Multimodality imaging review of the post-amputation stump pain

Abstract

Limb amputation is one of the oldest known surgical procedures performed for a variety of indications. Little surgical technical improvements have been made since the first procedure, but perioperative and post-operative refinements have occurred over time. Post-amputation pain (PAP) of the stump is a common complication but is an extremely challenging condition to treat. Imaging allows early diagnosis of the underlying cause so that timely intervention is possible to minimize physical disability with its possible psychological and socioeconomic implications. A multidisciplinary approach should be taken involving the rehabilitation medicine team, surgeon, prosthetist, occupational therapist and social workers. Conventional radiographs demonstrate the osseous origin of PAP while high-resolution ultrasound is preferred to assess soft-tissue abnormalities. These are often the first-line investigations. MRI remains as a problem-solving tool when clinical and imaging findings are equivocal. This article aimed to raise a clear understanding of common pathologies expected in the assessment of PAP. A selection of multimodality images from our Specialist Mobility and Rehabilitation Unit are presented so that radiologists are aware of and recognize the spectrum of pathological conditions involving the amputation stump. These include but are not limited to aggressive bone spurs, heterotopic ossification, soft-tissue inflammation (stump bursitis), collection, nervosas, osteomyelitis etc. The role of the radiologist in reaching the diagnosis early is vital so that appropriate treatment can be instituted to limit long-term disability. The panel of authors hopes this article helps readers identify the spectrum of pathological conditions involving the post-amputation stump by recognizing the imaging features of the abnormalities in different imaging modalities.

Figure 1.

Stump neuromas: high-resolution soft-tissue ultrasound (a) is showing two discrete hypoechoic lesions (arrows) typical of end neuromas. (b) An ultrasound image is showing a spindle neuroma (asterisk) away from the severed nerve end and characteristic “tail sign” of the involved nerve (arrow) proximally. Axial (c) and coronal (d) fat-suppressed MR images are showing the ovoid well-defined high-signal soft-tissue mass (arrows) characteristics of stump neuroma.

Figure 2.

Soft-issue inflammation: conventional lateral radiograph of the stump (a) is demonstrating a bone spur (arrow) at the inferior edge of the stump. High-resolution soft-tissue ultrasound of the same patient (b) is revealing the bone spur (arrow) and associated bursal fluid distension (asterisk). An ultrasound image in a different patient (c) is showing a deep-seated collection (asterisk) and two sinus tracts (arrows) communicating the collection with skin surface.

Figure 3.

Lateral conventional radiograph of an amputation stump (a) is showing heterotopic ossification (solid arrow) of the soft tissue, which in itself is swollen and is of higher density than the remainder of the soft tissues. These ossification foci are discontinuous from linear vascular calcification. High-resolution ultrasound (c) is confirming the presence of soft-tissue ossification focus (black arrow), with strong post-acoustic shadowing. Anteroposterior stump radiograph of another patient (b) is demonstrating a prominent bone spur within the lateral edge of the fibular stump (white arrow), which has been redemonstrated (curved arrow) on high-resolution ultrasound (d).

Figure 4.

Osteomyelitis: conventional radiograph (a) is revealing osseous destruction and periosteal new bone formation (solid arrow) at the stump end. An ultrasound image of the same patient (b) is demonstrating bony irregularities with periosteal reaction (curved arrow) and adjacent soft-tissue inflammatory changes (star). Fat-suppressed sagittal T₂ weighted (T2W) (c) and axial T2W (d) MR images are confirming the presence of the intramedullary abscess.

Figure 5.

Osteomyelitis: coronal T₁ weighted (a) and coronal short tau inversion-recovery (b) MR images are demonstrating extensive soft-tissue inflammation (arrows) and bone marrow oedema (curved arrow) compatible with stump soft-tissue infection with local contagious spread of soft-tissue infection resulting in stump osteomyelitis. A 4-h delayed planar bone scintigram image (c) of the same patient is confirming avid tracer uptake (solid arrow) at the site of osteomyelitis. The degenerative pattern of uptake within the ipsilateral knee can be noted. A Leukoscan image (d) is confirming avid uptake (thin arrow) in the same area.

Figure 6.

Stress reaction: axial T₁ weighted (a), axial short tau inversion-recovery (STIR) (b) and coronal STIR (c) MRI sequences are demonstrating subtle oedema-like changes at the stump–prosthesis interface (arrows) compatible with normal marrow response to altered biomechanics following amputation. The well-defined marrow changes with no associated soft-tissue inflammatory response can be noted.

Figure 7.

Tumour recurrence: conventional anteroposterior radiograph (a) of a young patient showing aggressive lytic lesion in medial tibial metaphysis (solid arrow). Coronal T₁ weighted MRI (b) is confirming the low-signal mass (white star), which was proven to be tibial sarcoma on histology. 3 years after the amputation, the patient presented with stump pain. Conventional radiograph (c) is revealing osseous destruction at the stump end (arrow). Coronal short tau inversion-recovery MR image (d) is showing tumour recurrence with extensive aggressive osseous abnormalities (black star) and soft-tissue component of the lesion.