Scapho-Lunate (SL) Ligament Injuries

Scapho-lunate (SL) ligament injuries are serious injuries to the wrist. The scapho-lunate ligament connects two of the most important bones of the wrist together: the scaphoid and the lunate. The scapho-lunate ligament keeps those small bones of the wrist moving together in a normal, synchronous fashion. Tears of the scapho-lunate ligament can cause significant pain and usually lead to arthritis after 10-15 years, sometimes earlier.

Scapho-lunate ligament injuries can occur from either repetitive overuse or from trauma, such as a fall onto the outstretched hand. Scapho-lunate ligament injuries lead to pain on the back (dorsum) of the wrist that is worse with activities, especially when putting pressure onto the extended wrist, such as when doing a push-up, getting up off of the floor, getting out of a pool, or opening a door.

The diagnosis of scapho-lunate ligament injuries is suspected based on a physical examination performed by a hand surgeon. Tenderness over the scapho-lunate ligament and pain about the ligament when extending the wrist makes one suspicious of a scapho-lunate ligament injury. The hand surgeon will perform a ‘scaphoid shift’ test, which attempts to determine whether or not the scaphoid and lunate bones are moving together correctly. A negative test does not mean that the ligament is not affected, only that other supportive ligaments may be intact enough to prevent a shift under the low loads imposed during a physical examination. On the other hand, a positive scaphoid shift test signifies a significant scapho-lunate ligament injury.

MRI is not very accurate for diagnosing scapho-lunate ligament injuries, even if intra-articular dye is added to the study (ie. an MR arthrogram). The best way to diagnose scapho-lunate ligament injuries is by arthroscopy. However, MRIs are usually performed before arthroscopic surgery to rule out other problems outside the joint that the arthroscope can’t see (occult ganglion cysts, avascular necrosis or interrupted blood supply of the lunate, etc).

In mild cases, where the scapho-lunate ligament is ‘sprained’ and not significantly torn, a splint, a steroid injection and avoiding loading the extended wrist (see the above activities that do this) for an extended period of time (well over a year) may be enough to quiet things down. Weight-lifting and push-ups can be performed in a splint that keeps the wrist in neutral position. As an aside, although most people perform the bench press and other weight-lifting exercises with the bar pressing their wrist back into extension, this is poor form, and may lead to wrist problems.

If non-operative management fails to provide sufficient pain relief, the next step is to confirm the diagnosis and to visualize the degree of scapho-lunate instability. This is done arthroscopically. Wrist arthroscopy is a quick, minimally invasive out-patient procedure that involves minimal down-time. As above, an MRI is usually obtained before surgery, but because the MRI is not very accurate for problems inside the wrist joint, it is only used to rule out problems outside the wrist joint that the arthroscope can not see.

If the scapho-lunate ligament is intact and the scaphoid and lunate bones are stable, then the pain may be coming from ‘dorsal capsulitis’, a somewhat controversial inflammatory condition of the joint lining next to the scapho-lunate ligament that can mimic a scapho-lunate ligament injury. Dorsal capsulitis can be addressed arthroscopically by removing some of the joint capsule (the joint covering). There is no harm incurred by removing this piece of joint capsule. Following this arthroscopic procedure, there is no splinting and activities can slowly be restarted within a week following surgery. If any other problems are found within the wrist joint, they can be addressed arthroscopically or noted for further discussion with the patient if they are too severe for arthroscopic management.

If the scapho-lunate ligament injury is due to a traumatic event that occurred within the past 3 months in a young patient, ligament repair can be considered. Let me state now for the record that anything that is done to treat a scapho-lunate ligament injury has at least a 20% failure rate. Period. Sometimes more. Scapho-lunate ligament injuries are still one of the big unsolved problems in hand and wrist surgery today.

A scapho-lunate ligament repair is performed through an open incision. The scapho-lunate ligament is repaired back to the bone with a small anchor, which is looks a lot like the head of a harpoon. It sticks into the bone and has stitches on it that hold the ligament back down against the bone. The scapho-lunate ligament repair is protected by an absorbable screw between the scaphoid and the lunate. The screw absorbs over time. This eventually causes it break, with a disconcerting, but harmless, ‘pop’ a few months after surgery. However, by the time it breaks it has already stabilized the scaphoid and lunate together enough that the ligament has healed, if it’s going to heal.

If there is no acute injury, or it’s been over 3 months following an injury, a scapho-lunate ligament repair will probably fail. As a failed scapho-lunate ligament repair can lead to permanent stiffness, it’s not a surgery that I recommend if the odds of success are poor. In this situation, which is the most common situation, if the symptoms are too much to live with reconstruction can be considered. I also prefer reconstructions rather than scapho-lunate ligament repair in patients between the ages of 40-60 years, as stiffness following scapho-lunate ligament repair becomes more common in patients over 40. Reconstruction techniques stabilize the scaphoid by other methods than scapho-lunate ligament repair. There are many different reconstruction techniques described in the hand literature. The reason that so many techniques have been described is that none of them work predictably. Again, there is at least a 20% failure rate with any treatment of scapho-lunate ligament injury.

My own personal philosophy when all treatments have a significant failure rate is to perform techniques with higher success rates that also have low complication rates. At the current time, until better reconstructive options come along, there are two techniques that I prefer. Both involve using tendons to substitute for the loss of the scapho-lunate ligament. One of the techniques is a little less surgery, and one is a little more surgery. Both are performed on an outpatient basis.

The lesser surgery involves moving one of the wrist’s extensor tendons (the extensor carpi radialis longus, or ECRL) to the scaphoid to stabilize the scaphoid during wrist motion. It is simple and quick. Following surgery a cast is worn for 4 weeks and then hand therapy is started to regain wrist motion. I prefer the ECRL transfer for lesser degrees of scapho-lunate ligament instability in patients whom wish to avoid significant stiffness; older patients, for example.

The bigger surgery is called a ‘modified Brunelli reconstruction’. This involves taking roughly 1/3 of the flexor carpi radialis (FCR) tendon and pulling it through a hole created in the scaphoid. This is then pulled over the scaphoid and lunate bones and tied down with an anchor to reconstruct a tether between the scaphoid. A pin is placed to hold the scaphoid in position and a short arm cast is used for 4-6 weeks, depending on how bad the instability is.

If the patient is 55-60 years or older, it may be better to just remove the scaphoid and perform a lunocapitate fusion, as detailed in the ‘Wrist Arthritis’ section of the website. This outpatient procedure involves a cast for 6 weeks and provides motion similar to what an older patient could expect from a scapho-lunate ligament reconstruction.

I know that’s a lot of information, but scapho-lunate ligament injuries are a complex topic that is still without a predictable solution. We have some good surgeries available, if needed, but no great surgeries as of yet. However, if realistic goals are understood, most patients are quite happy with their surgical treatments.