Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Background: The medial sural artery perforator (MSAP) flap has gained recent popularity for head and neck reconstruction. It carries advantages including a thin, pliable skin paddle, favorable pedicle length, the capacity for a chimeric muscle component from the medial gastrocnemius (MG), and low donor site morbidity. Previous work by Dusseldorp et al. classified MSAP vascular anatomy according to the arterial branching pattern and height (Type I: single branch, Type IIa: dual branching pattern with take-off above tibial plateau, Type IIb: dual branching pattern with take-off below tibial plateau, Type III: 3 or more branches).
Objective: To delineate the vascular anatomical branching pattern characteristics of the MSAP flap and underscore the importance of pre-operative computed tomography angiogram (CTA) imaging in perforator selection.
Methods: A retrospective analysis was conducted of all patients who had underwent CTA imaging for use in head and neck reconstructive surgery at our institution between 2016-2021. MSAP branching patterns were classified according to Dusseldorp et al. (2014). Additional data was collected on visibility of MSAPs on Maximum Intensity Projection (MIP) reformats, dominance of MSA branches, and vessel depth at the widest portion of the MD. Statistical analyses included Pearson’s chi-squared test for comparing branching pattern and dominant branch type between Type IIA & Type IIB, and Kruskall-Wallis tests for the association between branching pattern and perforator depth at the widest part of the MG.
Results: A total of 83 patients and 166 potential lower extremity scans met inclusion criteria. From this initial cohort, 13 scans were excluded due to missing CTA scans or radiologic artifact from knee replacements (7.8%), with final inclusion of 153 scans. Type IIA branching type was the most prevalent (41.3%), followed by Type III (17.4%), Type IIB (15.6%), and Type I (15.0%). There were 4 “not further classified” (NFC) scans (2.4%) that did not fit any criteria. Overall, branch dominance was observed in 66% of cases, with the lateral-most MSA branch most frequently dominant (61%) compared to the medial (28%) and middle (11%) branches. The average MSAP depth at the widest part of the MG was 8.8 millimeters (mm), which was similar across branching patterns: Type I (8.5 mm), Type IIA (8.5 mm), Type IIB (8.7 mm), Type III (9.9 mm), and NFC (9.3 mm). Perforators were appreciated in 51% of MIP scans. Pearson’s chi-squared test demonstrated p-value of 0.0015 at α < 0.05. Kruskall-Wallis tests showed a p-value of <0.0001 at α < 0.05.
Conclusions: Lower extremity CTA provides useful information that may facilitate MSAP flap harvest. The Type IIA branching pattern was the most common. The lateral MSA branch was most often dominant. There appears to be a relationship between distribution of dominant branch and branching pattern type between the Type IIA & Type IIB groups, with the former favoring lateral branch dominance and the latter favoring medial branch dominance. There was also significance demonstrated between branching pattern and average MSAP branch depth at the widest part of MG, which may suggest that certain branching morphologies may be favorable for perforator access.