Skip to main content

Table 1 Model parameters, assumptions and data sources

From: Economic benefits of microprocessor controlled prosthetic knees: a modeling study

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% [61,62,63]
 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 0.48–0.58a [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 - $3029.72a
 NMPK $3477.60 $3129.84 - $3825.36a
Lost wages per person per year   
 MPK $1669.11 $1502.20 - $1836.02a
 NMPK $2144.06 $1929.65 - $2358.47a
Transportation expenses per person per year   
 MPK $463.46 $417.11 - $509.81a
 NMPK $300.36 $270.32 - $330.40a
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 - $211.45a
 NMPK $135.95 $122.36 - $149.55a
Physical therapy cost in year 1   
 MPK $1986.68 $1788.01 - $2185.35a
 NMPK $1648.62 $1483.76 - $1813.48a
Physical therapy cost in year 2   
 MPK $1621.68 $1459.51 - $1783.85a
 NMPK $1347.47 $1212.72 - $1482.21a
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]
  1. MPK microprocessor-controlled knees, NMPK non-microprocessor controlled knees. K1-K4: Medicare Functional Classification Level 1 to 4, respectively
  2. aThere are no range values directly from the literature; in the sensitivity analyses, they were derived through varying the base case value up and down by 10%. The design of the studies comparing the effectiveness of MPK to NMPK: Prospective cohort study [26, 39, 59, 60]; Retrospective cohort study [37, 40]; Cross-sectional study [38])