Ultrasound superiority in detecting micro rib lesions for post-coronavirus disease 2019 chest wall pain: a comparative retrospective study

Introduction

Since December 2022, the incidence rate of confirmed cases of coronavirus disease 2019 (COVID-19) in China has gradually increased. In December, the daily number of new cases ranged from 3,000 to 8,000, eventually reaching its peak. The majority of these cases have been classified as mild (1). A dry cough is recognized as one of the most prevalent initial symptoms of COVID-19, affecting approximately 60–70% of symptomatic patients, alongside fever and the loss of taste and smell (2-5). Following the acute phase of COVID-19, coughing may persist for several weeks or months and is frequently associated with chronic fatigue, cognitive impairment, dyspnea, or pain. These prolonged effects are collectively referred to as post-COVID syndrome or long COVID (6-8). In the later stages of the illness, characterized by three consecutive negative detections of viral RNA on a nasopharyngeal swab, cough symptoms may intensify, often accompanied by chest pain, which can significantly disrupt patients’ work, sleep, and overall quality of life.

Imaging tests are essential for the assessment of patients experiencing localized chest wall pain following COVID-19 infection. Computed tomography (CT) is a widely utilized imaging modality that can reveal lesions in the lungs, pleura, ribs, and other structures. However, it is noteworthy that many patients exhibit no physical or radiological abnormalities aside from tenderness in the affected area of the chest wall, which complicates clinical diagnosis and treatment (9). For individuals presenting with localized chest pain, ultrasound (US) serves as an effective diagnostic tool. US is a portable, rapid, radiation-free, and noninvasive technique that offers a high rate of differentiation and good penetration for evaluating chest wall lesions. It is particularly valuable in the assessment of a variety of pleural and chest wall conditions, as well as in identifying missed rib fractures (10-12). However, US also has certain limitations compared to CT scans. For instance, US has a limited penetration depth, which may make it difficult to visualize deeper structures in patients with obesity or those with large breasts. Additionally, US findings are highly operator-dependent, requiring extensive experience and skill to obtain accurate results. CT scans, on the other hand, provide comprehensive cross-sectional images of the chest, including detailed visualization of bony structures and posterior chest wall areas, which may be challenging to assess with US alone. Numerous US findings have been documented in patients with COVID-19; to our knowledge, there has been no published literature specifically addressing US findings in patients with localized chest pain following COVID-19 infection.

In this study, we retrospectively analyzed the dynamic US or CT findings in 47 patients who experienced chest wall pain following a cough associated with COVID-19 and explored the value of US for detecting and monitoring patients with localized chest wall pain. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-722/rc).

Methods

Patient selection

We conducted a retrospective observational study involving consecutively admitted patients experiencing chest wall pain following COVID-19 at a tertiary hospital in Beijing from December 1, 2022, to December 31, 2022. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Ethics Board of Beijing Tsinghua Changgung Hospital (approval No. 23621-6-01). Informed consent was waived in this retrospective study. The diagnosis of COVID-19 was confirmed by the detection of viral RNA through real-time polymerase chain reaction (PCR) on a nasopharyngeal swab. All patients who presented to the pain department with chest pain symptoms after COVID-19 within 60 days (the typical duration of COVID-19 in China is up to two months) were included in the study. For a more comprehensive assessment and definitive diagnosis, CT and US examinations are routinely performed for most patients with chest pain in our department.

Fifty-one patients participated in the pain department due to localized chest wall pain following COVID-19 between December 1, 2022, and December 31, 2022. Among these patients, four did not undergo US or CT examination, and the remaining 47 patients completed either US or CT examinations. The sample size was determined based on the number of eligible patients during the study period, as this was a retrospective analysis of existing clinical data.

Collection of clinical information

All patients underwent an initial cardiac workup to exclude angina and other cardiac causes of chest pain before proceeding to CT or US examinations. This included electrocardiogram (ECG), troponin level measurements and echocardiography. Inclusion was strictly limited to patients who demonstrated normal ECG findings, normal troponin levels, or normal echocardiographic results, in conjunction with a clinical evaluation indicative of non-cardiac chest pain. All patients were asked about the date of their initial COVID-19 diagnosis, the duration of their illness, whether they experienced a cough, the severity of the cough, and the duration of any chest wall pain. Patients who presented to the pain department were also queried about the characteristics of their chest pain, including its location and severity. We utilized the Visual Analog Scale (VAS) (scale 0–10) to evaluate the intensity of chest pain in patients. Additionally, cough severity was assessed using the cough VAS (scale 0–10).

