A five-year radiostereometry study of cup fixation and implant survival in 484 Moovis trapeziometacarpal arthroplasties

INTRODUCTION: The primary cause of revision of trapeziometacarpal arthroplasty limiting the implant survival has been aseptic cup loosening. Radiostereometry is a precise method to evaluate implant migration as a surrogate marker for aseptic implant loosening and later revision. The aim of this prospective single-centre cross-sectional cohort study was to evaluate fixation of trapeziometacarpal cups using radiostereometry, report clinical and patient reported outcomes at 5 year follow-up, and assess the complications and survival rate of the Moovis cup with up to 9 years of follow-up. METHODS: Four-hundred and eighty-four conical press-fit dual-mobility Moovis trapeziometacarpal implants were inserted in 407 patients, with a mean age of 59 years (range 43-80). Tantalum beads were inserted in the trapezium during index surgery. Radiostereometric images at 3 weeks, 3 months, 1 year, 2 years and 5 years after the index surgery were used to measure cup migration. Clinical and patient reported outcomes were recorded for 5 years. The cumulative implant survival until 9 years was analysed using the Kaplan-Meier method. RESULTS: Cup migration was 0.28 mm (95% CI: 0.25 to 0.32 mm) total translation at the 3 month follow-up and remained stable until the 5 year follow-up. Females had 0.15 mm (95% CI: 0.06 to 0.24 mm) more cup migration (total translation) than males at the 5 year follow-up. Grip strength, resting and activity pain, and Quick DASH score showed clinically relevant improvement at 1 year and remained stable until the 5 year follow-up. Medium-term patient satisfaction was 96%, and willingness to repeat the procedure was 96%. The 9 year cumulative implant survival rate was 98% for cup removal owing to aseptic loosening and 87% for removal/exchange of any implant component. CONCLUSION: Stable cup fixation and high patient satisfaction until 5 years combined with good 9 year survivorship for Moovis press-fit cups favour its use in the treatment of trapeziometacarpal osteoarthritis. Although these results cannot be directly extrapolated to other trapezial cups, they suggest that similar press-fit conical trapezial cup designs may also provide good fixation and favourable clinical outcomes in the treatment of painful trapeziometacarpal joint osteoarthritis, in patients between the ages of 40 and 80 years. LEVEL OF EVIDENCE: Level II.