Changes in Sagittal Balance of Motion at the Thumb Metacarpophalangeal Joint After Sequential Trapeziectomy, Suspensionplasty, and Extensor Pollicis Brevis Tenodesis: A Cadaveric Study.

BACKGROUND

We hypothesized that hyperextension metacarpophalangeal (MP) thumb deformity may be caused by trapeziectomy alone due to telescoping of the first metacarpal without trapezial support.

OBJECTIVE

To explore the relationship of trapeziectomy with hyperextension thumb MP joint deformity and contribute novel data on the underlying pathomechanics.

METHODS

This basic anatomical research study examined thumb MP joint kinematics at 6 surgical stages in 10 cadaveric specimens: stage 1, baseline; 2, volar plate of the thumb MP joint division; 3, trapeziectomy; 4, Weilby's ligament reconstruction and tendon interposition (LRTI); 5, extensor pollicis brevis (EPB) tenotomy; and 6, MP volar plate reconstruction by tenodesis with EPB. Six infrared cameras were used in a motion capture system to determine three-dimensional angles of the first MP joint during 10 cycles of thumb flexion-extension, measuring angles in maximum flexion and extension and the complete flexion-extension arc.

RESULTS

In comparison to baseline, the angle in extension and MP-ROM were significantly increased after stages 3 (trapezium extraction), 4 (LRTI), and 5 (EPB tenotomy). In comparison to values after stages 3, 4, and 5, the hyperextension was significantly corrected after stage 6 (tenodesis).

CONCLUSIONS

In a cadaveric model of trapeziectomy, secondary thumb column shortening favors an MP joint hyperextension deformity that is not corrected by LRTI or EPB tenotomy and requires a stabilization procedure.