Table 1 Model parameters, assumptions and 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%

[61,62,63]

 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, 70,71,72]

 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

Physical therapy cost in year 2

 MPK

$1621.68

$1459.51 - $1783.85^a

 NMPK

$1347.47

$1212.72 - $1482.21^a

Health utilities

[37,38,39,40]

 MPK

0.82

0.75–0.83

 NMPK

0.66

0.60–0.92

Discount rate

3.00%

2.00–5.00%

[76]