Variations in management of A3 and A4 cervical spine fractures as designated by the AO Spine Subaxial Injury Classification System

Barry Ting Sheen Kweh MBBS (Hons)1,2,3, Jin Wee Tee BMedSci, MBBS, MD, FRACS1,2,4, Sander Muijs MD, PhD5, F. Cumhur Oner MD, PhD5, Klaus John Schnake MD6, Lorin Michael Benneker MD, PhD7, Emiliano Neves Vialle MD, MSc8, Frank Kanziora MD, PhD9, Shanmuganathan Rajasekaran MCh, PhD, FRCS10, Gregory Schroeder MD11, Alexander R. Vaccaro MD, PhD11, and the AO Spine Subaxial Injury Classification System Validation Group, AndreyGrinMD Ahmed ShawkyAbdelgawaadMD Akbar JaleelZubairiFCOS Ortho AlejandroCastilloMD Alejo VernengoLezicaMD AlessandroRamieriMD, PhD AlfredoGuiroyMD AlonGrundshteinMD AmauriGodinhoJr.MD AminHenineMD Andrei A.PershinMD, PhD AlkinoosAthanasiouMD, PhD BaronZarate-KalfopulosMD SofienBenzartiMD ClaudioBernucciMD Brandon J.RebholzMD, FAAOS, BrunoDireito-SantosMS, MSc, FEBOT, Bruno LourençoCostaMD, MSc, BrunoSacilotoMD, CatalinMajerMD, PhD, ChadiTannouryMD, FAOA, FAAOS, ChristinaChengMD, Jason Pui YinCheungMD, ChristianKonradsMD, ChumponJetjumnongMD, Chun KeeChungMD, PhD, Eugen CezarPopescuMD, PhD, CumhurKilinçerMD, PhD, Colin B.HarrismMD, FAAOS, Craig D.SteinerMD, CristinaIgualadaMD, DarkoPerovicMD, PhD, David RuizPicazoMD, Luis DavidOrosco FalconeMD, DilipGopalakrishnanMS, DesaiAnkitMBBS, D.Ortho, DNB (Ortho), Devi PrakashTokalaFRCS (T&O), BalgopalKarmacharyaFCPS, RaphaelLotanMD, MHA, MahmoudShoaibMSc, SalvatoreRussoFRCS (NS), Arun KumariswanadhaMS, FACS, BhavukGargMS (Ortho), Noe DimasUribeCMOT, FabricioMedinaMD, JayakumarSubbiahDNB (Ortho), WaelAlsammakMD, ValentineMandizvidzaFCS-ECSA (Ortho), Ahmad ArieffAtanMD, RathinaveluBaraniMS (Ortho), MRCS (Ed), Hugo VilchisSámanoMD, Emilija StojkovskaPemovskaMD, Fabian CatarinoLopez HinojosaMD, TaolinFangMD, PhD, FedericoLandrielMD, Federico DanielSartorPhD, Marcus ViniciusDe Oliveira FerreiraMD, VitoFiorenzaMD, Francisco AlbertoMannaraMD, SeibertFranzProf. Dr. Mag., Brett A.FreedmanMD, Samuel Arsenio M.GrozmanMD, FPOA, FPCS, GuillermoEspinosaMD, Guillermo AlejandroRicciardiMD, GunaseelanPonnusamyMS (Ortho) UKM, Hassane AliAmadouMD, ItatiRomeroMD, JoostRutgesMD, PhD, JamesHarropMD, MSHQS, Jose-CarlosSauri-BarrazaMD, Jeevan KumarSharmaMBBS, MS (Ortho), FASSI, Jose Joefrey F.ArbatinJr.FPOA, Jeronimo B.MilanoMD, PhD, Jibin JosephFrancis(SA) FRCS (SN), John ChenLi TatMB BCh (NUI), BAO, LRCSI, FRCS (Ed), JoachimVahlMD, Jose AlfredoCorredorMD, João MorenoMoraisMD, JoanaGuasqueMD, JohnKoernerMD, DuerinckJohnnyMD, PhD, Jose RafaelPerozo RonMD, JuanDelgado-FernandezMD, Juan EstebanMuñoz Montoya JuanLouridoMD, ArielKaenPhD, Kubilay MuratÖzdenerMD, KonstantinosMargetisMD, PhD, KonstantinosPaterakisMD, Lady LozanoCariMD, LingjieFuMD, PhD, AhmedDawoudMD, Luis MuñizLunaMD, MahmoudAlkharsawiPhD, Maximo-AlbertoDiez-UlloaMD, Maria A.García-PalleroMD, MauroPluderiMD, PhD, MarceloGruenbergMD, MarceloValaccoMD, MarioGanauMD, PhD, MBA, FEBNS, Martin M.EstefanMD, Luis MiguelDuchén RodríguezMD, NaohisaMiyakoshiMD, PhD, MahmoudElshamlyMD, PhD, Mohamed FawzyKhattabMD, PhD, Sean R.SmithMD, MbarakAbeidMD, IgnacioGarfinkelMD, NicolaNicassioMD, NunoNevesPhD, Olga CarolinaMorillo AcostaMD, Pedro LuisBazánMD, PauloPereiraMD, PhD, PhedyLimMD, Patrick R.PritchardMD, PragneshBhattMS, MCh, FRCS, FEBNS, RaghurajKundangarMS (Ortho), Rian SouzaVieiraMD, RicardoRodrigues-PintoMD, PhD, Ripul R.PanchalDO, FACOS, FACS, RafaelLlombart-BlancoMD, PhD, Ronald AlbertoRioja RosasMD, RuiManilhaMD, RatkoYuracMD, SaraDinizMD, Scott C.WagnerMD, SegundoFuegoMD, SelvarajRamakrishnanMD, SerdarDemirözMD, ShafiqHacklaMBBS, MS (Ortho), DNB (Ortho), BabakShariatiFRCS, MohammadEl-SharkawiMD, PhD, YasunoriSorimachiMD, DMSc, PhD, StipeCorlukaMD, Sung-JooYuhMD, ThamiBenzakourMD, TarekElHewalaMD, PhD, TarunSuriMS, FNB (Spine surgery), Derek T.CawleyMMSc, MCh, FRCS, AdetunjiToluseMD, FWACS, FMCOrtho, CristianValdezMD, WaheedAbdulMD, WaqarHassanMD, YohanRobinsonMD, PhD, MBA, Zachary L.HickmanMD, FAANS, Mohamad Zaki HajiMohd AminMS Ortho, Oscar GonzálezGuerraMD, ZdenekKlezlMD, PhD,
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  • 1 National Trauma Research Institute, Melbourne, Victoria;
  • | 2 Department of Neurosurgery, The Alfred Hospital, Melbourne, Victoria;
  • | 3 Department of Neurosurgery, Royal Melbourne Hospital, Parkville, Melbourne, Victoria;
  • | 4 Central Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia;
  • | 5 Department of Orthopaedics, University Medical Center Utrecht, The Netherlands;
  • | 6 Center for Spinal Surgery, Schön Klinik Nürnberg Fürth, Germany;
  • | 7 Sonnenhofspital Bern, University of Bern, Switzerland;
  • | 8 Spine Surgery Group, Catholic University of Parana, Curitiba, Brazil;
  • | 9 Center for Spine Surgery and Neurotraumatology, Frankfurt, Germany;
  • | 10 Department of Orthopaedic and Spine Surgery, Ganga Hospital, Coimbatore, India; and
  • | 11 The Rothman Institute at Thomas Jefferson University, Philadelphia, Pennsylvania
Open access

