A perspective on reoperations after surgical treatments of degenerative lumbar diseases

Abstract

Clinical data including reoperation rates are comparable for lumbar patients after decompression-alone or decompression-with-fusion surgeries. However, there could exist different mechanisms causing complications after the two surgeries. We discussed research and technology development perspectives for improvement of the surgeries using published clinical outcome data.

Graphical abstract

1. The translational potential of this article

This paper provides clinical and basic scientific evidence for improvement of lumbar fusion surgeries, including surgical techniques and fusion devices, that are aimed to reduce reoperation rates after traditional decompression-alone or decompression-with-fusion surgeries in treatment of patients with lumbar degenerative diseases.

2. Introduction of LBP and treatments

Low back pain (LBP) is the number one cause of disability in adults [1]. Seventy-five percent (75 %) of all adults will experience LBP, secondary to degenerative lumbar diseases (including lumbar spondylolisthesis, stenosis, disc herniation or disc diseases) [2]. The annual total cost is estimated to exceed $100 billion for treatment of LBP related lumbar diseases in the United States alone [3,4].

Patients with LBP are usually treated conservatively at early stage of the disease. When conservative treatment fails, an appropriate lumbar decompression procedure, such as laminectomy, discectomy or foraminotomy, is performed [5]. A decompression procedure always involves removing part of the bone or soft tissue that compresses the spinal nerve root with a small incision and minimal disruption to the surrounding tissues. Decompression-alone is generally effective for relieving radicular pain caused by nerve compression. Pain relief and functional scores (e.g., Oswestry Disability Index, ODI) typically improve significantly in the short term but may decline over time if underlying instability or degeneration progresses [6]. Improvements in quality-of-life measures (e.g., SF-36) are significant but can decline if further degenerative changes occur. There were more than 350,000 lumbar decompressions performed in the United States in 2014 [7]. Decompression may cause changes in the structure of lumbar segments and lead to reoperation mainly due to same segment diseases (SSD, including disc herniation, recurrent stenosis, instability, and others) [[8], [9], [10]].

To improve decompression-alone surgery, fusion of the index level in addition to a decompression was developed where the index level is fused using bone grafts with a fusion device to stabilize the index segment [11] and restore normal disc height [12]. Decompression-with-fusion is generally effective for both radicular and axial back pain relief. It stabilizes the spine, which is thought to provide more consistent long-term pain relief, better and more sustained functional improvement, and thus lead to better overall functional outcomes and great improvements in quality-of-life scores [11]. There were over 370,000 lumbar fusion performed in 2014 in the United States [7]. The number of lumbar fusion surgeries has soared in the past decade [13]. Currently, 90 % of patients with LBP are treated using decompression-with-fusion surgeries in the United States, and 50 % in other countries [14].

3. Comparison of the two surgeries

Numerous studies have compared the clinical advantages of the two surgeries and reported inconsistent clinical outcome data [4,[15], [16], [17]]. Weinstein et al. compared outcomes for decompression-alone versus decompression-with-fusion in a randomized controlled trial and found better long-term pain relief and functional improvement in the fusion group, particularly in patients with instability [18]. Fritzell et al. found that fusion provided better long-term outcomes in terms of pain relief and function in a randomized controlled trial comparing decompression-alone to decompression-with-fusion surgeries [19]. Ghogawala et al. compared laminectomy alone versus laminectomy-with-fusion and reported that patients undergoing fusion had slightly better outcomes in terms of quality of life and lower reoperation rates over a four-year period in a randomized controlled trial [10]. Forsth et al. found that among patients with lumbar spinal stenosis, with or without degenerative spondylolisthesis, decompression-with-fusion surgery did not result in better clinical outcomes at 2 years and 5 years than did decompression-alone surgery in another randomized controlled trial [9]. More recently, Austevoll et al. found that decompression-alone was noninferior to decompression-with-fusion over a period of 2 years in a randomized controlled trial [20]. Karlsson et al. found that adding fusion to decompression in spinal stenosis surgery, with or without spondylolisthesis, does not improve the five-year Oswestry Disability Index, and the data at 5 years-follow up support decompression-alone as the preferred method for operating on spinal stenosis in a multicenter randomized controlled trial [17].

