Unilateral Versus Bilateral Strut Placement in Revision Spine Surgery

The rate of spine surgery reoperations is between 5% and 20%. Reoperation of the spine entails a series of additional risks related to the presence of a distorted anatomy, scar tissue, and adhesions, with reported increased occurrence of dural tears and damage to the neural structures. These risks are particularly real when interbody cage placement and instrumentation are performed. In this context, the choice of positioning a single or double cage as interbody support in posterior or transforaminal interbody fusion (PLIF and TLIF) procedures should be made not only in consideration of the biomechanical properties of the spine segment involved but also acknowledging the greater risks related to surgery through dense scar tissue. The positioning of a single cage has the advantage of requiring a unilateral approach therefore reducing the risk of harm to the surrounding delicate structures; conversely, it presents a reduced surface for the distribution of the load and objective difficulties in providing a symmetrical support, in comparison to two cages. The concomitant presence of posterolateral instrumentation provides the single cage with a significant stability and reduced stress on the interbody construct. As take home message, while the indication for performing a PLIF or TLIF in patients with previous lumbar surgeries should be evaluated on a patient-by-patient basis, the evidence suggests that the choice of a unilateral approach in association with pedicle screw instrumentation provides a reliable structural stability with reduced risk of dural tear or damage to the neural structures