Loss of Lumbar Lordosis After Fusion and Instrumentation Using 5.5 Millimeter Rod Implants

Twenty two cases were retrospectively reviewed after decompression and fusion was performed for spinal stenosis with degenerative spondylolisthesis and/or degenerative disc disease, with a minimum of 2 levels fused and a minimum follow up of 24 months (range 24-33 months). Average age at surgery was 63.6 years (range 45-85 years). all cases under went posterior lateral fusion only with a multi-axial pedicle screw and 5.5 millimeter titanium rod system. Fused levels ranged from 2 to 6 (average 2.7). No cases were treated with interbody support. All patients were braced for at least 3 months with a rigid orthosis. There was no loss of fixation noted in any cases. Pre-operative standing x-rays were measured for total lordosis and surgical segment lordosis. Intra-operative films were measured for surgical segment lordosis after instrumentaion was placed. Initial post-operative standing films were measured for surgical segment lordosis and total lordosis as were 2 year post-operative films. Loss of surgically established lordosis was seen at the first follow up averaging 6.3 degrees (range 0-19 degrees) as measured over fused levels. An additional 1.5 degree average loss was seen over the next 2 years (range 0-8 degrees). Loss of total lordosis was seen at the first post-operative visit when compared to pre-operative films in 14 cases averaging 8 degrees (maximum 20 degrees) with further loss of lordosis seen at 2 year follow up in 10 cases (maximium 18 degree loss). Loss of instrumented segment lordosis was compensated for by hyperlordosis at proximal adjacent segments in 6 cases with advanced collapse of adjacent discs in 2 others. No pseudoarthroses have been identified to date. Two patients are awaiting revision surgery. These implants appear to inadeqately control lumbar lordosis without anterior column support.