Quantification of patellar tracking using kinematic MRI

Sulcus Angle, Trochlear Depth, and Dejour's Classification Can Be Reliably Applied To Evaluate Trochlear Dysplasia: A Systematic Review of Radiological Measurements

PURPOSE

To summarize data on the reliability of available imaging criteria for the assessment of trochlear dysplasia and to assess the methodological quality of the included studies.

METHODS

This systematic review was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guideline. Search was performed using major electronic databases from their inception to September 2021. All studies enrolling patients of any age who underwent a radiological exam to rule out features related to trochlear dysplasia were included. After the identification of available imaging criteria, reliability studies were analyzed. Descriptive statistics were used to summarize findings. Methodological quality was assessed using the Quality Appraisal of Reliability studies checklist.

RESULTS

A total of 2391 articles were identified, and 33 articles comprising 3036 patients with a mean age of 28.6 years were included. Thirty different measurements were extracted. Magnetic resonance imaging (MRI) was the most used imaging modalities (21 studies), followed by computed tomography (10 studies), conventional radiology (8 studies) and ultrasonography (US) (1 study). Sulcus angle, trochlear depth, and Dejour's classification were the most explored measurements. Overall, sulcus angle can be reliably assessed on radiography, CT and MRI, whereas trochlear depth can be reliably measured only with CT and MRI. Reliability of Dejour's classification ranged from poor or fair to very good for all imaging modalities. Methodological quality of included studies varied from 2 to 9 positive items out of 11 possible. Twenty-four studies (72.7%) were considered at high risk of bias.

CONCLUSION

Trochlear dysplasia can be reliably evaluated at least with 3 measurements: sulcus angle, trochlear depth and Dejour's classification. Methodological quality assessment showed high risk of bias in most included studies.

LEVEL OF EVIDENCE

Level III, systematic review of Level II-III studies.

Mid-term study on the effects of arthroscopic discoid lateral meniscus plasty on patellofemoral joint: An observational study

In the present study, we aimed to investigate the clinical outcomes of arthroscopic discoid lateral meniscus (DLM) plasty and the adaptive changes in the patellofemoral joint after surgery. From September 2010 to March 2012, 25 patients with DLM injuries who underwent arthroscopic meniscus plasty were enrolled in the prospective study. All patients underwent clinical evaluation before the operation and at the last follow-up, and imaging evaluation was performed by upright magnetic resonance imaging before and 1 month after the operation as well as at the last follow-up. Clinical evaluation included Lysholm score, Kujala score, McMurray's sign, patellar mobility, patella grind test, and quadriceps atrophy. Imaging evaluation included bisect offset index, patella tilt angle (PTA), and cartilage damage. Lysholm score, Kujala score, McMurray's sign, and quadriceps atrophy at the last follow-up were significantly improved compared with the preoperative levels (P < .05). At the last follow-up, there were no statistical differences in patella mobility and patella grind test compared with the preoperative levels. In addition, bisect offset index and PTA showed a dynamic trend of rising and then falling over time (P < .05). At 1 month after the operation, bisect offset index and PTA were significantly increased compared with the preoperative levels or the values at the last follow-up (P < .05), while there were no differences between the preoperation and the last follow-up. Cartilage damage became worse with time (P < 0.05), and the 2 were positively correlated (Spearman = 0.368). At the last follow-up, the degree of cartilage damage was significantly increased compared with the preoperative level (P < .017), while there was no significant difference between the 1-month postoperative grade and the preoperational grade or the last follow-up grade. The effect of arthroscopic DLM plasty on the patellofemoral joint was dynamic, with the position of the patella deviating in the early stages and recovering in the mid-term, especially when the knee was in the biomechanical standing position. In addition, the patellofemoral joint cartilage might undergo accelerated degeneration after the operation, while the mid-term effect of the operation was positive, and the patellofemoral joint function was acceptable.

Biomechanical characteristics and muscle function in individuals with patellofemoral osteoarthritis: A systematic review of cross-sectional studies

BACKGROUND

Our objective was to investigate kinematic and kinetic characteristics and changes in muscle function in individuals with patellofemoral osteoarthritis compared to healthy individuals.

METHODS

Searches were performed of the Medline, Embase, Web of Science, The Cochrane Library, LILACS, and SciELO databases until May of 2022 for observational studies comparing individuals with patellofemoral osteoarthritis to a control group. The PRISMA guidelines and recommendations of the Cochrane Collaboration were followed. The GRADE approach was used to analyze and synthesize the level of evidence.

FINDINGS

Fourteen studies were included, involving a total of 594 participants (360 with patellofemoral osteoarthritis and 234 controls). The level of evidence for pelvis, hip adduction and knee abduction angles at 45° of knee flexion during the single-leg squat, and knee flexion angle during the task of walking was very low. Regarding muscle strength, the level of evidence for isometric strength of the hip abductors, extensors and external rotators, and concentric strength of the knee extensors and flexors was very low. It was not possible to synthesize any type of evidence for kinetic, electromyography, or muscle volume variables.

INTERPRETATION

The level of evidence was very low for all synthesized evidence for kinematic and muscle strength variables. However, individuals with patellofemoral osteoarthritis have lower isometric strength of the hip abductor muscles. Further studies with adequate adjustment for confounding factors, such as the non-inclusion of individuals with osteoarthritis in the tibiofemoral compartment concomitant to patellofemoral osteoarthritis, are needed to gain a better understanding of the clinical characteristics of patellofemoral osteoarthritis.

Lateral Patellar Inclination Angle Measured via a Two-Image Technique on Axial Magnetic Resonance Imaging

Lateral patellar inclination (LPI) measures patellar tilt and is historically described on axial X-ray or a single magnetic resonance image (MRI). Given the variability in patellar height, LPI may be better represented by performing this measurement on two separate axial MRI images. We hypothesized that a two-image LPI measurement would be different from the current single-image LPI and have similar, if not superior reliability. Sixty-five patients treated for patellar instability (PI) between 2014 and 2017 were identified. Single image and two-image LPI were measured on axial MRI images. All measurements were performed by two independent observers. Reliability analysis was based on three observers' measurements of 30 randomly selected patients. Both the one image and two image LPI showed good inter-rater reliability (intraclass correlation coefficient [ICC] = 0.71 and 0.89, respectively), although the two image LPI had less variability. Both single image and two image LPI had near perfect intra-rater reliability (ICC = 0.98 and 0.98, respectively). Average single image LPI (14.6 ± 9.9 degrees) was 6.1 ± 3.4 degrees less than the average two image LPI (19.6 ± 9.4 degrees) (p = 0.037). Referencing a previously described 13.5 degrees maximum threshold, 54% of the patients had excessive patellar tilt based on single image LPI, while 73% had pathologic patellar tilt based on two image LPI. Two image LPI has similar reliability with less inter-rater variability compared with the historical single image LPI measurement. Significantly greater patellar tilt was identified with two image LPI that was found with single image LPI. A larger percentage of patients were classified as having pathologic patellar tilt based on two image LPI than single image LPI. The two image LPI provides more consistent and representative measurements of patellar tilt. Previously described threshold values for patellar tilt should be re-examined using this new measurement technique to appropriately risk stratify patients with PI and patellofemoral pain.

Sonographic evaluation of patellar tendon displacement and its correlation with patellofemoral pain syndrome

Background

Patellofemoral pain syndrome is the most common knee condition and is associated with patellar maltracking. Ultrasound is used in studying patellar maltracking. The objective is to determine if the technique which analyzes the displacement of the patellar tendon in the trochlear sulcus is associated with patellofemoral pain syndrome.

Methods

In total, 68 knees of 34 football players (males = 20, females = 14) were included. Patellar tendon displacement was assessed in supine and standing positions. Patellar tendon displacement difference in the two positions was determined.

Results

There was a significant difference in the lateral patellar tendon displacement during standing which was larger in patellofemoral pain syndrome than without patellofemoral pain syndrome (Mean Rank = 39.20 vs. 30.32, p = 0.02). There was no significant difference between the two groups for lateral patellar tendon displacement in supine and the difference in patellar tendon displacement from supine to standing.

Conclusion

The technique could be a potential method in assessing patellar maltracking. It could be used to have a comprehensive understanding of the pathomechanics and treatment of patellofemoral pain syndrome.

The relationship between patellar tilt and quadriceps patellar tendon angle with anatomical variations and pathologies of the knee joint

PURPOSE

To investigate the association between the knee joint anatomical variations and pathologies, and to describe the quadriceps patellar tendon angle (QPA).

