Lateral deviation of the radius in young animals most often results from which bone growth disturbance?

Lateral deviation of the radius in young animals most often results from which bone growth disturbance?

• A. Premature proximal radius physeal closure
• B. Distal radial fracture
• C. Premature distal ulna physeal closure
• D. Carpal subluxation

Answer: (C)

Unequal growth of paired forearm bones during development can create angular deformities as the limb lengthens. If the distal growth plate of the ulna closes prematurely, the ulna stops lengthening while the radius continues to grow. That mismatch makes the ulna effectively shorter, and the radius must bend to accommodate the new relationship between the two bones at the distal forearm. The result is a bowing of the radius toward the outside of the limb, seen as lateral deviation. Other disturbances, like problems limited to the radius itself or a carpal joint issue, don’t produce this same pattern of radius bowing driven by ulna shortening, so premature distal ulna physeal closure best explains the lateral deviation.

Unequal growth of paired forearm bones during development can create angular deformities as the limb lengthens. If the distal growth plate of the ulna closes prematurely, the ulna stops lengthening while the radius continues to grow. That mismatch makes the ulna effectively shorter, and the radius must bend to accommodate the new relationship between the two bones at the distal forearm. The result is a bowing of the radius toward the outside of the limb, seen as lateral deviation. Other disturbances, like problems limited to the radius itself or a carpal joint issue, don’t produce this same pattern of radius bowing driven by ulna shortening, so premature distal ulna physeal closure best explains the lateral deviation.