Background

The anatomy of the scapholunate interosseous ligament (SLIL) has been described qualitatively in great detail, with recognition of the dorsal component's importance for carpal stability. The purpose of this study was to define the quantitative anatomy of the dorsal SLIL and to assess the use of high-frequency ultrasound to image the dorsal SLIL.

Methods

We used high-frequency ultrasound imaging to evaluate 40 wrists in 20 volunteers and recorded the radial-ulnar (length) and dorsal-volar (thickness) dimensions of the dorsal SLIL and the dimensions of the scapholunate interval. We assessed the use of high-frequency ultrasound by comparing the length and thickness of the dorsal SLIL on ultrasound evaluation and open dissection of 12 cadaveric wrists. Student's t test was used to assess the relationship between measurements obtained on cadaver ultrasound and open dissection.

Results

In the volunteer wrists, the mean dorsal SLIL length was 7.5 ± 1.4 mm and thickness was 1.8 ± 0.4 mm; the mean scapholunate interval was 5.0 mm dorsally and 2.5 mm centrally. In the cadaver wrists, there was no difference in dorsal SLIL length or thickness between ultrasound and open dissection.

Conclusions

The dorsal SLIL is approximately 7.5 mm long and 1.8 mm thick. These parameters may be useful in treatment of SLIL injuries to restore the native anatomy. High-frequency ultrasound is a useful imaging technique to assess the dorsal SLIL, although further study is needed to assess the use of high-frequency ultrasound in detection of SLIL pathology.

Background

The goal of this study was to compare the biomechanical stability of a 2.4-mm dorsal spanning bridge plate with a volar locking plate (VLP) in a distal radius fracture model, during simulated crutch weight-bearing.

Methods

Five paired cadaveric forearms were tested. A 1-cm dorsal wedge osteotomy was created to simulate an unstable distal radius fracture with dorsal comminution. Fractures were fixed with a VLP or a dorsal bridge plate (DBP). Specimens were mounted to a crutch handle, and optical motion-tracking sensors were attached to the proximal and distal segments. Specimens were loaded in compression at 1 mm/s on a servohydraulic test frame until failure, defined as 2 mm of gap site displacement.

Results

The VLP construct was significantly more stable to axial load in a crutch weight-bearing model compared with the DBP plate (VLP: 493 N vs DBP: 332 N). Stiffness was higher in the VLP constructs, but this was not statistically significant (VLP: 51.4 N/mm vs DBP: 32.4 N/mm). With the crutch weight-bearing model, DBP failed consistently with wrist flexion and plate bending, whereas VLP failed with axial compression at the fracture site and dorsal collapse.

Conclusions

Dorsal spanning bridge plating is effective as an internal spanning fixator in treating highly comminuted intra-articular distal radius fracture and prevents axial collapse at the radiocarpal joint. However, bridge plating may not offer advantages in early weight-bearing or transfer in polytrauma patients, with less axial stability in our crutch weight-bearing model compared with volar plating. A stiffer 3.5-mm DBP or use of a DBP construct without the central holes may be considered for distal radius fractures if the goal is early crutch weight-bearing through the injured extremity.