METHODS

MRIs of 406 cases with a lateral patellar tilt angle (LPT)>5° and a control group of 40 cases with an LPT<5° were retrospectively evaluated. QPA, LPT, trochlear sulcus angle (TSA), tibial tubercle-trochlear groove distance (TT-TG), Insall-Salvati index (ISI), patellar tendon length (PTL), patellar height (PH), lateral trochlear inclination (LTI), trochlear facet asymmetry ratio (TFA) and trochlear depth (TD) were measured. Presence of fat-pad oedema, patellar and trochlear chondromalacia, patellar and quadriceps tendinosis and effusion were evaluated.

RESULTS

The medians of TSA, PTL, ISI and TT-TG were significantly higher; LTI, TFA and TD were significantly lower in the patient group. The prevalence of SL-Hoffa, non-SL-Hoffa, suprapatellar and prefemoral fat-pad oedema, effusion and chondromalacia were significantly higher in the patient group. LPT was found to be positively correlated with TSA and TT-TG, and negatively correlated with LTI and TD. Cases with trochlear dysplasia, patellar chondromalacia and quadriceps tendinosis had significantly higher LPT. There was a positive correlation between QPA and TSA and a negative correlation between QPA and LTI. Cases with trochlear dysplasia, non-SL-Hoffa oedema, prefemoral fat-pad oedema and quadriceps tendinosis had significantly higher QPA. We found 10°<LPT to be a cut-off value to cause SL-Hoffa fat pad oedema.

CONCLUSION

The anatomical variations of the knee joint are associated with fat-pad, cartilage and tendon pathologies.

Morphological study of the vastus medialis oblique in recurrent patellar dislocation based on magnetic resonance images

Background

To investigate the morphological parameters of the vastus medialis obliquus (VMO) muscle and delineate its importance in the maintenance of patellofemoral joint stability.

Methods

The magnetic resonance imaging data of seventy-five knees (fifty-four patients) with recurrent lateral patella dislocation (LPD) and seventy-five knees (seventy patients) without recurrent LPD were retrospectively analysed. Five morphological parameters related to the VMO (elevation in the sagittal plane and coronal plane, craniocaudal extent, muscle-fibre angulation, cross-sectional area ratio) and two patella tilt parameters (patella tilt angle, bisect offset ratio) were measured in MR images. The independent-samples t test or chi-square test was used for statistical comparisons.

Results

The mean ages of the patients in the recurrent LPD group and control group were 22.1 ± 9.9 years and 24.0 ± 6.5 years, respectively. Eighteen out of seventy-five (24%) patients MRI showed VMO injuries. Compared with the control group, the patients with recurrent LPD showed significantly higher sagittal VMO elevation (10.4 ± 2.3 mm vs. 4.1 ± 1.9 mm), coronal VMO elevation (15.9 ± 5.7 mm vs. 3.9 ± 3.7 mm), muscle-fibre angulation (35.4 ± 8.0° vs. 27.9 ± 6.3°), patella tilt angle (25.9 ± 10.7° vs. 9.1 ± 5.2°), and bisect offset ratio values (0.9 ± 0.3 vs. 0.5 ± 0.1) and significantly lower craniocaudal extent (13.7 ± 5.3 mm vs. 16.7 ± 5.1 mm) and cross-sectional area ratio values (0.05 ± 0.02 vs. 0.07 ± 0.02).

Conclusions

The results showed that abnormalities in the VMO and patella tilt were clearly present in recurrent LPD patients compared with normal people.

The inclination of the femoral medial posterior condyle was almost vertical and that of the lateral was tilted medially

PURPOSE

The purpose of this study was to three-dimensionally analyse the size and shape of the femoral posterior condyles of the normal knee.

METHODS

A total of 62 healthy Japanese volunteers (37 males and 25 females) providing a sample of 124 normal knee joints, who had no knee-related symptoms and no history of major trauma, underwent computed tomography scans of the bilateral femur and tibia. Three-dimensional digital models of the femur were constructed from computed tomography data using visualisation and modelling software. The following parameters were evaluated: (1) the radii of the posterior condyles approximated to spheres and (2) the inclination angle of the posterior condyles in the coronal plane of the femoral coordinate system.

RESULTS

The radii of the medial and lateral condyles approximated to spheres were 17.0 ± 1.6 and 17.1 ± 1.8 mm, respectively and were not different. The inclination angles of the medial and lateral condyles in the coronal plane were - 0.6° ± 4.6° and 9.7° ± 5.7°, respectively. The medial condyle was almost vertical, whereas the lateral one was medially tilted.

CONCLUSIONS

This study found an asymmetrical inclination between medial and lateral condyles. This may be related to the asymmetrical motion of the knee, which is known as medial pivot motion. This finding provides valuable morphological information and may be useful for implant designs for total knee arthroplasty.

LEVEL OF EVIDENCE

IV.

Dynamic MRI for articulating joint evaluation on 1.5 T and 3.0 T scanners: setup, protocols, and real-time sequences

Dynamic magnetic resonance imaging (MRI) is a non-invasive method that can be used to increase the understanding of the pathomechanics of joints. Various types of real-time gradient echo sequences used for dynamic MRI acquisition of joints include balanced steady-state free precession sequence, radiofrequency-spoiled sequence, and ultra-fast gradient echo sequence. Due to their short repetition time and echo time, these sequences provide high temporal resolution, a good signal-to-noise ratio and spatial resolution, and soft tissue contrast. The prerequisites of the evaluation of joints with dynamic MRI include suitable patient installation and optimal positioning of the joint in the coil to allow joint movement, sometimes with dedicated coil support. There are currently few recommendations in the literature regarding appropriate protocol, sequence standardizations, and diagnostic criteria for the use of real-time dynamic MRI to evaluate joints. This article summarizes the technical parameters of these sequences from various manufacturers on 1.5 T and 3.0 T MRI scanners. We have reviewed pertinent details of the patient and coil positioning for dynamic MRI of various joints. The indications and limitations of dynamic MRI of joints are discussed.

Static patella tilt and axial engagement in knee extension are mainly influenced by knee torsion, the tibial tubercle-trochlear groove distance (TTTG), and trochlear dysplasia but not by femoral or tibial torsion

PURPOSE

The aim of this study was to investigate the association of femoral (FT), tibial (TT), and knee torsion (KT) on the patella tilt (PT), the axial engagement index (AEI), and the tibial tuberosity-trochlear groove distance (TTTG).

METHODS

Femoral torsion, tibial torsion, knee torsion, patella tilt, the axial engagement index, the TTTG, and trochlear dysplasia were retrospectively evaluated on 59 patients suffering from recurrent patella instability or anterior knee pain with 118 torsional lower limb magnetic resonance imaging studies.

RESULTS

FT and TT did not show any significant associations with TTTG, PT, and AEI (n.s.). KT was significantly associated with a higher TTTG, higher PT, and lower AEI (all, p < 0.001). Higher grade trochlear dysplasia was associated with a higher PT and lower AEI (both, p < 0.001). The Dejour classification showed no significant association with FT, TT, KT, and TTTG (n.s.). All measurement parameters showed an excellent interrater agreement (ICC 0.89-0.97).

CONCLUSIONS

Static patella tilt and patellofemoral axial engagement in knee extension are mainly influenced by knee torsion, TTTG, and trochlear dysplasia but not by femoral or tibial torsion. These findings help to understand the underlying reasons for the patella position in knee extensions in CT and MRI investigations in patients suffering from patella instability and patellofemoral pain syndrome.

LEVEL OF EVIDENCE

III.

The Effect of Diacutaneous Fibrolysis on Patellar Position Measured Using Ultrasound Scanning in Patients With Patellofemoral Pain Syndrome

Context: Tightness or lack of flexibility of several muscles of the thigh has been associated with patellofemoral joint pain. A tight iliotibial band can lead to laterally located patella and an abnormal patellar tracking pattern. Diacutaneous fibrolysis (DF) is commonly used to reduce muscle tightness, but no studies have evaluated the effects of this technique in the treatment of patients with patellofemoral pain syndrome. Objective: To assess the effect of DF on patellar position in patients with patellofemoral pain syndrome. Design: A single-group, pretest–posttest clinical trial. Setting: University of Zaragoza. Participants: A total of 46 subjects with patellofemoral pain (20 males, 26 females; age: 27.8 [6.9] y). Intervention: Three sessions of DF. Main Outcome Measures: Patellar position measurement using real-time ultrasound scanning; pain intensity measured with visual analog scale and function measured with the Anterior Knee Pain Scale. Results: The application of 3 sessions of DF significantly increased the patellar position at posttreatment evaluation (P < .001) and at 1-week follow-up (P < .001). There was not a significant difference on patellar position between posttreatment and follow-up measurements (P = .28). There were also a statistically significant decrease in pain and increase in function at posttreatment and at 1-week follow-up measurements (P < .001). Conclusion: This study found that patellar position, pain intensity, and function were significantly improved after 3 sessions of DF and at 1-week follow-up.

