Frequency Content of Cartilage Impact Force Signal Reflects Acute Histologic Structural Damage

OBJECTIVE The objective of this study was to determine if acute cartilage impact damage could be predicted by a quantification of the frequency content of the impact force signal. DESIGN Osteochondral specimens excised from bovine lateral tibial plateaus were impacted with one of six impact energies. Each impact force signal underwent frequency analysis, with the amount of higher-frequency content (percent of frequency spectrum above 1 KHz) being registered. Specimens were histologically evaluated to assess acute structural damage (articular surface cracking and cartilage crushing) resulting from the impact. RESULTS Acute histologic structural damage to the cartilage had higher concordance with the high-frequency content measure than with other mechanical impact measures (delivered impact energy, impact maximum stress, and impact maximum stress rate of change). CONCLUSIONS This result suggests that the frequency content of an impact force signal, specifically the proportion of higher-frequency components, can be used as a quick surrogate measure for acute structural cartilage injury. Taking advantage of this relationship could reduce the time and expense of histological processing needed to morphologically assess cartilage damage, especially for purposes of initial screening when evaluating new impaction protocols.