Elsevier

World Neurosurgery

Volume 163, July 2022, Pages 214-227
World Neurosurgery

From the Annals of Weill Cornell Neurological Surgery
Minimally Invasive Spine Surgery: An Overview

https://doi.org/10.1016/j.wneu.2022.03.114Get rights and content

Spinal surgery is undergoing a major transformation toward a minimally invasive paradigm. This shift is being driven by multiple factors, including the need to address spinal problems in an older and sicker population, as well as changes in patient preferences and reimbursement patterns. Increasingly, minimally invasive surgical techniques are being used in place of traditional open approaches due to significant advancements and implementation of intraoperative imaging and navigation technologies. However, in some patients, due to specific anatomic or pathologic factors, minimally invasive techniques are not always possible. Numerous algorithms have been described, and additional efforts are underway to better optimize patient selection for minimally invasive spinal surgery (MISS) procedures in order to achieve optimal outcomes. Numerous unique MISS approaches and techniques have been described, and several have become fundamental. Investigators are evaluating combinations of MISS techniques to further enhance the surgical workflow, patient safety, and efficiency.

Introduction

The entire field of surgery is in the midst of a dramatic transformation toward minimally invasive techniques and approaches. Driven by patient preferences and changing socioeconomics of medicine, minimally invasive surgery (MIS) techniques were initially embraced by general and specialty surgeons, with delayed emergence in spine surgery due to unique constraints. Historically, open approaches to the spine were necessary to ensure optimal surgical outcomes and patient safety. For example, during traditional open freehand placement of pedicle screw instrumentation, the surgeon needs to expose not only the screw entry point but also the surrounding anatomy in order to best estimate the optimal screw trajectory while avoiding injury to critical neurovascular structures. These techniques require long incisions with significant trauma to surrounding muscle and tissues. A larger surgical bed also predisposes to the risk of blood loss (with or without need for transfusion), risk of surgical site infection, and increased pain and narcotic requirements, resulting in longer hospital stays. In addition, in some cases of deformity or trauma, reliance on the knowledge of normal anatomic trajectories and visualization of surrounding anatomic structures may still result in malpositioned instrumentation. Use of newer intraoperative imaging techniques, in combination with powerful software, has allowed surgeons to supplement their understanding of the 3-dimensional (3D) anatomy of the spine with real-time navigation, avoiding the need for extensive exposure of surrounding landmarks. In fact, minimally invasive techniques have been associated with decreased postoperative narcotic requirements, lower blood loss, and shorter hospital stays.1,2 Minimally invasive spinal surgery (MISS) is now routinely used in the treatment of a growing variety of pathologies, including trauma, degenerative disease, and cancer. Though not all spine pathology is optimally treated with MISS, an estimated 75% of the approximately 1.2 million spinal procedures performed each year in the United States could be performed in whole, or in part, with MIS techniques.3

In addition to the technological factors which have enabled MIS implementation in spine surgery, socioeconomic and population factors have increased demand. In the United States, the need for surgical treatment of degenerative spinal conditions is predicted to increase as the population over 65 years old increases by 20% between 2015 and 2030.4 In this age group, there is a 68% rate of radiographic degenerative spinal deformity.5 Although not all patients or pathologies can be treated with MIS techniques, there is strong demand for MISS from patients. This demand has an economic impact on health care delivery as approximately 13% of employer-sponsored health care insurance dollars are part of “consumer-directed” plans, and this percentage is increasing.6 This has allowed patients to seek elective surgical care on the basis of their perceptions and preferences. Narain et al. administered a questionnaire to spine patients scheduled for a preoperative spine consultation7; among the 326 patients who responded to the questionnaire, the most important factors driving their preferences were long-term surgical outcomes, the recommendation of their surgeon, and the complication risk. They found that the majority of patients surveyed would prefer MIS to open surgery. Patients indicated they believed MIS is less painful, has a lower risk of complications, is less expensive, and requires a lower level of sedation. The patients surveyed perceived minimally invasive and open surgery to offer similar outcomes, with neither option increasing the chances of requiring a future reoperation. Most indicated they would seek the opinion of another surgeon if MISS options were not offered in their initial surgical consultation. Forty-four percent would travel “somewhat or much further” to seek the opinion of a surgeon who offered MISS. Interestingly, regarding surgeon skill, many patients preferred their surgeon to have more experience if offering open surgery instead of MISS. While patients did indicate that cost was not a prominent factor in deciding between MISS and open surgery, potential cost advantages have become a focus for hospital administrators as well as payors. Several retrospective studies have evaluated cost differences between MISS and open spinal surgery. Specifically, 14 studies have evaluated cost differences between minimally invasive and open laminectomy, microdiscectomy, transforaminal lumbar interbody fusion, posterior lumbar interbody fusion, and anterior lumbar interbody fusion (ALIF).8 All found MISS to be associated with reduction in direct costs of between 2% and 20%. In studies providing detailed accounting of direct costs, MISS procedures were associated with higher intraoperative direct costs but overall lower direct costs due to shorter length of hospital stay and fewer postoperative services needed during admission.

