Is minimally invasive surgery a game changer in spinal surgery?

Tubular retractor systems

The introduction of tubular retractors in the late 1990s marked a significant advancement in MISS. The METRx system, introduced in 1997, enabled surgeons to perform microdiscectomies through a muscle-splitting approach, minimizing tissue disruption while maintaining adequate visualization [4]. This technology paved the way for a variety of tubular-based procedures, including microdecompression for spinal stenosis and minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) [5].

The advantages of tubular approaches are well-documented. A meta-analysis by Goldstein et al. [6] comparing tubular microdiscectomy to open microdiscectomy found comparable clinical outcomes with significantly less surgical site pain and shorter length of hospital stay in the tubular group. Several subsequent studies have corroborated these findings, establishing tubular techniques as a cornerstone of MISS.

The tubular systems have continued to evolve, with significant advances in design and functionality. The development of expandable retractors and specialized instruments has helped optimize procedures through these narrow corridors. Recent advancements include integrated light sources and suction capabilities, further enhancing intraoperative visual access and efficiency.

Percutaneous pedicle screw fixation

Percutaneous pedicle screw fixation, introduced in the early 2000s, marked a significant milestone in minimally invasive spinal stabilization [7]. This technique enables surgeons to place pedicle screws through small stab incisions, avoiding the extensive muscle dissection required in traditional open approaches.

A systematic review and meta-analysis by Phan et al. [8] compared percutaneous and open pedicle screw fixation in 1,028 patients. The results demonstrated significantly lower blood loss and shorter hospital stays in the percutaneous group, with no significant difference in operative time or complication rates [8]. These findings underscore the potential benefits of percutaneous techniques in reducing surgical morbidity.

The accuracy of percutaneous pedicle screw placement has been extensively investigated. A meta-analysis by Perdomo-Pantoja et al. [7] analyzing 48,757 percutaneously placed pedicle screws reported an overall accuracy rate of 93.3%, a figure comparable to traditional open techniques. The integration of navigation and robotic systems has further improved the accuracy of percutaneous screw placement, with some studies reporting accuracy rates exceeding 98%.

Minimally invasive transforaminal lumbar interbody fusion

MI-TLIF has emerged as a leading MISS technique since its introduction in the mid-2000s. This versatile approach effectively treats various lumbar pathologies, including degenerative disc disease, spondylolisthesis, and recurrent disc herniation [9]. This technique combines the principles of minimally invasive decompression, interbody fusion, and percutaneous pedicle screw fixation (Fig. 1).

Fig. 1

(A) Severe central stenosis observed in a 65-year-old male patient. (B) Intraoperative C-arm images after positioning the tubular retractor. (C) Intraoperative microscopic image showing endplate preparation using a reamer (white arrowhead). (D) Three small incisions visible: the right-side incision for the tubular retractor and two for percutaneous screw insertion. (E, F) Postoperative anteroposterior and lateral radiographs demonstrating well-positioned interbody cage and four percutaneous pedicle screws.

A comprehensive meta-analysis by Hu et al. comparing MI-TLIF to open TLIF found that MI-TLIF was associated with significantly less blood loss, shorter hospital stays, and lower complication rates [10]. Importantly, there were no significant differences in terms of operative time, fusion rates, or clinical outcomes between the two techniques.

The long-term outcomes of MI-TLIF have also been encouraging. A prospective study by Adogwa et al. [9] enrolling 148 patients undergoing MI-TLIF found sustained improvements in back pain, leg pain, and disability, with a fusion rate of 96% at 5 years. These results suggest sustained benefits of MI-TLIF over time. Recent advancements in MI-TLIF techniques include the use of expandable interbody cages, which allow the insertion of larger implants through small working channels, potentially improving lordosis restoration and indirect decompression [11].

Lateral lumbar interbody fusion

Developed in the late 2000s, lateral lumbar interbody fusion (LLIF) techniques, including extreme lateral interbody fusion and oblique lateral interbody fusion (OLIF), provide an alternative approach to interbody fusion [12]. These techniques entail gaining access to the disc space through a retroperitoneal approach, avoiding disruption of the posterior musculature and facet joints (Fig. 2).

Fig. 2

Lateral lumbar interbody fusion in a 62-year-old male patient. (A, B) Severe central stenosis with mild spondylolisthesis and centrally herniated disc observed preoperatively. (C, D) Lateral interbody fusion with percutaneous screw fixation, showing significantly restored intervertebral disc height.

