Radiographic and Advanced Imaging Evaluation of Posterior Shoulder Instability.

PURPOSE OF REVIEW: Posterior shoulder instability is an uncommon but important cause of shoulder dysfunction and pain which may occur as the result of seizure, high energy trauma, or repetitive stress related to occupational or sport-specific activities. This current review details the imaging approach to the patient with posterior shoulder instability and describes commonly associated soft tissue and bony pathologies identified by radiographs, CT, and MR imaging. RECENT FINDINGS: Advances in MR imaging technology and techniques allow for more accurate evaluation of bone and soft tissue pathology associated with posterior shoulder instability while sparing patients exposure to radiation. Imaging can contribute significantly to the clinical management of patients with posterior shoulder instability by demonstrating the extent of associated injuries and identifying predisposing anatomic conditions. Radiologic evaluation should be guided by clinical history and physical examination, beginning with radiographs followed by CT and/or MRI for assessment of osseous and soft tissue pathology. Synthesis of a patient's clinical history, physical exam findings, and radiologic examinations should guide clinical management.

Deep-learning for automated detection of MSU deposits on DECT: evaluating impact on efficiency and reader confidence.

Introduction: Dual-energy CT (DECT) is a non-invasive way to determine the presence of monosodium urate (MSU) crystals in the workup of gout. Color-coding distinguishes MSU from calcium following material decomposition and post-processing. Manually identifying these foci (most commonly labeled green) is tedious, and an automated detection system could streamline the process. This study aims to evaluate the impact of a deep-learning (DL) algorithm developed for detecting green pixelations on DECT on reader time, accuracy, and confidence. Methods: We collected a sample of positive and negative DECTs, reviewed twice-once with and once without the DL tool-with a 2-week washout period. An attending musculoskeletal radiologist and a fellow separately reviewed the cases, simulating clinical workflow. Metrics such as time taken, confidence in diagnosis, and the tool's helpfulness were recorded and statistically analyzed. Results: We included thirty DECTs from different patients. The DL tool significantly reduced the reading time for the trainee radiologist (p = 0.02), but not for the attending radiologist (p = 0.15). Diagnostic confidence remained unchanged for both (p = 0.45). However, the DL model identified tiny MSU deposits that led to a change in diagnosis in two cases for the in-training radiologist and one case for the attending radiologist. In 3/3 of these cases, the diagnosis was correct when using DL. Conclusions: The implementation of the developed DL model slightly reduced reading time for our less experienced reader and led to improved diagnostic accuracy. There was no statistically significant difference in diagnostic confidence when studies were interpreted without and with the DL model.

MR elastography-based slip interface imaging (SII) for functional assessment of myofascial interfaces: A feasibility study.

PURPOSE: Abnormal adherence at functional myofascial interfaces is hypothesized as an important phenomenon in myofascial pain syndrome. This study aimed to investigate the feasibility of MR elastography (MRE)-based slip interface imaging (SII) to visualize and assess myofascial mobility in healthy volunteers. METHODS: SII was used to assess local shear strain at functional myofascial interfaces in the flexor digitorum profundus (FDP) and thighs. In the FDP, MRE was performed at 90 Hz vibration to each index, middle, ring, and little finger. Two thigh MRE scans were performed at 40 Hz with knees flexed and extended. The normalized octahedral shear strain (NOSS) maps were calculated to visualize myofascial slip interfaces. The entropy of the probability distribution of the gradient NOSS was computed for the two knee positions at the intermuscular interface between vastus lateralis and vastus intermedius, around rectus femoris, and between vastus intermedius and vastus medialis. RESULTS: NOSS map depicted distinct functional slip interfaces in the FDP for each finger. Compared to knee flexion, clearer slip interfaces and larger gradient NOSS entropy at the vastus lateralis-vastus intermedius interface were observed during knee extension, where the quadriceps are not passively stretched. This suggests the optimal position for using SII to visualize myofascial slip interface in skeletal muscles is when muscles are not subjected to any additional force. CONCLUSION: The study demonstrated that MRE-based SII can visualize and assess myofascial interface mobility in extremities. The results provide a foundation for investigating the hypothesis that myofascial pain syndrome is characterized by changes in the mobility of myofascial interfaces.