OBJECTIVE

Optimal management of A3 and A4 cervical spine fractures, as defined by the AO Spine Subaxial Injury Classification System, remains controversial. The objectives of this study were to determine whether significant management variations exist with respect to 1) fracture location across the upper, middle, and lower subaxial cervical spine and 2) geographic region, experience, or specialty.

METHODS

A survey was internationally distributed to 272 AO Spine members across six geographic regions (North America, South America, Europe, Africa, Asia, and the Middle East). Participants’ management of A3 and A4 subaxial cervical fractures across cervical regions was assessed in four clinical scenarios. Key characteristics considered in the vignettes included degree of neurological deficit, pain severity, cervical spine stability, presence of comorbidities, and fitness for surgery. Respondents were also directly asked about their preferences for operative management and misalignment acceptance across the subaxial cervical spine.

RESULTS

In total, 155 (57.0%) participants completed the survey. Pooled analysis demonstrated that surgeons were more likely to offer operative intervention for both A3 (p < 0.001) and A4 (p < 0.001) fractures located at the cervicothoracic junction compared with fractures at the upper or middle subaxial cervical regions. There were no significant variations in management for junctional incomplete (p = 0.116) or complete (p = 0.342) burst fractures between geographic regions. Surgeons with more than 10 years of experience were more likely to operatively manage A3 (p < 0.001) and A4 (p < 0.001) fractures than their younger counterparts. Neurosurgeons were more likely to offer surgical stabilization of A3 (p < 0.001) and A4 (p < 0.001) fractures than their orthopedic colleagues. Clinicians from both specialties agreed regarding their preference for fixation of lower junctional A3 (p = 0.866) and A4 (p = 0.368) fractures. Overall, surgical fixation was recommended more often for A4 than A3 fractures in all four scenarios (p < 0.001).

CONCLUSIONS

The subaxial cervical spine should not be considered a single unified entity. Both A3 and A4 fracture subtypes were more likely to be surgically managed at the cervicothoracic junction than the upper or middle subaxial cervical regions. The authors also determined that treatment strategies for A3 and A4 subaxial cervical spine fractures varied significantly, with the latter demonstrating a greater likelihood of operative management. These findings should be reflected in future subaxial cervical spine trauma algorithms.

ABBREVIATIONS

SLIC = Subaxial Cervical Spine Injury Classification; VAS = visual analog scale.

OBJECTIVE

Optimal management of A3 and A4 cervical spine fractures, as defined by the AO Spine Subaxial Injury Classification System, remains controversial. The objectives of this study were to determine whether significant management variations exist with respect to 1) fracture location across the upper, middle, and lower subaxial cervical spine and 2) geographic region, experience, or specialty.

METHODS

A survey was internationally distributed to 272 AO Spine members across six geographic regions (North America, South America, Europe, Africa, Asia, and the Middle East). Participants’ management of A3 and A4 subaxial cervical fractures across cervical regions was assessed in four clinical scenarios. Key characteristics considered in the vignettes included degree of neurological deficit, pain severity, cervical spine stability, presence of comorbidities, and fitness for surgery. Respondents were also directly asked about their preferences for operative management and misalignment acceptance across the subaxial cervical spine.

