Article Information

Marcelo Molina^1,2,3,*, Sebastián Vial^1,4

¹Orthopaedic Surgery Department, Spine Unit, Instituto Traumatológico, Dr. Teodoro Gebauer, Santiago, Chile

²Orthopaedic Surgery Department, Spine Unit, Clínica Alemana, Santiago, Chile

³Universidad Finis Terrae, School of Medicine, Chile

⁴Universidad de Chile, School of Medicine

*Corresponding Author: Marcelo Molina, Orthopaedic Surgery Department, Spine Unit, Instituto Traumatológico, Santiago, Chile.

Received: 06 December 2023; Accepted: 11 December 2023; Published: 29 December 2023

Citation: Marcelo Molina , Sebastián Vial. Radiological Classification for Degenerative Lumbar Spine Disease: A Literature Review of the Main Systems. Journal of Spine Research and Surgery. 5 (2023): 127-138

Abstract

Keywords

spine; degenerative; lumbar; classification; disc herniation; spondylolisthesis; facet joint osteoarthritis; spinal; stenosis; literature; review

Article Details

Introduction

Degenerative changes in the lumbar spine, considered a natural part of aging, typically commence early, often between the 2^nd and 3^rd decade of life [1]. These changes encompass all the components of the vertebral unit, including the intervertebral disc, the facet joints, their respective ligaments, and the adjacent vertebrae.

The distinction between normal and pathological degeneration is not always clearly defined. There is a gradual degenerative process of the spine that in some individuals progresses to pathological changes that can lead to symptoms. Numerous classification systems aim to quantify the degree of spine degeneration, delineating the threshold between normal and pathological changes. The severity of radiological degeneration is expected to correlate with clinical symptoms and functional status [2]. An ideal classification should allow to definition of the degree of severity of the pathology, provide a common language among health care professionals, establish a prognosis, and guide treatment [3]. Unfortunately, the relationship between pathological degeneration and symptoms does not always correlate closely. This paradox is evident in some patients presenting with severe radiological degeneration and mild symptoms, contrasting with others presenting without significant degeneration but with severe clinical impairment.

Despite the above limitations, imaging remains a primary tool in clinical practice for assessing spinal pathology, offering various classifications based on different imaging modalities described in the literature. We conducted a systematic review of available classifications for lumbar spinal degenerative disease, to identify those demonstrating the highest clinical utility, through a strong clinical correlation and reproducibility.

Material and Methods

We performed a systematic literature review search for papers that proposed or described a radiological classification system for degenerative lumbar spine disease, including lumbar disc herniation, facet joint arthritis, spondylolisthesis, and lumbar stenosis.

Information search:

The search was performed by 2 investigators, an experienced spinal surgeon, and an orthopedic resident. The literature search was carried out in three stages. The first one consisted in searching in MEDLINE and EMBASE databases using diverse combinations of the following MeSH terms: "classification", "diagnostic imaging", "computed tomography scan", "magnetic resonance imaging", "lumbar vertebrae", "Intervertebral disc", "intervertebral disc degeneration", "Intervertebral Disc Displacement", "spine osteoarthritis", "zygapophyseal joint", "spinal stenosis", "spondylolisthesis". The search was restricted to English, with articles published from 1980 to date. Next, we expanded the search by exploring the reference list of selected articles and utilizing the “related articles” function within the search engine. Lastly, only articles meeting our criteria were selected.

Inclusion criteria:

We included clinical papers describing classifications of lumbar degenerative diseases based on radiographic, CT, and/or MRI evaluation. Preference was given to those with reliability assessments.

Evaluation of the classification systems:

The reliability tests for the reviewed articles were primarily assessed using the “Intraclass Correlation Coefficients” (ICC) and “Cohen's Kappa coefficient” (k), following "Landis & Koch criteria [4,50] (refer to Table 1).