CT and US examination

All eligible patients underwent either chest CT or US examination to determine the cause of their chest pain. In cases where patients received both US and CT examinations, these were ordered simultaneously, with the US performed either before or after the CT examination, ensuring a time difference of no more than three days.

CT examinations were conducted using 64-section scanners (GE Discovery CT750 HD). Images were reconstructed with a slice thickness of 1.25 mm, employing a high-frequency reconstruction algorithm. Image acquisitions were performed during a deep inspiration breath-hold. All chest CT images were retrospectively reviewed by two radiologists with 10 and 15 years of experience in chest imaging, respectively. They worked independently and reached a consensus on the findings. US examinations were performed using the Aixplorer system (SuperSonic Imagine, Aix-en-Provence, France) with an SL15-4 linear probe and the EPIQ 7C system (Philips, America) with an SL12-5 linear probe. The examination focused on the specific area of patient-reported pain, which was typically localized and fixed. The most painful area, characterized by focal chest tenderness, was examined in detail with the probe positioned transversely, parallel to the rib’s long axis.

This approach generally provided adequate imaging for the anterior chest wall but required additional techniques for the lateral and posterior chest walls. For the lateral chest wall, patients were repositioned to a lateral decubitus position to reduce acoustic shadowing from breast tissue and improve visualization of underlying structures. For the posterior chest wall, patients were positioned prone to enhance contact between the posterior chest wall and the transducer, with the probe carefully angled to optimize image quality. In some cases, a low-frequency convex probe was used initially to roughly locate the area of interest, followed by a high-frequency linear probe for a more detailed examination. An extensive scan of the surrounding tissue was then performed.

Imaging female patients and those with obesity presented additional challenges. For obese patients, the limited penetration depth of the high-frequency linear probe could potentially affect the visualization of deeper anterior chest wall layers. To address this, the sonographer adjusted the probe’s frequency to a lower setting and applied gentle pressure to improve contact and reduce artifacts. For female patients, particularly those with larger breasts, the probe’s position was carefully adjusted to ensure optimal visualization of the chest wall structures beneath the breast tissue. Despite these adjustments, imaging deeper layers in some obese and female patients remained more challenging compared to leaner or male patients.

To minimize variability and enhance feasibility, the chest US examination was carried out by a sonographer with over 20 years of experience in musculoskeletal US. The stored images were subsequently reviewed by a different, blinded sonographer, also with more than 20 years of experience in musculoskeletal US, and a consensus was ultimately reached. The radiologists and sonographers were distinct teams, and they were blinded to each other’s findings to minimize bias. The results were documented immediately following the US examination based on real-time sonographic findings. Patients who underwent US or CT examinations were asked to return for follow-up sonography after 3–4 weeks.

Statistical analysis

The software SPSS version 22.0 (IBM Corp., Armonk, NY, USA) was utilized for statistical analysis. All data were presented as the mean ± standard deviation (M ± SD), and a P value <0.05 was considered statistically significant. The Kolmogorov-Smirnov test was employed to assess the normality of the data distribution. A t-test was conducted to compare the duration of COVID-19 between the two groups, while the Mann-Whitney U test was used to compare the duration of chest wall pain, cough severity, chest pain severity, and the degree of pain relief between the two groups.

Results

Demographic and clinical characteristics

Forty-seven patients were ultimately enrolled in the study (Figure 1). Based on the results of US or CT examination, 47 patients were categorized into a positive group and a negative group.

Figure 1 STARD diagram of the flow of participants in the study. COVID-19, coronavirus disease 2019; CT, computed tomography; STARD, Standards for Reporting of Diagnostic Accuracy; US, ultrasound.