A Unique Case of Familial Expansile Osteolysis: Findings on 99mTc-MDP Bone Scan.

ABSTRACT: Familial expansile osteolysis is an exceedingly rare autosomal dominant bone dysplasia, which can have overlapping features with Paget disease and expansile skeletal hyperphosphatasia. We present a novel case of familial expansile osteolysis evaluated on 99mTc-MDP bone scan with correlative radiographs and CT.

Incidence of complications related to shoulder arthroplasties identified on computed tomography.

PURPOSE: Determine incidence of shoulder arthroplasty complications identified on computed tomography (CT). MATERIALS AND METHODS: Retrospective institutional database review of patients with shoulder arthroplasties who underwent CT between 01/2006-11/2021 at a tertiary academic referral center with subspecialized orthopedic shoulder surgeons. CT reports were reviewed for arthroplasty type and complication. Data were stratified and summarized. Associations between complications and arthroplasty types were determined with Chi-squared goodness of fit test. RESULTS: Eight hundred twelve CTs in 797 unique patients were included (438 (53.9%) females and 374 (46.1%) males; mean age 67 ± 11 years). There were 403 total shoulder arthroplasties (TSA), 317 reverse total shoulder arthroplasties (rTSA), and 92 hemiarthroplasties (HA). Complications were present in 527/812 (64.9%) and incidences were: loosening/aseptic osteolysis 36.9%, periprosthetic failure 21.6%, periprosthetic fracture 12.3%, periprosthetic dislocation 6.8%, joint/pseudocapsule effusion 5.9%, prosthetic failure 4.8%, infection 3.8%, and periprosthetic collection 2.1%. Complications per arthroplasty were: 305/403 (75.7%) TSAs, 176/317 (55.5%) rTSAs, and 46/92 (50%) HAs (p < 0.001). Periprosthetic fracture (20.8%), prosthetic dislocation (9.8%), and prosthetic failure (7.9%) were highest in rTSAs (p < 0.001, p < 0.013, p < 0.001, respectively). Loosening/aseptic osteolysis most frequent in TSAs (54.1%) (p < 0.001). Periprosthetic failure most frequent in HA (32.6%) (p < 0.001). Significant associations were identified with joint/pseudocapsule effusion and loosening/aseptic osteolysis (p = 0.04) and prosthetic dislocation (p < .001). CONCLUSION: In this single tertiary academic referral center cohort, the incidence of shoulder arthroplasty complication identified on CT was 64.9% and the most commonly occurring complication was loosening/aseptic osteolysis (36.9%). TSA had the highest incidence of complication (75.7%).

7T for clinical imaging of benign peripheral nerve tumors: preliminary results.

PURPOSE: MRI has become an essential diagnostic imaging modality for peripheral nerve pathology. Early MR imaging for peripheral nerve depended on inferred nerve involvement by visualizing downstream effects such as denervation muscular atrophy; improvements in MRI technology have made possible direct visualization of the nerves. In this paper, we share our early clinical experience with 7T for benign neurogenic tumors. MATERIALS: Patients with benign neurogenic tumors and 7T MRI examinations available were reviewed. Cases of individual benign peripheral nerve tumors were included to demonstrate 7T MRI imaging characteristics. All exams were performed on a 7T MRI MAGNETOM Terra using a 28-channel receive, single-channel transmit knee coil. RESULTS: Five cases of four pathologies were selected from 38 patients to depict characteristic imaging features in different benign nerve tumors and lesions using 7T MRI. CONCLUSION: The primary advantage of 7T over 3T is an increase in signal-to-noise ratio which allows higher in plane resolution so that the smallest neural structures can be seen and characterized. This improvement in MR imaging provides the opportunity for more accurate diagnosis and surgical planning in selected cases. As this technology continues to evolve for clinical purposes, we anticipate increasing applications and improved patient care using 7T MRI for the diagnosis of peripheral nerve masses.

Osteoid osteomas of the hands and feet: a series of 71 cases.

