High-field and low-field MR imaging of superior glenoid labral tears and associated tendon injuries

Modern Low-Field MRI of the Musculoskeletal System: Practice Considerations, Opportunities, and Challenges

ABSTRACT

Magnetic resonance imaging (MRI) provides essential information for diagnosing and treating musculoskeletal disorders. Although most musculoskeletal MRI examinations are performed at 1.5 and 3.0 T, modern low-field MRI systems offer new opportunities for affordable MRI worldwide. In 2021, a 0.55 T modern low-field, whole-body MRI system with an 80-cm-wide bore was introduced for clinical use in the United States and Europe. Compared with current higher-field-strength MRI systems, the 0.55 T MRI system has a lower total ownership cost, including purchase price, installation, and maintenance. Although signal-to-noise ratios scale with field strength, modern signal transmission and receiver chains improve signal yield compared with older low-field magnetic resonance scanner generations. Advanced radiofrequency coils permit short echo spacing and overall compacter echo trains than previously possible. Deep learning-based advanced image reconstruction algorithms provide substantial improvements in perceived signal-to-noise ratios, contrast, and spatial resolution. Musculoskeletal tissue contrast evolutions behave differently at 0.55 T, which requires careful consideration when designing pulse sequences. Similar to other field strengths, parallel imaging and simultaneous multislice acquisition techniques are vital for efficient musculoskeletal MRI acquisitions. Pliable receiver coils with a more cost-effective design offer a path to more affordable surface coils and improve image quality. Whereas fat suppression is inherently more challenging at lower field strengths, chemical shift selective fat suppression is reliable and homogeneous with modern low-field MRI technology. Dixon-based gradient echo pulse sequences provide efficient and reliable multicontrast options, including postcontrast MRI. Metal artifact reduction MRI benefits substantially from the lower field strength, including slice encoding for metal artifact correction for effective metal artifact reduction of high-susceptibility metallic implants. Wide-bore scanner designs offer exciting opportunities for interventional MRI. This review provides an overview of the economical aspects, signal and image quality considerations, technological components and coils, musculoskeletal tissue relaxation times, and image contrast of modern low-field MRI and discusses the mainstream and new applications, challenges, and opportunities of musculoskeletal MRI.

Clinical Assessment of Physical Examination Maneuvers for Superior Labral Anterior to Posterior Lesions

Purpose  Shoulder pain and disability pose a diagnostic challenge owing to the numerous etiologies and the potential for multiple disorders to exist simultaneously. The evidence to support the use of clinical tests for superior labral anterior to posterior complex (SLAP) is weak or absent. The purpose of this study is to determine the diagnostic validity of physical examination maneuvers for SLAP lesions by performing a methodologically rigorous, clinically applicable study.

Methods  We recruited consecutive new shoulder patients reporting pain and/or disability. The physician took a history and indicated their certainty about each possible diagnosis (“certain the diagnosis is absent/present,” or “uncertain requires further testing”). The clinician performed the physical tests for diagnoses where uncertainty remained. Magnetic resonance imaging arthrogram and arthroscopic examination were the gold standards. We calculated sensitivity, specificity, and likelihood ratios (LRs) and investigated whether combinations of the top tests provided stronger predictions.

Results  Ninety-three patients underwent physical examination for SLAP lesions. When using the presence of a SLAP lesion (Types I–V) as disease positive, none of the tests was sensitive (10.3–33.3) although they were moderately specific (61.3–92.6). When disease positive was defined as repaired SLAP lesion (including biceps tenodesis or tenotomy), the sensitivity (10.5–38.7) and specificity (70.6–93.8) of tests improved although not by a substantial amount. None of the tests was found to be clinically useful for predicting repairable SLAP lesions with all LRs close to one. The compression rotation test had the best LR for both definitions of disease (SLAP tear present = 1.8 and SLAP repaired = 1.67). There was no optimal combination of tests for diagnosing repairable SLAP lesions, with at least two tests positive providing the best combination of measurement properties (sensitivity 46.1% and specificity 64.7%).

Conclusion  Our study demonstrates that the physical examination tests for SLAP lesions are poor diagnostic indicators of disease. Performing a combination of tests will likely help, although the magnitude of the improvement is minimal. These authors caution clinicians placing confidence in the physical examination tests for SLAP lesions rather we suggest that clinicians rely on diagnostic imaging to confirm this diagnosis.

Diagnostic Validity of Patient-Reported History for Shoulder Pathology

Objective  The purpose of this article is to determine whether patient-reported history items are predictive of shoulder pathology and have the potential for use in triaging patients with shoulder pathology to orthopaedic outpatient clinics. Setting  It is set at two tertiary orthopaedic clinics. Patients  All new patients reporting pain and/or disability of the shoulder joint were prospectively recruited. A total of 193 patients were enrolled, 15 of whom withdrew, leaving 178 patients composing the study sample. Design  Patients completed a questionnaire on the history of their pathology, then the surgeon took a thorough history indicating the most likely diagnosis. The clinician then performed appropriate physical examination. Arthroscopy was the reference standard for those undergoing surgery and magnetic resonance imaging (MRI) with arthrogram for all others. We calculated the sensitivity, specificity, and likelihood ratios (LRs) of history items alone and in combination. We used the LRs to generate a clinical decision algorithm. Main Outcome Measures  Diagnosis was determined through arthroscopy or MRI arthrogram. Reporting was standardized to ensure review of all structures. Results  The physical examination and history agreed in 75% of cases. Of those that did not agree, the physical examination misdirected the diagnosis in 47% of our cases. In particular, history items were strong predictors of anterior and posterior instability and subscapularis tears and were combined in a tool to be utilized for screening patients. Conclusion  The patient-reported history items were effective for diagnosing shoulder pathology and should be considered for use in a triaging instrument.

