Outcomes of ultrasound-guided injections of Bennett lesions of the shoulder.

PURPOSE: To describe our technique and short term follow up of ultrasound-guided injections of symptomatic Bennett lesions. METHODS: We performed 13 ultrasound-guided injections in 10 baseball players from August 2014 to August 2021. The cohort was comprised of 10 males, with a mean age of 25 years and 1 month (age range: 17 years, 10 months-33 years, 1 month). Of the 10 patients, 6 were major league baseball players (including 5 pitchers and a second baseman), 3 were minor league baseball pitchers; and 1 pitched in high school. Symptoms in our patients included posterior shoulder pain at rest, pain with pitching (including in the acceleration phase and with follow-through), glenoid internal reduction deficit, and decreased pitching velocity. The procedure was performed in a similar fashion as a standard posterior approach glenohumeral injection, though with the linear transducer positioned slightly more medially. The needle was inserted from a lateral to medial approach, in plane with the transducer and aimed to the superficial surface of the Bennett lesion, onto which anesthetic and steroid was injected, avoiding injection into the glenohumeral joint. RESULTS: All patients had MRIs that showed Bennett lesions and all but one of the sonograms demonstrated the Bennett lesion. In 8/12 (67%) injections, the patient reported varying degrees of immediate symptom relief. In 4/12 injections, patients were unable to assess for immediate postprocedural change in symptomatology and for one patient post-procedural symptomatology was not documented. No complications occurred. Analytics of the average 4-seam fastball velocity was available for 2 of the major league players who had in-season injections, with minimal change in postprocedural velocity in the year after their ultrasound procedure; for one of the pitchers, his fastball velocity slightly increased in the month after the procedure while the other pitcher had his injection towards the end of the season and he threw no fastballs in his final games of the season. Two of the other professional pitchers went on to surgical intervention and neither returned to pitch professionally. CONCLUSION: Injection of symptomatic Bennett lesions is a safe procedure and can provide symptomatic relief that may be temporary, though equivocally useful clinically.

When to lavage in the absence of a sonographically visible joint effusion in painful total knee arthroplasty: a retrospective longitudinal study.

OBJECTIVE: To determine if knee arthroplasty without sonographically visible effusion needs to undergo lavage to rule out infection. METHODS: Patients were accrued by a retrospective search of a longitudinally maintained radiology database looking for patients referred for ultrasound guided aspiration of suspected TKA infection. Clinical presentations, laboratory tests, intraoperative findings, and follow-up were reviewed. RESULTS: Four hundred sixty-nine patients were included (mean age of 67 years (range, 36-91)) including 251 females. Four hundred three patients had effusions, of which 57 were infected based on ultrasound-guided and surgical aspirates. Sixty-four patients lacked effusions, of which 47 underwent lavage at the clinicians' request, with 6/47 infected. Nineteen patients without effusion were not lavaged at the clinicians' request due to low suspicion, and none were infected. Patients with positive lavage cultures all had clinical risk factors. Infection rates were significantly higher in patients with joint effusion and clinical suspicion for infection compared to absent joint effusion and absent clinical suspicion. A significantly higher proportion of patients with hyperemia or moderate-severe synovial thickening on ultrasound were symptomatic and had joint effusion and positive joint cultures. Aspiration of native fluid had 85% sensitivity and 100% specificity while lavage had a sensitivity of 57% and specificity of 100%. Negative predictive value for native aspirates was 94% compared to 86% for lavage. CONCLUSION: A TKA with low clinical suspicion of infection does not need to undergo lavage in the absence of a sonographically visible effusion.

Serial Ultrasonography for the Assessment of Healing of Lower Extremity Bone Stress Injury and Correlation With Return to Sport/Exercise.

