(Radiology. 1999;211:233-236.)
© RSNA, 1999
Chronic Avulsive Injury of the Deltoid Insertion in Adolescents: Imaging Findings in Three Cases1
Lane F. Donnelly, MD,
Clyde A. Helms, MD and
George S. Bisset, III, MD
1 From the Department of Radiology, Division of Pediatric Radiology, Box 3808, Duke University Medical Center, Durham, NC 27710. Received March 20, 1998; revision requested June 17; revision received July 9; accepted September 2. Address reprint requests to L.F.D.
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Abstract
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The clinical and imaging (magnetic resonance [MR] imaging, radiography, and bone scintigraphy) findings in three adolescent boys with chronic avulsive injury at the deltoid insertion are presented. MR imaging enabled the exclusion of findings suggestive of malignancy and the localization of abnormalities to the deltoid insertion site. Findings included cortical thickening and irregularity of the deltoid tubercle, with or without adjacent soft-tissue edema.
Index terms: Bones, injuries, 416.4191 • Bones, MR, 416.121411 • Bones, radionuclide studies, 416.12172 • Humerus, 416.4191 • Muscles, injuries, 416.4191
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Introduction
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Chronic avulsive injuries may be identified at imaging either when patients undergo imaging for pain or incidentally when imaging is performed for other reasons. Appropriate interpretation of imaging studies that show chronic avulsive injuries is essential so that such injuries are not misinterpreted as suspicious for malignancy and thus do not result in unnecessary biopsy procedures with potentially misleading results. We present the imaging findings in three adolescent boys with chronic avulsion of the insertion of the deltoid muscle on the humerus.
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Materials and Methods
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We reviewed the clinical and imaging findings in three patients who had chronic avulsion of the deltoid insertion. All patients were examined by means of radiography and MR imaging of the humerus. MR imaging was performed with a 1.5-T magnet (Signa; GE Medical Systems, Milwaukee, Wis), with the humerus placed in an extremity wrap coil. All patients were examined with T1- (600/11 [repetition time msec/echo time msec]), intermediate- (3,800/16), and T2-weighted (3,800/80) fast spin-echo imaging in the axial and sagittal planes. In two of the three cases, fat saturation was used to obtain the fast spin-echo images. Bone scintigraphy was performed in two of the three patients with intravenous injection of 0.20 mCi (7.40 MBq) (maximum, 20 mCi [740 MBq]) per kilogram of body weight technetium 99m–labeled methylene diphosphonate (MDP). Whole-body scintigraphy was performed by using a single gamma camera, with additional lateral spot views of the humerus obtained with a thin-section collimator. The standard for documenting the lack of a malignant process as the cause of the imaging findings was the lack of sequelae at long-term follow-up.
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Case Reports
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Case 1
A 16-year-old, right-handed athletic (baseball and football player) boy presented to another hospital with symptoms of several months of pain in the region of the right humerus. Radiographs of the humerus showed an area of cortical thickening that contained irregular areas of hyperlucency (Fig 1a). Bone scintigraphy demonstrated focal increased uptake of 99mTc MDP in the middle region of the humerus. On the lateral spot view, the activity was localized to the anterior cortex of the humerus (Fig 1b). The patient was referred to our institution for MR imaging for evaluation of possible malignancy. The MR image showed cortical thickening (Fig 1c) within the region of the deltoid insertion. Compared with the remainder of the humeral cortex, which had low signal intensity, there was high T2-weighted signal intensity within the thickened cortex at the deltoid insertion. There also was high T2-weighted signal intensity consistent with edema within the soft tissues immediately adjacent to the deltoid insertion (Fig 1d).
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Figure 1a. Chronic avulsion of the deltoid insertion in a 16-year-old athletic boy with chronic pain. (a) Radiograph of the right humerus shows prominence of the cortical thickness and an area of irregular hyperlucency (arrow) within the region of the deltoid insertion. (b) Lateral spot view on 99mTc MDP bone scintigram shows focal increased uptake (arrow) in the anterior cortex of the middle region of the humerus. (c) Intermediate-weighted (3,800/16) axial MR image shows cortical thickening and irregularity within the region of the deltoid insertion (arrows). Compared with the remainder of the humeral cortex, which has low signal intensity, there is high signal intensity within the thickened cortex at the deltoid insertion. (d) Intermediate-weighted (3,800/16) axial MR image just inferior to c shows high-signal-intensity edema (arrows) within the soft tissues immediately adjacent to the deltoid insertion.
