Bone Tunnel Orientation in Suspension Arthroplasty of the Thumb Carpometacarpal Joint: An Anatomical Cadaver Study

Background: Ligament suspension after trapeziectomy is a common technique in patients with osteoarthrosis. In this study, we set out to determine whether the orientation of the bone tunnel in the first metacarpal base affects the intraoperative position of the first metacarpal after surgery. Methods: Trapeziectomy and Epping procedure were performed in 32 cadaver hands. A drill hole was placed in the base of the first metacarpal, leaving a radial to ulnar tunnel parallel to the joint surface or a diagonal bone tunnel from the radiodorsal surface to the ulnar joint surface of the first metacarpal. Positioning of the first metacarpal was studied via radiography. Results: The distance between the first metacarpal and the scaphoid after suspension arthroplasty was 9.5 ± 2.6 mm when using the parallel radioulnar bone tunnel and 10.9 ± 2.3 mm when using the diagonal bone tunnel. Suspension of the first metacarpal was 33% higher with the diagonal bone tunnel compared with when using the parallel bone tunnel (displacement of 2.8 ± 2.0 mm vs 4.2 ± 2.0 mm). Conclusions: Higher suspension of the first metacarpal after trapeziectomy can be significantly achieved in our cadaveric model when using ligament suspension of the flexor carpi radialis tendon passed from the ulnar joint surface to the dorsum of the metacarpal. Our results have to be determined via clinical examination. To date, we prefer the diagonal bone tunnel when performing ligament suspension arthroplasty.