Instrumented Reduction and Monosegmental Fusion for Meyerding Grade IV Developmental Spondylolisthesis: A Report of 3 Cases

There are numerous reports of treatment methods for spondylolisthesis with a Meyerding Grade of more than III. In high dysplastic spondylosthesis, surgical treatment was selected because there is considered to be a high possibility of low back pain and lower limb neurological symptoms worsening if slippage progresses. Monosegmental lumbar interbody fusion (L5–S1) with a pedicle screw system (PPS) was used to treat three cases of Meyerding Grade IV developmental spondylolisthesis. Patients gave written informed consent. The spondylolisthesis was reduced to Meyerding Grade I and sagittal balance improved in all three cases. In two cases with severe spinal instability, there were no postoperative neurological complications and the course was favorable. However, in one case with little spinal mobility due to vertebral body dysplasia, despite performing sufficient decompression of the nerve root at L5 and slow reduction to avoid placing excessive tension on the nerve root, a transient neurological disorder was observed. A PPS was used to increase the reduction strength and favorable reduction was possible. However, in the case with a long clinical course and the case with poor spinal mobility, since the mobility and plasticity of the nerve root itself may have been reduced, it was considered that reduction should be performed carefully using intraoperative neurological monitoring.