BACKGROUND: Lower extremity bone stress injuries (BSIs) are common among athletes who participate in high-impact activities. Conventional imaging is limited in assessing healing of BSIs. HYPOTHESIS: Serial ultrasonography (US) can identify changes in appearance of lower extremity BSIs over time that can be correlated with symptoms and return to exercise/sport. STUDY DESIGN: Cohort observational study. LEVEL OF EVIDENCE: Level 3. METHODS: Adults 18 to 50 years old with a recent exercise-associated BSI of distal tibia/fibula or metatarsals diagnosed by magnetic resonance imaging (MRI) were enrolled. US was performed every 2 weeks for 12 weeks. The sonographic appearance (soft tissue edema, periosteal reaction, hyperemia on power Doppler, callus) was correlated with the numerical rating scale (NRS) for pain and ability to return to sport/exercise. RESULTS: A total of 30 patients were enrolled (mean age, 35.3 ± 7.7 years; 21 [70.0%] female). The tibia was most frequently affected (n = 15, 50.0%), followed by metatarsals (n = 14, 46.7%) and fibula (n = 1, 3.3%). At week 4, 25 of 30 (83.3%) had at least 1 US finding associated with the BSI. The degree of hyperemia was correlated with NRS at weeks 4 and 6 (Spearman correlations [ρ] 0.45 [0.09, 0.69] and 0.42 [0.07, 0.67], respectively), as well as return to sport/exercise at week 6 (ρ -0.45 [-0.68, -0.09]). US soft tissue edema was also correlated with NRS at week 6 (ρ 0.38 [0.02, 0.65]). CONCLUSION: Serial US of lower extremity BSIs can provide objective measures of healing. US findings were correlated with clinical outcomes at multiple timepoints. CLINICAL RELEVANCE: US may have advantages over conventional imaging for monitoring healing of lower extremity BSIs. Further research is needed to better understand the prognostic value of these sonographic indicators of BSI healing and role in assessing readiness for return to sport/exercise.

Ultrasound assessment of synovitis in total knee replacements: concordance with MR imaging and joint aspiration.

OBJECTIVE: To determine if diagnostic ultrasound can reliably distinguish between synovial patterns of prosthetic joint infection and polymeric wear in total knee replacements. METHODS AND METHODS: This retrospective study was approved by our hospital IRB. Using the radiology report database, MR examinations performed within a week of diagnostic ultrasound and/or ultrasound-guided aspiration were identified. This yielded (1) 24 cases with MR and ultrasound comparisons; (2) 44 cases with MR, ultrasound, and aspiration comparisons; and (3) 92 cases with ultrasound and aspiration comparisons. The MR studies were reviewed by a musculoskeletal radiologist. The ultrasound studies were each reviewed by 2 other musculoskeletal radiologists. Each study was graded for synovial pattern indicating infection, polymeric wear, or normal/nonspecific. Agreement between the MR grader and the ultrasound graders as well as ultrasound inter-rater agreement were assessed using k statistics. Sensitivity, specificity, positive predictive value, and negative predictive value of ultrasound were calculated. RESULTS: Agreement between ultrasound and MR imaging was fair to moderate: k of 0.27 (95% CI: 0.04, 0.50) and 0.44 (95% CI: 0.23, 0.65) for ultrasound raters 1 and 2, respectively. Inter-rater agreement between ultrasound graders 1 and 2 was moderate, with k of 0.56 (95% CI: 0.42, 0.70). Ultrasound sensitivities for infection were 0.13 and 0.09, while specificities were 0.94 and 0.98. Ultrasound sensitivities for polymeric wear were 0.38 and 0.62 with specificities of 0.90 and 0.76. CONCLUSION: Ultrasound does not perform well in distinguishing patterns of synovitis either compared to MRI or a reference standard of aspiration/clinical follow-up.

No Difference in Reintervention at 1-Year Between Ultrasound-Guided versus Blind Dorsal Carpal Ganglion Aspiration.

Purpose: The purpose of this retrospective comparative study was to compare the efficacy of dorsal carpal ganglion aspiration in patients who underwent either "blind" (using surface anatomy alone) or ultrasound-guided (US-guided) aspiration. Methods: Outcome measures were conducted during the coronavirus disease 2019 pandemic via telephone for a minimum of 12 months after aspiration, with efficacy defined by reintervention with either repeat aspiration or surgical excision. Results: Data are reported for 141 patients (46 blind; 95 US-guided) at an average of 28 months (range, 12-55 months) from aspiration. Reintervention was not significantly different based on the mode of aspiration-26% and 24% for blind aspiration and US-guided, respectively. Patient-perceived recurrence was higher at 65% for the entire cohort. Patients who received steroid injection at the time of aspiration perceived lower rates of recurrence-44% versus 77% for patients who received a steroid injection and patients who did not, respectively. Conclusions: This study found no significant difference between blind or US-guided aspiration in reintervention at a minimum of 1-year follow-up. Patients who received steroids at the time of aspiration perceived lower rates of recurrence. Type of study/level of evidence: Therapeutic III.

