The relationship between the angle of the trochlear groove and patella cartilage and bone morphology--a cross-sectional study of healthy adults

Deep Learning for Automated Measurement of Patellofemoral Anatomic Landmarks

BACKGROUND

Patellofemoral anatomy has not been well characterized. Applying deep learning to automatically measure knee anatomy can provide a better understanding of anatomy, which can be a key factor in improving outcomes.

METHODS

483 total patients with knee CT imaging (April 2017-May 2022) from 6 centers were selected from a cohort scheduled for knee arthroplasty and a cohort with healthy knee anatomy. A total of 7 patellofemoral landmarks were annotated on 14,652 images and approved by a senior musculoskeletal radiologist. A two-stage deep learning model was trained to predict landmark coordinates using a modified ResNet50 architecture initialized with self-supervised learning pretrained weights on RadImageNet. Landmark predictions were evaluated with mean absolute error, and derived patellofemoral measurements were analyzed with Bland-Altman plots. Statistical significance of measurements was assessed by paired t-tests.

RESULTS

Mean absolute error between predicted and ground truth landmark coordinates was 0.20/0.26 cm in the healthy/arthroplasty cohort. Four knee parameters were calculated, including transepicondylar axis length, transepicondylar-posterior femur axis angle, trochlear medial asymmetry, and sulcus angle. There were no statistically significant parameter differences (p > 0.05) between predicted and ground truth measurements in both cohorts, except for the healthy cohort sulcus angle.

CONCLUSION

Our model accurately identifies key trochlear landmarks with ~0.20-0.26 cm accuracy and produces human-comparable measurements on both healthy and pathological knees. This work represents the first deep learning regression model for automated patellofemoral annotation trained on both physiologic and pathologic CT imaging at this scale. This novel model can enhance our ability to analyze the anatomy of the patellofemoral compartment at scale.

Ultrasound Measurement of Lateral Patellar Displacement: A Cadaveric Validation Study

Background

Patellofemoral pain syndrome (PFPS) is one of the most common musculoskeletal complaints seen in outpatient settings. It has been suggested that hip adduction creates loads on the iliotibial band and causes lateral displacement of the patella (patellar tilt), which can lead to uneven patellofemoral joint loading, and hence, cause patellofemoral pain. In previous studies in the literature, ultrasound has been used to measure lateral patellar displacement. However, the method lacks validity data.

Purpose/Hypothesis

The aim of this study was to validate the use of ultrasound to measure lateral displacement of the patella, by comparing the position of the patella as measured first by ultrasound, and then by direct measurement.

Study Design

Descriptive Laboratory Study.

Methods

Nine soft-fixed cadavers were used in this study. The cadavers had been donated for anatomical examination and research under the Human Tissue Act (2004). The distance between the lateral femoral condyle and the lateral edge of the patella were measured by B-mode real-time ultrasound, and then by direct measurement, in two positions, neutral and at 20° hip adduction.

Results

The mean difference in the patella-to-lateral femoral condyle distance in the neutral position and at 20° adduction was 0.27 cm (ultrasound), and 0.34 cm (direct measurement), respectively. There were no significant differences between the measurements obtained by US and by direct measurement (Pearson correlation= 0.97, p=0.83).

Conclusion

Ultrasound is a valid and reliable method for measuring patellar position relative to the femoral condyle, and the validity data reported here suggest that it can be used with confidence in clinic to assess lateral patellar displacement.

Level of Evidence

3.

Ultrasound investigation into the relationship between hip adduction and the patellofemoral joint

[Purpose] Patellofemoral pain (PFP) is a common musculoskeletal complaint. It has been suggested that hip adduction creates a load on the iliotibial band and causes lateral displacement of the patella (patella tilt). However, data gathered in a previous study were derived from a small sample of males, while the condition predominantly affects females. We assessed the relationship between hip adduction and patellar position with a larger sample size, including males and females. [Participants and Methods] Forty healthy, asymptomatic females and males (age 21.5 ± 1.3 years) were recruited. Their knees were passively flexed by 20°. Using ultrasound, the distance between the lateral edge of the patella and the lateral condyle of the femur was measured in the neutral position and at 20° adduction. [Results] Hip adduction produced a smaller patella-lateral femoral condyle measurement than in the neutral position. The mean difference in the patella-condyle distance between the neutral position and 20° hip adduction was 0.18 cm. No statistically significant difference was found between the right and left limbs, genders, Tegner scores, or BMI of the study participants. [Conclusion] The results of the study showed that hip adduction causes lateral displacement of the patella. Ultrasound is an effective means of assessing patella tilt.

