Faculty Bibliography

Anatomic reconstruction of the humeral head with osteochondral allograft has been reported as a solution for large Hill-Sachs lesions with or without glenoid bone loss. However, to date, varying techniques have been used. This technical note describes an arthroscopic reconstruction technique using fresh-frozen, side- and size-matched osteochondral humeral head allograft. Allograft plugs are press fit into the defect without internal fixation and seated flush with the surrounding articular surface. This technique restores the native articular contour of the humeral head without compromising shoulder range of motion. Potential benefits of this all-arthroscopic approach include minimal trauma to the soft tissue and articular surface without the need for hardware or staged reoperation.

OBJECTIVE. The objective of our study was to see whether there is an association between engagement on physical examination and the location or size of a Hill-Sachs lesion and the presence and degree of glenoid bone loss as assessed on MRI. MATERIALS AND METHODS. Thirty-three consecutive patients (32 males and one female) with a history of anterior shoulder dislocation who underwent preoperative MRI and arthroscopy at our institution and were tested for engagement on physical examination over a 9-month period were included in the study. Two blinded readers reviewed each study independently and documented the presence and size of the Hill-Sachs lesion, location of the Hill-Sachs lesion with a modified biceps angle, and presence and size of glenoid bone loss. Statistical analysis included the Mann-Whitney, logistic regression, Pearson correlation, and intraclass correlation tests. RESULTS. Eleven patients had evidence of an engaging Hill-Sachs lesion on physical examination and 22 did not. There was no statistically significant difference between any of the dimensions or overall area of the Hill-Sachs lesion when comparing the group with an engaging Hill-Sachs lesion and the group with a nonengaging lesion (surface area, 3.60 vs 3.23 cm(3), respectively; p = 0.272). There was a trend for a larger biceps angle in the engaging group without a statistically significant difference (mean, 154.5 degrees vs 143.9 degrees ; p = 0.069). There was a statistically significant difference in the amount of glenoid bone loss in the engaging group compared with the nonengaging group (mean, 20.2% vs 6.0%; p = 0.001). CONCLUSION. There is a significant association between an engaging Hill-Sachs lesion on physical examination and the degree of glenoid bone loss as well as a trend toward increased engagement with more medially oriented Hill-Sachs lesions. These findings show the importance of considering both the Hill-Sachs lesion and glenoid bone loss when evaluating patients with engagement.

Objective: To determine the accuracy of MR imaging for the evaluation of the subscapularis tendon as well as define imaging findings that will increase accuracy. MATERIALS AND METHODS: Retrospective review of the MR and operative (OR) reports of 286 patients was conducted and reviewed for the presence/degree (partial (PT)/full-thickness (FT)) of tearing; only PT articular tears were included. The presence of a supraspinatus tear and time interval between surgery and MRI were also documented. All of the PT tears called on MRI were also reviewed to see if there was a statistically significant association between certain imaging characteristics and the presence of a tear in surgery. Statistical analysis included 95 % confidence intervals, Fisher's exact, and exact Mann-Whitney tests. RESULTS: A total of 244 patients were included in the study with a total of 25 subscapularis tears, 16 PT and nine FT, and 219 intact tendons in arthroscopy; 20/25 tears and 200 intact sensitivity of 80%, specificity of 91%, accuracy of 90%, positive predictive value of 51%, and negative predictive value of 98 %. There was a significant association between the presence of a PT tear during arthroscopy and fluid-like signal within the tendon on more than one imaging plane (p<0.001) with an accuracy of 90%. CONCLUSIONS: This study reflects a musculoskeletal radiology section's experience with the diagnosis of subscapularis tendon pathology, demonstrating that MRI could be used to accurately evaluate the subscapularis tendon. An understanding of certain imaging pitfalls and the presence of fluid-like signal on multiple imaging planes should increase the diagnostic accuracy of the radiologist evaluating the subscapularis tendon for the presence of a tear.

