An injury to the scapholunate ligament is a very serious injury to the wrist joint. Unfortunately, in order to understand what has happened to the wrist it is necessary to understand a little bit about the anatomy of the wrist……..
There are 8 bones in the wrist joint, and the bones involved in this injury are the scaphoid and lunate bones, marked above. If you look directly at the back of your left hand, the X-ray on the left shows the bones of the wrist from the same viewpoint. The gap between the scaphoid and the lunate is usually a few millimetres, and the bones appear to line up with one another.
If you then turn your left hand side on, the xray on the right shows the wrist from this viewpoint. The key here is that the lunate bone points straight upwards, and the scaphoid usually points at about 45° to the lunate.
Where is the scapholunate ligament?
Surgeons think of the wrist joint as having two rows – known as the proximal row (in green) and the distal row. These two rows of bones are tightly held together by ligaments between the bones, and the scapholunate ligament in red binds these two bones together.
The proximal row of bones are spring loaded, and the ligaments are designed to withstand the forces on the spring. Unfortunately, when the scapholunate ligament is torn, the spring is broken, causing the bones to spring apart.
How is the ligament torn?
The scapholunate ligament is really tough, and tearing it takes considerable force. We see this injury most often when people come off a mountain bike or motorbike at speed, or when people fall from a height, putting the hand out to break the fall and twisting during the fall.
How is is diagnosed?
The diagnosis is usually made on an X-ray of the wrist. You can see on the X-ray below that the gap between the scaphoid and the lunate on the left is much bigger now than it was in the normal X-ray above, and the bones are no longer lined up the way they were.
On the side view, the lunate bone has sprung back to point slightly backwards compared to the normal xray. Often, the diagnosis will be confirmed on an MRI scan of the wrist.
What are the symptoms?
This is usually an injury which causes significant pain in the central area of the wrist, with associated swelling of the wrist. The wrist usually very painful to move or load.
Sometimes the injury is not picked up early, and diagnosed as a sprain. In this situation, the problem often presents with ongoing pain, inability to load the wrist, stiffness and sometimes a clunking sensation on movement.
What happens if nothing is done?
This is a really nasty injury, and sometimes there is no good prospect of improving things with an operation. Using the wrist when the bones have spring apart produces very abnormal forces on the joint lining, or cartilage, and this cartilage in turn will wear away within a few years, creating arthritis in the wrist joint. You can read more about wrist arthritis here.
What is the treatment?
The treatment recommendation here is dependent on many factors, including age, bone quality, presence of arthritis in the wrist and whether there are any other injuries to the wrist ligaments. In addition, the treatment recommendations are different if the injury is picked up late (after a few weeks have elapsed).
Early Operative Treatment
The usual recommendation in a young person with good bone and no complicating factors is to repair the ligament surgically. This operation involves opening the wrist joint to get the scaphoid and lunate bones back into their normal position, then fix them in position with metal pins, before repairing the ligament back onto the bone using a special bone anchor screw.
The metal pins are kept in for around 12 weeks after the surgery, and the wrist is in a plaster cast for all of this time. Ligaments take a long time to heal, so we always try to stay on the safe side with the length the wires are in for. They are usually removed in the theatre with local anaesthetic, because the cut ends are well under the skin.
Are there any complications from this type of surgery?
All operations have a risk associated with them, and there are a number of things that can go wrong outlined here. This injury, however, puts you between a rock and a hard place. There is often a bigger risk to function from not having surgery than from having an operation, and it is this balance that should be discussed with the surgeon beforehand.
Once the wires have been removed, the wrist is very stiff. We then recommend that you start to use the wrist as normally as possible, building up movement and strength over the next few weeks. It takes a long time to recover from this injury, and sometimes physiotherapy is needed to help with the movement and strength of the wrist.
Late operative treatment
If the injury is picked up more than a few weeks down the line, it may be too late to repair the ligament directly – because this ligament sits inside a joint, the joint fluid tends to get to work resorbing the injured ligament and eventually there is no ligament left to repair. In selected cases, surgery is recommended to reconstruct the ligament using part of a nearby tendon. The basics of the operation are similar to the early repair, but with additional work to reinforce the ligament with the tendon graft, and also to reinforced the joint capsule. The rehabilitation is again similar to the early repair.
What are the result of surgery?
Surgery is designed to restore the normal relationship between the scaphoid and lunate bones, but because all ligaments heal with scar tissue rather than with normal ligament, the spring is never regained. This makes the wrist stiff, and most people end up with only around 50-60% of their normal wrist movement.
Grip strength is also usually reduced following this injury, but can be trained up with physiotherapy. Overall, although people are generally happy with the treatment they have had, there is always a long term price to pay for this injury, and wrist function is almost always reduced in the long term.
Most people develop a degree of arthritis in their wrist which may or may not become a problem in time. As a rough estimate, around 25% of patients go on to have surgery for arthritis in the long term following this injury. You can read about wrist arthritis here.
© Fife Virtual Hand Clinic 2021