Relation of the chondromalatia patellae to proximal tibial anatomical parameters, assessed with MRI

Background Magnetic resonance imaging (MRI) is a non-invasive highly sensitive tool for diagnosing chondromalacia patellae in the early stages. Many studies have evaluated patellar and trochlear morphology with different radiologic indices. We aimed to assess the discriminative power of tibial, patellar, and femoral indices in MRI for chondromalacia patellae. Patients and methods 100 cases of chondromalacia, as well as 100 age-matched controls among the patients who underwent knee MRI between February 2017 and March 2019, were included. The standard protocol of knee MRI was applied and the diagnosis of chondromalacia was made on MRI findings. Chondromalacia subjects were also classified as grade 1 to 4 according to the Modified Outerbridge's MRI grading system. We measured 25 MRI parameters in the knee and adjacent structures to determine the relation between chondromalacia patellae and anatomical MRI parameters. Results Tibial slope, trochlear depth, lateral trochlear inclination, and lateral patellar tilt angle had significant correlation with chondromalacia. Any increase in lateral trochlear inclination and lateral patellar tilt angle could increase the probability of the disease (Odds ratio [OR] 1.15, 1.13; 95% CI: 1.03-1.30; 1.02-1.26, respectively), while any increase in medial tibial slope and trochlear depth could decrease the probability of chondromalacia (OR 0.85, 0.06; 95% CI: 0.73-0.98, 0.02-0.17, respectively). We also designed a model for the severity of disease by using the patellar height index (relative odds ratio: 75.9). Conclusions The result of this study showed the novelty role of tibial anatomy in developing chondromalacia and its mechanism. We also concluded that patellar height might be an important factor in defining disease severity.

Visualization of Cartilage from Knee Joint Magnetic Resonance Images and Quantitative Assessment to Study the Effect of Age, Gender and Body Mass Index (BMI) in Progressive Osteoarthritis (OA)

Background:

Osteoarthritis (OA) is a degenerative disease of joint cartilage affecting the elderly people around the world. Visualization and quantification of cartilage is very much essential for the assessment of OA and rehabilitation of the affected people. Magnetic Resonance Imaging (MRI) is the most widely used imaging modality in the treatment of knee joint diseases. But there are many challenges in proper visualization and quantification of articular cartilage using MRI. Volume rendering and 3D visualization can provide an overview of anatomy and disease condition of knee joint. In this work, cartilage is segmented from knee joint MRI, visualized in 3D using Volume of Interest (VOI) approach.

Methods:

Visualization of cartilage helps in the assessment of cartilage degradation in diseased knee joints. Cartilage thickness and volume were quantified using image processing techniques in OA affected knee joints. Statistical analysis is carried out on processed data set consisting of 110 of knee joints which include male (56) and female (54) of normal (22) and different stages of OA (88). The differences in thickness and volume of cartilage were observed in cartilage in groups based on age, gender and BMI in normal and progressive OA knee joints.

Results:

The results show that size and volume of cartilage are found to be significantly low in OA as compared to normal knee joints. The cartilage thickness and volume is significantly low for people with age 50 years and above and Body Mass Index (BMI) equal and greater than 25. Cartilage volume correlates with the progression of the disease and can be used for the evaluation of the response to therapies.

Conclusion:

The developed methods can be used as helping tool in the assessment of cartilage degradation in OA affected knee joint patients and treatment planning.

Patellar Instability: When is Trochleoplasty Necessary?

Trochleoplasty is a very effective procedure for correcting trochlear dysplasia and addressing instability of the patella. With an increasing knowledge about the anatomy and biomechanics of the anterior distal femur, a wider array of surgical techniques may be applied to address specific conditions. Patients must be carefully selected to undergo trochleoplasty by use of a thorough history and physical examination as well as basic and advanced imaging. The presence of a "J sign" on physical examination, a history of recurrent instability, patella alta, trochlear dysplasia, and elevated tibial tubercle to trochlear groove are signs and symptoms for which the patient should be evaluated. We attempt to elucidate when trochleoplasty is indicated by means of addressing all aspects of evaluation.

