Soft-Tissue Pseudotumors of the Hip

Transcription

1 Soft-Tissue Pseudotumors of the Hip Poster No.: C-1564 Congress: ECR 2016 Type: Educational Exhibit Authors: M. R. Kaleel, J. Czajka, M. O'Loughlin, H. Baweja ; HARTFORD, Connecticut/US, Hartford/US Keywords: MR, CT, Musculoskeletal system, Musculoskeletal soft tissue, Extremities, Normal variants, Surgery, Trauma, Inflammation, Prostheses DOI: /ecr2016/C-1564 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 36

2 Learning objectives The purpose of our educational exhibit is to: Explain how post-operative, post-traumatic and degenerative/stress-induced lesions of the hip may result in clinically apparent soft tissue masses. Review the imaging characteristics of a variety of acquired soft tissue pseudotumors of the hip encountered at our institution. Differentiate imaging features of suspicious soft tissue pseudotumor from malignancy. Page 2 of 36

3 Background Post-operative, post-traumatic and degenerative/stress-induced lesions of the hip may result in clinically apparent soft tissue masses. The complex anatomy of the hip region allows for multiple potential spaces for the development of pseudotumors, including the subcutaneous fat, bursa, fascia and musculature. A pseudotumor may be a solid or cystic "mass" at a site of prior trauma, surgery or inflammation that clinically and radiographically can mimic a neoplasm. Page 3 of 36

4 Findings and procedure details 1. Post-operative pseudotumors 1.1 Gluteal Free Silicone Injection Free silicone injections have long been used for cosmetic procedures to enhance the lips, cheekbones, chin, breasts, hips, and buttocks. These procedures quickly grew out of favor as the health hazards associated with them became widely known. The adverse effects of free silicone injections were first reported in 1975 by Ellenbogen et al with a case of granulomatous hepatitis. Local complications of fat injection include fat necrosis, cellulitis, abscess and hematoma. However, more significantly, free silicone injections have been reported to lead to multi organ failure and death. Although officially banned in the USA and Europe, these procedures remain commonly performed on the black market without adequate medical supervision or regulation. Periodically, silicone injection procedures come to mainstream attention as news reports of patient fatalities following unauthorized injections. Silicone injections demonstrate classic radiographic patterns that can easily be recognized, which is useful when history is not provided and there is a clinically palpable soft tissue mass. Figure 1 presents the imaging findings of a gluteal free silicone injection on CT. On CT, the imaging findings include well-defined soft tissue nodules, with or without calcification. The nodules may be confluent and may be surrounded by fat stranding. Page 4 of 36

5 Fig. 1: Axial (A) and Coronal (B) CT scan showing clusters of soft tissue nodules with surrounding fat stranding in the gluteal subcutaneous fat, which is a classic appearance and location for gluteal silicone injections. References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US Figure 2 demonstrates the imaging findings of silicone injections on MRI. The lesions are often hyperintense nodules on T2 weighted images and demonstrate variable intensity on T1 weighted imaging. Page 5 of 36

6 Fig. 2: Axial STIR with Water Sat (A), Axial T1 (B), Coronal STIR (C), and Coronal T1 (D) showing clusters of soft tissue nodules with surrounding fat stranding in the gluteal subcutaneous fat, which is a classic appearance and location for gluteal silicone injections. The nodules are hyperintense on T2 weighted imaging and, in this example, are isointense to muscle on T1 weighted images. Silicone nodules may have a variable appearance on T1 weighted imaging. References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US 1.2 Metal-on-Metal Pseudotumor / ALVAL Page 6 of 36

7 Modern metal-on-metal total hip replacements can be complicated by a soft-tissue reaction, described as pseudotumor or aseptic lymphocytic vasculitis-associated lesions (ALVAL). ALVAL lesions are large focal solid or semiliquid masses that surround metalon-metal prosthetic devices and occur months to years after surgery. The most common prosthesis affected is the hip. ALVAL lesions are thought to result from excessive wear on these prostheses with the release of nanometer-sized particles. This leads to a foreign body reaction cascade resulting in sterile inflammatory lesions, which can mimic local effects of malignancy or infection. ALVAL can cause pain and swelling, and may also result in periprosthetic fracture. These lesions are classically associated with a poor outcome after revision surgery. Figure 3 presents the imaging findings of an ALVAL lesion on MRI. ALVAL lesions can either demonstrate standard fluid signal characteristics or a mixed cystic and solid appearance that is heterogeneously isointense and hyperintense on T2weighted images. They extend from the prosthesis and characteristically are demarcated by a thick, ragged capsule. The MRI signal characteristics of the capsule are isointense on T1-weighted and low signal intensity on T2-weighted images. Page 7 of 36