RESULTS

In total, 155 (57.0%) participants completed the survey. Pooled analysis demonstrated that surgeons were more likely to offer operative intervention for both A3 (p < 0.001) and A4 (p < 0.001) fractures located at the cervicothoracic junction compared with fractures at the upper or middle subaxial cervical regions. There were no significant variations in management for junctional incomplete (p = 0.116) or complete (p = 0.342) burst fractures between geographic regions. Surgeons with more than 10 years of experience were more likely to operatively manage A3 (p < 0.001) and A4 (p < 0.001) fractures than their younger counterparts. Neurosurgeons were more likely to offer surgical stabilization of A3 (p < 0.001) and A4 (p < 0.001) fractures than their orthopedic colleagues. Clinicians from both specialties agreed regarding their preference for fixation of lower junctional A3 (p = 0.866) and A4 (p = 0.368) fractures. Overall, surgical fixation was recommended more often for A4 than A3 fractures in all four scenarios (p < 0.001).

CONCLUSIONS

The subaxial cervical spine should not be considered a single unified entity. Both A3 and A4 fracture subtypes were more likely to be surgically managed at the cervicothoracic junction than the upper or middle subaxial cervical regions. The authors also determined that treatment strategies for A3 and A4 subaxial cervical spine fractures varied significantly, with the latter demonstrating a greater likelihood of operative management. These findings should be reflected in future subaxial cervical spine trauma algorithms.

In Brief

The authors investigated global variations in the management of subaxial cervical spine injuries according to fracture location, morphological pattern, geographic region, surgeon experience, and clinician specialty. Fractures of both the A3 and A4 subtypes, as designated by the AO Spine Subaxial Injury Classification System, were more likely to be operatively managed if they occurred at the cervicothoracic junction compared with those at the upper or middle subaxial regions. These findings should be reflected in future treatment algorithms.

Cervical spine fracture occurs in 2.4% of trauma patients and has the potential to cause devastating neurological sequelae.1 The subaxial cervical spine is affected in more than 65% of patients. In particular, the lower junctional region, as the transitional point between the mobile lordotic cervical spine and rigid kyphotic thoracic spine, tends to be preferentially injured.1,2 Indeed, fractures of the lower two cervical vertebrae (C6 and C7) constitute as many as 55% of all cervical fractures.1–3 Despite this unequal distribution of injuries, which suggests that the junctional region is at greater risk for instability, the subaxial region is still perceived as a single entity by multiple contemporary classification systems.4–6

The current Subaxial Cervical Spine Injury Classification (SLIC) System recommends operative or nonoperative intervention on the basis of fracture pattern, integrity of the discoligamentous complex, and neurological state8,9 but fails to differentiate different forms of burst fracture.8,10 Conversely, the AO Spine Subaxial Injury Classification System does recognize incomplete (A3) and complete (A4) burst fracture morphologies and introduces fracture patterns to reflect their perceived stability in a gradated fashion. However, neither classification system takes into account the level of injury across the subaxial cervical spine.8 To guide the formation of a novel subaxial cervical spine trauma algorithm, the international variations in management of A3 and A4 fractures were investigated.

The principal aim of our study was to determine whether worldwide management preferences of incomplete and complete cervical burst fractures differ across the upper, middle, and lower subaxial cervical regions. We hypothesized that surgeons would be more likely to recommend operative management for fractures of the lower subaxial cervical spine involving the cervicothoracic junction, as well as those of a complete burst fracture morphology. These would represent crucial findings in guiding future prospective trials and treatment algorithms given the paucity of high-quality evidence available. A universally applicable and accepted treatment algorithm has the potential to greatly streamline and improve the worldwide standard of spine trauma care.7

Methods

Data Collection

A 43-point survey was globally distributed to 272 AO Spine members across six distinct geographic regions. These 272 participants were volunteers from the approximately 6500 members of the AO Spine community who expressed interest in validating a new subaxial cervical spine trauma algorithm. Participant demographic characteristics, such as years of experience, specialty, and geographic region of practice, were collected. The survey assessed clinician management preferences for subaxial cervical fractures at different cervical regions, both directly with discrete questioning and indirectly through various clinical scenarios. Surgeons were presented with four clinical vignettes involving A3 or A4 subaxial cervical fracture (Fig. 1). The hypothetical patients sustained injury to either the upper subaxial region as represented by a C3 fracture, middle level as illustrated by a C5 fracture, or the lower cervicothoracic junctional area as characterized by a C7 fracture. Participants expressed their treatment plan across the subaxial cervical regions in the context of several variables, such as degree of pain as measured with the visual analog scale (VAS) and extent of medical comorbidities. Significant medical comorbidity was defined as American Society of Anesthesiologists physical status classification score 3 or higher.12 Bias due to differing radiological interpretations of fracture morphologies was circumvented by the use of written clinical vignettes. The primary outcome was management preferences for surgery or rigid orthosis in the treatment of A3 and A4 cervical fractures across the upper, middle, and lower subaxial regions. Secondary outcome measures were variations in management according to experience, geographic region, and specialty.

FIG. 1.
FIG. 1.

A3 incomplete burst fracture involves a single endplate, whereas A4 complete burst fracture involves both endplates.11 Copyright AO Spine, AO Foundation. Published with permission. Figure is available in color online only.

Statistical Analysis

All partial and complete responses to the survey were included in the analysis by using a simple random sampling scheme. Baseline continuous demographic characteristics were analyzed according to their mean, median, or interquartile range. Categorical data were analyzed according to absolute frequency and percentage of complete responses. The chi-square test or Fisher’s exact test was used to analyze differences between categorical parameters, whereas the Cochran-Armitage test was used to assess for trends. Owing to underrepresentation of participants from the six different geographical regions, regions with a low number of participants were combined with their closest neighboring geographic region. The likelihood that a surgeon would offer operative intervention for A4 fracture compared with A3 fracture was also investigated by using ORs with 95% CIs. The statistical significance level was defined as p < 0.05. All statistical analysis was performed with SAS version 9.4 (SAS Institute Inc.).

