gms | German Medical Science

Objectives/Interrogation: The scapholunate interosseous ligament (SLIL) is the most commonly injured ligament in the wrist. No reconstructive technique has been demonstrated to have better outcomes for a patient with reducible DISI than another. The purpose of this study was to compare the biomechanical and radiographic outcomes of the tri-ligament tenodesis (TLT) [1], Anatomic Front and Back (ANAFAB) reconstruction, and the Reduction and Association of the Scaphoid and Lunate (RASL) for reducible DISI deformity.

Methods: Scapholunate instability and DISI (defined as an absolute increase in RLA>15°) were created in 15 fresh-frozen cadaveric specimens by cutting the SLIL, long radiolunate ligament (LRL), dorsal inter-carpal ligament (DIC) and scaphotrapezo-trapezoidal (STT) ligaments. Specimens were randomized to receive the TLT, ANAFAB (Figure 1) or RASL procedures. Cadaver limbs were mounted onto a biomechanical testing jig in the clenched fist position with attached loads. Fluoroscopic images were taken in standardized PA and lateral positions to measure scapholunate gap (SLG), dorsal scaphoid translation (DST), radiolunate angle (RLA), and scapholunate angle (SLA). The specimens were cycled and compared radiographically in 3 states: intact, all ligaments cut and after reconstruction.

Results and Conclusions: The mean difference between intact and post-reconstruction measurements for RLA was 1.1°, 12° and 16.7° respectively for the ANAFAB, TLT and RASL groups, with a significant difference (Figure 2; p=0.024). The mean difference between the reconstruction and the intact status for SLA was -1° for both RASL and ANAFAB and 8° for TLT, with a significant difference (p=0.012). The mean difference of the DST between intact and reconstruction was 0.63 mm, 0.92 mm and 0.12 mm respectively for ANAFAB, TLT and RASL procedures (p=0.581). Compared with the measurements with all ligaments cut, the ANAFAB reduced the SLG 4.2 mm, the TLT 3.9 mm and the RASL 3.6 mm, with no significant difference (p=0.878). Considering the different radiographic measurements, we noted no significant difference between the 3 techniques in maintaining the reduction after loading (p>0.05).

The ANAFAB procedure offered significantly improved correction of the RLA relative to the modified TLT and RASL procedures. The ANAFAB technique was the only reconstruction that addressed the volar and dorsal extrinsic stabilizers of the proximal carpal row. Further biomechanical studies are needed in order to confirm these results for several wrist positions.