DOI: 10.1148/radiol.2272020462
(Radiology 2003;227:561-566.)
© RSNA, 2003
US of the Anterior Bundle of the Ulnar Collateral Ligament: Findings in Five Cadaver Elbows with MR Arthrographic and Anatomic Comparison—Initial Observations1
Jon A. Jacobson, MD,
Tim Propeck, MD,
David A. Jamadar, MB, BS, FRCS, FRCR,
Peter J. L. Jebson, MD and
Curtis W. Hayes, MD
1 From the Departments of Radiology (J.A.J., D.A.J., C.W.H.) and Orthopaedic Surgery (P.J.L.J.), University of Michigan Medical Center, 1500 E Medical Center Dr, TC-2910G, Ann Arbor, MI 48109-0326; and Department of Radiology, University of Missouri School of Medicine, Columbia (T.P.). Received April 24, 2002; revision requested June 21; revision received July 30; accepted October 9. Address correspondence to J.A.J. (e-mail: jjacobsn@umich.edu).
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ABSTRACT
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PURPOSE: To characterize the ultrasonographic (US) appearance of the anterior bundle of the ulnar collateral ligament of the elbow by comparing US images with magnetic resonance (MR) arthrograms and anatomic slices.
MATERIALS AND METHODS: The ulnar collateral ligament in four cadavers (eight elbows) was blindly evaluated with US by one musculoskeletal radiologist with experience in musculoskeletal US. These results were compared with standard arthrograms, MR arthrograms, and anatomic slices by consensus reading of two musculoskeletal radiologists. The criteria for an abnormal ulnar collateral ligament included contrast material extension into the ligament or fiber discontinuity, as documented by MR arthrography and anatomic slices.
RESULTS: Standard arthrography, MR arthrography, and anatomic slices demonstrated the ulnar collateral ligament to be unequivocally normal in three specimens and abnormal in two. The remaining three elbows did not meet the criteria for classification as either normal or abnormal, and thus they were excluded from the study. With US, the normal ulnar collateral ligament was fibrillar and hyperechoic between the medial epicondyle and proximal ulna. In the two abnormal cases, abnormal hypoechogenicity and ligament fiber disruption were noted. In addition, the proximal aspect of the ulnar collateral ligament varied from a cordlike structure to a broad attachment to the undersurface of the medial epicondyle with variable fat.
CONCLUSION: In this small sample, the anterior bundle of the ulnar collateral ligament is identified with US by its hyperechoic and compact fibrillar echotexture. The proximal attachment of the ulnar collateral ligament has a variable appearance. Hypoechogenicity and fiber disruption indicated ulnar collateral ligament abnormality.
© RSNA, 2003
Index terms: Elbow, MR, 422.1214 • Elbow, US, 422.1298 • Ultrasound (US), experimental studies
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INTRODUCTION
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Of the many musculoskeletal abnormalities that involve the elbow, injury to the ulnar collateral ligament may cause substantial pain and disability (1). This stabilizing structure is very important, particularly in the throwing athlete (2). An accurate diagnosis of this injury is essential for prompt and definitive treatment. Magnetic resonance (MR) imaging has been used with success in the diagnosis of ulnar collateral ligament abnormalities (1–3). The advantages of using intraarticular saline (4) and contrast material (5–9) in conjunction with MR imaging have also been demonstrated.
Musculoskeletal ultrasonography (US) has been used to evaluate abnormalities of the elbow (10–13), such as tears of the distal biceps brachii tendon (14) and epicondylitis (15). Although preliminary research has shown the potential application of US in the evaluation of ankle (16) and wrist (17) ligament abnormalities, little has been described in the evaluation of the ulnar collateral ligament of the elbow (12,13). The purpose of this study was to characterize the US appearance of the ulnar collateral ligament of the elbow (anterior bundle) with MR arthrographic and anatomic comparisons.