Patellofemoral Stabilization: Postoperative Redislocation and Risk Factors Following Surgery

Background

Patellofemoral instability is a common knee problem that is difficult to manage owing to its multifactorial etiology as well as the fact that predisposing pathoanatomic features vary from individual to individual. There is limited knowledge regarding the demographic and pathoanatomic risk factors or the relationship between these risk factors and the redislocation rate after surgical stabilization for this challenging condition.

Purpose

To analyze the postoperative redislocation rates and the prevalence of demographic and pathoanatomic risk factors for patients undergoing a patellofemoral stabilization.

Study Design

Case series; Level of evidence, 4.

Methods

Patients with symptomatic recurrent patellofemoral instability underwent a soft tissue patellofemoral stabilization procedure. A total of 342 patellofemoral stabilization procedures (reconstruction, n = 256; imbrication, n = 86) were assessed at a mean follow-up of 24.3 months. Concomitant procedures were performed in accordance with the à la carte concept of addressing significant anatomic or biomechanical characteristics. Two surgical cohorts were analyzed separately for reconstruction or imbrication to address laxity of the medial patellofemoral ligament (MPFL). Failure of the patellofemoral stabilization procedure was defined as postoperative redislocation of the patella. Prevalence of demographic and pathoanatomic risk factors was determined for all patients. Disease-specific patient-reported outcomes were assessed with the Banff Patella Instability Instrument (BPII).

Results

A redislocation rate of 5.1% was identified for MPFL reconstruction and 20.9% for MPFL imbrication. For both MPFL procedures, age at time of surgery was significantly younger for the failed group as compared with the intact group. Postoperative BPII scores were significantly lower for patients who subsequently experienced a surgical failure as compared with intact surgery for both MPFL reconstruction (P = .048) and MPFL imbrication (P = .003).

Conclusion

Patellofemoral stabilization with an à la carte approach to surgical selection demonstrated a low postoperative redislocation rate and good clinical results. Younger age at time of surgery was associated with surgical failure. This information may be used to guide surgical decision making and patient education.

Research Methods and Progress of Patellofemoral Joint Kinematics: A Review

Patellofemoral pain syndrome has a high morbidity, and its pathology is closely associated with patellofemoral joint kinematics. A series of in vivo and in vitro studies have been conducted to explore patellofemoral kinematics, and the findings are relevant to the diagnosis, classification, and management of patellofemoral diseases and even the whole knee joint. However, no definite conclusion on normal patellofemoral kinematics has been established. In this study, the measurement methodologies of patellofemoral kinematics (including data collection methods, loading conditions, and coordinate system) as well as their advantages and limitations were reviewed. Motion characteristics of the patella were analyzed. During knee flexion, the patellar flexion angle lagged by 30–40% compared to the tibiofemoral joint flexion. The patella tilts, rotates, and shifts medially in the initial stage of knee flexion and subsequently tilts, rotates, and shifts laterally. The finite patellar helical axis fluctuates near the femoral transepicondylar axis or posterior condylar axis. Moreover, factors affecting kinematics, such as morphology of the trochlear groove, soft tissue balance, and tibiofemoral motion, were analyzed. At the initial period of flexion, soft tissues play a vital role in adjusting patellar tracking, and during further flexion, the status of the patella is determined by the morphology of the trochlear groove and patellar facet. Our findings could increase our understanding of patellofemoral kinematics and can help to guide the operation plan for patients with patellofemoral pain syndrome.

The influence of isolated femur and tibia rotations on patella cartilage stress: a sensitivity analysis

BACKGROUND

To determine the influence of femur and tibia rotations in the transverse and frontal planes on patella cartilage stress.

METHODS

Patella cartilage stress profiles of six healthy females were obtained during a squatting task using subject-specific finite element models of the patellofemoral joint (45° of knee flexion). Input parameters for the finite element model included joint geometry, quadriceps muscle forces, and weight-bearing patellofemoral joint kinematics. The femur and tibia of each model were then rotated to 2°, 4°, 6°, 8°, and 10° along their respective axes beyond that of the natural degree of rotation in weight-bearing. The process was repeated for internal rotation, external rotation, adduction, and abduction. Quasi-static loading simulations were performed to quantify average patella cartilage stress.

FINDINGS

Incremental femur internal rotation beyond that of the natural rotation resulted in progressively greater patella cartilage stress (41-77%), whereas incremental tibia internal rotation resulted in a decrease in patella cartilage stress (7-10%). Femur and tibia external rotation resulted in a mild increase in patella cartilage stress, but only at 10° (9%). Incremental femur adduction resulted in an increase in patella cartilage stress, but only at 10° (43%). Femur abduction and frontal plane tibia rotation in either direction had no influence on patella cartilage stress.

INTERPRETATION

Femur internal rotation and adduction resulted in the greatest increases in patella cartilage stress. In contrast, tibia rotations in the transverse and frontal planes had minimal to no influence on patella cartilage stress. These results emphasize the need for clinicians to identify and correct faulty hip kinematics in persons with PFP.

Editorial Commentary: Is Magnetic Resonance Imaging Imaged Knee Patellar Tracking Relevant in Assessing the Patient With Patellar Instability?

Patellar pain and instability are common presentations to surgeons, yet assessment is more a static art than a dynamic science. In addition to resource-intensive gait laboratory, computed tomography (CT) and magnetic resonance imaging (MRI) have been used to measure patellar tracking. CT has the limitation of radiation and MRI has the limitation of software processing times. With an updated MRI protocol and software, it is now possible to dynamically view patellar tracking. Determining how this will be used to help in the diagnosis and treatment of patients will be the next goal.

Clinical Utility of Continuous Radial Magnetic Resonance Imaging Acquisition at 3 T in Real-time Patellofemoral Kinematic Assessment: A Feasibility Study

PURPOSE

To compare patellar instability with magnetic resonance imaging analysis using continuous real-time radial gradient-echo (GRE) imaging in the assessment of symptomatic patients and asymptomatic subjects.

METHODS

Symptomatic patients with suspected patellofemoral maltracking and asymptomatic volunteers were scanned in real time by a radial 2-dimensional GRE sequence at 3 T in axial orientation at the patella level through a range of flexion-extension. The degree of lateral maltracking, as well as the associated tibial tubercle-trochlear groove distance and trochlea depth, was measured. Patellar lateralization was categorized as normal (≤2 mm), mild (>2 to ≤5 mm), moderate (>5 to ≤10 mm), or severe (>10 mm). The patellofemoral cartilage was also assessed according to the modified Outerbridge grading system.

RESULTS

The study included 20 symptomatic patients (13 women and 7 men; mean age, 36 ± 12.8 years) and 10 asymptomatic subjects (3 women and 7 men; mean age, 33.1 years). The mean time to perform the dynamic component ranged from 3 to 7 minutes. Lateralization in the symptomatic group was normal in 10 patients, mild in 1, moderate in 8, and severe in 1. There was no lateral tracking greater than 3 mm in the volunteer group. Lateral maltracking was significantly higher in symptomatic patients than in asymptomatic subjects (4.4 ± 3.7 mm vs 1.5 ± 0.71 mm, P = .007). Lateral tracking significantly correlated with tibial tubercle-trochlear groove distance (r = 0.48, P = .006). There was excellent agreement on lateral tracking between the 2 reviewers (intraclass correlation coefficient, 0.979; 95% confidence interval, 0.956-0.990).

CONCLUSIONS

The inclusion of a dynamic radial 2-dimensional GRE sequence is a rapid and easily performed addition to the standard magnetic resonance imaging protocol and allows dynamic quantitative assessment of patellar instability and lateral maltracking in symptomatic patients. With a paucity of reported data using this technique confirming that these results reach clinical significance, future work is required to determine how much lateral tracking is clinically significant.

LEVEL OF EVIDENCE

Level III, case control.

Dynamic MRI to quantify musculoskeletal motion: A systematic review of concurrent validity and reliability, and perspectives for evaluation of musculoskeletal disorders

Purpose

To report evidence for the concurrent validity and reliability of dynamic MRI techniques to evaluate in vivo joint and muscle mechanics, and to propose recommendations for their use in the assessment of normal and impaired musculoskeletal function.

Materials and methods

The search was conducted on articles published in Web of science, PubMed, Scopus, Academic search Premier, and Cochrane Library between 1990 and August 2017. Studies that reported the concurrent validity and/or reliability of dynamic MRI techniques for in vivo evaluation of joint or muscle mechanics were included after assessment by two independent reviewers. Selected articles were assessed using an adapted quality assessment tool and a data extraction process. Results for concurrent validity and reliability were categorized as poor, moderate, or excellent.

Results

Twenty articles fulfilled the inclusion criteria with a mean quality assessment score of 66% (±10.4%). Concurrent validity and/or reliability of eight dynamic MRI techniques were reported, with the knee being the most evaluated joint (seven studies). Moderate to excellent concurrent validity and reliability were reported for seven out of eight dynamic MRI techniques. Cine phase contrast and real-time MRI appeared to be the most valid and reliable techniques to evaluate joint motion, and spin tag for muscle motion.

