This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Commonest location of aneurysmal bone cyst is: September 2006 
Select and explain. 
A. Femur, B. Pelvis, C. Veebrae, D. Tibia
D: Tibia
Answer: D: Tibia 
Explanation: Ans. D: Tibia Regarding the location of the aneurysmal bone cyst, any bone may be affected. Approximate frequencies by site are: Skull and mandible (4%) Spine (16%) Clavicle and ribs (5%) Upper extremity (21%) Pelvis and sacrum (12%) Femur (13%) Lower leg (24%) Foot (3%) Sho tubular bones are less frequently affected and are involved in about 10% of cases. Spinal involvement demonstrates a predilection for the posterior elements. In decreasing order of frequency, the following pas of the spine are involved: cervical, thoracic, lumbar. Contiguous veebrae may be involved in 25% of cases. The cyst involves the diaphysis in isolation in about 8% of cases