The positive group included patients with identifiable chest wall lesions on imaging, such as rib fractures, periosteal reactions, costochondritis, thickened deep fascia, or fat herniations. The negative group consisted of patients with no detectable chest wall abnormalities on both CT and US. The demographic and clinical characteristics of each group are presented in Table 1. All patients had a history of COVID-19 and experienced persistent cough symptoms. Additionally, all patients reported localized chest wall pain, which was often exacerbated by inspiration, coughing, and localized palpation. The VAS evaluation results regarding the location of chest pain, the duration of COVID-19, the duration of chest pain, cough severity, and chest pain severity are detailed in Table 2 (positive group) and Table 3 (negative group). A total of 25 patients were included in the positive group, while 22 patients were included in the negative group. The comparison results between the positive and negative groups are presented in Table 4. In the positive group, the average VAS score for chest pain was 7.0±1.4, which was significantly higher than the negative group’s score of 4.7±1.4 (P<0.01). Similarly, the average cough severity score for the positive group was 6.6±1.8, compared to 4.3±1.6 for the negative group (P<0.01). The average duration of chest pain in the positive group was 8.1±7.3 days, while in the negative group it was 8.0±8.1 days, showing no statistically significant difference (P=0.71). Additionally, there was no significant difference in the duration of COVID-19 between the two groups (P=0.58). Although the duration of the illness was comparable, these findings underscore significant differences in pain and cough severity between the two groups. At the second visit (3–4 weeks after the first visit), a significant difference in pain relief was observed between the two groups (P<0.01), with the positive group demonstrating greater pain relief than the negative group.

All patients were diagnosed with COVID-19 and had completed acute treatment at least two weeks prior to enrollment in the study. During the acute phase of COVID-19, patients receive various treatments based on their symptoms and the severity of the disease, which may include rest, hydration, and management of fever and pain with acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs). However, hospitalization or intensive care is not required, and all patients receive symptomatic support treatment. At the time of study registration, the patients’ symptoms of COVID-19 were stable. For the management of chest pain, patients with mild chest pain are initially treated with NSAIDs and acetaminophen to alleviate discomfort. In more severe cases, weak opioid medications may be added. Additionally, patients are advised to gently stretch the chest wall, rest, and use protective measures when coughing. The reduction of chest pain in the group of patients who tested positive for COVID-19 is attributed to the improvement of the disease, as confirmed by imaging examinations and effective pain management. US imaging reveals healing of rib lesions, which correlates with subsequent pain relief. For patients experiencing chest pain due to severe coughing associated with COVID-19, cough medications such as codeine or dextromethorphan are administered to decrease the frequency and intensity of coughing. Expectorants are used to thin secretions, thereby reducing the force of coughing, and patients are instructed on proper coughing techniques to minimize pressure on the chest wall. Collectively, these interventions have contributed to a reduction in the pain scores of the patients.

US and CT findings

Ultrasonographic examinations were conducted on a cohort of 35 patients. Among the positive cases, all 25 patients (100%) exhibited positive ultrasonography results. The ultrasonographic assessment identified rib abnormalities in 17 patients. The predominant finding was an undisplaced fracture, observed in 12 patients. These fractures were attributed to the intense coughing episodes, as all patients had a history of severe cough following COVID-19, with no reported history of external chest trauma. All patients with suspected rib fractures on US underwent CT scans to confirm the diagnosis and assess the extent of the lesions. Additional findings included thickening of the deep fascia at the site of pain in 5 patients, periosteal reaction in 2 patients, costal chondritis in 1 patient, deep fascial fat hernia in 1 patient, mild laceration at the junction of the procostal arch and sternum in 1 patient, echo enhancement of local subcutaneous fat in 1 patient, and surface roughness of the ribs accompanied by local soft tissue swelling and injury at the junction of the ribs and rib cartilage in 1 patient (Figures 2-5). Furthermore, chest CT examinations were performed on 46 patients. Within the positive group, only 5 patients (20%) demonstrated positive CT results during the initial visit, all of which were rib lesions. Detailed findings from the ultrasonography and CT examinations for the positive group are presented in Table 5. Notably, the lesion detection rate for ultrasonography was significantly higher than that for CT, with rates of 100% and 20%, respectively.

Figure 2 US image of a deep fascial adipose hernia. This case involves a 30-year-old male with a history of COVID-19 and a severe cough. One week after recovering from COVID-19, the patient began to experience localized chest pain that worsened with movement. High-frequency ultrasonography revealed that the superficial layer of deep fascia at the site of pain was discontinuous, and local adipose tissue was herniated, indicating the formation of a deep fascial adipose hernia. The red arrows highlight the herniated fat within the fascia. COVID-19, coronavirus disease 2019; US, ultrasound.