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MATERIALS AND METHODS
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Institutional review board approval was obtained prior to the initiation of this study. Both upper extremities of four human cadavers were obtained from the anatomic donations department at our institution. The specimens were nonembalmed, frozen fresh, and thawed to room temperature prior to imaging.
US Scanning
The eight elbow specimens were imaged with US, and 10-MHz and 12-MHz linear transducers (HDI 5000; Advanced Technology Laboratory, Bothell, Wash) were used by a fellowship trained musculoskeletal radiologist (J.A.J) with 9 years experience in musculoskeletal US. The examiner was not aware of the status of the ulnar collateral ligament at the time of US. Liberal transmission gel (Aquasonic 100; Parker Laboratories, Fairfield, NJ) was used in place of the standoff pad. The medial aspect of the elbow joint was imaged in the coronal plane with the elbow in 20°–30° of flexion. The characteristic contour of the medial epicondyle, which appeared hyperechoic with posterior acoustic shadowing typical of bone cortex, was used as an initial landmark. The transducer was then moved distally to image the proximal ulna. Several images of this region were obtained. An effort was made to image any ligament fibers, which are characterized by a compact and fibrillar hyperechoic echotexture, that were in the expected location of the ulnar collateral ligament. US imaging was concentrated over the expected location of the anterior bundle of the ulnar collateral ligament, which courses from the anteroinferior aspect of the medial epicondyle to the sublime tubercle along the medial aspect of the coronoid process of the proximal ulna (9,18).
Arthrography
An initial anteroposterior fluoroscopic image was obtained with the elbow in full extension prior to the imaging procedures to evaluate for any abnormality of the elbow joint that could potentially interfere with the study, such as a fracture, joint destruction, heterotopic ossification, or the presence of a metallic foreign body. A 1.5-inch 22-gauge spinal needle (Quincke; Becton Dickinson, Franklin Lakes, NJ) was inserted into the olecranon fossa of the distal humerus from a posterior approach with the elbow in 90° of flexion. Intraarticular needleplacement was confirmed with visualization of iodinated contrast agent (iohexol, Omnipaque; Nycomed, Princeton, NJ) between the humeral and ulnar articulation in a linear configuration. A solution of 0.1 mL gadopentetate dimeglumine (Magnevist; Berlex Imaging, Wayne, NJ), 9 mL of iohexol, 9 mL of unflavored gelatin (Kind and Knox, Englewood Cliffs, NJ) dissolved in water (two 8-oz packs of gelatin in 40 mL of boiling water), and five drops of methylene blue was prepared, and approximately 8–10 mL was injected into the elbow joint. A single anteroposterior fluoroscopic image was then obtained with the elbow in extension. One author (J.A.J.) performed all of the arthrographic and US examinations. Arthrography was performed 2 months after US and without knowledge of the US results.
MR Imaging
The eight elbows were then imaged by using a dedicated extremity surface coil with a 1.5-T magnet (Signa; GE Medical Imaging, Milwaukee, Wis). MR imaging sequences (256 x 192 matrix, 3-mm section thickness, 0.3-mm section gap, 12-cm field of view, two acquisitions) included T1-weighted (repetition time msec/echo time msec, 450–700/14–16) MR imaging with and without fat saturation in the coronal plane (relative to the humeral shaft) with the elbow in 20°–30° of flexion (6) to optimally visualize the ulnar collateral ligament.
Anatomic Slicing
The eight cadaveric elbows were frozen in the same position used for MR imaging and cut into 3-mm coronal slices relative to the humeral shaft by using a band saw. The surface of each slice was photographed.
Image Interpretation and Comparison
Image interpretation was divided into two parts. First, conventional arthrographic, MR arthrographic, and anatomic images were reviewed to classify the ulnar collateral ligament as normal or abnormal. Second, the US images were analyzed and compared with other images and anatomic sections. Evaluation of the integrity of the ulnar collateral ligament on MR and US images was limited to the anterior bundle.
