Unacceptable failure of the PI2® implant

The PI2 (R) spacer is designed for treatment of trapeziometacarpal (TM) osteoarthritis. However, the shape of this implant has raised concerns about its stability. We retrospectively investigated 45 implants in 41 patients treated for trapeziometacarpal osteoarthritis in our hospital between 2004 and 2009 who underwent trapeziectomy and insertion of a PI2 (R) spacer. Outcome parameters included revision rates and clinical outcomes correlated with implant position and scaphometacarpal distance, assessed using standard radiographs. A total of 12 implants (27%) were removed at a median time of 10months (interquartile range (IQR), 7-22months). These included five dislocations and one early infection. Additionally, a further six patients underwent revision due to persistent pain. Three of these had scapho-trapezoid osteoarthritis, two had developed subluxation of the implant, and one did not show any radiographic abnormalities. A review of patient records revealed that 33 implants remained in place at a median time of 29months (IQR, 20-57). However, of those, only 21 implants (64%) in 17 patients were available for clinical evaluation at a median follow-up of 29months (IQR, 19-62months). No significant differences in clinical outcomes including functional results were observed between in-place (n=8) and subluxated (n=13) implants. Due to the high revision rate (12/45), consistent with other reports in the literature, we have abandoned the use of the PI2 (R) spacer. We recommend the establishment of a registry for evaluation of future implants. Type of study/level of evidence: Case-series study/level IV