|SYMPOSIUM - MINIMALLY INVASIVE SPINE SURGERY
|Year : 2020 | Volume
| Issue : 1 | Page : 26-33
A review of minimally invasive techniques for correction of adult spine deformity
Aniruddh Agrawal1, Neel Anand2, Anisha Agrawal1
1 Topiwala National Medical College, Mumbai, Maharashtra, India
2 Department of Orthopaedic Surgery, Cedars Sinai Medical Center, Los Angeles, CA, USA
|Date of Submission||29-Apr-2019|
|Date of Decision||13-Aug-2019|
|Date of Acceptance||30-Oct-2019|
|Date of Web Publication||05-Feb-2020|
Mr. Aniruddh Agrawal, Topiwala National Medical College, 401 Sony House, Cd Barfiwala Road, Andheri West, Mumbai 400056, Maharashtra.
Source of Support: None, Conflict of Interest: None
This paper highlights the current status of minimally invasive surgery (MIS), with special attention to learning curve, cost-effectiveness, and different techniques, for the correction of adult spine deformity (ASD). A literature review was performed through the PubMed database. Studies that fit the inclusion criteria (n = 27) were analyzed by the authors through the MINORS criteria and their results were then presented. The abundance of data on the learning curve of the procedure shows that it takes at least 22–39 surgeries for a surgeon to reach optimal operative time. The literature search showed that there is a paucity of data available on the cost-effectiveness of the procedure in developing countries; however, if the results from the developed countries were to be considered, MIS is cost-effective for ASD correction. There are certain limitations to the procedure including inadequate sagittal balance as well as chances of proximal junctional kyphosis and adjacent segment disease; however, the overall benefits of MIS including decreased operative time, blood loss, and hospital stay could tilt the balance in its favor.
Keywords: Cost-effective, learning curve, minimally invasive surgery, scoliosis
|How to cite this article:|
Agrawal A, Anand N, Agrawal A. A review of minimally invasive techniques for correction of adult spine deformity. Indian Spine J 2020;3:26-33
|How to cite this URL:|
Agrawal A, Anand N, Agrawal A. A review of minimally invasive techniques for correction of adult spine deformity. Indian Spine J [serial online] 2020 [cited 2020 Feb 27];3:26-33. Available from: http://www.isjonline.com/text.asp?2020/3/1/26/277806
| Introduction|| |
Adult spine deformity (ASD) refers to a set of conditions involving abnormal spinal alignment leading to a range of symptoms including pain, neurologic dysfunction, and gross physical deformity. It is most often defined as a condition occurring in patients who are at least 18 years old with a coronal Cobb angle greater than 20°, sagittal vertebral axis (SVA) greater than 5cm, and/or pelvic tilt (PT) greater than 20°.
Although open surgeries have been traditionally used for complex spine deformities, often with use of multilevel decompression and fusion, there has been a rise in the use of minimally invasive techniques for spinal deformities. These techniques were initially introduced to minimize approach-related morbidity associated with open spine surgeries. During the past decade, there has been a rapid evolution of minimally invasive surgeries (MISs) in the treatment of complex spinal pathologies. Recent literature shows that MIS, in addition to having better cosmetic results, has also decreased blood loss, shorter operative time, and quicker postoperative recovery.,,,, MIS can be classified based on two parameters. One is the invasiveness of the operation and the degree to which the MIS techniques are used, and the other is the approach to the spine that is used.,,
On the basis of the degree to which MIS is used, it can be divided into the following:
- (a) MIS decompression. It involves minimally invasive decompression with or without single-level/short-segment fusion in patients with mild spinal deformity and symptoms primarily of neural element compression.
- (b) Circumferentially minimally invasive surgery (cMIS). It involves 360° deformity correction with anterior column support (interbody graft placement) and posterior segmental instrumentation through an entirely MIS approach.
- (c) Hybrid surgery. It involves the incorporation of lateral MIS techniques with a traditional “open” posterior surgery, which includes segmental osteotomies and instrumentation.
Although cMIS and hybrid surgery are sometimes confused, cMIS differs from hybrid surgery as it involves sparing the paraspinal muscles and preserving the posterior ligamentous tension band.
