Symptomatic Subsidence of a Box-Shaped Titanium Cage After Anterior Cervical Discectomy and Fusion: Two Case Reports and Review of the Literature.

This study reports two cases of rare symptomatic subsidence of titanium cages after anterior cervical discectomy and fusion (ACDF). First, an 82-year-old man underwent ACDF at C5/6 and C6/7 using two 6 mm height box-type titanium cages. On the 34th postoperative day, motor weakness occurred in the right upper limb, and CT showed that the cage at C5/6 had subsided 6 mm into the C6 vertebral body. On postoperative day 55, both cages were removed, and C6 corpectomy was performed. The C5-7 space was refixed with a mesh cage and plate. He was discharged home from the rehabilitation hospital three months later. Second, a 41-year-old man underwent ACDF at C5/6 and C6/7 using two 5 mm height box-type titanium cages. He fell violently on the 33rd postoperative day, causing pain from the neck to the left hand, weakness, and skillful movement disorder in the left hand, and CT showed that the cages at C5/6 and C6/7 had subsided by 7 mm and 6 mm, respectively. On the 65th postoperative day, both cages were removed by reoperation, and C6 and 7 corpectomy was performed. The space between C5 and T1 was refixed with a mesh cage and plate. He was discharged home two months later. Possible causes of titanium cage subsidence include osteoporosis, trauma, vertebral cortex damage by an operative procedure, and cage height of 6 mm or more. While ACDF is safe and effective for cervical spondylosis, special caution is needed in older osteoporotic patients.