1935 Sutro

These article titled Subcutaneous fatty nodes in the sacroiliac area from Chrales Sutro it is one of the first medical articles that studied the nodules also known as back mice or back mouse.

Sutro didn’t reach clear conclusions about the etiopathogenic role of theses intriguing fatty nodes.

He did NOT find the same histological findings than Stockman.

Notes on the article of:

Sutro, C. J.

Subcutaneous Fatty Nodes in the Sacroiliac Area.

Am J Med Sci 1935; 190: 833-837.

Hospital for Joint Diseases, New York City.

Charles J. Sutro, M. D. was an orthopedic surgeon born in 1906 in New York.

Sutro is intrigued by Stockman’s work and the presence of tender nodules

Sutro, intrigued by Stockman’s work and the presence of the tender nodes in so many patients with low back pain, tried to do a research to confirm Stockman’s findings. Nevertheless, he didn’t manage. He operated on 4 patients, three of them with an active infection. In all cases he just found “NORMAL FATTY TISSUE”. He seemed puzzled by these results. He emphasized that the fatty lobules had an exquisite tenderness sometimes and that they had a thin capsule. He hypothesized that they could be a cause of pain and that they may have a protective role to protect the bony parts of the back.

He gave an extended bibliography.

Sutro’s investigation results

fatty nodes

-Sutro studied 170 unselected hospital patients.

-They found subcutaneous nodes in the sacroiliac region in 94 cases.

-45/170 were unilateral, and 49/170 were bilateral.

-From 2 to 60 years.

Nodules were also noted in thin persons.

-Incidence was higher in “stout women past middle ages”.

-33/170 had low back pain, 16/33 had tender subcutaneous nodules.

Following Stockman’s work, he decided to do a biopsy to certain patients

Since Stockman’s work suggested that inflammatory changes in the subcutaneous fat might be the cause of some pain symptoms, he tried to find those results.

They removed surgically the tender nodules in 4 patients.

  • Case 1: Woman, 50 years old. Low back pain for months. It sometimes radiated to posterior aspect of the right leg. Bilateral group of subcutaneous nodules could be palpated in the sacroiliac region (clumps of 6 to 8 nodes). Free movable under the skin. Sized from a pea to an almond. Consistency of a soft rubber. Those on the right side were much tender.

Previous to operation the nodes were considered to be: lipomas, neurolipomas, located rheumatoid nodules, MYOGELOSES (INDURATIONS OF VOLUNTARY MUSCLES, Lange believes them to be the result of local chemical disturbances).

They operated on the woman. They removed 6 nodes. They were LOBULES OF FAT, each covered with a thin capsule. Histology showed normal adipose tissue. No inflammatory changes were found. After the operation the woman was free from pain for at least 3 months.

Sutro wondered “how come” the nodes could be related to low back pain. Since the macroscopic and microscopic examination was reported as normal fat, this didn’t correlate with Stockman’s work.

That’s why they decided to remove nodes from patients with an obvious focus of infection.

  • Case 2: Male, 26 years old. He had “tuberculosis of the left astragalus” for 3 years. He had the presence of 2 tender pea-sized nodules bilateral over the sacroiliac areas. He never had low back pain. They removed surgically A CLUSTER OF SMALL NODULES over the left sacroiliac joint. They were enclosed in DELICATE CAPSULES (that showed the presence of small arterioles). Histologically, they found nothing apart from adipose tissue.
  • Case 3: Male, 42 years old. Back pain for 8 years. He had advanced pyorrhea. Lumbar tender nodes were palpated, freely movable under the skin. The nodes were removed and showed fat lobules enclosed in thin capsules with a COMPLETE ABSENCE OF ANY INFLAMMATORY changes. The back pain persisted, but the area where they removed the nodes was no longer painful.
  • Case 4: Colored woman. Recent sacroiliac region pain. She had past history of repeated sore throat. Tenderness on the LEFT sacroiliac region. There were clusters of nodes bilaterally, on the left markedly tender. Nodes were removed under local anesthesia. The microscopic examination showed normal adult fatty tissue. Pain stayed after operation.

fatty nodes Sutro

Sutro’s final thoughts

-The microscopic examinations showed normal fatty tissue disposed in LOBULES (no evidence of any inflammatory abnormality). Enclosed in delicate capsules.

-It seems that the subcutaneous nodules are probably protective or buffer pads over some of the poorly muscle-covered areas of the sacrum and ilium.

-Tenderness, sometimes of exquisite degree, may be attributed to the mere presence of these subcutaneous fat nodules and not to the joints.

-It can be differentiated from Dercum’s in the differential diagnosis.

Published in April 2018 By Marta Cañis Parera ORCID iD icon


Sutro, C. J. Subcutaneous Fatty Nodes in the Sacroiliac Area. Am J Med Sci 1935; 190: 833-837.

Stockman, R. The Clinical Symptoms and Treatment of Chronic Subcutaneous FibrosisBritish Medical Journal. 1911; 1(2616): 352-355.

Stockman. A Discussion on Fibrositis. Proc R Soc Med. 1913; 6 (Balneol Climatol Sect): 36-9. PubMed PMID: 19976474; PubMed Central PMCID: PMC2006735