Since that time, they have become very popular for spinal fusion. They help the spine bear greater loads than bone graft alone. The surgeon can fill them with bone material to help strengthen the fusion.

Bone is still a better material than metals or alloys. So scientists continue to look for ways to fuse the spine without screws, metal plates, or cages. A recent study using bone dowels was reported.

Threaded bone dowel taken from cadaver bones (preserved after death for use) were used instead of cages. Bone transmits forces through the spine better than titanium cages but can't sustain as much load as cages.

Patients who got the bone dowels did better when the spine was bolstered with screws at the same time. Stand-alone bone dowels met with a high rate of complications and failure. The bone dowels cracked and broke. Then the surgeon had to take them out and replace them with cages anyway.

Studies will continue to try different materials and methods to perfect spinal fusion. At the same time, artificial disc replacements are now available to replace fusion altogether.