Results

A total of 155 (57.0%) responses from specialists in six geographic regions were received. Baseline demographic characteristics are summarized in Table 1. Importantly, almost half the respondents worked in an academic center (49.7%), with a mean of 106.0 spine trauma patients treated per year.

TABLE 1.

Demographic characteristics of the 155 AO Spine members who completed the internationally distributed survey

CharacteristicValue
Subspecialty
 Orthopedics96 (61.9)
 Neurosurgery52 (33.5)
 Other7 (4.5)
Geographic region
 Europe48 (31.0)
 Latin & South America40 (25.8)
 Asia29 (18.7)
 North America17 (11.0)
 Middle East13 (8.4)
 Africa8 (5.2)
Years in practice
 <527 (17.4)
 5–1052 (33.5)
 11–2050 (32.3)
 >2026 (16.8)
Work setting
 Academic77 (49.7)
 Hospital54 (34.8)
 Private practice24 (15.5)
Treated spine trauma patients, no./yr
 Mean106.0
 Median50.0 (20–100)
 1–2543 (27.7)
 26–10087 (56.1)
 >10025 (16.1)

Values are shown as number (percent) or median (interquartile range).

Management Preferences for A3 and A4 Subaxial Cervical Spine Fractures

When confronted with incomplete burst fractures consistent with the A3 subtype of the AO Spine Subaxial Injury Classification System, surgeons expressed a significantly increased preference for surgical management in all four scenarios if injuries were located at the lower cervicothoracic junction (Table 2). This was true for patients who were neurologically intact, otherwise medically fit, and had minimal pain (p < 0.001), and even for those who had significant comorbidities (p = 0.002). In the cohort of patients who had significant pain but were otherwise appropriate for surgical intervention, surgeons were again more likely to recommend operative management for inferior junctional fractures at the lower subaxial region than those located at the upper or middle subaxial cervical regions (p = 0.004). Patients with a notable degree of pain and comorbidities also demonstrated a significant trend toward undergoing operative intervention if their injuries were located at the lower junctional region (p = 0.024). Pooled analysis of all four scenarios was consistent with this tenet of preferential management of cervicothoracic junctional A3 fracture with surgical fixation rather than rigid orthosis (p < 0.001) compared with more superiorly located injuries.

TABLE 2.

Management preferences for A3 and A4 subaxial cervical spine fractures, stratified by upper, middle, and lower cervical regions

Subaxial Cervical Spine LevelA3 Fracture Management Strategyp ValueA4 Fracture Management Strategyp Value*
Surgery (n [%])Rigid Orthosis (n [%])Surgery (n [%])Rigid Orthosis (n [%])
Scenario 1
 Upper34 (21.9)121 (78.1)<0.001104 (67.5)50 (32.5)0.165
 Middle43 (27.9)111 (72.1)111 (72.1)43 (27.9)
 Lower61 (39.6)93 (60.4)115 (74.7)39 (25.3)
Scenario 2
 Upper20 (13.0)134 (87.0)0.00273 (47.4)81 (52.6)0.022
 Middle22 (14.3)132 (85.7)87 (56.5)67 (43.5)
 Lower41 (26.6)113 (73.4)93 (60.4)61 (39.6)
Scenario 3§
 Upper66 (43.1)87 (56.9)0.004123 (80.4)30 (19.6)0.162
 Middle78 (51.0)75 (49.0)130 (85.0)23 (15.0)
 Lower91 (59.5)62 (40.5)132 (86.3)21 (13.7)
Scenario 4
 Upper49 (32.0)104 (68.0)0.02497 (63.4)56 (36.6)0.018
 Middle52 (34.0)101 (66.0)109 (71.2)44 (28.8)
 Lower68 (44.4)85 (55.6)116 (75.8)37 (24.2)
Pooled analysis
 Upper169 (27.5)446 (72.5)<0.001397 (64.7)217 (35.3)<0.001
 Middle195 (31.8)419 (68.2)437 (71.2)177 (28.8)
 Lower261 (42.5)353 (57.5)456 (74.3)158 (25.7)

Boldface type indicates statistical significance (p < 0.05).

Determined using the Cochran-Armitage trend test.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

A complete A4 burst fracture was also more likely to be managed operatively than its less severe A3 counterpart. Regardless of whether various key characteristics were altered, including degree of pain and presence of significant comorbidities, surgical intervention was preferred if the fracture was located at the cervicothoracic junction (Table 2). Although the individual scenarios failed to demonstrate a statistically significant difference in management of junctional A4 fractures, likely confounded by the overwhelming preference for surgical management of complete burst injuries in general, the pooled analysis confirmed that junctional complete burst fractures are preferentially treated with operative intervention compared with those fractures in the upper or middle cervical regions (p < 0.001).