Figure 3 US and CT images of rib fractures are presented for a 36-year-old male with a one-month history of chest pain. The patient had previously contracted COVID-19 and experienced a severe cough. High-frequency ultrasonography revealed a fracture of the 6th rib without any obvious dislocation, with surrounding callus formation (A,B). Both plain CT scans and 3D reconstructions confirmed the fracture of the 6th rib (D,E). Three weeks later, ultrasonography indicated that the cortex of the 6th rib was intact, and the callus was nearly completely absorbed (C). The red arrows indicate the fracture site. 3D, three-dimensional; COVID-19, coronavirus disease 2019; CT, computed tomography; US, ultrasound.

Figure 4 US and CT images of rib fractures. This is a 28-year-old female who experienced significant tenderness at the left costal margin for five days. The patient had a history of COVID-19 and a severe cough. High-frequency ultrasonography revealed a fracture of the left ninth rib, accompanied by slight dislocation and fresh callus formation (A). Both the plain CT scan and 3D reconstruction clearly demonstrated the fracture of the ninth rib (C,D). One month later, the US examination indicated that callus formation was observed at the original fracture site of the left costal margin, indicating a healing stage (B). The red arrows indicate the fracture site. 3D, three-dimensional; COVID-19, coronavirus disease 2019; CT, computed tomography; US, ultrasound.

Figure 5 US and CT images of rib fractures are presented. This case involves a 29-year-old female who experienced severe chest pain for four days. The patient has a history of COVID-19 and a significant cough. High-frequency ultrasonography revealed a fracture of the right seventh rib, characterized by a slight and sharp dislocation with fresh callus formation (A,B). Both the plain CT scan and 3D reconstruction clearly demonstrated the fracture of the seventh rib (D,E). Three weeks later, the US examination indicated that callus formation was observed at the original fracture site, signifying a healing stage (C). The red arrows (A-E) and the white arrow (B) indicate the fracture site. 3D, three-dimensional; COVID-19, coronavirus disease 2019; CT, computed tomography; US, ultrasound.

The average duration of the US examination was between 5 and 18 minutes, with an average of 10 minutes. Most of the time was spent localizing the lesion site. Follow-up USs were conducted to monitor the repair stages of the fracture, particularly during cartilage callus formation. In the positive group, of the 25 patients who underwent US review one month later, most presented with signs of fracture healing. However, 7 patients exhibited no positive ultrasonography findings, indicating complete healing of the rib lesions. Only 4 patients underwent chest CT scans a month later, and 2 of these patients showed new findings related to rib changes.

Discussion

In this single-center, objective study, we aim to explore the causes of localized chest wall pain in patients following COVID-19 infection and to investigate the utility of US for detecting and monitoring these patients. Many individuals who experienced cough symptoms after COVID-19 also reported localized chest wall pain. There are various potential causes of chest wall pain, and imaging examinations are the preferred method for identifying lesions. Through US/CT examination, the present study found that rib lesions were the most common cause of localized chest wall pain. Compared to the negative group, the positive group exhibited higher VAS scores for cough VAS score, pain VAS score, as well as a greater degree of lesion relief. High-frequency US can effectively detect rib and chest wall lesions, allowing for dynamic and continuous observation of the extent and severity of these lesions. Our findings confirm the unique value and advantages of US in detecting chest wall diseases.

In this study, a greater proportion of women were affected compared to men, with 76% of the positive group being female and 24% male. The majority of the participants were young, with a median age of 33.8±12.8 years. All individuals had a documented history of COVID-19, which was followed by severe coughing episodes. US examinations consistently yielded positive results, with the predominant manifestations being bone lesions. Previous research has suggested a potential mechanism by which severe coughing can lead to rib fractures. Specifically, when the force exerted by a cough surpasses the elastic limit of the ribs, small fissures may develop. With repeated force, fractures can occur at the most susceptible point, typically at the costophrenic junction. An additional proposed mechanism involves the opposing forces generated by the anterior serratus and external oblique muscles, which intersect in the middle third of the ribs (13-16). The ribs most commonly fractured are the fifth through ninth, as observed in our cases. Notably, a significant number of patients who experienced rib lesions as a result of coughing were young. A retrospective study conducted at the Mayo Clinic in Rochester, Minnesota, aimed to elucidate the demographic, clinical, and radiological characteristics of 54 patients who sustained cough-induced rib fractures over a 9-year period. The authors concluded that while decreased bone density is a recognized risk factor for cough-induced rib fractures, such fractures may also occur in individuals with normal bone density (17).