Conclusion

Dynamic MRI techniques are promising for the in vivo evaluation of musculoskeletal mechanics; however results should be evaluated with caution since validity and reliability have not been determined for all joints and muscles, nor for many pathological conditions.

Correlation of 3D Shift and 3D Tilt of the Patella in Patients With Recurrent Dislocation of the Patella and Healthy Volunteers: An In Vivo Analysis Based on 3-Dimensional Computer Models

BACKGROUND

The concepts of lateral deviation and lateral inclination of the patella, characterized as shift and tilt, have been applied in combination to evaluate patellar malalignment in patients with patellar dislocation. It is not reasonable, however, to describe the 3-dimensional (3D) positional relation between the patella and the femur according to measurements made on 2-dimensional (2D) images.

PURPOSE

The current study sought to clarify the relation between lateral deviation and inclination of the patella in patients with recurrent dislocation of the patella (RDP) by redefining them via 3D computer models as 3D shift and 3D tilt.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Altogether, 60 knees from 56 patients with RDP and 15 knees from 10 healthy volunteers were evaluated. 3D shift and tilt of the patella were analyzed with 3D computer models created by magnetic resonance imaging scans obtained at 10° intervals of knee flexion (0°-50°). 3D shift was defined as the spatial distance between the patellar reference point and the midsagittal plane of the femur; it is expressed as a percentage of the interepicondylar width. 3D tilt was defined as the spatial angle between the patellar reference plane and the transepicondylar axis. Correlations between the 2 parameters were assessed with the Pearson correlation coefficient.

RESULTS

The patients' mean Pearson correlation coefficient was 0.895 ± 0.186 (range, -0.073 to 0.997; median, 0.965). In all, 56 knees (93%) had coefficients >0.7 (strong correlation); 1 knee (2%), >0.4 (moderate correlation); 2 knees (3%), >0.2 (weak correlation); and 1 knee (2%), <0.2 (no correlation). The mean correlation coefficient of the healthy volunteers was 0.645 ± 0.448 (range, -0.445 to 0.982; median, 0.834). A statistically significant difference was found in the distribution of the correlation coefficients between the patients and the healthy volunteers ( P = .0034). When distribution of the correlation coefficients obtained by the 3D analyses was compared with that by the 2D (conventional) analyses, based on the bisect offset index and patellar tilt angle, the 3D analyses showed statistically higher correlations between the lateral deviation and inclination of the patella ( P < .01).

CONCLUSION

3D shift and 3D tilt of the patella were moderately or strongly correlated in 95% of patients with RDP at 0° to 50° of knee flexion.

CLINICAL RELEVANCE

It is not always necessary to use both parameters when evaluating patellar alignment, at least for knees with RDP at 0° to 50° of flexion. Such a description may enable surgeons to describe patellar alignment more simply, leading to a better, easier understanding of the characteristics of each patient with RDP.

Statistical shape modeling predicts patellar bone geometry to enable stereo-radiographic kinematic tracking

Complications in the patellofemoral (PF) joint of patients with total knee replacements include patellar subluxation and dislocation, and remain a cause for revision. Kinematic measurements to assess these complications and evaluate implant designs require the accuracy of dynamic stereo-radiographic systems with 3D-2D registration techniques. While tibiofemoral kinematics are typically derived by tracking metallic implants, PF kinematic measurements are difficult as the patellar implant is radiotransparent and a representation of the resected patella bone requires either pre-surgical imaging and precise implant placement or post-surgical imaging. Statistical shape models (SSMs), used to characterize anatomic variation, provide an alternative means to obtain the representation of the resected patella for use in kinematic tracking. Using a virtual platform of a stereo-radiographic system, the objectives of this study were to evaluate the ability of an SSM to predict subject-specific 3D implanted patellar geometries from simulated 2D image profiles, and to formulate an effective data collection methodology for PF kinematics by considering accuracy for a variety of patient pose scenarios. An SSM of the patella was developed for 50 subjects and a leave-one-out approach compared SSM-predicted and actual geometries; average 3D errors were 0.45±0.07mm (mean±standard deviation), which is comparable to the accuracy of traditional segmentation. Further, initial imaging of the patella in five unique stereo radiographic perspectives yielded the most accurate representation. The ability to predict the remaining patellar geometry of the implanted PF joint with radiographic images and SSM, instead of CT, can reduce radiation exposure and streamline in vivo kinematic evaluations.

Relationship of Trochlear Morphology and Patellofemoral Joint Alignment to Superolateral Hoffa Fat Pad Edema on MR Images in Individuals with or at Risk for Osteoarthritis of the Knee: The MOST Study

Purpose To determine the relationship of patellofemoral joint alignment and trochlear morphology to superolateral Hoffa fat pad (SHFP) edema on magnetic resonance (MR) images in older adults with or at risk for osteoarthritis of the knee. Materials and Methods Institutional review board approval and written informed consent were obtained from all subjects. The Multicenter Osteoarthritis Study is a prospective cohort study of older adults with or at risk for osteoarthritis of the knee. Subjects were recruited from Birmingham, Alabama, and Iowa City, Iowa. In this cross-sectional study, patellofemoral joint alignment (bisect offset, patellar tilt angle, and Insall-Salvati ratio), trochlear morphology (sulcus angle, lateral and medial trochlear inclination, and trochlear angle) and SHFP edema were assessed on MR images of the knee. Measures of alignment and morphology were divided into quartiles, and SHFP was determined to be present or absent. Separate logistic regression models were used to determine the relationship of each measure of alignment and morphology to the presence of SHFP edema, with adjustments for age, sex, and body mass index. Results SHFP edema was present in 152 (13.4%) of the 1134 knees that were included. When compared with knees with measurements in the lowest quartile, knees with measurements in the highest quartile for trochlear angle, bisect offset, and Insall-Salvati ratios were 1.6 (95% confidence interval [CI]: 1.0, 2.6), 2.3 (95% CI: 1.3, 4.0), and 8.9 (95% CI: 4.7, 16.9) times more likely to show SHFP edema, respectively. No relationship was found between other measures and SHFP edema. Conclusion A more anterior trochlear facet, a more laterally displaced patella, and knees with patella alta were significantly associated with SHFP edema on MR images in subjects with or at risk for osteoarthritis of the knee. ^© RSNA, 2017.

Relationship between the Patellar Ridge and the Femoral Trochlea in the Patellar Tracking

OBJECTIVE

To investigate the anatomic morphology of the patellar ridge and how it matches the femoral trochlea in patellar tracking.

METHOD

We selected 40 volunteers, 20 males (age, 28 ± 5 years) and 20 female (age, 27 ± 6 years), who were completely asymptomatic with normal knee structures. We measured the right or left legs of volunteers, and the region from the distal femur to the tibial tuberosity was scanned by computed tomography (CT) with flexion at 0°, 30°, 60°, and 90°. CT data was reconstructed using image analysis software (Mimics). Variables such as the angle between the patellar ridge and patellar long axis, the tibial external rotation angle, as well as the best matching position between the patellar ridge and femoral trochlea at different knee flexion angles were measured. A single experienced orthopedic surgeon performed all the measurements, and the surgeon was blinded to the subject identifying information. We analyzed the differences between the various angles using a one-way analysis of variance. The differences between genders were analyzed using the t test.

RESULTS

The intraclass correlation coefficient (ICC) values were greater than 0.81 for all measurements, and the ICC value is almost in perfect agreement. The angle between the patellar ridge and the patellar long axis was 11.13° ± 4.1°. The angle in male participants was 10.87° ± 4.5° and it was 12.09° ± 3.7° in female participants. There were significant differences between each angle (0°, 30°, 60°, and 90°). The angles between the patellar ridge and femoral trochlear groove did not greatly increase with the knee flexion. The tibial internal rotation angle also showed a gradually increase at knee flexion of 0°-60°, and a gradually decrease at 60°-90°. The best-fit point between the patellar ridge and femoral trochlear groove gradually increased along with the knee flexion. There were no significant differences between male and female participants at all angles ( P < 0.05).

CONCLUSION

The anatomic morphology of the patellar ridge allows better matching between the patellar ridge and femoral trochlea during knee flexion, which is an important mechanism for the regulation of patellar tracking.

Upright weight-bearing CT of the knee during flexion: changes of the patellofemoral and tibiofemoral articulations between 0° and 120°

PURPOSE

To prospectively compare patellofemoral and tibiofemoral articulations in the upright weight-bearing position with different degrees of flexion using CT in order to gain a more thorough understanding of the development of diseases of the knee joint in a physiological position.

