[Isis(®) trapeziometacarpal prosthesis in basal thumb osteoarthritis: 30 months follow-up in 30 cases].

OBJECTIVES: The goal of our work was to evaluate the results of the Isis(®) trapeziometacarpal prosthesis.

METHODS: Our retrospective study included 26 patients, 30 prosthesis. The mean follow-up was 30 months. Preoperatively, the pain was 8.1 out of 10, the QuickDASH was 68.5 and the average Kapandji score was 7.8. The Dell's stage was 2.3. The prosthesis used was hybrid: the trapezial cup was cemented in 90% of cases, and the metacarpal stem was cementless.

RESULTS: Eighty-seven percent of patients were satisfied or very satisfied. At last follow-up, the pain was 3.4 out of 10, the QuickDASH was 37.8, and the average Kapandji score 9.1. The range of motion in flexion-extension and abduction-adduction were respectively 30.5° and 31.7±11°. The strength of the key-pinch, pulp-pinch and grasp averaged 75% of the contralateral side. On radiologic review, the rate of radiolucent lines was 20%, and the loosening or non-osteointegration rate 10%. No dislocation was noted. One surgical revision was necessary for symptomatic metacarpal non-osteointegration. The survival rate of the prosthesis was 93% at 42 months.

DISCUSSION: Clinical results are good. However, the rate of abnormal radiographic images (30%) at 30 months follow-up must incite caution. Although these prosthetic loosenings seem to be less symptomatic, a longer follow-up is necessary to assess the sustainability of clinical results and the future of these periprosthetic radiolucent lines. This led us to change our practice to using noncemented prostheses from now on.