BACKGROUND: Few useful interventions exist for patients with persistant low back pain. We suggest that a fibro-fatty nodule (“back mouse”) may be an identifiable and treatable cause of this and other types of pain.
METHODS: We describe 2 patients with painful nodules in the lower back and lateral iliac crest areas. In both cases, the signs and symptoms were unusual and presented at locations distant from the nodule. One patient complained of severe acute lower abdominal pain, and the other had been treated for chronic recurrent trochanteric bursitis for several years.
RESULTS: In both patients, symptoms appeared to be relieved by multiple injection of the nodule.
DISCUSSION: There is agreement that back mice exist. Referred pain from the nodules might explain the distant symptoms and signs in these cases. Multiple puncture may be an effective treatment because it lessens the tension of a fibro-fatty nodule.
CONCLUSIONS: Randomized trials on this subject are needed. In the meantime, physicians should keep back mice in mind when presented with atypical and unaccountable symptoms in the lower abdomen, inguinal region, or legs.
A part from symptoms caused by vertebral disk injury, the scientific evidence for the specific causation and effective treatment of low back problems is relatively weak. Clinicians who wish to adhere to evidence-based practice when treating persistent low back pain are faced with a limited number of useful interventions: short-term therapy with muscle relaxants and analgesics, and encouragement to return to daily routines as quickly as possible.1-3
Though doubt has been cast on the real existence of subtypes or syndromes of low back pain, our clinical observation and experience suggest that a fibro-fatty nodule (“back mouse”) may be an identifiable and remediable cause of acute or chronic low back pain.4,5 Given the extent of the costs and suffering caused by low back pain, effective therapy for even a few cases of recurrent or chronic pain would be helpful. We describe 2 patients for whom back mice were the likely cause of low back pain and were associated with unusual symptoms and signs, masquerading as other clinical problems. In both cases, the full medical records from the Family Practice Center and University of North Carolina hospitals were available for evaluation.
Methods and results
Bilateral Trochanteric Bursitis
In 1985 Ms C, a 53-year-old nursing aide, developed typical signs and symptoms of trochanteric bursitis following a vaginal hysterectomy. She also suffered from mild hypertension and chronic depression. The hip pain was intermittent and would affect one side and then the other, often radiating down the legs and limiting her ability to walk. Examination revealed marked tenderness to palpation over the greater trochanter in either hip area. There were no clear precipitating factors.
She was first treated with a variety of nonsteroidal anti-inflammatory agents, with little effect. Subsequently, she received physical therapy including ultrasound, exercise, and cushioned shoes, all of which produced only temporary relief. Because of the chronic pain antidepressants were also tried, which improved her depression but provided minimal improvement for the hip problem.
In 1991, orthopedic evaluation confirmed the findings of relapsing bilateral trochanteric bursitis with an otherwise normal physical examination. Lumbosacral spine and hip radiographs showed only mild degeneration of the L4/5 vertebral disk. The greatest relief for the patient came from injections of lidocaine hydrochloride and methylprednisolone acetate directly into each bursa, but relief lasted only a few weeks after each injection. They had to be repeated on a regular basis. She also needed acetaminophen and oxycodone twice daily to help control the pain, and in 1995 she applied for disability.
At that time, the orthopedic specialist discharged her back to her family physician with a diagnosis of chronic trochanteric bursitis for which no other treatment could be offered. In 1997 another orthopedic consultation led to the same opinion, based on typical symptoms and clinical findings. In 1998, during a discussion of the lack of treatment options for this chronic problem, it was suggested that the symptoms could be secondary to a lower back problem and a careful soft tissue examination might be of value. Detailed examination revealed 2 long rubbery and tender fibro-fatty nodules, each one lying on an iliac crest (right side=3 cm by l cm; left side=6 cm by l cm) These findings correlated with previous descriptions of fibro-fatty nodules in the back region.4,7
Repeated testing using firm palpation of these nodules reproduced the pain over each greater trochanteric area where the patient had experienced pain in the past. Each nodule was treated with multiple puncture technique (6 to 8 punctures of the fibrous capsule of the nodule) and injected with 3 cc of lidocaine hydrochloride and 40 mg methylprednisolone acetate.4,5 There was immediate and complete relief of the clinical symptoms and signs. Five months after the injections there has been no recurrence of the clinical characteristics of trochanteric bursitis, though there have been other symptoms of lumbosacral pain.