Diagnosis of Superior Labrum Anterior-to-Posterior Tears by Using MR Imaging and MR Arthrography: A Systematic Review and Meta-Analysis

Purpose To evaluate the diagnostic accuracies of nonenhanced magnetic resonance (MR) imaging and MR arthrography for diagnosis of superior labrum anterior-to-posterior (SLAP) tears by using a systematic review and meta-analysis. Materials and Methods A comprehensive literature search was performed on the two main concepts of MR imaging (MR imaging, and direct and indirect MR arthrography) and SLAP tears. Inclusion criteria consisted of original studies that assessed the diagnostic accuracy of MR imaging, direct MR arthrography, and/or indirect MR arthrography for the detection of SLAP tears, by using surgical findings as the reference standard. The Quality Assessment of Diagnostic Accuracy Studies 2, or QUADAS-2 Quality Assessment of Diagnostic Accuracy Studies 2 Quality Assessment of Diagnostic Accuracy Studies 2 , tool was used to assess methodologic quality. Meta-analyses were performed that compared MR imaging studies to direct MR arthrography studies and indirect MR arthrography studies, 3-T studies to 1.5-T studies, and low-bias MR imaging studies to low-bias direct MR arthrography studies. Study variation was analyzed by using the Cochran Q test of heterogeneity and the I² statistic. Results Thirty-two studies met inclusion and exclusion criteria, including 3524 imaging examinations: 1963 direct MR arthrography examinations (23 studies), 1402 MR examinations (14 studies), and 159 indirect MR arthrography examinations (three studies). Twelve studies had low risk for bias, two had questionable risk, and 18 had high risk. Mean sensitivities of direct MR arthrography, MR imaging, and indirect MR arthrography for SLAP tear diagnosis were 80.4%, 63.0%, and 74.2%, respectively. Mean specificities of direct MR arthrography, MR imaging, and indirect MR arthrography were 90.7%, 87.2%, and 66.5%, respectively. Summary receiver operator characteristic (ROC) curve demonstrated superior accuracy of direct MR arthrography compared with those of MR imaging and indirect MR arthrography. Similar findings were observed in the low-bias subanalysis. Summary ROC curve demonstrated overall superiority of 3-T imaging, with or without intra-articular contrast material compared with 1.5-T imaging, with or without intra-articular contrast material. Significant variance was observed for MR imaging and direct MR arthrography (P < .001) studies for both mean sensitivity and specificity. Conclusion Direct MR arthrography appears to be more accurate than nonenhanced MR imaging for diagnosis of SLAP tears, whereas 3-T MR imaging with or without intra-articular contrast material appears to improve diagnostic accuracy compared with 1.5-T MR imaging with or without intra-articular contrast material. ^© RSNA, 2017 Online supplemental material is available for this article.

Magnetic Resonance Imaging Currently Fails to Fully Evaluate the Biceps-Labrum Complex and Bicipital Tunnel

PURPOSE

To determine the diagnostic accuracy of magnetic resonance imaging (MRI) for biceps-labrum complex (BLC) lesions, including the extra-articular bicipital tunnel.

METHODS

A retrospective review of 277 shoulders with chronic refractory BLC symptoms that underwent arthroscopic subdeltoid transfer of the long head of the biceps tendon (LHBT) to the conjoint tendon was conducted. Intraoperative lesions were categorized as "inside" (labral tears and dynamic LHBT incarceration), "junctional" (LHBT partial tears, LHBT subluxation, and biceps chondromalacia), or "bicipital tunnel" (extra-articular bicipital tunnel scar/stenosis, loose bodies, LHBT instability, and LHBT partial tears) based on anatomic location. Attending radiologist-generated MRI reports were graded dichotomously as positive or negative for biceps and labral damage and then compared with intraoperative findings. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for MRI with respect to intraoperative findings.

RESULTS

With regard to inside lesions, MRI had an overall sensitivity, specificity, PPV, and NPV for labrum lesions of 77.3%, 68.2%, 57.3%, and 84.5% respectively. The sensitivity, specificity, PPV, and NPV of MRI for junctional lesions were 43.3%, 55.6%, 73.1%, and 26.0%, respectively. For the bicipital tunnel, MRI had a sensitivity, specificity, PPV, and NPV of 50.4%, 61.4%, 48.7%, and 63.0%, respectively.

CONCLUSIONS

MRI was unreliable for ruling out BLC lesions among chronically symptomatic patients, including when the bicipital tunnel was affected.

A Comparison of Biceps Labrum Complex Findings in Patients with and without Superior Migration of the Humeral Head in Large or Massive Rotator Cuff Tears

Background

The purpose of this study was to clarify the relationship between superior migration of the humeral head and findings of biceps labrum complex (BLC) in large or massive rotator cuff tears.

Methods

Forty-nine shoulders that underwent surgery for torn supraspinatus and infraspinatus tendons were included. Patients were divided into two groups according to the acromio—humeral interval (AHI). Arthroscopic findings of BLC were classified into five types; Type 0; normal shape, Type 1: fraying; Type 2: detachment; Type 3: attrition of BLC and superior glenoid; and Type 4: defect.

Results

The group without migration (AHI ≥ 7 mm) consisted of 21 shoulders and that with migration (AHI < 7 mm) was 28 shoulders. There were significantly more patients with Types 2, 3, and 4 in the group with migration than without migration.

