IMPACT OF THE GRADE OF DEGENERATIVE LUMBAR DISEASE ON THE OCCURRENCE OF SPINAL DEFORMITY

ABSTRACT Objective: To evaluate the impact of the severity of degenerative lumbar disease (DLD) on the occurrence of spinal deformity, as well as on the choice of treatment, whether conservative or surgical. Methods: This is a retrospective analysis of a prospective database. One hundred and thirty patients with low back pain and/or pain radiating to the lower limbs were included in the study and were graded on a DLD scale that considers total spine (panoramic) X-ray findings. The rates of adult spinal deformity (ASD) for the different degrees of the DLD scale were compared using the Chi-square test. The choice of treatment type, conservative or surgical, was also compared among the degrees of the DLD scale using Fisher's exact test. Results: The ASD rate was zero in grade 0 patients, 24% in grade I, 35% in grade II and 44% in grade III (P = 0.02). Grade III patients were more likely to be diagnosed with ASD (OR = 2.22; P <0.05; 95% CI = 0.90-5.45) compared to the other DLD grades. Only 7.7% of the patients were chosen for surgical treatment and there was no difference by the DLD scale grade. Conclusion: There was correlation between the DLD grading scale and the occurrence of ASD, with at least twice the chance of this diagnosis in DLD scale grade III as compared to the other grades. The treatment of choice was conservative in a very small number of patients analyzed, with no difference between the different grades of the DLD grading scale. Level of Evidence III; Retrospective analysis of prospective database (cohort).


INTRODUCTION
The use of total spine radiography in the evaluation of patients with chronic low back pain has become increasingly popular because this modality allows the observation of both radiographic changes in the lumbar segment of the spine and spinal alignment in the coronal and sagittal planes, as well as the measurement of spinopelvic parameters. 1 The association between changes in spinopelvic parameters and symptomology, including pain and functional disability, is well established as demonstrated in several studies. [2][3][4] This correlation was the basis for the development of the SRS-Schwab classification system for adult spinal deformity (ASD). 5 However, low back pain and consequent functional disability may have several other causes including spondylosis or spondyloarthrosis (disc, facet joint, and vertebral body degeneration), degenerative spinal deformities, vertebral instability (including spondylolisthesis), and central or foraminal canal stenosis with spinal cord or nerve root compression. 6 Although magnetic resonance continues to be considered the gold standard imaging examination for the evaluation of degenerative changes in the spine, 7 the radiographic examination allows the identification of findings associated with spondylosis, including osteophytosis, loss of disc height, sclerosis, and subchondral cysts in the vertebral plateaus. 8 Recently, a severity scale for degenerative lumbar disease (DLD) that considers a total spine radiographic examination and assesses the presence of radiographic signs of spondylosis, its extension throughout the lumbar segments, and the presence of signs of instability, such as spondylolisthesis or laterolisthesis, was presented. 1 The objectives of the present study were to evaluate the impact of the severity of DLD on the occurrence of spinal deformity and on the choice of treatment, whether conservative or surgical.

Type of study and ethical aspects
This is a cross-sectional study considering a cohort of prospectively selected patients in outpatient care at a clinic specializing in spinal surgery. The study was approved by the Institutional Review Board of the service where it was conducted (CAAE: 18013219.7.0000.5463) and considered a bank of radiographic images of patients who signed the informed consent form regarding the storage of their examinations. Information from the medical records was also considered, including demographic data and choice of treatment, whether conservative or surgical.

Study population
Adult individuals (≥ 18 years of age) complaining of chronic low back pain (starting at least 3 months before), with or without associated symptoms of radiculopathy were included. The exclusion criteria were previous neurological or spinal surgery, neurological or neuromuscular diseases, history of spinal trauma or neoplastic spinal disease, complaints of hip/knee/ankle/foot disability that can alter joint positioning, inadequate radiography not permitting visualization from C2 to the head of the femur or without sufficient resolution to analyze the radiographic signs of DLD.

Grading of degenerative lumbar disease
Total spine radiographs (panoramic) in frontal and lateral views, considering the lumbar segment, were used to conduct the analysis. All the examinations were performed at the same radiology service following a standardized technique: comfortable standing posture with shoulders at 45° elevation and elbows flexed, resting the fingertips on the clavicles or on the face. 9 As all the images were digitalized in DICOM format, it was possible to enlarge them while maintaining the quality and resolution necessary for accurate assessment level by level of the entire lumbar segment. According to the radiographic findings of DLD, the patients were graded as follows. (Figure 1) • Grade 0: absence of signs of degenerative disease in the lumbar spine. • Grade I: presence of signs of degenerative disease in one or two lumbar spinal segments, without scoliosis or signs of instability. • Grade II: presence of signs of degenerative disease in three or more segments of the lumbar spine, without signs of scoliosis or instability. • Grade III: presence of signs of degenerative disease in the lumbar spine associated with scoliosis (coronal inclination measured using the Cobb technique greater than or equal to 30°) and/or signs of instability, such as laterolisthesis (> 2 mm) and spondylolisthesis (at least grade 2).

