Incision orientation and scar formation in the shoulder area: a prospective multicenter study

Abstract Optimal skin incision orientation in the shoulder remains debated: textbook guidelines recommend horizontal incisions, while the intraoperative pinch test suggests an upright orientation, and no consensus exists among tension-line concepts such as Langer’s, Kraissl’s, or more recent ones. In this prospective multicenter comparative study with partial randomization and blinded photographic assessment, we evaluated scar formation following horizontal, upright, and oblique incisions at 44 shoulder excision sites from 38 patients across three German centers (2020–2022), using the Patient and Observer Scar Assessment Scale (POSAS) at 3 and 6 weeks. For the primary endpoint, the 6-week observer-reported overall POSAS score, no significant differences were observed between orientations. In exploratory analyses, upright incisions were among the best-rated by patients and observers at 6 weeks and showed significant improvement over time in thickness, elasticity, and vascularity, while oblique incisions showed significant pigmentation improvement; horizontal incisions did not improve. Subregion analyses showed higher stiffness and thickness scores for upright incisions, and worse overall scores for oblique incisions, in the lateral versus medial subregion. As the primary endpoint was non-significant, these exploratory findings should be regarded as hypothesis-generating, positioning upright incisions as a promising candidate for early scar improvement warranting confirmation in larger, adequately powered studies.