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Figure 1b. Chronic avulsion of the deltoid insertion in a 16-year-old athletic boy with chronic pain. (a) Radiograph of the right humerus shows prominence of the cortical thickness and an area of irregular hyperlucency (arrow) within the region of the deltoid insertion. (b) Lateral spot view on 99mTc MDP bone scintigram shows focal increased uptake (arrow) in the anterior cortex of the middle region of the humerus. (c) Intermediate-weighted (3,800/16) axial MR image shows cortical thickening and irregularity within the region of the deltoid insertion (arrows). Compared with the remainder of the humeral cortex, which has low signal intensity, there is high signal intensity within the thickened cortex at the deltoid insertion. (d) Intermediate-weighted (3,800/16) axial MR image just inferior to c shows high-signal-intensity edema (arrows) within the soft tissues immediately adjacent to the deltoid insertion.
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Figure 1c. Chronic avulsion of the deltoid insertion in a 16-year-old athletic boy with chronic pain. (a) Radiograph of the right humerus shows prominence of the cortical thickness and an area of irregular hyperlucency (arrow) within the region of the deltoid insertion. (b) Lateral spot view on 99mTc MDP bone scintigram shows focal increased uptake (arrow) in the anterior cortex of the middle region of the humerus. (c) Intermediate-weighted (3,800/16) axial MR image shows cortical thickening and irregularity within the region of the deltoid insertion (arrows). Compared with the remainder of the humeral cortex, which has low signal intensity, there is high signal intensity within the thickened cortex at the deltoid insertion. (d) Intermediate-weighted (3,800/16) axial MR image just inferior to c shows high-signal-intensity edema (arrows) within the soft tissues immediately adjacent to the deltoid insertion.
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Figure 1d. Chronic avulsion of the deltoid insertion in a 16-year-old athletic boy with chronic pain. (a) Radiograph of the right humerus shows prominence of the cortical thickness and an area of irregular hyperlucency (arrow) within the region of the deltoid insertion. (b) Lateral spot view on 99mTc MDP bone scintigram shows focal increased uptake (arrow) in the anterior cortex of the middle region of the humerus. (c) Intermediate-weighted (3,800/16) axial MR image shows cortical thickening and irregularity within the region of the deltoid insertion (arrows). Compared with the remainder of the humeral cortex, which has low signal intensity, there is high signal intensity within the thickened cortex at the deltoid insertion. (d) Intermediate-weighted (3,800/16) axial MR image just inferior to c shows high-signal-intensity edema (arrows) within the soft tissues immediately adjacent to the deltoid insertion.
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There were no soft-tissue masses or marrow signal intensity abnormalities. Because of the absence of MR imaging findings of malignancy and the localization of the findings to the region of the deltoid insertion, the findings were presumed to be secondary to chronic avulsion. The biopsy of this lesion that was originally scheduled to follow the MR imaging examination was canceled. The patient's pain resolved after rest and conservative treatment. Two years later, the patient had no other medical problems.
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Case 2
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A 16-year-old, right-handed boy who worked as a migrant agricultural worker underwent bone scintigraphy during the work-up of a recently diagnosed osteosarcoma of the right femur. In addition to showing marked uptake of 99mTc MDP in the area of the osteosarcoma of the femur, bone scintigraphy demonstrated focal increased uptake in a portion of the anterior cortex of the proximal third of the humerus (Fig 2a). The lateral spot view showed the activity to lie in the anterior cortex. There were no other findings to suggest other sites of metastatic disease. The patient had no symptoms or findings related to the humerus at physical examination.
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Figure 2a. Chronic avulsion of the deltoid insertion identified during the imaging work-up of osteosarcoma of the right femur in a 16-year-old boy. (a) Whole-body 99mTc MDP bone scintigram shows focal uptake (arrowhead) overlying a portion of the proximal one-third of the humerus and a large area of increased uptake (arrow) in the region of osteosarcoma of the right middle region of the femur. On the lateral spot view of the humerus (not shown), the activity was localized to the anterior cortex. (b) Intermediate-weighted (3,800/16) axial MR image shows increased cortical thickness and cortical irregularity of the deltoid insertion (arrows).
