[Moje prosthesis for the proximal interphalangeal joint]

The purpose of this study was to find out if the Moje implant made of ceramic material can fulfil the clinical expectations that are expected in a replacement of the proximal interphalangeal finger joint (PIP joint). The performance was compared to the results achieved with hands that did not undergo surgery.

From January 2001 to March 2005 15 patients suffering from primary arthrosis received a total of 21 Moje implants as PIP joint replacements. Computer-assisted data were collected including postoperative range of movement (in both hands), strength, pain reduction, patient satisfaction and number of complications.

The average range of motion in PIP joints replaced by the Moje implant was 18.5 degrees (minimum 7 degrees lack of extension to 69 degrees flexion) which correlates to 26% of the ROM of the other hand side). The proportion of pinch strength "thumb opposition to index finger" of the hand that underwent surgery compared to the other side was 56%. Power achieved with the Jamar dynamometer was 94.2% of that, of the non-operated hand. 80% of the patients stated an improvement of their pain situation (more than 2 points on a VAS of 1-5). Most patients were well satisfied with the outcome of the surgery. There was a need for 13 re-operations in 9 fingers. The main problems were loosening of the proximal implant, with subluxation and fractures of the cortical bone.

The Moje ceramic implant does not fulfil the published ideal attributes for a PIP joint replacement as shown in the clinical results. Even a modification of the prosthesis design in 2004 has not diminished the deficits in range of motion and stability. The implant in its present design shows neither the required performance, nor the ideal attributes needed for an adequate PIP joint replacement.