The incidence and morphology of the Gantzer’s muscle in a Kenyan population

Abstract

Gantzer’s muscle is an accessory head of the flexor pollicis longus (FPL). Its incidence, attachments as well as relations to nervous structures have been shown to exhibit population variations, which have important clinical bearings. Data from our setting however remains partly elucidated. To study the muscle, the skin of the anterior forearm and fascia were removed to expose the flexor compartment of the forearm. The flexor muscles were also identified and reflected. The Ganzter’s muscle was identified as that muscle belly originating from the flexor digitorum superficialis, the radius, the medial humeral epicondyle or the ulna coronoid process and inserted on the flexor pollicis longus or the flexor digitorum superficialis muscle. Its prevalence, laterality, origin, insertion, shape and relation to the anterior interosseous nerve were determined. The data obtained was entered into SPSS and percentages calculated for the different variables. The muscle was found in 19/43 (44%) cadavers on the right and on 20/43 (46%) on the left. In 5 out the 43 cadavers (11%), the muscle was present bilaterally while in the rest, it existed solely as either on the right orleft (predominantly on the left, 46%). The Gantzer’s muscle was also noted to predominantly originate from the Flexor Digitorum Superficialis muscle (72% on the left, 76% on the right) and insert on the Flexor pollicis longus (100%). As regards its shape, it was predominantly triangular, on both right side (65%) as well as the left side (54%). In majority of the cases, the muscle also lay posterior to the anterior interosseous structures (100% on the left and 89% on the right). In conclusion, the Gantzer’s muscle is relatively common in our population, exhibits marked population variations and as such should be taken into account especially during surgical approach to the anterior elbow to avoid its inadvertent injury.