Dr. Knight differentiates the sacro-iliac lipoma from the pannicular hernia of the sacro-iliac area. Both are also known by the term back mice.
He says that the sacro-iliac lipoma has been known to be a cause of backache for a long time, but their significance has not been emphasized, since in many cases the diagnosis hasn‘t been made if the nodule was not palpated.
He differentiates the sacro-iliac lipoma from the pannicular hernia (due to fat herniation through the lumbodorsal fascia). After his personal experience, he thinks that the presence of the lipoma in all the 7 patients was the causative agent. He found a concomitant pannicular hernia to the lipoma in just 3 cases. He says that, on his opinion, the fat protruding through the fascia was just a coincidental finding.
He made a remark that sometimes the nodule can NOT be PALPATED, instead there is a kind of “tender thickening“. Nevertheless, if the local anesthetic injection relieves the pain, Dr. Knight considers that it is a sign of a deep, not easily palpable sacro-iliac lipoma and recommends surgical excision if necessary.
HE DOES NOT make any reference to the possible etiopathogenic explanations.
He just mentions Ficarra and McLaughlin’s article from 1952.
Notes on the article:
Sacro-iliac lipoma versus pannicular hernia
C. Knight, M. D.
Knight starts saying:
“Low back pain may at times be a difficult diagnostic problem“.
Physicians often “shrink“ from patients with a recurrent history of backache.
These patients usually have been to many doctors and often resorted to chiropractors or osteopaths. That’s why physicians sometimes consider this type of patient as neurotic.
The author admits that the number of cases of sacro-iliac lipoma is still limited because he had little time, but if it would not be by a member of his own family that had suffered from this entity, he would be missing even more cases.
He mentions that Ficarra and McLaughlin ONLY found 2 references to herniation of fat through the lumbodorsal fascia (one case associated with lipomas).
He saw 7 cases of sacro-iliac lipoma in a period of 6 months (3 cases were associated to pannicular hernias).
His cases were mainly women (6 vs 1). Age ranging from 20 to 56 years. Pain symptoms from few months to 15 years.
Symptomatology of the sacro-iliac lipoma
All cases presented with a history of backache that was aggravated by motion (specially on forward bending). The pain would typically radiate to the lateral side of the leg. Lying on the back could increase the pain. Some patients got relief from a corset and others refer that the corset would aggravate the symptoms.
Some patients explain specific movements associated with pain, such as to tie his own shoe.
Most of the patients stated that the pain WOULD LAST SEVERAL DAYS at a time, and then they would be free of pain for several days.
Pain description: as nagging ache or acute as stooping over to pick up an object from the floor.
There was not significant history of trauma.
Examination of the sacro-iliac lipoma
-All patients show good general state.
-Of course, Knight warns that a general examination is necessary to do a proper differentiating diagnosis.
-He mentions that if the novocaine local block relieves the pain, some X-ray findings may be irrelevant in the diagnosis.
-The two main factors are:
1-Finding a nodule or mass or masses
2-The relief of pain by novocaine block
The palpation of masses can differ from each person:
-Some patients have distinct nodules that are easily palpated and rolled under one‘s finger.
-Some patients do not have palpable nodules but, instead, they show a noticeable thickness of the subcutaneous tissue in the affected side as compared from the unaffected one.
Sometimes this inability to feel a clear nodule makes the diagnosis of lipoma questionable, but if then there is a clear relief of pain by novocaine injection, the patient can be operated on and the lipoma WILL BE FOUND and removed with complete relief.
The relief of pain by novocaine block is the definitive diagnostic procedure. And Dr. Knight based HIS PROGNOSIS on the result of the block.
If he felt a NODULE or THICKNESS on the side causing pain, he injected the local anesthetic.
He found 50% of the patients to have BILATERAL LIPOMATA.
They are usually located two inches (5 cm) lateral to the midline on the line extending out between the 4rth and 5th spinous proces of the lumbar vertebrae.
Knight injects 8-10 cc of one or 2 % novocaine down to the bone. He administrates a barbiture 1 1/2 hours before injection.
A few minutes after injection, he asks the patient to get up and go through all motions that had previously caused pain. If there is a clear relief, Dr. Knight advises the patient to undergo surgical removal. With 50% of relief he advises surgery.
CASE HISTORIES about sacro-iliac lipoma
CASE 1: Woman, 56-year-old. She complained of pain on the left side of her back and left lateral thigh. She had this recurrent pain for 18 months, it was becoming worse.
In April 1952, Dr. Knight diagnosed her malady as a fascitis with arthitis.
X-ray revealed a marked straightening of the entire lumbar spine with an arthritic spur on the anterior superior surface of L4, with normal disc spaces. There was some arthtritic degeneration on the left sacroiliac articulation. He advised her a corset and a bed board, but pains continued to recur. Examination showed an obese white female, not acutely ill but suffering from pain. Everything was normal except a WALNUT-SIZED LIPOMA in the left sacro-iliac region and a small lipoma in the right. She had ALMOST COMPLETE RELIEF after 1 hour of administration of novocaine. He advised her surgical removal.
On operation he removed a one-inch diameter lipoma from the area of the left sacro-iliac joint. About 1 to 1-1/2 inches lateral to the lipoma, there was an OPENING in the fascia through which FAT was protruding and which admitted the end of the doctor’s finger. He closed the opening with chromic.
There was another opening one-inch long and 3/4 inches wide with a thin strip of tissue between the openings, and the other being an oval opening.
The patient was discharged on the third day with an uneventful convalescence. After 6 weeks she kept free of pain.
CASE 2: Woman, 20-year-old. She complained of pain on the left side of her back for 3-4 months. She spent 10 days in hospital with backache without relief. The onset was gradual and there was no injury. The pain could radiate anteriorly and would occasionaly hurt on coughing. On the left side, she had no distinct mass but a DEFINITE THICKNESS and moderate tenderness. Pain was completely gone after 8 cc of novocaine. A WALNUT-SIZED LIPOMA was removed. NO HERNIA WAS FOUND. Patient remained free of pain after 6 weeks after operation.
CASE 3: Man, 41-year-old. Pain on the right side of his back for 2 years. PAIN was aggravated by lying on his back, sitting, bending, lifting or crossing his legs. There was an AREA OF THICKNESS 2 inches from the midline at level of 5th vertebra. He had complete relief with novocaine block. They removed a LIPOMA and found a DOUBLE-OPENING hernia where fatty tissue was protruding.
Published in July 2018 by By Marta Cañis Parera
- KNIGHT EC. Sacro-iliac lipoma versus panicular hernia. J Iowa State Med Soc. 1954 Feb;44(2):62-3. PubMed PMID: 13118264.
- FICARRA BJ, MCLAUGHLIN WJ. Low back pain due to pannicular hernias; report of a case. J Am Med Assoc. 1952 Nov 1;150(9):855. PubMed PMID: 12990314.