Heterotopic Ossification and Platelet-Rich Plasma in Core Muscle Injuries: A Single-Institution Experience Over 6 Years.

BACKGROUND: A 2015 study of platelet-rich plasma (PRP) for groin injuries in National Football League (NFL) players alerted the authors to the possibility that PRP is associated with heterotopic ossification (HO). The current study of athletes seen between 2014 and 2019 provides a more comprehensive analysis of that observation. PURPOSE/HYPOTHESIS: This report describes the early results of groin surgery for athletes who had experienced failed PRP therapy performed by different practitioners and with an assortment of PRP techniques. The primary goal of this cohort study was to determine short-term clinical outcomes after surgery of PRP-treated patients. It was hypothesized that previous PRP treatment would be associated with the presence of HO among patients with core muscle injuries (CMIs). STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: All athletes seen at 1 institution and identified at their first visit as having received PRP for a CMI were followed and compared with patients with a CMI who had not previously received PRP. Although in many cases HO was observed on clinical examination or imaging, HO was identified intraoperatively in all surgical cases and confirmed pathologically. Successful surgery was defined as return to play at previously high levels of performance or greater as determined by the athletes' own assessments. All patients who had received PRP were followed for ≥2 years. RESULTS: Among 3642 patients with a new CMI seen between 2014 and 2019, 68 (1.9%) patients developed HO within the core muscles and/or adjacent soft tissues. Of the 68 patients, 60 (88.2%) were men, and the mean age was 34.5 years. Of the 68 patients, 62 (91.2%) were athletes and 44 (64.7%) had been treated previously with PRP. HO was observed in 24 (0.7%) patients without previous PRP treatment. Three athletes who received PRP retired early from sports because of HO and scar issues. In total, 22 of 28 (78.6%) NFL players who received PRP developed HO, compared with 0 (0%) of 28 randomly selected, age-, position-, and injury-matched NFL players. After surgical repair, 3-month success rates were 67.9% and 96.4%, respectively, in the PRP and non-PRP groups (P = .006). By 6 months postoperatively, PRP-treated patients were back to similarly high success rates compared with the non-PRP cohort. Scar tissue issues played a prominent role in the relative delay in definitive success. CONCLUSION: The present, more comprehensive study confirms the previous preliminary analysis that treating CMIs with PRP may be associated with HO.

Pediatric thrower's elbow: maturation-dependent MRI findings in symptomatic baseball players.

BACKGROUND: Elbow pain is common among youth baseball players and elbow MRI is increasingly utilized to complement the clinical assessment. OBJECTIVE: To characterize, according to skeletal maturity, findings on elbow MRI from symptomatic youth baseball players. MATERIALS AND METHODS: This IRB-approved, HIPAA-compliant retrospective study included pediatric (<18 years of age) baseball players with elbow pain who underwent MRI examinations between 2010 and 2021. Two radiologists, blinded to the outcome, independently reviewed examinations to categorize skeletal maturity and to identify osseous and soft tissue findings with consensus used to resolve discrepancies. Findings were compared between skeletally immature and mature patients and logistic regression models identified predictors of surgery. RESULTS: This study included 130 children (115 boys, 15 girls): 85 skeletally immature and 45 mature (12.8±2.3 and 16.2±1.0 years, respectively, p<0.01). Kappa coefficient for interobserver agreement on MRI findings ranged from 0.64 to 0.96. Skeletally immature children, when compared to mature children, were more likely to have elbow effusion (27%, 23/85 vs 9%, 4/45; p=0.03), medial epicondyle marrow edema (53%, 45/85 vs 16%, 7/45; p<0.01), avulsion fracture (19%, 16/85 vs 2%, 1/45; p=0.02), and juvenile osteochondritis dissecans (OCD, 22%, 19/85 vs 7%, 3/45; p=0.04), whereas skeletally mature children were more likely to have sublime tubercle marrow edema (49%, 22/45 vs 11%, 9/85; p<0.01) and triceps tendinosis (40%, 18/45 vs 20%, 17/85; p=0.03). Intra-articular body (OR=4.2, 95% CI 1.5-47.8, p=0.02) and osteochondritis dissecans (OR=3.7, 95% CI 1.1-11.9, p=0.03) were independent predictors for surgery. CONCLUSION: Differential patterns of elbow MRI findings were observed among symptomatic pediatric baseball players based on regional skeletal maturity. Intra-articular body and osteochondritis dissecans were independent predictors of surgery.