Osteoid osteomas typically arise in the long bones of extremities. Patients often report pain relieved by NSAIDS, and radiographic findings are often sufficient for diagnosis. However, when involving the hands/feet, these lesions may go unrecognized or misdiagnosed radiographically due to their small size and prominent reactive changes. The clinicopathologic features of this entity involving the hands and feet are not well-described. Our institutional and consultation archives were searched for all cases of pathologically confirmed osteoid osteomas arising in the hands and feet. Clinical data was obtained and recorded. Seventy-one cases (45 males and 26 females, 7 to 64 years; median 23 years) arose in the hands and feet, representing 12% of institutional and 23% of consultation cases. The clinical impression often included neoplastic and inflammatory etiologies. Radiology studies demonstrated a small lytic lesion in all cases (33/33), the majority of which had a tiny focus of central calcification (26/33). Nearly, all cases demonstrated cortical thickening and/or sclerosis and perilesional edema which almost always had an extent two times greater than the size of the nidus. Histologic examination showed circumscribed osteoblastic lesions with formation of variably mineralized woven bone with single layer of osteoblastic rimming. The most common growth pattern of bone was trabecular (n = 34, 48%) followed by combined trabecular and sheet-like (n = 26, 37%) with only 11 (15%) cases presenting with pure sheet-like growth pattern. The majority (n = 57, 80%) showed intra-trabecular vascular stroma. No case showed significant cytology atypia. Follow up was available for 48 cases (1-432 months), and 4 cases recurred. Osteoid osteomas involving the hands and feet follow a similar age and sex distribution as their non-acral counterparts. These lesions often present with a broad differential diagnosis and may initially be confused with chronic osteomyelitis or a reactive process. While the majority of cases have classic morphologic features on histologic exam, a small subset consists solely of sheet-like sclerotic bone. Awareness that this entity may present in the hands and feet will help pathologists, radiologists, and clinicians accurately diagnose these tumors.

Feasibility of photon-counting CT for femoroacetabular impingement syndrome evaluation: lower radiation dose and improved diagnostic confidence.

OBJECTIVE: The feasibility of low-dose photon-counting detector (PCD) CT to measure alpha and acetabular version angles of femoroacetabular impingement (FAI). MATERIAL AND METHODS: FAI patients undergoing an energy-integrating detector (EID) CT underwent an IRB-approved prospective ultra-high-resolution (UHR) PCD-CT between 5/2021 and 12/2021. PCD-CT was dose-matched to the EID-CT or acquired at 50% dose. Simulated 50% dose EID-CT images were generated. Two radiologists evaluated randomized EID-CT and PCD-CT images and measured alpha and acetabular version angles on axial image slices. Image quality (noise, artifacts, and visualization of cortex) and confidence in non-FAI pathology were rated on a 4-point scale (3 = adequate). Preference tests of standard dose PCD-CT, 50% dose PCD-CT, and 50% dose EID-CT relative to standard dose EID-CT were performed using Wilcoxon Rank test. RESULTS: 20 patients underwent standard dose EID-CT (~ CTDIvol, 4.5 mGy); 10 patients, standard dose PCD-CT (4.0 mGy); 10 patients, 50% PCD-CT (2.6 mGy). Standard dose EID-CT images were scored as adequate for diagnostic task in all categories (range 2.8-3.0). Standard dose PCD-CT images scored higher than the reference in all categories (range 3.5-4, p < 0.0033). Half-dose PCD-CT images also scored higher for noise and cortex visualization (p < 0.0033) and equivalent for artifacts and visualization of non-FAI pathology. Finally, simulated 50% EID-CT images scored lower in all categories (range 1.8-2.4, p < 0.0033). CONCLUSIONS: Dose-matched PCD-CT is superior to EID-CT for alpha angle and acetabular version measurement in the work up of FAI. UHR-PCD-CT enables 50% radiation dose reduction compared to EID while remaining adequate for the imaging task.

Nodular Fasciitis: False Positive on 18F-Piflufolastat and 11C-Choline PET/CT.

