A technique for the measurement of patellar tracking during weight-bearing activities using ultrasound

Reliability and validity of quantitative ultrasound for evaluating patellar alignment: A pilot study

BACKGROUND

Patellar malalignment is a risk factor of patellofemoral pain. Evaluation of the patellar alignment have mostly used magnetic resonance imaging (MRI). Ultrasound (US) is a non-invasive instrument that can quickly evaluate patellar alignment. However, the method for evaluating patellar alignment via US has not been established. This study aimed to investigate the reliability and validity of evaluating patellar alignment via US.

METHODS

The sixteen right knees were imaged via US and MRI. US images were obtained at two sites of the knee to measure US-tilt as the index of patellar tilt. Using a single US image, we measured US-lateral distance and US-angle as the index of patellar shift. All US images were obtained three times each by two observers to evaluate reliabilities. Lateral patellar angle (LPA), as the indicators of patellar tilt, and lateral patella distance (LPD) and bisect offset (BO), as the indicators of patellar shift, were measured via MRI.

RESULTS

US measurements provided high intra- (within-day and between days) and interobserver reliabilities with exception of interobserver reliability of US-lateral distance. Pearson correlation coefficient indicated that US-tilt is significantly positively correlated with LPA (r = 0.79), and US-angle is significantly positively correlated with LPD (r = 0.71) and BO (r = 0.63).

CONCLUSION

Evaluating patellar alignment via US showed high reliabilities. US-tilt and US-angle showed moderate to strong correlation with MRI indices of patellar tilt and shift via MRI, respectively. US methods are useful for evaluating accurate and objective indices of patellar alignment.

Physical Examination and Patellofemoral Pain Syndrome: an Updated Review

PURPOSE OF REVIEW

Patellofemoral pain syndrome (PFPS) accounts for 25 to 40% of all knee disorders. Diagnosis of PFPS is primarily based on history and physical examination, but the findings on physical examination are often subtle and do not consistently correlate with symptoms described. Yoon and Fredericson published a review article in 2006 detailing the physical examination maneuvers most frequently used to assist clinicians in the accurate diagnosis and treatment of PFPS, and our aim in this review is to provide an update on this previous article focusing on the literature published over the past 15 years regarding the topic.

RECENT FINDINGS

Since publication of Fredericson's original review article, there have been studies building on the literature specifically surrounding Q angle, patellar tilt, crepitus, strength and functional testing, and physical examination maneuver clustering. Additionally, multiple studies have been conducted on the use of musculoskeletal ultrasound (US) as a diagnostic tool for PFPS. Recent literature has further supported Q angle (when measured utilizing a standardized protocol), crepitus, weakness of hip abductors and extensors, and weakness detected in functional testing as predictors of PFPS while finding inconsistent evidence behind lateral patellar tilt as a predictor of PFPS. The reliability of most physical examination tests alone remain low, but clustering physical examination findings may provide better sensitivities and specificities in diagnosing PFPS. Musculoskeletal US is rapidly gaining popularity, and decreased vastus medialis obliquus (VMO) volume, asymmetry in gluteus medius thickness, intra-articular effusions, and quadriceps and patellar tendon thicknesses have shown value in diagnosing those with PFPS. Additionally, US has the advantage of providing dynamic examination as well as evaluation of the patellofemoral joint in newborns and infants as a predictor of future patellofemoral instability. Further studies are needed to establish the gold standard for diagnosing PFPS and what US findings are truly predictive of PFPS.

Intrarater reliability of measuring the patella position by ultrasonography in weight-bearing condition

[Purpose] The aim of this study was to determine the intrarater reliability of using ultrasonography as a measurement tool to assess the patella position in a weight-bearing condition. [Subjects and Methods] Ten healthy adults participated in this study. Ultrasonography was used to assess the patella position during step down with the loading knee in flexion (0° and 20°). The distance between the patella and lateral condyle was measured to represent the patella position on the condylar groove. Two measurements were obtained on the first day and the day after 1 week by the same investigator. [Results] Excellent intrarater reliability, ranging from 0.83 to 0.93, was shown in both conditions. Standard errors of the measurements were 0.5 mm in the straight knee and 0.7 mm in the knee flexion at 20°. Minimal differences in knee flexion at 0° and knee flexion at 20° were 1.5 mm and 1.9 mm, respectively. [Conclusion] Ultrasonography is a reliable assessment tool for evaluating the positional changes of the patella in weight-bearing activities, and it can be easily used by practitioners in the clinical setting.