Extensor carpi ulnaris tendon pathology and ulnar styloid bone marrow edema as diagnostic markers of peripheral triangular fibrocartilage complex tears on wrist MRI: a case-control study.

OBJECTIVES: To evaluate extensor carpi ulnaris (ECU) tendon pathology and ulnar styloid process bone marrow edema (BME) as diagnostic MRI markers for peripheral triangular fibrocartilage complex (TFCC) tears. METHODS: One hundred thirty-three patients (age range 21-75, 68 females) with wrist 1.5-T MRI and arthroscopy were included in this retrospective case-control study. The presence of TFCC tears (no tear, central perforation, or peripheral tear), ECU pathology (tenosynovitis, tendinosis, tear or subluxation), and BME at the ulnar styloid process were determined on MRI and correlated with arthroscopy. Cross-tabulation with chi-square tests, binary logistic regression with odds ratios (OR), and sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were used to describe diagnostic efficacy. RESULTS: On arthroscopy, 46 cases with no TFCC tear, 34 cases with central perforations, and 53 cases with peripheral TFCC tears were identified. ECU pathology was seen in 19.6% (9/46) of patients with no TFCC tears, in 11.8% (4/34) with central perforations and in 84.9% (45/53) with peripheral TFCC tears (p < 0.001); the respective numbers for BME were 21.7% (10/46), 23.5% (8/34), and 88.7% (47/53) (p < 0.001). Binary regression analysis showed additional value from ECU pathology and BME in predicting peripheral TFCC tears. The combined approach with direct MRI evaluation and both ECU pathology and BME yielded a 100% positive predictive value for peripheral TFCC tear as compared to 89% with direct evaluation alone. CONCLUSIONS: ECU pathology and ulnar styloid BME are highly associated with peripheral TFCC tears and can be used as secondary signs to diagnose tears. KEY POINTS: • ECU pathology and ulnar styloid BME are highly associated with peripheral TFCC tears and can be used as secondary signs to confirm the presence of TFCC tears. • If there is a peripheral TFCC tear on direct MRI evaluation and in addition both ECU pathology and BME on MRI, the positive predictive value is 100% that there will be a tear on arthroscopy compared to 89% with direct evaluation alone. • If there is no peripheral TFCC tear on direct evaluation and neither ECU pathology nor BME on MRI, the negative predictive value is 98% that there will be no tear on arthroscopy compared to 94% with direct evaluation alone.

Postoperative MR Imaging of the Pubic Symphysis and Athletic Pubalgia.

MR imaging evaluation can be valuable in patients with prior surgery for athletic pubalgia presenting with new, recurrent, or persistent groin pain. The clinical and interventional history as well as comparison with preoperative imaging is essential for imaging interpretation. Imagers should be aware of expected and unexpected postoperative findings. MR imaging findings concerning for infection, new injury, contralateral injury, or concomitant sources of symptoms (such as hip pathology) should be reported when present.

Spotty Bone Marrow: A Frequent MRI Finding in the Feet of Ballet Dancers.

