Method Article

Identifying Frailty Using Point-of-Care Ultrasonography: Image Acquisition and Assessment

DOI:

10.3791/66803

⸱

July 26th, 2024

 ,  ,  ,  ,  ,  ,  , 
1Department of Anesthesiology and Critical Care Medicine, George Washington University, 2The George Washington University School of Medicine and Health Sciences Washington, 3Vanderbilt University Medical Center, 4Department of Anesthesiology, UVA Health, 5Department of Anesthesiology, Duke University School of Medicine, Duke University Health System

In This Article

Summary

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Here, we present a protocol to assess frailty in the perioperative setting using point-of-care ultrasound to measure quadriceps thickness. This method offers a practical, non-invasive alternative to traditional assessment methods, potentially enhancing perioperative care by quickly identifying frail patients.

Abstract

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Frailty is a significant predictor of a range of adverse outcomes in surgical patients, including increased mechanical ventilation time, longer hospital stays, unplanned readmissions, stroke, delirium, and death. However, accessible tools for screening in clinical settings are limited. Computed tomography of the psoas muscle is the current standard imaging device for measuring frailty, but it is expensive, time-consuming, and exposes the patient to ionizing radiation. Recently, the use of point-of-care ultrasound (POCUS) has emerged as a potential tool to determine the presence of frailty and has been shown to accurately predict frailty and postoperative outcomes. In this article, we will describe the image acquisition of the quadriceps muscles and explain how they can be used to determine frailty and predict postoperative adverse events. We will present information on probe selection, patient positioning, and troubleshooting. Images from a demonstration will be used to present the POCUS technique and example results. The article will culminate in a discussion of the use of these images in medical decision-making and potential limitations.

Introduction

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As the average life expectancy rises globally, an increasing number of surgeries are performed on patients over the age of 651. Frailty is more common in these patients compared with their younger counterparts and represents a state of physiological vulnerability to stressors, including surgery2,3,4. Frailty in the preoperative setting has been linked with a higher risk for postoperative adverse events across many surgical subspecialties5,6,7,8,9,10,11,12,13, including longer hospital length of stay10,14, loss of independence15,16, readmission rates17,18, increased costs14, and mortality10,18,19,20. Therefore, it is of utmost importance for the perioperative healthcare team to consider a patient's frailty during preoperative decision-making.

The most commonly used method to diagnose frailty includes the Fried frailty phenotype, which comprises five factors including exhaustion, weakness (measured by grip strength), slow walking pace, weight loss, and low physical activity levels21. However, this scale was designed primarily for outpatient services and may be too time-consuming in the perioperative setting. In addition, it requires patient cooperation and is impractical in a patient with altered mental status. Moreover, CT scans are used to assess muscle mass for sarcopenia diagnosis, which can aid in frailty assessment. However, while effective, CT scans present practical challenges in resource allocation and expose patients to ionizing radiation, especially in the perioperative period.22 Therefore, there is a need for bedside test that can quickly and accurately identify preoperative patients with diminished muscle mass, thus flagging those at higher surgical risk.

Recently, Canales et al. reported on a method for screening for frailty in the preoperative setting using point-of-care ultrasound23. They found that quadriceps muscle thickness accurately predicted frailty and was an independent predictor of postoperative discharge to a skilled nursing facility and delirium. The quadriceps muscle is located on the anterior thigh and is composed of four muscle bellies: the rectus femoris, the vastus medialis, vastus lateralis, and the vastus intermedius24. Using point-of-care ultrasound for frailty screening in the preoperative setting offers advantages over the Fried frailty assessment and CT imaging. Point-of-care ultrasound provides objective measures of physiologic parameters, such as muscle mass and quality, in real-time, allowing for immediate and non-invasive evaluation. This approach is more practical, efficient, and adaptable to patients who may not be able to undergo traditional assessment, enhancing perioperative risk stratification and improving outcomes23.

