The scaphoid is one of the eight small carpal bones forming the wrist joint, situated on the thumb side of the hand. Due to its position, it is the most frequently fractured carpal bone, often injured during a fall onto an outstretched hand. Palpating the scaphoid for tenderness is a common physical examination technique used to assess for potential injury following trauma. This maneuver helps determine if the underlying bone has been damaged, guiding the next steps in medical assessment.
Understanding the Scaphoid’s Location
To effectively palpate the scaphoid, one must first accurately locate the anatomical snuffbox, a triangular depression on the dorsal aspect of the wrist near the base of the thumb. The scaphoid bone forms the floor of this depression, making it the primary site for examination. This indentation becomes most apparent when the thumb is fully extended, tightening the surrounding tendons.
The borders of this anatomical snuffbox are clearly defined by three tendons that run into the thumb. The medial border, closer to the middle of the wrist, is formed by the tendon of the Extensor Pollicis Longus muscle. The lateral border, closer to the radial side of the wrist, is formed by the paired tendons of the Abductor Pollicis Longus and the Extensor Pollicis Brevis muscles.
The scaphoid bone rests deep within this space, articulating with the radius, the larger forearm bone, and the other carpal bones. This positioning makes it vulnerable to compressive forces during a fall. Identifying the snuffbox correctly ensures that the pressure applied during the examination is directed precisely over the scaphoid’s surface.
Detailed Palpation Procedure
The physical examination begins with proper positioning of the wrist to maximize the exposure of the scaphoid bone. The patient’s hand should be relaxed, and the examiner may gently position the wrist into a slight degree of ulnar deviation. This specific movement shifts the scaphoid slightly outward from under the radius, allowing for a clearer path to its surface.
The examiner then uses the tip of one finger, typically the index or middle finger, to apply pressure directly into the center of the anatomical snuffbox. The goal is to press down through the skin and soft tissues to the underlying bone. The pressure should be firm enough to compress the soft tissues but not so forceful as to cause undue discomfort in an uninjured wrist.
Applying pressure over the floor of the snuffbox allows the examiner to assess the central portion, or waist, of the scaphoid, which is the most common site for a fracture. Palpation in this specific location is considered the most reliable single test for detecting a scaphoid injury. Tenderness elicited here is highly suggestive of a fracture, even if initial X-rays do not show a clear break.
For a more comprehensive examination, it is important to assess other parts of the scaphoid bone. One variation involves palpating the scaphoid tubercle, a bony prominence located on the palm side, or volar aspect, of the wrist near the base of the thumb. This tubercle can be felt just below the crease where the wrist meets the hand. Another technique involves keeping the wrist in maximum flexion to expose the proximal pole, the part of the bone closest to the forearm. A thorough palpation involves checking these multiple areas—the snuffbox, the tubercle, and the proximal pole—to avoid missing a fracture located outside the most common area.
What Tenderness Indicates and Seeking Medical Care
Tenderness directly over the scaphoid during palpation is a significant clinical finding, even if swelling is minimal or absent. This localized pain, particularly after a fall onto an outstretched hand, is strongly correlated with a potential scaphoid fracture. Since the initial absence of a visible fracture on standard X-rays does not rule out the injury, the physical examination finding of tenderness is particularly important.
The unique and precarious blood supply of the scaphoid bone elevates the concern for this injury. Blood vessels enter mainly from the distal end and flow backward toward the proximal pole. A fracture through the waist of the bone can disrupt this flow, leaving the proximal pole without a blood supply. This disruption can lead to avascular necrosis, where the bone tissue dies and may collapse over time, resulting in long-term wrist instability and arthritis. The initial tenderness found during palpation is the first indication that this serious process may be starting.
Any finding of tenderness in the anatomical snuffbox warrants immediate medical attention and further investigation. Healthcare providers will typically immobilize the wrist with a splint or cast, even if X-rays are inconclusive, to protect the bone. Additional imaging, such as a repeat X-ray in seven to ten days, a specialized scaphoid view X-ray, or more advanced modalities like a CT scan or MRI, may be necessary to confirm or rule out a fracture that was initially hidden.