Conclusion

This study indicates a potential relationship between BLC injury and superior humeral head migration accompanied by a rotator cuff tear.

Analysis of Low-Field MRI Scanners for Evaluation of Shoulder Pathology Based on Arthroscopy

BACKGROUND

Many studies have compared the diagnostic capabilities of low-field magnetic resonance imaging (MRI) scanners to high-field MRI scanners; however, few have evaluated the low-field MRI diagnoses compared with intraoperative findings.

PURPOSE

To determine the accuracy and sensitivity of low-field MRI scanners in diagnosing lesions of the rotator cuff and glenoid labrum.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

Over a 2-year period, MRI examinations without intra-articular contrast were performed on 79 patients for shoulder pathologies using an in-office 0.2-T extremity scanner. The MRI examinations were read by board-certified, musculoskeletal fellowship-trained radiologists. All patients underwent shoulder arthroscopy performed by a single sports fellowship-trained orthopaedic surgeon within a mean time of 56 days (range, 8-188 days) after the MRI examination. The mean patient age was 54 years (range, 18-81 years). Operative notes from the shoulder arthroscopies were then retrospectively reviewed by a single blinded observer, and the intraoperative findings were compared with the MRI reports.

RESULTS

For partial-thickness rotator cuff tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 85%, 89%, 79%, and 92%, respectively. For full-thickness rotator cuff tears, the respective values were 97%, 100%, 100%, and 98%. For anterior labral lesions, the values were 86%, 99%, 86%, and 99%, and for superior labral anterior-posterior (SLAP) lesions, the values were 20%, 100%, 100%, and 79%, respectively.

CONCLUSION

Low-field MRI is an accurate tool for evaluation of partial- and full-thickness rotator cuff tears; however, it is not effective in diagnosing SLAP lesions. More information is needed to properly assess its ability to diagnose anterior and posterior labral lesions.

Disorders of the proximal and distal aspects of the biceps muscle

PROXIMAL ASPECT OF BICEPS: Tenodesis of the long head of the biceps may offer improved cosmesis, improved strength, and diminished activity-related pain compared with tenotomy, although comparative studies have shown similar outcomes in some patient populations. DISTAL ASPECT OF BICEPS: Operative treatment of both partial and complete distal biceps ruptures results in better outcomes compared with nonoperative care, although the optimal technique and fixation are yet to be determined. Nonoperative management is an acceptable treatment for patients willing to accept some loss of forearm supination and elbow flexion strength as well as changes in endurance and cosmesis.

Imaging of football injuries to the upper extremity

Imaging of football players is unique in many ways. Familiarity with mechanisms of injury, position of the player, and the need for rapid diagnosis and reporting will help radiologists when dealing with these athletes. Although plain radiographs are typically the first imaging modality used, MR imaging has become the cornerstone on which diagnoses and treatment decisions are based. As these athletes become stronger, faster, and more skilled, the ability to accurately assess their injuries becomes even more important, and understanding of the challenges that these patients present becomes critical.

Protocol for determining the diagnostic validity of physical examination maneuvers for shoulder pathology

BACKGROUND

Shoulder complaints are the third most common musculoskeletal problem in the general population. There are an abundance of physical examination maneuvers for diagnosing shoulder pathology. The validity of these maneuvers has not been adequately addressed. We propose a large Phase III study to investigate the accuracy of these tests in an orthopaedic setting.

METHODS

We will recruit consecutive new shoulder patients who are referred to two tertiary orthopaedic clinics. We will select which physical examination tests to include using a modified Delphi process. The physician will take a thorough history from the patient and indicate their certainty about each possible diagnosis (certain the diagnosis is absent, present or requires further testing). The clinician will only perform the physical examination maneuvers for diagnoses where uncertainty remains. We will consider arthroscopy the reference standard for patients who undergo surgery within 8 months of physical examination and magnetic resonance imaging with arthrogram for patients who do not. We will calculate the sensitivity, specificity and positive and negative likelihood ratios and investigate whether combinations of the top tests provide stronger predictions of the presence or absence of disease.

DISCUSSION

There are several considerations when performing a diagnostic study to ensure that the results are applicable in a clinical setting. These include, 1) including a representative sample, 2) selecting an appropriate reference standard, 3) avoiding verification bias, 4) blinding the interpreters of the physical examination tests to the interpretation of the gold standard and, 5) blinding the interpreters of the gold standard to the interpretation of the physical examination tests. The results of this study will inform clinicians of which tests, or combination of tests, successfully reduce diagnostic uncertainty, which tests are misleading and how physical examination may affect the magnitude of the confidence the clinician feels about their diagnosis. The results of this study may reduce the number of costly and invasive imaging studies (MRI, CT or arthrography) that are requisitioned when uncertainty about diagnosis remains following history and physical exam. We also hope to reduce the variability between specialists in which maneuvers are used during physical examination and how they are used, all of which will assist in improving consistency of care between centres.

Validity of noncontrast magnetic resonance imaging in diagnosing superior labrum anterior-posterior tears

BACKGROUND

The biceps labral complex has received much interest in recent years as a source of shoulder pain. Magnetic resonance imaging (MRI) is the imaging modality of choice for those patients with a suspected superior labrum anterior-posterior (SLAP) tear. The goal of this study was to look at the accuracy of MRI without arthrography to correctly identify SLAP tears.

METHODS

The study had a prospective, case-based, case-control design. Participants were consecutive patients seen at an orthopaedic outpatient clinic who received an MRI scan as part of their diagnostic cycle. All patients were aged at least 18 years, with various shoulder dysfunctions (impingement, rotator cuff tear, and so on) that were evaluated during a routine clinical evaluation. Arthroscopic surgery was performed as the reference standard for a SLAP lesion.

