Medio-Latero-Superior Trajectory Technique

There are many techniques available for fixation, stabilization and fusion of the lumbar spine. Interbody or posterolateral bone grafting techniques are usually supplemented with solid mechanical bone fixation. The many other forms of fixation include spinous process fixation, facet screw fixation, wiring methods and well established techniques such as pedicle screw fixation. Pedicle screw techniques have been the mainstay of stabilization of the lumbar spine for decades because they provide superior mechanical fixation.

Pedicle screw insertion techniques have some drawbacks, including potential neurovascular injury and a requirement for significant muscle dissection to reveal bone landmarks for safe insertion of the pedicle screw. The standard angulation of a pedicle screw requires a lateral to medial approach and therefore, especially for caudal lumbar and sacral pedicle fixation, widemuscular dissection. Percutaneous pedicle screw techniques have been well documented for a variety of indications1, however decompression and bone graft insertion requires an additional approach which can be midline, paramedian, lateral or anterior.

We have used an alternative approach trajectory for pedicle screw insertion for trauma applications for over 10 years2 and, over time, adapted this technique to degenerative pathologies3. Advantages of this alternative pedicle trajectory include that it uses the superior end of the construct to avoid wide dissection of the mobile superior facet joint and it reduces incision length and muscle dissection, thus minimizing approach-related trauma. The medio-latero-superior trajectory (MLST) technique involves a starting point on the medial aspect of the pars with angulation of the pedicle screw in a mediolateral and caudocranial direction.We here discuss both drawbacks of this new screw trajectory along with its potential benefits.

We accept that the indications for this technique are limited. The primary indication is single level degenerative fusion because the technique is not suitable for long segment pathologies such as scoliosis or kyphosis.