Preferences According to Experience, Geographic Region, and Specialty

To determine whether degree of experience affected management of A3 and A4 fractures across the subaxial cervical spine, the cohort was dichotomized according to a threshold of 10 years of experience (Table 3). Interestingly, experienced surgeons tended to prefer surgery rather than rigid orthosis in comparison with their younger colleagues in the management of both incomplete burst (39.9% vs 28.0%, p < 0.001) and complete burst (75.9% vs 64.3%, p < 0.001) fractures across the entire subaxial cervical spine. Furthermore, there were no significant global differences in likelihood of offering operative intervention for single- or dual-endplate fractures across the individual four scenarios (Table 4). On pooled analysis, European surgeons were less inclined to favor operative management for A3 fracture compared with their American and Asian counterparts (p = 0.019). Overall, there was no significant regional variation in the management of A4 fractures, with the majority of clinicians opting to manage this fracture with surgical intervention rather than rigid orthosis (p = 0.918). On the other hand, pooled analysis of all four clinical scenarios revealed that neurosurgeons were more likely to offer operative intervention for A3 (39.9% vs 29.6%, p < 0.001) and A4 (76.3% vs 67.5%, p < 0.001) fractures compared with their orthopedic colleagues (Table 5). However, spine surgeons from both specialties exhibited similar preferences for operative management of lower junctional A3 (41.3% vs 42.1%, p = 0.866) and A4 (76.9% vs 73.5%, p = 0.368) fractures.

TABLE 3.

Participants who preferred surgical management for A3 and A4 subaxial cervical spine fractures, stratified by surgeon experience

Subaxial Cervical Spine LevelPreference for Surgery, Stratified by Experiencep Value
≤10 yrs (n = 79)>10 yrs (n = 76)
Scenario 1*
 A3
  Upper14 (17.7)20 (26.3)0.196
  Middle15 (19.2)28 (36.8)0.015
  Lower21 (26.9)40 (52.6)0.001
  Overall50 (21.1)88 (38.6)<0.001
 A4
  Upper49 (62.8)55 (72.4)0.206
  Middle52 (66.7)59 (77.6)0.129
  Lower52 (66.7)63 (82.9)0.021
  Overall153 (65.4)177 (77.6)0.004
Scenario 2
 A3
  Upper8 (10.3)12 (15.8)0.307
  Middle8 (10.3)14 (18.4)0.148
  Lower16 (20.5)25 (32.9)0.082
  Overall32 (13.7)51 (22.4)0.015
 A4
  Upper35 (44.9)38 (50.0)0.524
  Middle38 (48.7)49 (64.5)0.049
  Lower40 (51.3)53 (69.7)0.019
  Overall113 (48.3)140 (61.4)0.005
Scenario 3
 A3
  Upper29 (37.7)37 (48.7)0.169
  Middle33 (42.9)45 (59.2)0.043
  Lower40 (51.9)51 (67.1)0.056
  Overall102 (44.2)133 (58.3)0.002
 A4
  Upper57 (74.0)66 (86.8)0.046
  Middle62 (80.5)68 (89.5)0.121
  Lower62 (80.5)70 (92.1)0.037
  Overall181 (78.4)204 (89.5)0.001
Scenario 4§
 A3
  Upper23 (29.9)26 (34.2)0.565
  Middle23 (29.9)29 (38.2)0.279
  Lower31 (40.3)37 (48.7)0.294
  Overall77 (33.3)92 (40.4)0.119
 A4
  Upper47 (61.0)50 (65.8)0.542
  Middle50 (64.9)59 (77.6)0.083
  Lower54 (70.1)62 (81.6)0.098
  Overall151 (65.4)171 (75.0)0.024
Pooled analysis
 A3
  Upper74 (23.8)95 (31.3)0.038
  Middle79 (25.5)116 (38.2)<0.001
  Lower108 (34.8)153 (50.3)<0.001
  Overall261 (28.0)364 (39.9)<0.001
 A4
  Upper188 (60.6)209 (68.8)0.036
  Middle202 (65.2)235 (77.3)<0.001
  Lower208 (67.1)248 (81.6)<0.001
  Overall598 (64.3)692 (75.9)<0.001

Boldface type indicates statistical significance (p < 0.05). Values are shown as number (percent) unless indicated otherwise.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

TABLE 4.

Participants who preferred surgical management for A3 and A4 subaxial cervical spine fractures, stratified by geographic region

