Anomalous bilateral contribution of extensor pollicis longus and muscle fusion of the first compartment of the wrist

Abstract

Knowledge of the anatomical variations of the muscles of the first dorsal compartments of the wrist is clinically relevant to De Quervain's tenosynovitis and to reconstructive surgeries. In the literature, there are many reports of the presence of multiple insertion tendons in the first dorsal compartment of the wrist, but few reports describe occurrences of fusion and muscle contributions. This case report describes an anomalous bilateral contribution of the extensor pollicis longus. This anomalous contribution was found through a slender auxiliary tendon that crossed laterally under the extensor retinaculum, entered the first dorsal compartment of the wrist and merged with the tendon of the extensor pollicis brevis muscle. In the same cadaver in which this contribution was present, there was atypical muscle fusion of the abductor pollicis longus muscle and extensor pollicis brevis muscle. In conclusion, anomalous bilateral contribution of the extensor pollicis longus muscle and atypical muscle fusion, concomitant with a variant insertion pattern, are the highlight of this case report. Furthermore, it is concluded that additional tendons may be effectively used in reconstructive surgeries, but that there is a need for knowledge of the possible numerical and positional variations of these tendons, with a view to making more effective surgical plans.

Relationship to the superficial radial nerve and anatomic variations of the first extensor compartment in Thai population: a basis for successful de Quervain tenosynovitis treatment

“…Our discovery of a split EPL tendon traveling deep to the EPB tendon into one sub-compartment of the 1st EC and remerging with the main EPL slip distal to the 1st EC, before inserting into the base of the distal phalanx of the thumb has not been reported previously. Rosa et al [ 47 ] described a case with the bilateral contribution of a tendon slip from EPL that crossed laterally under the ER, entered the 1st EC, and merged with the EPB tendon which was different from our observation. Interestingly, this finding occurred bilaterally in one cadaver.…”