8 Fig. 3: Axial Proton Density (A), Coronal Proton Density (B), Sagittal Proton Density (C), and Coronal STIR (D) sequences showing a lobular, slightly complex cystic fluid collection (red arrow) contiguous with the left hip prosthesis (green arrow). References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US 2. Traumatic Pseudotumors 2.1 Morel-Lavallée lesion A Morel-Lavallée lesion represents a closed degloving injury associated with severe trauma, when the skin and subcutaneous fatty tissue abruptly separate from the underlying fascia. Morel-Lavallée lesions most commonly occur over the greater trochanter of the femur, but may be seen over the knee, scapula, or lumbar region as well. The perifascial plane fills with blood and pus, and may form a pseudocapsule, preventing spontaneous resolution. Page 8 of 36

9 These lesions should be treated with surgical evacuation, or in some cases, percutaneous drainage. If left untreated, Morel-Lavallée lesions can become infected and may progress to extensive skin necrosis. The imaging features of a Morel-Lavallée lesion depend on its contents. When purely cystic, the lesion follows fluid signal on MRI. The lesions may be complex appearing due to hemorrhagic clots, with the T1 and T2 characteristics dependent on the age of the hematoma, and may also demonstrate fluid-fluid levels. The key to distinguishing a Morel-Lavallée lesion from malignancy is the antecedent history of trauma and its classic location, dissecting the fascial plane between the subcutaneous fat and the muscle. Figure 4 presents a classic MRI case of a Morel-Lavallee lesion occurring along the fascial plane. Fig. 4: Ultrasound (A) shows a large complex fluid collection over the right thigh. Coronal T2 (B), Coronal PD Fat Sat (C), and Axial T2 Fat Sat (D) show a cystic fluid collection (red arrow) occurring along the fascial plane (green arrow), a classic location for a Morel-Lavallee lesion. Axial T1 Fat Sat Pre (E) and Post Contrast (F) images show the fluid collection demonstrating only peripheral enhancement. References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US Page 9 of 36

10 2.2 Soft Tissue Hematoma Soft tissue hematomas are most commonly seen following trauma, either blunt, penetrating, or iatrogenic, but may also occur secondary to antithrombotic therapy or coagulation disorders. Patients present clinically with a palpable lump, pain, or skin discoloration. Massive hematomas may cause gluteal compartment syndrome. Rarely, a hematoma may continue to expand rather than resolve, mimicking a soft tissue tumor. Findings on imaging that suggest hematoma are heterogeneous signal on T1 and T2 weighted imaging with a peripheral pseudocapsule, which may demonstrate enhancement. Findings that would be concerning for an underlying hemorrhagic tumor include spontaneous bleeding without an antecedent history of trauma, nodular wall, and heterogeneous internal enhancement. Figure 5 presents the imaging findings of a left gluteal/thigh hematoma on MRI. Page 10 of 36

11 Fig. 5: Axial T2 Fat Sat (A and B), Sagittal T2 (E), and Sagittal T1 (D) demonstrating a left gluteal/thigh hematoma (red arrow). Notice the fluid-fluid level (green arrow) and the hemorrhagic clot (blue arrow). References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US Figure 6 presents a companion case of a hematoma extending into the anterolateral upper thigh on CT, MRI, and US. Page 11 of 36

12 Fig. 6: Axial CT (A) of the left thigh demonstrating a geographic region of hypodensity within the vastus lateralis muscle. Ultrasound (B) shows a complex fluid collection with echogenic debris and a fluid-fluid level. Axial T2 FS (C and D), Axial T1 Fat Sat Pre Contrast (E), and Axial T1 Fat Sat Post Contrast (F) showing a vastus lateralis hematoma (red arrow) with a fluid-fluid level (blue arrow). Notice the internal septations (yellow arrow), which enhance on post-contrast images. References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US 2.3 Pelvic avulsion injury Avulsion fractures of the pelvis and hip are common injuries seen in physically active adolescents and young adults, occurring when sudden forceful muscular contraction causes the apophysis attached to the muscular tendon to avulse. Avulsion injuries of the pelvis are classically reported at six sites: Site Muscle Ischial tuberosity (most common) Hamstring muscles Page 12 of 36