Decompression-alone has been reported to lead to higher reoperation rates compared to fusion in short term [20]. In an extensive literature review, Lang et al. [4] compared the reoperation rates of decompression-alone or decompression-with-fusion and found that the reoperation rates of both surgeries are highly affected by the length of follow up time and for post-operative time up to 10 years, both surgeries are comparable in reoperation rates. For example, the reoperation rate following decompression-alone surgery ranges from 1.6% to 10.8 % within 1 year, 6.5%–41.3 % within 3 years, 3.6%–34.0 % within 5 years, 4.4%–33.8 % within 10 years after the primary surgery; the reoperation rate following decompression-with-fusion surgery ranges from 0.0% to 7.0 % within 1 year, 7.4%–19.6 % within 3 years, 7.8%–24.0 % within 5 years, 3.0%–29.3 % within 10 years after the primary surgery [4,17].

In general, these literature data showed not only comparable clinical outcome scores, but also similar reoperation rates in longer term of post-operative time. It leads to the conclusion in literature that overall clinical outcomes are comparable of the two surgeries and could not suggest one surgery over the other [4,9,10,17,20], implying that despite numerous technological advancements, surgical treatment of degenerative lumbar diseases has not been improved from decompression-alone surgery.

Reoperation after primary surgery could heavily burden health care resources. Lang et al. analyzed the costs related to reoperations following primary decompression-alone or decompression-with-fusion surgeries [4]. An analysis of an institutional database from 1997 to 2007 found that total direct cost of revision discectomy was $39,836 with a 1-year follow-up [21]. Another study showed that the mean total 2-year costs of revision fusion for pseudoarthosis, same-level recurrent lumbar stenosis and adjacent segment disease were $41,631, $49,431 and $47,846 respectively [22]. Recently, the two-year follow up reoperation cost of decompression-with-fusion was estimated at $53,828 [23]. In addition, while both decompression-alone and decompression-with-fusion surgeries have been shown to provide significant benefits to patients with lumbar degenerative diseases (showing comparable clinical outcomes [9,10] in terms of pain relief, functional improvement, and quality of life), however, fusion is associated with a higher initial cost, more bleeding, longer operating times and a longer recovery period [4,17]. Therefore, contemporary fusion technique might not be optimal to enhance treatment of patients from decompression-alone surgery. Development of new surgical techniques to reduce reoperation rate in patients after lumbar surgery is critically important and needed for reducing the healthcare expenditure.

4. Analysis of reoperation data and research perspectives

Numerous studies have investigated the risk factors of reoperation following decompression-alone or decompression-with-fusion surgeries. Risk factors of both surgeries are reported to be related to patient age, gender, symptoms, coexisting degeneration, type of operation [[24], [25], [26], [27]], and altered biomechanical forces near the index disc or a fusion site [28,29]. However, due to different experimental setup and patient population, inconsistent results have been reported on these risk factors. An in-depth analysis of the literature data revealed that although clinical outcomes including reoperation rates are comparable following the two types of surgeries, different underlying reoperation mechanisms may exist. For decompression-alone surgery, clinical outcome data showed that reoperations are often due to recurrent disc herniation, progressive degeneration, or instability, i.e., same segment diseases (SSD). For decompression-with-fusion, clinical data showed that reoperation is often due to complications like adjacent segment disease (ASDis) or pseudoarthrosis. For example, Ghogawala et al. reported that reoperations among spondylolisthesis patients treated with decompression-alone surgery were all at the index levels because of SSD; and among patients treated with decompression-with-fusion were all at the adjacent levels after fusion surgery due to symptomatic ASDis [10]. Forsth et al. found in another prospective study for lumbar spinal stenosis that within a mean follow up period of 6.5 years, 31 patients received reoperations after lumbar fusion with 22 due to ASDis and 3 due to pseudoarthrosis; 28 patients received reoperations after decompression-alone surgery with 18 due to restenosis at the index levels and 5 due to ASDis [9]. Karlsson et al. reported that a total of 26 patients (22 %) in the decompression-alone group underwent subsequent surgery with restenosis or foraminal stenosis at the index level being the most common cause (n = 19; 73 %); a total of 27 patients (24 %) in the fusion group underwent further lumbar surgery with adjacent level stenosis being the most common cause (n = 23; 85 %) in a prospective study for lumbar spinal stenosis of a mean follow up period of 5 years [17].