Subaxial Cervical Spine LevelPreference for Surgery, Stratified by Regionp Value
North, Latin, & South America (n = 57)Europe (n = 48)Africa, Asia, & the Middle East (n = 50)
Scenario 1*
 A3
  Upper14 (24.6)9 (18.8)11 (22.0)0.773
  Middle17 (29.8)10 (20.8)16 (32.7)0.397
  Lower23 (40.4)17 (35.4)21 (42.9)0.748
  Overall54 (31.6)36 (25.0)48 (32.4)0.311
 A4
  Upper38 (66.7)35 (72.9)31 (63.3)0.588
  Middle38 (66.7)38 (79.2)35 (71.4)0.361
  Lower42 (73.7)39 (81.3)34 (69.4)0.396
  Overall118 (69.0)112 (77.8)100 (68.0)0.124
Scenario 2
 A3
  Upper10 (17.5)5 (10.4)5 (10.2)0.435
  Middle11 (19.3)4 (8.3)7 (14.3)0.278
  Lower19 (33.3)9 (18.8)13 (26.5)0.242
  Overall40 (23.4)18 (12.5)25 (17.0)0.040
 A4
  Upper30 (52.6)23 (47.9)20 (40.8)0.477
  Middle32 (56.1)27 (56.3)28 (57.1)0.994
  Lower36 (63.2)31 (64.6)26 (53.1)0.441
  Overall98 (57.3)81 (56.3)74 (50.3)0.420
Scenario 3
 A3
  Upper25 (43.9)20 (41.7)21 (43.8)0.970
  Middle27 (47.4)24 (50.0)27 (56.3)0.654
  Lower35 (61.4)28 (58.3)28 (58.3)0.933
  Overall87 (50.9)72 (50.0)76 (52.8)0.890
 A4
  Upper46 (80.7)36 (75.0)41 (85.4)0.437
  Middle47 (82.5)40 (83.3)43 (89.6)0.554
  Lower51 (89.5)41 (85.4)40 (83.3)0.646
  Overall144 (84.2)117 (81.3)124 (86.1)0.527
Scenario 4§
 A3
  Upper20 (35.1)14 (29.2)15 (31.3)0.803
  Middle20 (35.1)13 (27.1)19 (39.6)0.423
  Lower28 (49.1)16 (33.3)24 (50.0)0.173
  Overall68 (39.8)43 (29.9)58 (40.3)0.112
 A4
  Upper38 (66.7)29 (60.4)30 (62.5)0.181
  Middle38 (66.7)32 (66.7)39 (81.3)0.181
  Lower46 (80.7)33 (68.8)37 (77.1)0.352
  Overall122 (71.3)94 (65.3)106 (73.6)0.276
Pooled analysis
 A3
  Upper69 (30.3)48 (25.0)52 (26.7)0.462
  Middle75 (32.9)51 (26.6)69 (35.6)0.148
  Lower105 (46.1)70 (36.5)86 (44.3)0.116
  Overall249 (36.4)169 (29.3)207 (35.5)0.019
 A4
  Upper152 (66.7)123 (64.1)122 (62.9)0.705
  Middle155 (68.0)137 (71.4)145 (74.7)0.311
  Lower175 (76.8)144 (75.0)137 (70.6)0.342
  Overall482 (70.5)404 (70.1)404 (69.4)0.918

Boldface type indicates statistical significance (p < 0.05). Values are shown as number (percent) unless indicated otherwise.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

TABLE 5.

Participants who preferred surgical management for A3 and A4 subaxial cervical spine fractures, stratified by surgical specialty

Subaxial Cervical Spine LevelPreference for Surgery, Stratified by Specialtyp Value
Orthopedics (n = 96)Neurosurgery (n = 52)
Scenario 1*
 A3
  Upper17 (17.7)14 (26.9)0.189
  Middle22 (23.2)19 (36.5)0.084
  Lower40 (42.1)17 (32.7)0.263
  Overall79 (27.6)50 (32.1)0.328
 A4
  Upper62 (65.3)39 (75.0)0.224
  Middle67 (70.5)41 (78.8)0.275
  Lower70 (73.7)41 (78.8)0.487
  Overall199 (69.8)121 (77.6)0.082
Scenario 2
 A3
  Upper10 (10.5)8 (15.4)0.390
  Middle10 (10.5)10 (19.2)0.141
  Lower26 (27.4)12 (23.1)0.570
  Overall46 (16.1)30 (19.2)0.411
 A4
  Upper40 (42.1)30 (57.7)0.070
  Middle49 (51.6)35 (67.3)0.065
  Lower58 (61.1)32 (61.5)0.954
  Overall147 (51.6)97 (62.2)0.032
Scenario 3
 A3
  Upper32 (34.0)29 (55.8)0.011
  Middle40 (42.6)34 (65.4)0.008
  Lower53 (56.4)32 (61.5)0.545
  Overall125 (44.3)95 (60.9)<0.001
 A4
  Upper73 (77.7)45 (86.5)0.192
  Middle79 (84.0)46 (88.5)0.466
  Lower80 (85.1)46 (88.5)0.572
  Overall232 (82.3)137 (87.8)0.127
Scenario 4§
 A3
  Upper22 (23.4)24 (46.2)0.005
  Middle24 (25.5)25 (48.1)0.006
  Lower40 (42.6)25 (48.1)0.520
  Overall86 (30.5)74 (47.4)<0.001
 A4
  Upper53 (56.4)39 (75.0)0.026
  Middle64 (68.1)41 (78.8)0.167
  Lower70 (74.5)41 (78.8)0.553
  Overall187 (66.3)121 (77.6)0.014
Pooled analysis
 A3
  Upper81 (21.4)75 (36.1)<0.001
  Middle96 (25.4)88 (42.3)<0.001
  Lower159 (42.1)86 (41.3)0.866
  Overall336 (29.6)249 (39.9)<0.001
 A4
  Upper228 (60.3)153 (73.6)0.001
  Middle259 (68.5)163 (78.4)0.011
  Lower278 (73.5)160 (76.9)0.368
  Overall765 (67.5)476 (76.3)<0.001

Boldface type indicates statistical significance (p < 0.05). Values are shown as number (percent) unless indicated otherwise.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

Misalignment Acceptance Rate

Clinicians accepted significantly different degrees of malalignment across the subaxial cervical spine in the management of A3 and A4 fractures sustained by medically fit, neurologically intact patients (p = 0.040). In particular, misalignment was less tolerated at the cervicothoracic junction (61.2% of participants) compared with the middle (47.4%) and upper (44.7%) subaxial cervical regions (Supplementary Table 1). There was no statistically significant difference with respect to the misalignment acceptance rate, and thus willingness to conservatively manage cervical burst fractures with rigid orthosis rather than surgical fixation, when stratified according to years of experience or geographic region of practice (Supplementary Tables 2 and 3). However, compared with their neurosurgical counterparts, orthopedic spine specialists indicated that they had a significantly lower tolerance of misalignment of A3 injuries compared with A4 injuries (p = 0.046). Despite this, there was no difference between the two specialties with respect to management of A3 or A4 fractures across the subaxial cervical spine (Supplementary Table 4).

