Retrograde Blood Supply of the Scaphoid
A missed or undertreated scaphoid fracture can cut the proximal pole off from its blood supply and leave a young patient with a nonunion that turns into wrist arthritis.
Key terminology
- Scaphoid
- This boat-shaped carpal bone links the 2 rows of carpal bones on the thumb side of the wrist. It is the most commonly fractured carpal bone.
- Proximal pole
- This end of the scaphoid sits against the radius and lunate, farthest from where its vessels enter. Its blood arrives only by backward flow from the middle of the bone.
- Scaphoid waist
- This narrow middle third of the scaphoid lies between the proximal and distal poles. It is the most common site of scaphoid fracture.
- Avascular necrosis (AVN)
- Bone dies after losing its blood supply. On radiographs the dead fragment looks whiter (sclerotic) than the bone around it.
- Scaphoid nonunion advanced collapse (SNAC)
- This wrist arthritis follows an untreated scaphoid nonunion. It starts between the radius and scaphoid and spreads to the rest of the wrist over years.
- Anatomic snuffbox
- This hollow on the back of the wrist at the base of the thumb lies between the thumb extensor tendons. The scaphoid forms its floor, so tenderness here suggests a fracture.
- Thumb spica splint
- This splint holds the wrist and extends along the thumb to the thumb joint. It is the standard way to immobilize a suspected scaphoid fracture.
Takeaways
- Radial artery branches entering the dorsal ridge supply 70-80% of the scaphoid, including the entire proximal pole. The vessels enter near the middle of the bone and flow backward to the proximal pole. Volar branches at the distal tubercle supply the remaining 20-30%. The finding comes from injection studies of 15 cadaver wrists (Gelberman and Menon, J Hand Surg Am 1980;5:508-513, PMID 7430591).
- Micro-CT found the dorsal ridge network feeds an average of 83% of scaphoid volume. All 13 specimens received inflow at the dorsal ridge, and 1 had no vessels at the tubercle at all. An earlier cadaver study by the same group confirmed the 70-80% dorsal share. Slender scaphoids had a weaker internal network than full ones (Morsy et al, J Hand Surg Am 2019;44:928-938, PMID 31543293; Botte et al, J Hand Surg Am 1988;13:216-220, PMID 3351245).
- The more proximal the fracture, the more of the scaphoid is cut off from its 1 dorsal source. A scaphoid waist fracture can split the proximal fragment from the dorsal ridge vessels. A proximal pole fracture leaves the small proximal fragment with almost no blood supply. Avascular necrosis (AVN) and nonunion both follow that loss of flow (Gelberman and Menon, J Hand Surg Am 1980;5:508-513, PMID 7430591).
- 34% of proximal pole fractures treated without surgery progress to nonunion. The relative risk of nonunion was 7.5 compared with more distal fractures also treated in a cast. Only 67 of 1,147 casted fractures (5.8%) were proximal. Studies defined the proximal pole inconsistently, and the authors proposed the proximal fifth of the bone (Eastley et al, J Hand Surg Eur Vol 2013;38:888-897, PMID 22736744).
- 31 of 32 untreated scaphoid nonunions (97%) older than 5 years had developed arthritis. Arthritis starts between the radius and scaphoid and then spreads through the wrist, the pattern called scaphoid nonunion advanced collapse (SNAC). In another series, radioscaphoid arthritis appeared at a mean of 17.0 years and generalized wrist arthritis at 31.6 years. A French series of 52 cases reached the same conclusion (Ruby et al, J Bone Joint Surg Am 1985;67:428-432, PMID 3972868; Mack et al, J Bone Joint Surg Am 1984;66:504-509, PMID 6707028).
- Anatomic snuffbox tenderness was 100% sensitive and only 9% specific in 215 patients. Combining it with scaphoid tubercle tenderness and pain on thumb compression raised specificity to 74% without losing sensitivity. A meta-analysis found snuffbox specificity ranged from 3% to 98% across studies, too varied to pool (Parvizi et al, J Hand Surg Br 1998;23:324-327, PMID 9665518; Mallee et al, J Hand Surg Am 2014;39:1683-1691, PMID 25091335).
- Occult fractures made up 33% of confirmed scaphoid fractures in one Edinburgh series. These fractures did not show on the first radiographs. Of 537 referrals, 76% never proved to have a fracture, so many wrists were splinted without need. The authors favored early MRI over repeated weeks of empiric immobilization in a thumb spica splint (Burns et al, Scott Med J 2013;58:143-148, PMID 23960052).
- Casting and early surgery gave the same wrist scores at 52 weeks for scaphoid waist fractures displaced 2 mm or less. In SWIFFT, 14% of surgery patients had a potentially serious surgical complication vs 1% after casting. A 2026 Chinese registry emulation of 6,769 patients found surgery halved nonunion (8.4% vs 17.5%) with a functional gain below the usual clinically important threshold (Dias et al, Lancet 2020;396:390-401, PMID 32771106; Zhang et al, J Am Acad Orthop Surg 2026;34:e2173-e2185, PMID 42384474).