A good classification reliability is generally accepted with a Kappa index of > 0.60, with at least substantial agreement [2]. However, for facet joint degenerative pathology -which is considered more difficult to classify- Kappa coefficients or ICC >0.40 (at least moderate agreement) is considered acceptable for evaluation [2].

Table 1: Agreement Measures for categorical data according to the criteria published by "Landis & Koch [4,50].

Results

Initially, 1873 articles were identified in the databases. Articles were selected according to their title and abstract, subsequently, bibliographic references and related articles in search engines were reviewed. A total of 64 articles were reviewed, identifying 31 imaging-based classification systems for lumbar spine degenerative pathology that adjusted to our selection criteria.

Lumbar Disc Degeneration Classifications Systems:

In our literature search, we found seven imaging systems for lumbar disk degeneration, all with reliability evaluation. Five were based on MRI findings and two were based on plain radiographs (see Table 2). However, because MRI is the current gold standard, we only included MRI-based classifications.

Only two underwent both intra- and inter-rater reliability tests, showing a Kappa coefficient > 0.60. The classification proposed by Pfirrmann et al. [7] and its subsequent modification by Griffith et al.8 exhibit greater values in their reliability tests.

The Pfirrmann et al. MRI-based classification categorizes lumbar disc degeneration into 5 degrees based on signal intensity, disc structure, and differentiation between the nucleus and the disc ring [7]. Griffith et al.'s modification increases this to eight, enhancing discrimination, especially between disc degeneration in elderly subjects. In the original Pfirrmann classification, there were more than 87% of lumbar intervertebral discs graded as either III or IV in this age group, without substantial difference between them [8].

The “Tufts Classification for lumbar disc degeneration”, created by Riesenburger et al. classifies degenerative disc disease in 6 degrees (Grades 0 to 5) depending on the score obtained according to the variables of disc brightness and structure, Modic changes, high-intensity zones (HIZ) and disk height. In their reliability studies, moderate to excellent intra-rater agreement (k = 0.53 - 0.94) and substantial inter-rater agreement (k = 0.66 - 0.77) were demonstrated for all the variables except for HIZ, which showed moderate agreement [9]. Later, Burke et al. modified this classification system eliminating the HIZ variable. At the same time, he performed reliability tests involving evaluators from different specialties (2 neuroradiologists and 2 neurosurgeons), to assess inter-specialty reproducibility. The interrater agreement was moderate (k = 0.465 - 0.576) and the intrarater agreement was moderate to substantial (k = 0.523 - 0.649) [10].

HIZ = High intensity zone

Table 2: Summary of the Lumbar Disc Degeneration Classifications Systems included in our review

Lumbar Disk Herniation Classifications Systems:

Seven classification systems related to LDH were identified (refer to Table 3). Four articles [12], [13], [15], and [46] underwent reliability evaluation. The classification suggested by Ahn et al. [12] uses MRI to grade the sagittal migration of LDH from 1 to 6, depending on the direction and distance from the disc space, displaying substantial intra and inter-observer agreement (refer to Table 3). The Michigan State University (MSU) classification system, developed by Mysliwiec et al. [15] using weighted-T2 axial MRI images, categorizes the LDH in 3 levels (from anterior to posterior: 1, 2, and 3) and the medial-lateral location in 4 levels (A = central; AB = paracentral; B = lateral recess; C = far lateral). The Kappa coefficient has almost perfect values for both the interrater (weighted k: Grade = 0.934; Location = 0.904) and intrarater (Weighted Kappa: Grade = 0.883; Location = 0.808) agreement. Halldin et al. [13], through CT and MRI, present a graduation system for LDH distribution and size across multiple planes. They did not use the Kappa coefficient or ICC for the evaluation of intra and interobserver agreement, this makes reliability studies not comparable with other classifications. Zhu et al., in 2023, introduced an MRI-based LDH classification system outlining four types and recommending a surgical strategy for each one, demonstrating good inter- and intra-observer agreement [46].