There are multiple ways to approach the spine with an MIS technique. These include transforaminal lumbar interbody fusion (TLIF), lateral lumbar interbody fusion (LLIF), MIS anterior lumbar interbody fusion (ALIF), MIS placement of iliac screws, MIS placement of percutaneous screws, MIS rod rotation and reduction techniques, as well as MIS posterior pars-facet complex fusion. However, most of these techniques have their own limitations, pose technical challenges, are associated with technical complications, and are accompanied by a learning curve.,,,,
The aim of this paper was to highlight information about the current practices in the use of MIS for correction of ASD through literature review and analysis with special attention to limitations, learning curve, and cost-effectiveness of various MIS techniques.
| Materials and Methods|| |
Literature search strategy
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed for the present systematic review. Electronic searches were performed using Ovid MEDLINE, PubMed, Cochrane Central Register of Controlled Trials (CCTR), and the Cochrane Database of Systematic Reviews (CDSR). The search was limited to clinical studies with the following key terms: “minimally invasive,” “surgery,” “adult,” “spine,” “deformity,” and “scoliosis.” The search criteria used for PubMed are as follows:
Minimally [All Fields] AND invasive [All Fields] AND “scoliosis” OR “scoliosis” [All Fields])
Minimally [All Fields] AND invasive [All Fields] AND “deformity” [All Fields]
Minimally [All Fields] AND invasive [All Fields] AND (“scoliosis” OR “scoliosis” [All Fields]) AND (“adult” OR “adult” [All Fields])
Minimally [All Fields] AND invasive [All Fields] AND “deformity” [All Fields]) AND (“adult” OR “adult” [All Fields])
Minimally [All Fields] AND invasive [All Fields] AND (“scoliosis” OR “scoliosis” [All Fields]) AND Cost [All Fields]
Minimally [All Fields] AND invasive [All Fields] AND (“scoliosis”  OR “scoliosis” [All Fields]) AND “deformity” [All Fields]) AND Learning [All Fields]
A filter for studies published in 2005 or later and English language was applied. The reason of this time cutoff was to equalize results of open surgery to MIS and hybrid techniques that are developed in last decade and to more appropriately reflect the data associated with current techniques.
Two authors performed the search independently, and any discrepancies were resolved by discussion. The reference lists of all retrieved articles were reviewed for further identification of potentially relevant studies, assessed using the inclusion and exclusion criteria.
Selection criteria and critical appraisal
Eligible studies for the present systematic review included those in which patient cohorts underwent MIS for adult degenerative scoliosis. When institutions published duplicate studies with accumulating numbers of patients or increased length of follow-up, only the most complete reports were included for quantitative assessment. All publications were limited to those involving human subjects and in the English language.
Titles and abstracts generated by the search in these databases were excluded from full-text review according to the following exclusion criteria: anatomical descriptions, case reports, commentaries, literature reviews, and studies addressing congenital idiopathic scoliosis. Two investigators independently reviewed each retrieved full-text article. Discrepancies between the two reviewers were resolved by discussion and consensus. The quality of the selected studies was judged by using the methodological index for nonrandomized studies (MINORS).
The inclusion criteria were the following:
Articles in English published in 2005 or later.
Articles providing quantitative results with respect to perioperative (≤3 months) and late (>3 months) complications specific to ASD surgery with open, MIS, and hybrid procedures.
Retrospective or prospective studies including randomized-controlled trials, nonrandomized trials, cohort studies, case–control studies, and case series.
The exclusion criteria were the following:
Articles that did not provide clear quantitative data specific to complications of ASD surgery.
Articles with patients’ age <18 years.
Articles that did not have more than 95% of patients undergoing instrumented surgeries.
Studies including tumor-related deformity or with congenital scoliosis.
| Results|| |
The results presented are based on a thorough literature search in the PubMed database. A total of 476 references were found from the electronic database search. After exclusion and inclusion criteria were applied, 38 references remained for full-text evaluation. After final application of criteria and removal of repeats, 27 studies were included in the present review for analysis [Figure 1].,,,,,,,,,,,,,,,,,,,,,,,,,,
- (a) Indications of MIS. A systematic analysis was not included in this review on the indications of minimally invasive spine surgery for ASD as much evidence exists on this topic in the form of reviews and meta-analysis. Information about the current literature on the same has been added for the sake of completeness.There is no consensus on when MIS should be performed and what MIS technique should be used for a particular pathology. However, certain tools, such as the MiSLAT algorithm, exist to help the surgeon evaluate each patient into different groups to better plan the surgical procedure and follow appropriate guidelines.
