Ultrasound unveils source of stump pain in amputees

High-resolution sonography can accurately detect the causes of residual limb pain in amputees, according to British researchers, who found that ultrasound can guide proper treatment and rehabilitation, help educate patients about their condition, and even help with design and fitting of prostheses.

Stump pain impairs function and mobility and may seriously undermine an amputee's quality of life. Finding the source of pain is thus crucial to provide proper treatment and relief.

MRI is often the imaging modality of choice in the investigation of stump pain. Because of the multiple abnormalities that can be found in any one patient, however, it may be difficult to identify the most relevant cause of pain with MRI alone, said principal investigator Dr. Marian O'Reilly, a consultant radiologist at Kingston Hospital in Surrey.

"With ultrasound, the soft tissue abnormalities can not only be demonstrated but, by using probe pressure to reproduce the patient's symptoms, the clinical relevance of the findings will often be apparent," O'Reilly told Diagnostic Imaging. "In addition, a standard MRI examination will demonstrate only the larger neuromas and this study found that the degree of pain does not correlate with neuroma size."

O'Reilly and colleagues evaluated 90 surgically foreshortened limbs among 79 patients with stump pain over an 18-month period. The patients underwent ultrasound with linear probes.

Previous research suggests residual limb pain is related to the response of the bone and soft tissues to trauma, surgical treatment, and underlying disease processes. The investigators found the three main causes of stump pain in study subjects were neuromas, new bone formation, and infection. They also found that overuse injuries were common causes of pain. Their findings were initially discussed at the 2008 American Roentgen Ray Society meeting.

Researchers identified 68 neuromas in 40 patients but found the degree of pain did not correlate with a neuroma's size. Immature heterotopic new bone formation was the main cause of pain in six patients, while mature bony spurs were the main cause in seven and a contributing cause in five. Soft tissue infection and nonspecific inflammation/edema were the main cause of pain in 11 and six patients, respectively.

Overuse injuries comprised muscle tears, tendinosis, and secondary degenerative joint disease. Other causes of pain included bursae, soft tissue calcifications, bony erosions, Baker's cyst, and tender scarring. Nonlocal causes included spondylolisthesis with nerve root compression and recurrence or exacerbation of preexisting disease.

Using ultrasound findings, clinicians can prescribe appropriate rehabilitation and treatment, O'Reilly said. Prosthetists working at her institution found ultrasound results helpful for the design and customization of prostheses for individual patients. And patients were interested in knowing more about their limb, the alteration of the anatomy and the location of any abnormalities, she said.

"This increased their confidence in wearing their prosthesis, which can then be adapted to increase their comfort and activities," O'Reilly said.

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