To the Editor:
We read with interest the paper of Karanikolas et al .1demonstrating the importance of effective perioperative analgesia in the prevention of phantom limb pain. Their finding that appropriate pain relief, regardless of the method of delivery, reduces the prevalence of phantom limb pain at 6 months is an important contribution to the postamputation pain literature. We also noted there was no significant difference between the treatment and control groups with respect to the prevalence of residual limb pain at 1 and 6 months. Although this lack of treatment effect certainly could be a result of small sample size, it also may be secondary to lack of differentiation of the subtypes of residual limb pain.
Previous reports of persistent postamputation pain2,–,4have differentiated between pain arising from a phantom and that from the residual limb; however, subclassifications of residual limb pain are not performed typically (or at least reported). In the Durham Veterans Administration Medical Clinic postamputation pain clinic, we recently recognized the existence of at least three distinct residual limb pain subtypes: somatic pain, complex regional pain syndrome-like pain, and neuroma/neuralgia pain. Although these are well-recognized pain diagnoses in their own right, they usually are not used in the specific clinical setting of persistent postamputation pain. We believe that recognition of these distinct subtypes may help to better identify effective prevention strategies and/or treatments. These subtypes have different proposed etiologies and are unlikely to respond to similar treatments.
For these reasons, we believe that the historic failure to recognize distinct subtypes of residual limb pain has led us to paint with too wide a brush, and in the article by Karanikolas et al ., this could have hidden a positive treatment effect in one or another residual limb pain subtype.
To address what we see as a deficiency in the current state of the art regarding postamputation pain taxonomy, we have developed a diagnostic algorithm that is capable of differentiating the subtypes of residual limb pain described above. We are validating this algorithm in our amputation pain clinic and encourage others in the field to consider further differentiating residual limb pain into its component subtypes.