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Subacromial lipoma causing impingement syndrome of the shoulder: A case report
Subacromial lipoma causing impingement syndrome of the shoulder: A case report Jaikumar Relwani, MS(Orth), DNB(Orth), FRCSG, Wallace Ogufere, FRCS (Tr&Orth), and Sam Orakwe, FRCSEd, FRCS (Tr&Orth), London, England
I
mpingement syndrome is usually caused by encroachment of the rotator cuff by the acromion, coracoacromial ligament, acromioclavicular joint, or coracoid process. Iatrogenic causes such as sutures, pins, or wires left from previous surgery can cause the same symptoms. We present a case with classic signs of impingement and possible cuff tear in which the magnetic resonance imaging (MRI) results were reported as normal but the patient in fact had a subacromial lipoma causing an impingement syndrome of the shoulder. The case is the first such reported to our knowledge. We would like to introduce this as an unusual cause of impingement and also present the MRI findings of such a lesion.
CASE REPORT A 52-year-old woman presented to our shoulder unit with gradually progressive pain and restricted motion in the right shoulder of 18 months’ duration. The pain was present mainly on overhead movement and abduction. She also complained of a feeling of stiffness in the shoulder. There was no palpable swelling around the shoulder. She had a painful arc between 50° and 120°, with a positive Neer sign and positive Neer impingement test result. Examination of the cuff strength revealed mild weakness of the supraspinatus, with no signs of shoulder instability. Radiographs of the shoulder were normal. The patient was treated conservatively with subacromial local anesthetic and steroid injections, oral nonsteroidal anti-inflammatory drugs, and physiotherapy for 4 months without relief. After conservative treatment had failed, she underwent an MRI examination, the findings of which were reported as normal except for a deformity of the lesser tuberosity related to an old fracture. However, in view of the persistent symptoms, the diagnosis of impingement with a cuff tear was still entertained, and we decided to perform an open subacromial decompression and repair of the cuff. From the Department of Trauma and Orthopaedics, Lewisham University Hospital. Reprint requests: Jaikumar Relwani, MS (Orth), DNB (Orth), FRCSG, Specialist Registrar in Trauma and Orthopaedics, Lewisham University Hospital, Lewisham High Street, London SE13 6LH. (E-mail: [email protected]). J Shoulder Elbow Surg 2003;12:202-3. Copyright © 2003 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2003/$35.00 ⫹ 0 doi:10.1067/mse.2003.45
202
Figure 1 Axial T2-weighted magnetic resonance image showing a well-circumscribed homogenous swelling (arrows) with signal intensity resembling that of subcutaneous fat.
At surgery, through a midacromial approach, a soft lipomatous swelling measuring 5 ⫻ 4 ⫻ 4 cm was found in the anterior subacromial space. This was the offending lesion and was clearly reducing the size of the rotator interval. The swelling was impinging upon and displacing the tendon of the biceps as well. It was completely excised. There was no associated rotator cuff tear. A histopathologic examination confirmed a simple lipoma. Postoperatively, the patient recovered completely with physical therapy at 3 months. She remains asymptomatic at 12 months after surgery. In a retrospective review, the MRI films did show the lesion as a homogenous, well-circumscribed mass extending from the tendon of the biceps anteriorly to the greater tuberosity laterally and superiorly to the subacromial space. The lesion was homogenous on both T2-weighted (Figure 1) and T1-weighted (Figure 2) MRI images. There was no infiltration of the surrounding muscle or the cuff.
Relwani, Ogufere, and Orakwe
J Shoulder Elbow Surg Volume 12, Number 2
203
lesion. The lipoma had been clearly visible and would probably have been detected had we been aware of the condition. A literature review showed that this is the first such report of a lipoma in the subacromial space causing impingement syndrome. The lesion was homogenous on both T1- and T2-weighted MRI images. A STIR sequence for such a lesion has been recommended to differentiate it from a liposarcoma.8 Simple lipomas show complete suppression at T2 STIR, whereas liposarcomas show mild to moderate heterogeneity at T1/T2 and fail to show complete suppression at T2 STIR.8 Gadolinium-enhanced MRI also may be useful, especially in selecting a biopsy site for such lesions.1 Thus, a subacromial lipoma, although extremely rare, can cause subacromial impingement. This case also demonstrates that MRI can be very accurate in detecting unusual lesions. REFERENCES
Figure 2 T1-weighted oblique coronal magnetic resonance image showing a homogenous lesion (arrows) overlying the cuff insertion.