RESULTS

Seventy-seven patients were evaluated during arthroscopic surgery. The pretest probability of a SLAP lesion-only diagnosis was 18.2%, and for a SLAP lesion with or without a concomitant diagnosis, the pretest probability was 66.2%. In both cases, use of MRI led to post-test probability values that were worse when a positive finding was identified on the MRI scan.

DISCUSSION

The results of this study suggest that SLAP tears are often incorrectly diagnosed based on MRI evaluation, with MRI providing a high level of sensitivity and low level of specificity. On the basis of the results of this study, conventional MRI is not a suitable test to accurately evaluate the biceps labral complex for the presence of a SLAP tear.

Throwing injuries of the upper extremity

The overhead throwing motion is a complex sequence of maneuvers that requires coordinated muscle activity in the upper and lower extremities. The shoulder and elbow are subject to multidirectional forces and are particularly vulnerable to injury during specific phases of the overhead throwing motion. Ligamentous, tendinous, neural, and osseous pathology that may occur in the shoulder or elbow of an overhead-throwing athlete will be discussed, with an emphasis on the role of MR imaging and MR arthrography.

Shoulder MRI accuracy in the community setting

HYPOTHESIS/BACKGROUND

Evaluate the accuracy for shoulder magnetic resonance imaging (MRI) interpretations of typical community radiologists and compare this to selected fellowship trained musculoskeletal radiologists.

METHODS

The MRIs of 104 shoulders of 100 consecutive different patients who had undergone shoulder arthroscopy by a single surgeon were included in this prospective study. The 104 typed MRI reports of community radiologists were examined, and the positive or negative findings were recorded for the anterior, superior, and posterior labra, and the long head biceps tendon and rotator cuff. The 104 MRIs were then interpreted by 2 fellowship trained musculoskeletal radiologists who were blinded to the nature of this study. They were asked to specifically comment on the same shoulder pathologies and to subjectively rate the quality of each MRI study using a visual analogue score (VAS).

RESULTS

The shoulder pathologies documented by arthroscopy included rotator cuff tears (55 full, 10 partial), labral tears (12 anterior, 17 posterior, 29 superior), and 31 biceps abnormalities. There were 69 noncontrast MRIs and 35 MRI arthrograms. Comparing the community radiologists' accuracies with the 2 selected musculoskeletal radiologists' accuracies, there were no significant differences for any of the shoulder pathologies studied. There was a significant positive correlation between VAS and accuracies for both musculoskeletal radiologists in diagnosing posterior labral tears only. The use of contrast in these MRIs only significantly improved both of the musculoskeletal radiologists' accuracies in diagnosing biceps lesions.

CONCLUSION

The accuracies for shoulder MRI in this community setting were not improved by having the MRIs interpreted by selected fellowship trained musculoskeletal radiologists.

Comparison of high-field and low-field magnetic resonance images of cadaver limbs of horses

Eleven limbs taken postmortem from 10 lame horses were examined by MRI in a low-field 0.27T system designed for standing horses and a high-field 1.5T system used to examine anaesthetised horses. Nine limbs were examined in the foot/pastern region and two in the fetlock region, and the results were compared with gross pathological examinations and histological examinations of selected tissues. The appearance of normal tissues was similar between the two systems, but the anatomical arrangement of the structures was different due to differences in positioning, and a magic angle artefact was observed at different sites in some imaging sequences. Articular cartilage could be differentiated into two articular surfaces in most joints in the high-field images but could generally be separated only at the joint margins in the low-field images. Abnormalities of tendon, ligament and bone detected by gross examination were detected by both forms of MRI, but some details were clearer on the high-field images. Articular cartilage found to be normal on pathological examination was also classified as normal on MRI, but lesions in articular cartilage detected on pathological examination were identified only by high-field MRI. An abnormality was detected on MRI of all the limbs that had abnormal navicular flexor fibrocartilage on pathological examination.

Glenohumeral instability associated with Buford complex

Buford complex is described as a normal anatomical variant of the anterosuperior part of the glenoid consisting of the absence of the anterosuperior labrum with the presence of a cord-like middle glenohumeral ligament. Traditionally, reattachment to the glenoid has been discouraged. We present a case of a Buford complex associated with glenohumeral instability. The patient was operated for recurrent instability without a preoperative diagnosis of Buford complex. The diagnosis was made during shoulder arthroscopy and reattachment to the glenoid was performed with a satisfactory outcome. Here, we discuss the relationship of the Buford complex with intraarticular pathology and the surgical treatment in cases when this variant is associated with instability.

Superior labral tears of the shoulder: pathogenesis, evaluation, and treatment

Lesions of the superior glenoid labrum and biceps anchor are a well-recognized cause of shoulder pain. Advances in shoulder arthroscopy have led to improvements in recognizing and managing superior labral anterior-posterior (SLAP) tears. Recent biomechanical studies have postulated several theories for the pathogenesis of SLAP tears in throwing athletes and the effect of these injuries on normal shoulder kinematics. Advances in soft-tissue imaging techniques have resulted in improved accuracy in diagnosing SLAP tears. However, the diagnosis of clinically relevant SLAP tears remains challenging because of the lack of specific examination findings and the frequency of concomitant shoulder injuries. Definitive diagnosis of suspected SLAP tears is confirmed on arthroscopic examination. Advances in surgical techniques have made it possible to achieve secure repair in selected patterns of injury. Recent outcomes studies have shown predictably good functional results and an acceptable rate of return to sport and/or work with arthroscopic treatment of SLAP tears.

