End of the Road for Scapholunate Instability

This follow-up study from the Department of Orthopedics at the Alpert Medical School of Brown University (Rhode Island) gives us an idea of the long-term results for surgery to correct scapholunate (wrist) instability. In the original study published in 1998, there were 14 patients treated with a bone-reticulum-bone autograft. Now 15 years later, long-term results for six of those 14 patients are reported.

Scapholunate instability refers to a condition in the wrist where the ligament holding the two bones (scaphoid and lunate) together is torn or ruptured. The scaphoid tips one direction (flexes forward) and the lunate tips in the opposite direction (extends).

This creates a painful, unstable wrist. Surgical treatment to prevent total collapse of the joint is necessary. The surgical choices include repairing the injured ligament, using a screw to hold the bones together, or reconstruction of the soft tissue and bone. In this study series, the reconstructive surgery called bone-retinaculum-bone or BRB was chosen.

In this procedure, the surgeon takes a piece of soft tissue called the retinaculum from the patient’s wrist and uses it to replace the torn ligament. Plugs of bone harvested from the back of the distal radius (forearm bone near the wrist) were inserted into the scaphoid and the lunate. The bone plugs were held in place with screws and wires to create a stable wrist unit. The wires were removed after eight weeks when the patients started hand therapy.

When the original 14 patients were followed-up (two to five years after the procedure), they reported very little pain and all were back to work. Only six of the original 14 were examined directly and X-rayed for this follow-up study. Three others were contacted by phone; only two patients were completely lost to follow-up.

For those patients who were able to return for evaluation, measurements included wrist range-of-motion, pain, and grip strength. X-rays were used to look for wrist arthritis and to measure the scapholunate gap and angle. There was a wide range of results reported.

Three of the six returning patients had complete failure of the graft requiring another surgery. Two had a carpectomy (removal of the wrist bones) and one had an arthrodesis (wrist fusion). Either of these procedures was considered an “endpoint” (nothing more could be done). The three patients contacted by phone did not want to come back for re-evaluation, said they were fine, and did not want any further treatment.

On the positive side, some of the patients did have durable results even while working as manual laborers requiring heavy lifting or participating in competitive weightlifting. Obviously for them, the graft was stiff enough and durable enough to make these activities possible. Why the graft was less successful for others remains under investigation. The surgeons are looking at ways to improve blood supply to the graft tissue as one possible way to improve results.

In summary, the authors of this study recognize the difficulty of treating a scapholunate interosseous ligament injury. Without surgical treatment, the resulting wrist instability can cause collapse and eventual arthritis. But of the many types of treatment approaches, none have a good track record for long-term results, including this bone-retinaculum-bone autograft. Their final statement sums it up quite well, Scapholunate instability remains an unsolved problem despite novel approaches to its treatment.