The Patello-Femoral Joint Degeneration and the Shape of the Patella in the Population Needing an Arthroscopic Procedure

Background: the main goal of the study was to investigate the prevalence of the articular cartilage defects (ACD) in the patellofemoral (PF) region of the knee joint based on the anatomical shapes of patella and its impact on the level of physical activity in the population needing arthroscopic procedures for all types of pathologies in the knee. Methods: The articular cartilage status of the PF region was obtained from 1098 arthroscopic procedures of the knee joint. The ACD were correlated to Wiberg’s shape of the patella and classified according to the degree, size and depth of the ACD in the PF region using the ICRS (International Cartilage Repair Society) system: group I consisting of patients with Wiberg type I shape (W1), group II—patients with Wiberg type II shape (W2) and group III—patients with Wiberg type III shape (W3). The Tegner physical activity scale was used to evaluate the physical activity of the patients. Results: The mean of ACD size (PF region) in the W3 group was 3.10 ± 0.99 cm², which was a statistically significantly larger area in comparison with the W1 (1.90 ± 0.63 cm²; p < 0.0000) and W2 (1.95 ± 0.71 cm²; p < 0.0000). The patients from the W3 group (mean 3.10 ± 0.99) were less physically active (<4 Tegner) compared to the W2 group (mean of 4.48 ± 0.88; p = 0.004) and W1 group (mean of 4.55 ± 0.72; p = 0.002). Conclusions: The patients with the Wiberg type III patella shape had a higher incidence and larger size of ACD in the PF of the knee compared to the groups of Wiberg type I and II. Wiberg III patients with a lower level of physical activity had a larger size of ACD in the PF joint.

Analysis of the articular cartilage T1ρ and T2 relaxation times changes after ACL reconstruction in injured and contralateral knees and relationships with bone shape

The objectives of this study were twofold: (1) to evaluate the longitudinal change in cartilage T_1ρ and T₂ 6- and 12-months after ACL reconstruction (ACLR) in both reconstructed and intact contralateral knees with the aim of validating the role of the contralateral knee as an internal control in longitudinal studies; (2) to explore relationships between bone shape at the time of injury and the progression of T_1ρ and T₂ over 12-months after ACLR. T_1ρ and T₂ cartilage relaxation times and 3D MRI-based statistical shape modeling (SSM) of tibia and femur were computed for both knees of forty ACL-injured patients and 15 healthy controls. ACL subjects were scanned 8.4 ± 6.4 weeks after injury (2.4 ± 3.7 weeks prior to ACLR), 6- and 12-months after ACLR. Longitudinal changes in T_1ρ and T₂ values were assessed using linear mixed model, and partial correlation coefficients were calculated between bone shape and longitudinal changes in T_1ρ and T₂ values. Significant longitudinal increases in T_1ρ and T₂ values were observed in reconstructed and contralateral knees 6-months after ACLR. Tibial bone shape features, associated with the medial plateau height and width, were observed to be correlated with cartilage T_1ρ and T₂ progression in reconstructed knees. Our results suggest that caution should be used in considering contralateral knee as internal controls in longitudinal ACL studies and 3D MRI-based-SSM might serve as an imaging biomarker for the early stratification of patients at risk for developing post-traumatic accelerated cartilage degeneration and potentially osteoarthritis after ACL tear. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:707-717, 2017.

Patient-specific modeling of the trochlear morphologic anomalies by means of hyperbolic paraboloids

Diagnostic and therapeutic purposes are issuing pressing demands to improve the evaluation of the dysplasia condition of the femoral trochlea. The traditional clinical assessment of the dysplasia, based on Dejour classification, recognized 4 increasing (A, B, C, D) levels of severity. It has been extensively questioned in the literature that this classification methodology can be defective suggesting that quantitative measures can ensure more reliable criteria for the dysplasia severity assessment. This study reports on a novel technique to model the trochlear surface (TS), digitally reconstructed by 3D volumetric imaging, using three hyperbolic paraboloids (HP), one to describe the global trochlear aspect, two to represent the local aspects of the medial and lateral compartments, respectively. Results on a cohort of 43 patients, affected by aspecific anterior knee pain, demonstrate the consistency of the estimated model parameters with the morphologic aspect of the TS. The obtained small fitting error (on average lower than 0.80 mm) demonstrated that the ventral aspect of the trochlear morphology can be modeled with high accuracy by HPs. We also showed that HP modeling provides a continuous representation of morphologic variations in shape parameter space while we found that similar morphologic anomalies of the trochlear aspect are actually attributed to different severity grades in the Dejour classification. This finding is in agreement with recent works in the literature reporting that morphometric parameters can only optimistically be used to discriminate between the Grade A and the remaining three grades. In conclusion, we can assert that the proposed methodology is a further step toward modeling of anatomical surfaces that can be used to quantify deviations to normality on a patient-specific basis.