PELD = Percutaneous endoscopic lumbar discectomy

* Intra and inter-observer weighted kappa coefficient values according to Zhu et al. [44]

Table 3: Summary of Lumbar Disc Herniation Classifications Systems included in our review

Lumbar Facet Joint Osteoarthritis Classifications:

Eight imaging systems of lumbar facet degeneration were found (refer to Table 4). Given the difficulty of evaluating degenerative pathology on facet joints, regardless of imaging modality, a Kappa coefficient or ICC> 0.40 is considered acceptable [2]. Only four classifications -Pathria et al. [18], Weishaupt et al. [19], Fujirawa et al. [20], and Little et al. [21] had reliability studies meeting these criteria. Pathria et al.'s classification using plain radiographs was excluded due to poor inter-observer agreement (k = 0.26) [18].

Pathria et al. in 1987 proposed a facet osteoarthritis severity classification system based on CT, categorizing it into 4 grades (from grade 0 to 3). They only evaluated the interrater agreement, which was k = 0.46 [18]. Fujirawa et al. building upon Pathria et al.'s work, introduced an MRI-based classification system with 4 severity degrees exhibiting substantial inter-rater agreement (k = 0.636). Stieber et al. performed new reliability studies for both classifications, showing different values compared to the original articles (refer to Table 4) [25]. This could be due to the difficulty in assessing the facet joint, independent of the imaging methodology.

Little et al.'s modification of Kellgren's classification 2015, uses radiographs to grade the severity of osteoarthritis by 5 degrees (from 0, no osteoarthritis, to 4, advanced osteoarthritis) with moderate to substantial inter-observer agreement (weighted average Kappa = 0.63 ) and moderate intra-observer agreement (weighted Kappa = 0.42 and 0.54) [21].

The Weishaupt et al. classification system has the best reliability studies among the identified systems. Ranging from grade 0 (normal facet joint space) to grade 3 (narrowing of the joint space and/or large osteophytes and/or severe hypertrophy of the joint process and/or severe subarticular erosion and/or subchondral cysts). Furthermore, it shows an adequate intra -and inter-observer agreement in both CT and MRI assessments (refer to Table 4) [19].

* Reliability studies by Stieber et al [25].

Table 4: Summary of the Lumbar Facet Joint Osteoarthritis Classifications Systems included in our review

Degenerative Lumbar Spinal Stenosis Classifications:

Eight classification systems were found (refer to Table 5), all based on MRI.

The system proposed by Lurie et al. grades the severity of lumbar spinal stenosis in three areas: central, lateral recess, and foramina, and also evaluates root impingement. They defined it as "mild stenosis" if the decrease in area is ≤1/3 of the normal area, "moderate" if the compromise is between 1/3 and 2/3 of the normal area, and "severe" if the compromise is >2/3 of the normal area. For central stenosis, this classification shows an almost perfect intra- and inter-rater agreement (k = 0.82) and substantial (Kappa: 0.73), respectively. However, for lateral recess stenosis, foraminal stenosis, and root impingement, they found only a moderate inter-rater agreement (refer to Table 4) [26].

Schizas et al. graded the severity of central and lateral recess stenosis by dural sac morphology on MRI, without using any specific measurement tools. The reliability evaluation was moderate for interobserver agreement (k = 0.44) and substantial for intraobserver agreement (k = 0.65) [27]. They graduated stenosis from A to D: Grade A corresponded to a mild stenosis or no stenosis and grade D was an “extreme stenosis”. Grade A was subclassified into four specific subtypes of the distribution of the lumbar roots in the dural sac. Furthermore, they identified an association between grades C and D with a greater probability of failure of conservative treatment [27].

