Faculty Bibliography

Purpose: To see if 3D imaging could improve our understanding of rotator cuff tendon tear shapes on MRI.
Method(s): We performed a retrospective review of 1.5T/3T MR examinations, conducted over an 18-month period, of patients with arthroscopically proven full- thickness rotator cuff tears. Two orthopaedic surgeons reviewed the operative reports/arthroscopic photos for each patient, and characterized, in consensus, the shape of the tear based on a comparison of the tear's width (size) and length (retraction), and involvement of the rotator interval without measurements into the following categories: crescent, longitudinal, U or L-shaped longitudinal, and massive- type. Two musculoskeletal radiologists reviewed the pre-operative MR examination for each patient independently/blind to the arthroscopic findings. Initially, the readers characterized the shape of the tendon tears by reviewing the standard 2DMR sequences and using the same criteria as the surgeons used during their review of the scope images. Next, the readers measured and documented the width and length of each tendon tear using the 2D images. The shape of the tear was then classified based on a previously published MR-based system as either crescent, longitudinal, U or L-shaped, or massive. Four weeks after the initial imaging evaluation, 3DMR reconstructions of each tear were reviewed and the shape documented by each radiologist independently/blind to the arthroscopic results using the same system used by our orthopaedic colleagues. These results were then compared to the 2D imaging evaluations and arthroscopic findings. Statistical analysis included 95% confidence intervals, McNemar test, and intra-class correlation coefficients.
Result(s): A total of 34 patients were included in the study; 21 had crescent shaped tears and 13 had longitudinal tears during arthroscopy. Of the 13 longitudinal tears, 8 were subtyped as U-shaped, while 5 were described as L-shaped. 6 of the 13 longitudinal tears were additionally classified as massive-type. There was no significant difference when comparing the accuracy of the tear shape characterizations made on 2DMR imaging without measurements (pre) and with measurements (post). The accuracy for differentiating between crescent shaped, longitudinal, and massive tears was the same for reader 1, 70.6% (24/34; p=1) and more accurate using the post 2D data for reader 2 (67.6%(post) vs. 61.8%(pre), p=0.5). The accuracy for tear shape characterization between crescent and longitudinal using the 3D reconstructions for reader #1 was 97.1%(33/34) and 88.2% (30/34) for reader #2. When this characterization included subclassifying the longitudinal tears into U or-L shaped, the accuracy for reader #1 was 97.1% and 82.4% for reader #2. When further characterizing the longitudinal tears as massive or not, both readers had an accuracy of 76.9% (10/13). The overall accuracy of the 3D reconstructions was 82.4% (56/68), significantly different (p=0.021) from the post 2D accuracy (64.7%) and pre 2D accuracy (60.3%, p=0.001). The intraclass correlation coefficient for the 2D measurements of width and length were 0.81, moderate agreement, for width and 0.95, strong agreement, for length.
Conclusion(s): Our study has demonstrated that 3DMR reconstructions of the rotator cuff improve the accuracy of characterizing rotator cuff tear shapes compared to the current 2DMR imaging based techniques