Prevalence and clinical significance of chondromalacia isolated to the anterior margin of the lateral femoral condyle as a component of patellofemoral disease: observations at MR imaging

OBJECTIVE

To determine the prevalence of chondromalacia isolated to the anterior margin of the lateral femoral condyle as a component of patellofemoral disease in patients with anterior knee pain and to correlate it with patient demographics, patellar shape, and patellofemoral alignment.

MATERIALS AND METHODS

Retrospective study over a 1-year period reviewing the MR knee examinations of all patients who were referred for assessment of anterior knee pain. Only patients with isolated lateral patellofemoral disease were included. Age, gender, distribution of lateral patellofemoral chondromalacia, and grade of cartilaginous defects were documented for each patient. Correlation between the distribution of lateral patellofemoral chondromalacia and patient demographics, patellar shape, and indices of patellar alignment (femoral sulcus angle and modified Q angle) was then ascertained.

RESULTS

There were 50 patients (22 males, 28 females) with anterior knee pain and isolated patellofemoral disease. The majority of the patients (78 %) had co-existent disease with grade 1 chondromalacia. No significant correlation was found between patients with chondromalacia isolated to the anterior margin of the lateral femoral condyle and age, gender, patellar shape, or modified Q angle (p > 0.05). However, patients with chondromalacia isolated to the anterior margin of the lateral femoral condyle had a shallower femoral sulcus angle (mean 141.8°) compared to the patients with lateral patellar facet disease (mean 133.8°) (p = 0.002).

CONCLUSIONS

A small percentage of patients with anterior knee pain have chondromalacia isolated to the anterior margin of the lateral femoral condyle. This was associated with a shallower femoral sulcus angle.

Relationship between the trochlear groove angle and patellar cartilage morphology defined by 3D spoiled gradient-echo imaging

OBJECTIVE

To examine whether the femoral trochlear groove angle (TGA) is a determinant of the patellar cartilage volume and patellar cartilage damage.

MATERIALS AND METHODS

Patellar cartilage was evaluated by MR imaging in 66 patients (22 males and 44 females) with knee pain. Fat-suppressed 3D spoiled gradient-echo images were used to calculate the cartilage volume and to grade the cartilage damage. The proximal and distal TGAs were measured from axial PD-weighted FSE MR images with fat suppression.

RESULTS

For every increase in the TGA at the distal femur, the patellar cartilage volume was significantly increased by 6.07 × 10(-3) cm(3) (95% CI: 1.27 × 10(-3), 10.9 × 10(-3)) after adjustment for age, gender, and patellar bone volume (P < 0.05). The MR grade of medial patellar cartilage damage progressed as the distal TGA became narrower, although there was no significant correlation between the distal TGA and the MR grading of patellar cartilage damage.

CONCLUSION

A more flattened distal TGA was associated with increased patellar cartilage volume. However, there was no association between TGA and patellar cartilage defects.

PATELLA TRACKING WITH PERIPATELLAR SOFT TISSUE STABILIZERS AS A FUNCTION OF DYNAMIC SUBJECT-SPECIFIC KNEE FLEXION

Musculoskeletal modeling has found wide application in joint biomechanics investigations. This technique has been improved by incorporating subject-specific skeletal elements and passive patellofemoral stabilizers in a dynamic analysis. After trochlear engagement, the volunteers' patellae displaced laterally, whereas tilt was subject specific. Comparison of the tilt and mediolateral position values to in vivo MRI values at 30° knee flexion showed a mean accuracy of 84.4% and 96.9%, respectively. Medial patellofemoral ligament tension decreased with knee flexion, while the patellar tendon–quadriceps tendon ratio ranged from 0.4 to 1.2. The patellofemoral contact load–quadriceps tendon load ratio ranged from 0.7 to 1.3, whereas the mediolateral load component–resultant load ratio ranged from 0 to 0.4. Three validated subject-specific musculoskeletal models facilitated the analysis of patellofemoral biomechanics: Subject-specific patella tracking and passive stabilizer response was analyzed as a function of dynamic knee flexion.