Another classification of degenerative central lumbar spinal stenosis, based on dural morphology by MRI and exhibiting good inter-observer agreement is described by Lee Guen et al. This system comprises four grades; ranging from grade 0 (the absence of stenosis) to grade 3, implying a severe stenosis with all the lumbar roots seen as a lump in the MRI [28]. Park et al. conducted a reliability study on Lee Guen et al. 's classification, revealing substantial inter-observer agreement values (k= 0.78). Additionally, they established an association between grade 0 with the absence of neurological manifestations and grade 3 with the presence of neurological manifestations [29].

For lateral recess stenosis, Pfirrman et al [47] in 2004 developed a grading system that described a four-grade scale based on compromise of the traversing nerve root (no compromise, contact of nerve root, deviation of nerve root, and compression of the nerve root). In 2021, Miskin et al [48] simplified this classification into a three-grade scale (normal, contact of the nerve root without compression, and compression of the nerve root). For lateral recess stenosis, Pfirmann et al. [47] reported an inter-reader agreement of 0.62–0.67 among three readers including one spine surgeon and two radiologists. Nevertheless, the modified classification had a fair agreement (k =0.323).

For foraminal stenosis, Wildermuth et al [30] in 1998 and Lee et al [31] in 2010 proposed an MRI classification with substantial and almost perfect Kappa coefficient values, respectively, for intra and interobserver agreement (see Table 5). Both consisted of 4 degrees, from the absence of foraminal stenosis to complete obliteration. It should be noted that the classification of Lee et al. is more precise in the definition of degrees. In 2022, Özer et al [45] proposed a new MRI classification and a treatment algorithm. They divided the foraminal stenosis into two groups: “stable” and “unstable”. In stable stenosis, the disc and annulus are calcified and facet joints are hypertrophic and degenerated. In unstable stenosis, there is a degenerative and mobile intervertebral disc. Each group has 4 subgroups about cause and type of compression. Then, they proposed a treatment for each subgroup. The classification has nearly perfect interobserver and intraobserver Kappa coefficient values (see Table 5).

Table 5: Summary of the Degenerative Lumbar Spinal Stenosis Classifications Systems.

Degenerative Spondylolisthesis Classifications:

Classically, spondylolisthesis has been classified according to the system proposed by Meyerding [32]. However, this classification is not specific for degenerative spondylolisthesis. We found only 2 imaging classifications for degenerative spondylolisthesis were found (refer to Table 6).

The “Clinical and Radiographic Degenerative Spondylolisthesis” (CARDS) classification system by Kepler et al. used static and dynamic plain radiographs, classifying the pathology with almost perfect interrater agreement (k = 0.82). It consists of 4 “radiographic types” (from A to D) based on disc collapse, anterior translation, and the presence of segmental kyphosis. Added to the above is the clinical variable modifying lower limb pain (0 = absent, 1 = unilateral, and 2 = bilateral) [33].

Gille et al. and the French Society for Spine Surgery, proposed a classification system using anteroposterior and lateral total spine radiograph [34], with almost perfect intra and interobserver agreement, with Kappa coefficients 0.89 and 0.82, respectively [35]. It should be noted that this system derives from the “Spinal Deformities in Adults Classification” by Schwab et al [36], which has an almost perfect (k = 0.87) and a substantial (k = 0.75) intra and interrater agreement, respectively. They classify spondylolisthesis into 5 types according to the calculations of the following variables: segmental lordosis, lumbar lordosis, pelvic incidence, pelvic tilt, and the vertical sagittal axis.

** Reliability studies by Ghailane et al [35]

Table 6: Summary of the Degenerative Spondylolisthesis Classification Systems included in our review

Discussion

In our systematic literature review, we identified 31 imaging-based classification systems for lumbar spine degenerative disease. This abundance of classifications underscores the intricate nature of the spine's functional unit, comprising various elements, including intervertebral discs, vertebral endplates, facet joints, and ligaments.