Before the ulnar collateral ligament was classified as normal or abnormal, conventional arthrographic, MR arthrographic, and anatomic photographic images were reviewed by two musculoskeletal radiologists (J.A.J., D.A.J.), with 9 years and 6 years of experience, respectively, in elbow arthrography and MR imaging. The US results were unknown to the readers during this review. The ulnar collateral ligament was classified as abnormal if both MR arthrographic images and anatomic slices displayed extension of intraarticular contrast material into the ulnar collateral ligament or ligament discontinuity or absence. The presence of contrast material between the ulnar collateral ligament and the medial margin of the trochlea of the distal humerus was considered a normal recess, as previously described (7). The ulnar collateral ligament was classified as normal if all of the following criteria were met: conventional arthrograms depicted no abnormal extraarticular extension of contrast material, MR arthrograms depicted continuous ligament fibers between the medial epicondyle and proximal ulna, and photographs of anatomic slices showed continuous ligament fibers between the medial epicondyle and ulna. Conventional arthrography, MR arthrography, and anatomic slices from each subject were interpreted together.
The US images of the normal and abnormal ulnar collateral ligaments were then evaluated by the same observers. One of the retrospective reviewers (J.A.J.) performed the initial US examinations, but because the interval between US imaging and image interpretation was 3 years, the US results were unknown to the readers during this retrospective review. The images were evaluated for normal, hyperechoic ligamentous fibers between the medial epicondyle and the proximal ulna. The US images were then compared with the MR arthrographic images and anatomic slices.
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RESULTS
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After review of the conventional arthrographic, MR arthrographic, and photographic images of the anatomic slices, five of the eight specimens were classified as having an unequivocally normal or abnormal ulnar collateral ligament. There were three normal cases (left elbow from an 88-year-old woman, left elbow from a 74-year-old woman, and right elbow from a 91-year-old man) and two abnormal cases (left elbow from a 54-year-old man and left elbow from a 91-year-old man). The remaining three elbows did not meet the criteria to be classified as either normal or abnormal and thus were excluded from the study. The primary reason for exclusion was suboptimal or inadequate anatomic slices because of tissue destruction during slicing or a suboptimal plane of slicing.
Review of the US images, when compared with the other imaging studies and anatomic slices, showed the normal ulnar collateral ligament (Figs 1, 2) as a predominantly hyperechoic structure that is compact and fibrillar and located between the medial epicondyle and proximal ulna. The ligament appeared artifactually hypoechoic when oriented oblique to the ultrasound beam from anisotropy, although ligament fibers were still imaged (19). There was variability in the proximal aspect of the ulnar collateral ligament. In two normal specimens (aged 88 and 74 years), a distinct bundle of uniform thickness extended from the apex of the medial epicondyle to the ulna. Deep or lateral to this cordlike bundle, hyperechoic tissue was identified that did not demonstrate linear fibers. Comparison with MR arthrograms and photographs of anatomic slices demonstrated fat in this area. The third normal specimen (aged 91 years) showed increased thickness of the proximal aspect of the ulnar collateral ligament. In this case, ligament fibers originated from both the undersurface and the apex of the medial epicondyle. Comparison with MR arthrograms and photographs of anatomic slices showed broad attachment of the ligament fibers.
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Figure 1a. Normal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows normal hyperechoic and fibrillar echotexture (arrowheads) and adjacent hyperechoic fat (solid arrow). Note slight anisotropy (open arrow) where the ligament is oblique to the ultrasound beam. (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show intact ulnar collateral ligament (arrowheads) and adjacent fat (arrow). Low-signal-intensity areas in b represent tissue gas from tissue decomposition.
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Figure 1b. Normal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows normal hyperechoic and fibrillar echotexture (arrowheads) and adjacent hyperechoic fat (solid arrow). Note slight anisotropy (open arrow) where the ligament is oblique to the ultrasound beam. (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show intact ulnar collateral ligament (arrowheads) and adjacent fat (arrow). Low-signal-intensity areas in b represent tissue gas from tissue decomposition.
