Introduction

The Medial femoral trochlea (MFT) flap is a motion preserving option for treating scaphoid proximal pole nonunion. Although this technique requires resecting a substantial portion of the scapholunate interosseous ligament, the intercarpal angular relationships are preserved. Studies have demonstrated that this is due to the reconstruction with a flap that is larger than the resected nonunited proximal scaphoid.   The technique of purposeful expansion of the scaphoid height has been termed scaphoid overstuffing. This study was to characterize the effect of overstuffing on force transmission across the scaphoid and lunate facers of the radius. 

Methods

• 11 fresh, frozen cadaveric specimens; no evidence of injury or wrist disease

• Exposure was via a dorsal approach

• Pressure analyzed by electronic pressure sensors

• Wrists were evaluated in three different states

• Native

• Scapholunate dissociation (SLD)

• Overstuffed (OD)

• Pressures were taken in 30 degrees of flexions, full wrist extension, 30 degrees of extension and fist clenched

• Pressure measured in kPa 

• Contact areas measured in mm2

• One-way ANOVA for comparison of groups

Results

In all functional positions the overstuffed state had higher peak pressures across the scaphoid facet than the native state.

• 30 degrees flexion (OS 383±221 kPa, P=0.033),

• Full wrist extension (OS 1068±767 kPa, P=0.022)

• 30 degrees wrist extension (OS 880±518 kPa, P<0.001)

• Clenched fist (OS 1040±736 kPa, P=0.02)