The different classification systems use various terminologies to describe the varying degrees of severity of lumbar degeneration. The evaluated classifications can use Arabic numerals (e.g., 1, 2, 3, etc.), Roman numerals (e.g., I, II, III, IV, etc.), letters (e.g., A, B, C, etc.) and qualitative terms (e.g., "mild," "moderate," "severe"). This variety may lead to confusion when comparing different grades. It should be mentioned that all the classifications, in their initial grades, describe the absence of degenerative pathology or mild changes. As graduation levels increase, more advanced stages of the disease are described, demonstrating a logical and evolutionary progression.

Reliability studies, particularly inter-observer agreement, play an important role in evaluating a classification system as they enable reproducibility among various evaluators, thereby fortifying the system's credibility. Typically, reliability is assessed using statistical tools like the Kappa coefficient or ICC. Among the 27 systems identified, 20 underwent inter-rater agreement studies. It is crucial not only to consider the validation and reliability of classifications but also their implementation in clinical practice. Simplicity and precision in the description of the systems are essential.

We identified one article by Kettler et al. [2], which assesses classifications for degenerative spine diseases, focusing on cervical and lumbar disc and facet joint degeneration, with an emphasis on their reliability studies. Their conclusions suggest preferred classifications based on statistical measures such as kappa or ICC values. In our article, we reviewed only image-based classifications of lumbar degenerative spine disease and include disc and facet joint degeneration, LDH, degenerative stenosis, and degenerative spondylolisthesis. However, we reviewed the lack of sufficient studies correlating them with clinical outcomes for prognosis. The choice of classification ultimately relies on the surgeon's expertise and experience.

Lumbar Disc Degeneration Classifications Systems

The gold standard image modality to assess disc degeneration is MRI. The system proposed by Pfirrmann et al. in 2001, evaluates lumbar disc degeneration using MRI and a simple algorithm to discriminate between 5 degrees. Moreover, it has an almost perfect and substantial intra and interrater agreement, respectively. Subsequent evaluations of its reliability showed almost perfect values of the Kappa coefficient and ICC, with no differences between specialties (radiologists versus spine surgeons) [38].

None of the other classifications found had the simplicity and inter-rater agreement reproducibility of Pfirrmann et al.'s classification. The modification made by Griffith et al. [8], allowing for more precise grading of degenerative lumbar disease across 8 levels, its complexity might limit its practicality in clinical settings."

Lumbar Disk Herniation Classifications Systems

In 2001, Fardon and his colleagues published an article detailing a consensus reached by members of the "North American Spine Society", the "American Society of Spine Radiology" and the "American Society of Neuroradiology" regarding the nomenclature and classification of lumbar disc disease38. This classification allows the characterization of LDH based on its morphology and location. An updated version by the same author was published in 2014 [39], proposing diagnostic categories for normal and pathological variations of LDH.

The MSU classification system [15] classifies the location and grade of the LDH with an almost perfect inter and intrarrater agreement [44]. Furthermore, there exists an association between the “MSU-B” LDH with greater severity of facet osteoarthritis. It should be noted that this system only evaluates LDH in the axial plane, not in the sagittal plane. However, the MSU classification is easy to apply in clinical practice with a very good level of agreement.

Another simple and easy system to use is Zhu et al. 's classification, which defines 4 types of LDH morphology and suggests a surgical strategy for each. However, de inter- and intra-observer agreement was only “good” [46].

Lumbar Facet Joint Osteoarthritis Classifications Systems

Only four imaging-based classifications identified for facet osteoarthritis meet the recommended international literature standards for Kappa coefficient or ICC values (>0.40) [2]. These encompass classifications utilizing plain radiographs (Little et al. [21]), CT scans (Pathria et al. [18]), MRI (Fujirawa et al. [20]), and a combination of CT and MRI (Weishaupt et al. [19]). It is known that the best image to evaluate the vertebral unit is MRI, therefore we recommend classification systems that use this imaging modality to evaluate the facet joins. Both Fujirawa et al. and Weishaupt et al. employ MRI to evaluate facet osteoarthritis, demonstrating adequate interobserver agreement. However, Weishaupt et al. 's classification offers a more detailed description between degrees, enhancing the precision of grading.