AO Spine Subaxial Injury Classification System

This survey also provided unique insight into clinician management preferences for incomplete and complete burst fractures without radiological interpretation as a confounder. Surgeons overwhelmingly preferred operative fixation for the management of A4 fractures compared with A3 injuries in all four scenarios throughout the subaxial cervical spine (Table 6). This is consistent with the logical and gradated manner in which the AO Spine Subaxial Injury Classification System introduces fracture patterns from least to most severe. In neurologically intact patients with minimal cervical pain (VAS ≤ 4/10) on mobilization who were deemed fit for surgery, A4 fractures were more likely to be treated with operative intervention than A3 fractures in the upper (OR 7.40, 95% CI 4.45–12.31, p < 0.001), middle (OR 6.66, 95% CI 4.05–10.96, p < 0.001), and lower (OR 4.50, 95% CI 2.77–7.31, p < 0.001) cervical regions.

TABLE 6.

Management strategies for A3 versus A4 subaxial cervical spine fractures

Subaxial Cervical Spine LevelManagement StrategyOR (95% CI)*p Value
SurgeryRigid Orthosis
Scenario 1
 Upper
  A334 (21.9)121 (78.1)7.40 (4.45–12.31)<0.001
  A4104 (67.5)50 (32.5)
 Middle
  A343 (27.9)111 (72.1)6.66 (4.05–10.96)<0.001
  A4111 (72.1)43 (27.9)
 Lower
  A361 (39.6)93 (60.4)4.50 (2.77–7.31)<0.001
  A4115 (74.7)39 (25.3)
Scenario 2
 Upper
  A320 (13.0)134 (87.0)6.04 (3.43–10.64)<0.001
  A473 (47.4)81 (52.6)
 Middle
  A322 (14.3)132 (85.7)7.79 (4.48–13.54)<0.001
  A487 (56.5)67 (43.5)
 Lower
  A341 (26.6)113 (73.4)4.20 (2.60–6.80)<0.001
  A493 (60.4)61 (39.6)
Scenario 3§
 Upper
  A366 (43.1)87 (56.9)5.40 (3.24–9.01)<0.001
  A4123 (80.4)30 (19.6)
 Middle
  A378 (51.0)75 (49.0)5.43 (3.15–9.37)<0.001
  A4130 (85.0)23 (15.0)
 Lower
  A391 (59.5)62 (40.5)4.28 (2.44–7.51)<0.001
  A4132 (86.3)21 (13.7)
Scenario 4
 Upper
  A349 (32.0)104 (68.0)3.68 (2.29–5.90)<0.001
  A497 (63.4)56 (36.6)
 Middle
  A352 (34.0)101 (66.0)4.81 (2.96–7.81)<0.001
  A4109 (71.2)44 (28.8)
 Lower
  A368 (44.4)85 (55.6)3.92 (2.40–6.39)<0.001
  A4116 (75.8)37 (24.2)

Boldface type indicates statistical significance (p < 0.05). Values are shown as number (percent) unless indicated otherwise.

Indicates the likelihood of surgical intervention for A4 fracture compared with A3 fracture.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, minimal cervical axial pain (VAS ≤ 4/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, and deemed fit for surgery.

Patient without neurological deficits, significant cervical axial pain (VAS ≥ 5/10) on mobilization, stable cervical spine, significant comorbidities, and deemed fit for surgery.

Similar findings were also observed in patients with significant comorbidities. Complete burst fractures were again more likely to be managed surgically than incomplete burst fractures in the upper (OR 6.04, 95% CI 3.43–10.64, p < 0.001), middle (OR 7.79, 95% CI 4.48–13.54, p < 0.001), and lower (OR 4.20, 95% CI 2.60–6.80, p < 0.001) subaxial regions. Once again, patients with A3 junctional fractures in the lower subaxial spine were also more likely to be offered intervention than patients with similar fractures elsewhere. When significant pain (VAS ≥ 5/10) was introduced into preoperative decision-making, surgeons were again more likely to recommend surgical fixation for A4 fractures than A3 fractures across the upper (OR 5.40, 95% CI 3.24–9.01, p < 0.001), middle (OR 5.43, 95% CI 3.15–9.37, p < 0.001), and lower (OR 4.28, 95% CI 2.44–7.51, p < 0.001) subaxial regions. Consistent with previous scenarios, cervicothoracic junctional A3 fractures were also more likely to be operatively managed than those located elsewhere.

Finally, complex surgical decision-making was interrogated with challenging clinical vignettes in which perioperative risk of comorbidities needed to be weighed against the benefits of operative intervention such as spinal stability and analgesic effect. In this instance, the AO Spine Subaxial Injury Classification System held true, with A4 fractures more likely to be deemed suitable for operative management at every cervical region. Importantly, there was less management variation at C3 (OR 3.68, 95% CI 2.29–5.90, p < 0.001) and C7 (OR 3.92, 95% CI 2.40–6.39, p < 0.001) than for fractures located in the middle location (OR 4.81, 2.96–7.81, p < 0.001). In other words, this scenario indirectly demonstrates that surgeons were more likely to surgically manage A3 fractures at the lower cervicothoracic junction than those at the upper or middle subaxial regions.

