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Micro-CT Study of the Intraosseous Vascularity of the Scaphoid
Mohamed Morsy, MD1,2; Nick A van Alphen, MD1; Alexis T Laungani, MD1, Assaf Kadar, MD1; Steven L Moran, MD1
1Mayo Clinic, Rochester, MN; 2Assiut University, Assiut, Egypt

Introduction: Avascular necrosis of the proximal pole of the scaphoid is a commonly anticipated complication following scaphoid fractures. The purpose of this study was to use micro-CT to demonstrate the intraosseous vascularity of the scaphoid within a three dimensional orientation to identify areas of greatest perfusion, and define vascular "safe-zones" for surgical intervention.

Methods: Twelve upper extremities were injected with a lead-based contrast agent (Microfil MV-117, Flow Tech, Carver, MA, USA) under a physiologic pressure of 140 mmHg, monitored by a pressure monitor. The Scaphoids were harvested and scanned using a micro-CT scanner. The intraosseous vascularity was incorporated into a 3D rendering (figure 1). Vessel number, diameter, distribution and pattern were evaluated and analyzed.

Results: Four scaphoids (33.33%) received one vessel to the proximal pole and waist. Five (41.67%) received two vessels and three (25%) received three vessels. Those vessels entered the scaphoid at the dorsal ridge proximal to the level of the mid-waist in three specimens (25%), at the level of the mid-waist in six (50%) and distal to the level of the mid-waist in three (25%). As for the distal pole, three specimens (25%) received one vessel to the distal pole, five (41.67%) received two vessels and four (33.33%) received three vessels. Nutrient vessels entered the distal pole from the volar side in five specimens (41.67%), from the dorsal side in one (8.33%) and from both the volar and dorsal side in six (50%). A vascular density 3D model was created by mirroring the intraosseous vascularity of all the twelve specimens onto one image (figure 2). This showed the areas of potential vascularity, and was used to suggest an optimal position for instrumentation of the scaphoid respecting the intraosseous vasculature (Figure 3).

Discussion and Conclusion: Results of this study suggest that the scaphoid's proximal pole and waist receive vascularity exclusively from vessels entering through the dorsal ridge, which conforms to the data from previous studies. However, the distal pole showed variability in the vessel entry, being exclusively volar, dorsal or from both sides. The generated 3D intraosseous vascular model allowed us to suggest a "safe-zone" for surgical intervention and instrumentation. The results of this study suggest screw placement slightly ulnar and dorsal to the long axis of the scaphoid. Figure 1

Figure 2

Figure 3

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