Imaging of the Hip Prior to Replacement: What the Surgeon Wants to Know.

Total hip arthroplasty is an effective treatment for severe degenerative arthritis and is increasingly being used. Radiography is the primary modality for the initial diagnosis of osteoarthritis and preoperative planning. Additional radiographic views may include the spine and lower extremities in order to optimize implant positioning for the individual patient. Computed tomography is sometimes used for preoperative planning and intraoperative robotic assistance. Magnetic resonance imaging and diagnostic ultrasound is generally reserved for patients without obvious arthritis. Ultrasound-guided injections may provide diagnostic and/or therapeutic benefits.

Pain After Hip Arthroplasty: MR Imaging/Ultrasound Correlation.

MR imaging and ultrasound (US) have complementary roles for the comprehensive assessment of painful hip arthroplasty. Both modalities demonstrate synovitis, periarticular fluid collections, tendon tears and impingement, and neurovascular impingement, often with features indicating the causative etiology. MR imaging assessment requires technical modifications to reduce metal artifact, such as multispectral imaging, and optimization of image quality, and a high-performance 1.5-T system. US images periarticular structures at high-spatial resolution without interference of metal artifact, permitting real-time dynamic evaluation, and is useful for procedure guidance. Bone complications (periprosthetic fracture, stress reaction, osteolysis, and component loosening) are well depicted on MR imaging.

Imaging of the Peripheral Nerves of the Lower Extremity.

Continued advancements in magnetic resonance (MR) neurography and ultrasound have made both indispensable tools for the workup of peripheral neuropathy. Ultrasound provides high spatial resolution of superficial nerves, and techniques such as "sonopalpation" and dynamic maneuvers can improve accuracy. Superior soft tissue contrast, ability to evaluate both superficial and deep nerves with similar high resolution, and reliable characterization of denervation are strengths of MR neurography. Nevertheless, familiarity with normal anatomy, anatomic variants, and common sites of nerve entrapment is essential for radiologists to use both MR neurography and ultrasound effectively.

Dynamic ultrasound assessment of hip instability and anterior and posterior hip impingement.

OBJECTIVE: In this technical report, we describe our protocol for the dynamic sonographic evaluation of the hip and assess reliability of the ultrasound assessment of hip microinstability. MATERIALS AND METHODS: Our clinical experience with a standardized dynamic ultrasound of the hip performed in a series of 27 patients with imaging performed by an experienced musculoskeletal radiologist during physical examination by an orthopedic surgeon specializing in hip preservation is illustrated with clinical photographs and ultrasound images from volunteers and selected patients. Interrater reliability for the diagnosis of microinstability was calculated. RESULTS: Dynamic ultrasound technique and findings of hip instability, femoroacetabular impingement, and ischiofemoral impingement with corresponding clinical photos showing the necessary physical examination maneuvers are described. Interrater agreement for the diagnosis of microinstability was substantial (κ 0.606 [0.221-0.991]). CONCLUSION: At our institution, dynamic ultrasound of the hip during physical examination complements information gathered from static imaging by providing real-time correlation of symptoms with what is occurring anatomically.

Dermal ultrasound measurements for bone quality assessment : An investigation of advanced glycation endproducts derived from confocal fluorescence microscopy.

Bone quality is increasingly being recognized in the assessment of fracture risk. Nonenzymatic collagen cross-linking with the accumulation of advanced glycation end products stiffens and embrittles collagen fibers thus increasing bone fragility. Echogenicity is an ultrasound (US) parameter that provides information regarding the skin collagen structure. We hypothesized that both skin and bone collagen degrade in parallel fashion. Prospectively collected data of 110 patients undergoing posterior lumbar fusion was analyzed. Preoperative skin US measurements were performed in the lumbar region to assess dermal thickness and echogenicity. Intraoperative bone biopsies from the posterior superior iliac spine were obtained and analyzed with confocal fluorescence microscopy for fluorescent advanced glycation endproducts (fAGEs). Pearson's correlation was calculated to examine relationships between  (1) US and fAGEs, and (2) age and fAGEs stratified by sex. Multivariable linear regression analysis with adjustments for age, sex, body mass index (BMI), diabetes mellitus, and hemoglobin A1c (HbA1c) was used to investigate associations between US and fAGEs. One hundred and ten patients (51.9% female, 61.6 years, BMI 29.8 kg/m2 ) were included in the analysis. In the univariate analysis cortical and trabecular fAGEs decreased with age, but only in women (cortical: r = -0.32, p = 0.031; trabecular: r = -0.32; p = 0.031). After adjusting for age, sex, BMI, diabetes mellitus, and HbA1c, lower dermal (ß = 1.01; p = 0.012) and subcutaneous (ß = 1.01; p = 0.021) echogenicity increased with increasing cortical fAGEs and lower dermal echogenicity increased with increasing trabecular fAGEs (ß = 1.01; p = 0.021). This is the first study demonstrating significant associations between skin US measurements and in vivo bone quality parameters in lumbar fusion patients. As a noninvasive assessment tool, skin US measurements might be incorporated into future practice to investigate bone quality in spine surgery patients.