In the present article, part 1 of a 3-part series, we describe several of the unique approach techniques in MISS that have become foundational in their standalone use and their application in combination to achieve larger surgical goals. We then examine the current state of the field through an examination of the imaging and navigation technologies that have coevolved and shaped the field. In part 2 of this series (“Challenges Hindering Widespread Adoption of Minimally Invasive Spinal Surgery”),9 we present some of the challenges in MISS and proposed solutions. In the final article (“The Future of Minimally Invasive Spinal Surgery”),10 we discuss the future direction of MISS.

Section snippets

Unique Approaches in MISS

Successful minimally invasive techniques for resection, decompression, and fusion for a variety of pathologies throughout the spinal axis have been well described. Tubular retraction, endoscopy, the use of lateral corridors for interbody fusion, and navigated percutaneous pedicle screw insertion are techniques which have proven fundamental in MISS. These techniques are used in standalone surgeries or in combination with other techniques as part of a larger operation. Here, we describe these

Choosing the Right Approach

Table 2, Table 3, Table 4, Table 5 outline the indications, contraindications, spinal-level accessibility, and advantages/disadvantages of the common MISS approaches for lumbar fusion.

When evaluating the surgical approaches to a given spinal pathology at our institution, rather than employing a “one-size-fits-all” mentality toward MISS, we identify the open and minimally invasive approaches capable of dealing with a given pathology and select the best one for the individual patient. This

Fluoroscopy

The changes in intraoperative imaging modalities as they relate to pedicle screw placement illustrate the way that technological advances have shaped MISS. One of the first technologies adapted to pedicle screw placement was intraoperative fluoroscopy. With fluoroscopic methods, the meticulous exposure of surrounding landmarks that were required to ensure accurate starting points and trajectories for freehand screw placement was no longer necessary. Freehand techniques required the surgeon to

Robotic Spine Surgery

General surgeons and surgical subspecialists have successfully incorporated robots into routine use in the operating room for a variety of procedures, including cholecystectomy,49 radical prostatectomy,50 and colectomy.51 The ability to generate high-fidelity, real-time 3D CT–acquired anatomy and correlate it precisely with the spatial relationship of surgical instruments has provided the opportunity for automation. In robotic spinal instrumentation, a robotic arm (rigidly fixed to the surgical

Cortical Bone Trajectory

The ability to place spinal instrumentation with the aid of 3D intraoperative navigation has enabled the widespread investigation of different techniques with the goal of improving biomechanical stability and/or safety. In 2009, Santoni et al. described the cortical bone trajectory (CBT) for lumbar pedicle screws.56 Rather than using an entry point at the junction of the transverse process and facet and traveling mainly through cancellous bone as is the case with traditional pedicle screws, the

Virtual and Augmented Reality

Augmented reality (AR) in the operating room involves the virtual superimposition of anatomic structures or artificial targets onto actual patient anatomy. Either via specialized goggles or the eyepiece of the operative microscope, AR allows for lesions or areas of interest, such as pedicle screw starting points or surrounding anatomy, to be identified via CT or magnetic resonance imaging and superimposed in real time in the correct spatial orientation and position. In addition to robust

Conclusions

Technological advancements have enabled the safe adaptation of minimally invasive techniques in spine surgery. The best-quality evidence available suggests that in well-selected patients, MISS outcomes are similar to those achieved with open surgery and that MISS techniques offer a favorable safety profile. Although these increasingly technologically advanced techniques are accompanied by high upfront costs, studies to date suggest that the high upfront costs of MISS equipment are defrayed by

CRediT authorship contribution statement

Jacob L. Goldberg: Conceptualization, Formal analysis, Investigation, Writing – original draft, Writing – review & editing, Visualization. Roger Härtl: Conceptualization, Investigation, Writing – review & editing, Visualization. Eric Elowitz: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Resources, Writing – original draft, Writing – review & editing, Visualization, Supervision.

Acknowledgments

The authors appreciate Dr. Philip Stieg for his leadership and support of “From the Annals of Weill Cornell Neurological Surgery” and Dr. Michael L. J. Apuzzo for his guidance and input in this project. They also acknowledge the contribution of Anne Stanford, ELS, who provided professional editing services.

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  • Cited by (0)

    Conflict of interest statement: Roger Härtl reports the following: consulting in DePuy Synthes, Brainlab, and Ulrich; royalties from Zimmer Biomet; and investor in RealSpine. Eric Elowitz reports the following: consulting in Medtronic and Joimax. Jacob L. Goldberg has no conflicts to report.

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