This paper will detail how to obtain the point-of-care ultrasound measurements of the quadriceps (including probe selection, patient positioning, and troubleshooting) and discuss the implications of this measurement in the perioperative setting.

Protocol

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

NOTE: The exams can be performed with either a low frequency curvilinear (2-5 MHz) or medium to high frequency linear probe (6-12 MHz) depending on patient body habitus, probe availability, and provider preference. For the figures and scans, a curvilinear probe (C35xp, SonoSite M-Turbo) was utilized.

1. Technique for quadriceps scanning

  1. Quadriceps depth measurement
    1. Patient positioning: Place the patient in a supine position (head of the bed elevated to 30o) with their legs extended.
    2. Probe selection: Select a low-frequency curvilinear or medium to high-frequency linear probe.
    3. Mode selection: Set the preset (i.e., exam type) on the scanner to musculoskeletal (MSK) setting.
    4. Probe placement:
      1. Place the probe transversely on the anterior thigh at approximately 60% the length from the anterior superior iliac spine (ASIS) to the superior border of the patella (Figure 1).
      2. With the probe perpendicular to the long axis of the muscles, the quadriceps will appear deep to the subcutaneous tissue and superficial to the femur.
      3. Use extra contact gel to minimize underlying soft tissue distortion.
    5. Image optimization:
      1. To prevent the overestimation of the muscle thickness due to superficial edema, apply firm pressure to the ultrasound probe without inflicting pain25.
      2. If any difficulty identifying the rectus femoris is encountered, ask the patient to contract their thigh muscles or extend their knee. The rectus femoris, being superficial and crossing the hip joint, will show a different movement pattern compared to the deeper vastus muscles (Supplementary Video 1).
    6. Measurement of quadriceps muscle thickness
      1. Activate the Caliper function of the ultrasound machine by pressing Measure on the ultrasound machine.
      2. Use the cursor to measure the anterior-to-posterior distance between (1) the deep border of the vastus intermedius (just superficial to the cortex of the femur) and (2) the most superficial fascia of the rectus femoris (Figure 2).
        NOTE: If there is any difficulty identifying the structures mentioned in 1.1.6.2, the steps mentioned in the Video 1 supplement can be repeated before activating the caliper function. The quadriceps muscle thickness is the sum of the muscle thickness of the rectus femoris and vastus intermedius (Figure 3).
    7. Image acquisition: click on Acquire to save a video clip of this sonographic view.
    8. Repeat measurement (steps 1.1.6-1.1.7) three times and average values to minimize variability.

2. Technique for rectus femoris scanning

  1. Rectus femoris cross-sectional area (CSA) measurement
    1. Patient positioning: follow step 1.1.1.
    2. Probe selection: follow step 1.1.2.
    3. Mode selection: follow step 1.1.3.
    4. Probe placement: follow step 1.1.4.
    5. Image optimization:
      1. Adjust the depth using the vertical ruler on the right side of the displayed scan. Adjust the gain using the horizontal slide bar at the bottom of the touch control panel so that the rectus femoris muscle is centered in the ultrasound frame with clear visualization of its boundaries and the underlying femur.
      2. Identify the rectus femoris muscle as a hypoechoic structure within the anterior thigh compartment, with a central echogenic line representing the intramuscular tendon.
      3. Activate the caliper function on the ultrasound machine and trace around the periphery of the rectus femoris muscle carefully to define its cross-sectional area. The ultrasound machine will calculate and display the CSA based on the tracing.
    6. Image acquisition: follow step 1.1.6.
    7. Repeat measurement three times and average values to minimize variability.
  2. Rectus Femoris Circumference Measurement
    1. Patient positioning: follow step 1.1.1.
    2. Probe selection: follow step 1.1.2.
    3. Mode selection: follow step 1.1.3.
    4. Probe placement: follow step 1.1.4
    5. Image optimization:
      1. Adjust the depth using the vertical ruler on the right side of the displayed scan. Adjust the gain using the horizontal slide bar at the bottom of the touch control panel so that the rectus femoris muscle is centered in the ultrasound frame with clear visualization of its boundaries and the underlying femur.
      2. Identify the rectus femoris muscle as a hypoechoic structure within the anterior thigh compartment, with a central echogenic line representing the intramuscular tendon.
      3. Activate the caliper function on the ultrasound machine and trace around the periphery of the rectus femoris muscle carefully to define its cross-sectional area. The ultrasound machine will calculate and display the circumference based on the tracing (Figure 4).
    6. Image acquisition: follow step 1.1.6.
    7. Repeat measurement three times and average values to minimize variability.