Diagnostic ultrasound and ultrasound-guided injections for peri-articular pain after knee replacement.

OBJECTIVE: The purpose of this technical report is to review the sonographic spectrum of abnormalities accounting for peri-articular pain after knee replacement surgery, as well as to demonstrate the clinical utility of ultrasound in the diagnosis and treatment of this subset of patients. MATERIALS AND METHODS: Utilizing an imaging report database, we performed a search for ultrasound examinations performed by a single radiologist for knee pain after knee arthroplasty at our institution over a 10-year period. The search yielded 63 patients, whom we have categorized by causative pathology, with representative diagnostic and procedural ultrasound images selected for inclusion. RESULTS: Our search yielded multiple causes of peri-articular knee pain after arthroplasty, including medial and lateral retinacular impingement and scarring, iliotibial band or conjoined tendon irritation, popliteus tendon impingement, medial collateral ligament impingement, pes anserine bursitis, and scarring of Hoffa's fat pad. CONCLUSION: While knee arthroplasty is an often-successful procedure, it can be complicated by post-operative peri-articular knee pain. Ultrasound provides a valuable tool for the diagnosis of painful peri-articular knee pathology, as it allows for both static and dynamic evaluation, as well as direct correlation with patient symptoms, and is not confounded by the metal components. In addition to its diagnostic utility, ultrasound can also guide diagnostic and/or therapeutic injections of anesthetic and corticosteroid. Given these advantages, ultrasound is an important tool in managing the painful post-arthroplasty knee.

Sonographic Changes in the Median Nerve Predict Conversion to Surgery after Corticosteroid Injection of the Carpal Tunnel.

BACKGROUND: Risk factors for conversion to surgical management of moderate severity carpal tunnel syndrome are poorly understood. The authors hypothesized that sonographic findings along the carpal tunnel could predict failure of conservative management for carpal tunnel syndrome. METHODS: The authors report on 96 wrists with moderate clinical signs and symptoms of carpal tunnel syndrome. Sonographic evaluation with measurement of median nerve cross-sectional area was performed at three consistent anatomic locations. The authors recorded median nerve morphology, inlet and outlet dimensions of the carpal tunnel, and maximal thickness of the transverse carpal ligament. Steroid injection was performed. Patients were followed up for a minimum of 1 year after injection and progression to surgical management was recorded. RESULTS: A total of 54 percent ( n = 52) of patients converted to surgical management within 1 year after injection. Median nerve cross-sectional area decreased over the course of the carpal tunnel from proximal to distal in 81 of 96 wrists. A greater decrease in cross-sectional area of the median nerve between the pisiform and the hamate was associated with conversion to operative intervention for carpal tunnel syndrome, with the average decrease in median nerve cross-sectional area among those whose conservative treatment failed being 5.01 mm 2 compared with 2.97 mm 2 among those who did not progress to surgical treatment. CONCLUSIONS: This study demonstrates that ultrasound may be an additional tool used by clinicians to better counsel patients about the severity and progression of their disease. Patients who demonstrate a decrease in cross-sectional area of the median nerve along the carpal tunnel demonstrate a higher likelihood of progression to operative management. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Ultrasound-guided injection of the pisotriquetral joint: technique and case series.