A systematic review by Hijji et al. [12] analyzing 6,819 patients undergoing LLIF found high fusion rates and significant improvements in patient-reported outcomes, with a relatively low overall complication rate. The most common complications were transient thigh symptoms (36.07%), which typically resolved within 6 months postoperatively [13].

LLIF techniques have been particularly useful in treating adult spinal deformity and multi-level degenerative disc disease. A multicenter study by Berjano et al. [14] involving 12 patients undergoing LLIF for adult spinal deformity reported significant improvements in coronal Cobb angle and sagittal vertical axis. The study concluded that LLIF, when combined with posterior percutaneous fixation, can achieve meaningful deformity correction with reduced morbidity compared to traditional open techniques. Recent innovations in LLIF include the development of navigation-assisted techniques and specialized retractor systems designed to minimize the risk of neural complications [15].

Endoscopic spine surgery

The most recent advancement in MISS is the emergence of endoscopic techniques, which have gained widespread acceptance since the 2010s. These cutting-edge procedures are performed through a single small incision using specialized endoscopes with working channels, allowing for decompression and discectomy under continuous visual access [16].

A meta-analysis by Shi et al. [17] comparing full-endoscopic to microendoscopic discectomy found comparable clinical outcomes with significantly shorter operative time and hospital stay in the full-endoscopic group. These findings suggest that full-endoscopic techniques may offer advantages in terms of surgical efficiency and recovery time. The applications of full-endoscopic spine surgery have expanded beyond simple discectomies to include more complex procedures such as foraminotomy, central canal decompression, and even interbody fusion [18]. One of the main challenges associated with full-endoscopic techniques is the steep learning curve. The importance of structured training programs and proctorship to ensure the safe adoption of these techniques has been emphasized [19].

Intraoperative navigation

Intraoperative navigation systems have transformed the landscape of MISS, particularly in the realm of pedicle screw placement. By seamlessly integrating preoperative or intraoperative imaging with real-time instrument tracking, these advanced systems provide surgeons with unparalleled precision, enhanced accuracy, and improved safety.

A meta-analysis by Tian et al. [20] demonstrated the superiority of navigation-assisted pedicle screw placement over freehand techniques in terms of improved screw placement accuracy and reduced risk of cortical perforation. This improved accuracy translates to enhanced patient safety and potentially reduced reoperation rates for screw malposition.

Robotics

Robotic assistance in spine surgery represents a natural evolution of navigation technology, aiming to enhance the precision and consistency of procedures [21]. While still in its early stages, robotic spine surgery shows promise in improving accuracy and potentially reducing complications. Moreover, the integration of robotic assistance with navigation systems can potentially mitigate concerns related to distorted anatomical landmarks, thereby enhancing the overall surgical outcomes [22] (Fig. 3).

Fig. 3

Robot-assisted pedicle screw fixation.

Robotic assistance has been highlighted as a valuable tool for pedicle screw placement in LLIF procedures. Studies have shown that robotic-guided pedicle screw placement can increase accuracy, reduce operative time, and decrease radiation exposure, making it particularly advantageous in MISS [15].

Augmented reality

Augmented reality (AR) systems represent the cutting edge of visualization technology in spine surgery. By overlaying computer-generated images onto the surgeon’s view of the operative field, AR enables real-time, three-dimensional (3D) visualization of patient anatomy and surgical instrumentation [23,24] (Fig. 4).

Fig. 4

(A–E) Augmented reality-assisted spine surgery. OP field, operative field; IR, infrared camera.

Initial studies on AR in spine surgery have demonstrated its potential for improving pedicle screw placement accuracy. A pilot study by Elmi-Terander et al. [25] using an AR surgical navigation system for thoracic pedicle screw placement achieved an accuracy rate of 94.1%, comparable to conventional navigation systems. The AR system enabled continuous visualization of the screw trajectory without diverting gaze from the surgical field, potentially improving workflow efficiency. A feasibility study by Müller et al. [26] using a head-mounted AR display for pedicle screw fixation achieved accuracy comparable to the gold standard of high-end pose-tracking systems.

Decompression procedures

Minimally invasive decompression techniques, including tubular discectomy and endoscopic decompression, have been widely adopted for the treatment of lumbar disc herniation and spinal stenosis. A Cochrane review by Overdevest et al. [27] analyzed data from 10 randomized controlled trials comparing minimally invasive to open decompression for lumbar spinal stenosis. The authors found no significant differences between the two techniques in terms of leg pain, disability, or walking ability at long-term follow-up. However, minimally invasive techniques were associated with less low back pain in the short term and shorter hospital stays [27]. For lumbar disc herniation, a meta-analysis by Ruan et al. [28] comparing percutaneous endoscopic lumbar discectomy to open microdiscectomy found comparable rates of postoperative back pain, complications, reoperation, and Oswestry Disability Index (ODI).

