Upper extremity fractures are among the most common of the extremity injuries with carpal fractures accounting for 18 percent of hand fractures and 6 percent of all fractures [1,2]. Of these, fractures to bones of the proximal row are most frequent. Lunate fractures occur less often than fractures of the scaphoid with a reported incidence of 0.5 to 6.5 percent of all carpal fractures . Fractures of the lunate, particularly those that are not recognized and treated appropriately, may lead to osteonecrosis, also known as Kienböck's disease. Thus, detection of lunate fractures and appropriate early management are important goals that can reduce the likelihood of this complication.
This topic will review issues related to lunate fractures in adults. A general overview of carpal fractures is presented separately. (See "Overview of carpal fractures".)
PERTINENT ANATOMY AND RISK FACTORS
The anatomy of the wrist is reviewed in detail separately; pertinent details about lunate anatomy are described below. (See "Anatomy and basic biomechanics of the wrist".)
The lunate is well protected as it sits in a sulcus on the distal radius (lunate fossa) (image 1). The lunate can be appreciated by palpation on the dorsum of the wrist just distal to the radius and in line with the middle finger. Another landmark that can help to identify the location of the lunate is Lister's tubercle, a longitudinal bony prominence of the distal radius that is located just proximal to the lunate. The lunate is made more prominent in this location with volar flexion of the wrist.
The bone receives its blood supply on both the volar and dorsal aspects . While 80 percent of lunates possess a dual arterial source, the other 20 percent have a single source leading to a high incidence of ischemic bone changes following fracture. Isolated acute fracture of the lunate is an uncommon occurrence and may go unrecognized, possibly resulting in avascular necrosis, a condition known as Kienböck’s Disease (though this condition is thought to be multi-factorial and usually occurs in the absence of acute trauma) . Associated risk factors include occupations or sports involving repetitive pressure to the base of the hand with the wrist in extension (eg, gymnast, jack hammer operator), and those with ulnar shortening relative to the length of the radius, a condition referred to as "ulna minus variance" . (See "Distal radius fractures in adults", section on 'Anatomic landmarks and measurements'.)