PURPOSE: To describe our techniques for ultrasound-guided injection of the pisotriquetral joint (PTJ), and to report our experience in a case series. METHODS: Between 7/1/14 and 11/30/20, we performed 42 injections in 33 patients with ulnar-sided wrist pain, referred by clinicians who suspected the PTJ as the pain generator. There were 16 males and 17 females, average age 46.7 years. The patients were positioned in one of five ways: sitting with the hand maximally supinated; sitting with the hand maximally pronated; supine with the elbow flexed across the chest and the ulnar aspect of the wrist facing upward; supine with the elbow flexed, the arm externally rotated, and the ulnar aspect of the wrist facing upward; prone with the symptomatic hand at their side and the ulnar aspect of the wrist facing upward. RESULTS: The procedures were performed by any of twelve fellowship-trained musculoskeletal radiologists. Fifteen patients reported immediate relief of symptoms, including 6 patients whose pisotriquetral joints were normal sonographically. Four patients underwent subsequent surgical excision of their pisiforms and the fifth underwent arthroscopic debridement of the pisotriquetral joint. CONCLUSION: Ultrasound is a facile imaging modality for guiding pisotriquetral injections, which may be accomplished with a variety of patient positions and injection techniques.

Isolated Traumatic Tear of the Middle Head of the Deltoid Muscle: A Case Report.

CASE: A 27-year-old male pedestrian struck presented with left shoulder pain and weakness 4 months postinjury, with an isolated middle head of the deltoid tear. The patient's pain persisted despite extensive nonoperative management. The deltoid was primarily repaired to the lateral acromion using a transosseous suture repair technique. CONCLUSION: Suture repair of the deltoid to the acromion using transosseous tunnel fixation is a successful treatment for traumatic, isolated tears of the middle head of the deltoid muscle that fail conservative treatment. After surgical repair and physical therapy, our patient recovered full, pain-free range of motion and strength at 6 months.

Utility of lavage in addition to native fluid collection during fluoroscopically guided joint aspiration in infection diagnosis.

Image-guided prosthetic joint aspirations have been criticized in the literature as having poor sensitivity and specificity. Native fluid is typically analyzed for the presence of infection. Joint lavage during fluoroscopically guided aspiration of prosthetic joints is not routinely performed, and the lavage aspirate is not typically analyzed unless native fluid could not be aspirated for culture. This study aims to determine if concordance of culture results from native fluid and an additional joint lavage sample improves sensitivity and specificity in the diagnosis of prosthetic joint infection by fluoroscopically guided joint aspiration. A retrospective review of the fluoroscopically guided joint aspirations at our institution between December 2007 and December 2009 was performed. Data collected from the electronic medical record included culture results for both native fluid and lavage aspirate, histopathology results, final clinical diagnosis, as well as clinical/surgical management. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and likelihood ratio for infection were calculated for the following culture analysis scenarios: native fluid alone; lavage aspirate alone; native fluid; and lavage aspirate. Five hundred sixty-three aspirations, mostly prosthetic joints, were identified in the reviewed time period, of which 397 were sent for both native fluid and lavage aspirate analysis. Concordance between positive culture results from native fluid and joint lavage aspirate markedly increased the likelihood ratio for infection from 23.8 to 138.7 and improved specificity and PPV of fluoroscopically guided joint aspiration, with similar sensitivity and NPV to that of native fluid culture alone.

Ultrasound-guided aspiration of anterior cruciate ligament mucinous cysts in the posterior intercondylar notch: Technique and short-term outcomes.

PURPOSE: To describe our technique of aspirating symptomatic anterior cruciate ligament (ACL) mucinous cysts in the posterior intercondylar notch with ultrasound guidance, and to detail short-term patient outcomes. METHODS: We identified 13 patients from February 2008 to May 2020 who underwent ultrasound-guided aspiration of symptomatic ACL mucinous cysts in the posterior intercondylar notch. Post-procedural imaging was reviewed to evaluate the degree of cyst decompression. Needle size was noted. Post-procedural symptomatology was also assessed. RESULTS: No or minimal fluid was initially aspirated in 11/13 (84.6%) patients. For the two patients in which the cysts were aspirated completely with initial needle placement, with no need for lavage, a 13-gauge trocar was utilized. Of the remaining cysts, 10/11 were aspirated with an 18-gauge needle and one with a 20-gauge needle. Subsequent lavage was performed in 10 of the remaining 11 patients. After lavage, in eight there was a reduction of at least 50% volume by retrospective image interpretation; of 25% to 50% volume in one patient and of less than 25% volume in one patient. Five of the 13 patients reported immediate post-procedural symptomatic relief. In the other patients, immediate efficacy or post-procedural symptomatology was not documented. CONCLUSION: Aspiration of symptomatic ACL mucinous cysts is a safe procedure and can provide symptomatic relief that may be temporary, but useful clinically. We recommend needles larger than 18 gauge for the best chance of successful aspiration.