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Figure 2b. Chronic avulsion of the deltoid insertion identified during the imaging work-up of osteosarcoma of the right femur in a 16-year-old boy. (a) Whole-body 99mTc MDP bone scintigram shows focal uptake (arrowhead) overlying a portion of the proximal one-third of the humerus and a large area of increased uptake (arrow) in the region of osteosarcoma of the right middle region of the femur. On the lateral spot view of the humerus (not shown), the activity was localized to the anterior cortex. (b) Intermediate-weighted (3,800/16) axial MR image shows increased cortical thickness and cortical irregularity of the deltoid insertion (arrows).
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Radiographs of the humerus were normal. MR imaging, performed to evaluate for a potential metastatic lesion, demonstrated cortical thickening and irregularity in the region of the deltoid insertion (Fig 2b). The humerus appeared to be normal otherwise, without marrow signal intensity abnormalities or a soft-tissue mass to suggest metastatic disease. Because of the absence of MR imaging findings of malignancy and the localization of the findings to the region of the deltoid insertion, the findings were presumed to be secondary to chronic avulsion. The scheduled biopsy of the lesion was canceled. At follow-up bone scintigraphy 6 months later, there was no change in the appearance of the humerus. At follow-up bone scintigraphy 1 year later, the uptake of 99mTc MDP at the deltoid tubercle was much less prominent, and the patient continued to be free of symptoms related to the humerus.
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Case 3
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A 13-year-old, right-handed athletic boy presented with chronic pain in the middle region of the right humerus. Radiographs of the humerus showed cortical thickening with an area of hyperlucency in the region of the deltoid insertion (Fig 3a). MR imaging demonstrated cortical thickening and irregularity at the deltoid insertion on the humerus (Fig 3b). There was increased T1- and T2-weighted signal intensity within the soft tissues immediately adjacent to the deltoid insertion (Fig 3c). No MR imaging findings of malignancy were present. Because of the absence of MR imaging findings of malignancy and the localization of the findings to the region of the deltoid insertion, the findings were presumed to be secondary to chronic avulsion. A biopsy of this lesion was originally scheduled to follow the MR imaging examination, but it was canceled. The patient's pain resolved after rest and conservative treatment. At follow-up more than 2 years later, the patient had no medical problems related to the humerus.
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Figure 3a. Chronic avulsion of the deltoid insertion in a 13-year-old boy with chronic pain. (a) Radiograph of the humerus shows slight enlargement of and cortical irregularity in the region of the deltoid insertion (arrow). (b) T1-weighted (600/11) axial MR image shows thickened, irregular cortex at the deltoid insertion (arrows) and high signal intensity in the adjacent soft tissues (arrowhead) consistent with subacute hemorrhage. (c) T2-weighted (3,800/80) non–fat-saturated MR image shows increased signal intensity (arrows) within the soft tissues immediately adjacent to the deltoid insertion.
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Figure 3b. Chronic avulsion of the deltoid insertion in a 13-year-old boy with chronic pain. (a) Radiograph of the humerus shows slight enlargement of and cortical irregularity in the region of the deltoid insertion (arrow). (b) T1-weighted (600/11) axial MR image shows thickened, irregular cortex at the deltoid insertion (arrows) and high signal intensity in the adjacent soft tissues (arrowhead) consistent with subacute hemorrhage. (c) T2-weighted (3,800/80) non–fat-saturated MR image shows increased signal intensity (arrows) within the soft tissues immediately adjacent to the deltoid insertion.
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Figure 3c. Chronic avulsion of the deltoid insertion in a 13-year-old boy with chronic pain. (a) Radiograph of the humerus shows slight enlargement of and cortical irregularity in the region of the deltoid insertion (arrow). (b) T1-weighted (600/11) axial MR image shows thickened, irregular cortex at the deltoid insertion (arrows) and high signal intensity in the adjacent soft tissues (arrowhead) consistent with subacute hemorrhage. (c) T2-weighted (3,800/80) non–fat-saturated MR image shows increased signal intensity (arrows) within the soft tissues immediately adjacent to the deltoid insertion.
