Characteristics of the Gantzer muscle and implications for its use as a tendon-graft source in upper extremity reconstruction

Background

The Gantzer muscle is an anatomical variant muscle that functions in flexion of the volar forearm. The prevalence and laterality of this muscle has been studied more recently in the literature. This study aimed to determine the prevalence and size of this muscle and tendon.

Methods

This was an observational study done from September 2021 to January 2022 at the University of North Texas Health Science Center in Fort Worth, Texas. Cadaveric dissection was conducted in the Department of Physiology and Anatomy. 50 pairs for a total of 100 forearms were dissected bilaterally in cadavers comprising 17 females (34 %) and 33 males (66 %) to identify the Gantzer muscle. The mean age at death was 68.8 years of age (range 40–91 years). When present, the dimensions of each Gantzer tendon were measured in millimeters using digital calipers. As a study of cadaveric specimens, this study was exempt from Institutional Review Board (IRB) approval.

Results

The Gantzer muscle was present in 62 of the 100 forearms (62 %). All 62 Gantzer muscles originated from flexor digitorum superficialis (FDS) (100 %). Of the 62 Gantzer muscles, 42 inserted distally into flexor pollicus longus (FPL) (72.5 %), while the remaining 17 muscles inserted distally into flexor digitorum profundus (FDP) (27.5 %). The tendons inserting into FDP had an average length of 65.495 mm, while those inserting into FPL had an average length of 16.353 mm (p = 0.002). The Gantzer muscle was present in 24 of the 33 male specimens (72.7 %) and 13 of the 17 female specimens (76.4 %). Of the 62 Gantzer muscles, 50 were present bilaterally (80.6 %), and there was no significant difference in bilateral occurrence between sexes (p = 0.189).

Conclusions

Our results suggest that the Gantzer muscle may be of sufficient size and present commonly enough in the general population to be considered as an alternative graft source for certain upper extremity reconstruction procedures in place of, or in addition to, palmaris longus, extensor toe tendons, and other commonly used tendon grafts. In this study, when palmaris longus was absent in a specimen, a Gantzer muscle was likely present, and may provide surgeons an alternative tendon graft source in the upper extremity without requiring additional incisions in the lower extremity for alternative tendon graft sources. Further biomechanical testing of the Gantzer tendon with comparisons to other common tendon graft sources is warranted.