- (b) Comparison of MIS, hybrid, and open techniques. A systematic analysis was not performed in this review on this comparison; however, it is important to include data that were found on a preliminary search for this. There exist enough data, in the form of systematic reviews and meta-analysis on this comparison; a few of those have been cited below.A study by Park et al., involving 105 patients with an average of four interbody fusions in both groups, compared the outcomes of cMIS and hybrid surgery in the treatment of ASD. They found that there was no statistical difference between the Oswestry disability index (ODI) and visual analog score (VAS) changes between the two groups. It also reported that the approaches are similarly effective for correcting sagittal plane deformity and improving quality of life. Another multicenter study by the Invasive Species Specialist Group (ISSG) involving 184 patients compared the MIS, hybrid, and open techniques. The study reported that although the MIS group included patients with a significantly smaller Cobb angle, the hybrid group had a significantly larger lumbar curve correction and the largest change in the pelvic index-lumbar lordosis (PI-LL). The open group not only had the greatest SVA correction but also a larger postoperative thoracic kyphosis. This study also found no statistical difference between the ODI and VAS among the three groups. Importantly, this was the early experience among all of the participating institutions.
- (c) Comparison of results of different MIS approaches.
- TLIF. It was first introduced by Blume and Harms and Jeszenszky. It represents the refinement of the posterior lumbar interbody fusion. Through this technique, you can access the disc space unilaterally using a far left trajectory through the vertebral foraminal space. It is especially used for the lumbosacral junction (L4-5 and L5-S1).Multilevel TLIF has proven itself as a promising approach for correction of deformity surgery without the patient having to undergo multiple step surgery. Wang et al. showed that the postoperative Cobb angle improved from 29.2° to 9°, whereas the global lumbar lordosis (LL) improved from 27.8° to 42.6° and the SVA improved from 7.4cm to 4.3cm. Clinically at one year follow-up, VAS for leg pain improved from 5.1 to 1.8 and VAS for back pain improved from 7.6 to 3.4, whereas the ODI improved from 44.1 to 24.1 after surgery. A systematic review by Carlson et al. concluded that although the literature was sparse, there exists much evidence to suggest that an MIS-TLIF may be adequate for restoration of LL.
- LLIF. It was developed on the foundations of the laparoscopic LLIF. The approach involves an MIS retroperitoneal trajectory to the spine. It has the distinct advantage over the ALIF by providing lateral exposure of the disc and avoiding major vessels and the peritoneal cavity. A recent systematic review by Keorochana et al. suggests that MIS-LLIF has better clinical outcomes than the traditional open technique. However, fusion rates between MIS-TLIF and MIS-LLIF are similar. Anand et al., have reported statistically significant improvements in coronal and sagittal Cobb angle including improvement in pelvic parameters with cMIS surgery involving multilevel LLIF combined with posterior percutaneous instrumentation. Wang and Mummaneni, Acosta et al., and Anand et al. showed that LLIF is an effective means of improving segmental and regional LL.,, Complications associated with LLIF include major vascular injuries (e.g., some life-threatening and others life-ending), bowel perforations, sterile seromas, and instrumentation failures.
- ALIF. In comparison to posterior accesses, the ALIF procedure can be associated with a shorter operative time, with less bleeding, and postoperative pain, reducing the length of hospitalization and withdrawal from work. A particular advantage of the ALIF technique includes the ability to restore disc height and gain lordosis. Anand et al. have shown MIS-ALIF for L5-S1 with an oblique lateral approach in conjunction with multilevel LLIF and MIS percutaneous screws to be effective in obtaining excellent correction of coronal and sagittal balance in ASD. However, severe osteoporosis increases the risk of cage subsidence and can cause loss of sagittal and coronal correction.
- (d) Learning Curve of MIS surgeries for ASD. A learning curve is defined as the time taken and/or the number of cases required by an average surgeon to become proficient (e.g., reduce operative time, estimated blood loss, and morbidity/ adverse events) to be able to perform a procedure independently with a reasonable outcome. The measures used for assessing learning of a certain procedure were mainly intraoperative continuous process variables such as operative time (45%) and intraoperative varied outcome variables such as complications (51%). Usually, in cases of minimally access surgery, time for completion of operation is given more weightage than other surgeries when assessing the learning curve. There have been varying reports on the learning curve for MIS. A single surgeon series for MIS-TLIF (single- and two-level) observed that there was a 50% improvement in proficiency by case 12 and a 90% improvement by case 39. Between these cases, complication rates also fell from 33% to 20.5%.
