Treating Lumbar Scoliosis with Single-Level Minimally Invasive Transforaminal Lumbar Interbody Fusion

Abstract

Substantial evidence exists supporting lumbar fusion procedures in cases of spondylolysis, spondylolisthesis, and other cases of sagittal deformity. However, coronal deformity can also be a cause of low back and leg pain. One hundred seven patients underwent minimally invasive transforaminal lumbar interbody fusion (MITLIF). All patients had preoperative and postoperative radiographs exhibiting a clear coronal deformity that correlated with their symptomatology. Dynamic radiographs were analyzed using a three-point angle measurement tool through the EasyViz viewer program. Pre-op and post-op Cobb angles (CA) were recorded along with Health-related Quality of Life (HRQL) measures, Visual Analog Scale, Oswestry Disability Index, and SF-36. The average CA decreased from 9.47 pre-op to 7.54 post-op (p < 0.05). CA ranged from 0.7 to 43.2% pre-op, and 0.7 to 34.1% post-op. There was a statistically significant (p < 0.05) correlation between CA improvement and HRQL measure improvement. There has not been an appropriate level of focus on coronal deformity, its relationship to HRQL measures, and long-term prognosis. In our study, CA was reduced by 21% on average with just a single-level fusion, supporting the consideration of a focused single-level fusion versus a large multilevel fusion in cases of coronal deformity, especially in elderly patients.

1. Introduction

Spinal deformity is defined by malalignment in curvature of one or more levels of the vertebral column. Spinal deformities involve the combination of sagittal, coronal, and axial planes [1]. Major developments in spinal deformity correction techniques did not occur until 1940–1970 when poliomyelitis was an epidemic causing patients to suffer from excruciating pain due to abnormal spine curvature and associated cardiopulmonary compromise, ultimately leading to an untimely death [2]. The Harrington procedure was a novel technique at the time and involved placement of hooks on the bony architecture of posterior elements that were attached to stainless steel rods, this technique launched the idea of utilizing internal stabilization to correct spinal deformity, which prior to that time relied mainly on casting and external stabilization techniques [3]. The advent of polyaxial head pedicle screws advanced techniques for scoliotic spinal deformity treatment by allowing the placement of rods even when the pedicles are misaligned and utilization of these screws alone or in combination with proximal hook instrumentation was revealed to yield a significant improvement in primary and secondary curve correction in idiopathic thoracic scoliosis [4, 5]. Adult spinal deformity (ASD) most often occurs because of wear- and tear-associated degeneration that accumulates over time, which is why it is so prevalent in the elderly population. Studies have documented the importance of sagittal deformity correction and significant improvement in health-related quality of life (HRQOL) measures [6, 7]. Sagittal imbalance can lead to progressive deformity, strain on paraspinal musculature, ligamentous and joint hypertrophy, spinal stenosis, spondylolisthesis, and even problems with social interactions due to the inability of horizontal gaze maintenance [8, 9]. These resultant conditions often have a disastrous impact on the patient’s ability to ambulate and carry out activities of daily living (ADL). Scoliosis, which is typically defined by an abnormality of spinal curvature in the coronal plane, commonly occurs due to aging-related collapse of intervertebral disks and vertebral body compression fractures that result in exaggeration or deficiency of normal curvatures of the spine [10]. Unfortunately, an insufficient amount of data is available regarding the outcomes of coronal deformity correction with minimally invasive spinal procedures. Therefore, we undertook the challenge to provide long-term data on radiographic and clinical outcomes of corrective surgery performed on individuals suffering from coronal deformity-associated pathology.

2. Materials and methods

The study was designed to follow a consecutive series of patients over an extended period to examine radiographic and clinical measures of surgical success. Three hundred fifty patients who underwent minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) were followed for seven consecutive years. All of the procedural outcomes and test results analyzed were previously collected as part of the course of routine treatment, no additional interventions were required, and data analysis did not involve use of subject identifiers, thereby waiving the need for informed consent. The data was pared down to 107 patients who had preoperative and postoperative radiographs that exhibited a clear coronal deformity that correlated with the patient’s symptomatology. A detailed description of our MI-TLIF approach can be found in our previous investigation entitled “Complication management with minimally invasive spine procedures” [11]. Dynamic radiographs were analyzed using a three-point angle measurement tool through the EasyViz viewer program. Cobb angles were recorded preoperatively and postoperatively along with a validated full set of Health-related Quality of Life (HRQOL) measures, such as Short Form-36 (SF-36), as well as the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI).

