Background: The interfrontal angle (IFA) has been utilized as a surrogate for morphologic assessment of the anterior cranial region in metopic synostosis with success in characterizing presenting severity. Its utility as an outcome measure has not been assessed similarly. In this study, we aimed to determine whether meaningful information relative to shape, and relapse in particular, could be assessed using the IFA.
Methods: Patients with operatively treated isolated metopic synostosis were identified and included based on the availability of "previously obtained" low-dose computerized tomography (CT) scans at (1) preoperative and 2 postoperative (2) postoperative day-3 and (3) 1 year time points. Relapse was calculated as the percentage of the operatively induced change in IFA that was retained after the first postoperative year.
Results: After exclusionary criteria, 19 patients were identified. The mean IFA values at the 3 time points were 119.3° (±9.8), 139.6° (±6.3), and 135.3° (±7.1), chronologically. Of the 19 patients, 14 (73.7%) experienced relapse, with this subgroup averaging 62.4% retention of their surgical change after 1 year. Increased preoperative severity and delayed age at surgical intervention were concurrently associated with an increased occurrence of relapse (P = 0.011). Another model utilizes preoperative IFA to predict the change in IFA that would accompany surgery on a case-by-case basis (P < 0.0001).
Conclusions: (1) Fronto-orbital advancement offers immediate correction in the frontal bandeau. (2) Surgical impact, using fronto-orbital advancement, can be predicted using preoperative severity. (3) A component of postoperative relapse occurs within the frontal bandeau and is detectable at 1 year via the IFA. Exclusively, the IFA cannot characterize holistic postoperative relapse due to its inherent anatomical constraints; this supports the cessation of routine postoperative computerized tomography scans for determining outcomes.