A more recent study by Dayani et al. described the learning curve associated with 100 screw placements. They reported that surgeons who had less experience with MIS were 33.3% more likely to have a medial pedicle breach. All cerebrospinal fluid leaks and wound infections in their cohort also occurred at the hands of less-experienced surgeons. Lee et al. assessed and compared the findings of the 100 cases of a single-level TLIF technique performed by a single surgeon. They noted that in operative parameters, only operative time, fluoroscopy time, and usage of patient-controlled analgesia were significantly higher in the first 44 cases. These cases also had a higher VAS score for back and leg pain. They therefore concluded that the asymptote of the surgeon’s learning curve for MIS-TLIF was achieved at the 44th case. In another assessment by Neal et al., a single resident/attending team performed 28 TLIF procedures and placed 65 screws. They reported no difference between pedicle screw placement accuracy between the first and second cohorts. This study also, however, reported no difference between operative times between the two cohorts. Another larger study by Lee et al. included 60 single-level TLIF patients. In the single-level TLIF series, operative time was significantly shorter in the late group (183 ± 23min) than the early group (254 ± 44min), and blood loss during the operation was significantly reduced in the late group (292 ± 280mL) as compared with the early group (508 ± 278mL). Ambulation recovery time significantly decreased from 2.4 ± 0.6 days in the early group to 2.0 ± 0.5 in the late group. ODI and VAS scores for lower back pain and radiating pain did not differ between the two groups.
One of the largest studies of TLIF learning curve was performed by Wood et al., which included 627 pedicle screws placed in 150 patients. They observed that intraoperative adjustment of screws because of electromyography and computerised tomography guidance were 5.1%, 4.3%, and 2% in the first 50, second 50, and last 50 cases, respectively. They also noted that the initial eight cases required a correction in 16% of all screws placed.
In cases of lateral access spine surgery, Chong et al. prospectively evaluated 32 patients who underwent an LLIF with supplementary posterior stabilization based on operative time and perioperative parameters. These investigators concluded that break point in operating time occurred at the 22nd operating level, with a decline in operative time from 71min to 42min. However, they found no clinically significant difference in VAS back and leg scores at one-year follow-up between the two sets of patients. Anand et al. showed that after the first 4 years or 100 cases of performing extreme lateral interbody fusion (XLIF), the complication rates were lower in their experience.
Additional experiences with the oblique lateral interbody fusion (OLIF) technique by Woods et al. in 21 patients have shown that there was no statistical difference in blood loss, operative time, or complication rate between the first 10 and last 10 patients.
- (e) Cost-effectiveness of MISRelatively little evidence exists for cost-effectiveness of MIS in ASD. Furthermore, there is a paucity of data available for the Indian MIS surgery cost-effectiveness. However, there is an abundance of research on cost-effectiveness of MIS in spinal degenerative disease.,,,,,,,,,,,,,,,, The study by Uddin et al. divided 71 patients into two groups depending on whether they underwent MIS or a traditional “open” surgery for idiopathic scoliosis. They reported that the number of levels fused in MIS surgeries was lesser, but could achieve similar clinical outcomes at follow-up. MIS surgeries cost on average $269,807, whereas “open” surgeries cost $391,889, leading to an average savings of $122,081 if MIS was performed. They however noted that there was no statistically significant difference between the out-patient rehabilitation costs between the two techniques. They attributed this reduced cost of surgery to an average of 1 week of lesser hospital stay in MIS patients as well as lesser operative time (because of decreased number of fused levels). Other factors that decreased cost of MIS surgery were decreased need for blood products and medications.
Studies involving patients treated for degenerative spine diseases also have a similar finding, which rules in favor of MIS. MIS has been reported to be cheaper than open surgery from anywhere between 2.54% and 33.6%., The study by Parker et al. was also able to make an estimate of $6,650 dollars as indirect savings in relation to missed work in open groups.A study based in Italy and the United Kingdom, which determined the cost-effectiveness by the incremental cost per quality-adjusted life-year gained, concluded that the MIS approach was dominant strategy as compared with the traditional open approach (i.e., yielding both cost savings and improved health-related quality of life [HRQOL]). They determined that total cost savings when MIS was performed were about €973 for Italy and €1666 for the United Kingdom. Moreover, it also resulted in the improvement of 0.04 quality-adjusted life-year over 2 years in HRQOL.
