This is a relevant article about subfascial fat herniation (also known as back mice or mouse) from 1946. Ralph Herz presents his personal anatomical observations from the dissecting room (his findings were essentially the same as Copeman and Ackerman reported) and he studied 109 medical cases related to subfascial fat herniation and low back pain.
Notes on the article:
Herniation of subfascial fat as a cause of low back pain; report of 37 cases treated surgically.
Ann Rheum Dis. 1946 Dec; 5(6):201-3.
PubMed PMID: 20242353
In this short article, Ralph Herz presented anatomic evidence that the nodules that can be palpated in some backs are due to herniation of subfascial fat through de deep layer of the superficial fascia (subfascial fat herniation). The relief from the pain can be obtained by anaesthetic injection or by surgical removal. He studied 109 cases related to this entity.
He concludes that this clinical entity is common, and its recognition is simple. The presence of a painful nodule, with disappearance of pain after injection with anaesthetic solution, is diagnostic. Surgical treatment in these cases results in continuous relief of severe back pain.
Previous studies (1945): 6 cases. And current study (1946): 37 cases more
In 1945 Herz did a study where he reported 6 cases of low back pain in women relieved by excision of herniated fat. In the current study he presents 37 surgical cases aiming to show that subfascial fat herniation is a causative agent in producing low back pain.
Puzzled by little literature about subfascial fat herniation (or back mice)
First of all, the author is puzzled not to find other clinical reports on relief of back pain by removal of a herniation of subfascial fat in literature, except for the work of Sutro (1935) and Copeman and Ackerman (1944). He theorized it could be because other papers may have been published under varying titles.
Personal observations in the dissection room that showed subfascial fat herniation
He carried out dissection of several cadavers (his findings were essentially the same as Copeman and Ackerman reported)
-In a cachectic specimen the fascies were more easily delineated, and the basic fat consisted of a very thin layer.
-In a normal specimen, fat pads were considerably thicker, and the fascias less easily defined, with considerable variation in thickness and more numerous weak points.
-Incision of the deep layer of the superficial fascia revealed a large fat pad (laying over gluteal region 3 cm below the crest of the ilium and about 3 cm from the spine or midline, which extended below the level of the posterior superior spine of the ilium, and measured roughly 10x15cm).
-In all specimens the deep layer of the superficial fascia had several weak areas, though, where this fat could be very easily forced into the space between the two layers of superficial fascia.
Between October, 1943, and February, 1946, he observed 109 cases of this syndrome. Operation was performed in 37, with 34 patients with complete relief.
The typical story in these cases was that trauma resulting from a physical strain initiated the back pain often referred down one leg. Some patients explain recurrent attacks of such pain for many years. IN ALL CASES A DEFINITE NODULE WAS PALPABLE; this was extremely tender, and pressure on it intensified the pain. The crucial point was the relief of pain and muscle spasm after injection with anaesthetic solution.
- CASE 1. Man 29yrs with severe pain in the lower back radiating down the left leg. Past history of trauma 15 months earlier. Leg pain with numbness had become so severe that he had had little rest or sleep. Previous neurological examination revealed burning and hyperalgesia in L4 distribution. Slight atrophy of left thigh and decreased left patellar reflexes. He had a clinical diagnosis of L3-L4 protruded disc, however operation was deferred because of evidence was not conclusive. At the moment of a second examination, the author was called into consultation, and palpated two painful nodules in the left gluteal region. After injection of 3cc of 2% procaine, the pain abated. A diagnosis of multiple fascial fat herniations in left gluteal area was made. Operation was done with the patient symptom-free 4 months after operation.
- CASE 2. Woman 48yrs with severe, intermittent back pain since a fall thirty years earlier. Previously, she had unsuccessfully undergone a hysterectomy in an attempt to obtain relief from back pain. A palpable painful node was found in the left gluteal area. Pain relief followed an injection of 5cc of 1.5% metycaine. A second injection a few weeks later also produced a temporary relief. Back pain disappeared 6 moths after operation.
Surgical problems to identify nodules
-Difficult if abundant fatty tissue (i.e. overweight). Specially if there is considerable superficial fatty tissue it has not been possible to see a definite mass that could be clearly differentiated as a palpable nodule.
–Sometimes it is a lobulated mass, instead of a definite nodule. In these cases, a wide dissection of fat is made down to the gluteus maximus muscle. If after scission of the mass, a weak point of the fascial layer is found, this is sutured.
It consists of mature adipose tissue, sometimes definitely lobulated. Sometimes it has a pedicle (probably the result of long-lasting strangulation). The mature homogeneous fat is often supported by strands of separately cellular, collagenous connective tissue. Some appeared oedematous and hyperaemic (infiltrated with exudative cells, lymphocytes) and the others did not. One case presented nerve tissue in the fat lobule.
The role of trauma
It seems that the lesions could be present to some people without causing symptoms. Trauma could initiate the symptoms by oedema and hemorrhage. Some could have spontaneous relief or after massage therapy. Others could become chronic and develop fibrous tissue in fatty mass.
Published in March 2018 by Marta Cañis Parera
- Herz R. Herniation of subfascial fat as a cause of low back pain; report of 37 cases treated surgically. Ann Rheum Dis. 1946 Dec;5(6):201-3. PubMed PMID: 20242353.
- Copeman, W.S.C. and Ackerman, W. (1944) . Quart.J.Med. 13,37.
- Sutro CJ. Subcutaneous fatty nodes in the sacroiliac area. Am J Med Sci 1935; 190:833-837.