Surgery for Bennett Fractures of the Thumb
Improved technology and smaller surgical instruments have changed the way hand surgeons repair Bennett fractures of the thumb. In this article, hand surgeons review those changes and describe how and when to use arthroscopy and fluoroscopy together to get the best results.

Bennett fractures are named for a physician who first wrote about them in the medical literature way back in 1885. The specific bone that's affected is the thumb metacarpal. Metacarpal is another word for the bone in the thumb that is closest to the wrist. The joint that is affected is the carpometacarpal (CMC) joint. This is where the base of the thumb is connected to the wrist.

A Bennett fracture is a break along the bottom side of the thumb metacarpal closest to the wrist bone. The location at the base of the thumb metacarpal next to the wrist is why it affects the carpometacarpal joint. And because this is a pivotal joint that contributes to all the movements of the thumb, a close and careful fracture reduction is important.

Reduction refers to putting the broken pieces of bone back together so that the bone surfaces line up exactly and the carpometacarpal joint is fully restored. The surgeon uses wires, pins, or screws (called fixation) to hold the bone in place while it heals. Until small-joint arthroscopy became available, surgeons used open incisions and fluoroscopy (real time 3-D X-rays) to guide the reduction and fixation.

But there have been problems just using traction and fluoroscopy because sometimes it looked like the bone is reduced and properly in place when it wasn't. Even a slight rotation of the bone can make a difference. Without an anatomic reduction, patients ended up with a painful, arthritic thumb. Combining arthroscopy with the fluoroscopy has changed all that. Now the hand surgeon can replace the bone fragments where they belong, apply the appropriate fixation, and make sure everything is lined up perfectly before putting the hand in a splint.

All that sounds so simple but the surgeon still has many challenges coordinating these two tools. The arthroscope must be inserted into the joint without hitting nerves, blood vessels, or tendons. The broken fragment must be rotated and slipped back into place carefully with a tiny probe. While holding the probe in place and keeping the bone in its perfect spot, the surgeon then fixes the bone in place. When using screws, the surgeon must be careful that the tip of the screw doesn't go inside the joint.

But the good news is that Bennett fractures of the thumb can be surgically repaired in this fashion and provide patients with a much better long-term result. The authors caution that more complex fractures may still require an open surgery. If the shaft of the bone is broken and/or the soft tissues around the area have been torn, then a more extensive reconstructive procedure may be needed that requires a full incision.
Randall W. Culp, MD, and Jeff W. Johnson, MD. Arthroscopically Assisted Percutaneous Fixation of Bennett Fractures. In The Journal of Hand Surgery. January 2010. Vol. 35A. No. 1. Pp. 137-140.