Purpose: To see if failure of arthroscopic shoulder stabilization can be predicted by the evaluation of bipolar bone loss on MRI Methods: A retrospective review of 39 consecutive patients (40 shoulders) who underwent arthroscopic capsulolabral repair for recurrent, traumatic, anterior shoulder instability was performed. There were a total of 40 MRIs from 39 patients (31males, 8 females, mean age 31.7 yrs.). Mean follow-up was 19 months. Pre-operative plain radiographs, MRI scans, operative reports, arthroscopic photos, and post-operative records were reviewed for each patient. Surgical failure was defined as recurrent shoulder dislocation and/or persistent apprehension during normal range of motion. Each preoperative MRI scan was evaluated for bipolar bone loss by one musculoskeletal radiologist using the on-track/off-track (OOT) method in which the glenoid track (GT) and Hill-Sachs interval (HSI) aremeasured. According to this technique, the GT is calculated as 0.83D-d in which "D" represents the diameter of the intact glenoid and "d" corresponds to the amount of glenoid bone loss. The HSI represents the width of the Hill-Sachs lesion plus the width of the intact bone bridge between the rotator cuff attachment and the lateral aspect of the Hill-Sachs lesion. All measurements were in millimeters. Lesions were considered "off-track" if the HSI exceeded the GT and "on-track" if the HSI was less than the GT. These findings were then compared to the corresponding post-operative outcomes. Statistical analysis was carried out using the Fisher exact test.
Result(s): Of the 40 shoulders evaluated, 6 were considered surgical failures (3 with recurrent dislocation and 3 with persistent apprehension). The OOT method correctly predicted 1 of these failures and falsely predicted 6 failures in shoulders that were clinically stable. There was no significant difference when comparing stable to unstable shoulders with regards to age, size of GTand HSI. Overall, the OOT method sensitivity was 16.7% (1/6), specificity 82.4% (28/34), positive predictive value 14.3% (1/7), negative predictive value 84.9% (28/33) and overall accuracy 72.5% (29/40).
Conclusion(s): MRI evaluation of bipolar (humeral and glenoid) bone loss using the on-track/off-track method is a moderately accurate and specific, but insensitive technique to predict surgical failure after arthroscopic capsulolabral repair for shoulder instability

OBJECTIVE: The purpose of this study was to determine whether the simultaneous MRI evaluation of Hill-Sachs lesions and glenoid bone loss by use of the on-track off-track method can be used to predict engagement during arthroscopy. MATERIALS AND METHODS: The records of 75 consecutively registered patients (60 male patients, 15 female patients) with a history of previous anterior shoulder instability who underwent preoperative MRI of the shoulder and arthroscopy at our institution were reviewed. A total of 76 MRI examinations were included. Two readers reviewed the MR images of each patient blindly and independently and used the on-track off-track method to predict engagement. These results were compared with the findings related to engagement seen during arthroscopy, which was performed by one of seven orthopedic surgeons. Statistical analyses included Fisher exact test, logistic regression, ROC analysis, and calculation of intraclass correlation coefficients. RESULTS: Using the on-track off-track technique of reading MR images, the reviewers correctly predicted 13 of the 18 engaging (off-track) lesions (sensitivity, 72.2%). Among the 58 shoulders that did not engage (on-track), they correctly predicted 51 (specificity, 87.9%). Overall, the accuracy of the on-track off-track method was 84.2% with a positive predictive value of 65.0% and negative predictive value of 91.1%. CONCLUSION: Our study showed that the on-track off-track method can be used in MRI to accurately assess the bipolar bone loss seen in patients with anterior shoulder instability for predicting the presence of engaging, or off-track, lesions. This information can be used preoperatively to help guide the type of stabilization procedure performed on patients with anterior shoulder instability.

OBJECTIVE: The objectives of the article are to improve the radiologist's understanding of shoulder arthroscopy and see how it correlates with MRI. We review the basic principles of arthroscopy followed by a comparison of its strengths and weaknesses relative to MRI. This discussion is supplemented by a series of cases that show the relationship between arthroscopy and MRI in terms of the visualization of normal and abnormal anatomy in the diagnosis of common shoulder abnormalities. CONCLUSION: By understanding what our orthopedic colleagues are seeing (and not seeing) during arthroscopic shoulder surgery, we can better understand the strengths and weaknesses of MRI, which provides us the opportunity to improve our imaging interpretations and produce valuable management-guiding diagnostic reports.