ABSTRACT: PET/CT plays a crucial role in the management of prostate cancer with several emerging and established radiopharmaceuticals, including 18 F-piflufolastat and 11 C-choline. These radiotracers are thought to be relatively specific to prostate cancer; however, uptake has also been demonstrated in other benign and malignant lesions. Nodular fasciitis is a rapidly growing benign soft tissue neoplasm that is typically self-limiting. Although a few case reports describe 68 Ga-PSMA uptake in nodular fasciitis, uptake of 11 C-choline and other PSMA-targeted PET probes, including 18 F-piflufolastat, have not previously been reported. We present a novel case of nodular fasciitis demonstrating both 18 F-piflufolastat and 11 C-choline avidity.

Multimodality evaluation of transfascial muscle and other soft tissue herniations of the extremities.

This review illustrates the multimodality assessment of transfascial muscle and other soft tissue herniations of the extremities. Transfascial herniations of the extremities can develop from congenital or acquired disruptions of the deep fascia, resulting in herniation of the underlying muscle, nerve, or soft tissue tumor into the subcutaneous tissues. While most patients present with a painless subcutaneous nodule that may change in size with muscle activation, some may experience focal or diffuse extremity symptoms such as pain and paresthesias. Although the diagnosis may be clinically suspected, radiologic evaluation is useful for definitive diagnosis and characterization. Ultrasound is the preferred modality for initial workup through a focused and dynamic examination. Magnetic resonance imaging can be utilized for equivocal, complicated, and preoperative cases. Computed tomography is less useful in the evaluation of transfascial herniations in the extremities due to similarities in the attenuation between muscle and fascia, which can decrease the conspicuity of small defects.

Evolving Role of Dual-Energy CT in the Clinical Workup of Gout: A Retrospective Study.

BACKGROUND. Dual-energy CT (DECT) allows noninvasive detection of monosodium urate (MSU) crystal deposits and has become incorporated into the routine clinical evaluation for gout at many institutions over the past decade. OBJECTIVE. The purpose of this study was to compare two time periods over the past decade in terms of radiologists' interpretations of DECT examinations performed for the evaluation of gout and subsequent clinical actions. METHODS. This retrospective study included 100 consecutive adult patients who underwent DECT to evaluate for gout in each of two periods (one beginning in March 2013 and one beginning in September 2019). Examinations performed in 2013 were conducted using a second-generation DECT scanner (80 kV [tube A] and 140 kV [tube B] with a 0.4-mm tin filter), and those performed in 2019 were conducted using a third-generation DECT scanner (80 kV [tube A] and 150 kV [tube B] with a 0.6-mm tin filter) that provides improved spectral separation. Original DECT reports were classified as positive, negative, or equivocal for MSU crystals indicative of gout. Joint aspirations occurring after the DECT examinations were recorded on the basis of findings from medical record review. A single radiologist performed a post hoc retrospective blinded image review, classifying examinations as positive, negative, or equivocal. RESULTS. In 2013, 44.0% of DECT examinations were interpreted as positive, 23.0% as negative, and 33.0% as equivocal; in 2019, 37.0% were interpreted as positive, 47.0% as negative, and 16.0% as equivocal (p < .001). The frequency of joint aspiration after DECT was 14.0% in 2013 versus 2.0% in 2019 (p = .002), and that after DECT examinations with negative interpretations was 17.4% in 2013 versus 2.1% in 2019 (p = .02). In post hoc assessment by a single radiologist, the distribution of interpretations in 2013 was positive in 49.0%, negative in 22.0%, and equivocal in 29.0%, and in 2019 it was positive in 39.0%, negative in 50.0%, and equivocal in 11.0% (p < .001). CONCLUSION. When DECT examinations performed for gout in 2013 and 2019 were compared, the frequency of equivocal interpretations was significantly lower in 2019, possibly in relation to interval technologic improvements. Negative examinations were less frequently followed by joint aspirations in 2019, possibly reflecting increasing clinical acceptance of the DECT results. CLINICAL IMPACT. The findings indicate an evolving role for DECT in the evaluation of gout after an institution's routine adoption of the technology for this purpose.

Preoperative ultrasound accurately characterizes surgically confirmed extracranial spinal accessory nerve injuries.