[Rotator cuff tears: value of 3.0T MRI]

PURPOSE

To demonstrate the value of 3.0T MR imaging for the detection of rotator cuff tendon tears and surgical planning by correlating imaging findings to surgical findings. Materials and methods. Prospective follow-up of patients who underwent 3.0T MR imaging of the shoulder in our department between November 2005 and June 2007. Surgical findings were correlated to imaging findings for 48 patients who underwent surgery: detection, size, partial thickness or complete, and tendon edges.

RESULTS

In this patient group, the positive predictive value of MRI for detecting surgical tears was 100% (100% of complete tears and 92% of partial thickness tears). No change in surgical management was recorded when arthroscopy was performed based on MRI findings (size of tear).

CONCLUSION

3.0 T MRI is valuable for the detection of small tears, especially for partial thickness tears due to increased spatial resolution. The identification of surgical candidates and surgical planning are improved due to more accurate measurements of tear size and quality of the tendon edges.

Analysis of interobserver and intraobserver variability in the diagnosis and treatment of SLAP tears using the Snyder classification

BACKGROUND

Superior labral anterior posterior lesions are a relatively rare entity, and classification as a basis for selection of treatment has remained a point of controversy.

HYPOTHESIS

There will be substantial interobserver and intraobserver variability in the diagnosis and treatment of superior labral anterior posterior tears by experienced arthroscopic specialists.

STUDY DESIGN

Cohort study (diagnosis), Level of evidence, 2.

METHODS

Compact discs containing 22 video vignettes of approximately 15 seconds duration were sent to the membership of the Arthroscopy Association of North America, American Shoulder and Elbow Society, and AOSSM. Each surgeon was asked to review the vignettes, classify the superior labral anterior posterior lesion type, and provide a treatment recommendation for each vignette. Seventy-three expert surgeons responded to the solicitation with a completed analysis. The same CD-ROM was re-sent to each of these 73 surgeons at a minimum of 12 months after the first viewing to obtain data on intraobserver reliability. Seventeen of the 73 surgeons returned this second CD-ROM with a complete analysis. Demographic data were also obtained from each surgeon. Multivariable logistic regression analysis was used to analyze the data, and 95% confidence intervals were established for each superior labral anterior posterior type (I-IV) with regard to diagnosis and treatment decision.

RESULTS

The 22 vignettes analyzed by 73 surgeons resulted in 1606 responses. Several significant trends were noticed with regard to diagnosis and treatment from the responses: (1) surgeons had difficulty distinguishing type III lesions from type IV lesions, (2) the treatment of type III lesions is much more variable than that of any other subtype, and (3) surgeons had difficulty distinguishing normal shoulders from type II superior labral anterior posterior tears. No relationship was identified between correct treatment decisions based on diagnosis and any of the demographic factors analyzed. Our analysis of intraobserver variability showed only moderate agreement. The analysis of interobserver variability improved significantly when the diagnoses were analyzed based on treatment decision.

CONCLUSIONS

There is substantial interobserver and intraobserver variability among experienced shoulder arthroscopic specialists with regard to diagnosis and treatment of superior labral anterior posterior tears. Intraobserver agreement using the Snyder classification indicated only moderate agreement. Analysis of interobserver agreement based on treatment decisions results in superior concordance among experienced surgeons for the diagnosis of superior labral anterior posterior lesions.

Isolated and combined Type II SLAP repairs in a military population

The study compares the clinical results of isolated arthroscopic repair of Type II SLAP tears with those of combined treatment for Type II SLAP and other associated shoulder conditions. The population was composed of 36 aged-matched active duty males with a mean age of 31.6 years (range 22-41 years); mean follow-up was 29.1 months (range 24-42 months). Eighteen subjects in Group I had isolated Type II SLAP tears. Eighteen subjects in Group II had Type II SLAP tear and concomitant ipsilateral shoulder conditions, including subacromial impingement in six patients, acromioclavicular arthrosis in three patients, subacromial impingement and acromioclavicular arthrosis in four patients, spinoglenoid cyst in four patients, and intra-articular loose bodies in one patient. Arthroscopic SLAP repair was performed with biodegradable suture anchors. Subacromial decompression and spinoglenoid cyst decompression were performed arthroscopically. Distal claviculectomy was performed in open fashion. Loose bodies were removed arthroscopically. At minimum 2-year follow-up, the mean UCLA score for Group I (30.2 +/- 3.0 points) was not significantly different from Group II (30.8 +/- 2.0 points) (P = 0.48). The mean post-operative ASES score for Group I (84.1 +/- 13.4 points) was significantly lower than for Group II (91.8 +/- 5.4 points) (P < 0.04). The mean VAS pain score for Group I (1.6 +/- 1.3 points) was significantly higher than for Group II (0.7 +/- 0.7 points) (P < 0.02). Seventeen of 18 patients (94%) in each group returned to full duty. In a population of active duty males, arthroscopic repair of isolated Type II SLAP had comparable results with a cohort of Type II SLAP repairs treated in combination with other shoulder conditions, with the combined treatment group having significantly better results in two of three parameters measured. Return to duty rates were identical. Therefore, concurrent treatment of other associated extra-articular shoulder conditions improves the overall success of SLAP repair and the presence of these other conditions should be recognized and treated along with the SLAP tears in order to maximize clinical results.

