Summary and Outlook—Future of Lumbar Minimally Invasive Surgery

56 Summary and Outlook—Future of Lumbar Minimally Invasive Surgery

Joel Martin, Laura Hein, Vincent Cheung, and William Taylor

Summary

Minimally invasive spine surgery continues to expand both procedurally and in interest to patients. We review possible future directions for this expanding field.

Keywords: minimally invasive surgery (MIS) lumbar minimally invasive surgery transforaminal lumbar interbody fusion (TLIF) posterior lumbar interbody fusion (PLIF) diffusion of innovation

56.1 Adoption and Diffusion

Lumbar minimally invasive spine surgery has continued to evolve in the past decade, although with the rapidity initially projected. In 2016, approximately one-third of all surgeries were done with the minimally invasive approach and it was estimated that by 2020, approximately half of all surgeries will be conducted using these methods.1 Despite multiple positive studies and continued expansion of techniques, the adoption rate of minimally invasive spine surgery has not been as rapid as initially expected. This is often compared with the case of laparoscopic procedures, in which within a span of 1 to 2 years, abdominal surgeries done via laparoscopic technique almost completely supplanted open procedures, and rapidly became the standard of care. This certainly has not happened as quickly in the case of minimally invasive spine surgery despite multiple studies showing that minimally invasive approaches to spinal surgery offer decreases in blood loss, length of stay, infection rates, and have similar, if not improved, outcomes to open procedures. Leaders in minimally invasive surgery (MIS) have described a possible upper limit on MIS techniques and have postulated whether MIS has reached its maximum capability.¹

Rate-limiting factors such as enhanced learning curves and uncertain applications in complex spinal disease have been suggested to impose a significant limitation in the adoption and diffusion of lumbar MIS techniques. In his classic writing on the diffusion of innovation topic published in 1983, Rodgers predicted an initial steep adoption curve as innovators and early adopters led the way to early adoption. Eventually, the market share of the innovation reaches saturation, much like the laparoscopic cholecystectomy and appendectomy have experienced, and what is currently being seen with robotic assisted prostatectomies.² Perhaps the reason why this trend is not being observed in lumbar MIS lies in the issue of technical complexity? The diffusion of medical techniques differs significantly from diffusion of new products and equipment. These features are described by Hinsch et al in 2014, which suggests that diffusion of technique also requires diffusion agents and interpersonal interaction, along with technical performance. Hinsch et al also purport that diffusion of technique is a prerequisite for diffusion of any related product or technology.³ It can been suggested that minimally invasive lumbar spine surgery is more likely a diffusion of technique in which interaction between potential adopters and diffusion agents is the most important factor affecting adoption. For example, a classic diffusion of technique related to MIS of spine is akin to the diffusion of anterior, as opposed to standard lateral, hip replacement. The reasons are very similar, as the lateral approach is a well-respected technique in which many patients do very well, similar to open lumbar spine surgery. In addition, the latter technique is well established, and the anterior approach does not require new specific technology but rather the diffusion of training and technique.

56.2 Patient Care and Procedures

The question of standard of care for lumbar MIS still remains. Lumbar MIS has been defined as “one that by virtue of the extent and means of surgical technique will results in less collateral tissue damage, results in measurable decrease in morbidity and more rapid functional recovery than traditional exposures, without differentiation in the intended surgical goal.”⁴ Inclusive evidence has been reported on both nonfusion techniques, including MIS microdiscectomy, direct decompression (laminectomy/laminotomy), indirect decompression (interspinous process devices), as well as minimally invasive (MI) fusion techniques including percutaneous pedicle screw fixation, MIS transforaminal lumbar interbody fusion (TLIF), posterior lumbar interbody fusion (PLIF), and lateral lumbar interbody fusion (LLIF). Nonfusion techniques require a learning curve, and as expected, evidence suggests that clinical outcomes are similar in open and MIS cohorts.⁵^,⁶^,⁷^,⁸^,⁹

Despite similar clinical outcomes, decreased blood loss, shorter hospitalization, and cost savings seen in fusion lumbar MIS, the increased radiation exposure and learning curve may affect its overall use.¹⁰^,¹¹^,¹²^,¹³ Evidence demonstrates that the use of MIS versus open surgery for lumbar disc herniation reaches clinical equipoise, but MIS can be inferior in regard to pain relief of the legs and lower back, quality-of-life, and rehospitalization rate.¹⁴ For fusion cases, three randomized controlled trials have demonstrated that MIS-TLIF demonstrates advantages, most prominently in reduced hospitalization, cost, and time to return to work.¹⁴^,¹⁵^,¹⁶^,¹⁷ From this literature, it appears that more complicated procedures have a larger opportunity to gain from MIS. Simple discectomy, done with MIS, may serve best as a learning tool for more complicated procedures to follow, and therefore complicated deformity procedures should not be a surgeons’ initial MIS and learning can occur progressively along a natural pathway. Clinical success with MIS appears more likely than with non-MIS fusions, but while these data are intriguing, they should be interpreted cautiously considering the level of heterogeneity of the studies available. Further, high-quality comparative studies are warranted to better understand the relative benefits of more complex interbody and MIS fusions for these conditions. Patient selection and matching the procedure to specific pathology remains key, along with appropriate technique.

