The Use of ^99mTc-MDP Bone Scanning to Assess Facial Bone Growth

DISCUSSION

The ability to predict the cessation of facial bone growth before surgery is crucial in patients with mandibular prognathism, as well as in patients with unilateral condylar hyperactivity (1,2). Various imaging techniques such as hand and wrist radiographs, cephalograms, and ^99mTc-MDP bone scintigraphy are currently used to determine when facial bone growth has stopped, so that surgery can be most effective. Radiographs compare the growth of the hand and wrist with that of the mandible; however, the mandible tends to grow even after the hand and wrist mature. Cephalograms require 2 separate observations, months apart, yet cannot predict future growth (1).

^99mTc-MDP bone scintigraphy is able to view osteogenic activity, allowing for visualization and comparison of the growth of the left and right condyles of the mandible. The condylar region is compared with the lumbar vertebra, and the ratio is determined. Patients with ratios of less than 1 are considered eligible for surgery, but ratios greater than 1 lead to delay of any surgical procedures.

Obtaining a thorough history is important because bone activity can also indicate remodeling after recent trauma. A study performed at Universidade Gama Filho and Hospital Universitário Pedro Ernesto in Rio de Janeiro, Brazil, emphasized the ability of ^99mTc-MDP to visualize the metabolic status earlier than other methods (1). We used the same method and regions of comparison during our study. The ratio determined by selecting regions of interest on the right and left body and rami condyles of the mandibles compared with the L4 vertebra was less than 1; therefore, surgery was a viable option.

Bone scanning is an important technique that detects mandibular growth, and its quantitation aids in deciding the optimal timing for surgery.