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Discussion
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An avulsion injury is a structural failure of bone at a tendinous or aponeurotic insertion related to a chronic tensile force applied from a musculoskeletal unit (1). The injury may be acute and related to a single violent tensile event, or chronic and related to multiple repeated events. Adolescents are prone to avulsive injuries related to their propensity for great strength, ability to sustain extreme levels of activity, and growing apophyses (1,2).
The cortical irregularity and periosteal reaction that can be seen on radiographs in association with chronic avulsive injuries can mimic the radiographic changes seen with malignancy (1–7). In addition, if unwarranted biopsies of these areas are performed, the histologic changes associated with the healing callus of the avulsion injury may be misinterpreted as malignancy (5,6). Therefore, knowledge of the sites predisposed to avulsion injury is vital for appropriate interpretation of the imaging findings and avoidance of unnecessary biopsy with potentially misleading results. Those sites predisposed to avulsion injuries that have been most stressed in the literature are the muscular insertion sites of the pelvis and proximal femurs, such as the anterosuperior iliac spine, anteroinferior iliac spine, ischial apophysis, and lesser trochanter and posteromedial cortex of the distal femur (1–7). The insertion of the deltoid muscle on the humerus has not been stressed as a site prone to avulsion injury.
The deltoid muscle is the dominant abductor of the shoulder and inserts on a bony prominence located on the anterolateral cortex of the middle to proximal thirds of the humerus called the deltoid tubercle. There is a great deal of variability in the range of cortical thickness and irregularity of the deltoid tubercle seen on radiographs obtained in healthy individuals (8,9). Therefore, radiographs are often not helpful in either diagnosing or excluding avulsive injury. In two of the three patients that we encountered with deltoid avulsive injuries, there was prominent thickness and irregularity of the cortex at the deltoid tubercle. The other patient had normal radiographs of the humerus.
The MR imaging findings of tendon injuries have been well described (10–13). With acute tendon injuries, increased T2-weighted signal intensity is seen within the injured tendon, at the tendon insertion site, or within the adjacent soft tissues (10–13). With chronic avulsion, the degree of edema and resultant increased T2-weighted signal intensity may be less prominent, and cortical thickening at the insertion site may be the dominant finding. In all three of the patients that we encountered with chronic avulsive injury of the deltoid insertion site, MR imaging help to exclude findings suggestive of malignancy, such as a soft-tissue mass, cortical destruction, or abnormal marrow signal intensity. The MR imaging findings of chronic deltoid avulsion were prominent thickness and irregularity of the cortex at the deltoid insertion, often with edema in the adjacent soft tissues. The findings were localized to the region of the deltoid insertion. It was the combination of the absence of findings of malignancy and the localization of findings to the deltoid insertion that enabled the diagnosis of chronic avulsion injury. In both cases in which bone scintigraphy was performed, the findings were supportive of an avulsion injury. There was high focal uptake of 99mTc MDP in an area of the anterior cortex of the humerus in the region of the deltoid tubercle.
The clinical presentation of the patients was variable. Two of the three patients were symptomatic, with prolonged periods of focal pain. The other patient was asymptomatic. All three patients were physically active adolescents: Two were athletes, and one was a migrant agricultural worker. We presume that this physical activity predisposed these patients to the findings of chronic avulsion. All of the patients were treated conservatively without sequelae at long-term follow-up.
In conclusion, in cases of chronic avulsion of the deltoid insertion, which may be encountered as a source of pain or seen incidentally, MR imaging can be helpful both in excluding findings of malignancy and in localizing the abnormality to the deltoid insertion.
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Footnotes
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Abbreviation: MDP = methylene diphosphonate
Author contributions: Guarantor of integrity of entire study, L.F.D.; study concepts, L.F.D., C.A.H., G.S.B.; study design, L.F.D., C.A.H.; definition of intellectual content, L.F.D., C.A.H., G.S.B.; literature research, L.F.D., C.A.H.; manuscript preparation, L.F.D.; manuscript editing, C.A.H., G.S.B.
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References
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Abstract
Introduction
