Table 3.

Comparison of Impact Parameters Measured In Situ Using Internal Load Cell Versus Pressure-Sensitive Film^a

Detection method	Force (N)	Absolute area (mm2)b	Calculated load (MPa)	Maximum displacement (%)c
Internal load cell	326.9 ± 47.30	1.39 ± 0.11	212.9 ± 21.2	21.50 ± 4.50
Pressurex pressure-sensitive film	439.3 ± 50.13d	1.33 ± 0.42	330.3 ± 50.3	14.23 ± 3.33e

^aAll impacts generated using a blunt hemispherical tip.

^bArea determined through upper 88 % intensity (LUT function, NIH Image 1.6) of total footprint.

^cCartilage depth determined by comparison of light micrographs of impacted and neighboring unimpacted cartilage.

^dMagnitude calculated from the footprint obtained using medium-grade Pressurex pressure-sensitive film footprint.

^eBased on average lapine articular cartilage thickness in this study, 378 ± 87 mm.