Arthroscopic superior labrum anterior-posterior repair in military patients

The purpose of this retrospective study was to determine the efficacy of arthroscopic superior labrum anterior-posterior (SLAP) repair in a military population. In this study, 27 patients (of 30 consecutive patients) who had suture anchor repair of a type II SLAP lesion were evaluated at a mean of 30.5 months postoperatively. Fifteen patients had isolated tears, whereas twelve also had a concomitant diagnosis. At follow-up, the overall mean American Shoulder and Elbow Surgeons score was 86.9 points and the mean University of California, Los Angeles score was 30.4 points. The results were excellent in 4 patients, good in 20, and fair in 3. Of the patients, 96% returned to full duty (mean, 4.4 months). Patients treated for concomitant diagnoses and a SLAP tear had significantly higher American Shoulder and Elbow Surgeons scores and tended to have higher University of California, Los Angeles scores than those treated for an isolated SLAP tear. The findings indicate that arthroscopic SLAP repair in military patients results in a high rate of return to duty. The results suggest that concomitant shoulder pathology should be treated at the time of SLAP repair.

Shoulder MR arthrography: In vitro determination of optimal gadolinium dilution as a function of field strength

PURPOSE

To find the optimal contrast agent dilution to maximize signal intensity (SI), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in shoulder MR arthrography using MR systems operating at different magnetic field strengths.

MATERIALS AND METHODS

Autoptic human glenohumeral ligaments were inserted in eight egg-shaped 20-mL phantoms filled with saline and gadolinium diethylenetriaminepentaacetic acid bismethylamide (Gd-DTPA-BMA) in different dilutions of 0.5, 1, 2, 2.5, 5, 12.5, 50 mmol/liter, to simulate the shoulder articular capsule. These phantoms were inserted inside two plastic 240-mL phantoms filled with water. MRI was performed on 0.2-, 0.5-, 1.0-, 1.5-, and 3.0-T MR systems using a three-dimensional gradient echo (GRE)-T1-weighted pulse sequence. SI, SNR, and CNR were determined.

RESULTS

Peak SI and SNR were found at 5 mmol/liter, with the exception of the 0.2-T scanner, where the maximum was at 2 mmol/liter. Peak CNR was observed at 1 mmol/liter for the 3-T scanner, at 2 mmol/liter for the 0.2- and 0.5-T scanners, and at 5 mmol/liter for the remaining scanners.

CONCLUSION

The optimal SI and SNR are provided by 5 mmol/liter contrast agent dilution. Peak CNR was found in a range between 1 and 5 mmol/liter dilutions, depending on the strength of the magnetic field.

Low-field musculoskeletal MRI

Since it was first introduced in the field of medical imaging in the early 1980s, MRI has become essential for the diagnosis and treatment of musculoskeletal conditions. Most imaging in the United States is performed on high-field (>1.0T), whole-body scanners. However, for reasons discussed below, imaging at low (<0.5T) and medium (0.5-1.0T) field strengths using small, low-cost, easily installed scanners in imaging centers and physicians' offices is gaining increasing popularity. Such scanners can be very useful for imaging the upper and lower extremities, from the shoulder to the fingers and the hips to the toes. In this review we provide an overview of the different available extremity scanners and their advantages and disadvantages, briefly review the literature regarding their use, and discuss our experience in using low-field extremity scanners to evaluate joints.

Magnetic resonance imaging accuracy for the diagnosis of superior labrum anterior-posterior lesions in the community setting: eighty-three arthroscopically confirmed cases

Magnetic resonance imaging (MRI) has been shown in the literature to have high accuracy for the diagnosis of superior labrum anterior-to-posterior (SLAP) lesions. However, these studies have been performed at specialized institutions and have not been evaluated for community settings. Our hypothesis was that MRI diagnosis of SLAP lesions in the community setting is not as accurate as suggested by previous literature. The MRI reports for 83 consecutive surgically confirmed type II SLAP lesions were evaluated. The findings regarding the presence of SLAP lesions were documented from the community radiologists' MRI readings. Two blinded, fellowship-trained musculoskeletal radiologists evaluated these same 83 MRIs, as well as 17 MRIs with surgically confirmed normal superior labra. The musculoskeletal radiologists also used a visual analog scale to subjectively grade the quality of each MRI. MRIs were performed at 14 different centers and were read by 28 different community radiologists. There were 37 noncontrast MRIs and 46 MRI arthrograms. The community radiologists accurately identified 51% of the SLAP lesions. The sensitivities for the community radiologists were significantly better for the MRI arthrograms than for the noncontrast MRIs (P = .0002). For the two musculoskeletal radiologists, the sensitivities were 60% and 67.5%, and the specificities were 71% and 76.5%. The accuracies for the musculoskeletal radiologists were 62% and 69%. One of the musculoskeletal radiologists had significant correlation between the visual analog score and MRI diagnostic accuracy (P = .0006). The sensitivity for one of the musculoskeletal radiologists was significantly greater than the sensitivity for the community radiologists (P = .0063). The accuracies between the other musculoskeletal radiologist and the community radiologists were not significantly different (P = .0577). In this community setting, MRI was not accurate for the diagnosis of SLAP lesions. Musculoskeletal radiologists were more accurate than the community radiologists; however, the musculoskeletal radiologists were not as accurate as previous literature might predict.

MR Imaging of the Glenohumeral Ligaments

The glenohumeral ligaments, particularly the inferior one, are the major passive stabilizers of the joint, and the labrum functions as a site of ligamentous attachment. The strong union between the collagen fibers of the glenohumeral ligaments and the glenoid labrum is more resistant to injury than the union between the glenoid rim and the labrum. Labral tears associated with glenohumeral instability are therefore usually secondary to avulsion rather than impaction. This article reviews the normal MR imaging anatomy, variants and pitfalls of the glenohumeral ligaments, and the basic biomechanics of the glenohumeral ligaments. Examples of injuries involving these structures are provided.

