to the anatomic patellar instability risk factors. All parameters showed an area under the curve of 0.6 in the ROC analysis, indicative of failure of the diagnostic test. CONCLUSIONS: There was a significant association between femoral trochlear morphology and increased risk of ACL injury in pediatric patients. No gender difference was found except in the trochlear depth. It was showed that the difference in trochlear morphology should be considered between normal children and pediatric patients with ACL injury to increase the awareness regarding ACL injuries. LEVEL OF EVIDENCE: III.

Long Head of the Biceps Tendon Tenotomy versus Subpectoral Tenodesis in Rotator Cuff Repair.

BACKGROUD: Lesions of the long head of the biceps tendon (LHBT) are one of the most common pathologies in patients with a rotator cuff tear. Although various procedures have been shown to be effective for treating LHBT lesions during rotator cuff repair, no consensus has been reached regarding the most effective treatment. The purpose of this study was to compare the outcomes of tenotomy vs subpectoral tenodesis of the LHBT in arthroscopic rotator cuff repair. METHODS: The records of 135 patients who underwent arthroscopic rotator cuff repair with biceps tenotomy or subpectoral tenodesis for a partial LHBT tear of > 50% were initially reviewed. Finally, 77 patients (38 patients with tenotomy and 39 patients with subpectoral tenodesis) with an intact rotator cuff, who underwent a functional evaluation at 1 year postoperatively, were enrolled in this retrospective study. RESULTS: The average follow-up was 13.3 ± 4.36 months (13.2 ± 1.4 months in the tenotomy group and 13.6 ± 2.7 months in the subpectoral tenodesis group; p = 0.416). Demographic and surgical data were not significantly different between the 2 groups. Preoperatively, biceps groove tenderness, Speed's test, and Yergason test results were positive in 27.3%, 27.3%, and 10.4% of the study subjects, respectively. Compared with preoperative values, all functional scores including shoulder muscle power were significantly improved postoperatively, and no significant intergroup difference was observed (all p > 0.05). A visible Popeye deformity was not encountered in either group at the final follow-up. Eight patients in the tenotomy group and 7 patients in the subpectoral tenodesis group complained of mild anterior shoulder pain (p = 0.731), and 4 patients in each group complained of groove tenderness (p = 0.969). No surgical or postoperative complication occurred in either group. CONCLUSIONS: Both biceps tenotomy and subpectoral tenodesis performed during rotator cuff repair improved pain and function and resulted in comparable clinical outcomes. Residual symptoms associated with the remnant LHBT in the groove may not be a problem after adhesion of LHBT.

Effects of a Thermosensitive Antiadhesive Agent on Single-Row Arthroscopic Rotator Cuff Repair.

BACKGROUND: Postoperative stiffness after rotator cuff repair is a common complication that can lead to poor outcomes and patient discomfort. The application of an antiadhesive agent at the time of repair recently became an option for clinicians, but little information is available on its effects. PURPOSE: To evaluate and compare retear rates, the incidence of postoperative stiffness, and the clinical outcomes of patients who underwent cuff repair with or without the application of an antiadhesive agent. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Among 296 patients who underwent arthroscopic rotator cuff repair surgery, we compared the outcomes of those injected with a thermosensitive gel antiadhesive agent into the subacromial space (112 cases) versus noninjected controls (184 cases). Retear rates in the 2 groups were determined by magnetic resonance imaging at 1 year after surgery. Shoulder joint range of motion and functional scores were evaluated serially. RESULTS: The rate of retear was significantly lower in the injection group (20/112 cases; 17.9%) than the control group (53/184 cases; 28.8%) (P = .034). Postoperative stiffness was not significantly different between the 2 groups (P = .710). Among the data regarding range of motion, only forward flexion at 6 months after surgery showed superior results in the injection group. Functional scores showed conflicting results: The control group had better visual analog scale scores for pain (injection vs control: 2.17 vs 1.68 at 6 months; 1.82 vs 1.28 at 12 months), American Shoulder and Elbow Surgeons scores (79.89 vs 89.64 at 12 months), and simple shoulder test scores (8.70 vs 10.06 at 12 months), whereas the injection group had better Constant-Murley scores (injection vs control: 59.49 vs 55.60 at 3 months; 77.35 vs 71.98 at 6 months; 87.28 vs 81.56 at 12 months). CONCLUSION: The tendon healing rate was significantly higher in the group receiving an antiadhesive agent than in the control group. No intergroup difference was seen in the occurrence of postoperative stiffness. However, the pain-related functional score showed inferior results in the injection group at 12 months. The biological action of antiadhesive agents in rotator cuff repair should be further evaluated.

