Analysis of achilles tendon vascularity with second-generation contrast-enhanced ultrasound

Update of Contrast-enhanced Ultrasound in Musculoskeletal Medicine: Clinical Perspectives - A Review

Contrast-enhanced ultrasound (CEUS) uses an intravascular contrast agent to enhance blood flow signals and assess microcirculation in different parts of the human body. Over the past decade, CEUS has become more widely applied in musculoskeletal (MSK) medicine, and the current review aims to systematically summarize current research on the application of CEUS in the MSK field, focusing on 67 articles published between January 2001 and June 2021 in online databases including PubMed, Scopus, and Embase. CEUS has been widely used for the clinical assessment of muscle microcirculation, tendinopathy, fracture nonunions, sports-related injuries, arthritis, peripheral nerves, and tumors, and can serve as an objective and quantitative evaluation tool for prognosis and outcome prediction. Optimal CEUS parameters and diagnostic cut off values for each disease category remain to be confirmed.

Operative versus conservative treatment of acute Achilles tendon ruptures: preliminary results of clinical outcome, kinematic MRI and contrast-enhanced ultrasound

INTRODUCTION

There is no uniform consensus on the gold standard therapy for acute Achilles tendon rupture. The aim of this pilot study was to compare operative and conservative treatment regarding imaging findings and clinical outcome.

MATERIALS AND METHODS

Surgically or conservatively treated patients with acute Achilles tendon rupture were retrospectively evaluated. Differences in tendon length and diameter with and without load were analysed using kinematic MRI, tendon perfusion, structural alterations, movement and scar tissue by means of grey-scale and contrast-enhanced ultrasound (CEUS). Intra- and interobserver agreement were recorded.

RESULTS

No significant difference was detected regarding clinical outcome, B mode ultrasonography, contrast-enhanced sonography or MRI findings, although alterations in MRI-based measurements of tendon elasticity were found for both groups. Considerable elongation and thickening of the injured tendon were detected in both groups.

CONCLUSION

Both, conservative and surgical treatment showed comparable outcomes in our preliminary results and may suggest non-inferiority of a conservative approach.

Contrast-enhanced ultrasound for musculoskeletal indications in children

The increasing use of contrast-enhanced ultrasound (CEUS) has opened exciting new frontiers for musculoskeletal applications in adults and children. The most common musculoskeletal-related CEUS applications in adults are for detecting inflammatory joint diseases, imaging skeletal muscles and tendon perfusion, imaging postoperative viability of osseous and osseocutaneous tissue flaps, and evaluating the malignant potential of soft-tissue masses. Pediatric musculoskeletal-related CEUS has been applied for imaging juvenile idiopathic arthritis and Legg-Calvé-Perthes disease and for evaluating femoral head perfusion following surgical hip reduction in children with developmental hip dysplasia. CEUS can improve visualization of the capillary network in superficial and deep tissues and also in states of slow- or low-volume blood flow. In addition, measurements of blood flow imaging parameters performed by quantitative CEUS are valuable when monitoring the outcome of treatment interventions. In this review article we present current experience regarding a wide range of CEUS applications in musculoskeletal conditions in adults and children, with emphasis on the latter, and discuss imaging techniques and CEUS findings in musculoskeletal applications.

Evaluation of Tendon Disorders With Ultrasonography and Elastography

The frequency of musculoskeletal system ultrasonography (US) has increased over time. The most common reason for musculoskeletal US is the evaluation of tendons. The superficial location of tendons makes US the most suitable diagnostic tool, and US is generally the initial imaging modality for tendon disorders. The primary advantages of US are its low cost, easy accessibility, rapidity, repeatability, freedom from x-rays, and enabling of a dynamic inspection. In addition, Doppler US and elastography can be performed simultaneously with US. We aimed to demonstrate the US and elastographic findings of tendon disorders that we frequently encounter in different regions.

Doppler Flow Response Following Running Exercise Differs Between Healthy and Tendinopathic Achilles Tendons

Background

The relationship between exercise-induced intratendinous blood flow (IBF) and tendon pathology or training exposure is unclear.

Objective

This study investigates the acute effect of running exercise on sonographic detectable IBF in healthy and tendinopathic Achilles tendons (ATs) of runners and recreational participants.