INTRODUCTION: Bone marrow signal abnormalities on magnetic resonance imaging (MRI) are common in athletes. However, few studies evaluate the MRI appearance of bone marrow in the feet of ballet dancers. Our study aims to describe the "spotty bone marrow" (SBM) pattern in the tarsal bones of a cohort of ballet dancers, establishing its prevalence, distribution, potential associations, and evolution.
Methods: Eighty-six MRIs of 68 ankles in 56 ballet dancers were retrospectively reviewed for mar- row signal alterations, which were classified as focal or SBM (defined as patchy fluid-sensitive signal hyperintensity spanning more than one location or tarsal bone). When SBM involved the talus, its anatomic distribution in the bone and morphologic pattern were recorded. Additional osseous and soft tissue findings were documented. For subjects with more than one MRI of the same ankle, the SBM's evolution was monitored.
Results: Spotty bone marrow was identified in 44 ankles (65%). Spotty bone marrow was isolated to the talus (44%), present in all tarsal bones (25%), or distributed between the talus and one to three other tarsal bones (31%). In the talus, The SBM involved the entire bone (65%), the neck and body (31%), or the head and neck (4%). The SBM most commonly showed a random morphologic pattern (87%) but occasionally showed a peripheral predominance (13%). There was no statistically significant difference in the prevalence of other pathologies in ankles with and without SBM. In eight ankles with a follow-up MRI, the SBM worsened in one, remained stable in two, and improved in five ankles. None progressed to a stress fracture.
Conclusion: Spotty bone marrow is an MRI finding frequently encountered in ballet dancers. It is usually self-limiting and should not be misinterpreted as a more aggressive pathology.

Ultrasound-guided Procedures Allow Delay of Definitive Treatment for Core Muscle Injuries.

INTRODUCTION: Core muscle injuries (CMI) are common in every sport. To minimize lost playing time, providers apply various nonsurgical treatments, including platelet-rich plasma, corticosteroids, ultrasound (US)-guided percutaneous tenotomy, and prolotherapy. Limited data exist with regard to their effectiveness. We chose to review a cohort of consecutive professional and collegiate athletes who sustained CMI at various points within their seasons and underwent a combination of US-guided percutaneous needle "tenotomy" and corticosteroid injections to complete the remainder of their seasons. METHODS: Twenty-five consecutive collegiate or professional athletes with CMI involving the rectus abdominis-adductor aponeurotic plate were included in this retrospective study. Athletes with concomitant symptomatic hip femoroacetabular impingement were included in the study. The primary outcome measure was whether athletes completed their seasons. Secondary measures were weeks played after the procedures (delay until surgery), need for repeat procedures, and outcomes after eventual surgery. Postoperative performance was assessed via interviews at 6 wk and 6 months postoperatively. RESULTS: Twenty-one of 25 (84%) athletes completed their seasons. On average, athletes returned to play 3 d (range, 1-9 d) after the procedures. Surgical repair was delayed a mean of 18 wk (range, 2-44 wk). Seven athletes had concomitant symptomatic femoroacetabular impingement and six underwent combined hip arthroscopy and core muscle repairs. Among 17 patients who eventually had core muscle surgery alone (no hip surgery), 82% (14 of 17) reported performing at their preinjury level at 6 wk. At 6 months, 96% of postop athletes (22 of 23) reported performing at their preinjury level. CONCLUSIONS: Temporizing CMI with US-guided percutaneous tenotomy and corticosteroid injections is effective in allowing continued sport participation among high-level athletes and does not negatively affect postoperative outcomes.

Prevalence of lateral patellofemoral maltracking and associated complications in patients with Osgood Schlatter disease.

