AMPREDICT PROsthetics-Predicting Prosthesis Mobility to Aid in Prosthetic Prescription and Rehabilitation Planning

Validation of the Amputee Single Item Mobility Measure (AMPSIMM) and the abbreviated AMPSIMM-4 for amputee mobility

ObjectiveTo evaluate the criterion and construct validity of the 7-category Amputee Single Item Mobility Measure (AMPSIMM) in a large contemporary dysvascular lower limb amputation population and propose an abbreviated 4-category version (AMPSIMM-4) whose mobility categories parallel the Medicare Functional Classification Levels (K-levels).DesignCohort study retrospectively identifying persons with their first lower limb amputation then prospectively collecting their self-reported mobility.SettingNational cohort identified through a large Veterans' Administration dataset.ParticipantsSix hundred and ninety-two participants aged 30 years and older, undergoing their first diabetes and/or peripheral artery disease-related amputation at the transmetatarsal, transtibial, or transfemoral level, with a subset of 60 consecutive participants with a self-reported K-level.Main measuresAMPSIMM, Locomotor Capability Index-5 (LCI-5), K-levels, and PROMIS Global-10 Physical (PROMIS-P), at one year post amputation.ResultsThe strength of the correlation between AMPSIMM and LCI-5 scores was large (Spearman's rho = .88; p < .0001). The correlation with PROMIS-P scores was 0.67 (p < .0001). The strength of the correlation between the AMPSIMM-4 and self-reported K-levels was large (Spearman's rho = .82; p < .0001).ConclusionsThe AMPSIMM is a clinician-friendly single-item patient-reported measure that can capture a broad range of lower limb amputation mobility, from wheelchair to advanced community ambulation, with or without a prosthesis, and with or without ambulation aids. It demonstrates strong criterion and construct validity. The AMPSIMM-4 can be generated directly from the AMPSIMM with descriptors that are very similar to and are highly correlated with self-reported K-levels.

Applying mobility prediction models to real-world patients with major amputations

BACKGROUND

Outcome prediction models (PMs) have become commonplace and are promoted to aid in counseling patients. The aim of this study is to evaluate the performance of existing mobility PMs for post-major amputation (MA) patients in a real-world, socioeconomically disadvantaged population.

METHODS

A retrospective review of patients with MA secondary to peripheral arterial disease from 2016 to 2022 was performed. Patients who were nonambulatory before MA or with contralateral MA were excluded. Three published PMs were investigated: (1) AmpPredict (predicts 1-year mobility), (2) Amputee Single Item Mobility Measure, (predicts degree of mobility with prosthesis at 1 year), both derived from Veteran's Affairs data, and (3) a Vascular Quality Initiative (VQI) data-derived model (predicts 1-year mobility). Predicted mobility rates vs actual mobility rates were compared.

RESULTS

The study cohort consisted of 126 patients, 71% male, 60% non-White race, with a mean state Area Deprivation Index of 9 of 10. Baseline characteristics were significantly different between the study and derivation cohorts. Actual mobility at 1 year was 43%. Of the 38 patients with an AmpPredict 1-year mobility of ≥70%, 45% actually achieved mobility. Of 101 patients with a high predicted probability from the VQI score (≥71%), 48% achieved mobility. The mean difference between AmpPredict and VQI for a given patient was 36% (range, 1%-81%). The Amputee Single Item Mobility Measure predicted 87% of patients would be community (vs home) ambulators at 1 year and 32% of patients actually achieved community ambulation (sensitivity of 91%, specificity of 14%, positive predictive value of 33%, and negative predictive value of 79%).

CONCLUSIONS

Published models dramatically overestimated the likelihood of mobility in our patient cohort. This result may be related to the demographics and comorbidities of our cohort being significantly different from the derivation cohorts. We recommend caution when applying PMs to a population with significantly different characteristics from the population used to derive the model.

AMPREDICT MoRe: Predicting Mortality and Re-amputation Risk after Dysvascular Amputation

OBJECTIVE

This study aimed to create a novel prediction model (AMPREDICT MoRe) that predicts death and re-amputation after dysvascular amputation, which overcomes prior implementation barriers by using only predictors that are readily available in the electronic health record (EHR).

METHODS

This was a retrospective cohort study of 9 221 patients with incident unilateral transmetatarsal, transtibial, or transfemoral amputation secondary to diabetes and or peripheral arterial disease identified in the Veterans Affairs Corporate Data Warehouse between 1 October 2015 and 30 September 2021. The prediction model evaluated factors falling into several key domains: prior revascularisation; amputation level; demographics; comorbidities; mental health; health behaviours; laboratory values; and medications. The primary outcome included four categories: (i) no death and no re-amputation (ND/NR); (ii) no death and re-amputation (ND/R); (iii) death and no re-amputation (D/NR); and (iv) death and re-amputation (D/R). Multinomial logistic regression was used to fit one year post-incident amputation risk prediction models. Variable selection was performed using LASSO (least absolute shrinkage and selection operator), a machine learning methodology. Model development was performed using a randomly selected 80% of the data, and the final model was externally validated using the remaining 20% of subjects.

RESULTS

The final prediction model included 23 predictors. The following outcome distribution was observed in the development sample: ND/NR, n = 4 254 (57.7%); ND/R, n = 1 690 (22.9%); D/NR, n = 1 056 (14.3%); and D/R, n = 376 (5.1%). The overall discrimination of the model was moderately strong (M index 0.70), but a deeper look at the c indices indicated that the model had better ability to predict death than re-amputation (ND/NR vs. ND/R, 0.64; ND/NR vs. D/NR, 0.78; grouped ND vs. D, 0.79 and NR vs. R, 0.67). The model was best at distinguishing individuals with no negative outcomes vs. both negative outcomes (ND/NR vs. D/R, 0.82).