Methods

48 participants (43 ± 13 years, 176 ± 9 cm, 75 ± 11 kg) performed a standardized submaximal 30-min constant load treadmill run with Doppler ultrasound “Advanced dynamic flow” examinations before (U_pre) and 5, 30, 60, and 120 min (U₅-U₁₂₀) afterward. Included were runners (>30 km/week) and recreational participants (<10 km/week) with healthy (H_run, n = 10; H_rec, n = 15) or tendinopathic (T_run, n = 13; T_rec, n = 10) ATs. IBF was assessed by counting number [n] of intratendinous vessels. IBF data are presented descriptively (%, median [minimum to maximum range] for baseline-IBF and IBF-difference post-exercise). Statistical differences for group and time point IBF and IBF changes were analyzed with Friedman and Kruskal-Wallis ANOVA (α = 0.05).

Results

At baseline, IBF was detected in 40% (3 [1–6]) of H_run, in 53% (4 [1–5]) of H_rec, in 85% (3 [1–25]) of T_run, and 70% (10 [2–30]) of T_rec. At U₅ IBF responded to exercise in 30% (3 [−1–9]) of H_run, in 53% (4 [−2–6]) of H_rec, in 70% (4 [−10–10]) of T_run, and in 80% (5 [1–10]) of T_rec. While IBF in 80% of healthy responding ATs returned to baseline at U₃₀, IBF remained elevated until U₁₂₀ in 60% of tendinopathic ATs. Within groups, IBF changes from U_pre-U₁₂₀ were significant for H_rec (p < 0.01), T_run (p = 0.05), and T_rec (p < 0.01). Between groups, IBF changes in consecutive examinations were not significantly different (p > 0.05) but IBF-level was significantly higher at all measurement time points in tendinopathic versus healthy ATs (p < 0.05).

Conclusion

Irrespective of training status and tendon pathology, running leads to an immediate increase of IBF in responding tendons. This increase occurs shortly in healthy and prolonged in tendinopathic ATs. Training exposure does not alter IBF occurrence, but IBF level is elevated in tendon pathology. While an immediate exercise-induced IBF increase is a physiological response, prolonged IBF is considered a pathological finding associated with Achilles tendinopathy.

Posttraumatic Perfusion Analysis of Quadriceps, Patellar, and Achilles Tendon Regeneration With Dynamic Contrast-Enhanced Ultrasound and Dynamic Contrast-Enhanced Magnetic Resonance Imaging: Preliminary Results

OBJECTIVES

The healing process of tendons after surgical treatment of tendon ruptures mainly depends on the perfusion of the tendon and its surrounding tissue. Dynamic contrast-enhanced ultrasound (DCE-US) and dynamic contrast-enhanced MRI (DCE-MRI) can provide additional information about the local microperfusion. In this pilot study, the feasibility of these techniques to assess the vascularization during tendon regeneration was evaluated.

METHODS

Between 2013 and 2015, 23 patients with surgical treatment of traumatic rupture of quadriceps, patellar, and Achilles tendons were involved. All patients received clinical follow-up examinations at 6, 12, and at least 52 weeks postoperatively. Dynamic contrast-enhanced US and DCE-MRI examinations were performed 6 and 12 weeks postoperatively. Dynamic contrast-enhanced US perfusion was quantified by the parameters peak enhancement, wash-in area under the curve, rise time, and initial area under the curve. Correlations between these parameters were examined via the Spearman rank correlation. The clinical and functional outcomes were assessed via the Lysholm Knee Score and Knee and Osteoarthritis Outcome Score at 12 and 52 weeks postoperatively.

RESULTS

Fourteen patients with quadriceps (n = 8), patellar (n = 4) and Achilles (n = 2) tendon ruptures with complete follow-up were available. The microperfusion could be successful assessed. We could detect a strong correlation of DCE-US (peak enhancement) parameters with DCE-MRI (initial area under the curve) parameters after 6 and 12 weeks.

CONCLUSIONS

In this pilot study, DCE-US was able to visualize the microperfusion of healing tendons with a strong correlation with DCE-MRI. Our initial results are in favor of DCE-US as a potential quantitative imaging tool for evaluating the vascularization in tendon regeneration as a complementary method.

