- Department of Neurological Surgery, University of Washington Medical Center, Seattle, Washington, USA
Correspondence Address:
Trent L. Tredway
Department of Neurological Surgery, University of Washington Medical Center, Seattle, Washington, USA
DOI:10.4103/2152-7806.109186
Copyright: © 2013 Kazemi N This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.How to cite this article: Kazemi N, Crew LK, Tredway TL. The future of spine surgery: New horizons in the treatment of spinal disorders. Surg Neurol Int 19-Mar-2013;4:
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Abstract
Background and Methods:As with any evolving surgical discipline, it is difficult to predict the future of the practice and science of spine surgery. In the last decade, there have been dramatic developments in both the techniques as well as the tools employed in the delivery of better outcomes to patients undergoing such surgery. In this article, we explore four specific areas in spine surgery: namely the role of minimally invasive spine surgery; motion preservation; robotic-aided surgery and neuro-navigation; and the use of biological substances to reduce the number of traditional and revision spine surgeries.
Results:Minimally invasive spine surgery has flourished in the last decade with an increasing amount of surgeries being performed for a wide variety of degenerative, traumatic, and neoplastic processes. Particular progress in the development of a direct lateral approach as well as improvement of tubular retractors has been achieved. Improvements in motion preservation techniques have led to a significant number of patients achieving arthroplasty where fusion was the only option previously. Important caveats to the indications for arthroplasty are discussed. Both robotics and neuro-navigation have become further refined as tools to assist in spine surgery and have been demonstrated to increase accuracy in spinal instrumentation placement. There has much debate and refinement in the use of biologically active agents to aid and augment function in spine surgery. Biological agents targeted to the intervertebral disc space could increase function and halt degeneration in this anatomical region.
Conclusions:Great improvements have been achieved in developing better techniques and tools in spine surgery. It is envisaged that progress in the four focus areas discussed will lead to better outcomes and reduced burdens on the future of both our patients and the health care system.
Keywords: Future developments, minimally invasive surgery, navigation, robotics, spine surgery
INTRODUCTION
Although it is difficult to predict the rapidly changing practice of spinal surgery, we focus this article on four areas of burgeoning interest: Minimally invasive spinal surgery, motion preservation, robotics and neuro-navigation and the use of biologics. All four of these areas will most likely see further significant growth in the near, as well as distant future. Minimally invasive techniques have been developed and honed for decades; however, recent technological advances combined with the development of computer software to aid in robotic surgery and neuro-navigation will hopefully allow for safer and more efficacious minimally invasive procedures for our future patients. Moreover, the use of biologically active agents may actually reduce the number of traditional spinal surgeries while providing patients with reasonable non-operative treatment options. Definitive treatment will most likely be preventative in nature, which is in direct contrast to our current surgical treatment modalities which mainly focus on treating the “end-result” of spinal pathology. While this article is not intended to be a comprehensive menu of future products, techniques and trends in spinal neurosurgery, it is our goal to present the possibilities that will be available in our spinal armamentarium as we approach 2020.
MINIMALLY INVASIVE APPROACHES TO THE SPINE
The introduction of the tubular retractor system (METRx™, Medtronic, Memphis, TN, USA) by Foley and Smith in the late 1990s allowed spine surgeons to treat symptomatic herniated discs with minimally invasive techniques.[
Accordingly, the tubular retractor system has undergone various modifications over the past 10 years and has allowed the spine surgeon to expand the role of minimally invasive approaches to include lumbar fusion techniques (i.e., minimally invasive transforaminal lumbar interbody fusions or MI-TLIFs) for treatment of spondylolisthesis, degenerative disc disease, short segment spinal deformity, as well as traumatic fractures. Excellent outcomes combined with fewer complications, shorter hospital stays, and less blood loss have been reported with this technique.[
Another minimally invasive procedure for the thoraco-lumbar spine is the eXtreme lateral interbody fusion (XLIF®, NuVasive, San Diego, CA, USA) or direct lateral interbody fusion (DLIF). This lateral, trans-psoas muscle approach has been popularized by Pimenta and others for the treatment of degenerative disc disease and has also been utilized to treat a variety of spinal pathologies.[
This direct lateral approach has been utilized for the placement of an intervertebral artificial disc outside of the United States and is currently in an FDA-Investigational Device Exemption (FDA-IDE) trial.[
MOTION PRESERVATION
The past decade has witnessed a change in philosophy regarding cervical and lumbar fusion surgery. Traditionally, the anterior cervical discectomy and fusion procedure has provided many patients with symptomatic relief of radicular, and occasionally, axial neck pain with excellent clinical outcomes and high fusion rates.[
Cervical disc arthroplasty complications are rare; however, lumbar disc arthroplasty approaches carry well-documented risks to the lumbosacral vessels, neural elements, and genitourinary structures. This issue may be improved in the future with better preoperative imaging assessment and possibly through minimal access approaches. Furthermore, the direct lateral or extreme lateral approach may reduce these risks and thus become the preferred surgical approach by both spine and general access surgeons.
