Cadaveric Study of Appropriate Screw Length for Distal Radius Stabilization Using Volar Plate Fixation
We conducted a study to highlight areas of risk with distal radius fixation to prevent occurrence of extensor tendon injury without compromising the security and stability of the fixation.
Twelve cadaveric forearms were used. The volar locking plate was placed to best anatomical and radiologic fit on the distal radius of each arm. All 7 holes in the plate were drilled, and bicortical length was measured using a depth gauge under fluoroscopy to estimate screw lengths. Screws were secured into place, and dorsal prominence was measured.
The central screw positions had the least dorsal screw prominence, mean (SD) of 0.50 (1.06) mm, and were considered low-risk. The radial and ulnar screw positions had more dorsal screw prominence, 3.38 (1.38) mm and 1.03 (1.30) mm, respectively. Although only radial prominence was statistically significant, both radial and ulnar screw positions were considered high-risk and in need of screw length adjustments.
The data suggest that screw length for this plate should be decreased by about 3 mm for the radial positions and by 1 mm for the ulnar positions to decrease the risk for tendon rupture and irritation secondary to dorsal screw prominence.
In fractures with an intact dorsal cortex, standard depth gauges will likely produce appropriate screw length measurements. However, even in this situation, and based on the results reported by Wall and colleagues,12 subtraction of 1 to 2 mm may prove prudent. In cases in which the dorsal cortex is comminuted and screw estimates based on fluoroscopy are used, the lateral image may provide estimates that lead to screw prominence. A 45° supinated view should be used to check screw length for the radial side, the column most at risk. However, comminution may also obscure this view. We cannot comment on that, as the present study did not create comminuted fractures of the distal radius. In addition, the ulnar column posed a lesser but real risk of screw prominence, which must also be accounted for, and typically is not appreciated with alternate views.
Last, use of live fluoroscopy instead of standard anteroposterior and lateral views may prove valuable in assessing hardware placement and screw length in the setting of a comminuted distal radius fracture. Through use of live fluoroscopy, prominent screws, especially those on the radial side, may be identified, and potential tendon injury may be avoided. Keeping in mind the shape of the dorsal aspect of the distal radius should assist surgeons in preventing screw prominence dorsally and limit complications.
