What Are the Patient-reported Outcomes After Elective Transtibial Amputation? A Comparison of CRPS, Neuropathic Pain, and Other Conditions That Lead to Late Amputation After Limb Salvage

Background In the United States, approximately 2.3 million people live with limb loss, of whom about 91% have undergone lower extremity amputation. Despite these numbers, relatively few studies have evaluated outcomes after elective transtibial amputation. In particular, we do not know whether the outcomes after amputation for intractable neurogenic pain such as complex regional pain syndrome (CRPS) are comparable to outcomes after late amputations (6 weeks or more after limb salvage) performed for other reasons such as recurrent infection, soft tissue problems, recalcitrant nonunion, poor function, and chronic nonneurogenic pain. Questions/purposes (1) Did patients who underwent late amputation for CRPS or neuropathic pain have inferior Patient-Reported Outcomes Measurement Information System (PROMIS) scores at follow-up compared with patients who had nonneurogenic elective amputation? (2) Did patients who underwent late amputation for CRPS or neuropathic pain have more pain, use more pain medication, or wear prosthetics less often than patients who have undergone nonneurogenic elective amputation? (3) Were patients who underwent late amputation for CRPS or neuropathic pain more likely to be revised to a higher level of amputation or express decision regret than patients undergoing nonneurogenic elective amputation? Methods This retrospective comparative study examined 70% (50 of 71) of patients who underwent elective (that is, scheduled, nonurgent) transtibial amputation between July 2006 and September 2019 at least 6 weeks after lower extremity trauma (median range 2 years 6 weeks to 15 years). Most patients were men (94% 47 of 50) and active duty service members who sustained combat-related trauma (74% 37 of 50). Patients with CRPS (defined using the Budapest criteria diagnostic guidelines, which requires ongoing disproportionate pain plus signs in four categories: sensory, vasomotor, sudomotor/edema, and motor/trophic changes, n = 10) and other forms of neuropathic pain (n = 10) were compared with a control group of patients who had nonneurogenic elective amputation (n = 30). Demographic characteristics among cohorts were not different given the numbers available. The median (range) follow-up was 9 years (3 to 16) after amputation. The primary outcome was the PROMIS pain interference score. Secondary outcomes included other PROMIS metrics, VAS pain, and patient-reported medication and prosthetic use as well as revision to a higher level of amputation and decision regret. Results With the numbers available, we found no difference in PROMIS pain interference scores for patients with transtibial amputations performed for neurogenic pain compared with other causes of late amputation (median range 57 45 to 64 versus 56 39 to 72; p = 0.81). There were likewise no differences with the numbers available in PROMIS physical function, mobility, life satisfaction, and severity of substance use. Amputations performed for neurogenic pain resulted in more pain reduction than late amputations for other causes (median ΔVAS -5 -9 to -1 versus median Δ VAS -3 -8 to 7; p = 0.02). Both groups reported a reduction in opioid use (100% reduction in median frequency of opioid administrations for both groups; p < 0.001). Prosthetic use was not different with the numbers available among all cohorts. No patients in the CRPS plus neuropathic pain cohort were revised to a higher level of amputation compared with 2 patients in the nonneurogenic elective amputation cohort. No patients expressed definitive decision regret. Conclusion Patients undergoing elective transtibial amputations for intractable neurogenic pain experienced clinically meaningful improvement in pain. Our findings support the use of transtibial amputation for treatment-resistant neurogenic pain, and they provide reasonable, but generally favorable, expectations for patients considering this irreversible procedure that are generally comparable to outcomes from patients undergoing late amputations for other indications. Level of Evidence Level III, therapeutic study.