OBJECTIVE: To evaluate adults with history of Osgood Schlatter disease (OSD) for imaging features of lateral patellofemoral maltracking. METHODS: In a span of four years, 10,181 unique non-contrast knee MRIs were performed on patients aged 20-50. Patients with acute trauma, prior surgery, and synovial pathologies were excluded. 171 exams had imaging findings of OSD, and an age-matched control group of 342 patients without OSD was randomly selected. Two radiologists retrospectively reviewed MRIs for features of lateral patellofemoral maltracking. Maltracking was defined as edema in superolateral Hoffa's fat or a tibial tuberosity-trochlear groove (TT-TG) distance ≥20 mm with either patellar tilt/translation. Binomial logistic regression identified predictors of maltracking in OSD. Optimal TT-TG distance to indicate maltracking was determined by receiver operating characteristic curve. RESULTS: 59% (101/171) of the knees with OSD showed findings of maltracking, with patella alta, trochlear dysplasia, and quadriceps tendinosis as significant predictors of maltracking (p < 0.001). Patellofemoral chondrosis was present in 63% (107/171), with maltracking contributing to higher grade chondrosis more so than increasing age (OR 8.4 versus 1.07). 13 mm was the optimal cut-off TT-TG distance to indicate maltracking (sensitivity 83%, specificity 80%). The prevalence of maltracking in the control group was 15% (p < 0.001 compared with the OSD group). CONCLUSION: Adults with sequelae of OSD are at high risk of maltracking and are likely to develop patellofemoral chondrosis. A lower threshold for identifying maltracking patients, including a lower cut-off TT-TG distance can help identify those at risk. Radiologists should maintain a high index of suspicion for maltracking in adults with OSD to guide clinical intervention.

Painful type II os naviculare: introduction of a standardized, reproducible classification system.

OBJECTIVE: To provide a novel MRI classification system for the symptomatic type II os naviculare by creating a standardized grading of associated bone marrow edema (BME) and correlating with patient symptoms. METHODS: BME was classified on an ordinal scale: grade 1, faint signal immediately adjacent to the synchondrosis; grade 2, intermediate signal within the os and navicular tuberosity without extending to the navicular body; grade 3, intense signal extending to the navicular body. BME on 59 MRIs was independently graded by three radiologists. Inter- and intra-observer agreement was analyzed using intraclass correlation coefficient. Univariate and multivariate analyses assessed for patient and imaging characteristics predictive of subjective pain score. A cohort of 82 patients without BME represented a control group. RESULTS: Inter-observer agreement of BME grade was 0.95 (CI 0.93-0.97) and intra-observer was 0.92 (CI 0.87-0.96), indicating excellent agreement. In patients with BME, predictors of more severe pain were longer duration of pain (p = 0.02) and presence of soft tissue edema overlying the os naviculare (p < 0.001). One hundred percent of subjects with BME localized their pain to the medial midfoot (59/59) versus 25.6% (21/82) of controls (p < 0.001). CONCLUSIONS: This novel grading system provides reliable quantification of BME associated with os naviculare, which is a specific cause of medial foot/ankle pain. Early diagnosis is important as pain severity worsens with longer duration of symptoms. Pain severity is correlated with soft tissue edema overlying the os, which may be secondary to extrinsic compression, reactive to biomechanical stress, or reflect direct trauma.

Predicting osteomyelitis in patients whose initial MRI demonstrated bone marrow edema without corresponding T1 signal marrow replacement.

PURPOSE: We endeavored to determine which characteristics of diabetic ulcers portend the strongest risk for osteomyelitis in patients whose initial T1-weighted imaging was normal. By determining which features have a greater risk for osteomyelitis, clinicians can treat patients more aggressively to reduce the sequela of inadequately treated osteomyelitis. MATERIALS AND METHODS: We performed a retrospective analysis of MR imaging from 60 pedal ulcers with suspected osteomyelitis. Ulcer dimensions and depth were measured. Ratios of marrow ROI/joint fluid ROI on T2/STIR sequences were obtained. Progression to osteomyelitis on subsequent MRI was characterized by loss of normal marrow signal on T1-weighted images. Statistical analysis was performed with a two-sample t test and Cox proportional hazard model. A p value < 0.05 was used as the threshold for statistical significance. RESULTS: Sixty MR exams were identified. Thirty-four progressed to osteomyelitis. Marrow ROI/joint fluid ratios averaged 65% in the osteomyelitis group, and 45% in the non-osteomyelitis group, p < 0.001. ROI ratios > 53% had a 6.5-fold increased risk of osteomyelitis, p < 0.001. Proximity to bone averaged 6 mm in the osteomyelitis group and 9 mm in the non-osteomyelitis group, p = 0.02. Ulcer size averaged 4 cm2 in the osteomyelitis group versus 2.4 cm2 in the non-osteomyelitis group, p = 0.07. Ulcers greater than 3 cm2 has a 2-fold increase in the risk of osteomyelitis, p = 0.04. CONCLUSION: Increasing bone marrow ROI signal/joint fluid ratios on T2/STIR images were the strongest risk factors for developing osteomyelitis, while ulcer size and depth are weaker predictors.

