844 - Investigating the role of time interval between amputation and targeted muscle reinnervation for outcomes of prescription pain medication use and phantom limb pain in lower extremity amputees

Objectives: Targeted muscle reinnervation (TMR) has shown efficacy in the prevention and treatment of neuroma and phantom limb pain (PLP) in amputees. “Acute” and “delayed” refer to the time interval between index amputation and TMR procedure, with < 2 weeks noted for acute TMR in the literature. This study aims to investigate time interval for delayed TMR as it relates to pain-related outcomes in major lower-extremity amputees (LEA).

Design:

Method: Retrospective chart review.
Setting: Amputee/Prosthetic Clinic in an academic medical center.

Participants: Study size was determined by the availability of major single-limb LEA patients who met inclusion criteria. 19 patients (19 limbs) (ages 29-79, M = 49.7, SD = 15.7) who underwent delayed TMR (interval >= 2 weeks) within the 7-year review period were included.

Main Endpoints: Self-reported prescription pain medication (PPM) usage for amputation and self-reported experience of PLP using binary scales (yes/no) on follow-up Amputee/Prosthetic Clinic visits post-TMR procedure. 

Results:

Results: The distribution for calculated time interval in weeks (M = 16.9; SD = 151.3) was split into three groups (2-7, 7-21, 21-607) (n=7,6,6) for analysis across all follow-up visits (n=51). Using mixed-effects logistical model, time-interval group did not predict PPM usage (p = 0.28; 0.50) or self-reported PLP (p = 0.15; 0.09) compared to reference group (2-7). However, for patients 60 or older (n=8) with distribution split into two equal groups (7-21; 21-607) across follow-up visits (n=18) and analyzed using exact logistic regression model, larger time-interval group was a significant negative predictor for experiencing PLP (OR = 0.05, CI 0.0-0.4; p=0.001).

Conclusions:

Conclusions: These preliminary results suggest that further exploration of time interval for TMR is warranted for pain-related outcomes in older populations. Limitations included low sample size and high variability, with future analysis to stratify endpoints by time-interval-group at specific follow-up intervals expected to further elucidate findings.