The scaphoid is a small, boat-shaped bone located on the thumb side of the wrist, and it is the most frequently fractured of the eight carpal bones. This injury requires specific management because the scaphoid has a precarious blood supply, especially to the portion closest to the forearm. This limited blood flow makes the bone susceptible to delayed healing or failure to heal, known as nonunion. Nonunion can lead to long-term wrist dysfunction, so seeking prompt medical attention is crucial for the best possible outcome.
Recognizing and Diagnosing the Injury
A scaphoid fracture often occurs after a fall onto an outstretched hand, but the resulting symptoms can be subtle and sometimes mistaken for a simple wrist sprain. The primary sign is pain and tenderness when pressure is applied to the anatomical snuffbox, the triangular depression on the back of the hand at the base of the thumb. Swelling on the thumb side of the wrist and pain with gripping or pinching are also common.
Diagnosis typically begins with X-rays, which include specialized views of the scaphoid bone. Up to 20% of scaphoid fractures, sometimes called “occult fractures,” may not be visible immediately after the injury. If a fracture is suspected despite negative X-rays, the standard protocol involves immobilizing the wrist and repeating the X-ray examination after 10 to 14 days. Advanced imaging, such as MRI or CT scans, may be used for a definitive and earlier diagnosis, confirming the fracture and assessing its stability.
Conservative Treatment Options
Non-surgical management is the initial approach for stable, non-displaced scaphoid fractures, especially those located in the middle (waist) or the portion closest to the thumb (distal pole). Healing potential is higher in the distal pole due to its better blood supply. Treatment involves strict immobilization in a long or short arm thumb spica cast, which includes the thumb, to stabilize the fracture fragments.
The duration of immobilization varies significantly based on the fracture’s location and individual healing rates, typically ranging from 6 to 12 weeks or more. Fractures in the waist may require 8 to 12 weeks for union, while those in the proximal pole often require 12 to 24 weeks. Follow-up X-rays are taken periodically to monitor the progression of bone healing. Even for fractures with moderate displacement (0.5 mm to 1.5 mm), a prolonged period of casting may be pursued before considering surgery.
Surgical Repair Procedures
Surgery becomes necessary for scaphoid fractures that are displaced, unstable, or fail to heal after conservative treatment. A fracture is considered unstable if the fragments are separated by more than 1 millimeter or if there is excessive angulation. Early surgical fixation may also be considered for some non-displaced fractures to accelerate the return to activity and reduce the risk of nonunion.
Internal fixation is the main surgical technique, involving stabilizing the fracture fragments with specialized screws or wires. A headless compression screw is often used, inserted across the fracture site to hold the pieces together and promote bone union. Fixation can be performed through a small percutaneous incision or a larger, open incision, depending on the fracture’s complexity and location.
In cases of established nonunion or delayed healing, the surgeon may perform a bone grafting procedure along with internal fixation. Bone graft material, often taken from elsewhere in the body, is packed into the fracture gap to stimulate new bone growth. For nonunions complicated by avascular necrosis, a vascularized bone graft, which includes a small attached blood vessel, is often used to restore blood flow and enhance healing.
Recovery, Rehabilitation, and Potential Complications
After the period of cast immobilization, physical therapy is initiated to restore function to the wrist. The initial focus of rehabilitation is on gentle active range-of-motion exercises for the wrist and thumb to combat stiffness resulting from prolonged immobilization. As healing progresses, the therapy program advances to include strengthening exercises for the surrounding wrist muscles.
Despite appropriate treatment, the unique anatomy of the scaphoid bone makes it prone to two specific complications. Nonunion, which affects 5% to 15% of scaphoid fractures, occurs when the bone pieces do not fuse together. This complication is often addressed with surgery and bone grafting.
The second major risk is avascular necrosis (AVN), where a portion of the bone dies due to the loss of blood supply. This occurs more frequently with fractures of the proximal pole, as the injury can sever the main blood vessels entering the bone. If left untreated, both nonunion and AVN can eventually lead to progressive wrist arthritis and loss of mobility.