OTA 2012 Posters

Scientific Poster #100 Upper Extremity OTA-2012

Dorsal Radial Blind Spot

Andrew K. Brown, MD; Howard Roth, MD; David A. Fuller, MD;
Cooper University Medical Center, Camden, New Jersey, USA

Background/Purpose: Management of distal radius fractures has been an ongoing evolution since before Colles first described the injury in 1814. Most recently that evolution has given rise to a trend in volar plating. The advantages afforded by this new technology (rigid stabilization, early motion, and fixation of comminuted or osteoporotic bone) are not without risk of certain novel complications. One of the most widely reported complications associated with volar plates, it seems, is extensor tendon injury. The etiology of this injury can be varied. The very nature of the fracture may itself cause injury to the extensor tendons; however, the more concerning causes of these injuries for the practicing surgeon are those that are iatrogenic. Numerous case reports and retrospective studies have shown that prominent screws extending beyond the dorsal cortex can cause acute rupture, attritional rupture, or tenosynovitis. From retrospective data it can be estimated that extensor tendon complications occur between 3% and 5% of the time. A number of anatomic factors contribute to the incidence of these complications. First, the extensor tendons sit approximately 1 mm from the dorsal cortex of the distal radius. Thus a screw with even the slightest protrusion can injure the extensors. Secondly, the dorsal cortex is exceedingly thin and is often comminuted, making accurate measurement of screw length difficult. Lastly, the geometric shape of the distal radius makes it nearly impossible to judge screw position on lateral radiographs or intraoperative fluoroscopy. While this phenomenon is not new, it has as yet to be anatomically quantified. It is with this in mind that we set about to objectively describe the anatomy of the dorsal radius with the hypothesis being that there exists a consistent extensor sulcus on the dorsal aspect of the radius, but that the sulcus depth varies on an individual basis. For purposes of this study, we refer to this sulcus as the dorsal radial blind spot given the inability to detect the sulcus on standard radiographs.

Methods: 61 consecutive wrist MRI studies performed for any reason were analyzed. Skeletal immaturity and fractures or bone tumors distorting the anatomy were the only exclusion criteria. Using axial views, the dorsal extensor compartment ulnar to Lister’s tubercle was evaluated. Using the axial cut with the maximum sulcus depth, a line was drawn from the apex of Lister’s tubercle to the dorsal ulnar corner of the radius. Measurement was then made from this line to the deepest point in the sulcus and recorded as sulcus depth.

Results: 61 MRI scans were evaluated (33 female, 28 male) ranging in age from 12 to 65 years. The average depth of the sulcus was 1.3 mm (range, 0.0-3.1 mm). The average sulcus depth for females was 1.34 mm and for males was 1.25 mm. The sulcus measured ≥2 mm in 13% (8 of 61) of the wrists studied.

• The FDA has not cleared this drug and/or medical device for the use described in this presentation   (i.e., the drug or medical device is being discussed for an “off label” use).  ◆FDA information not available at time of printing. Δ OTA Grant.