Recent clinical studies have consistently demonstrated the efficacy of biportal endoscopic lumbar discectomy in treating lumbar disc herniation. In a multicenter, retrospective study, the clinical outcomes of biportal endoscopic discectomy were similar to those of open microscopic discectomy, with benefits such as minimal estimated blood loss, shorter hospital stay, and reduced early postoperative back pain [29,30]. Moreover, biportal endoscopic lumbar discectomy has also shown promising results in obese individuals, highlighting its potential as a viable treatment option for this specific patient population [31,32]. Furthermore, biportal endoscopic laminectomy has been shown to be a satisfactory option for patients with lumbar spinal stenosis, offering favorable clinical outcomes and potentially improving postoperative recovery [33–38].

Fusion procedures

Minimally invasive fusion techniques, particularly MI-TLIF, LLIF, and endoscopic lumbar interbody fusion (LIF) have become increasingly popular for treating various lumbar pathologies requiring arthrodesis. A network meta-analysis by Lu et al. [39] comparing various LIF techniques found that MISS was associated with the lowest risk of surgical site infection and the shortest hospital stay compared to open techniques, while clinical outcomes, including improvements in pain and disability scores, remained comparable across techniques. In a recent meta-analysis by Zhang et al. [40], the OLIF group showed more significant improvement in Visual Analog Scale (VAS) score for radiating pain, while the improvements in VAS score for back pain and the ODI scores were comparable. OLIF was associated with a significantly shorter duration of surgery and less intraoperative blood loss than minimally invasive surgery (MIS)-TLIF, even with supplementary posterior fixations.

Full-endoscopic LIF demonstrated promising initial results, outperforming MIS-TLIF in terms of blood loss and VAS score for back pain [41]. However, no significant differences were observed between the two techniques in terms of complications, short- or medium-term clinical outcomes, and fusion rates. The clinical and radiographic outcomes of biportal endoscopic LIF were comparable to those of MIS-TLIF [42] (Fig. 5).

Fig. 5

(A, B) Patient with severe central stenosis and grade 1 spondylolisthesis at L4–5 undergoing biportal endoscopic transforaminal interbody fusion. (C) Biportal endoscopic approach providing clear visualization of endplate preparation, enabling complete preparation (black arrowhead). (D) Safe cage insertion achieved under endoscopic guidance. (E) Six small incisions visible: two for endoscope access and four for percutaneous screw insertion. (F) Postoperative lateral lumbar radiograph showing anteriorly positioned lumbar cage and four inserted pedicle screws.

Deformity correction

MISS techniques for adult spinal deformity correction have been an area of significant interest and innovation in recent years [43]. Recent studies demonstrate that MISS techniques reduce overall complication rates associated with deformity correction surgeries [44]. While open surgery remains the gold standard, MISS has shown satisfactory clinical outcomes for deformity correction. Furthermore, minimally invasive approaches using long spinal constructs have been explored for assessing fractures, tumors, or deformities, particularly in elderly or debilitated patients [45]. The concept of a triad of MIS procedures for adult spinal deformity (ASD) includes anterior column realignment, LLIF, and percutaneous pedicle screw fixation. This combination is suggested to reduce the number of fusion segments required for normalizing spinopelvic mismatch while providing indirect neural decompression [46].

Cost-effectiveness

The economic impact of MISS has garnered significant attention amidst rising healthcare costs and the emphasis on value-based care. Research has shown that MISS procedures can offer substantial cost savings. For example, a comparative analysis of MI-TLIF and open TLIF revealed that higher implant costs of ML-TILF were offset by lower overall hospital costs, driven by shorter lengths of stay and reduced complication rates [47]. When factoring in societal costs, such as earlier return to work, the cost savings associated with MI-TLIF were even more pronounced. Additional studies have highlighted the cost disparity between open and MI-TILF, with open TLIF incurring significantly higher costs–averaging US$ 4,038–compared to MI-TLIF [48]. In the realm of lumbar discectomy surgeries, endoscopic procedures, such as full-endoscopic and biportal endoscopic discectomy, have proven more cost-effective than microscopic discectomy [49].