OBJECTIVE: To determine the accuracy of preoperative ultrasound and MRI in surgically confirmed spinal accessory nerve injuries and present the benefits of a multimodality image review. MATERIALS AND METHODS: A retrospective review of 38 consecutive patients referred to a peripheral nerve surgical practice at an academic teaching hospital with surgically confirmed spinal accessory nerve injuries. All cases were reviewed for patient demographics, date and cause of injury, preoperative EMG, and surgical diagnosis and management. Additionally, prospective interpretation of preoperative ultrasound and MRI reports were reviewed for concordance or discordance with the surgical diagnosis. RESULTS: Iatrogenic injury was present in 37 (97%) cases and most commonly a result of an excisional lymph node biopsy (68%). Surgically confirmed spinal accessory nerve injury diagnoses consisted of 25 (66%) stump neuromas and 13 (34%) incomplete nerve injuries. Nine months was the average time from injury to surgery. Twenty-nine patients underwent preoperative ultrasound and/or MRI evaluation: 12 ultrasound only, 10 MRI only, and seven with both ultrasound and MRI. Eighteen (95%) preoperative ultrasound reports compared to four (24%) preoperative MRI reports were concordant with the surgical diagnosis. In the seven cases with both preoperative ultrasound and MRI, six had discordant ultrasound and MRI imaging diagnoses for which the ultrasound was concordant with the surgical diagnoses in all cases. CONCLUSION: Preoperative ultrasound more accurately characterizes spinal accessory nerve injuries compared to MRI and should serve as the modality of choice when a spinal accessory nerve injury is suspected.

Sternoclavicular joint pseudotumor: a clinicopathologic and radiologic study of 25 cases occurring in patients without prior neck dissection.

Pseudotumors of the sternoclavicular joint are rare, poorly characterized pseudoneoplastic lesions previously reported in association with prior neck dissection and thought to result from mechanical instability of the muscles of the shoulder girdle. We report 25 examples of this distinctive process, occurring in patients without a history of neck dissection, typically sent in consultation out of concern for a primary bone or soft-tissue tumor. Cases occurred in 14 women and 11 men (median = 68 years of age) and involved the sternoclavicular joint (17 cases), sternomanubrial joint (2 cases) or other nearby locations (6 cases). The masses ranged from 0.4 to 6.4 cm in size (median = 2.2 cm). Twenty-one patients (84%) had a clinical history of osteoarthritis involving other joints. Clinical follow-up (16 patients; mean = 11.4 months; range = 2-40 months) was uniformly benign, without evidence of recurrent disease. Radiologic review showed changes of osteoarthritis, often with cystic change. Pathologic features included degenerating cartilage, fibrinoid debris, pseudocyst formation, and florid proliferation of myofibroblasts and capillaries. The differential diagnosis of sternoclavicular/sternomanubrial pseudotumors centers around cartilaginous tumors of bone, in particular chondrosarcoma. Careful clinical, radiographic, and pathologic correlations are essential in arriving at the correct diagnosis and avoiding overtreatment.

Percutaneous MR Imaging-Guided Laser Ablation and Cryoablation for the Treatment of Pediatric and Adult Symptomatic Peripheral Soft Tissue Vascular Anomalies.

PURPOSE: To evaluate the safety and effectiveness of percutaneous magnetic resonance (MR) imaging-guided laser ablation and cryoablation for the treatment of symptomatic soft tissue vascular anomalies (VAs) of the trunk and extremities. MATERIALS AND METHODS: An institutional review board-approved retrospective review was undertaken of all pediatric and adult patients who underwent MR imaging-guided and monitored laser ablation and/or cryoablation for the treatment of symptomatic peripheral soft tissue VA. Preablation and postablation MR imaging was independently reviewed. Pain scores on the visual analog scale (0 to 10) and self-reported subjective symptomatic improvement were assessed. Change in VA size and pain scores were compared using a paired t test. RESULTS: Thirty patients (24 females; age, 10-75 years) with 34 VAs were treated for moderate to severe pain (n = 27) or swelling/mass effect (n = 3) with 60 total ablation sessions. The baseline maximum VA diameter was 9.5 cm ± 8.6. At baseline, all VAs (100%) demonstrated variable T2-weighted signal hyperintensity and enhancement. The baseline pain score was 6.4 ± 1.6. Clinical follow-up was available for 23 patients. At a mean follow-up time of 12.2 months ± 10.1, 19 of 20 (95%) patients treated for pain and 2 of 3 (67%) patients treated for swelling/mass effect reported partial or complete symptomatic relief. There was a significant decrease in the postablation pain scores (-5.7 ± 1.0, P < .001) and maximum VA size (-2.3 cm ± 2.7, P = .004), with >50% reduction in VA T2 signal (59%) and enhancement (73%). Nine of 30 (30%) patients experienced minor complications. CONCLUSIONS: MR imaging-guided and monitored percutaneous laser ablation and cryoablation appear to be safe and effective for the treatment of symptomatic peripheral soft tissue VAs.