Overall, six studies have performed the cost analysis of single-level TLIFs,,,,, and they all reported a saving ranging from 17.13% to 19.50%. The PLIF approach has been shown to cost less than the MIS technique by 2.54%–10.56% for a single-level fusion and 5.85%–19.65% for a two level fusion.,,A more recent French study analyzed cost-effectiveness in 46 patients and concluded that it was preferential to use MISs as there was less cost to patients in terms of postoperative time to return to work.
- (f) Limitations and ceiling effects of MIS for deformity. Evidence suggests that sagittal imbalance plays a key role in affecting the health-related quality of life outcomes. This evidence is supported by the fact that a positive sagittal balance can lead to higher energy requirements to stand and ambulate, leading to early fatigue, intolerance to standing, and walking with compensation through other joints. According to Le et al. unless anterior column reconstruction is included as a part of surgery, MIS LIF only has a modest capacity to correct LL and PT. Anand et al. showed in their early experience with an older protocol that there were limitations and ceiling effects to what could be achieved with MIS techniques for ASD. The use of AxiaLIF for L5-S1 was deemed to be inferior for sagittal balance as compared with ALIF in their experience.
Although the main critique of MISs in deformity correction remains inability to improve sagittal balance to the same extent as open surgeries, anterior longitudinal ligament release with the use of hyperlordotic cages has shown promising radiographic and clinical outcome. These outcomes are almost similar to the ones achieved by the traditional Schwab’s posterior column shortening osteotomies, which have a complication rate as high as 40%., Anand et al. have shown that with a strict protocol and appropriate selection criteria, most patients with ASD without a prior fusion can be treated with MIS techniques without the need for osteotomies or ALL release. With their new protocol in effect for the past 6 years, they have shown significant improvements in coronal and sagittal parameters for these patients. MIS-LLIF can also be an option in cases of adjacent segment failure; the lateral approach avoids traversing a scarred corridor and allows placement of an intervertebral cage without the pitfalls of reoperation mentioned above. Additional fixation can be obtained using a lateral plate without the need to revise prior instrumentation. Literature is lacking for use of MIS in adjacent segment disease. However, it should always be remembered that revision surgery with severe spinal deformity continues to be a limitation for MIS approaches alone.
| Discussion|| |
Although there is an abundance of published data on learning curve and cost-effective analysis for MIS in degenerative spinal conditions, there remains a paucity of data on cases of spinal deformity. Most of the literature focuses on clinical outcomes and complications,,,,[ 77-81] which sufficiently prove that if appropriate patient selection is performed, results with MIS can match or sometimes even exceed those obtained by open surgery. These facts have already been established.
The learning curve associated with MIS for ASD has been a deterrent for many surgeons to take on this technique. There seems to be an association of “early” cases with increased rates of complication and poorer VAS scores; radiological outcomes were more or less similar throughout the learning process.,, Therefore, it is recommended that when a surgeon is starting out with the MIS technique, the initial surgeries (at least 30–44 cases till asymptote is reached), should be safely performed in a training environment because of a significantly higher rate of complications expected from the learning curve.
In a developing country such as India where cost is a significant factor for performing one technique over another, there is a need for a cost-effective analysis in the Indian hospital environment. Analysis from developed countries such as United States of America, United Kingdom, Italy, and France,,, all show that MIS has decreased direct and indirect costs by minimizing need for ICU admission and postoperative recovery period, respectively. However, these analyses may or may not hold true for a developing country and therefore need to be subject to evaluation. According to a study by Anand et al., which evaluated the prevalence of MIS use in practice by ASD surgeons, only around 7% of surgeons use MIS to treat ASD in more than 80% of their patients. This number was derived from surgeons who were members of the Scoliosis Research Society. Further evaluation into why the adoption rate is low and what is causing the hesitation of these surgeons to adopt these techniques needs to be performed.
| Conclusion|| |
MIS for ASD correction is a technique with good proven short-term and long-term clinical and radiological outcomes. However, a learning curve for the surgery exists, which can be overcome in a controlled training setup and adoption of strict protocols. Surgeon adoption of this technique is still low and the cause of the hesitance of these surgeons needs to be evaluated. Cost-effective analysis for developing countries needs to be performed to further increase the knowledge based on which surgeons can chose to perform open or MIS surgeries.
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Conflicts of interest
There are no conflicts of interest.
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