MATERIALS AND METHODS

CT scans of the knee in 0°, 30°, 60° flexion in the upright weight-bearing position and in 120° flexion upright without weight-bearing were obtained of 10 volunteers (mean age 33.7 ± 6.1 years; range 24-41) using a cone-beam extremity-CT. Two independent readers quantified tibiofemoral and patellofemoral rotation, tibial tuberosity-trochlear groove distance (TTTG) and patellofemoral distance. Tibiofemoral contact points were assessed in relation to the anteroposterior distance of the tibial plateau. Significant differences between degrees of flexion were sought using Wilcoxon signed-rank test (P < 0.05).

RESULTS

With higher degrees of flexion, internal tibiofemoral rotation increased (0°/120° flexion; mean, 0.5° ± 4.5/22.4° ± 7.6); external patellofemoral rotation decreased (10.6° ± 7.6/1.6° ± 4.2); TTTG decreased (11.1 mm ±3.7/-2.4 mm ±6.4) and patellofemoral distance decreased (38.7 mm ±3.0/21.0 mm ±7.0). The CP shifted posterior, more pronounced laterally. Significant differences were found for all measurements at all degrees of flexion (P = 0.005-0.037), except between 30° and 60°. ICC was almost perfect (0.80-0.99), except for the assessment of the CP (0.20-0.96).

CONCLUSION

Knee joint articulations change significantly during flexion using upright weight-bearing CT. Progressive internal tibiofemoral rotation leads to a decrease in the TTTG and a posterior shift of the contact points in higher degrees of flexion. This elucidates patellar malalignment predominantly close to extension and meniscal tears commonly affecting the posterior horns.

Effects of Patellofemoral Taping on Patellofemoral Joint Alignment and Contact Area During Weight Bearing

Study Design Controlled laboratory study. Background Although it has been theorized that patellofemoral joint (PFJ) taping can correct patellar malalignment, the effects of PFJ taping techniques on patellar alignment and contact area have not yet been studied during weight bearing. Objective To examine the effects of 2 taping approaches (Kinesio and McConnell) on PFJ alignment and contact area. Methods Fourteen female subjects with patellofemoral pain and PFJ malalignment participated. Each subject underwent a pretaping magnetic resonance imaging (MRI) scan session and 2 MRI scan sessions after the application of the 2 taping techniques, which aimed to correct lateral patellar displacement. Subjects were asked to report their pain level prior to each scan session. During MRI assessment, subjects were loaded with 25% of body weight on their involved/more symptomatic leg at 0°, 20°, and 40° of knee flexion. The outcome measures included patellar lateral displacement (bisect-offset [BSO] index), mediolateral patellar tilt angle, patellar height (Insall-Salvati ratio), contact area, and pain. Patellofemoral joint alignment and contact area were compared among the 3 conditions (no tape, Kinesio, and McConnell) at 3 knee angles using a 2-factor, repeated-measures analysis of variance. Pain was compared among the 3 conditions using the Friedman test and post hoc Wilcoxon signed-rank tests. Results Our data did not reveal any significant effects of either McConnell or Kinesio taping on the BSO index, patellar tilt angle, Insall-Salvati ratio, or contact area across the 3 knee angles, whereas knee angle had a significant effect on the BSO index and contact area. A reduction in pain was observed after the application of the Kinesio taping technique. Conclusion In a weight-bearing condition, this preliminary study did not support the use of PFJ taping as a medial correction technique to alter the PFJ contact area or alignment of the patella. J Orthop Sports Phys Ther 2017;47(2):115-123. doi:10.2519/jospt.2017.6936.

A knee brace alters patella position in patellofemoral osteoarthritis: a study using weight bearing magnetic resonance imaging

OBJECTIVE

To assess using weight bearing magnetic resonance imaging (MRIs), whether a patellar brace altered patellar position and alignment in patellofemoral joint (PFJ) osteoarthritis (OA).

DESIGN

Subjects age 40-70 years old with symptomatic and a radiographic Kellgren-Lawrence (K-L) evidence of PFJOA. Weight bearing knee MRIs with and without a patellar brace were obtained using an upright open 0.25 T scanner (G-Scan, Easote Biomedica, Italy). Five aspects of patellar position were measured: mediolateral alignment by the bisect offset index, angulation by patellar tilt, patellar height by patellar height ratio (patellar length/patellar tendon length), lateral patellofemoral (PF) contact area and finally a measurement of PF bony separation of the lateral patellar facet and the adjacent surface on the femoral trochlea (Fig. 1).

RESULTS

Thirty participants were recruited (mean age 57 SD 27.8; body mass index (BMI) 27.8 SD 4.2); 17 were females. Four patients had non-usable data. Main analysis used paired t tests comparing within subject patellar position with and without brace. For bisect offset index, patellar tilt and patellar height ratio there were no significant differences between the brace and no brace conditions. However, the brace increased lateral facet contact area (P = .04) and decreased lateral PF separation (P = .03).

CONCLUSION

A patellar brace alters patellar position and increases contact area between the patella and femoral trochlea. These changes would lower contact stress at the PFJ. Such changes in patella position in weight bearing provide a possible biomechanical explanation for the success of the PFJ brace in clinical trials on PFJOA.

Lower extremity rotational deformities and patellofemoral alignment parameters in patients with anterior knee pain

PURPOSE

Anterior knee pain is a common musculoskeletal condition amongst young adult population. Lower extremity structural factors, such as increased femoral anteversion and lateral tibial torsion, may contribute to patellofemoral malalignment and anterior knee pain. The aim of this study was to evaluate the lower extremity structural factors and related patellofemoral alignment parameters that play a role in the aetiology of anterior knee pain.

METHODS

This study involved three groups: patients with unilateral symptomatic knees (n = 35), asymptomatic contralateral knees in the same patients and a control group (n = 40). All subjects were physically examined, and Q-angles were measured. The lower extremities of all subjects were imaged by a very low-dose CT scan, and the symptomatic knees of patients were compared with their asymptomatic contralateral knees and with the healthy knees of controls regarding femoral anteversion, tibial torsion, sulcus angle, patellar tilt angle and lateral patellar displacement.

RESULTS

Regarding the Q-angle, femoral anteversion and lateral tibial torsion, no significant differences were found between the symptomatic and asymptomatic knees, whereas significant differences were found between the symptomatic knees and controls. The symptomatic group demonstrated significantly greater sulcus angle only in 30° of knee flexion than did the controls.

CONCLUSION

Patients with unilateral anterior knee pain may have similar morphology at their contralateral asymptomatic lower extremity, and different morphology compared with healthy controls. Lower extremity rotational deformities may increase the risk of anterior knee pain; however, these deformities alone are not sufficient to cause knee pain, and may be predisposing factor rather than a direct aetiology.

LEVEL OF EVIDENCE

Diagnostic study, Level III.

Influence of posterior lateral femoral condyle geometry on patellar dislocation

INTRODUCTION

Patellar instability is a condition with multifactorial aetiology, potentially involving soft tissue characteristics, the bony anatomy of the patella, femur and tibia, and alignment of the lower limb. The shape of the distal femur and patellofemoral joint has been frequently studied using plain orthogonal and skyline radiographs. We investigated a possible contribution of hypoplasia of the lateral femoral condyle in the axial plane to patellar instability.

METHODS

The geometry of the distal femur and alignment of the lower limb on plain radiographs and MRI scans in 25 young adult patients with patellar instability was measured, and compared to a control group of 75 age-matched patients. Measurements were validated by intra-observer and inter-observer reliability studies, and multivariate analysis was used to compare the groups. Cases with and without high Beighton score or knee hyperextension were also compared.

RESULTS

The anatomical posterior condylar angle, anterior condylar angle and sulcus angle on axial MRI scans showed insignificant differences between groups. The Blackburne-Peel ratio, anatomical femoro-tibial angle and femoral joint angle showed significant differences between groups, but not the tibial plateau angle. There was a significant correlation between posterior condylar angle and valgus knee alignment. In cases with joint hypermobility, femoral joint angle was significantly increased and posterior condylar angle was significantly decreased.

CONCLUSIONS

Multiplanar hypoplasia of the lateral femoral condyle resulting in a valgus knee is a risk factor for patellar instability in young patients without osteoarthritis or joint hypermobility. Isolated posterior lateral condyle hypoplasia appears to be unrelated to patellar instability.

Correlation Between Changes in Tibial Tuberosity-Trochlear Groove Distance and Patellar Position During Active Knee Extension on Dynamic Kinematic Computed Tomographic Imaging

PURPOSE

The purpose of this study was to evaluate changes in tibial tuberosity-trochlear groove (TTTG) distance with knee flexion in patients with patellar instability and correlate it with patellar position.