Evaluation of tibial rotational axis in total knee arthroplasty using magnetic resonance imaging.

Surgeon-dependent factors such as optimal implant alignment of the tibial component are thought to play a significant role in the outcome following primary total knee arthroplasty (TKA). In addition, tibial component malrotation is associated with pain, stiffness, and altered patellofemoral kinematics in TKA. However, measuring tibial component rotation after TKA is difficult. Therefore, the purpose of this study was to find a reliable method for positioning the tibial component in TKA. To investigate the morphology of the tibial plateau, 977 patients' knees (829 females and 148 males) were evaluated using MRI. The relationships between the femoral transepicondylar axis (TEA), Akagi line, posterior tibial margin (PTM), medial third of the tibial tubercle (MTT), and anatomical tibial axis (ATS) were investigated in this study. In addition, gender difference in tibial rotational alignment were evaluated. Relative to the TEA, the MTT and ATS were externally rotated by 0.5° ± 4.4° and 0.5° ± 5.4°, respectively, while Akagi line and PTM were internally rotated by 3.7° ± 4.5° and 9.9° ± 6.1°, respectively. Gender differences were found in MTT, Akagi line and ATS (P < 0.05). Our result showed that the rotational alignment led to notable variance between femoral and tibial components using fixed bone landmarks. The MTT and ATS axes showed the closest perpendicular aspect with projected TEA. And the MTT and Akagi axes showed the reduced variance. In addition, PTM is not a reliable landmark for rotation of the tibial component. Based on the results of this study, surgeons may choose the proper anteroposterior axis of the tibial component in order to reduce rotational mismatch and improve clinical outcomes.

The femoral trochlear anterior line is a better alternative intra-operative reference compared to femoral anterior tangent line for femoral rotation in both genders in total knee arthroplasty.

PURPOSE: To determine the most reliable reference axis for the femoral component rotation in TKA patients by comparing the trochlear anterior line (TAL) and the femoral anterior tangent line (FAT). To evaluate the variability of each anatomic parameter in a Korean population. METHODS: Magnetic resonance images (MRIs) were taken for 500 patients (400 females and 100 males) with knee joint osteoarthritis who had Kellgren and Lawrence grade 3 and 4 prior to TKA in our institution between February 2016 and September 2017. It was investigated that whether significant differences in variance and gender exist for TAL and FAT. RESULTS: TAL and the FAT were internally rotated by 5.1° ± 3.1° and 6.8° ± 6.1°, respectively, about the Transepicondylar axis (TEA). Although no gender-related differences were found for the TAL, they were found for the FAT. The variance of the TAL with respect to the TEA was significantly smaller compared with that for the FAT and thus exhibited a more consistent distribution. In addition, such a trend was found for both genders. CONCLUSIONS: The results show that the TAL is a favorable index for appropriate rotational alignment of the femoral component in TKA.

Gender difference in bowing of the sagittal femoral morphology measurement using magnetic resonance imaging.