Diagnosis of adult spinal deformity (ASD)
The same total spine radiographs used to grade DLD were used to diagnose ASD. For this, the presence of coronal plane deformity (scoliosis) and loss of spinopelvic sagittal alignment were evaluated. The radiographic parameters were measured using Surgimap Spine software (Nemaris Inc. New York, USA), a tool validated for radiographic evaluation of the spine. 10 The parameters described by the International Spine Study Group were considered as the criteria for the ASD diagnosis: presence of scoliosis (coronal Cobb angle ≥ 20º), thoracic kyphosis (T4-T12 ≥ 60°, pelvic version (PV) ≥ 20º, sagittal vertical axis (SVA) > 5 cm, and the discrepancy between pelvic incidence and lumbar lordosis (PI-LL) > 10°. 5 The presence of at least one of these criteria defined an ASD diagnosis.

Statistical analysis
Statistical analysis was conducted using the R program, version 3.4.9 (R Foundation for Statistical Computing, Vienna, Austria). The comparison of the occurrence of ASD among the different grades of the DLD severity scale was analyzed using the Chi-squared test and the odds ratio (OR) was also calculated for each DLD grade, with a confidence interval of 95% (95% CI). The type of treatment choice, between conservative and surgical, was compared among the DLD severity scale grades using Fisher's exact test. The level of significance considered for all statistical analysis was 5%.

Correlation between DLD severity and ASD occurrence
The more advanced the DLD grade, the greater the rate of ASD occurrence among the patients. No grade 0 patients were diagnosed with ASD, while the diagnosis occurred in 24% of grade I patients, 35% of grade II patients, and 44% of grade III patients ( Figure 2, Table 1), with a statistically significant difference (P = 0.02). Patients classified as grade III on the DLD grading scale had higher odds of having an ASD diagnosis (OR = 2.22, P < 0.05, 95% CI = 0.90-5.45) than the other DLD grades.

Correlation between DLD severity and choice of treatment
Of the total patient sample, 7.7% opted for surgical treatment. According to the DLD grading scale, the percentage of patients who opted for surgical treatment varied, corresponding to 9% of grade 0 patients, 2.5% of grade I patients, 7.5% of grade II patients, and 17% of grade III patients ( Figure 3, Table 2), but without any statistically significant difference (P = 0.239).

DISCUSSION
Recently, a DLD grading scale based on the analysis of radiographic images of the total spine (panoramic) was presented. 1 This scale demonstrated high reproducibility and proved to be easily applicable. 1 The present study sought to evaluate whether such a DLD grading scale might influence certain clinical aspects of the patients, including the diagnosis of ASD and the type of treatment option, whether conservative or surgical.
ASD consists of a wide variety of clinical presentations (neglected idiopathic scoliosis, degenerative lumbar scoliosis, loss of sagittal alignment, etc.) and, therefore, its real prevalence is difficult to assess precisely, although it is believed that it is trending to increase along with the aging of the global population. 4,5 While Schwab et al. reported that up to 60% of the individuals above 60 years of age present ASD, using the presence of coronal curves with an angle of magnitude > 10° as a diagnostic criterion, 11 a recent Brazilian study found an occurrence rate of 18% of the population diagnosed with ASD and also demonstrated a relationship with increasing age, with 29% of the individuals aged ≥ 60 years. 12 In the present study, which considered only patients of a spinal service with complaints of low back pain and/or lumbosciatalgia, the ASD occurrence rate was 30% for the total sample. The radiographic parameters consider for an ASD diagnosis were those recommended by the International Spine Study Group 5 studies, which were also adopted by the study published by Barreto et al. 12 What was new was that the present study demonstrated that, according to the scale proposed by Vasconcelos et al., 1 the more frequent the ASD diagnosis the more advanced the DLD grade. 1 Moreover, the simple fact that the patients had a more advanced grade of DLD (grade III), made their chances of being diagnosed with ASD 2 times greater than patients with the other grades of DLD.
Although a good number of the patients diagnosed with ASD have minor complaints, or are asymptomatic, a portion of these patients present varying pain and functional disability profiles and require more aggressive treatment, including surgery. 13,14 Other studies have shown that patients diagnosed with ASD associated with loss of sagittal alignment have worse quality of life indicators and even greater predominance in the choice of surgical treatment. [2][3][4]15 Although the DLD grading system used in the present study has been shown to be correlated with the ASD diagnosis, there was no correlation between the different DLD grades and the determination of the type of patient treatment, between conservative or surgical.
Considering DLD alone, low back pain symptoms accompanied or not by radiation to a lower limb have an extremely high prognosis for improvement with conservative treatment. 9,[16][17][18][19] Thus, in general, in most cases conservative treatment is chosen with surgery limited to a small group of patients. 16,19 Similar information was also observed in the present study, with only 7.7% of patients choosing surgical treatment. The fact that there was no difference in the rate of choice of surgical treatment according to the DLD scale grade suggests that there was no correlation between the radiographic findings and the choice of treatment. It is known that the main factor associated with the choice of surgical treatment is the intensity of symptoms associated with functional limitation, 17,20 as well as the persistence of the symptoms, 17,21 rather than the radiological pattern of the disease.
The main limitation of the study is its retrospective nature, which makes impossible a progressive evaluation of the patients' treatments according to the DLD scale grade, as well as according to a diagnosis or not of ASD. Another important limitation is the lack of analysis of the quality of life indicators and their correlation with the variables considered. However, the results found in the present study, in which there was a correlation between the DLD scale grade and the occurrence of ASD, motivates new preferably prospective studies to analyze the impact of these variables on quality of life indicators.