Value of response to anesthetic injection during hip MR arthrography to differentiate between intra- and extra-articular pathology.

PURPOSE: To determine the value of anesthetic injection during hip MR arthrography (anesthetic MRA) to differentiate between intra- and extra-articular pathology in patients with hip pain. MATERIALS AND METHODS: This retrospective study was IRB-approved and HIPAA-compliant. We included 75 consecutive adult patients (46 women, mean age 38 ± 13 years) who were referred for MRA. All patients underwent a focused hip examination including active flexion, passive flexion, and passive flexion with internal and external rotation, immediately prior to injection. Anesthetic MRA was performed following fluoroscopically guided intra-articular injection of contrast mixed with anesthetic. Following the injection, the hip examination was repeated, and the pain response was recorded. Clinical records, including response to corticosteroid injections, physical therapy notes, and operative reports were reviewed for verification of intra- and extra-articular pathology as the source of hip pain (gold standard). The positive (PPV) and negative predictive values (NPP) of anesthetic MRA to differentiate between intra- and extra-articular pathology were calculated. RESULTS: On MRI, 41 patients had only intra-articular and 5 patients only extra-articular pathology, while 29 patients had both, intra- and extra-articular pathology. Forty-three patients had pain relief and 32 patients had no pain relief after anesthetic injection. PPV of anesthetic MRA to detect intra-articular pathology was 91% and NPV was 67%. CONCLUSION: Anesthetic MRA can be used as an adjunct to define the origin of hip pain. A positive response suggests intra-articular pathology which can be helpful to localize the source of pain in equivocal cases where both intra- and extra-articular pathology are evident on MRI.

Second opinions in orthopedic oncology imaging: can fellowship training reduce clinically significant discrepancies?

OBJECTIVE: To determine factors that lead to significant discrepancies in second-opinion consultation of orthopedic oncology patients, and particularly if musculoskeletal fellowship training can decrease clinically significant discrepancies. METHODS: A PACS database was queried for secondary reads on outside cross-sectional imaging studies, as requested by orthopedic oncology from 2014 to 2017. Comparison of original and secondary reports was performed using a published seven-point scale that defines clinically significant discrepancies. An online search was performed for each original radiologist to record if a fellowship in musculoskeletal imaging was completed. Additionally, years of post-residency experience, number of Medicare part B patients billed per year (marker of practice volume), and average hierarchical condition category for each radiologist (marker of practice complexity) was recorded. RESULTS: A total of 571 patients met the inclusion criteria, with 184 cases initially interpreted by an outside fellowship trained musculoskeletal (MSK) radiologist and 387 cases initially interpreted by a non-MSK trained radiologist. The rate of clinically significant discrepancy was 9.2% when initially interpreted by MSK radiologists compared with 27.9% when initially performed by non-MSK radiologists (p < 0.05). After adjustment by both patient characteristics and radiologist characteristics, the likelihood of clinically significant discrepancies was greater for initial interpretations by non-MSK radiologists compared with MSK radiologists (OR = 1.36; 95% CI = 1.23-2.49). CONCLUSION: In orthopedic oncology patients, the rate of clinically significant discrepancies was significantly higher when initially interpreted by non-MSK radiologists compared with MSK radiologists. The lower rate of clinically significant discrepancies demonstrates that subspecialty training may direct more appropriate diagnosis and treatment.

