Final answer:
While 2 mm of shortening in a metacarpal fracture is associated with extensor lag, the exact degree of lag varies and requires an orthopedic evaluation to determine the functional deficit.
Step-by-step explanation:
In the context of metacarpal fractures, 2 mm of shortening is typically associated with a certain degree of extensor lag at the metacarpophalangeal joint. This joint articulates between the distal end of a metacarpal bone of the hand and a proximal phalanx bone of the thumb or finger. An extensor lag implies that there is a loss of full extension in the affected digit.
The specific degree of extensor lag can vary depending on several factors such as the location of the fracture, individual patient anatomy, and the exact metacarpal involved. However, extensor lag is generally understood to increase with greater shortening of the metacarpal bone. Unfortunately, there isn't a universally accepted number in degrees of extensor lag directly correlated with 2 mm of shortening. The clinical manifestation needs to be assessed on an individual basis, and an orthopedic evaluation is required to determine the extent of the functional deficit.
Physical therapy and possible surgical intervention may be needed to address the extensor lag. An exact degree can't be provided without further clinical assessment, as it can be influenced by the muscles and tendons involved, such as those responsible for abduction and flexion of the fingers at the metacarpo-phalangeal joints.