In regard to the commercially available artificial disc products, two of the FDA-approved cervical disc arthroplasty devices and both of the FDA-approved lumbar implants are composed of materials that do not allow for adequate visualization of the operative disc level and often obscure adjacent segments when evaluated with MRI. In a study evaluating the ability to visualize the spinal canal and adjacent segments after cervical disc arthroplasty, only the Bryan (Medtronic) and Prestige LP (Medtronic) allowed for adequate visualization.[
Figure 2
(a) Intraoperative view of bryan Artificial Disc (Medtronic, Memphis, TN, USA), (b) Postoperative radiograph of Bryan Artificial Disc (Medtronic), (c) Intraoperative view of ProDisc-C Artificial Disc (Synthes, Paoli, PA, USA), (d) Postoperative radiograph of ProDisc-C Artifi cial Disc (Synthes)
Although disc arthroplasty may be a reasonable option for patients with cervical or lumbar disc disease, many patients do not fit the criteria for arthroplasty due to lumbar spondylolistheses, cervical subluxation, lack of motion related to severe spondylosis, and more commonly secondary to insurance-related denials. In this population, fusion surgery will most likely be the mainstay. Traditional titanium-alloy plates and screws are still popular; however, we are witnessing a trend toward bio-absorbable plates and screws, as well as significantly smaller plating systems that purportedly reduce the incidence of iatrogenic adjacent segment disease spondylosis. Bio-absorbable instrumentation has been utilized in plastic surgery and neurosurgery for craniofacial reconstruction for many years, but bio-absorbable anterior cervical plating systems have only been available in the United States since 2006[
These products offer an alternative to their metal counterparts which can often be difficult to remove when re-operation is necessary. The absorbable plating system also negates the artifact that is often visualized on postoperative MRIs.
ROBOTICS AND NEURO-NAVIGATION
There are many potential hazards associated with spine surgery, which include risks to vital structures including important vessels, viscera and of course neural elements. In addition, if instrumentation is utilized, there is a risk of malpositioning of the hardware leading to compromise of the anatomy required for spinal stability. Therefore, good control and accuracy in the operative approach is a necessity in spine surgery. For example, it has been estimated that a dural breach occurs in 3.5% of primary initial discectomies and around 13% of revision discectomies.[
Although robotics has been employed for longer than a decade in many surgical subspecialties, it has only recently been utilized in the area of spine surgery. The advantage of the current robotic platform is that it allows the surgeon real-time procedural manipulation combined with heuristic instrument control, real-scale magnification, and elimination of tremor. All of this can now be combined with anatomical spine navigation to allow precise surgical technique with minimal spinal bony damage and blood loss. However, until recently, robotics has always had limited application in spine surgery due to the challenges of visualization, cost, adequate training, and the development of minimally invasive techniques that have offered a viable and more widely utilized alternative.
