The wrist is a complex and highly mobile joint, crucial for daily activities like writing and lifting. Its intricate structure allows for a wide range of movements, making it susceptible to various injuries and degenerative conditions. It is formed by forearm bones and small hand bones. Understanding their arrangement is important for comprehending wrist function and how medical procedures can restore utility.
Understanding the Wrist’s Carpal Bones
The human wrist contains eight small bones known as carpal bones. These bones are organized into two distinct rows: the proximal row and the distal row. Each row consists of four carpal bones, working together to provide flexibility and a range of motion to the hand.
The proximal row of carpal bones is located closest to the forearm and articulates directly with the radius, one of the two long bones in the forearm. This row includes the scaphoid, lunate, triquetrum, and pisiform bones. The scaphoid is the largest bone in this row, while the lunate is often described as moon-shaped, and the triquetrum is pyramid-shaped. The pisiform is a small, pea-shaped bone situated on the palmar surface of the triquetrum.
The distal row of carpal bones lies further down the hand, connecting the wrist to the metacarpal bones, which are the long bones of the palm. This row comprises the trapezium, trapezoid, capitate, and hamate bones. The capitate is notably the largest of all the carpal bones. The collective arrangement of these carpal bones forms an arch, which contributes to the stability and function of the wrist.
The Proximal Row Carpectomy Procedure
A proximal row carpectomy (PRC) is a surgical procedure that involves the removal of specific carpal bones from the wrist to alleviate pain and restore function. This operation directly addresses conditions where the bones of the proximal carpal row have become severely damaged or arthritic. The surgeon explicitly removes the scaphoid, lunate, and triquetrum bones during a PRC. These three bones constitute the primary load-bearing components of the proximal row.
This procedure addresses severe wrist pain and dysfunction, often due to significant cartilage degradation. Common indications include advanced arthritis, such as scapholunate advanced collapse (SLAC) wrist and scaphoid nonunion advanced collapse (SNAC) wrist, and Kienböck’s disease, which involves lunate bone collapse. Certain complex wrist fracture-dislocations can also necessitate a PRC. The surgery’s primary goal is to eliminate painful bone-on-bone friction by removing damaged bones, creating a new, more functional joint surface for substantial pain relief.
Life After a Proximal Row Carpectomy
After a proximal row carpectomy, the wrist undergoes a significant anatomical change, leading to a new functional articulation. With the scaphoid, lunate, and triquetrum bones removed, the capitate bone from the distal carpal row now directly articulates with the radius, the larger forearm bone. This creates a new joint, effectively converting the complex native wrist joint into a simpler hinge-like mechanism.
Patients experience a notable reduction in pain following the procedure, a primary objective of the surgery. While the wrist’s full range of motion may be somewhat reduced, a functional range of motion is preserved. Studies indicate patients achieve around 50% of normal movement in flexion and extension. Grip strength is also preserved, often ranging from 50% to 71% of the unaffected side. This new joint configuration allows for continued wrist movement, providing a functional outcome for individuals with previously debilitating wrist conditions.