Action affected in BENNET’S fraction of thumb?
**Core Concept**
Bennett's fracture is a type of intra-articular fracture of the thumb's basal joint, specifically involving the first metacarpal bone. This fracture is characterized by an abduction and radial displacement of the metacarpal head, leading to an abnormal alignment of the thumb's joint.
**Why the Correct Answer is Right**
The Bennett's fracture affects the abductor pollicis longus (APL) tendon, which is responsible for thumb abduction and radial deviation. The fracture disrupts the attachment of the APL tendon to the first metacarpal bone, leading to weakness and instability in thumb movements. This is due to the involvement of the joint capsule and surrounding ligaments, which are damaged during the fracture, further compromising the stability of the thumb's basal joint.
**Why Each Wrong Option is Incorrect**
**Option A:** The flexor pollicis longus (FPL) tendon is not directly affected in Bennett's fracture, as it is primarily involved in thumb flexion.
**Option B:** The radial collateral ligament is not the primary ligament affected in Bennett's fracture; the fracture involves the joint capsule and surrounding ligaments.
**Option C:** The palmar cutaneous branch of the median nerve is not directly related to the Bennett's fracture, as it is primarily involved in sensation to the palmar aspect of the thumb.
**Clinical Pearl / High-Yield Fact**
In Bennett's fracture, a key clinical finding is the inability to actively abduct the thumb, which is a result of the disrupted attachment of the abductor pollicis longus tendon.
**Correct Answer: A. Abductor pollicis longus tendon.**