SPECT bone scintigraphy for the assessment of condylar growth activity in mandibular asymmetry: is it accurate?

The comparison of serial radiographs and clinical photographs is considered the current accepted standard for the diagnosis of active condylar hyperplasia in patients with facial asymmetry. Single photon emission computed tomography (SPECT) has recently been proposed as an alternative method. SPECT can be interpreted using three reported methods absolute difference in uptake, uptake ratio, and relative uptake. SPECT findings were compared to those from serial comparisons of radiographs and clinical photographs taken at the time of SPECT and a year later; the sensitivities and specificities were determined. Two hundred patient scans were evaluated. Thirty-four patients showed active growth on serial growth assessment. On comparison with serial growth assessment, the sensitivity and specificity of the three methods ranged between 32.4% and 67.6%, and 36.1% and 78.3%, respectively. Analysis using receiver operating characteristic (ROC) curves revealed area under the curve (AUC) values of <0.58. The average age (mean standard deviation) of patients with active growth was 18.6 +/- 2.8 years, and average growth in the anteroposterior, vertical, and transverse directions was 0.94 +/- 0.91 mm, 0.88 +/- 0.86 mm, and 1.4 +/- 0.66 mm, respectively. With such low sensitivity and specificity values, it is not justifiable to use SPECT in place of serial growth assessment for the determination of condylar growth status.