Now that Kobe Bryant suffered a luno-triquetral ligament injury in his wrist, many people are interested in this problem. The luno-triquetral ligament keeps two of the wrist’s small bones, the lunate and the triquetrum, aligned and connected to each other so that they move together in a normal, synchronous fashion during wrist motion. Luno-triquetral ligament injuries can cause significant pain and can lead to arthritis, but are not as dangerous as the more common scapho-lunate ligament injuries (please see my previous blog on scapho-lunate ligament injuries). Luno-triquetral ligament injuries are also usually better tolerated than are scapho-lunate ligament injuries, causing less pain and disability.
Similar to scapho-lunate ligament injuries, luno-triquetral ligament injuries can occur from either repetitive overuse or from trauma, such as a fall onto the outstretched hand or a twisting injury, often due to power tools. Luno-triquetral ligament injuries can 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. They also can cause pain with forearm rotation, such as when using tools, turning a doorknob, etc.
The diagnosis of luno-triquetral ligament injuries is suspected based on a physical examination performed by a hand surgeon. Tenderness over the luno-triquetral ligament and pain about the ligament when extending the wrist makes one suspicious of a luno-triquetral ligament injury. The hand surgeon will perform various maneuvers to determine whether or not the lunate and triquetral bones are moving together correctly.
MRI is not very accurate for diagnosing luno-triquetral ligament injuries, even if intra-articular dye is added to the study (ie. an MR arthrogram). The best way to diagnose luno-triquetral 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, such as occult ganglion cysts, avascular necrosis or interrupted blood supply of the lunate, etc.
In mild cases, when the luno-triquetral ligament is ‘sprained’ and not significantly torn, immobilization using a splint or a cast, a steroid injection and avoiding loading the extended wrist (see the above activities that do this) for an extended period of time (often 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 luno-triquetral ligament instability. This is done arthroscopically. Wrist arthroscopy is a minimally invasive out-patient procedure that involves minimal down-time. After confirming the luno-triquetral ligament injury, the unstable torn ends of the ligament are debrided (shaved down) and an absorbable screw is placed between the lunate and triquetrum. This screw often provides stability and pain relief. A cast is worn for 6 weeks after surgery. This arthroscopic treatment has approximately an 80% success rate. As for scapho-lunate ligament injuries, there is a 20% failure rate for all surgical treatments of luno-triquetral ligament injuries.
Some people have long ulna bones that push against the triquetrum, causing luno-triquetral ligament injuries. In these cases, the ulnar bone may need to be shortened to take the stress off of the luno-triquetral joint. Shortening the ulna also tightens up the other ligaments around the luno-triquetral joint, providing further stability and symptom relief. The success rate of ulnar shortening is 81-84% and, in fact, many believe that ulnar shortening is the best long-term answer for luno-triquetral ligament injuries. In order to tighten up the ligaments about the luno-triquetral joint, the ulnar shortening has to be performed in the middle of the ulna bone, in its shaft. This is an outpatient procedure that involves removing a few millimeters of bone from the center of the ulnar shaft. A plate is placed to protect the ulna while it heals, which takes approximately 3 months. A cast is worn for the first 6 weeks, and then a removeable brace is used until the bone is fully healed. The main drawback to this procedure is that sometimes the ulna takes over 3 months to heal. Often, a bone stimulator is used to speed up the healing process. A bone stimulator is a painless device applied 20 minutes a day the operative area. Most activities, including many sports, can be restarted without the bone fully healed on x-ray.
If the luno-triquetral ligament injury is very severe because the secondary, back-up ligaments around it have also torn, or if the luno-triquetral ligament injury has already led to arthritis, the wrist is treated with a luno-capitate partial wrist fusion, the same procedure used to treat wrist arthritis (please see the Wrist Arthritis section of my website). Lunocapitate fusion is an outpatient procedure that involves fusing the lunate and the capitate together. The triquetrum and the scaphoid are both removed. A cast is worn for approximately 6 weeks and then therapy is begun. This is a predictable procedure that works very well for advanced wrist problems, including arthritis.
The good news about luno-triquetral ligament injuries is that they are usually not as serious as scapho-lunate ligament injuries. An injection and immobilization is often all that is needed. However, if problems persist, there are a number of outpatient surgeries that can provide relief.