3. Results

We examined 107 patients over 7 years to look at clinical and radiographic outcomes of MI-TLIF. A total of 66 females and 41 males were treated at our institution (average age 68.6, range 39–92). Levels fused included L1-L2 (n = 1, 1%), L2-L3 (n = 10, 9.3%), L3-L4 (n = 16, 15%), L4-L5 (n = 75, 70%), L5-S1 (n = 1, 1%), or multilevel fusion (n = 4, 3.7%). The average Cobb angle decreased from 21.6 ± 5.6 preoperatively to 15.63 ± 3.58 postoperatively (p < 0.05). The lumbar lordosis and pelvic incidence (PI-LL) mismatch was improved postoperatively (Figure 1). There were improvements in VAS (Figure 2), SF36 (Figure 3), and ODI (Figure 4). There was a statistically significant correlation between Cobb angle reduction and HRQOL measure improvement (p < 0.05). Patients also exhibited an age-related trend, with average Cobb angles increasing with the patient’s age. Cobb angles improved after MI-TLIF in 94% (n = 101) of patients and this improvement correlated with an improvement in symptom questionnaires. MI-TLIF resulted in a high rate of spinal fusion and a low rate of reoperation. Preoperative and intraoperative imaging of a patient who underwent an MI-TLIF procedure are demonstrated in Figures 5 and 6. Cobb angles were reduced by 21% on average with just a single-level fusion, supporting the consideration of a focused single-level fusion versus a large multilevel fusion in cases of coronal deformity, especially in the elderly.

Figure 1.

Lumbar lordosis—pelvic incidence mismatch improved to <10 at 3 months postoperative period.

Figure 2.

Down trending of the VAS score from preoperative to 1 year postop.

Figure 3.

Down trending of the SF36 PCS and MCS score from preoperative to 1 year postop.

Figure 4.

Down trending of the ODI from preoperative to 1 year postop.

Figure 5.

Preoperative imaging of 72 year old female with symptomatic low back pain and neurogenic claudication. Neutral standing lateral (A) AP (B) plain radiographs and (C) MRI of the lumbosacral spine demonstrating coronal deformity of the lumbar spine.

Figure 6.

MRI revealed most severe lumbar stenosis at L4–5, consistent with patient’s distribution of radiculopathy. She then underwent focal treatment of the lumbar scoliosis with MIS TLIF L4–5. She experienced symptomatic relief and 2 year postop XR shows fusion at L4–5.

4. Discussion

Adult degenerative scoliosis (ADS) is recognized as the most common type of spinal deformity in skeletally mature individuals, which develops as a result of progressive and asymmetric degeneration of the vertebral column [12]. Back pain is highly prevalent in adult scoliosis, it occurs most frequently on the convex aspect of the coronal deformity that is thought to be due to degenerative changes in intervertebral discs and facet joints, as well as para-spinal muscular exertion associated with spinal imbalance [10]. Debilitating radiculopathy has also been noted to occur in up to 78% of individuals suffering from ADS, which typically occurs on the concave side of the spinal deformity as a result of foraminal stenosis due to facet joint hypertrophy and lateral subluxation [13, 14]. Measurement of the Cobb angle is currently the gold standard for quantification of spinal curvature and is widely considered to be a reproducible technique for establishing the initial diagnosis of adult scoliosis, as well as a postoperative measurement of surgical success. The Cobb angle derives its name from John Robert Cobb, an American orthopedic surgeon, who pioneered the use of this measurement modality and described its use in his “Outline for the Study of Scoliosis” which was published as part of Instructional Course Lectures of the American Academy of Orthopedic Surgeons in 1948 [15]. In order to diagnose a skeletally mature individual with scoliosis, the Cobb angle, which is the resultant angle of intersecting perpendicular lines drawn parallel to the superior vertebral endplate of the most tilted vertebra at the top of the curve and the inferior endplate of the most titled vertebral body at the bottom of the curve, must be observed to be or exceed 10 degrees on a posteroanterior standing radiograph of the spine (Figure 7) [16]. Although it is important to radiographically assess the patient’s spinal curvature prior to and after surgical intervention, it is equally important to assess other aspects that encompass the patient’s well-being in order to obtain an accurate measure of surgical success.

Figure 7.

Cobb angle. The resultant angle of intersecting perpendicular lines drawn parallel to the superior vertebral endplate of the most tilted vertebra at the top of the curve and the inferior endplate of the most titled vertebral body at the bottom of the curve, must be observed to be or exceed 10 degrees on a posteroanterior standing radiograph of the spine.