13 Anterior Superior Iliac Ppine Sartorius muscle Anterior Inferior Iliac Spine Rectus femoris muscle Iliac Crest Abdominal muscles Greater Trochanter Gluteus medius and minimus muscles Lesser Ttrochanter Iliopsoas muscle Avulsion of the lesser trochanter at the insertion of the iliopsoas muscles is rare but may occur in younger athletes, resulting in severe pain and decreased function. However, in adults, iliopsoas avulsion injuries must be investigated further as these fractures are often pathologic and due to metastatic disease. The diagnosis can be made by X-ray and CT. In the acute phase, avulsion injuries may have a very abnormal appearance on MRI due to muscular and osseous edema, mimicking an aggressive lesion. However, CT and x-ray may reliably demonstrate the classic avulsion injury. Further work-up is only indicated in the case of iliopsoas avulsions due to the high chance of underlying malignancy. Figure 7 shows a case of a chronic post-traumatic avulsion injury of the lesser trochanter on CT. Page 13 of 36

14 Fig. 7: Axial CT in bone (A) and soft tissue (B) windows showing a well-corticated hooklike avulsion fragment (red arrow) arising off of the lesser trochanter. Coronal CT (C) of the same finding. No suspicious lytic lesion seen to suggest a pathologic fracture. References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US 3. Degenerative/stress-induced pseudotumors 3.1 Bursitis Bursae are potential fluid spaces between bony prominences and surrounding soft tissue that function to provide cushioning and decrease friction between the bone/soft-tissue interface. Inflammation of the bursa can be caused by trauma, hematoma, arthritis or infection. Approximately 20 bursae have been described around the pelvis and hip. Any of these sites are a potential for bursitis and can be a cause of hip pain and abnormal findings on MRI. Although a thorough review of the bursae of the pelvis are beyond the scope of this discussion, we present examples of the two most common sites of bursitis, the iliopsoas Page 14 of 36

15 bursa and the greater trochanteric (subgluteus maximus) bursa. The diagnosis of bursitis can be reliably made on MRI with knowledge of the bursal anatomy The iliopsoas bursa is the largest bursa in the body, and lies between the iliopsoas muscle/tendon and the pectineus muscle, just medial to the anterior inferior iliac spine. Figure 8 shows a classic appearance of iliopsoas bursitis. Fig. 8: Coronal T2 (A) and Axial T2 Fat Sat (B and C) showing a lobular simple fluid collection (red arrow) arising between the iliopsoas muscle (yellow arrow) and the pectineus muscle (green arrow). Notice the relationship adjacent to the iliopsoas tendon (yellow circle). References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US The greater trochanteric/subgluteus maximus bursa is located between the gluteus maximus tendon and the greater trochanter. The greater trochanter has 4 facets: the anterior, lateral, posterior, and superoposterior. Greater trochanteric bursae occur along the posterior and lateral facets, and should not extend to the anterior facet. Page 15 of 36

16 Figure 9 shows a greater trochanteric bursitis, confined to the lateral facet. Fig. 9: Coronal T2 Fat Sat (A) and Axial T2 Fat Sat (B) showing a fluid-filled trochanteric bursa, which does not extend beyond the anterior border of the lateral facet (yellow arrow). References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US 3.2 Muscle and tendon tears Muscle and tendon tears are frequently encountered throughout the patient population, including pediatric to elderly patients, and are common complaints of pelvic and lower extremity pain. The rectus femoris muscle is the anterior most muscle of the quadriceps muscle group that is subsequently the most commonly injured. It originates from two tendons, the direct/straight and indirect/reflected tendons, which arise from the anterior inferior iliac spine and superior acetabular ridge and posterolateral aspect of the hip joint capsule respectively. Page 16 of 36