The reliability studies conducted by Weishaupt et al. [19] and Berg et al. [40] recommend the use of CT and MRI for assessing facet joint osteoarthritis. Although evaluation of the bony component (facet osteophytes and hypertrophy) is better with CT, results from CT and MRI are not significantly different.

Degenerative Lumbar Spinal Stenosis Classifications Systems

The best imaging modality to evaluate spinal stenosis is MRI due to its superior ability to identify non-bony components. The eight classifications identified use MRI to determine the severity of lumbar stenosis.

Fardon et al.'s classification offers a precise method to determine the location of spinal stenosis. It divides the site of compression into different zones based on anatomical limits. In the axial plane, these zones are the "central area", "lateral recess or subarticular area", "foraminal area", and "extraforaminal area". In the sagittal plane, these zones are the "infra pedicular level”, "pedicular or disc level", and "supra pedicular level".

The severity of the stenosis, regardless of its location, could be properly assessed using the Lurie et al. classification. It classifies the severity according to the compromise of the area in question [26]. "Mild" is the compromise ≤1/3 of the normal area, "Moderate" is the compromise between 1/3 and 2/3 of the normal area, and "Severe" is the compromise >2/3 of the normal area. The interobserver agreement of the severity of the central and foraminal stenosis were substantial (k = 0.73) and moderate (k = 0.58), respectively. The interobserver agreement at the lateral recess stenosis had the worst agreement values, with an average kappa coefficient of 0.49 [26].

The severity of the stenosis, regardless of location, could be adequately assessed using the Lurie et al. classification. It classifies the severity based on the affected area as compared to the normal 26. "Mild" is the compromise ≤1/3 of the normal area, "moderate" is the compromise between 1/3 and 2/3 of the normal area, and "severe" is the compromise >2/3 of the normal area. The inter-observer agreement of the central and foraminal stenosis severity was substantial (k = 0.73) and moderate (k = 0.58), respectively. The inter-observer agreement at the lateral recess stenosis had the worst agreement values, with an average kappa coefficient of 0.49 [26].

Assessment of central and lateral recess stenosis severity is achieved through the dural sac morphology, employing classifications by Lee Guen et al. and Schizas et al. Lee Guen et al.'s classification comprising four grades (from grade 0 to grade 3), offers simplicity and exhibits superior intra- and interobserver agreement. Conversely, Schizas et al. introduced a more complex system with seven degrees. However, it has limitations; for instance, grade A combines patients without stenosis and those with mild stenosis. Moreover, grades C ('severe stenosis') and D ('extreme stenosis') have notably similar descriptions, differing primarily by the absence of posterior epidural fat. Another advantage of Lee Guen et al.'s classification lies in its correlation between severity degrees and the dural sac cross-sectional area. In 2013, Park et al. validated Lee Guen et al.'s classification and found an association between symptoms and the degree of stenosis [28].

For lateral recess stenosis, the four-grade classification system described by Pfirmann et al. [47] reported an inter-reader agreement of 0.62–0.67 among three readers including one spine surgeon and two radiologists. Kaliya-Perumal et al. [49], in 2018, did a revalidation of the grading system. They reported an inter-reader agreement of 0.521 among three orthopedic surgery residents. The modification proposed by Miskin et al. had an inter-observer agreement lower than these previously reported results (k=0.323) [48].

For us, the best classification for foraminal stenosis was proposed by Lee et al. [31]. Their MRI-based classification categorizes foraminal stenosis into four degrees based on morphology. In contrast, Wildermuth et al.'s classification30 offers less detailed descriptions for each degree compared to Lee et al.'s approach. Notably, Wildermuth's classification primarily focuses on changes in epidural fat, whereas Lee et al.'s system evaluates multiple factors, including epidural fat, stenosis type, and nerve compression presence [30,31]. Özer et al.'s classification [45] presents an intriguing approach, considering vertebral level stability and providing surgical guidance for each subgroup.