The effect of patellar taping on patellar position measured using ultrasound scanning

Previous research into the effect of patellar taping has found conflicting results and when studies have found positive findings these effects appear to be negated by exercise. The purpose of this study was to re-examine the effect of patellar taping on patellar position using ultrasound scanning. Twelve asymptomatic subjects (six males and six females (age 20.4+/-1.2 years)) had their patellar position examined, prior to and following the application of tape, and also following exercise (25 step ups). Mean patellar position (distance border patella to edge lateral femoral condyle) prior to application of tape was 6.2+/-1.3 mm following the application of tape mean patellar position was 7.9+/-1.7 mm, this was a statistically significant change in position (p=0.003). Following exercise mean patellar position was 7.6+/-1.7 mm this was a significant reduction compared to the taped position prior to exercise (p=0.001). This value was though still significantly greater than prior to the application of tape (p=0.006). This study found that patellar position was significantly changed following the application of tape. Furthermore, the study found that though low intensity exercise resulted in a significant change in the patellar position compared to the taped position prior to exercise, that change was most likely to have occurred due to random chance or measurement error.

A novel method for measuring electromechanical delay of the vastus medialis obliquus and vastus lateralis

Electromechanical delay (EMD) of the vastus medialis obliquus (VMO) and vastus lateralis (VL) is determined by measuring the interval between the time of onset of muscle activities and the time of onset of mechanical output. However, individual mechanical output of the VMO or the VL cannot be obtained with the conventional method because of the knee extension force as the mechanical output. Therefore, the objective of the present study was to develop a new method for measuring EMD of the VMO and VL individually. Twelve healthy volunteers participated in the experiment. The motor point of the target muscle was electrically stimulated to evoke a muscle twitch. Simultaneously, the electrical stimulation signal was transmitted to ultrasound apparatus via the electrocardiography input channel. The ultrasound apparatus was used to capture the patellar movement elicited by the muscle twitch. EMD was measured from the onset of the electrical stimulation to the onset of patellar movement. The results showed that the intraclass correlation coefficients for the reproducibility of the EMD measurements of the VMO and VL were greater than 0.8. The EMDs of the VMO and VL were 18.3 +/- 2.2 ms and 24.8 +/- 5.8 ms, respectively. This new method provides a more precise measurement of EMD in the VMO and VL than does the conventional method because of the use of patellar movement as the mechanical output.

The applicability of ultrasound imaging in the assessment of dynamic patella tracking: a preliminary investigation

The purpose of the study was to examine the effect of muscle stimulation of the Vastus Medialis Oblique (VMO) and Vastus Laterialis (VL) muscles on patella position in-vivo assessed by ultrasound scanning. Also to assess the reliability of the technique used. The position of the patella was measured using B-Mode, real time ultrasonography prior to and following the electrical stimulation of the VMO and VL muscles in 10 asymptomatic subjects. Maximal (tetanic) contraction of VMO brought about a mean medially displacement of the patella of 6.8+/-2.9 mm and VL a mean lateral displacement of 5.6+/-2.7 mm. The between repetition variation of displacement generated on muscle stimulation was assessed, results demonstrating a strong correlation between repetitions r=0.85 and 0.87 (p<0.01), for medial and lateral displacement respectively. The stimulation of either muscle (VMO or VL) brought about a consistent movement of the patella either medially for VMO or laterally for VL again demonstrating the reliability of the technique. The study found the reliability of the ultrasound technique to be good, reflecting those of previous studies which have used ultrasound to assess patella position.