In our study, we observed a higher proportion of female patients (76%) in the positive group. This demographic distribution may be attributable to several factors. First, physiological differences suggest that the thoracic structures of females might be more susceptible to injury from repetitive forceful coughing, potentially due to differences in tissue composition and rib structure. Second, hormonal factors could influence the integrity of bones and soft tissues, making females more prone to microfractures and soft tissue injuries. Additionally, emerging evidence indicates that COVID-19 may disproportionately affect females in terms of certain post-acute complications. However, these hypotheses warrant further investigation to establish a definitive relationship (18).

While it is true that rib fractures are more commonly associated with older individuals or those with reduced bone density, the rib fractures observed in younger patients in our study may be attributed to several factors. First, the intense coughing associated with COVID-19 can generate significant intrathoracic pressure changes, placing substantial stress on the ribs. Younger patients, with their stronger respiratory muscles and more forceful cough, may be particularly susceptible to such stress, leading to rib fractures even in the absence of pre-existing bone weakening (19). Second, the anatomical characteristics of younger ribs—being relatively more elastic and flexible—may paradoxically predispose them to microfractures when subjected to repetitive or forceful coughing. Third, the interplay of strong intercostal muscle contractions during vigorous coughing episodes might create additional forces on the ribs. It is also important to note that our study cohort may represent a specific subset of COVID-19 patients and may not be fully generalizable to the broader population. Further research with larger and more diverse samples is needed to better understand the mechanisms and prevalence of rib fractures in younger patients following intense coughing episodes.

In the present study, the findings indicated that among patients with chest pain following COVID-19, the ultrasonic detection rate of chest wall lesions was higher than that of CT, particularly in the case of micro rib fractures. Clinically, rib fractures are typically suspected based on the patient’s medical history and reported pain, with symptoms becoming more pronounced during inspiration, coughing, and localized palpation (20,21). However, fractures are identified in only 32–42% of symptomatic patients (22). While CT is often regarded as the gold standard for diagnosing rib fractures, it subjects patients to significant radiation exposure. Furthermore, CT is not an infallible imaging modality, as the orientation of the tomographic images may overlook fractures due to the unique anatomical features of the thorax (23,24). Various factors, including the location of the fracture, the imaging equipment used, artifacts, concealed fractures, and inadequate soft tissue resolution, can result in many minor fractures and soft tissue injuries appearing as negative on CT imaging. Recently, several researchers have explored the efficacy of US in detecting rib fractures (9,10,25). In comparison to conventional radiography, US demonstrated greater sensitivity in identifying rib fractures, including cartilaginous rib fractures (78% vs. 12%, respectively) (9,11,25,26). Notably, radiographic evaluations did not reveal a fractured rib in 6 out of 18 patients (37.5%), with chest CT examinations conducted in 16 of these patients.

When a fracture occurs, it manifests as a space, step, or displacement within the rib cortex. Fractures may be associated with local hematoma, fluid accumulation, or soft tissue swelling. During the acute healing phase, enhanced echogenicity indicative of callus formation is observed, filling the rib fracture space. Over time, the calcification of the callus may result in the development of a small acoustic shadow. Upon the completion of healing and remodeling, only slight contour abnormalities in the cortex may remain discernible (9,27). This study aimed to investigate the feasibility of using US as a routine and primary diagnostic tool for patients presenting with localized chest pain. Furthermore, US is a valuable and promising modality for patient follow-up, as it not only provides a clear visualization of the dynamic healing process of small lesions but also facilitates repeated, multiple, and long-term follow-up without the associated risks of radiation exposure.

There are certain limitations in this study. The sample size was small due to the initiation of the protocol after the onset of post-COVID-19 chest pain, which occurred following the outbreak of local transmission. In addition, the single-center design, non-randomized grouping, and lack of blinding in this study may introduce selection bias and detection bias. The dependence of US results on operator experience may also affect the reproducibility of the results. We also recognize that the positive and negative groups were unevenly distributed in terms of sex, age, and BMI, which could influence the generalizability of our findings.

Conclusions

Chest wall pain in patients experiencing cough following COVID-19 infection can be attributed to various factors, with rib lesions being the most prevalent. US examination demonstrated a higher detection rate of chest wall lesions in comparison to CT. Consequently, we propose that the US, given its advantages of safety, portability, and high resolution, represents an ideal alternative for the detection and monitoring of patients presenting with localized chest pain.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-722/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-722/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-722/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-722/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Ethics Board of Beijing Tsinghua Changgung Hospital (approval No. 23621-6-01). Informed consent was waived in this retrospective study.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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