Low field MRI: a review of the literature and our experience in upper extremity imaging

Since its introduction to medical imaging in the early 1980s, MRI has become essential in diagnosis and treatment of musculoskeletal conditions. Most imaging in the United States is performed on high-field whole-body scanners (>1.0 T). Imaging on low (<0.5 T) and medium (0.5-1.0 T) field strengths using small, low-cost, easily installed scanners in physicians' offices or imaging centers has gained popularity. These scanners can be useful in imaging the upper extremity from the shoulder to the fingers. This article provides an overview of the different extremity scanners available and their advantages and disadvantages, a brief review of the literature regarding their use, and a discussion of our experience in using the low-field extremity scanners in evaluating the upper extremity.

3T MR Imaging of the Musculoskeletal System (Part II): Clinical Applications

The gain in SNR that is afforded by 3T MR imaging systems has tremendous clinical applications in the musculoskeletal system. The potential for demonstrating and enhancing the visibility of normal osseous, tendinous, cartilaginous, and ligamentous structures is exciting. Furthermore, harnessing this added signal to increase spatial resolution may improve our diagnostic abilities in various joints dramatically. Radiologists have enjoyed great success in assessing joint disease with current MR imaging field strengths; however, many intrinsic joint structures remain poorly evaluated, which leads to a golden opportunity for 3T MR imaging. The articular cartilage of the knee, the glenoid labrum of the shoulder, the intrinsic ligaments and TFC of the wrist, the collateral ligaments of the elbow, the labrum and articular cartilage of the hip, and the collateral ligaments of the ankle have been evaluated suboptimally on 1 .5T systems using routine nonarthrographic MR images. Because of the enhanced SNR, the higher spatial resolution, and the greater CNR of intrinsic joint structures at higher field strengths, 3T MR imaging has the potential to improve diagnostic abilities in the musculoskeletal system vastly, which translates into better patient care and management. The author's 2 years of clinical experience with musculoskeletal MR imaging on 3T systems has met and exceeded his expectations, and has bolstered the confidence of his orthopedic surgeons in his diagnoses. As coil technology advances and as the use of parallel imaging becomes more available in the extremities, the author expects to see even more dramatic improvements in image quality.

Musculoskeletal Imaging at 3T: Current Techniques and Future Applications

MSK MR imaging applications are making the transition rapidly from 1.5T to 3T. Initial experience in the knee suggests that the higher SNR provides technical improvement in routine clinical imaging with the potential for greater accuracy in the diagnosis of articular cartilage injury. Similarly, initial experience with 3T MR imaging in the evaluation of the hip and small joints of the hand and wrist has been positive. In other joints, clinical development has been limited by the lack of availability of dedicated surface coils, and sensitivity of 3TMR imaging to artifact. The clinical impact of this technology remains uncertain because no published controlled clinical trial has evaluated the impact of 3T MR imaging on diagnostic outcomes. In addition to clinical application, 3T MR imaging has an important role for furthering translational research in MSK diseases through the development of new molecular and functional MR imaging techniques.

High- Versus Low-Field MR Imaging

The role of MR imaging as a noninvasive technique in the detection and evaluation of musculoskeletal diseases is unquestionable. Most of the studies reported in the literature are based on high-field MR imaging. Initial studies performed with low-field-strength have reported unsatisfactory results in the assessment of the musculoskeletal system. Recent improvements, however, have generated a renewed interest in low-field-strength MR imaging. This article presents the principal applications and results published in the literature.

Assessment of the rotator cuff and glenoid labrum using an extremity MR system: MR results compared to surgical findings from a multi-center study

PURPOSE

To conduct a multi-center assessment of the use of a 0.2-T, extremity MR system (E-scan; General Electric Lunar Corp. and Esaote, Genoa, Italy) for identifying tears of the rotator cuff and glenoid labrum.

MATERIALS AND METHODS

A retrospective study was performed involving 160 patients (age range, 15-84 years old) from five facilities in the United States, comparing shoulder MR imaging to surgical findings. MR imaging of the shoulder was conducted as follows: shoulder coil; T1-weighted spin echo, coronal-oblique and axial images; short Tau inversion recovery (STIR), coronal-oblique images and axial images; and T2-weighted spin echo, coronal-oblique and sagittal-oblique images. The MR examinations were interpreted in an independent, prospective manner by two radiologists with extensive musculoskeletal MRI experience. Arthroscopic (N = 103) or open surgical (N = 57) procedures were performed within a mean of 53 days after MR imaging.

RESULTS

Surgical findings demonstrated rotator cuff tears in 131 patients and labral tears in 60 patients. For the rotator cuff, the sensitivity, specificity, positive predictive value, and negative predictive value were 90%, 93%, 98%, and 68%, respectively. For the labrum, the sensitivity, specificity, positive predictive value, and negative predictive value were 55%, 100%, 100%, and 82%, respectively.

CONCLUSIONS

There was good agreement when MR results obtained using the extremity MR system were compared to surgical findings for identifying rotator cuff tears, while the sensitivity of MR imaging for determining labral tears was relatively poor. Nevertheless, these findings were comparable to those reported in the peer-reviewed literature for MR systems operating at mid-, and high-field-strengths.