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Figure 1c. Normal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows normal hyperechoic and fibrillar echotexture (arrowheads) and adjacent hyperechoic fat (solid arrow). Note slight anisotropy (open arrow) where the ligament is oblique to the ultrasound beam. (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show intact ulnar collateral ligament (arrowheads) and adjacent fat (arrow). Low-signal-intensity areas in b represent tissue gas from tissue decomposition.
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Figure 2a. Normal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament (arrowheads) shows normal hyperechoic and fibrillar echotexture. Note broad origin on the undersurface of the medial epicondyle. (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show intact ulnar collateral ligament (arrowheads).
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Figure 2b. Normal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament (arrowheads) shows normal hyperechoic and fibrillar echotexture. Note broad origin on the undersurface of the medial epicondyle. (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show intact ulnar collateral ligament (arrowheads).
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Figure 2c. Normal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament (arrowheads) shows normal hyperechoic and fibrillar echotexture. Note broad origin on the undersurface of the medial epicondyle. (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show intact ulnar collateral ligament (arrowheads).
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The US appearance of the two abnormal ulnar collateral ligaments (Figs 3, 4) was that of abnormal focal hypoechogenicity, which disrupted the linear ligament fibers. In both cases, this abnormal area was at the proximal aspect of the ulnar collateral ligament adjacent to the medial epicondyle. Comparison with MR arthrograms and photographs of anatomic slices showed abnormal contrast material extension into the proximal ulnar collateral ligament with ligament fiber disruption.
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Figure 3a. Abnormal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows focal hypoechoic disruption (arrows) of ligament fibers with relatively normal ligament seen distally (arrowheads). (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show abnormal contrast material extension (arrows) into the proximal aspect of the ulnar collateral ligament. Arrowhead = normal distal ulnar collateral ligament.
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Figure 3b. Abnormal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows focal hypoechoic disruption (arrows) of ligament fibers with relatively normal ligament seen distally (arrowheads). (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show abnormal contrast material extension (arrows) into the proximal aspect of the ulnar collateral ligament. Arrowhead = normal distal ulnar collateral ligament.
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Figure 3c. Abnormal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows focal hypoechoic disruption (arrows) of ligament fibers with relatively normal ligament seen distally (arrowheads). (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show abnormal contrast material extension (arrows) into the proximal aspect of the ulnar collateral ligament. Arrowhead = normal distal ulnar collateral ligament.
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Figure 4a. Abnormal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows focal hypoechoic disruption (arrow) of ligament fibers with relatively normal ligament seen distally (arrowheads). (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show abnormal contrast material extension (arrow) into the proximal aspect of the ulnar collateral ligament (arrowhead).
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Figure 4b. Abnormal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows focal hypoechoic disruption (arrow) of ligament fibers with relatively normal ligament seen distally (arrowheads). (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show abnormal contrast material extension (arrow) into the proximal aspect of the ulnar collateral ligament (arrowhead).
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Figure 4c. Abnormal ulnar collateral ligament. E = medial epicondyle, F = common flexor tendon, U = ulna. (a) Longitudinal US image of the ulnar collateral ligament shows focal hypoechoic disruption (arrow) of ligament fibers with relatively normal ligament seen distally (arrowheads). (b) Coronal T1-weighted spin-echo MR image (700/14) and (c) coronal anatomic slice obtained after intraarticular administration of contrast material show abnormal contrast material extension (arrow) into the proximal aspect of the ulnar collateral ligament (arrowhead).
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DISCUSSION
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The results of our study confirm that the normal ulnar collateral ligament of the elbow can be imaged with US, and that this ligament appears hyperechoic with a compact fibrillar echotexture. This corresponds to the anterior bundle of the ulnar collateral ligament, which is substantially larger, better defined, and more functionally important with respect to valgus stability of the elbow when compared to the posterior and transverse components (1). US of the abnormal ulnar collateral ligaments in two specimens showed focal hypoechoic disruption of the ligament fibers, which represented abnormal contrast material extension and fiber disruption at MR arthrography and on anatomic slices.