Ultrasound of the distal biceps brachii tendon using four approaches: reproducibility and reader preference.

OBJECTIVES: To determine which sonographic appearance of the distal biceps brachii tendon (DBBT) is preferred by readers, and if images obtained by two different operators are reproducible. METHODS: We performed an IRB-approved prospective sonographic evaluation of the DBBT in 50 healthy elbows using four different approaches (anterior, lateral, medial, posterior) performed by two operators. Five musculoskeletal radiologists independently reviewed the images, and ranked the four approaches based on overall appearance of echogenicity of the tendon, visualized length, and visualization of the insertion. RESULTS: The medial approach was preferred in 79.6% of elbows, anterior in 17.6%, lateral in 2.8%, and the posterior approach was never preferred. The difference was statistically significant (P < 0.001). Kappa values for the five readers were 0.61 to 0.8 for choosing the images produced by the medial approach. CONCLUSION: The appearance of the DBBT using the medial approach is preferred by readers and is reproducible between different operators.

Ultrasound of Musculoskeletal Hematomas: Relationship of Sonographic Appearance to Age and Ease of Aspiration.

OBJECTIVE: The purpose of this study was to evaluate the safety and efficacy of ultrasound-guided aspiration of musculoskeletal hematomas, evaluate the associations between the sonographic appearance of hematomas and their age with ease of aspiration, and determine if there is an optimal time frame for aspiration. MATERIALS AND METHODS: A retrospective search of our radiology database was conducted using the keywords "hematoma" and "aspiration" for procedures performed from January 1, 2008, through September 28, 2017, by three fellowship-trained musculoskeletal radiologists. Associations between the ease of aspiration and echotexture of the hematoma and between the ease of aspiration and age of the hematoma were assessed with a marginal ordinal logistic regression model to account for patient-level clusters. Pairwise comparisons of the ease of aspiration between the different echotextures were adjusted for multiple comparisons with the Tukey-Kramer method. This same method was also used to calculate the odds ratio (OR) for the age of the hematoma and ease of aspiration and decompression. Clinical follow-up was assessed for infection and symptomatic relief. RESULTS: The cohort was composed of 148 patients (77 male and 71 female patients) with a mean age of 48 years (age range, 16-80 years). One hundred patients underwent clinical follow-up: There were no instances of infection and all patients reported symptomatic relief. Marginal proportional odds model showed an OR of 3.77 when comparing the ease of aspiration between hypoechoic hematomas and hematomas showing the other echotextures combined (i.e., complex, heterogeneous, echo-genic), which was statistically significant (p = 0.010). The OR of the ease of aspiration in relation to the age of a hematoma for each additional week was 1.03 with a p value of 0.547, which shows that there is no correlation between the age of the hematoma and ease of aspiration. CONCLUSION: Ultrasound-guided aspiration of hematomas is a safe and effective procedure. The sonographic appearance of a hematoma is unrelated to its age. Although a hematoma with a hypoechoic appearance is easier to aspirate than hematomas with other echotextures, the appearance and age of a hematoma should not dissuade one from trying to aspirate it.

Quantitative assessment of change in upper extremity muscle stiffness following fluid injection using shear wave elastography.

OBJECTIVE: To quantitatively assess changes in muscle stiffness following intramuscular saline injection using shear wave elastography (SWE). MATERIALS AND METHODS: Thirty muscles (lateral deltoid (LD), biceps brachii (BB), brachialis, pronator teres (PT), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU)) from fresh-frozen cadaveric specimens were injected with saline under ultrasound guidance. Pre- and post-injection muscle thickness (MT) (mm) and SWE (kPa) measurements were recorded. RESULTS: All muscles demonstrated a decrease in the mean SWE value post-injection, with the largest differences ± standard error noted in the LD (14.76 ± 3.55 kPa, p = 0.021) and brachialis muscles (12.02 ± 2.51 kPa, p = 0.013). Muscle thickness increased following injection, although the degree of changes poorly correlated with the change in SWE. CONCLUSION: In summary, following intramuscular injection of saline injection, a decrease in upper extremity muscle stiffness is detected using SWE. It is important to note that if performing a longitudinal assessment of muscle stiffness after intramuscular injection, saline will likely contribute to a decrease in muscle stiffness in the immediate post-injection time period.