Research

The revision of cylindrical cage pseudarthrosis can be performed by either posterior instrumented fusion alone or combined anterior cage removal and bone grafting followed by posterior stabilization and fusion. Inherent risks with revision anterior surgery (iliac vein or artery laceration, urethral injury, visceral injury, retrograde ejaculation) lead some authors to recommend posterior alone procedures. Concerns remain that the pseudarthrosis is not directly addressed and motion may remain if the fibrous anterior nonunion does not heal.

Patients undergoing revision for failed cage arthrodesis were prospectively identified and followed. Radiographs and outcomes were collected at a minimum of two-year follow-up.

Seventeen adult patients (22 pseudarthrosis levels) had revision surgery for failed cylindrical cage arthrodesis and minimum two-year follow-up. AP revisions were done in nine patients (12 levels) and 8 patients (10 levels) had posterior only approach. The majority of the cages were placed at either L5-S1 (55%) or L4-L5 (32%). The revision surgery extended to levels beyond the originally treated levels in 6 (35%) of the patients.

Solid interbody fusion was achieved at two-years follow-up in 92% (11 of 12) of the levels treated with AP procedures, and in 20% of levels (2 of 10) treated via posterior procedure alone (5 indeterminate and 3 non-unions). Solid posterolateral arthrodesis was noted in 92% (11 of 12) of the AP procedures and in 30% (3 of 10) of the posterior procedures alone (6 indeterminate levels and 1 non-union).

The overall pain, as measured by a visual analog scale (0-10), was on average 6.1, with 29% of patients with severity of 8 or higher. The majority of the patients reported daily symptoms of leg pain (73%), low back pain (86%), mid-back pain (57%), numbness and tingling (63%), weakness (57%) and buttock pain (64%). Overall satisfaction with treatment was 43%; 65% felt the surgery was successful; 76% would recommend the surgery and 81% would have the same treatment again.

This study documents an overall modest clinical outcome in treatment of cage pseudarthrosis. As suspected AP procedures demonstrate a high rate of interbody fusion where as the fusion assessment of posterior alone procedures is limited due to the cages. The incidence of additional fused segments suggests the complexity of surgical management of the degenerative lumbar spine.