We noted unexpected variability in the proximal aspect of the ulnar collateral ligament; however, the description of the ligament in the literature is also variable and therefore consistent with our findings. The anterior bundle is described as both cordlike (1,5) and triangular, with a broad attachment to the medial epicondyle (6). In addition, two layers of the anterior bundle have been described as having a thick intracapsular layer and a thin extracapsular layer that is confluent with the joint capsule (2). The images of the three normal ulnar collateral ligaments showed two appearances. The first appearance occurred in two specimens. A cordlike ligament originated near the apex or medial surface of the medial epicondyle and extended to the proximal ulna. In addition, fat was identified deep or lateral to the ulnar collateral ligament at the undersurface of the medial epicondyle. It is possible that this fat may be from volume averaging (6) or may be intraarticular fat (5), as has been previously proposed. Regardless, this explains the US depiction of hyperechoic tissue deep or lateral to the proximal ulnar collateral ligament. Lack of coexisting fibrillar echotexture will allow the differentiation between ligament and fat and the avoidance of overestimating the proximal thickness of the ulnar collateral ligament with US.
The second appearance of the normal ulnar collateral ligament (one specimen) was that of a broad attachment of the proximal ligament to the undersurface of the medial epicondyle. The MR arthrograms and anatomic slices showed the broad ligament attachment represented the US appearance of hyperechoic ligament fibers along the entire undersurface of the medial epicondyle. Authors of a prior study suggested that the broad proximal attachment of the ulnar collateral ligament might be due to depiction of a common attachment of the anterior and posterior bundles (5); however, the results of other studies indicate that the posterior bundle is not directly imaged (5), possibly because of its small size, inconsistent presence, and laxity during elbow extension (1). Further studies with healthy patients are required to determine if the variable appearance of the proximal ulnar collateral ligament in our specimens is applicable to the general population.
We acknowledge that the small sample size and advanced age of cadaveric specimens are factors that limit our study. This is partly due to the strict criteria for normal and abnormal ulnar collateral ligaments, as determined with comparative imaging and anatomic slices. In addition, we cannot confirm the exact cause of the abnormal ulnar collateral ligaments. While contrast material extension into the ligament with fiber disruption suggests a tear of the ligament and not isolated degeneration, partial-thickness tears cannot be differentiated from full-thickness tears, as contrast material extension beyond the joint— which indicates a full-thickness tear—is only present acutely (8). In addition, as both ulnar collateral ligament abnormalities were proximal, it is unknown if abnormalities of the other portions of the ligament have a different US appearance.
The analysis of US images relies on the technique and experience of the individual who acquired the US images and is an additional limitation; however, the US images were obtained by one investigator (J.A.J.) by using a standardized imaging protocol. Last, sensitivity and specificity in the diagnosis of ulnar collateral ligament abnormalities could not be assessed in this study.
This initial study establishes the US appearance of normal and abnormal ulnar collateral ligaments. Further investigations that apply these observations will help determine the true effectiveness of US in the assessment of ulnar collateral ligament abnormalities. The utility of dynamic imaging in US evaluation of the ulnar collateral ligament can then be assessed.
In conclusion, a normal ulnar collateral ligament appears as a hyperechoic and fibrillar structure with US, while an abnormal ulnar collateral ligament appears hypoechoic with discontinuous fibers. We noted variability in the proximal aspect of the ulnar collateral ligament, which included either cordlike or broad humeral origin and variable fat at the undersurface of the medial epicondyle. Further studies are needed to confirm these initial observations in a larger study group of patients.
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FOOTNOTES
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Author contributions: Guarantors of integrity of entire study, all authors; study concepts and design, all authors; literature research, J.A.J.; experimental studies, J.A.J., T.P.; data acquisition, J.A.J., T.P., D.A.J.; data analysis/interpretation, all authors; statistical analysis, J.A.J.; manuscript preparation, definition of intellectual content, editing, revision/review, and final version approval, all authors.
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ABSTRACT
INTRODUCTION