Providing Value-Based Service to a Sprawling Orthopaedics Practice.

Health care in the United States is changing, and diagnostic radiology is attempting to adapt to the new norm. A view of the landscape shows mergers, acquisitions, and radiology practices becoming larger. Musculoskeletal (MSK) radiology is trending toward subspecialization, and orthopaedic surgery practices are demanding quality, convenience, and efficiency in imaging services. In other industries, optimization of operations and strategic deployment of resources are standard, but radiology is not quite there yet. This article details our opportunities in MSK imaging to increase market share through service, added value, and improved operational efficiency.

Lumbosacral transitional vertebrae: significance of local bone marrow edema at the transverse processes.

OBJECTIVE: To evaluate the association between low back pain and bone marrow edema in lumbosacral transitional vertebra (LSTV) transverse processes, and to assess the prevalence of LSTV in a physically active population. MATERIALS AND METHODS: Individuals with LSTV on coronal MRI studies were identified in a retrospective review by keyword search from PACS. In total, 140 cases were reviewed by two fellowship-trained musculoskeletal radiologists. Data on associated low back pain were collected from patient records at the time of the imaging. RESULTS: Bone marrow edema was observed in 44% of the cases, but no correlation with low back pain was found. On coronal MRI, the prevalence of LSTV was 2.6%, with type II LSTV being the most common subtype. CONCLUSIONS: No correlation with bone marrow edema at the transverse processes of the LSTV and low back pain was observed. In our selected study population, the prevalence of LSTV was low.

Analysis of a Steerable Needle for Fine Needle Aspiration and Biopsy: Efficiency and Radiation Dose Compared With a Conventional Straight Needle.

PURPOSE: Percutaneous computed tomography (CT)-guided needle biopsy has proven to be an efficacious method for sampling of many soft tissue lesions, especially deep-seated masses in the abdomen and pelvis. This study sought to test the potential for a novel steerable needle to improve localization and to reduce procedure duration and radiation dose compared with a conventional straight needle. MATERIAL AND METHODS: A fresh, raw meat sample (lean bovine flank) was imbedded with cylindrical radiopaque and radiolucent obstacles designed to simulate vessels (radiolucent objects) and bones (radiopaque objects) on CT. A pit-containing olive (partially radiopaque) was imbedded beyond the obstacles to represent the target. Two sites on the surface of the meat were selected and marked to determine initial needle placement. Two radiologists with different levels of experience proceeded to position a straight needle and the steerable needle from each skin site to the target using CT guidance as efficiently as possible, avoiding the obstacles. The total positioning time, the number of CT scans required for positioning, and the number of repositioning events (partial withdrawal followed by advancement) were tracked for the straight and steerable needles. RESULTS: For the straight needle, total time to reach the target was 499 to 667 seconds (mean, 592 seconds); for the steerable needle, total time to reach the target was 281 to 343 seconds (mean, 309 seconds), on average, 48% lower. The number of CT scans needed for needle positioning averaged 6.25 for the straight needle and 3.5 for the steerable needle, which is 44% lower. Repositioning events (withdrawing and readvancing the needle) ranged from 3 to 10 for the straight needle (mean, 6.5) and 0 for the steerable needle. CONCLUSIONS: Using an in vitro model embedded with obstacles, the steerable needle performed better than a straight needle with regard to procedure time, needle repositioning events, and CT scans required for placement.

Clinical Impact of Second-Opinion Musculoskeletal Subspecialty Interpretations During a Multidisciplinary Orthopedic Oncology Conference.