17 Clinically, patients complain of pain at the anterior thigh after forceful kicking, sprinting or jumping. Rectus femoris injury can also occur after repetitive microtrauma and patients may present clinically with a palpable, tender mass. MRI is a useful imaging modality for distinguishing between muscle injury or neoplasm. A muscle tear can be seen as a linear hypointense signal within the muscle on T1 and T2 weighted images. Acute injuries will most commonly demonstrate increased T2 signal distally throughout the muscular body. There may be curvilinear muscle enhancement in the acute phase. If the MRI appearance of acute injury cannot be reliably distinguished from a sarcoma, short-term follow-up imaging can help by showing decreased edema and enhancement. Chronic injury of the rectus femoris may show ill-defined increased T2 signal at the origin of the musculotendinous junction. Figure 10 shows an acute rectus femoris muscle tear on MRI. Fig. 10: Axial T1 Fat Sat Pre Contrast (A) showing a hypointense linear muscle tear (red arrow). On post-contrast T1 images (B), there is surrounding muscular enhancement (green arrow). Axial T2 Fat Sat (C) shows associated muscular edema (yellow arrow). Page 17 of 36

18 References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US Figure 11 shows a companion case of an acute rectus femoris muscle tear on MRI. Fig. 11: Axial T2 Fat Sat (A) and Axial T1 Fat Sat (B) showing a hypointense linear tear (red arrow) of the rectus femoris muscle with surrounding edema (yellow arrow). References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US The gluteus medius muscle, along with the gluteus minimis muscle, is commonly referred to as the "rotator cuff" of the hip as it aids in hip abduction and joint stabilization during walking. The gluteus medius is a large, fan-shaped muscle that inserts on the superoposterior and lateral facets of the greater trochanter, and contributes to the pathology of the "greater trochanteric pain syndrome." Injury to this muscle group is a frequent cause of lateral hip pain that may be exacerbated with walking, climbing stairs and laying on the affected side. Page 18 of 36

19 MRI is a useful imaging modality for diagnosing tear or rupture. Frequently, gluteus medius injury demonstrates tendon elongation or retraction/avulsion and increased T2 signal intensity at the superolateral aspect of the greater trochanter and associated soft tissues and musculature. Chronic injury to the gluteus medius musculature may demonstrate calcification at the tendinous insertions and associated osseous erosion. This often raises concern for a mass in patients with primary malignancy and metastatic osseous lesions when visualized on plain radiograph. However, MRI demonstrates that the calcification is located within the tendon and the osseous findings are consistent with reactive inflammatory change and bone marrow edema. Figure 12 shows an acute gluteus medius tear with underlying calcific tendinitis of the gluteus medius muscle. Fig. 12: Axial T2 Fat Sat (A and B) and Coronal STIR (C) shows an acute tear of the partially retracted gluteus muscle (green arrow) near the musculotendinous junction with surrounding edema (yellow arrow). Coronal T1 (D) shows a focal hypointense lesion (red arrow), which was found on X-ray (E) to represent an area of chronic underlying calcific tendinitis. References: Department of Radiology, Hartford Hospital, Hartford Hospital HARTFORD/US Page 19 of 36

20 Page 20 of 36

21 Images for this section: Fig. 1: Axial (A) and Coronal (B) CT scan showing clusters of soft tissue nodules with surrounding fat stranding in the gluteal subcutaneous fat, which is a classic appearance and location for gluteal silicone injections. Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 21 of 36

22 Fig. 2: Axial STIR with Water Sat (A), Axial T1 (B), Coronal STIR (C), and Coronal T1 (D) showing clusters of soft tissue nodules with surrounding fat stranding in the gluteal subcutaneous fat, which is a classic appearance and location for gluteal silicone injections. The nodules are hyperintense on T2 weighted imaging and, in this example, are isointense to muscle on T1 weighted images. Silicone nodules may have a variable appearance on T1 weighted imaging. Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 22 of 36

23 Fig. 3: Axial Proton Density (A), Coronal Proton Density (B), Sagittal Proton Density (C), and Coronal STIR (D) sequences showing a lobular, slightly complex cystic fluid collection (red arrow) contiguous with the left hip prosthesis (green arrow). Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 23 of 36