Several outcomes are measured in order to assess the effect that scoliosis has on a patient’s overall quality of life, as well as the clinical success of scoliosis repair surgery. Health-related Quality of Life (HRQOL) measures, such as Short Form-36 (SF-36), Visual Analog Scale (VAS), and Oswestry Disability Index (ODI) are the most frequently used measurement modalities. HRQOL explores physical, mental, emotional, and even social parameters of a patient’s subjective well-being. SF-36 is the most commonly used HRQOL that is composed of eight scale scores which include but are not limited to, physical functioning, bodily pain, general mental health, and social functioning, which yield physical component summary (PCS) and mental component summary (MCS) scores [17]. The VAS is frequently utilized to further assess a patient’s degree and intensity of pain on a continuous scale that ranges from a score of 0 (“no pain”) to 100 (“worst imaginable pain”) [18]. The ODI is an equally important tool utilized in assessment of patients’ ability to perform activities of daily living (ADL), lifting heavy objects, as well as other aspects of their lives that may be affected by spinal disorders. Furthermore, ODI can isolate the variable of physical impairment from its psychosocial consequences [19]. Once a patient is radiographically diagnosed with scoliosis, their symptoms severely affect their quality of life and are refractory to nonoperative methods of treatment, it may be time to consider surgical intervention. Decompression and instrumented fusion is frequently indicated in order to relieve neurogenic claudication and halt the devastating sequelae of curve progression, destabilization, and degeneration of vertebral bone architecture caused by adult degenerative scoliosis. Ever since the 1930s, when it was first reported in literature by Capener as a treatment for spondylolisthesis, lumbar spine fusion has been performed via anterior retroperitoneal approach, as it provides direct access to vertebral bodies and is associated with fusion rates of approximately 92% [20, 21]. However, anterior lumbar interbody fusion (ALIF) is not without complications as it carries an inherent risk of injury to various abdominal and retroperitoneal structures that include, but are not limited to, great vessels, abdominal organs, prevertebral ganglia, and plexus [22]. Although open spine surgery has been traditionally employed to gain access to lumbar spine and treat its associated deformities, minimally invasive approaches are now becoming commonplace due to their ability to significantly reduce surgical trauma, preserve paraspinal muscle, decrease intraoperative blood loss, and hospital stay [23]. Specifically, when comparing transforaminal lumbar interbody fusion (TLIF) to minimally invasive transforaminal lumbar interbody fusion (MI-TLIF), it is becoming more evident that the latter is superior in every aspect. Multiple investigations have established that MI-TLIF yields significantly better SF-36, VAS, and ODI scores, improved perioperative outcomes and long-term outcomes that are comparable to TLIF, as evidenced by multiple studies, including a four-year prospective investigation which revealed an overall bony fusion rate of 93.5% for MI-TLIF [24, 25, 26]. As supported by the aforementioned studies, it is clear that the minimally invasive approach is superior to that of the traditional open lumbar spine surgery, especially when considering the elderly patient population whose surgical outcomes are further complicated by comorbidities. Based on our results and the fact that minimally invasive spine surgery is associated with reduced intraoperative blood loss, it is indubitable that when compared to single-level, multilevel lumbar fusion results in a higher incidence of complications, especially in the elderly population [27].

4.1 Limitations

This study lacks a comparative arm in which patients underwent multilevel lumbar fusion for not only the fractional curve but also the major curve for similar presentations of predominant radiculopathy. We do not have such a comparison group due to the lack of aggressive surgeries for this particular patient population in our institution. Despite of that, this single-arm study is adequate to show the safety and long-term durability of single-level TLIF for patients with predominant radiculopathy from fractional curve.

5. Conclusions

There exists substantial evidence to support lumbar fusion procedures in cases of spondylolysis, spondylolisthesis, and other cases of sagittal deformity. However, coronal scoliotic deformity can also be a cause of low back and leg pain in a certain subset of patients. Single-level minimally invasive transforaminal lumbar interbody fusion yields significant reductions in coronal deformity, improvement in health-related quality of life measures, a high rate of spinal fusion, and a low rate of reoperation. This minimally invasive approach to the lumbar spine is especially important when considering single versus multilevel fusion for the treatment of adult degenerative scoliosis in the elderly patient population whose surgical outcomes are already at high risk due to comorbidities.

Author contributions

Conceptualization, N.H. and M.P.C.; methodology, N.H. and M.P.C.; formal analysis, N.H. and M.P.C.; investigation, N.H. and M.P.C.; resources, N.H. and M.P.C.; writing—original draft preparation, V.C., V.G. and T.M.E.; writing—review and editing, V.C., V.G., T.M.E., N.H. and M.P.C.; supervision, N.H. and M.P.C.; project administration, N.H. and M.P.C.

Funding

This research received no external funding.

Conflicts of interest

Mick Perez-Cruet MD, MS: Thompson MIS-ownership interest.