Background
Hairline lowering (HALO) surgery is commonly performed using either a single anterior incision (AI) placed along the hairline or an anterior incision combined with bilateral extensions (BE) oriented anteroposteriorly along the superior temporal lines. The biomechanical implications of these incision designs remain insufficiently defined.
Methods
Cadaveric dissections were performed on five heads. After placement of an AI and subgaleal release, maximal scalp advancement was measured in the midline and along both mid-pupillary lines. Subsequently, bilateral extensions were added, together with additional posterior subgaleal dissection and one additional galeotomy, and measurements were repeated. Statistical analysis compared advancement achieved with each incision design.
Results
The BE design demonstrated greater scalp advancement at all measurement points compared with the AI design. Midline advancement increased by 21% (P = 0.043), right mid-pupillary advancement by 24.29% (P = 0.048), and left mid-pupillary advancement by 28.15% (P = 0.048). The most pronounced qualitative difference was observed at the lateral endpoints of the hairline, where BE allowed substantially greater advancement than AI; however, this observation was not quantitatively measured.
Conclusions
This cadaveric study provides preliminary anatomical evidence suggesting that the BE incision design may allow greater scalp advancement than the AI technique, particularly at the lateral hairline endpoints. These findings should be interpreted with caution given the small sample size and the presence of additional release maneuvers in the BE group. Further clinical studies are warranted to validate these anatomical observations.