The authors perform a cadaveric study to assess whether accessory slips of the abductor pollicis longus tendon (APL) inserting into the thenar eminence or trapezium influence the incidence and severity of basal joint arthritis. The first extensor tendon compartment in 73 cadaveric hands was dissected and trapeziometacarpal degeneration was graded macroscopically. The main APL tendon, which inserts into the base of the first metacarpal, was found to be accompanied by supernumerary slips in 96% of cases. Separate thenar and trapezial tendon slips occurred commonly but coexisted in only 1 case. The authors concluded that basal joint arthritis was not influenced by the number of accessory APL slips or whether the slips inserted into the thenar eminence or trapezium.
The insertion of supernumerary APL tendon slips into the thenar eminence and/or trapezium has previously associated with basilar thumb joint degeneration. Zancolli (Hand Clinics, 2001) reported good results after division of thenar APL slips in early primary arthritis. However, several anatomic studies have failed to demonstrate a relationship between supernumerary APL slips and CMC arthritis. The authors in this study hypothesized that Zancolli’s success with tendon slip division may have been related to local denervation rather than alterations in force transmission across the trapeziometacarpal joint.