Utilization of Low-Field MR Scanners

The evident advantage of high-field MR (magnetic resonance) scanners is their higher signal-to-noise ratio, which results in improved imaging. While no reliable efficacy studies exist that compare the diagnostic capabilities of low- versus high-field scanners, the adoption and acceptance of low-field MRI (magnetic resonance imaging) is subject to biases. On the other hand, the cost savings associated with low-field MRI hardware are obvious. The running costs of a non-superconductive low-field scanner show even greater differences in favor of low-field scanners. Patient anxiety and safety issues also reflect the advantages of low-field scanners. Recent technological developments in the realm of low-field MR scanners will lead to higher image quality, shorter scan times, and refined imaging protocols. Interventional and intraoperative use also supports the installation of low-field MR scanners. Utilization of low-field systems has the potential to enhance overall cost reductions with little or no loss of diagnostic performance.

Comparison of high-field-strength versus low-field-strength MRI of the shoulder

OBJECTIVE

Previous studies have reported similar results of shoulder MRI versus arthroscopy for high-field-strength (1.5-T) and low-field-strength (0.2-T) units. We report our experience with the accuracy of high- versus low-field-strength units versus arthroscopy for detection of supraspinatus tendon tears and labral tears in the same patients. SUBJECTS AND METHODS. Three musculoskeletal radiologists prospectively interpreted shoulder MRIs from 40 patients who had a complete shoulder MRI examination on a 0.2-T system and limited imaging on a 1.5-T unit. Proton-density axial and fat-saturated T2-weighted coronal and sagittal sequences were performed. Each radiologist interpreted the open unit images first and the high-field-strength images second. Results from 28 patients who also underwent arthroscopy were also compared with the MRI interpretations. All scans were then retrospectively reinterpreted by consensus of the three reviewers, who were unaware of the patient's name, results of previous MRI, or arthroscopy report (if any).

RESULTS

High-field-strength images altered reviewers' interpretations of low-field-strength scans for nine of 40 patients. In four patients, full-thickness supraspinatus tendon tears could be diagnosed definitively on the high-field-strength unit but not on the open unit. Three labral tears and two superior labral anteroposterior lesions could be depicted definitively on the high-field-strength unit but not on the open unit. All tears were confirmed at arthroscopy.

CONCLUSION

High-field-strength MRI units provide better spatial and contrast resolution and allow more accurate interpretations than low-field-strength units; these findings may affect clinical treatment.

MR imaging of shoulder instability injuries in the athlete

Lesions leading to glenohumeral instability may result from acute trauma, atraumatic laxity, or repetitive microtrauma. Athletic activities, especially overhead throwing, may lead to a series of lesions involving the stabilizing structures of the shoulder. The resultant injuries and pathomechanics leading to shoulder symptoms can be classified as primary disease, primary instability, acute traumatic instability, and posterosuperior impingment syndrome. MR imaging with or without intrarticular or intravenous injection of contrast material, along with clinical examination and stress testing, provides valuable preoperative assessment.

Evaluation of the rotator cuff and glenoid labrum using a 0.2-Tesla extremity magnetic resonance (MR) system: MR results compared to surgical findings

The purpose of this investigation was to evaluate the diagnostic capabilities of magnetic resonance imaging (MRI) performed using a dedicated-extremity MR system in detecting lesions of the rotator cuff and glenoid labrum. This retrospective study compared the MR results obtained in 47 patients that underwent MRI using a 0.2-Tesla extremity MR system (E-scan) to the surgical findings. MR images of the shoulder were obtained as follows: shoulder coil, T1-weighted, coronal-oblique and axial images; short Tau inversion recovery (STIR), coronal-oblique images; and T2-weighted, coronal-oblique, sagittal-oblique, and axial images. The MR examinations were interpreted by three highly experienced, musculoskeletal radiologists. Open surgical (N = 26) or arthroscopic (N = 21) procedures were performed within a mean time of 33 days after MRI. The surgical findings revealed rotator cuff tears in 28 patients and labral lesions in 9 patients. For the rotator cuff tears, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 100%, 100%, and 90%, respectively. For the labral lesions, the sensitivity, specificity, positive predictive value, and negative predictive value were 89%, 95%, 80%, and 97%, respectively. The findings indicated that there was good agreement comparing the MR results obtained using the low-field extremity MR system to the surgical findings for determination of lesions of the rotator cuff and glenoid labrum. Notably, the statistical values determined for the use of this MR system were comparable to those reported in the peer-reviewed literature for the use of whole-body, mid- and high-field-strength MR systems.

Subscapularis Tendon Tear: Primary and Associated Signs on MRI

PURPOSE

The purpose of this work was to investigate signs of subscapularis tendon tear on MRI.

METHOD

Preoperative written interpretations of high field (n = 9) and low field (n = 7) MRI of 16 patients with tears confirmed at surgery or arthroscopy were reviewed, followed by retrospective review of these studies.

RESULTS

A preoperative diagnosis of subscapularis tear was made in five (31%) cases. On retrospective review, primary signs of tear were present in 15 (94%) cases and in two-thirds were limited to the cranial third of the tendon. Supraspinatus tears were present in 69% of cases. Associated findings included medial dislocation (n = 4) or subluxation (n = 3) of biceps tendon, biceps tendinopathy (n = 2), superior labral tear (n = 5), and effusions of superior subscapularis recess (n = 6), subcoracoid bursa (n = 2), or both (n = 5). One or more associated signs were present in 94% of cases.

CONCLUSION

Subscapularis tear is frequently missed on MRI. Recognizing that primary signs of tear may be limited to the cranial third of the subscapularis tendon and identifying associated signs should facilitate diagnosis.