METHODS

Patients with symptomatic patellar instability underwent dynamic kinematic computed tomography (CT) during a cycle of knee extension from flexion. Knee flexion angles and corresponding TTTG distances, bisect offset, and patellar tilt were measured. Of the 51 knees, 37 had data available for interpolation between 5° and 30°. Results were interpolated to standardized intervals between 5° and 30° of knee flexion. Repeated-measures analysis (to identify differences between TTTG measurements at various knee flexion angles) and linear regression models (to assess for correlations between TTTG distance and bisect offset and between TTTG distance and patellar tilt) were used.

RESULTS

Fifty-one symptomatic knees in 38 patients were available for analysis. Bisect offset and patellar tilt correlated significantly (P < .001) with TTTG distance over all flexion angles. Interpolated results for comparison resulted in 37 knees in which the mean TTTG distance of 17.2 ± 5.8 mm at 5° decreased to 15.5 ± 5.7, 13.0 ± 5.5, and 11.5 ± 4.9 mm at 10°, 20°, and 30° of knee flexion, respectively. Mean TTTG at 5° was 1.5 times greater than that at 30° (P < .001). At 5°, 70.3% (26 of 37) of knees had a TTTG distance of more than 15 mm; at 30°, only 24.3% (9 of 37) exceeded this threshold.

CONCLUSIONS

Knee flexion angle during imaging is a critical factor when measuring TTTG distance to evaluate patellofemoral instability. We found that the mean TTTG distance varied by 5.7 mm between 5° and 30° of flexion in patients with symptomatic instability, although this relationship was not completely linear. Bisect offset and patellar tilt measurements mirrored this pattern, suggesting that TTTG distance influences patellar tracking in these patients.

LEVEL OF EVIDENCE

Level IV, prognostic case series.

Individuals with isolated patellofemoral joint osteoarthritis exhibit higher mechanical loading at the knee during the second half of the stance phase

BACKGROUND

Patellofemoral joint osteoarthritis is a highly prevalent disease and an important source of pain and disability. Nonetheless, biomechanical risk factors associated with this disease remain unclear. The purpose of this study was to compare biomechanical factors that are associated with patellofemoral joint loading during walking between individuals with isolated patellofemoral joint osteoarthritis and no osteoarthritis.

METHODS

MR images of the knee were obtained using a 3D fast-spin echo sequence to identify patellofemoral joint cartilage lesions. Thirty-five subjects with isolated patellofemoral joint osteoarthritis (29 females) and 35 control subjects (21 females) walked at a self-selected speed and as fast as possible. Peak knee flexion moment, flexion moment impulse and peak patellofemoral joint stress during the first and second halves of the stance phase were compared between groups.

FINDINGS

When compared to the controls, individuals with patellofemoral joint osteoarthritis demonstrated significantly higher peak knee flexion moment (P=.03, Eta(2)=.07), higher knee flexion moment impulse (P=.03, Eta(2)=.07) and higher peak patellofemoral joint stress (P=.01, Eta(2)=.10) during the second half of the stance phase. No significant group difference was observed during the first half of the stance phase.

INTERPRETATION

Findings of this study suggest that increased mechanical loading (i.e. knee flexion moment, impulse and patellofemoral joint stress) during the second half of the stance phase is associated with patellofemoral joint osteoarthritis. Prevention and rehabilitation programs for patellofemoral joint osteoarthritis may focus on reducing the loading on the patellofemoral joint, specifically during late stance.

The development, validation and internal consistency of the Norwich Patellar Instability (NPI) score

PURPOSE

No outcome measurements have previously been designed to assess patient-perceived patellar instability. The purposes of this study were to address this limitation and to describe the development and validation of the Norwich Patellar Instability (NPI) scores, a self-administered 19-item questionnaire to assess perceived patellar instability.

METHODS

A previous study assessed activities that aggravated symptoms in individuals with patellar dislocation and instability symptoms. These reported activities were ranked in order of severity, and a weighting system was calculated. The NPI score was introduced to routine clinical practice in three institutions. One hundred and two people who had experienced a lateral patellar dislocation completed 102 NPI questionnaires. The completed NPI score was correlated with the Knee injury and Osteoarthritis Outcome Score (KOOS) to evaluate divergent validity and with the J-sign, patellar mobility, apprehension test, Beighton score, Kujala Patellofemoral Disorder Score and Lysholm Knee Score to evaluate convergent validity. Internal consistency of the 19 items was also calculated.

RESULTS

The results indicated a moderate correlation between the NPI score and the Kujala Patellofemoral Disorder Score (rho = -0.66; p < 0.01) and Lysholm Knee Score (rho = -0.54; p = 0.03), suggesting good convergent validity. There was a little correlation between the KOOS and NPI score, indicating divergent validity (rho = -0.02 to -0.17; n.s.). There was high internal consistency (Cronbach's alpha = 0.93).

CONCLUSION

These results indicate the NPI score to be a valid tool to assess patellar instability for individuals following patellar dislocation. Further study is now required in order to assess the reliability and responsiveness of this new outcome measure.

Predictors of patellar alignment during weight bearing: an examination of patellar height and trochlear geometry

BACKGROUND

Patellar malalignment is thought to be an etiological factor with respect to the development of patellofemoral pain. Although previous studies have suggested that the geometry of the femoral trochlea and the height of the patella play an important role in determining patellar alignment, no investigation has systematically examined these relationships during weight bearing. The aim of this study was to determine whether patellar height and/or trochlear geometry predicts patellar alignment (lateral patellar displacement and lateral patellar tilt) during weight bearing.

METHODS

MR images of the patellofemoral joint were acquired from 36 participants during weight bearing (25% of body weight) at 4 knee flexion angles (0°, 20°, 40° and 60°). Using the axial images, patellar alignment (lateral displacement and tilt) and femoral trochlear geometry (sulcus angle and inclination of the lateral femoral trochlea) were measured. Patellar height (Insall-Salvati ratio) was measured on reconstructed sagittal plane images.

RESULTS

Stepwise regression analysis revealed that at 0° of knee flexion, the height of the patella was the best predictor of lateral patellar tilt while the lateral trochlea inclination angle was the best predictor of lateral patellar displacement. Lateral trochlear inclination was the best predictor of patellar lateral displacement and tilt at 20°, 40° and 60° of knee flexion.

CONCLUSION

Similar to a previous study performed under non-weight bearing condition, our findings suggest that lateral trochlear inclination is an important determinant of patellar alignment in weight bearing.

LEVEL OF EVIDENCE

Level III.

Association between measures of patella height, morphologic features of the trochlea, and patellofemoral joint alignment: the MOST study

BACKGROUND

Patellofemoral joint (PFJ) malalignment (lateral patella displacement and tilt) has been proposed as a cause of patellofemoral pain. Patella height and/or the morphologic features of the femoral trochlea may predispose one to patella malalignment.

QUESTIONS/PURPOSES

The purposes of our study were to assess the associations among patella height, morphologic features of the trochlea, and measures of PFJ alignment and to determine which measures of patella height and morphologic features of the trochlea were the best predictors of PFJ alignment.

METHODS

Measures of patella height (Insall-Salvati ratio and modified Insall-Salvati ratio), morphologic features of the trochlea (sulcus angle, trochlear angle, lateral trochlear inclination, medial trochlear inclination), and PFJ alignment (bisect offset and patella tilt angle) were assessed in 566 knees from the Multicenter Osteoarthritis Study.

RESULTS

Bisect offset was correlated with the Insall-Salvati ratio (r = 0.25) and lateral trochlear inclination (r = -0.38). Patella tilt angle correlated with the trochlear angle (-0.27) and lateral trochlear inclination (-0.32). Linear regression models including the Insall-Salvati ratio and lateral trochlear inclination explained 20% and 11% of the variance in bisect offset and patella tilt angle, respectively.

CONCLUSIONS

Of the variables measured in the current study, the Insall-Salvati ratio and lateral trochlear inclination were the best predictors of lateral patella displacement and lateral tilt. This knowledge will aid clinicians in the identification of anatomic risk factors for PFJ malalignment and/or PFJ dysfunction.

The patellofemoral kinematics in patients with untreated developmental dislocation of the hip suffering from patellofemoral pain

PURPOSE

This study reviews the dynamic patellofemoral CT results of 39 patients with untreated developmental dislocation of the hip who are suffering from knee pain.

METHOD

The mean age of the patients with unilateral developmental dislocation of the hip was 33.3 (±7.9), for bilateral patients 36.2 (±11.3), and for the control group, it was 31.5 (±8.5). While 14 of them were bilateral, 25 were unilateral. The CT results of 24 asymptomatic adult knees served as the control group. The patellofemoral parameters of patients with unilateral and bilateral developmental dislocation of the hip, the control group's parameters and the effect of femoral anteversion, limb length discrepancy, severity of dislocation, the mechanical axis deviation on patellofemoral parameters were analyzed.