DISCUSSION Rotator cuff impingement symptoms usually arise from pathologic shoulder lesions related to instability or extrinsic factors involving the coracoacromial arch.3,5,8 Bursal causes are less common and include thickening from rheumatoid arthritis and iatrogenic causes such as sutures or implants from previous surgery.5 Rare causes reported comprise coracoid impingement,3 synovial chondromatosis,1,2 clavicular malunion,7 unstable os acromiale,12 ossification of the subscapularis tendon,9 and tumors such as osteochondroma of the distal clavicle.10 Certain lesions may mimic impingement such as cervical spondylosis, a thoracic disk herniation,11 or tumors of the proximal humerus.4,6 Our patient had a lipoma of the subacromial space that presented as impingement with a weak rotator cuff. The lesion was originally not recognized on MRI and was only detected intraoperatively. As the lesion had a signal intensity similar to that of bone marrow, it was reported as a possible malunited fracture on the magnetic resonance images by 2 radiologists, but on review of the images, a clear zone was identifiable between the humerus and the
1. De Ferm A, Lagae K, Bunker T. Synovial osteochondromatosis: an unusual cause for subacromial impingement. Acta Orthop Belg 1997;63:218-20. 2. Demirhan M, Eralp L, Atalar AC. Synovial chondromatosis of the subcoracoid bursa. Int Orthop 1999;23:358-60. 3. Ferrick MR. Coracoid impingement. A case report and review of the literature. Am J Sports Med 2000;28:117-9. 4. Kaempffe FA. Neoplasm as a cause of shoulder pain. J Fam Pract 1995;40:480-5. 5. Kelty C, Stamer J, Irwin LR, Limb D. Subacromial impingement due to the locking bolt of a humeral nail. Orthopaedics 2000;23: 1200. 6. Marin R, Papierski P. Unusual presentation of an osteoid osteoma. Mil Med 1996;161:438-40. 7. Naert PA, Chipchase LS, Krishnan J. Clavicular malunion with consequent impingement syndrome. J Shoulder Elbow Surg 1998;7:548-50. 8. Pang AK, Hughes T. Magnetic resonance imaging of lipoma and liposarcoma: potential of short tau inversion recovery as a technique of fat suppression. Australas Radiol 2000;44:412-6. 9. Peidro L, Serra A, Suso S. Subcoracoid impingement after ossification of the subscapularis tendon. J Shoulder Elbow Surg 1999; 8:170-1. 10. Reichmister J, Reeder JD, Gold DL. Osteochondroma of the distal clavicle: an unusual cause of rotator cuff impingement. Am J Orthop 2000;29:807-9. 11. Wilke A, Wolf U, Lageard P, Griss P. Thoracic disc herniation: a diagnostic challenge. Man Ther 2000;5:181-4. 12. Wright RW, Heller MA, Quick DC, Buss DD. Arthroscopic decompression for impingement syndrome secondary to an unstable os acromiale. Arthroscopy 2000;16:595-9.
I
mpingement syndrome is usually caused by encroachment of the rotator cuff by the acromion, coracoacromial ligament, acromioclavicular joint, or coracoid process. Iatrogenic causes such as sutures, pins, or wires left from previous surgery can cause the same symptoms. We present a case with classic signs of impingement and possible cuff tear in which the magnetic resonance imaging (MRI) results were reported as normal but the patient in fact had a subacromial lipoma causing an impingement syndrome of the shoulder. The case is the first such reported to our knowledge. We would like to introduce this as an unusual cause of impingement and also present the MRI findings of such a lesion.
CASE REPORT A 52-year-old woman presented to our shoulder unit with gradually progressive pain and restricted motion in the right shoulder of 18 months’ duration. The pain was present mainly on overhead movement and abduction. She also complained of a feeling of stiffness in the shoulder. There was no palpable swelling around the shoulder. She had a painful arc between 50° and 120°, with a positive Neer sign and positive Neer impingement test result. Examination of the cuff strength revealed mild weakness of the supraspinatus, with no signs of shoulder instability. Radiographs of the shoulder were normal. The patient was treated conservatively with subacromial local anesthetic and steroid injections, oral nonsteroidal anti-inflammatory drugs, and physiotherapy for 4 months without relief. After conservative treatment had failed, she underwent an MRI examination, the findings of which were reported as normal except for a deformity of the lesser tuberosity related to an old fracture. However, in view of the persistent symptoms, the diagnosis of impingement with a cuff tear was still entertained, and we decided to perform an open subacromial decompression and repair of the cuff. From the Department of Trauma and Orthopaedics, Lewisham University Hospital. Reprint requests: Jaikumar Relwani, MS (Orth), DNB (Orth), FRCSG, Specialist Registrar in Trauma and Orthopaedics, Lewisham University Hospital, Lewisham High Street, London SE13 6LH. (E-mail: [email protected]). J Shoulder Elbow Surg 2003;12:202-3. Copyright © 2003 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2003/$35.00 ⫹ 0 doi:10.1067/mse.2003.45
202
Figure 1 Axial T2-weighted magnetic resonance image showing a well-circumscribed homogenous swelling (arrows) with signal intensity resembling that of subcutaneous fat.
