Carpal Tunnel Syndrome As a Complication of Wrist Fracture
There are many potential causes of carpal tunnel syndrome (CTS). Most people are familiar with CTS from repetitive motions, especially from activity in the work place. But CTS can also occur as a result of a wrist fracture. Specifically, fracture of the distal radius is the focus of this study.
Symptoms of CTS begin when the median nerve gets squeezed inside the carpal tunnel of the wrist, a medical condition known as nerve entrapment. The carpal tunnel is a canal formed by the wrist bones arranged in a circle. Nerves and blood vessels pass through the tunnel going from the wrist to the hand. Anything that causes pressure inside the carpal tunnel can compress the median nerve leading to CTS.
There are two bones in the forearm: the ulna and the radius. The radial bone is the larger of the two forearm bones. It's on the thumb side of the forearm. The authors showed how the risk of CTS after a distal radial fracture increases if the two ends of the bone are displaced (separated). Distal refers to the end of the bones in the forearm that's closest to the wrist.
They found that increased pressures within the carpal tunnel following fracture was the main cause of the acute CTS. They studied a group of 50 patients who had acute CTS after surgery for a distal radius fracture. The purpose of the study was to find predictive factors that would help surgeons prevent this complication.
Each patient was treated for the displaced fracture with an open reduction and internal fixation (ORIF). Open reduction means an incision was made to open the area for the surgeon to make the repair. Reduction means the two ends of the bone were moved back together and lined up again. Internal fixation refers to the use of a metal plate and/or screws to hold the ends of the bones together until healing occurs.
These 50 patients were identified because later, after the surgery was done, they developed CTS. Then they needed a second surgery to release the band of connective tissue across the carpal tunnel area. This area is called the retinaculum. The procedure is called a carpal tunnel release.
With a fracture, there can be contusion, deformity, or swelling from elevated pressure within the tunnel. Any of these problems can cause median nerve dysfunction and lead to permanent damage of the median nerve. Early recognition and treatment of any of these factors can prevent long-term problems.
But is it possible to tell ahead of time who might develop acute CTS after distal radial fracture? The goal would be to prevent carpal tunnel syndrome. The surgeon could do prophylactic (preventive) surgery for CTS at the time of the open reduction and internal fixation surgery.
These 50 patients who did develop CTS were compared with another group of 50 patients with the same type of radial fracture. The second group were matched with the first group by age, gender, and injury mechanism (how the injury occurred). But the difference was that the second group didn't have CTS.
Various factors were considered as being possibly significant. These included injury mechanism, other arm injuries present at the same time, low versus high energy injury, open or closed fracture, and presence of a crush injury. The authors were able to isolate fracture translation or displacement as the main difference between the two groups. Fracture translation is what would be called a predictive factor.
They found that if the two bones moved 35 per cent or more, the risk of acute CTS increased measurably. In general, studies show that displaced radial fractures are more common among men. The same was true in this study. But acute CTS after distal radial fracture was more likely to occur among women less than 48 years old.
The authors weren't sure if that was a fluke in their findings or a truly significant result. They also noted that because they were more likely to see higher-energy injuries at their clinic, they couldn't be sure their findings would be true for all displaced distal radial fractures. Before making specific recommendations, future studies will be done to sort out these two variables (age and high energy injury) further.
George Dyer, MD, et al. Predictors of Acute Carpal Tunnel Syndrome Associated with Fracture of the Distal Radius. In The Journal of Hand Surgery. October 2008. Vol. 33A. No. 8. Pp. 1309-1313.