In terms of minimally invasive approach (Fig. 56.1), LLIF and oblique lumbar interbody fusion (OLIF) have changed practice patterns in lumbar MIS in an unprecedented way. Minimally invasive posterior approaches have evolved in an attempt to reduce approach related complications. Anterior/lateral approaches avoid the spinal canal, cauda equina, and nerve roots, along with muscular insertions using a unique natural tissue plane to the spine. With its high fusion rates, well-established complication profile, and ability for use in routine degenerative or complex deformities, the adoption and proliferation of minimally invasive fusion techniques have been rapid. A study by Watkins et al of 220 consecutive patients with 309 operative levels were compared by surgery type, namely, anterior lumbar interbody fusion or ALIF (184 levels), LLIF (86 levels), and TLIF (39 levels), with an average follow-up of 19.2 months. They concluded that improvement of lordosis was significant for both the ALIF and LLIF groups, but not the TLIF group. Intergroup analysis showed the ALIF group had significantly improved lordosis compared to both the other groups. The ALIF and LLIF groups had significantly increased disc height compared to the TLIF group. All the three groups showed significantly reduced spondylolisthesis, with no difference between the groups.¹⁸ A recent review analyzed fusion, complications, and clinical success for lumbar fusion performed with various surgical technique, and found that PLIF-All, TLIF-All, and LLIF had significantly higher odds of fusion than instrumented posterior lateral fusion (Table 56.1), most notable for PLIF with an odds ratio of 3.2. ALIF had a slightly lower odds of fusion compared to PLIF (odds ratio 0.47), and MIS procedures had significantly higher odds of fusion than non-MIS (OR 2.20). Lastly, consistent with previously reported studies, instrumented PLF had significantly higher fusion odds than uninstrumented PLF (OR 2.20).¹⁹

Table 56.1 Odds ratio of fusion, complications, and clinical success between fusion techniques

Comparison	Fusion	Complications	Clinical success
ALIF-All vs. instrumented PLF	1.51 [1.15, 1.99]	0.89 [0.69, 1.15]	2.29* [1.86, 2.81]
PLIF-All vs. instrumented PLF	3.20* [2.53, 4.04]	0.65* [0.54, 0.79]	3.60* [3.03, 4.29]
TLIF-All vs. instrumented PLF	2.46* [1.90, 3.18]	0.54* [0.42, 0.70]	4.80* [3.95, 5.85]
LLIF vs. instrumented PLF	2.20* [1.55, 3.10]	1.66* [1.29, 2.14]	0.51* [0.40, 0.65]
Circumferential vs. instrumented PLF	1.49 [1.18, 1.89]	1.11 [1.09, 1.64]	1.19 [0.98, 1.44]
Instrumented vs. uninstrumented PLF	2.20* [1.74, 2.69]	1.00 [0.76, 1.42]	1.10 [0.86, 1.52]
ALIF vs. PLIF-All	0.47* [0.34, 0.66]	1.37 [1.02,1.79]	0.63* [0.50, 0.80]
ALIF vs. TLIF-All	0.62 [0.43, 0.87]	1.65 [1.10, 2.30]	0.48* [0.37, 0.61]
ALIF vs. LLIF	0.69 [0.45, 1.05]	0.54* [0.39, 0.74]	4.50* [3.38, 6.01]
PLIF-All vs. TLIF-All	1.30 [0.95, 1.79]	1.21 [0.91, 1.59]	0.75 [0.60, 0.94]
PLIF-All vs. LLIF	1.46 [0.98, 2.16]	0.39* [0.30, 0.52]	7.10* [5.44, 9.27]
TLIF-All vs. LLIF	1.12 [0.75, 1.68]	0.33* [0.24, 0.45]	9.47* [7.15, 12.5]
PLIF-MIS vs. PLIF non-MIS	1.01 [0.62, 1.64]	1.08 [0.75, 1.52]	18.6* [10.8, 32.1]
MIS-TLIF vs. TLIF non-MIS	0.95 [0.59, 1.58]	0.84 [0.48, 1.47]	12.3* [7.17, 21.1]
PLIF-MIS vs. MIS-TLIF	1.34 [0.76, 2.41]	1.45 [0.81, 2.58]	1.15 [0.56, 2.37]
MIS vs. non-MIS	1.59* [1.32, 1.90]	1.20 [1.03, 1.41]	2.44* [2.16, 2.75]
Biologic vs. no biologic	2.29* [1.75, 2.99]	1.28 [1.05, 1.55]	3.40* [2.82, 4.10]
Abbreviations: ALIF, anterior lumbar interbody fusion; LIF, lumber interbody fusion; LLIF, lateral lumbar interbody fusion; MIS, minimally invasive surgery; PLF, posterolateral fusion; PLIF, posterior lumbar interbody fusion; TLIF, transforaminal lumbar interbody fusion. Source: Reproduced with permission from Makanji H, Schoenfeld AJ, Bhalla A, Bono, CM. Critical analysis of trends in lumbar fusion for degenerative disorders revisited: influence of technique on fusion rate and clinical outcomes. Eur Spine J. 2018;5. Notes: *Significant p < 0.0025.

Fig. 56.1 (a) Surgical approaches to the lumbar spine for interbody fusion techniques. The five primary interbody fusion approaches are shown here schematically: anterior lumbar interbody fusion (ALIF), lateral or extreme lateral interbody fusion (LLIF or XLIF), oblique lumbar interbody fusion/anterior to psoas (OLIF/ATP), transforaminal lumbar interbody fusion (TLIF or MI-TLIF), and posterior lumbar interbody fusion (PLIF). (Reproduced from Raheja A, Tandon V, Garg K et al. A Review of Minimally Invasive Techniques in Thoracolumbar Trauma. Indian Journal of Neurotrauma 2021; 18(01): 07-13.)

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