Comparative Biomechanical Analysis of Three Ligamentous Reconstruction Techniques for Trapeziometacarpal Joint...

The trapeziometacarpal (TMC) joint is critical for thumb function, and its instability leads to significant disability. While the volar-only Eaton-Littler ligament reconstruction is a classic treatment, its efficacy is debated. Modern techniques like the Zhang method address both volar and dorsal ligaments, but comparative biomechanical data are scarce. This study aimed to biomechanically compare the stability of the traditional Eaton-Littler technique with the Zhang technique and a modified Zhang technique using a palmaris longus (PL) tendon graft.

A descriptive comparative study was conducted on 21 cadaveric specimens from 14 hands. Three techniques were evaluated: Eaton-Littler (n=7), Zhang (n=7), and modified Zhang (n=7). The Modified Zhang technique utilized PL tendon instead of flexor carpi radialis (FCR). Biomechanical testing measured joint displacement under controlled loads (10N, 20N, 30N) in four anatomical directions (dorsal, volar, radial, ulnar). Statistical analysis employed Wilcoxon signed-rank test with significance at p<0.05.

The Eaton-Littler technique demonstrated significantly greater displacement compared to both Zhang methods in dorsal (5.27mm vs 3.75mm vs 3.95mm at 30N; p<0.03), volar (6.29mm vs 5.27mm vs 5.05mm at 30N; p<0.03), and ulnar (5.73mm vs 3.90mm vs 3.68mm at 30N; p=0.018) directions. No significant differences existed between techniques for radial displacement (p>0.05) or between Zhang and modified Zhang methods (p>0.05). The PL and half-slip FCR grafts showed equivalent cross-sectional diameters (2.11mm vs 2.08mm; p=0.499).

Both Zhang and modified Zhang techniques demonstrate superior biomechanical stability profiles compared to the traditional Eaton-Littler procedure. The PL tendon represents a viable alternative graft option with comparable biomechanical properties, offering potential advantages in preserving FCR function.