Early Loosening of Spinal Rod in a Case of Degenerative Grade 1 Spondylolisthesis treated with Unilateral Pedicle Screw Fixation and Transforaminal Cage for Interbody Fusion.

Introduction: Unilateral pedicle screw fixation and transforaminal cage for interbody fusion are well-established form of treatment for lumbar spondylolisthesis. It is cost effective and has shown to have a comparable outcome to bilateral pedicle screw fixation. We present a case of unilateral pedicle screw fixation and transforaminal cage for interbody fusion in a patient of Grade 1 Degenerative spondylolisthesis who had an early implant failure, and try to assess the possible events leading to it.

Case Report: A 53-year-old female presented to our outpatient department with low back pain that had persisted for a few years. Plain radiographs revealed degenerative Meyerding Grade I spondylolisthesis at L5-S1. The patient underwent posterior decompression through left-sided laminotomy followed by pedicle screw fixation on the right side. Screws were inserted in the pedicle of L5-S1. An optimal hold of the screw in the left pedicle of L5 could not be achieved due to the poor quality of bone; hence, intraoperatively, the plan was revised from bilateral to unilateral pedicle screw fixation. Further, a transforaminal interbody cage was inserted. The patient started complaining of severe pain on the 8th post-operative day. X-ray done on the next day revealed loosening of the rod from the L5 pedicle screw, with back out of the insert screw. The patient was subsequently posted for revision surgery. During the subsequent follow-up at 6 months, the patient has shown significant symptomatic improvement and has resumed her routine daily activities.

Conclusion: Early rod loosening and migration are a rare phenomenon in lumbar pedicle screw fixation. Meticulous and precise pre-operative planning and surgical techniques may avert such complications. This case highlights the fact that though unilateral fixation is a reported treatment for listhesis, the proper case selection is needed. Conditions such as obesity and osteoporosis need to be considered, and preferably bilateral fixation should be done in such cases.