OBJECTIVES:: To determine the lowest estimated radiation dose necessary to reproducibly detect intra-articular air in the knee joint of a cadaver model. METHODS:: 10 adult fresh-frozen cadaver knees with intact joint capsules provided by Science Care(R), Phoenix, AZ. were thawed and scanned at 5 decreasing radiation doses (decreasing by approximately half from 8.42 mGy to 0.74 mGy) after introducing increasing volumes (0 cc, 0.1 cc, 0.3 cc, 0.5 cc, 0.7 cc, 0.9cc) of intra-articular air. Scans were performed using 2.0 mm slice-thickness from the distal 1/3 of the femur to the proximal 1/3 of the tibia. Sagittal and coronal reconstructions of each scan using 1.0 mm slice-thickness were rendered. All scans were reviewed by 1) a single attending radiologist, 2) a single attending orthopedic surgeon, and 3) a single chief resident, for the presence of intra-articular air. RESULTS:: The sensitivity and specificity of CT scan to detect intra-articular air at each volume of intra-articular air (0.1 cc, 0.3 cc, 0.5 cc, 0.7 cc, 0.9cc) was 100% at 0.74 mGy - the radiation threshold dose (RadTH) (scan parameters: voltage 80kV, current: 33mA, and scan time: 12.17 sec). The effective radiation dose at 0.74 mGy for a CT scan of the knee is approximately 0.10 mSV CONCLUSIONS:: CT scan to detect traumatic knee arthrotomies can be successfully accomplished at a threshold radiation dose of 0.74 mGy and for an intra-articular volume of 0.1cc of air. This low radiation dose protocol and volume of intra-articular air should be taken into consideration with future studies evaluating the use of CT scan to detect traumatic arthrotomies.

OBJECTIVE. The purpose of this study was to define and correlate the appearance of the rotator cable on MRI with arthroscopy, band-saw cadaveric sections, and histology. MATERIALS AND METHODS. Two cadaveric shoulders underwent 3-T MRI, band-sawing, and histologic evaluation. Three readers evaluated the MRI for the presence of the cable, and the same readers and a pathologist reviewed the macroscopic and microscopic specimens for a structure that corresponded to the cable. Cadaver 1 underwent arthroscopic evaluation to evaluate for the presence of a cable. Seventy consecutive shoulders that underwent 1.5- or 3-T MRI were also reviewed for the presence of the cable and evaluation of its characteristics (location, thickness, and width). RESULTS. A linear band of hypointense signal intensity was found along the undersur-face of the supraspinatus and infraspinatus tendons on both cadaveric MR images, which correlated to a linear band of tissue in the same location on macroscopic and microscopic evaluation and linear thickening along the cuff articular surface on arthroscopy consistent with the cable. The cable was seen in 74.3% of the MRI studies in both sagittal and coronal planes with a mean (+/- SD) distance of the cable from the medial margin of the enthesis of 1.33 +/- 0.27 cm, a mean width of the cable of 1.24 +/- 0.31 cm, and a mean thickness of 0.19 +/- 0.05 cm. CONCLUSION. The rotator cable is a structure that can be consistently seen on gross anatomic and histologic analysis, arthroscopy, and MRI in the intact rotator cuff. Familiarity with the typical location and morphology of the cable may allow easier characterization of disease that can involve the cable, such as rotator cuff tears.

OBJECTIVE: To create 3DMR osseous models of the shoulder similar to 3DCT models using a gradient-echo-based two-point/Dixon sequence. MATERIALS AND METHODS: CT and 3TMR examinations of 7 cadaveric shoulders were obtained. Glenoid defects were created in 4 of the cadaveric shoulders. Each MR study included an axial Dixon 3D-dual-echo-time T1W-FLASH (acquisition time of 3 min/30 s). The water-only image data from the Dixon sequence and CT data were post-processed using 3D software. The following measurements were obtained on the shoulders: surface area (SA), height/width of the glenoid and humeral head, and width of the biceps groove. The glenoid defects were measured on imaging and compared with measurements made on en face digital photographs of the glenoid fossae (reference standard). Paired t tests/ANOVA were used to assess the differences between the imaging modalities. RESULTS: The differences between the glenoid and humeral measurements were not statistically significant (cm): glenoid SA 0.12 +/- 0.04 (p = 0.45) and glenoid width 0.13 +/- 0.06 (p = 0.06) with no difference in glenoid height measurement; humeral head SA 0.07 +/- 0.12 (p = 0.42), humeral head height 0.03 +/- 0.06 (p = 0.42), humeral head width 0.07 +/- 0.06(p = 0.18), and biceps groove width 0.02 +/- 0.01 (p = 0.07). The mean/standard deviation difference between the reference standard and 3DMR measurements was 0.25 +/- 0.96 %/0.30 +/- 0.14 mm; 3DCT 0.25 +/- 0.96 /0.75 +/- 0.39 mm. There was no statistical difference between the measurements obtained on 3DMR and 3DCT (percentage, p = 0.45; mm, p = 0.20). CONCLUSION: Accurate 3D osseous models of the shoulder can be produced using a 3D two-point/Dixon sequence and can be added to MR examinations with a minor increase in imaging time, used to quantify glenoid loss, and may eliminate the need for pre-surgical CT examinations.