Development of femoral trochlear groove in growing rabbit after patellar instability

PURPOSE

The geometry of an articular surface is an important determinant of joint function. Although the geometry of the trochlear groove is considered to be important in the pathogenesis of patellofemoral joint disorders, the effects of the patella during the development of the femoral trochlear groove are unclear. This animal study aimed to investigate the relationship between the position of the patella and development of femoral trochlear groove in growing rabbits.

METHODS

Twenty-four knees of 12 rabbits were included in this study and were divided into two groups. First group consisted of the left knees and was used as the control group to which no surgical procedures were applied. Second group involved the right knees to which medial soft tissue restraints release was applied before 1 month of age. Computed tomographic (CT) evaluation of both knees of each rabbit was made in their first month of age before medial retinacular release and also during post-op 1-year follow-up. CT measurements included both the angle and depth of the femoral trochlear groove from 3 different parts (proximal, middle and distal) of the distal femur, and then these measurements were averaged.

RESULTS

Measurements revealed that while in the control group the groove angle decreased 27.4 degrees and the depth increased 0.11 mm, in the operated counterparts groove angle decreased 16.8 degrees and groove depth increased 0.03 mm, which indicated the flattening of the femoral groove in the operated group. These differences were found to be statistically significant (P < 0.05).

CONCLUSION

The results indicated that distal femoral groove with inadequate patellar position becomes more flattened and causes predisposition for patellar instability. Consequently, the clinical relevance of this study was that early reconstruction of the patellofemoral joint should be performed in the childhood to prevent the patellofemoral problems that are likely to be encountered in the following years.

The morphometry of patella and patellar ligament during the fetal period

This study aims to determine the development and morphology of the patella and patellar tendon and to obtain morphometric data about these structures during the fetal period. One hundred five human fetuses (55 males and 50 females) aged 9-40 weeks were used in this study. Fetuses were divided into four groups between gestational weeks; Group I (9-12 weeks), Group II (13-25 weeks), Group III (26-37 weeks), and Group IV (38-40 weeks). The patella and patellar ligament were exposed via anatomical dissection; the dimensions (length, width, thickness) and the width of the lateral and medial articular surfaces of the patella, and the length and width of the patellar ligament, were measured using a Vernier's caliper. No significant differences were observed between genders or sides for any of the parameters (P > 0.05), and a significant correlation was found between gestational age and all parameters (P < 0.001). All parameters of the patella and patellar ligament were found to be different statistically between trimesters (P < 0.05). This study reveals the development, morphological changes, and the morphometric measurements of the patella and patellar ligament during the fetal period. We hope that the present results can be useful for future studies.

Statistical shape modeling describes variation in tibia and femur surface geometry between Control and Incidence groups from the osteoarthritis initiative database

We hypothesize that variability in knee subchondral bone surface geometry will differentiate between patients at risk and those not at risk for developing osteoarthritis (OA) and suggest that statistical shape modeling (SSM) methods form the basis for developing a diagnostic tool for predicting the onset of OA. Using a subset of clinical knee MRI data from the osteoarthritis initiative (OAI), the objectives of this study were to (1) utilize SSM to compactly and efficiently describe variability in knee subchondral bone surface geometry and (2) determine the efficacy of SSM and rigid body transformations to distinguish between patients who are not expected to develop osteoarthritis (i.e. Control group) and those with clinical risk factors for OA (i.e. Incidence group). Quantitative differences in femur and tibia surface geometry were demonstrated between groups, although differences in knee joint alignment measures were not statistically significant, suggesting that variability in individual bone geometry may play a greater role in determining joint space geometry and mechanics. SSM provides a means of explicitly describing complete articular surface geometry and allows the complex spatial variation in joint surface geometry and joint congruence between healthy subjects and those with clinical risk of developing or existing signs of OA to be statistically demonstrated.