OBJECTIVE: To see if there is an association between engagement on physical examination (PE) and the location of the Hill-Sachs lesion (HSL) as assessed by the modified biceps angle. MATERIALS AND METHODS: Sixty-two patients with a history of anterior shoulder dislocation, who underwent preoperative MRI and arthroscopy at our institution and were tested for engagement on PE, were collected. Two musculoskeletal radiologists reviewed the MR studies, noting the presence of an HSL and documenting the location of the HSL with the modified biceps angle. Statistical analysis included the Mann-Whitney (MW) test and ROC (receiver-operating characteristic) curve. RESULTS: Of 62 patients, there were 58 males and 4 females with a mean age of 30 (range 18-59 years). Twenty patients demonstrated engagement on PE, while 42 did not. All patients had evidence of an HSL on MRI and arthroscopy. The mean biceps angle for the engaging group was 151.5 +/- 13.9 degrees , and 142.4 +/- 17.3 degrees for the non-engaging group. The biceps angle was statistically significantly higher among patients who had engagement compared to those who did not (p = 0.027). Overall, diagnostic accuracy was highest for a biceps angle >149 degrees , which resulted in a sensitivity of 70 % and specificity of 67 %. CONCLUSION: The modified biceps angle, as measured on MRI, was significantly higher in patients who demonstrated engagement on physical examination than in those who did not. This supports the theory that the location of the Hill-Sachs lesion may play a role in engagement and may be its most important characteristic when determining its significance.

BACKGROUND: Gout and osteoarthritis (OA) are the most prevalent arthritides, but their relationship is neither well established nor well understood. OBJECTIVES: We assessed whether a diagnosis of gout or asymptomatic hyperuricemia (AH) is associated with increased prevalence/severity of knee OA. METHODS: One hundred nineteen male patients aged 55 to 85 years were sequentially enrolled from the primary care clinics of an urban Veterans Affairs hospital, assessed and categorized into 3 groups: gout (American College of Rheumatology Classification Criteria), AH (serum urate >/=6.8 mg/dL, no gout), and control (serum urate <6.8 mg/dL, no gout). Twenty-five patients from each group subsequently underwent formal assessment of knee OA presence and severity (American College of Rheumatology Clinical/Radiographic Criteria, Kellgren-Lawrence grade). Musculoskeletal ultrasound was used to detect monosodium urate deposition at the knees and first metatarsophalangeal joints. RESULTS: The study showed 68.0% of gout, 52.0% of AH, and 28.0% of age-matched control subjects had knee OA (gout vs control, P = 0.017). Odds ratio for knee OA in gout versus control subjects was 5.46 prior to and 3.80 after adjusting for body mass index. Gout subjects also had higher Kellgren-Lawrence grades than did the control subjects (P = 0.001). Subjects with sonographically detected monosodium urate crystal deposition on cartilage were more likely to have OA than those without (60.0 vs 27.5%, P = 0.037), with crystal deposition at the first metatarsophalangeal joints correlating most closely with OA knee involvement. CONCLUSIONS: Knee OA was more prevalent in gout patients versus control subjects and intermediate in AH. Knee OA was more severe in gout patients versus control subjects.

The mechanics of the throwing shoulder are complex, resulting in a variety of adaptations that can lead to increased performance for the athlete. These adaptations can eventually fail and result in pathology to the stabilizing structures of the shoulder, most notably the rotator cuff and glenoid labrum. The understanding of the relationship between the mechanisms and injuries is evolving, resulting in improved diagnostic, therapeutic, and preventative measures. Our goal is to clarify the relationship between the mechanisms, common types of injury, and their appearance on imaging, specifically MRI, in a comprehensive, easy-to-understand manner that will leave you more confident when evaluating this subset of patients.

OBJECTIVE. The article reviews a select group of traumatic upper extremity injuries that can be easily misinterpreted on radiographs. CONCLUSION. The awareness of these specific injuries and an understanding of their underlying pathophysiology and the role that radiographs can play in their evaluation will give the reader the best opportunity to make the important imaging findings and guide appropriate treatment.

OBJECTIVE. The purpose of this article is to review the current understanding of the underlying pathophysiology of the Hill-Sachs lesion and anterior glenoid bone loss and to discuss the role of imaging in identifying and accurately describing these injuries. CONCLUSION. Understanding the underlying mechanics of anterior shoulder instability that result in Hill-Sachs lesions and glenoid bone loss, the strengths and weaknesses of the different imaging modalities ordered for their evaluation, and the methods used to characterize these osseous injuries on imaging are essential for the radiologist in this clinical setting.