Traumatic dislocation of the shoulder is a frequent injury in the young and active population. An acute shoulder dislocation often denotes a onetime traumatic episode, whereas chronic shoulder instability indicates multiple recurrent dislocations. Imaging, in particular MRI, is a useful tool that can accurately demonstrate the typical soft tissue and osseous markers of shoulder dislocation. However, the ability to differentiate between first time versus recurrent dislocation based on imaging remains in question. In this article, we describe the underlying biomechanics of glenohumeral stability as well as the imaging features and treatment options of shoulder dislocation. A review of current literature is presented, aimed to shed light about the potential role of imaging in distinguishing first dislocation versus chronic instability.

OBJECTIVE: The purpose of this study is to assess the accuracy of MRI quantification of glenoid bone loss and to compare the diagnostic accuracy of MRI to CT in the measurement of glenoid bone loss. MATERIALS AND METHODS: MRI, CT, and 3D CT examinations of 18 cadaveric glenoids were obtained after the creation of defects along the anterior and anteroinferior glenoid. The defects were measured by three readers separately and blindly using the circle method. These measurements were compared with measurements made on digital photographic images of the cadaveric glenoids. Paired sample Student t tests were used to compare the imaging modalities. Concordance correlation coefficients were also calculated to measure interobserver agreement. RESULTS: Our data show that MRI could be used to accurately measure glenoid bone loss with a small margin of error (mean, 3.44%; range, 2.06-5.94%) in estimated percentage loss. MRI accuracy was similar to that of both CT and 3D CT for glenoid loss measurements in our study for the readers familiar with the circle method, with 1.3% as the maximum expected difference in accuracy of the percentage bone loss between the different modalities (95% confidence). CONCLUSION: Glenoid bone loss can be accurately measured on MRI using the circle method. The MRI quantification of glenoid bone loss compares favorably to measurements obtained using 3D CT and CT. The accuracy of the measurements correlates with the level of training, and a learning curve is expected before mastering this technique.

OBJECTIVE: To evaluate the degree and location patterns of subscapularis tendon injury in patients with prior anterior shoulder dislocation (ASD). MATERIAL AND METHODS: Forty-five consecutive MR shoulder examinations in patients with a history of ASD and 20 consecutive MR examinations in patients without prior dislocation were reviewed. Two readers assessed for the presence and location of tendinosis and tearing in the subscapularis tendon, which was divided into three segments: superior, middle, and inferior. The readers also documented the presence of anterior labral tears, osseous Bankart defects and Hill-Sachs lesions. Fisher's exact tests were performed to analyze the different types of pathology and their locations. RESULTS: Subscapularis tendinosis, and partial thickness and full thickness tears were more common in patients with a history of ASD. Tendinosis was found in 60-64.4% of the dislocation patients compared with 40% of the non-dislocation group. When stratified by location, the middle and inferior thirds were the most commonly affected with statistical significance (p < 0.05) found in tearing of the inferior third. Anterior labral tears, osseous Bankart defects, and Hill-Sachs lesions were more common in the dislocation group with statistically significant associations with tendinosis in the middle and inferior thirds and tearing of the middle third (p < 0.05). CONCLUSION: Our study suggests an association between middle and inferior subscapularis tendon pathology and prior anterior shoulder dislocation. Based on our results, careful MR assessment of the subscapularis tendon by the radiologist is indicated in the setting of ASD as injury of this structure can be symptomatic and may be amenable to treatment.