RESULTS

In patients with unilateral untreated developmental dislocation of the hip, although the patella was located more laterally at initial flexion degrees, it was located more medially at 30° and 60° flexion with respect to the control group. For the involved extremity, the PTA angles at 15°, 30°, and 60° flexion were significantly higher than in the control group corresponding to medial patellar tilt. In patients with bilateral developmental dislocation of the hip, the course of the patella during tracking in terms of patellar shift was similar to that of the unilateral patients. The amount of leg length discrepancy and the severity of dislocation, as well as the mechanical axis deviation, did not affect the patellofemoral parameters.

CONCLUSION

The patients with untreated developmental dislocation of the hip and suffering from knee pain should be analyzed not only for tibiofemoral abnormalities but also for patellofemoral malalignment.

LEVEL OF EVIDENCE

Case-control study, Level III.

In vivo patellar tracking and patellofemoral cartilage contacts during dynamic stair ascending

The knowledge of normal patellar tracking is essential for understanding the knee joint function and for diagnosis of patellar instabilities. This paper investigated the patellar tracking and patellofemoral joint contact locations during a stair ascending activity using a validated dual-fluoroscopic imaging system. The results showed that the patellar flexion angle decreased from 41.9° to 7.5° with knee extension during stair ascending. During first 80% of the activity, the patella shifted medially about 3.9 mm and then slightly shifted laterally during the last 20% of the ascending activity. Anterior translation of 13 mm of the patella was measured at the early 80% of the activity and the patella slightly moved posteriorly by about 2mm at the last 20% of the activity. The path of cartilage contact points was slightly lateral on the cartilage surfaces of patella and femur. On the patellar cartilage surface, the cartilage contact locations were about 2mm laterally from heel strike to 60% of the stair ascending activity and moved laterally and reached 5.3mm at full extension. However, the cartilage contact locations were relatively constant on the femoral cartilage surface (∼5mm lateral). The patellar tracking pattern was consistent with the patellofemoral cartilage contact location pattern. These data could provide baseline knowledge for understanding of normal physiology of the patellofemoral joint and can be used as a reference for clinical evaluation of patellofemoral disorders.

Joint mechanics measurement using magnetic resonance imaging

Magnetic resonance imaging-based methods for measuring the mechanics of human joints have been successfully applied to quantitatively evaluate biomechanics in a wide variety of joints, pathologies, and interventions. The objective of this review was to provide a detailed overview of methods in the literature for measuring joint kinematics, meniscal and ligament movement, and cartilage strain using MRI.

The effects of quadriceps strengthening on pain, function, and patellofemoral joint contact area in persons with patellofemoral pain

OBJECTIVE

Patellar malalignment is a major cause of patellofemoral pain syndrome (PFPS), but the relationship between clinical symptoms and changes in patellar position and knee muscle strength has not been confirmed. This study examined the effect of weight training on hip and knee muscle strength, patellofemoral joint contact area, and patellar tilt on subjects with and without PFPS, hoping to develop an optimal rehabilitation protocol for subjects with PFPS.

DESIGN

The study uses a prospective independent group comparison. Fifteen subjects with and without PFPS were assessed for knee strength, patellofemoral joint contact area, and patellar tilt angle using magnetic resonance imaging. The subjects with PFPS were also examined and given a numeric pain rating score and a Kujala patellofemoral score. The subjects performed lower-limb weight training 3 times/wk for 8 wks, and the outcomes were assessed both before and after training.

RESULTS

Subjects with PFPS have increased their patellofemoral joint contact area after weight training (P < 0.001). No statistical significant change was found on the patellar tilt angle. The isometric and isokinetic knee strength in subjects with and without PFPS have increased after weight training (P value increased from 0.007 to 0.05). Both numeric pain rating and Kujala patellofemoral score in the PFPS group improved after training (P < 0.001).

CONCLUSIONS

Weight-training exercise increased knee muscle strength and the patellofemoral joint contact area, which could reduce mechanical stress in the joint, improving pain and function in subjects with PFPS.

Future trends in the use of X-ray fluoroscopy for the measurement and modelling of joint motion

Knowledge of three-dimensional skeletal kinematics during functional activities such as walking, is required for accurate modelling of joint motion and loading, and is important in identifying the effects of injury and disease. For example, accurate measurement of joint kinematics is essential in understanding the pathogenesis of osteoarthritis and its symptoms and for developing strategies to alleviate joint pain. Bi-plane X-ray fluoroscopy has the capacity to accurately and non-invasively measure human joint motion in vivo. Joint kinematics obtained using bi-plane X-ray fluoroscopy will aid in the development of more complex musculoskeletal models, which may be used to assess joint function and disease and plan surgical interventions and post-operative rehabilitation strategies. At present, however, commercial C-arm systems constrain the motion of the subject within the imaging field of view, thus precluding recording of motions such as overground gait. These fluoroscopy systems also operate at low frame rates and therefore cannot accurately capture high-speed joint motion during tasks such as running and throwing. In the future, bi-plane fluoroscopy systems may include computer-controlled tracking for the measurement of joint kinematics over entire cycles of overground gait without constraining motion of the subject. High-speed cameras will facilitate measurement of high-impulse joint motions, and computationally efficient pose-estimation software may provide a fast and fully automated process for quantification of natural joint motion.

The effect of a patellar brace on three-dimensional patellar kinematics in patients with lateral patellofemoral osteoarthritis

OBJECTIVE

Patellar bracing is a mechanical treatment strategy for patellofemoral osteoarthritis (OA) that aims to unload the lateral compartment of the joint by translating the patella medially. Our objective was to determine whether a patellar brace can correct patellar kinematics in patients with patellofemoral OA.

DESIGN

We assessed the effect of a patellar brace on three-dimensional patellar kinematics (flexion, spin and tilt; proximal, lateral and anterior translation) at sequential, static knee postures, using a validated magnetic resonance imaging (MRI)-based method, in 19 patients with radiographic lateral patellofemoral OA. Differences in kinematics between unbraced and braced conditions were assessed in the unloaded and loaded knee (15% bodyweight load) using hierarchical linear random-effects models. Random slope and quadratic terms were included in the model when significant (P<0.05).

RESULTS

Bracing with load caused the patellae to translate 0.46 mm medially (P<0.001), tilt 1.17° medially (P<0.001), spin 0.62° externally (P=0.012) and translate 1.09 mm distally (P<0.001) and 0.47 mm anteriorly (P<0.001) over the range of knee flexion angles studied. Bracing also caused the patellae to extend in early angles of knee flexion (P<0.001). The brace caused similar trends for the unloaded condition, though magnitudes of the changes varied.

CONCLUSION

Bracing changed patellar kinematics, but these changes did not appear large enough to be clinically meaningful because no reduction in pain was observed in the parent study.

The role of patellar alignment and tracking in vivo: the potential mechanism of patellofemoral pain syndrome

PURPOSE AND METHOD

Lateral patellar malalignment and maltracking are commonly believed to be associated with patellofemoral pain. In the current review, a computerized and manual search of English-language articles was performed using multiple combinations of the following keywords: 'patellofemoral pain syndrome' or 'patellofemoral pain', and 'patellar alignment' or 'patellar tracking'. The role of patellar alignment and tracking in vivo is discussed via a review of papers regarding the differences in asymptomatic and symptomatic patella. An attempt is made to identify the potential mechanism of patellofemoral pain syndrome (PFPS).

CONCLUSION

Evidence suggests that symptomatic patella do not consistently demonstrate lateral malalignment or tracking in patellar tilt and translation. Abnormal patellar alignment and tracking may be potential risk factors that are associated with patellofemoral pain. Other contributing factors should be considered in dealing with patellofemoral pain syndrome. Further studies are required to determine what normal patella alignment and tracking is before going on to define how these are altered in subjects with patellofemoral pain. Furthermore, prospective studies are needed to identify the alteration of patellofemoral kinematics, if any, and whether these are the causative factor or the consequence of the patellofemoral pain syndrome, as well as to determine the risk of development of patellofemoral pain syndrome in individuals with and without abnormal patellar tracking.

A systematised MRI approach to evaluating the patellofemoral joint

Knee pain in young patients is a common indication for knee MRI. Many static and dynamic internal derangements of the patellofemoral joint in these patients lead to various secondary MRI findings. This article focuses on how to systematically approach, detect, and emphasize the importance of these findings in the diagnosis of patellofemoral tracking and impingement syndromes with relevant case examples.

Case report: Quantitative MRI of tibial tubercle transfer during active quadriceps contraction

BACKGROUND

The evaluation of distal transfer procedures relies primarily on qualitative clinical findings. Although quantitative MRI measurements provide an objective supplement to qualitative clinical findings, an association between qualitative clinical findings and quantitative patellofemoral indices has yet to be established.