24 Fig. 4: Ultrasound (A) shows a large complex fluid collection over the right thigh. Coronal T2 (B), Coronal PD Fat Sat (C), and Axial T2 Fat Sat (D) show a cystic fluid collection (red arrow) occurring along the fascial plane (green arrow), a classic location for a MorelLavallee lesion. Axial T1 Fat Sat Pre (E) and Post Contrast (F) images show the fluid collection demonstrating only peripheral enhancement. Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 24 of 36

25 Fig. 5: Axial T2 Fat Sat (A and B), Sagittal T2 (E), and Sagittal T1 (D) demonstrating a left gluteal/thigh hematoma (red arrow). Notice the fluid-fluid level (green arrow) and the hemorrhagic clot (blue arrow). Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 25 of 36

26 Fig. 6: Axial CT (A) of the left thigh demonstrating a geographic region of hypodensity within the vastus lateralis muscle. Ultrasound (B) shows a complex fluid collection with echogenic debris and a fluid-fluid level. Axial T2 FS (C and D), Axial T1 Fat Sat Pre Contrast (E), and Axial T1 Fat Sat Post Contrast (F) showing a vastus lateralis hematoma (red arrow) with a fluid-fluid level (blue arrow). Notice the internal septations (yellow arrow), which enhance on post-contrast images. Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 26 of 36

27 Fig. 7: Axial CT in bone (A) and soft tissue (B) windows showing a well-corticated hooklike avulsion fragment (red arrow) arising off of the lesser trochanter. Coronal CT (C) of the same finding. No suspicious lytic lesion seen to suggest a pathologic fracture. Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 27 of 36

28 Fig. 8: Coronal T2 (A) and Axial T2 Fat Sat (B and C) showing a lobular simple fluid collection (red arrow) arising between the iliopsoas muscle (yellow arrow) and the pectineus muscle (green arrow). Notice the relationship adjacent to the iliopsoas tendon (yellow circle). Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 28 of 36

29 Fig. 9: Coronal T2 Fat Sat (A) and Axial T2 Fat Sat (B) showing a fluid-filled trochanteric bursa, which does not extend beyond the anterior border of the lateral facet (yellow arrow). Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 29 of 36

30 Fig. 10: Axial T1 Fat Sat Pre Contrast (A) showing a hypointense linear muscle tear (red arrow). On post-contrast T1 images (B), there is surrounding muscular enhancement (green arrow). Axial T2 Fat Sat (C) shows associated muscular edema (yellow arrow). Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 30 of 36

31 Fig. 11: Axial T2 Fat Sat (A) and Axial T1 Fat Sat (B) showing a hypointense linear tear (red arrow) of the rectus femoris muscle with surrounding edema (yellow arrow). Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 31 of 36

32 Fig. 12: Axial T2 Fat Sat (A and B) and Coronal STIR (C) shows an acute tear of the partially retracted gluteus muscle (green arrow) near the musculotendinous junction with surrounding edema (yellow arrow). Coronal T1 (D) shows a focal hypointense lesion (red arrow), which was found on X-ray (E) to represent an area of chronic underlying calcific tendinitis. Department of Radiology, Hartford Hospital, Hartford Hospital - HARTFORD/US Page 32 of 36

33 Conclusion A variety of soft tissue pseudotumors may occur in any of the potential spaces of the hip. These acquired pseudotumors may be post-operative, post-traumatic, or stress-induced. These benign pseudotumors can often be reliably differentiated from malignancy by recognizing the CT and MR characteristics of these entities when taken into account with the patient's history. Page 33 of 36

34 Personal information Mohammed R. Kaleel, M.D., M.Sc., is a PGY 5 Radiology Resident at Hartford Hospital, Hartford, CT. He will begin a Musculoskeletal Imaging fellowship at Stanford University in July Jessica L. Czajka, M.D., is a PGY4 Radiology Resident at Hartford Hospital, Hartford, CT. She will begin a Breast Imaging fellowship at Lahey Clinic in July Michael O'Loughlin, MD, is the Program Director of the Hartford Hospital Diagnostic Radiology Residency program and a Radiologist for Jefferson Radiology. Harpreet Baweja, MD, is the Program Director of the Musculoskeletal Radiology Fellowship program at Jefferson Radiology. He is an attending Radiologist for the Hartford Hospital Radiology Residency Program. Page 34 of 36

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