Results

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By implementing this protocol for measuring quadriceps muscle thickness using real-time ultrasound, it is possible to accurately assess frailty indicators. Following the steps outlined in this protocol, we positioned the patient and selected the appropriate ultrasound probe for optimal visualization of the quadriceps muscles.

The key to success in this technique is the precise placement of the probe on the anterior thigh at approximately 60% the length from the ASIS to the superior border of the patella with the probe perpendicular to the long axis of the muscles23 (Figure 1). This allows for clear and distinct images of the quadriceps muscles, facilitating accurate measurements of muscle thickness, CSA, and circumference. The ultrasound images captured during this process (Figure 2) clearly demonstrate the muscle structures, providing a reliable basis for measurement.

It is crucial to note the potential for variability in muscle thickness measurements related to probe pressure. Excessive pressure can compress the muscle, leading to underestimation, while insufficient pressure may not adequately delineate the muscle borders, causing overestimation (Figure 5). Therefore, maintaining consistent probe pressure is essential to ensure the accuracy of the measurements. Consistent probe pressure can be obtained by applying even pressure perpendicular to the skin surface using visual feedback from the ultrasound image to maintain uniform pressure throughout the examination.

In addition to applying appropriate pressure, it is crucial to position the probe in the correct position on the anterior thigh. If the sonographic image reveals the sartorius muscle, the probe is placed too medial on the thigh, and it is necessary to scan more laterally until the entire thickness of the rectus femoris can be visualized (Figure 3D).

Moreover, probe selection can also affect the measurements. A low frequency curvilinear (2-5 MHz) or medium to high frequency linear probe (6-12 MHz) can be used depending on patient body habitus, probe availability, and provider preference. For patients with a larger body habitus25, or for patients with substantial muscle hypertrophy24, it is generally advised to use a lower frequency probe, which has a higher depth penetration but lower resolution24,25. Therefore, if adequate resolution cannot be obtained with a lower frequency probe, switching to a higher frequency probe may be considered to optimize visualization.

While it is recommended to obtain ultrasonographic measurements of both extremities, it is not required, especially in patients who may have malformations or deformities in one lower extremity. This approach helps to minimize unnecessary discomfort for the patient and allows for a more focused evaluation of the affected limb. Furthermore, many published imaging protocols suggest that the patient should be lying supine with their legs fully extended to obtain the image, but the patient may be more comfortable lying with their back or head elevated during the study. If necessary, the patient may also lie in a decubitus position.

To account for variations in muscle mass composition due to gender, body size, and obesity, the raw ultrasound measurements can be indexed by dividing by the body surface area (BSA) and body mass index (BMI) for normalization. This standardization allows for comparison across different individuals with varying body habitus and muscle ratios23.

In our sample subject, the measurements of quadriceps depth and rectus femoris CSA and circumference revealed a muscle thickness consistent with non-frail status according to frailty cutoffs described in Canales et al (men: 20.5 kg (body mass index less than 24), 21.5 kg (body mass index of 24 to 26) and 23 kg (body mass index greater than 26); women: 11.5 kg (body mass index less than 23) and 13 kg (body mass index greater than 23), indicating that the patient was not at a heightened risk for frailty-related complications in the perioperative setting. For contrast, observe the poor muscular integrity in a patient that would classify as frail (Figure 6B). In this sonograph, the scanner will note more heterogeneous echotexture and potentially interrupted fascial planes, suggesting reduced muscle mass and quality.