CASE DESCRIPTION

A 21-year-old man presented with frequent episodes of patellar dislocation. Clinical and radiographic findings identified the patient as a candidate for realignment. MR images were obtained with the quadriceps contracted at 30° flexion and in full extension preoperatively and postoperatively. The procedure eliminated the clinical J-sign, defined as lateral movement of the patella over the lateral femoral condyle during active leg extension, which was confirmed quantitatively using established patellofemoral indices in conjunction with MRI.

LITERATURE REVIEW

Movement of the patellofemoral joint is complex and dependent on many factors, including skeletal geometry, dynamic muscle action, and soft tissue restraints. Therefore, proper clinical and radiographic evaluation of patellar tracking requires observation during active quadriceps contraction. However, it is unclear whether there is any association between quantitative radiographic indices and qualitative clinical assessment during active quadriceps contraction.

PURPOSES AND CLINICAL RELEVANCE

We believe objective measurements are valuable in determining the radiographic assessment of patellar realignment procedures. Lateral patellar edge appears to quantify the clinical J-sign. The association between radiographic medialization of the patella and clinical improvement postoperatively in this patient warrants additional investigation in a larger group of patients with longer followup.

Association between patella alta and the prevalence and worsening of structural features of patellofemoral joint osteoarthritis: the multicenter osteoarthritis study

OBJECTIVE

To examine the relationship between patella alta and the prevalence and worsening at followup of structural features of patellofemoral joint (PFJ) osteoarthritis (OA) on magnetic resonance imaging (MRI).

METHODS

The Multicenter Osteoarthritis Study is a cohort study of persons ages 50-79 years with or at risk for knee OA. Patella alta was measured using the Insall-Salvati ratio (ISR) on the baseline lateral radiograph, and cartilage damage, bone marrow lesions (BMLs), and subchondral bone attrition (SBA) were graded on MRI at baseline and at 30 months of followup in the PFJ. We examined the association of the ISR with the prevalence and worsening of cartilage damage, BMLs, and SBA in the PFJ using logistic regression.

RESULTS

A total of 907 knees were studied (mean age 62 years, body mass index 30 kg/m(2), ISR 1.10), 63% from female subjects. Compared with knees in the lowest ISR quartile at baseline, those in the highest quartile had 2.4 (95% confidence interval [95% CI] 1.7-3.3), 2.9 (95% CI 2.0-4.3), and 3.5 (95% CI 2.3-5.5) times the odds of having lateral PFJ cartilage damage, BMLs, and SBA, respectively, and 1.5 (95% CI 1.1-2.0), 1.3 (95% CI 0.9-1.8), and 2.2 (95% CI 1.4-3.4) times the odds of having medial PFJ cartilage damage, BMLs, and SBA, respectively. Similarly, those with high ISRs were also at risk for worsening of cartilage damage and BMLs over time than those with low ISRs.

CONCLUSION

A high ISR, indicative of patella alta, is associated with structural features of OA in the PFJ. Additionally, the same knees have an increased risk of worsening of these same features over time.

Patellofemoral joint kinematics: the circular path of the patella around the trochlear axis

Differing descriptions of patellar motion relative to the femur have resulted from previous studies. We hypothesized that patellar kinematics would correlate to the trochlear geometry and that differing descriptions could be reconciled by accounting for differing alignments of measurement axes. Seven normal fresh-frozen knees were CT scanned, and their kinematics with quadriceps loading was measured by an optical tracker system. Kinematics was calculated in relation to the femoral epicondylar, anatomic, and mechanical axes. A novel trochlear axis was defined, between the centers of spheres best fitted to the medial and lateral trochlear articular surfaces. The path of the center of the patella was circular and uniplanar (root-mean-square error 0.3 mm) above 16+/-3 degrees (mean+/-SD) knee flexion. In the coronal plane, this circle was aligned 6+/-2 degrees from the femoral anatomical axis, close to the mechanical axis alignment. It was 91+/-3 degrees from the epicondylar axis, and 88+/-3 degrees from the trochlear axis. In the transverse plane it was 91+/-3 degrees and 88+/-3 degrees from the epicondylar and trochlear axes, respectively. Manipulation of the data to different axis alignments showed that differing previously published data could be reconciled. The circular path of patellar motion around the trochlea, aligned with the mechanical axis of the leg, is easily visualized and understood.

The effect of load magnitude on three-dimensional patellar kinematics in vivo

Studies of three-dimensional patellar kinematics done with little or no applied load may not accurately reflect kinematics at physiological load levels, and may provide different results to those acquired with greater applied loads or in physiologic weightbearing. We report the effect of load magnitude on three-dimensional patellar kinematics (flexion, spin and tilt; proximal, lateral and anterior translation) using a validated, sequential static, MRI-based method. Ten healthy subjects loaded their study knee to 0% (no load), 15% and 30% bodyweight (BW) using a custom designed loading rig. Differences between loading levels were determined as a function of knee flexion for each kinematic parameter using linear hierarchical random-effects models. Quadratic and random slope terms were included in the models when significant. We found that the patellae flexed less with knee flexion at 30% BW load compared to 0% BW load (p<0.001) and 15% BW (p=0.004) load. The patellae showed a slight medial tilt with knee flexion at 30% BW load which was significantly less than the medial tilt seen at 0% BW load (p=0.017) and 15% BW load (p=0.043) with knee flexion. Small but statistically significant differences were also observed for proximal and anterior translation; the patellae were in a more proximal and posterior position at 30% BW load than at 0% BW load (p=0.010 and p=0.005, respectively) and 15% BW load (p<0.001 and p=0.029, respectively). Since differences in three-dimensional patellar kinematics were observed between loading levels, magnitudes of prescribed loads must be considered when designing studies and comparing results between studies.

A single measure of patellar kinematics is an inadequate surrogate marker for patterns of three-dimensional kinematics in healthy knees

Patellofemoral disorders, such as osteoarthritis and patellofemoral pain, are thought to be associated with abnormal patellar kinematics. However, assessments of three-dimensional patellar kinematics are time consuming and expensive. The aim of this study was to determine whether a single static measure of three-dimensional patellar kinematics provides a surrogate marker for three-dimensional patellar kinematics over a range of flexion angles. We assessed three-dimensional patellar kinematics (flexion, tilt and spin; lateral, anterior and proximal translation) at sequential static angles through approximately 45 degrees of loaded knee flexion in 40 normal subjects using a validated, MRI-based method. The surrogate marker was defined as the static measure at 30 degrees of knee flexion and the pattern of kinematics was defined as the slope of the linear best fit line of each subject's kinematic data. A regression model was used to examine the relationship between the surrogate marker and pattern of kinematics. The surrogate marker predicted 26% of the variance in pattern of patellar flexion (p<0.001), 27% of the variance in pattern of patellar spin (p=0.003), 11% of the variance in pattern of proximal translation (p=0.037) and 39% of the variance in pattern of anterior translation (p<0.001). No relationships were seen between the surrogate marker and tilt or lateral translation. The results suggest that a single measure of patellar parameters at 30 degrees knee flexion is an inadequate surrogate marker of three-dimensional patellar kinematics; therefore, a complete assessment of patellar kinematics, over a range of knee flexion angles, is preferable to adequately assess patterns of patellar kinematics.

Clinical feasibility of a magnetic resonance tracking system to guide the position of the scan plane during physiologic joint motion

PURPOSE

Unrestricted physiologic joint motion results in multidirectional displacement of the anatomic structures. When performing real-time magnetic resonance (MR) imaging of such a joint motion, continuous adjustment of the scan plane position may be required. The purpose of this study was to evaluate the clinical feasibility of a method to guide the scan plane position during dynamic-motion MR imaging of freely moving joints.

MATERIALS AND METHODS

The location of a small tracker device (dedicated hardware) placed on the patient's skin overlying a joint was determined by an ultrashort MR sequence and used to automatically adjust the scan plane position prior to each dynamic-motion MR image. Using a vertically open MR unit, this MR tracking system was applied in ten dynamic-motion MR examinations to evaluate flexion/extension manoeuvres in the weight-bearing knee joint, and in ten dynamic-motion MR examinations of the shoulder joint to evaluate manoeuvres such as internal/external rotation of the humerus, stress testing of the glenohumeral joint and abduction/adduction manoeuvres. Average number of manoeuvre repetitions, total number of images and percentage of useful images per manoeuvre were calculated. Imaging time per scan plane for each manoeuvre was recorded.

RESULTS

Average repetition of manoeuvres varied between 1.6 and 5.8, with an average number of 7 to 18 images per manoeuvre. Average percentage of useful images varied between 61% and 89%. Total imaging time per scan plane ranged between 1 min 10 s and 4 min 51 s.

CONCLUSIONS

The MR tracking system to guide the slice position for each consecutive dynamic-motion MR image of the freely but slowly moving shoulder or knee joint was feasible for clinical use, providing a high percentage of useful images for each manoeuvre within a clinically acceptable time frame.