Contrast-Enhanced Ultrasound for Musculoskeletal Applications: A World Federation for Ultrasound in Medicine and Biology Position Paper

This World Federation for Ultrasound in Medicine and Biology position paper reviews the diagnostic potential of ultrasound contrast agents for clinical decision-making and provides general advice for optimal contrast-enhanced ultrasound performance in musculoskeletal issues. In this domain, contrast-enhanced ultrasound performance has increasingly been investigated with promising results, but still lacks everyday clinical application and standardized techniques; therefore, experts summarized current knowledge according to published evidence and best personal experience. The goal was to intensify and standardize the use and administration of ultrasound contrast agents to facilitate correct diagnoses and ultimately to improve the management and outcomes of patients.

In Achilles tendinopathy, the neovascularization, detected by contrast-enhanced ultrasound (CEUS), is abundant but not related to symptoms

PURPOSE AND HYPOTHESIS

Mid-portion Achilles tendinopathy is characterized by a proliferation of small vessels, called neovascularization, which can be demonstrated by power Doppler sonography (PD). Neovascularization can be correlated with diagnosis and consequent therapies focused on vascular supply. Published data regarding the relationship between neovascularisation and symptoms, such as pain and disability, are contradictory. The hypothesis that contrast-enhanced ultrasound (CEUS) could detect with more sensibility than PD the new vessel ingrowth in human degenerated Achilles tendons and therefore the correlation of neovascularization with pain and disability, was evaluated.

METHODS

Thirty consecutive patients of recalcitrant Achilles tendinopathy were studied with ultrasound greyscale (US), PD, CEUS and magnetic resonance imaging. Neovascularization was recorded as percentage on the whole extension of examined area. The vascularization time was recorded as venous and arterial type. Imaging data were classified both concurrently with the examination and in a secondary blinded assessment; any difference in the subjective assessment was discussed and a consensus view formed. Pain and disability were assessed by Western Ontario McMaster Universities Arthritis Index (WOMAC) and EuroQuality of life 5-dimension-5-level questionnaire and visual analogue scale (EQ-VAS). All results were analysed with suitable statistical methods.

RESULTS

76.7% of cases were degenerated; 23.3% had also partial discontinuity of the fibres. PD detected vascularization in 54% of cases, whereas CEUS in 83% of cases: in 13 cases, PD did not detect vascularization. The vascularization time was rapid (< 20 s, arterial type) in 60% of cases. WOMAC pain mean value is 6.4 and SD 3.4; WOMAC total score mean value is 21.6 and SD 12.8. EQ-VAS mean value is 56 and SD 18.3. No statistically significant correlation emerged between vascularization and pain/disability.

CONCLUSIONS

CEUS showed a greater ability to detect neovessels than PD in chronic Achilles tendinopathies. Nevertheless in 30 consecutive tendinopathies, no correlation between pain/disability and neovascularization was found: the role of multiple neovessels continue to be unclear. The possibility to discriminate arterial from venous vessels ('vascularization time') could be useful to understand the pathophysiology of tendinopathies and its healing process.

STUDY TYPE

Diagnostic study.

LEVEL OF EVIDENCE

II.

Imaging modalities in the diagnosis and monitoring of Achilles tendon ruptures: A systematic review

OBJECTIVE

To determine the role of imaging in the diagnosis and monitoring of the Achilles tendon rupture (ATR).

STUDY DESIGN

Systematic review.

DATA SOURCES

PubMed and EMBASE in November 2016.

ELIGIBILITY CRITERIA

Clinical studies providing information on the methods and role of imaging in the diagnosis and monitoring of the ATR were included.

RESULTS

Fifty-six studies were included, most concerning the use of ultrasound (n=37) or MRI (n=18). Seven studies provided data on the diagnostic accuracy of imaging. Most ultrasound studies used a 7.5MHz probe (19/32 studies) and scanned the patient bilaterally in prone position, with recent studies tending to use higher frequency probes (r=0.42). Sensitivity [for detecting a rupture] ranged from 79.6 to 100%; the spread in specificity was large but two studies showed perfect (100%) data. Negative and positive likelihood ratios ranged from 0 to 0.23 and 1.0 to 10 respectively. MRI examination was generally performed with 1.5Tesla (T) MRI (6/12 studies) with a strong trend for higher T strength in more recent studies (r=0.71). One study reported a sensitivity of 90.9% and one a specificity of 100%. Although imaging can visualize structure and healing, these results were generally not related to the clinical picture. Overall, ultrasound was recommended over MRI for diagnosis and monitoring. Results of other imaging modalities remain inconclusive.

