Journal of NeuroEngineering and Rehabilitation

Table 1 Model parameters, assumptions and data sources Model parameter Base case Range Data sources Probability of falling per year [ 26 , 60 ] MPK 26.00% 22.20 – 32.00% NMPK 82.00% 75.00 – 87.50% Proportion of medical falls 10.40% 6.20 – 19.60% [ 61 – 63 ] Proportion of fatal medical falls 7.00% 6.30 – 7.70% a [ 64 ] Proportion of major injury falls 40.00% 32.60 – 40.00% [ 65 , 66 ] Proportion of minor injury falls 53.00% 53.00 – 60.50% Average number of falls per faller per year [ 26 , 59 ] MPK 3.20 2.00 – 3.20 NMPK 3.87 1.86 – 3.87 Odds ratio of falling in year 4 vs. year 1 0.53 0.48 – 0.58 a [ 67 ] Medical cost per major injurious fall $24,844.52 $16,978.61 - $31,707.24 [ 65 , 66 , 68 ] Medical cost per minor injurious fall $1332.47 $620.69 - $6005.62 Medical cost of fall-related death $27,337.76 $27,337.76 - $29,578.20 [ 68 , 69 ] Caregiving expenses per person per year [ 39 , 70 – 72 ] MPK $2754.29 $2478.86 - $3029.72 a NMPK $3477.60 $3129.84 - $3825.36 a Lost wages per person per year MPK $1669.11 $1502.20 - $1836.02 a NMPK $2144.06 $1929.65 - $2358.47 a Transportation expenses per person per year MPK $463.46 $417.11 - $509.81 a NMPK $300.36 $270.32 - $330.40 a Baseline prevalence of osteoarthritis (knee) Medicare claims data 2011 – 2014 K1/K2 16.30% 14.67 – 17.93% a K3/K4 19.10% 17.19 – 21.01% a Probability of developing osteoarthritis per year [ 34 ] ; Expert opinion MPK 1.50% 1.35 – 1.65% a NMPK 2.21% 1.99 - 2.43% a Osteoarthritis-related medical cost per year $6639.72 $996.41 - $14,682.92 [ 73 ] Osteoarthritis-related indirect cost per year $1084.21 $606.89 - $1192.63 [ 74 , 75 ] Baseline mortality rate Medicare claims data 2011 – 2014 K1/K2 18.00% 16.20 – 19.80% a K3/K4 9.31% 8.38 – 10.24% a Device acquisition cost in 10 years 2016 Medicare fee schedule; Medicare claims data 2011 – 2014; Expert opinion MPK (plus 1 replacement) $56,000.00 $44,750.00 - $58,118.00 NMPK (plus 2 replacements) $16,500.00 $7785.00 - $22,101.00 Device repair cost per year MPK $192.23 $173.01 - $211.45 a NMPK $135.95 $122.36 - $149.55 a Physical therapy cost in year 1 MPK $1986.68 $1788.01 - $2185.35 a NMPK $1648.62 $1483.76 - $1813.48 a Chen et al. Journal of NeuroEngineering and Rehabilitation 2018, 15 (Suppl 1):62 Page 52 of 72