In summary, this case study illustrates the steps for using point-of-care ultrasound for quadriceps muscle thickness measurement in elderly patients. The technique's ability to provide real-time, accurate visualization of muscle structures makes it a valuable tool for frailty assessment in the perioperative setting.

Leg edema analysis, patient leg with edema signs, arrows indicating swelling in clinical study.
Figure 1: Anatomical landmarks for quadriceps muscle scanning. With the patient supine on the bed, identify the external landmarks including the anterior superior iliac spine (upper blue arrow), the superior border of the patella (lower blue arrow), and optimal probe placement location (red arrow). Please click here to view a larger version of this figure.

Ultrasound imaging diagram; measuring anatomical structure; medical diagnostic process.
Figure 2: Ultrasonographic measurement of muscle anatomy. Once the appropriate cross-sectional image is ascertained (left), Use the calipers to measure the anterior-to-posterior distance between (1) the deep border of the vastus intermedius (just superficial to the cortex of the femur-green arrow) and (2) the most superficial fascia of the rectus femoris (red arrow). Please click here to view a larger version of this figure.

Ultrasound quadriceps cross-sections, labeled RF, VI, SQ, lateral, medial, muscle layer analysis.
Figure 3: Ultrasonographic assessment of muscle anatomy. (A,B) A cross sectional orientation of subcutaneous tissue (SQ), rectus femoris (RF) muscle, and vastus intermedius (VI) muscle, with the sartorius highlighted in blue. The anterior surface of the femur is highlighted in purple. (C,D) The scans depicts the RF more medially to the SQ and VI muscles, indicating the need to adjust the probe to scan more laterally. Note that Panels C and D are the incorrect location to perform the measurement of the quadriceps muscle. Please click here to view a larger version of this figure.

Ultrasound imaging, medical diagnostic, cross-section analysis, soft tissue examination, clinical result.
Figure 4: Ultrasonographic assessment of the Rectus Femoris (RF) muscle. (A) An incomplete visualization of the RF muscle, attributed to a superficial depth setting on the ultrasound device. (B) A complete visualization of the RF muscle, achieved by adjusting the depth setting to a deeper level. (C) The RF muscle with precise dimensions delineated: a cross-sectional area of 1.98 cm2 and a length measurement of 7.08 cm (orange arrow), as demarcated by the sonographic calipers.  Please click here to view a larger version of this figure.

Ultrasound measurements diagram, showing depth changes, labeled A-D, with distances in centimeters.
Figure 5: Variability in ultrasonographic muscle thickness measurements due to probe pressure. (A,B) The panels demonstrate the potential for measurement discrepancies of the rectus femoris, with values ranging from 0.78 cm to 1.00 cm. (C,D) The panels demonstrate the potential for measurement discrepancy of the combined measurement of the entire quadriceps muscle (the sum of the rectus femoris and the vastus intermedius), with values ranging from 1.57 cm to 2.25 cm. Applying excessive pressure can yield erroneously small measurements; applying inadequate pressure can yield erroneously large measurements. Please click here to view a larger version of this figure.

Ultrasound imaging; musculoskeletal analysis; horizontal vs vertical view; diagnostic application.
Figure 6: Ultrasound scans of healthy versus frail individuals. (A) A scan from a healthy individual, characterized by a well-defined muscle with uniform echotexture and clear, continuous fascial planes, indicative of good muscle quality and volume. (B) A scan from an elderly frail individual, where the muscle appears less defined with a more heterogeneous echotexture and potentially interrupted fascial planes, suggests reduced muscle mass and quality, which are common findings associated with frailty. Please click here to view a larger version of this figure.

Supplementary Video 1: A different movement pattern of the rectus femoris compared to the deeper vastus muscles. Please click here to download this File.