Degenerative Spondylolisthesis Classification Systems

We identified two imaging-based classification systems dedicated to degenerative spondylolisthesis. One, proposed by Gille et al. [34], derived from Schwab et al.'s “Adult Spinal Deformities Classification” [36]. The other, by Kepler et al. [33], known as the “CARDS classification”, incorporates both clinical and radiological variables. Radiological parameters encompass disc space height, sagittal alignment, and disc translation. While clinical parameters consider pain in the lower extremities - unilateral or bilateral. Both classifications had good reliability studies [33,35,41], as outlined in Table 5. However, our judgment suggests their limitation lies in the complexity of routine clinical application. Kong et al. compared both classifications in a retrospective study. They concluded that both systems have acceptable reliability, but the CARDS classification was easier to use and had better inter and intra-rater agreement values. Their findings highlighted that type D in the CARDS classification and type 5 in Gille et al.'s system correlated with worse preoperative pain and showed greater post-surgery improvement. Notably, Gille et al.'s classification provides more comprehensive information for therapeutic decisions [41].

Conversely, Meyerding et al.'s classification [32] gains favor for its ease of application and widespread use due to its simplicity, supported by substantial intra and interobserver agreement (k = 0.79 and 0.78, respectively) [42]. However, its primary limitation lies in the lack of consideration for morphological parameters such as segmental kyphosis or disc height, which bear significance in prognosis [43].

Based on the literature review, we recommend the following classifications due to their better intra and interobserver reproducibility and clinical application:

1. Lumbar Disc Degeneration Classifications Systems:Pfirrmann et al. ⁷
2. Lumbar Disk Herniation Classifications Systems:
3. Location: Fardon et al. ³⁹, MSU classification (Mysliwiec et al.)¹⁵
4. Morphology: Fardon et al. ³⁹
5. Degree: Lurie et al.²⁶, MSU classification (Mysliwiec et al.)¹⁵
6. Lumbar Facet Joint Osteoarthritis Classifications Systems:Weishaupt et al.¹⁹
7. Degenerative Lumbar Spinal Stenosis Classifications Systems:
8. Location:Fardon et al. ³⁹
9. Central–lateral recess stenosis:Lee Guen et al. ²⁸, Lurie et al. ²⁶
10. Lateral recess stenosis:Lurie et al. ²⁶
11. Foraminal stenosis:Lee et al.³¹
12. Degenerative Spondylolisthesis Classification Systems:CARDS et al.³³

Limitations

We could not recommend some classification systems due to lack of reliability. Other studies are not focused on clinical outcomes and do not aid in treatment decisions.

We did not find any classifications that correlate with prognosis. Hence, it is left to the surgeon and his experience with which classification to use.

We only searched articles in the English language, which may limit the evaluation of an eventual good classification in a different language.

Conclusions

There are many classification systems, with advantages and disadvantages. Some of them were more widely used because they were easily applied and reliable.

For a classification to hold clinical value, it should exhibit high reliability, typically indicated by a Kappa or ICC value exceeding 0.60. Additionally, it should offer clinical guidance to aid in therapeutic decisions and integrate them into guidelines.

Our review revealed that existing classifications only partially provided the above characteristics. A combination of different classifications allows a better description of the pathology and may categorize patient’s findings into subgroups that are similar in terms of prognosis and management. Further studies focused on classification development are needed to create improved systems with increased clinical utility and higher reliability.

Conflict of Interest

None of the authors has any potential conflict of interest.

Acknowledgment

This study was supported by the AO Spine Latin America. AO Spine is a clinical división of the AO Foundation, which is an independent medically guided Not-for-profit organization.

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