Improving Anterior Cervical Fusion Rates with Locking Plates

Fusion of the cervical spine (neck) may require metal plates for a rigid result. But the outcomes of this study show that even with a locking plate, motion occurs after anterior cervical discectomy and fusion (ACDF).

The purpose of this study was to measure the amount of motion present after ACDF. A second goal was to find out where the motion was occurring. Anterior plates are used to reduce or stop motion between two vertebrae. This allows for the bridging of bone between the vertebrae.

The same surgeon treated all patients. Allograft bone donated from a bone bank was used as the graft material. A locking titanium cervical plate with an adjustable angle was inserted anteriorly (from the front of the spine).

Special moving X-rays and motion tracking software were used to observe and measure motion after the procedure. Over half of the levels fused had detectable motion two weeks after the operation. Most of that motion occurred at the place where the bone and screw met (bone-screw interface).

Bending of the plate was the second most common source of motion. In a small number of cases, there was movement that originated at the screw-plate interface. It appears that there is enough load repeated in the first two weeks to cause loosening.

Factors that may affect loosening include osteoporosis (decreased bone mass), design of the implant, and post-operative care. It may be possible that patients who do not wear a rigid neck brace after surgery have more loosening than those who do wear the brace. Loosening is also more likely when more than one level is fused.

The authors conclude that efforts to improve fusion results using locking metal plates with ACDF have not been successful. Motion at the fusion site may be complicated by quality of bone, type of bone graft, and even the type of injury (fracture, tumor, disc degeneration).

Surgeons will be able to use this information when planning ACDF procedures. Type of implant used, postoperative care, and patient risk factors must all be taken into account to avoid implant loosening.