High-resolution MRI of a peroneal intraneural ganglion cyst arising from the knee joint: illustrative case.

BACKGROUND: The advancement of high-resolution imaging and increased clinical experience have led to an increased understanding of the formation and treatment of intraneural ganglion cysts. Nearly all intraneural ganglion cysts in the common peroneal nerve have been reported to arise from a joint connection to the superior tibiofibular joint. The authors have identified four cases of intraneural ganglion cysts arising from the knee joint itself; however, none of these reported cases were well described, documented, or illustrated with high-resolution imaging. OBSERVATIONS: Here the authors present the case of an intraneural ganglion cyst arising from the knee joint and causing intermittent weakness and pain. The articular branch to the knee joint was clearly demonstrated on high-resolution magnetic resonance imaging and confirmed at surgical exploration. The patient was treated with articular branch ligation and has had complete resolution of his symptoms without recurrence of the cyst on follow-up imaging. LESSONS: This case adds to the mounting evidence that intraneural cyst pathology is dependent on a connection to a synovial joint as stated in the unifying theory of intraneural cyst development.

Preoperative sonographic ulnar nerve mapping in the postoperative elbow.

OBJECTIVE: To describe the technique of sonographic ulnar nerve mapping in the postoperative elbow for surgical planning. MATERIALS AND METHODS: A retrospective review of a surgical databank identified 24 patients, all aged 18 years and older with a history of orthopedic elbow surgery, who were referred for preoperative sonographic mapping of the ulnar nerve prior to subsequent surgery. All cases were reviewed for patient demographics, clinical presentation, prior surgical interventions, and ultrasound technique. Charts were reviewed for intraoperative and postoperative outcomes, including nerve injury. RESULTS: The cohort included 12 males and 12 females with a mean age of 51 years (range 22-68 years) and a mean BMI of 29 (range 20-48). Preoperative sonographic ulnar nerve mapping occurred following various elbow surgeries including ulnar nerve transposition to assess nerve location prior to subsequent elbow surgery. Of the 24 patients with preoperative sonographic ulnar nerve mapping, subsequent surgery was performed arthroscopically in 14 and open in 10 cases. In 11 of the 24 cases, there was specific mention of a modified approach to joint access which was guided by the ulnar nerve map. There were no perioperative ulnar nerve-related complications, such as nerve transection. CONCLUSION: Preoperative mapping can facilitate planning of surgical access and ulnar nerve dissection. Sonographic mapping of the ulnar nerve reduces the potential uncertainty of nerve palpation in a complex postoperative elbow following ulnar nerve transposition. This technique may mitigate the risk of ulnar nerve injury.

Intraosseous "Lipoma" of the Calcaneus Developing in an Intraosseous Ganglion Cyst.

Intraosseous lipomas are rare primary bone tumors, most common to the calcaneus. There are several proposed theories of the natural etiology of intraosseous lipomas; however, all lack definitive support. In this report, an 18-year-old man presented with radiologic evidence of a simple bone cyst of the calcaneus. Over a 4-year period, the patient was followed with interval magnetic resonance imaging. The cyst demonstrated progressive development of peripheral intralesional fat with final magnetic resonance imaging features characteristic of an intraosseous lipoma. To our knowledge, this is the first longitudinal study that shows gradual peripheral fat deposition within an intraosseous ganglion cyst, illustrating a potential cause of intraosseous lipomas of the calcaneus.