PURPOSE: To analyze the impact on clinical management when musculoskeletal radiologists render second-opinion consultations during multidisciplinary orthopedic oncology conference. METHODS: A PACS database was searched for secondary interpretations on outside MRI studies reviewed during a multidisciplinary orthopedic oncology conference from January 2014 to December 2016. Reports were compared with the original interpretations, when available. Reports were categorized using a 7-point scale: I (no discrepancy), II (undetected clinically insignificant abnormality), III (clinically insignificant difference in interpretation), IV (difference in imaging follow-up recommendation), V (equivocal initial interpretation with subsequent definitive subspecialty interpretation), VI (clinically significant difference in interpretation), VII (failure to detect a clinically significant abnormality). RESULTS: A total of 409 patients met inclusion criteria, with an average age of 47.9 ± 19.2. There were 91 (22.2%) instances of discrepant interpretations resulting in clinically significant differences in management; 67 (16.4%) were category VI and 24 (5.9%) were category VII. An additional 72 subjects (17.6%) were identified as category IV and 28 (6.8%) as category V, yielding at total of 191 (46.7%) clinically relevant discrepancies. When pathology was available, the secondary consultations were concordant in 57 of 61 cases (93.4%) and the outside interpretations were concordant in 39 of 61 cases (63.9%, P < .05). CONCLUSION: A 22.2% rate of clinically significant difference was observed between primary and secondary interpretations. The substantial rate of clinically relevant discrepancies demonstrates that subspecialty expertise often changed the primary diagnosis. Thus, by participating in a multidisciplinary team, subspecialty radiologists have a unique opportunity to help direct appropriate treatment plans.

Algorithm for Imaging the Hip in Adolescents and Young Adults.

The imager's role in diagnosing prearthritic hip syndromes has increased significantly in the past 10 years. As surgical and nonsurgical treatment algorithms for mechanical syndromes including femoroacetabular impingement and acetabular dysplasia have evolved, clinicians have grown increasingly dependent on radiography, MR imaging, MR arthrography, and even computed tomography to confirm diagnoses and support the need for potential intervention. Musculoskeletal radiologists should help referrers navigate available imaging options and protocols, while using both clinical information and imaging findings to arrive at a diagnosis that adds value to the treatment plan.

Potential Utility of a Combined Approach with US and MR Arthrography to Image Medial Elbow Pain in Baseball Players.

Purpose To evaluate a combined imaging approach with both ultrasonography (US; conventional US and valgus stress US) and magnetic resonance (MR) arthrography in baseball players with medial elbow pain. Materials and Methods Institutional review board approval was obtained and the requirement for informed consent was waived. The study is compliant with HIPAA. Baseball players with medial elbow pain underwent US in addition to MR arthrography. Findings were assessed with each modality alone and both combined in this retrospective investigation. For the evaluation of ulnar collateral ligament (UCL) tears with stress US, the interval gapping of the medial elbow joint was measured between rest and valgus stress both at the injured and at the uninjured (contralateral) elbow. Surgical or arthroscopic correlation was available as the so-called gold standard. McNemar tests compared the accuracies of the imaging modalities. Results In this study, 144 baseball players had 191 findings of medial elbow pain, including 53 UCL tears. With stress US, joint gapping at the injured elbow greater than 1.0 mm compared with the contralateral elbow yielded a sensitivity, specificity, and accuracy of 96%, 81%, and 87%, respectively, for diagnosing UCL tears. With MR arthrography, the sensitivity, specificity, and accuracy for UCL tears were 81%, 91%, and 88%, respectively, and increased to 96% (P = .013, McNemar test), 99% (P = .023), and 98% (P < .001), respectively, when combined with US to a dual modality MR and US approach. For 31 patients with ulnar neuritis, the sensitivity, specificity, and accuracy increased from 74%, 92%, and 88%, respectively, with MR arthrography alone to 90% (P = .07, McNemar test), 100% (P < .001), and 98% (P < .001) combined with US. For the 59 myotendinous and the 48 osteochondral diagnoses, the sensitivity, specificity, and accuracy with MR arthrography alone were 93%, 93%, and 93%, and 94%, 98%, and 97%, respectively, with no additional diagnostic value from US. Conclusion The combined approach with both MR arthrography and US shows higher accuracy than each modality alone for the assessment of medial elbow pain. (©) RSNA, 2016.