CONCLUSION

The AMPREDICT MoRe model has been successfully developed and validated, and can be applied at the time of amputation level decision making. Since all predictors are available in the EHR, a future decision support tool will not require patient interview.

Racial disparities in prosthesis abandonment and mobility outcomes after lower limb amputation from a dysvascular etiology in a veteran population

BACKGROUND

Non-Hispanic Black (NHB) individuals have higher rates of amputation and increased risk of a transfemoral amputation due to dysvascular disease than non-Hispanic White (NHW) individuals. However, it is unclear if NHB individuals have differences in prosthesis use or functional outcomes following an amputation.

OBJECTIVE

To determine if there are racial disparities in prosthesis abandonment and mobility outcomes in veterans who have undergone their first major unilateral lower extremity amputation (LEA) due to diabetes and/or peripheral artery disease.

DESIGN

National cohort study that identified individuals retrospectively through the Veterans Affairs (VA) Corporate Data Warehouse (CDW) from March 1, 2018, to November 30, 2020, then prospectively collected their self-reported prosthesis abandonment and mobility. Multiple logistic regression was used to control for potential confounders and identify potential effect modifiers.

SETTING

The VA CDW, participant mailings and phone calls.

PARTICIPANTS

Three hundred fifty-seven individuals who underwent an incident transtibial or transfemoral amputation due to diabetes and/or peripheral arterial disease.

INTERVENTIONS

Not applicable.

MAIN OUTCOMES MEASURES

(1) Self-reported prosthesis abandonment. (2) Level of mobility assessed using the Locomotor Capabilities Index.

RESULTS

Rurally located NHB individuals without a major depressive disorder (MDD) had increased odds of abandoning their prosthesis (adjusted odds ratios [aOR] = 5.3; 95% confidence interval [CI]: [1.3-21.1]). This disparity was nearly three times as large for rurally located NHB individuals with MDD diagnosis, compared with other races from rural areas and with MDD (aOR = 15.8; 95% CI, 2.5-97.6). NHB individuals living in an urban area were significantly less likely to achieve advanced mobility, both with MDD (aOR=0.16; 95% CI: [0.04-7.0]) and without MDD (aOR = 0.26; 95% CI: [0.09-0.73]).

CONCLUSIONS

This study demonstrated that health care disparities persist for NHB veterans following a dysvascular LEA, with increased prosthesis abandonment and worse mobility outcomes.

Predicting Functional Outcomes Following Dysvascular Lower Limb Amputation: An Evidence Review of Personalizing Patient Outcomes

Most research on people undergoing lower limb amputations for dysvascular disease summarizes average patient outcome risks and average associations between patient factors and these outcomes. More recently, the importance of predicting patient-specific outcomes based on individual factors (ie, personalized rehabilitation) has become evident. This article reviews the evidence and discusses the importance of the following: (1) predicting outcomes to facilitate amputation-level and prosthesis prescription decisions and (2) how prediction models can be leveraged to develop decision support tools to facilitate provider/patient shared decision-making to ensure decisions considering each individual patient's priorities and preferences. Examples of these tools are discussed and referenced.

The Effect of Prosthetic Limb Sophistication and Amputation Level on Self-reported Mobility and Satisfaction With Mobility

OBJECTIVE

To determine if lower limb prosthesis (LLP) sophistication is associated with patient-reported mobility and/or mobility satisfaction, and if these associations differ by amputation level.

DESIGN

Cohort study that identified participants through a large national database and prospectively collected self-reported patient outcomes.

SETTING

The Veterans Administration (VA) Corporate Data Warehouse, the National Prosthetics Patient Database, participant mailings, and phone calls.

PARTICIPANTS

347 Veterans who underwent an incident transtibial (TT) or transfemoral (TF) amputation due to diabetes and/or peripheral artery disease and received a qualifying LLP between March 1, 2018, and November 30, 2020.

INTERVENTIONS

Basic, intermediate, and advanced prosthesis sophistication was measured by the accurate and reliable PROClass system.

MAIN OUTCOME MEASURE

Patient-reported mobility using the advanced mobility subscale of the Locomotor Capabilities Index-5; mobility satisfaction using a 0-10-point Likert scale.

RESULTS

Lower limb amputees who received intermediate or advanced prostheses were more likely to achieve advanced mobility than those who received basic prostheses, with intermediate nearing statistical significance at nearly twice the odds (adjusted odds ratio (aOR)=1.8, 95% confidence interval (CI), .98-3.3; P=.06). The association was strongest in TF amputees with over 10 times the odds (aOR=10.2, 95% CI, 1.1-96.8; P=.04). The use of an intermediate sophistication prosthesis relative to a basic prosthesis was significantly associated with mobility satisfaction (adjusted β coefficient (aβ)=.77, 95% CI, .11-1.4; P=.02). A statistically significant association was only observed in those who underwent a TT amputation (aβ=.79, 95% CI, .09-1.5; P=.03).

CONCLUSIONS

Prosthesis sophistication was not associated with achieving advanced mobility in TT amputees but was associated with greater mobility satisfaction. In contrast, prosthesis sophistication was associated with achieving advanced mobility in TF amputees but was not associated with an increase in mobility satisfaction.