[Lumbosacral fusion using a femoro-cortical allograft ring]

To evaluate the midterm radiographic behaviour of femorocortical allograftrings (FCA) in lumbosacral fusions in patients with disabling low back pain.

The radiographs of 41 patients with a minimum follow-up of 2 years were analysed by an independent orthopedic radiologist. The fusion rate was determined on lateral tomograms routinely obtained at 3 months intervals. On lateral radiographs the posterior intervertebral disc height as well as the segmental lordosis were measured. Changes of the allografting such as mottling, resorption and incorporation were registered.

The fusion rate was 95.2%. Time to radiographic fusion averaged 8.7 months (2-34 months) and in 66.1% radiographic fusion occurred without significant subsidence. In 18.6% fusion with subsidence resulted from resorption of the FCA and in 15.3% the FCA had protruded into the vertebral body. The posterior intervertebral disc height increased postoperatively by 1.9 millimeters on average. However, postoperative height loss was the rule and occurred within the first 12 postoperative months, resulting in a negligible final gain in height of 0.3 millimeters on average. The final gain in segmental lordosis was 1.3 degrees on average. Complete graft incorporation occurred in 16 of 62 segments (25.8%).

The described technique has proven to be highly effective in achieving a high fusion rate with a stable midterm graft behaviour.