Spondylolisthesis is defined as an anterior displacement of a spinal vertebra or the vertebral column in relation to the vertebrae below. The pathology is caused by either isthmic or degenerative conditions and, based on the degree of displacement, is separated out into 5 grades (Meyerding classification):
- Grade 1: 0–25% slip
- Grade 2: 25–50% slip
- Grade 3: is 50–75% slip
- Grade 4: is 75–100% slip
- Over 100% (Spondyloptosis) slip
The Aesculap Implant System's S4 Spinal System Spondylolisthesis Reduction Instrument (SRI) is intended to reduce such spondylolisthesis in a controlled manner following the initial slip path of the upper spinal vertebra. The SRI provides the following features and benefits:
| Features | Benefits |
| Allows surgeons to perform reduction with a single level fusion | Spares adjacent healthy vertebra |
| Enables simultaneous reduction and distraction | Easier to use and reduces procedure time |
| The reduction maneuver is precise and controlled | Reduces risk of inadvertent (unwanted and potentially damaging) movements |
| Reduces the listhetic vertebral body along the same curved displacement route | Minimizes unwanted interference with anatomical structures Minimizes neurological deficits that typically result from initial over-distraction of an already stretched nerve root |
| Utilizes S4's construct for reduction | Achieves minimal anatomical impingement (Ultra Low Profile) while maintaining biomechanics |