A Proximal Row Carpectomy (PRC) is a standard surgical procedure addressing severe wrist pain, typically resulting from advanced arthritis or trauma that has damaged the joint surfaces. It is classified as a motion-sparing salvage procedure, aiming to relieve pain while preserving some movement, unlike a total fusion which eliminates all motion. The primary goal of a PRC is to remove the damaged row of small bones causing painful friction against the forearm bones.
Understanding the Carpal Bones
The carpus, or wrist, is a complex anatomical structure composed of eight small carpal bones. These bones are arranged into two distinct rows, stacked between the forearm bones and the bones of the hand. This organization allows for the wrist’s intricate range of motion.
The row closest to the arm is the proximal row, which includes the Scaphoid, Lunate, Triquetrum, and Pisiform. This row forms the main articulation with the two forearm bones: the radius and the ulna. The radius, the larger of the two forearm bones, bears the majority of the load and forms the primary joint surface.
The second set of bones, positioned closer to the hand, is the distal carpal row. This row contains the Trapezium, Trapezoid, Capitate, and Hamate. These four bones articulate with the metacarpals, the long bones within the palm of the hand.
The Specific Bones Removed in Proximal Row Carpectomy
The Proximal Row Carpectomy procedure involves the surgical removal of the three main articulating bones within the proximal carpal row: the Scaphoid, the Lunate, and the Triquetrum. Removal of these three bones eliminates the source of chronic pain caused by bone-on-bone friction, particularly when cartilage surfaces have deteriorated due to severe arthritis.
The Scaphoid is the largest bone, positioned on the thumb side, and plays a significant role in wrist stability and movement. The Lunate is situated centrally and articulates directly with the radius. The Triquetrum is located on the pinky-finger side and contributes to the joint’s movement and stability.
The removal of these three bones effectively disconnects the main joint surface between the forearm and the wrist complex. The Pisiform, the fourth bone in the proximal row, is typically not removed during a standard PRC. The Pisiform is a small, pea-shaped bone located within a tendon on the palm side of the wrist.
Functional Mechanics of the Reconstructed Wrist
The biomechanical objective of a Proximal Row Carpectomy is to transform the wrist’s anatomy into a functional “neo-joint” that is both stable and pain-free. Removing the proximal row creates a new, structurally simpler articulation between the forearm and the remaining distal carpal row.
The Capitate bone, the largest and most central bone of the distal carpal row, becomes the primary point of articulation with the radius. The head of the Capitate moves into the concavity of the lunate fossa on the end of the radius. This new radiocapitate joint is the foundation for the wrist’s post-operative function.
The Capitate’s smooth, rounded head provides a suitable surface to move against the preserved cartilage of the radius, allowing for motion while avoiding painful contact. Patients can expect a functional arc of motion after the procedure, though the range is often reduced compared to a healthy wrist. Grip strength is typically preserved, often retaining 50 to 68 percent of the strength in the unaffected wrist.