Influence de l’anatomie de la surface articulaire proximal du trapèze (PAST) et de la surface articulaire trapézoïdienne du trapèze (TRAST) sur le placement de la cupule durant l’arthroplastie trapézo-métacarpienne

Abstract

Trapeziometacarpal prosthesis is one of the surgical options to address trapeziometacarpal osteoarthritis. Several authors reported the importance of the position of the cup and of bone stock to minimize the risk of loosening. Recenlty, Athlani et al. argued that the cup should be placed in the middle of the width of the trapezium. The senior author of the present study observed that placing the cup in the middle of trapezial width is not always possible, due to impingement (early contact) between the cup and the trapezoidal articular surface of the trapezium (TRAST), especially when trapezial height is low. The objective of the present study was to analyze the influence of the proximal articular surface of the trapezium (PAST) and TRAST anatomy on cup placement, in order to improve preoperative planning for trapeziometacarpal arthroplasty.

The influence of the anatomy of the PAST and the TRAST on cup placement during trapeziometacarpal arthroplasty was retrospectively evaluated on 56 preoperative anteroposterior radiographs of patients who underwent surgery for trapeziometacarpal osteoarthritis. The percentage coverage of the prosthetic cup by the PAST and the available height of the trapezium were calculated. The available height of the trapezium corresponds to the trapezium height after the bone cut at the ulnar edge of the proximal end of the prosthetic cup; it is the smallest available height of the trapezium witch was calculated considering the anatomy of the PAST and TRAST, with the cup placed in the middle of the width of the trapezium.

In 39% of cases, there was a significant difference (up to a mean 4.5 mm, P < 0.001) between the radial height of the trapezium (which is usually considered) and the available height of the trapezium.

The anatomy of the PAST and the TRAST has an impact on the placement of the prosthetic cup when trapezium height is low. The results of the present study suggest that these considerations must be known by all operators performing trapeziometacarpal arthroplasty; that lateralization, implant suspension, or surgical alternatives should be considered to prevent several intra- and postoperative surgical complications.