These analyses could provide important insight into the investigation of mechanisms causing reoperation in patients with LBP after lumbar surgery. The literature data indicate that the etiology of reoperation could be different between decompression-alone and decompression-with-fusion surgeries. In general, the clinical data reveal that a contemporary fusion indeed is efficient to stabilize the index level and helps reduce SSD that are mostly associated to decompression-alone surgeries. However, fusion causes complications in other surrounding spinal structures such as ASDis. Physiologically, spinal disc degeneration develops for decades. Surrounding tissue structures including spinal ligaments and adjacent discs have all adapted to the degenerative conditions of the index discs. For example, the inter-segmental ligaments and muscles could have been shortened in length to adapt to the disc height changes due to index disc degeneration (Fig. 1A). A contemporary lumbar fusion is mainly aimed to restore normal disc height and intervertebral alignment [12], and thus could cause biomechanics changes of the surrounding spinal structures such as internal compressive pressures on endplates, overstretching the intersegmental ligaments and consequently, increasing pressures on adjacent discs [30,31] (Fig. 1B). Therefore, a release of the tightened ligaments may be beneficial to minimize the changes of stresses in the surrounding spinal structures such as at the adjacent discs and facet joints and reduce the subsiding forces on the endplate–cage interface (Fig. 1C).

Fig. 1.

Schematic figures showing A) spinal segments with a diseased disc (ALL-anterior longitudinal ligament; PLL-posterior longitudinal ligament); and B) treatment of the diseased disc with fusion surgery by restoration of normal disc height. Restoration of normal disc height causes stretching of anterior/posterior longitudinal ligaments (showing by read arrows) and increases pressures on endplate–disc interfaces (showing by green arrows) of both index and adjacent segments. C) The idea of soft tissue release to reduce the tightness caused by expanding the index space using the fusion surgery and reduce internal pressures.

There are few studies that have attempted to investigate the biomechanics changes of the disc height and alignment, and contractions of surrounding spinal ligaments and muscles after fusion surgery [32,33]. For example, Zhou et al. investigated the biomechanical factors that may be associated to ASDis development using a combined in-vivo and in-silico approach [30]. Recent biomechanics research has also reported that a restoration of the index disc heights after fusion is associated with decreases of the adjacent disc heights (thus increasing disc pressure) [26,30,34]. Therefore, to clarify the biomechanical mechanisms of ASDis, prospective, longitudinal patient follow up studies are necessary to investigate the associations of disc height changes of both the index and adjacent segments with the development of ASDis following a fusion surgery. Quantitative analysis of adaptations of spinal ligaments and muscles to disc degenerations is critical to the understanding of the biomechanical etiology of the disc degeneration development. It is also clinically important to investigate novel surgical management strategies of spinal ligaments and muscles that can optimize the biomechanical environment of adjacent segments after a fusion surgery. These investigations should provide solid rationales for improvement of contemporary lumbar fusion surgeries and development of new technologies that aim to minimizing post-operative reoperations and enhancing longevity of the surgeries.

5. Perspectives

In conclusion, based on the analyses of data published in literature, the objective of contemporary spinal surgeries for treatment of LBP may need a revisit. Decompression-alone caused reoperations mostly because of SSD, but a decompression minimally interferes with the surrounding tissue structures such as spinal ligaments and adjacent discs. Any improvement of surgical treatment of the index discs that is aimed to avoid SSD should also minimize the interference to surrounding spinal tissues to avoid negative effects on these spinal structures. Contemporary fusion, while being efficient in stabilizing the index levels and reducing complications at the index level, can cause biomechanics changes in the adjacent levels and is associated with reoperations mostly at the adjacent levels. Therefore, while fusion is an efficient procedure to help reduce SSD related reoperation after decompression-alone surgery, any future improvement of fusion of the index levels should focus on minimizing interference to the biomechanical environment of surrounding tissue structures such as adjacent discs, intersegmental ligaments, and muscles. Furthermore, future studies should investigate the intrinsic biomechanical interactions among passive and active spinal tissues in health subjects and spinal patients before and after surgical treatments using in-vivo, in-vitro and in-silico approaches. The novel spinal biomechanics data should be instrumental for development of new treatment techniques that aim to relieve LBP pain and reduce the reoperation rate at both the index (mostly associated with decompression-alone) and adjacent (mostly associated with decompression-with-fusion) levels.

CRediT authorship contribution statement

Guoan Li: Conceptualization, Methodology, Data Analysis and Writing- Original draft preparation. Won Man Park: Investigation, Formal analysis, Writing – review & editing. Thomas Cha: Investigation, Formal analysis, Writing – review & editing.

Informed consent

NA.

Ethical approval

NA.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

The authors declare that there is no conflict of interest.