CT changes after trochleoplasty for symptomatic trochlear dysplasia

Trochlear dysplasia is an important risk factor for patellar instability. Because of a decreased trochlear depth in combination with a low lateral femoral condyle, the patella cannot engage properly in the trochlea. Trochleoplasty is a surgical procedure, which strives to correct such bony abnormalities. The aim of this study was to describe morphological features of trochlear dysplasia and the corrective changes after trochleoplasty on CT scan. The study group consists of 17 knees with trochlear dysplasia having undergone trochleoplasty for recurrent patellofemoral dislocation at a mean age of 22.4 years. The evaluation consisted in pre- and postoperative measurements on the proximal and distal trochlea on transverse CT scans in order to determine the morphological features. We measured the transverse position and depth of the trochlear groove, the transverse position of the patella, the ratio between the posterior patellar edge and the trochlear groove, the lateral patellar inclination angle, the sulcus angle, and the lateral trochlear slope. The trochlear groove lateralised a mean of 6.1 mm in the proximal aspect and 2.5 mm in the distal aspect of the trochlea, while the patella medialised a mean of 5 mm. Preoperatively the patella was lateral in relation to the trochlear groove in 13 cases, neutral in two cases, and medial in two cases. Postoperatively it was lateral in four cases, in neutral position in seven cases, and medialised in six cases, referenced to the trochlear groove. The trochlear depth increased from 0 to 5.9 mm postoperatively in the proximal aspect of the trochlea, and from 5.5 to 8.3 mm postoperatively in the distal trochlea. The lateral patellar inclination angle decreased from a mean of 21.9 degrees to a mean of 7.8 degrees . The sulcus angle decreased from a mean of 172.1 degrees to a mean of 133 degrees in the proximal trochlea and from a mean of 141.9 degrees to a mean of 121.7 degrees in the distal trochlea. The lateral trochlear slope changed from 2.8 degrees to 22.7 degrees in the proximal and from 14.9 degrees to 26.9 degrees in the distal part of the trochlea. In the CT scan patients with trochlear dysplasia demonstrated a poor depth, or even a flat or convex trochlea with a greater sulcus and lateral trochlear slope angle, a lateralised patella to the trochlear groove with poor congruency, and a greater lateral patellar inclination angle. Trochleoplasty can correct the pathological features of trochlear dysplasia by surgically creating more normal anatomy. The goal of this surgical procedure is to steepen and lateralise the trochlear groove for a better engagement of the patella.

Quantification of patella position by ultrasound scanning and its criterion validity

Altered position of the patella has been associated with patellofemoral joint pain. The main techniques used for assessment of position are either expensive or invasive; there are limited reports of the use of ultrasound (US) scanning to assess patella position. The aim of this study was to establish the validity of a measure of patella position using US scanning compared with those found using magnetic resonance imaging (MRI). MRI and US scans were taken of 20 subjects and analyzed using previously described methods. The correlation between patella position assessed by US scan and lateral patella displacement on MRI showed a good statistically significant correlation (r = 0.64, p = 0.003). The correlation between the patella position assessed by US scan and the equivalent measure on MRI showed an excellent statistically significant correlation (r = 0.78, p = 0.0001). The method described has shown US scanning to be a reliable measure of patella position, with strong criterion validity compared with MRI measures.

Active patellar tracking measurement: a novel device using ultrasound

BACKGROUND

Many patients suffer patellar instability that may relate to transient patellar tracking abnormalities.

OBJECTIVE

To develop and test a technique to measure dynamic patellar tracking.

STUDY DESIGN

Controlled laboratory and in vivo study.

METHOD

A functional knee brace was modified to allow an ultrasound transducer to be mounted laterally to the femur, following the path of the patella during knee movement. An ultrasound system was used to measure patellar mediolateral position parallel to the femoral transepicondylar axis. Ten subjects with no patellar instability were studied to obtain patellar tracking and accuracy data.

RESULTS

The interobserver and intraobserver reproducibility ranged from 0.2 +/- 0.1 mm to 1.0 +/- 0.5 mm. The accuracy of the ultrasound measurement was checked against magnetic resonance imaging and was 0.6 +/- 1.9 mm. The patella moved medially then laterally from extension to flexion when sitting. Squatting and stepping produced a more lateral path, without the initial medial translation. The patella was more lateral during knee extension than during flexion.

CONCLUSIONS

This novel method for measurement of dynamic patellar mediolateral tracking was found to have good intraobserver and interobserver reproducibility, and the measurements matched closely with those obtained from magnetic resonance imaging reconstructions of static patellar positions. Some preliminary data for tracking in 3 activities were obtained from 10 normal knees.