Several procedures have been recently tested using the Da Vinci robotic system (Intuitive Surgical Inc., Sunnyvale, CA, USA) including laminectomy, laminotomy, discectomy, and dural repairs on an in vivo porcine model.[
Renaissance™ (Mazor Robotics, Inc., Caesarea, Israel) is a miniature robotic guidance system which can be either mounted on table or on the patient's spinous process. This system together with its precursor, Spine Assist® (Mazor Robotics, Inc.) has now been employed for longer than 5 years. In its development, it has been cadaverically tested using percutaneous placement of pedicle and translaminar facet screws, as well as being employed for the placement of transpedicular screws via open and percutaneous techniques in PLIFs.[
In a retrospective multi-center trial, using the Spine Assist, screw placement was determined to be clinically acceptable in 98% of cases based on intraoperative X-ray imaging. Postoperative imaging demonstrated that 98.3% of the screws fell within a safe zone, whereas in 9%, screws breached the pedicle by up to 2 mm. The remainder of the screws breached between 2 and 4 mm, and in only two cases was there a breach greater than 4 mm. Neurological deficit was seen in four patients, but following revision of the instrumentation, all of these deficits resolved.[
Overall, robotic-assisted surgery provides several advantages to the surgeon. These include a significant improvement of dexterity with a reduction in physiological tremor, significant reduction in X-ray–induced radiation, visualization in three dimensions, and significant improvement in ergonomics with significantly less pain, strain, and stiffness.[
There are of course several disadvantages to robotics in spine and these include the lack of haptic feedback from tissue manipulation, increased operating time, and the need for increased training not just for the surgeon but also other operating room staff. There is also the issue of significant cost. The estimated cost of acquiring a Da Vinci system, for example, lies in the $1.1-$1.7 million range.[
In concert with robotics, spinal and neuro-navigational devices can be utilized. Many large hospitals offering complex spine surgery do not consider navigation a routine component of current treatment. Often, the reasons for this include the significant investment in cost, space, and the belief that its utility does not improve outcomes significantly over and above non-navigation techniques.
Although intraoperative navigation has been available for the past decade, it has evolved from plain fluoroscopy to 2D and then 3D fluoroscopy acquired intraoperatively and then co-registered with preoperative imaging.[
A recent study compared navigated and non-navigated pedicle screws using the O-arm system and assessed their relative accuracy. The study found that 4.9% of the non-navigated screws needed to be removed intraoperatively compared with 0.6% of the navigated screws. It also reported that a “significant” medial breach, as defined by 50% excursion of the screw diameter, was almost 8 times more likely to occur without navigation. Image guidance leads to more accurate placement of pedicle screws.[
Overall, navigation appears to improve accuracy of surgical instrumentation while also significantly reducing radiation exposure. However, as with robotic-assisted platforms, it can be associated with increased operative time, risk of exposure to infection during draping and un-draping process, and the required learning for both surgical and non-surgical operating room staff. We predict that while it may add little benefit to routine surgical cases where bony anatomical landmarks are sufficient for placement of screws and instrumentation, its greatest application may be observed in cases with significant deformity or dysplastic changes in the spine. For example, it could be of benefit in scoliosis cases with significant rotational deformity of the spine and perhaps in the thoracic region where accuracy is critical.
SPINAL BIOLOGICS
Perhaps the most exciting area in the future treatment of spinal disorders is best witnessed in the development of biologically active agents used to augment and possibly restore the function of the spine. One of the first biologics to be approved in the United States was rhBMP-2 (Infuse, Medtronic). This powerful osteoinductive agent stimulates the production of bone and is utilized to augment fusion surgeries of the spine. Further development of the commercially available product has revolutionized the spine surgeon's ability to obtain a fusion mass in patients that may have problems achieving an adequate fusion. Another biologically active product that was approved by the United States FDA was rhBMP-7 or OP-1 (Stryker, Kalamazoo, MI, USA). This product also promotes bone growth and was marketed in a putty form compared to the absorbable sponge carrier utilized with Infuse. This adjuvant to achieving successful fusion has been documented in preclinical as well as clinical studies.[
Studies have demonstrated the feasibility of placing these agents through minimally invasive procedures.[
As we progress through this decade, we must keep in mind that predicting the future of spine surgery may also be affected by the economic impact on healthcare that looms in the United States and throughout the world. It is conceivable that we will be asked to provide care for more individuals while possibly receiving less payment in return. This could greatly impact the amount of innovation and interest that has allowed our specialty to improve care for our patients. It is also important that our leaders in innovation be allowed to work with industry in an open and honest collaboration in order to benefit our future patients.
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