The importance of femoral sagittal bowing on total knee arthroplasty (TKA) has not been actively discussed. Femoral sagittal bowing can lead to cortex damage, fractures, or femoral malalignment. Therefore, the purpose of this study was to evaluate femoral sagittal bowing at different segments of the femur in the Korean population, and to discuss the implications on total knee arthroplasty. Differences in the morphology of femoral sagittal bowing for 978 patients-829 women and 148 men-were evaluated using magnetic resonance imaging. The angle between the femoral mechanical axis and the anterior cortex line was measured for all the patients. In addition, the gender difference in femoral sagittal bowing was investigated. The angle of femoral sagittal bowing with the mechanical axis was 2.8˚ ± 2.2˚. The angles for femoral sagittal bowing were 2.9˚ ± 2.2˚ and 2.3˚ ± 2.6˚ for females and males, respectively. Thus, a gender difference was found in the femoral sagittal bowing (p < 0.05). Excessive sagittal bowing of the femur can affect the final sagittal position of the femoral component, and this has implications for implant design selection. We recommend that surgeons accurately perform pre-operative evaluation of femoral bowing to prevent potential malalignment, rotation, and abnormal stresses between the femur and implant.

Morphometric study of gender difference in osteoarthritis posterior tibial slope using three-dimensional magnetic resonance imaging.

Posterior tibial slope (PTS) is an important parameter of sagittal alignment associated with postoperative stability and kinematics after total knee arthroplasty (TKA). However, data are limited regarding the innate gender differences in PTS in Koreans. The current study separately measured the PTS of the medial and lateral tibial plateau on magnetic resonance images of 511 patients with knee joint osteoarthritis who had Kellgren and Lawrence grade 3 and 4 (430 women, 81 men) and compared the measurements between and within the genders. The tibia was then rotated to the tibial plateau with the tibial centroid axis and the PTS was evaluated from best-fit planes on the surface of the proximal tibia and individually for the medial, lateral, and overall plateaus. The average overall PTS was 10.0° ± 3.5°. The average overall PTS of the female and male patients was 10.2° ± 3.4° and 8.8° ± 4.0°, respectively. The average medial PTS was 10.4° ± 4.0°, significantly greater than the mean lateral PTS of 8.7° ± 3.9° (P < 0.05). The average medial and lateral tibial slopes for female patients were 10.7° ± 3.8° and 8.8° ± 3.8°, respectively, while the average medial and lateral tibial slopes for male patients were 8.9° ± 4.8° and 7.9° ± 4.7°, respectively. The medial and overall PTS were significantly greater in female patients than in male patients (P < 0.05). The results showed a gender difference in PTS and that medial PTS was greater than lateral PTS. These findings have clinical relevance in knee reconstructive surgery for determining ideal placement of the posterior slope tibial component. Surgeons should be aware of variability and gender differences in the tibial slope of patients undergoing TKA.

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.

Morphologic difference and size mismatch in the medial and lateral tibial condyles exist with respect to gender for unicompartmental knee arthroplasty in the Korean population.

PURPOSE: The purpose of this study was to characterize the geometry of the proximal tibia in both genders in the Korean population. Anthropometric data on the medial and lateral tibial condyles of the osteoarthritic knees of 149 males and 814 females were obtained using three-dimensional magnetic resonance imaging. METHODS: In the medial and lateral proximal tibial condyles, the anteroposterior (AP) dimension, widest dimension (WD) at defined points, and condylar aspect ratio were evaluated. These measurements were compared with similar dimensions of the tibial components from five commonly used unicompartmental knee arthroplasty (UKA) designs in Korea. RESULTS: Both the AP dimension and WD in the medial and lateral tibial condyles of the male patients were significantly greater than those of the female patients (P < 0.05). In addition, the AP dimension and WD were greater in the medial than in the lateral tibial condyle (P < 0.05). There was WD overhang in three and two prostheses in the medial and lateral tibial condyles, respectively. A decrease in the condylar aspect ratio with an increasing AP dimension was found in the medial and lateral tibial condyles for both the male and female patients. CONCLUSIONS: Smaller medial and lateral tibial condylar dimensions are more frequent in Korean women than in Korean men. This study highlights the finding that conventional UKA designs lead to size mismatch in the Korean population and may indicate an important guideline on proper gender-specific UKA tibial prostheses with different WD/AP dimension aspect ratios. In addition, this study suggests that the shape of the medial tibial plateau is different to that of the lateral plateau, which can lead to a mediolateral overhang for medial UKA in an attempt to optimize the AP coverage. LEVEL OF EVIDENCE: III.