The importance of optimising neurologic safety during spinal deformity surgery

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Lawrence Lenke, renowned spinal deformity surgeon and the man behind the Lenke system of classification, tells Spinal News International how one of the most feared complications of spinal deformity surgery is lower extremity paralysis and how surgeons have to thoroughly prepare pre-operatively to identify patients who are high-risk. He is also scheduled to speak on this topic at the 18th International Meeting on Advanced Spine Technologies (IMAST) in July in Copenhagen, Denmark.

Why is this an important issue, particularly in adult deformity surgery?

 

One of the most feared complications of spinal deformity surgery is lower extremity paralysis. Adults with long-standing deformities are at greater risk since their spinal columns and their neural axes have been deformed for a long period of time. They usually have a greater degree of rigidity and kyphosis and potentially a more tenuous blood supply, all risk factors for neurolologic deficit with deformity correction.

 

What does the literature say on neurologic safety and spinal deformity surgery?

 

The literature is quite varied regarding the risk of neurologic deficit for many reasons including the type of pathologies and ages of patients included, whether the deformities are primarily in the coronal plane (ie scoliosis), the sagittal plane (ie kyphosis vs. scoliosis) or combined, the magitude and rigidity of the major deformity as well as the correction manoeuvres utilised during the operation. For typical adolescent idiopathic scoliosis  patients, the neurologic deficit rate should be

 

What are your key tips to surgeons on what to do in order to get maximum neurologic safety?

 

To minimise neurological deficits in spinal deformity surgery, thorough pre-operative preparation is critical,   understanding those deformity characteristics which will place the patient at higher risk. These conditions include: adults (vs. paediatric); kyphosis (vs. scoliosis); rigid (vs. flexible); revision (vs. primary); and those patients either not monitored or unable to be monitored (vs. those having appropriate spinal cord monitoring); and those with myelopathy due to their deformity (vs. those with normal neurologic function). Next, using meticulous surgical technique with adequate mean arterial pressure (MAP) to maintain adequate spinal cord perfusion (usually MAP >70–80 at critical portions of the surgery especially for those at higher risk) will be helpful. Meticulous surgical technique of implant placement (ie pedicle screws) and deformity correction is always necessary to avoid iatrogenic neural compromise. The use of multimodaltiy spinal cord monitoring has been shown to significantly reduce the rate of major neurologic deficits and is imperative as the current standard of care for those centres in the developed world, including some form of motor tract monitoring which has been shown to correlate most closely with both the acuity of an impending problem and the postoperative motor status. Lastly, careful and complete motor neurologic assessment via a wake-up test should always be performed prior to a patient leaving the operating room, and frequently during the first 48 hours postoperative.

 

Are there any studies on this issue in the pipeline?

 

To fully elucidate the neurologic complications following complex adult deformity surgery, the Scoliosis Research Society (SRS) and AOSpine International have recently partnered to prospectively study a large cohort of adult patients undergoing spinal deformity surgery. Termed the “Scoli-Risk Study”, 15 centres from around the world have been selected by the principal investigators Leah Carreon (Louisville) Ken Cheung (Honk Kong), Michael Fehlings (Toronto), Lawrence Lenke (St Louis), and Chris Shaffrey (Virginia). Aiming for a late 2011 start date, this landmark study will provide definitive data on the neurologic as well as all complications associated with high risk, complex adult deformity surgery as a much needed baseline for future studies of attractive medications and future techniques aimed at lowering these complications. It is only through this type of multicentre collaborative investigation that major strides will be made to make all forms of spinal deformity surgery safer for the patients that we treat.