Dynamic chiropractic
september 4, 2000, volume 18, issue 19
low back pain and episacral lipomas
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by david bond,dc
a cause of low back pain and disability often overlooked by practitioners who treat patients suffering from acute and chronic musculoskeletal complaints is the episacral lipoma. Although usually thought of as a minor condition, it is capable of producing considerable low back pain.
First described by ries in 1937,1 episacral lipomas are small, tender, "tumor-like" nodules occurring mainly over the sacroiliac region which can cause disabling low back pain. The term "lipoma" is descriptive only in that through direct palpation over the region, the examiner is able to detect a subcutaneous mass similar to the benign tumors; however, it is not a tumor, but is subfascial fat which has herniated through the overlying fascial layer.
Perhaps a better term is that of the lumbar fat herniation as described in 1944 by copeman and ackerman.2 in their research, they reported 10 cases of severe and disabling low back pain in which they identified the fatty tumors as the principle cause of the patient's complaints. They subsequently excised the herniation, which produced striking relief of the pain. In 1945, hertz reported the cases of six women with excruciating low back pain.3 all of the women had a history of a traumatic strain prior to its occurrence of, which was sometimes accompanied by unilateral leg pain. The low back pain in all six women was dramatically relieved by the removal of a herniated fat tumor.
In a followup study by copeman and ackerman, 11 new cases were described.4 in all 11 patients, a biopsy confirmed the presence of edematous fat lobules herniating through deficiencies of the fibrous compartments. It was felt that the pain was produced in the fibro-fatty tissue and not in the musculature itself.
Hucherson and gandy reported in 1948 that of 32 patients who had undergone surgical removal of the lipoma, only two patients failed to experience relief of pain.5 many other researchers have reported that in patients with backaches and occurrence of the nodules, relief was obtained immediately by injection of a local anesthetic and some by operation. At times, dramatic relief was obtained, and there was no recurrence of pain over time.6,7,8,9 in a study by singewald,10 1,000 persons were evaluated for lipomas. They were found in 16% of the subjects; however, only 10% had reported back pain. Therefore, it is not an uncommon finding in the general population, although it is usually asymptomatic.
Fat herniations occur in predictable sites along the edge of the sacrospinalis muscle just above the iliac crest, very close to the natural "dimple" in the sacroiliac area.10 in this area, through abnormal tension, trauma, or by inherent weaknesses of the fascia, as well as through foramina for cutaneous nerves, the underlying fat pad may herniate through the fibrous tissue between the superficial and deep layers. Copeman and ackerman4 mapped the basic fat pattern of the lumbar region from 14 cadaver studies with reference to the most common sites for the occurrence of fat herniations, which were felt to be extremely corresponding. The researchers reported that during dissections, it was not uncommon to find the fascia to be of non-uniform thickness. They also found actual deficiencies of the fascia in which underlying fat tended to bulge through.
In addition, they were able to describe three basic types of herniations: pedunculated, nonpedunculated and foraminal. The nonpedunculated hernia appears as a tense swollen nodule, which protrudes frequently along the iliac crest. Pedunculated hernias have the appearance of a strangulated polyp through the fascia connected by a fibrous pedicle. In the foraminal type, the fat herniates through the foramina containing the cutaneous branches of the posterior rami of the first three lumbar nerves as they pierce the deep fascia after leaving the body of the muscle. A horizontal fold of membrane acts as a valve that prevents the herniation from occurring during flexion of the back; however, a failure to function normally may result in a herniation. Of the three, the nonpedunculated herniation appears to be the most common. Biopsy of the specimens revealed that they were composed entirely of normal adipose tissue with some edema present. In some cases, there was evidence of patches of fibrous tissue growing in the fatty tissue and others with nerve tissue present; however, this has not been a consistent finding. From a clinical standpoint, the mechanism of pain is not fully understood; however, pain appears to be the primary feature, which seems to be due to the expansion of the fat herniation in the otherwise unyielding fibrous capsule, in that removal of the lipoma alleviates the pain.
The pain pattern of the fat herniation originates in a focal region; however, it may radiate in an ill-defined distribution and may be variable in intensity and duration.9 upon palpation, the patient is usually able to describe the exact point of extreme, or pinpoint, tenderness. It is different from a trigger point as described by travell13 in that the examiner can palpate a definite mass rather than a taut band of skeletal muscle. However, like a myofascial trigger point, firm pressure may produce pain that radiates in a general and segmental distribution.11
depending upon the severity of the pain, there may be a restriction of the lumbar range of motion, and the pain may increase with positioning.9 there may well be a significant degree of paraspinal muscle spasming which may also be related to the referred pain, as well as the nature of the original incident.2 no specific structural abnormality of the spine has been identified. Nerve root traction tests are usually normal, with a production of primarily low back and sacral pain upon testing, unless there is a concomitant disc herniation.8 reports of pain radiating down the side affected with the lipoma are frequent; however, there is no uniformity of the radiation area.5 diagnosis is usually confirmed by the injection of local anesthetic, which significantly alleviates the pain, at least temporarily.12