CONCLUSION

The adjunct role of imaging, especially of ultrasound and MRI, in the diagnosis and monitoring of ATRs was established. It is therefore recommended to rely primarily on the clinical examination and evaluation and to use imaging for ruling out other injuries and providing additional clinical information. More high-quality research is warranted into the diagnostic accuracy of imaging as well as less conventional imaging modalities' diagnostic and monitoring capabilities.

Sonography of the Achilles Tendon After Complete Rupture Repair: What the Radiologist Should Know

This review aims to provide the radiologist with simple and systematic guidelines for evaluation of the Achilles tendon after complete rupture repair. Currently, there is a plethora of nonsurgical and surgical treatments, but sonographic examination has shown no significant differences between them. A systematic analysis of several parameters (morphologic characteristics, structure, color Doppler vascularization, and mobility) should be undertaken. Morphologically, the repaired tendon is larger, wider, or both. The loss of the fibrillary structure, inhomogeneity, and the surgical material in the context of the tendon are "normal" aspects after a repaired rupture. The presence of fluid collections when affecting greater than 50% of the surface of the tendon and extensive calcifications should be considered pathologic aspects. In the immediate postoperative period, there is the absence of vascularization detectable by color Doppler imaging. During the first 3 months, there is an increase in intratendinous vascularization with hypervascularization. From 3 to 6 months, stabilization and regression of the vascularization occur. Beyond the first 6 months, the hypervascularization is pathologic. The pattern of motion is, generally, reduced considerably more often in surgically treated tendons than in non-surgically treated ones. Elastography generally shows a hard appearance, with only a relatively heterogeneous pattern. In conclusion, a treated tendon will never regain a normal sonographic appearance, and the operator must distinguish between normal posttreatment changes and real pathologic characteristics.

The regional microvascular density of the gluteus medius tendon determined by immunohistochemistry with CD31 staining: a cadaveric study

BACKGROUND AND PURPOSE

There are no studies to date about the vascularisation into the gluteus medius tendon. The purpose of this study was to define the microvessel density of the gluteus medius in 3 zones through a special staining with CD31 and to identify regional differences in microvascular density that may have implications for the healing.

METHODS

We obtained 12 complete gluteus medius tendons from cadavers who had been an average age of 30.3 years old (range 18 to 55). All the donors were males with no known history of hip abnormalities.Following a rigorous protocol, each gluteus medius tendon was divided in 3 portions. Each gluteus medius tendon was divided in 3 portions (I: musculotendinous, II: Tendon, III: Tendon-Bone junction).

RESULTS

There were regional differences between all anatomic zones in both the transverse section (p<0.001) and the longitudinal section (p = 0.007). Furthermore, a significant difference was found between zones II and I (mean difference -23.45 IC95% -38.77 to -8.13, p<0.001) and between zones II and III (mean difference -26.08 IC95% -41.39 to -10.76, p<0.001) in transverse section. In longitudinal sections, this difference was found as well between zones II and I (mean difference -29.48 IC95% -51.54 to -7.43, p = 0.01), but not between zones II and III (mean difference -10.87 IC95% -32.93 to 11.18, p = 0.67).

CONCLUSIONS

The microvessel density was significantly lower in the length of the tendon (central portion) compared to the other 2 regions.

The acute effects of exercise on the microvascular volume of Achilles tendons in healthy young subjects

BACKGROUND

Real-time harmonic contrast-enhanced ultrasound (CEU) is used in several diseases to visualize the microvascularization in various tissues, due to its high sensitivity.

AIM

The aim of the present study was to investigate whether CEU could be used to detect an increase in the microvascular volume (MV) in healthy tendon tissue in response to exercise comprising a 1-h run.

METHODS

After a bolus injection of the ultrasound contrast SonoVue(®), CEU measurements of (MV) in the Achilles tendon were taken prior to exercise, immediately after a 1-h run, and 24 h after exercise in nine healthy young subjects (seven men and two women) mean age 31 ± 4 years. In addition, the effect of 15 min of arm cycling exercise on the flow within the Achilles tendon was tested in four athletes (mean age 33 ± 6 years) using the CEU method before and after exercise.

RESULTS

The present data show a significant increase in the (MV) of the Achilles tendon for all subjects following the run compared with before exercise. No significant change in (MV) was seen in the Achilles tendon after 15-min arm cycling exercise (P = 0·96). This indicates that the increase in microvascular blood volume within the Achilles tendon in response to running is a local response.

