Nonunion of Fracture Scaphoid: Foundational Concepts
Scaphoid nonunion is failure of a scaphoid fracture to unite within the expected period, with persistent fracture mobility, a visible fracture gap or sclerosis, and continuing biological or mechanical inability to achieve union. It is clinically important because the scaphoid is the principal link between the proximal and distal carpal rows. Untreated nonunion may progress through altered carpal mechanics to scaphoid nonunion advanced collapse (SNAC) wrist, secondary radiocarpal and midcarpal osteoarthritis, pain, weakness and loss of motion.
Relevant anatomy and vascular basis
The scaphoid is divided into distal pole, waist and proximal pole. Approximately 70–80% of its surface is covered by articular cartilage, leaving limited areas for vascular entry. Its blood supply is predominantly from branches of the radial artery entering dorsally and distally, with retrograde flow toward the proximal pole. Consequently, fractures through the waist or proximal third may interrupt intraosseous vessels supplying the proximal fragment. The proximal pole is therefore particularly vulnerable to avascular necrosis (AVN) and nonunion.
The scaphoid has an important role in carpal stability. A waist fracture with collapse may produce a “humpback” deformity, characterized by flexion of the distal fragment and shortening of the scaphoid. This alters the…