Evolving minimally invasive techniques in posterior cervical spine instrumentation

Posterior cervical spine surgery often presents significant challenges, with soft tissue problems being some of the most frequent and devastating complications. Wound dehiscence, infections, and junctional kyphosis are among the most common complications that can result from traditional open procedures (¹). These complications are not only distressing for the patient but also increase the overall cost and recovery time for the procedure. In fact, the posterior cervical/cervico-thoracic approach, in particular, exhibits infection rates as high as 18% (^2–4), a troubling statistic for spine surgeons. Every spine surgeon has encountered posterior cervical surgery cases with horrifying soft tissue issues.

The development of percutaneous techniques in the thoraco-lumbar spine has been one of the major innovations in spinal surgery during the past decades, with significantly decreased soft tissue damage (⁵), leading to reduced blood loss, pain and massively reduced infection rates (⁶) so that these techniques have become indispensable nowadays.

In view of the above-average infection rates of the posterior cervical spine approach and the significantly reduced infection problems with percutaneous approaches in the thoracic/spinal region, the use of percutaneous techniques on the dorsal cervical spine would be extremely obvious.

With the advent of cannulated screws, minimally invasive techniques in the posterior cervical spine have been used for transarticular fixation of the C1-C2-joint complex as early as the mid 1990’s (⁷). Subaxial treatment was limited to non-instrumented keyhole-decompression due to the lack of specifically designed percutaneous stabilization systems (^8–11). 

The transfer of percutaneous techniques from the thoraco-lumbar spine to the cervical spine is not trivial, though: The small dimensions of cervical pedicles and the proximity of the spinal cord and vertebral artery requires an order of magnitude greater precision in screw placement. Radiographic landmarks visible on 2D-fluoroscopy are lacking  (¹²) . 

As a consequence, a high-resolution 3D-intraoperative imaging system in combination with a navigation or robotic system is a conditio-sine-qua-non for the percutaneous application of internal fixation at the subaxial cervical spine.

With the broader distribution of these technologies, medtech companies obviously consider the market situation for the development of percutaneous implant systems to be promising: In the past few years, more than one percutaneous system has achieved market maturity and is available; the majority of competitors have these systems in their pipeline (¹³) . 

Difficulties to be overcome include the high segmental mobility of the cervical spine, which affects precision of navigation much more than in the thoracic spine. 

The second difficulty to overcome is the development of strategies to include effective decompression techniques  into the minimally invasive concept as a whole. 

In spine trauma, the problem of segmental mobility has to be regarded in a unique way: 

Undoubtedly, mobility in the acutely injured spine segment is gross and exceeds any physiologic level – which in most cases is also the basis for the surgical indication.

But: Posterior instrumentation in spine trauma is often used as supporting posterior tension band after reduction, decompression and anterior stabilization of a complete facet dislocation (F4) or additive stabilization after corpectomy / plating of a complete burst (A4) fracture. 

A further frequent indication for posterior instrumentation includes stabilization of an injured ankylosing spine—where segmental mobility beside the injured segment is near to zero. 

In my opinion, these two applications represent the ideal indication for implementation of percutaneous stabilization in the cervical spine, because of limited segmental mobility (facilitating navigation without registration of every single vertebra) and no need for extensive decompression, which both interfere with the available percutaneous techniques. 

The advancing development of percutaneous posterior instrumentation in the cervical spine seems definitely to be considered as the next powerful innovation in the field of spine surgery, which we from the AO Spine KFTI regard as major milestone to be observed closely: Solving the soft tissue issues in the posterior cervical spine will be of great benefit to our patients and will help to reduce a lot of suffering from complicated courses.