Discussion

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Previous studies have indicated that POCUS can be used to estimate muscle thickness, including the quadriceps muscle, with accuracy comparable to CT scans26,27,28. Sonographic measurement of quadriceps muscle thickness has been correlated with frailty and can be used to predict certain postoperative outcomes23. In addition, this method is helpful in situations where other methods of diagnosing frailty may be impractical, such as in the preoperative setting or in cases where the patient or provider is unable to participate in a lengthy examination.

A recent systematic review and meta-analysis conducted on the evaluation of appendicular muscle mass in sarcopenia in older adults using ultrasonography assessed ultrasonography's reliability and validity in assessing muscle mass in the elderly, particularly through the measurement of the thickness and cross-sectional area of rectus femoris or gastrocnemius muscles. The review found that these sonographic parameters accurately diagnosed sarcopenia, offering a non-invasive and effective tool for clinical assessment in geriatric populations29.

There are limitations to using POCUS to estimate preoperative frailty and predict postoperative outcomes. While sarcopenia and frailty are closely linked, sarcopenia alone may not be as predictive of postoperative mortality compared to a diagnosis of frailty30,31,32. This test utilizes muscle thickness to predict frailty-related outcomes, identifying only one part of the multisystem syndrome of frailty and cannot identify cognitive decline or other physical changes associated with the disorder. While the method described in this manuscript showed clinical utility in at least one clinical study23, muscle loss is known to vary by body shape, gender, and ethnicity33. Moreover, chronic conditions prevalent in different demographic groups can further complicate the applicability of the bedside assessment technique. Factors such as underlying health conditions, medication use, and varying levels of physical activity can influence muscle composition and thus impact the accuracy of the assessment. Therefore, larger-scale studies across different patient populations are needed to confirm the utility of this bedside assessment technique.

Operator error can also contribute to the limitations of this technique. Since there is a learning curve associated with this POCUS technique, strategies to mitigate operator variability to ensure accuracy and reliability must be established, such as standardizing training protocols, ongoing quality assurance measures, and proficiency assessments. These steps can enhance the reproducibility and validity of POCUS-based frailty assessments in diverse clinical settings.

To enhance the validation of POCUS in predicting long-term outcomes and its integration into clinical medicine, future research avenues should prioritize longitudinal studies assessing the correlation between sonographic measurements of muscle thickness and patient outcomes over extended periods. Such investigations would not only validate the efficacy of POCUS in identifying frailty but also elucidate its predictive power for postoperative morbidity and mortality in diverse patient populations. Additionally, studies focusing on the integration of POCUS into existing clinical protocols are crucial to establishing standardized guidelines for its implementation across different healthcare settings. Moreover, efforts should be directed toward refining operator training protocols and quality assurance measures to minimize variability and ensure the reliability of POCUS-based frailty assessments.

As the population of patients undergoing surgery continues to age, the identification of frailty becomes increasingly important to anticipate postoperative needs and guide operative planning. This paper supports further validation of the utility of POCUS to measure quadriceps depth as an alternative to time-consuming or costly evaluations for frailty. Ultimately, while there are no drug treatments for frailty, non-pharmacological interventions, such as addressing poor nutrition and cognitive disorders, may be able to improve future surgical outcomes in affected patients34,35.

Disclosures

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None of the authors have any conflicts of interest to disclose.

Acknowledgements

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None. No funding was received for this project.

Materials

List of materials used in this article
NameCompanyCatalog NumberComments
High Frequency Ultrasound Probe (HFL38xp)SonoSite (FujiFilm)P16038
Low Frequency Ultrasound Probe (C35xp)SonoSite (FujiFilm)P19617
SonoSite X-porte UltrasoundSonoSite (FujiFilm)P19220
Ultrasound GelAquaSonicPLI 01-08

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Frailty AssessmentPoint Of Care UltrasoundQuadriceps MuscleMuscle ThicknessSurgical RiskUltrasound MeasurementPreoperative EvaluationRectus FemorisBedside Ultrasound

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