CONCLUSION

The present data reveal that real-time harmonic CEU can be used to determine the MV of healthy Achilles tendons both at rest and after 1 h of running exercise.

Ultrasound in sports medicine: relevance of emerging techniques to clinical care of athletes

The applications of ultrasound in managing the clinical care of athletes have been expanding over the past decade. This review provides an analysis of the research that has been published regarding the use of ultrasound in athletes and focuses on how these emerging techniques can impact the clinical management of athletes by sports medicine physicians. Electronic database literature searches were performed using the subject terms 'ultrasound' and 'athletes' from the years 2003 to 2012. The following databases were searched: PubMed, Web of Science, Cochrane Library, CINAHL, and SPORTDiscus™. The search produced 617 articles in total, with a predominance of articles focused on cardiac and musculoskeletal ultrasound. 266 of the studies involved application of ultrasound in evaluating the cardiovascular properties of athletes, and 151 studies involved musculoskeletal ultrasound. Other applications of ultrasound included abdominal, vascular, bone density and volume status. New techniques in echocardiography have made significant contributions to the understanding of the physiological changes that occur in the athlete's heart in response to the haemodynamic stress associated with different types of activity. The likely application of these techniques will be in managing athletes with hypertrophic cardiomyopathy, and the techniques are near ready for application into clinical practice. These techniques are highly specialized, however, and will require referral to dedicated laboratories to influence the clinical management of athletes. Investigation of aortic root pathology and pulmonary vascular haemodynamics are also emerging, but will require additional studies with larger numbers and outcomes analysis to validate their clinical utility. Some of these techniques are relatively simple, and thus hold the potential to enter clinical management in a point-of-care fashion. Musculoskeletal ultrasound has demonstrated a number of diagnostic and therapeutic techniques applicable to pathology of the shoulder, elbow, wrist, hand, hip, knee and ankle. These techniques have been applied mainly to the management of impingement syndromes, tendinopathies and arthritis. Many of these techniques have been validated and have entered clinical practice, while more recently developed techniques (such as dynamic ultrasound and platelet-rich plasma injections) will require further research to verify efficacy. Research in musculoskeletal ultrasound has also been helpful in identifying risk factors for injury and, thus, serving as a focus for developing interventions. Research in abdominal ultrasound has investigated the potential role of ultrasound imaging in assessing splenomegaly in athletes with mononucleosis, in an attempt to inform decisions and policies regarding return to play. Future research will have to demonstrate a reduction in adverse events in order to justify the application of such a technique into policy. The role of ultrasound in assessing groin pain and abdominal pain in ultraendurance athletes has also been investigated, providing promising areas of focus for the development of treatment interventions and physical therapy. Finally, preliminary research has also identified the role of ultrasound in addressing vascular disease, bone density and volume status in athletes. The potential applications of ultrasound in athletes are broad, and continuing research, including larger outcome studies, will be required to establish the clinical utility of these techniques in the care of athletes.

Application of contrast-enhanced sonography with time-intensity curve analysis to explore hypervascularity in Achilles tendinopathy by using a rabbit model

OBJECTIVES

The purpose of this study was to investigate the ability of contrast-enhanced sonography in staging and grading hypervascularity in tendinopathic tissues by using a rabbit model.

METHODS

Fourteen rabbits were injected with 100 and 50 μL of collagenase in their left and right Achilles tendons, respectively. The vascularity was assessed by non-contrast-enhanced and contrast-enhanced power Doppler sonography on day 0 (baseline) and days 1, 7, and 14 after collagenase injections. Color pixels within targeted areas were plotted according to time and analyzed by a curve-fitting method.

RESULTS

Non-contrast-enhanced power Doppler sonography failed to differentiate vascularity at various stages or between bilateral tendons, whereas contrast-enhanced sonography showed that the peak color pixel amount reached its maximum on day 1 and declined over time in tendons treated with 100 μL of collagenase. A similar trend was observed in tendons receiving 50 μL of collagenase. For comparisons between bilateral tendons, higher vascularity was detected in those treated with more collagenase on day 1 or 7. Time-intensity curve analysis revealed rapid microbubble replenishment in both tendons during their initial phase after collagenase injections.

CONCLUSIONS

Contrast-enhanced sonography discriminated the vascularity of various injury grades at different time points after collagenase injections. Time-intensity curve analysis detailed the hemodynamics in tendinopathic tissues, which helped differentiate vascularity in acute inflammatory from later degenerative phases.