BIGGER IS NOT NECESSARILY BETTER: Minimally Invasive Spine Surgery

Rishi Wadhwa, MD

Patients often ask if I do spine surgery “minimally invasively.” Typically this question is intended to find out if I operate through small openings or with a microscope. This type of surgery—minimally invasive spine (MIS) surgery—is my particular area of interest within neurosurgery. Thanks to this interest, I completed a spine fellowship at UCSF, focusing on developing expertise in performing these procedures and caring for these patients. 

MIS surgery employs a set of techniques that allow the surgeon to perform a number of spinal procedures through minimal-access openings, often using small retractor tubes and a microscope. It limits blood loss, obviates the need for muscle retraction (the major cause of post-operative pain in spinal surgery) and leaves a favorable cosmetic result. Almost all degenerative spinal pathologies can be treated this way including:  

• Lumbar/thoracic discectomy and foraminotomy  
• Lumbar interbody fusions and pedicle screw placement  
• Cervical foramintomy and discectomy  
• Lateral interbody fusion  
• Spinal cord stimulator placement  

MIS surgery offers many other advantages.  A recent UCSF study¹ indicates that direct benefits include reduced need for narcotics, lower incidence of post-operative wound infections and earlier return to work. MIS surgery is also associated with a direct cost savings of about $4,000 per patient and reduction of VAS (visual analog scale) pain scores in MIS patients as compared to those who undergo open spinal surgery.¹ Multiple studies have demonstrated significantly less blood loss in MIS surgery, thus obviating the need for transfusion and fewer subsequent transfusion-related complications.^2,3 Finally, hospital stays have been shown to be significantly shorter in MIS surgery patients.³ 

The disadvantages to MIS surgery are few. These include an initially steep learning curve, which often deters surgeons from pursuing training in this technique. There is also a slight possibility of increased intraoperative radiation secondary to x-ray use. 

Preoperative evaluation is similar in all spine surgeries. Patients must exhaust conservative therapies including rest, physical therapy and interventional pain management. Most patients respond well to conservative treatment. When they do not, the decision on how to proceed can be made after all options are discussed with the surgeon. The patient must be counseled that, as with any procedure, there are risks. With MIS, these include nerve injury, spinal fluid leak and pseudoarthrosis (non-fusion). Patients do not need to be typed and crossed for blood before surgery, as transfusions are extremely rare.

The surgery proceeds as follows: Patients are usually placed under general anesthesia, as there is significant drilling on delicate neural structures. After localization with x-ray fluoroscopy or intraoperative neuro-navigation, a small wire is introduced into the skin on the spine over which small, serially larger dilator tubes are introduced to a maximum diameter of 14 mm for discectomy procedures and 22 mm for fusion procedures (both under an inch, which equals 25.4 mm). Through this small port, the procedural steps, including neural decompression, bone grafting and pedicle screw placement, are completed. Correction of anatomical misalignments can also be performed with MIS. Surgical drains are rarely placed, which limits the chance of infection. Once the procedure is completed, the tube is removed and the incision closed. 

After discectomy procedures, patients are sent home the same day; fusion patients are discharged the following day. Post-operative care and instructions are the same as for open procedures. The wound is typically closed cosmetically with dissolvable sutures, and staples do not need to be removed. Patient-reported outcomes are tracked at regular intervals post-operatively. These are submitted to the national neurosurgery quality outcomes database (N2QOD), part of the physician quality reporting system (PQRS). 

As this field grows, I have been honored to publish a number of manuscripts and textbook chapters in which I have recommended pushing the envelope with MIS surgery for trauma, deformity and tumor surgery. Though these indications are still in their infancy, the well-accepted indications for degenerative procedures have proven safe and effective. In addition, long-term MIS fusion rates have proven at least equal to those of open fusion procedures. 

For most patients, MIS surgery is a viable alternative to open surgery. The surgeon should be adept in both techniques and able to apply the one that best suits the individual patient. This is an exciting time, as Marin County now has the technology and the expertise to apply minimally invasive techniques to spinal surgery.

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Dr. Wadhwa is a fellowship-trained spine neurosurgeon at Marin General Hospital and the UCSF Spine Center. He is also the Spine Medical Director at Novato Community Hospital. 

Email: rishi.wadhwa@ucsf.edu 

References 
1. Cheng JS, et al, “Short-term and long-term outcomes of minimally invasive and open transforaminal lumbar interbody fusions: is there a difference?” Neurosurg Focus, 35(2):E6, (2013). 
2. Zaïri F, et al, “Transforaminal lumbar interbody fusion: goals of the minimal invasive approach,” Neurochirurgie, 59(4-5):171-7, (2013). 
3. Dhall SS, et al, “Clinical and radiographic comparison of mini-open transforaminal lumbar interbody fusion with open transforaminal lumbar interbody fusion in 42 patients with long-term follow-up,” J Neurosurg Spine, 9(6):560-5 (2008).