At surgery, through a midacromial approach, a soft lipomatous swelling measuring 5 ⫻ 4 ⫻ 4 cm was found in the anterior subacromial space. This was the offending lesion and was clearly reducing the size of the rotator interval. The swelling was impinging upon and displacing the tendon of the biceps as well. It was completely excised. There was no associated rotator cuff tear. A histopathologic examination confirmed a simple lipoma. Postoperatively, the patient recovered completely with physical therapy at 3 months. She remains asymptomatic at 12 months after surgery. In a retrospective review, the MRI films did show the lesion as a homogenous, well-circumscribed mass extending from the tendon of the biceps anteriorly to the greater tuberosity laterally and superiorly to the subacromial space. The lesion was homogenous on both T2-weighted (Figure 1) and T1-weighted (Figure 2) MRI images. There was no infiltration of the surrounding muscle or the cuff.
Relwani, Ogufere, and Orakwe
J Shoulder Elbow Surg Volume 12, Number 2
203
lesion. The lipoma had been clearly visible and would probably have been detected had we been aware of the condition. A literature review showed that this is the first such report of a lipoma in the subacromial space causing impingement syndrome. The lesion was homogenous on both T1- and T2-weighted MRI images. A STIR sequence for such a lesion has been recommended to differentiate it from a liposarcoma.8 Simple lipomas show complete suppression at T2 STIR, whereas liposarcomas show mild to moderate heterogeneity at T1/T2 and fail to show complete suppression at T2 STIR.8 Gadolinium-enhanced MRI also may be useful, especially in selecting a biopsy site for such lesions.1 Thus, a subacromial lipoma, although extremely rare, can cause subacromial impingement. This case also demonstrates that MRI can be very accurate in detecting unusual lesions. REFERENCES
Figure 2 T1-weighted oblique coronal magnetic resonance image showing a homogenous lesion (arrows) overlying the cuff insertion.
DISCUSSION Rotator cuff impingement symptoms usually arise from pathologic shoulder lesions related to instability or extrinsic factors involving the coracoacromial arch.3,5,8 Bursal causes are less common and include thickening from rheumatoid arthritis and iatrogenic causes such as sutures or implants from previous surgery.5 Rare causes reported comprise coracoid impingement,3 synovial chondromatosis,1,2 clavicular malunion,7 unstable os acromiale,12 ossification of the subscapularis tendon,9 and tumors such as osteochondroma of the distal clavicle.10 Certain lesions may mimic impingement such as cervical spondylosis, a thoracic disk herniation,11 or tumors of the proximal humerus.4,6 Our patient had a lipoma of the subacromial space that presented as impingement with a weak rotator cuff. The lesion was originally not recognized on MRI and was only detected intraoperatively. As the lesion had a signal intensity similar to that of bone marrow, it was reported as a possible malunited fracture on the magnetic resonance images by 2 radiologists, but on review of the images, a clear zone was identifiable between the humerus and the
1. De Ferm A, Lagae K, Bunker T. Synovial osteochondromatosis: an unusual cause for subacromial impingement. Acta Orthop Belg 1997;63:218-20. 2. Demirhan M, Eralp L, Atalar AC. Synovial chondromatosis of the subcoracoid bursa. Int Orthop 1999;23:358-60. 3. Ferrick MR. Coracoid impingement. A case report and review of the literature. Am J Sports Med 2000;28:117-9. 4. Kaempffe FA. Neoplasm as a cause of shoulder pain. J Fam Pract 1995;40:480-5. 5. Kelty C, Stamer J, Irwin LR, Limb D. Subacromial impingement due to the locking bolt of a humeral nail. Orthopaedics 2000;23: 1200. 6. Marin R, Papierski P. Unusual presentation of an osteoid osteoma. Mil Med 1996;161:438-40. 7. Naert PA, Chipchase LS, Krishnan J. Clavicular malunion with consequent impingement syndrome. J Shoulder Elbow Surg 1998;7:548-50. 8. Pang AK, Hughes T. Magnetic resonance imaging of lipoma and liposarcoma: potential of short tau inversion recovery as a technique of fat suppression. Australas Radiol 2000;44:412-6. 9. Peidro L, Serra A, Suso S. Subcoracoid impingement after ossification of the subscapularis tendon. J Shoulder Elbow Surg 1999; 8:170-1. 10. Reichmister J, Reeder JD, Gold DL. Osteochondroma of the distal clavicle: an unusual cause of rotator cuff impingement. Am J Orthop 2000;29:807-9. 11. Wilke A, Wolf U, Lageard P, Griss P. Thoracic disc herniation: a diagnostic challenge. Man Ther 2000;5:181-4. 12. Wright RW, Heller MA, Quick DC, Buss DD. Arthroscopic decompression for impingement syndrome secondary to an unstable os acromiale. Arthroscopy 2000;16:595-9.