Unresolved pain is often neurogenic in origin; therefore, listening to the patient, as well as relying on one’s best clinical judgment, can help with diagnosing the sometimes difficult-to-spot conditions that result in this potentially debilitating symptom.
Stephen L. Barrett, DPM, an adjunct professor in the Podiatric Medicine Program at Midwestern University College of Health Sciences and founder of Barrett Foot & Ankle in Phoenix, Arizona, provided guidance on addressing the etiology of chronic lower extremity pain.
During his presentation, he urged clinicians to have a “high index of suspicion” for neurogenic causes of pain following ankle injury or total knee arthroplasty, as well as of plantar fasciitis, that “fly under the radar” and offered some pearls for those in attendance about how to identify these patients.
Dr. Barrett advised that patients’ descriptions can often be very informative. Phrases like “it burns, even when I’m not on it,” can be a good indicator of a peripheral nerve injury. He also said gait analysis, radiographs, and diagnostic nerve blocks using lidocaine can facilitate appropriate assessment.
Elaborating on lidocaine blocks, Dr. Barrett noted that a ligamentous injury is often erroneously blamed as the generator of lower extremity pain, but this not likely 8 weeks after sustaining an injury.
“ [The pain generator] is easy to diagnose with intra-articular injection of lidocaine,” he said.
Shifting gears to pain associated with ankle sprain, Dr. Barrett noted that there are many sequelae after ankle injury, including entrapment of the common fibularis (peroneal), superficial fibularis, and/or sural nerves, as well as sinus tarsi syndrome.
Dr. Barrett then expanded on heel pain, which is the most frequent complaint prompting presentation to a podiatric practice. He described several neurogenic causes including entrapment of the medial calcaneal nerve or the medial and lateral plantar nerve (tarsal tunnel syndrome). Further causes of heel pain include plantar fasciitis, infracalcaneal fat pad atrophy, rheumatoid arthritis, Reiter’s syndrome, ankylosing spondylitis, psoriatic arthritis, gout, and fibromyalgia, among others.
To identify the cause of heel pain, Dr. Barrett discussed using a medial calcaneal nerve block, which involves local anesthestic infiltration using a careful injection technique from proximal to distal and approximately 1 cm in depth. Resolution of the heel pain would confirm the etiology as entrapment of the medial calcaneal nerve.
In summarizing his presentation, Dr. Barrett reiterated: “Always listen to your patients … because most often they are able to isolate their primary pain generator; implement the use of diagnostic nerve blocks with lidocaine in suspected areas where pain generators are identified, and repeat these if there are equivocal results initially; and determine if the pain is centralized, because if it is, the likelihood of peripheral intervention being successful is greatly reduced.”