Analyse der Passgenauigkeit der Prothesenköpfe der Ascension® PyroCarbon-Fingermittelgelenksprothese

BACKGROUND: The Ascension pyroCarbon proximal interphalangeal (PIP) total joint is available in 4 different sizes, and ideally, the prosthesis head will be flush with the bone. Fit of the Ascension pyrocarbon PIP joint prosthesis has not yet been investigated.

MATERIALS AND METHODS: The components of the Ascension pyrocarbon PIP total joint were inserted in 287 phalanges of human cadaver specimens. The distances from the edge of the component head to the edge of the bone were electronically measured radially, ulnarly, dorsally and palmarly on radiographs in posterior-anterior and lateral views.

RESULTS: Only one finger had a precise fit of the heads of both, the proximal and corresponding distal component in relation to the bone. Only in 17 (5 proximal, 12 distal) prosthesis components the head did the bone fit on all sides. Overall, the proximal component head tends to be too large, while the distal component head tends to be too small.

CONCLUSION: With occasional exceptions, the proximal and distal component heads of the Ascension pyrocarbon PIP total joint do not accomodate the dimensions of finger phalanges.