Discussion

Traumatic spine injury in the cervical region results in the highest rate of complete motor and sensory neurological deficit.13 Although the considerable range of motion afforded by the cervical’s spine reliance upon ligamentous structures rather than bony stability is a functional advantage, it simultaneously confers a particular susceptibility to injury and instability.14–16 In turn, this leads to a significant risk of morbidity and mortality given the potential for high spinal cord injury and permanent neurological deficit.14–16 As such, there are ongoing international efforts to formulate both a universal classification system and accepted treatment algorithm.8,17–19 Our survey addresses both these subjects. We determined that junctional subaxial cervical region fractures are more likely to be operatively managed, and also that the AO Spine Subaxial Injury Classification System represents a logical progression of injury morphology because A4 fractures were more likely to be surgically stabilized than A3 fractures.20

There is an unequal distribution of dislocations and fractures across the subaxial cervical spine, with as many as 90% of fractures occurring in the middle and lower regions.1,21 As the transitional point between the comparatively mobile lordotic cervical spine and the more rigid kyphotic thoracic spine, the cervicothoracic junction is especially vulnerable to mechanical instability and disruption.22,23 Fractures affecting the lower two cervical vertebra (C6 and C7) have been estimated to constitute between 39% and 55% of all cervical fractures.1–3 More specifically, the C6–7 level is the most commonly fractured level of the subaxial cervical spine (21.2%).24 This is closely followed by fracture of C7 or dislocation at the C7/T1 junction, which account for 17% of all injuries.25 Quarrington et al. also found that the C6–7 level was the most commonly involved level for facet dislocation.26 This pattern of fractures and dislocations that preferentially occur in the lower subaxial spine reflects this region’s increased vulnerability to injury. The results of our worldwide survey are consistent with this tenet.

Indeed, we determined that junctional fractures of both the A3 (p < 0.001) and A4 (p < 0.001) subtypes are more likely to be managed with operative intervention than injuries located elsewhere. Furthermore, the current AO Spine Subaxial Injury Classification System differentiates between incomplete and complete burst fracture morphologies, but it does not take into account the subaxial spine level as a formal discrete category or modifier.8 Similarly, the Spine Section of the German Society for Orthopedics and Trauma (DGOU) advocates surgical fixation for complete burst fractures of the subaxial cervical spine, while suggesting that rigid orthosis and close observation may be considered for neurologically intact patients with incomplete burst fracture.27 However, the level of the subaxial cervical fracture is not taken into account by the DGOU algorithm.27 Our novel finding of a consistent global preference for operative intervention for fractures located at the cervicothoracic region, compared with fractures at the upper and middle regional cervical regions, was evident even in patients with significant comorbidities (p = 0.002). As such, we advocate for consideration of inclusion of the level of subaxial cervical spine injury in future classification and treatment algorithms.

Unfortunately, there is a distinct paucity of prospective data that directly compare surgical outcomes after operative and nonoperative management of subaxial cervical spine fractures stratified by level of injury. Koivikko et al. examined 69 neurologically intact patients with burst or teardrop fractures who underwent either surgical decompression and stabilization or skull traction and halo bracing.21 The operative cohort experienced superior outcomes with respect to improved Frankel grade of neurological status, reduced spinal canal narrowing, and less kyphotic deformity compared with the nonoperative group.21 Importantly, 67 of 69 patients had middle and lower cervical fractures (C5–7). Toh et al. and Fisher et al. concurred with the role of surgical intervention for fractures of the middle and lower cervical spine, and they advocated for an anterior rather than posterior or conservative approach owing to superior decompression and overall outcome.28,29 Overall, these studies favored operative intervention for the management of lower cervical fracture, which is consistent with the preferences expressed in our global survey. Nonetheless, there is still a need for randomized trials to confirm this apparent treatment benefit.

Numerous treatment algorithms, with varying degrees of usability and reliability, have been proposed to guide clinical decision-making for the management of subaxial cervical spine fracture. The Allen and Ferguson system attempted to classify injuries according to six main mechanisms of injury but is based on findings on plain radiography, which Song et al. argued makes it less applicable today.6,30 Likewise, the Harris classification divides subaxial cervical spine injuries into five categories on the basis of mechanism.5 On the other hand, the pioneering AO Spine Subaxial Injury Classification System introduced by Vaccaro et al. in 2016 divides injuries into three main categories: type A (compression), type B (distraction), and type C (translation). Each category introduces fracture patterns in a logical gradated manner of increasing severity.8 This methodological classification has shown serviceable intraobserver and interobserver reliability for all categories.8 Our study provided original compelling evidence that type A4 complete burst fracture is overwhelmingly believed to be more severe than A3 incomplete burst fracture, and thus more likely to be operatively managed irrespective of patient comorbidity status (p < 0.001).

This is not to state that the algorithm is beyond refinement. Indeed, others have challenged the reliability of the AO Spine Subaxial Injury Classification System. Silva et al. astutely noted that B type and facet injuries are often poorly distinguished.18 Only the extremes of injuries, whether minor or severe, were reliably rated while the use of facet modifiers was relatively imprecise and difficult to assess.18 Hitti et al. also attempted to modify the system by incorporating comorbidities, such as osteoporosis, in an attempt to predict failure of nonoperative treatment.19 The significance of using modifiers to address additional determinants of stability was addressed by Divi et al., who incorporated important conditions such as ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis into the system.31 It is evident that treatment algorithms are continuously evolving. We propose, much like Schleicher et al., that not only does fracture morphology carry importance but also the level of the affected subaxial cervical region.32 Indeed, fracture location at a junctional region has already been incorporated into the validated Spine Instability Neoplastic Score as contributing additional points toward instability.33

The rationale behind developing a subaxial cervical spine algorithm is the sizable morbidity and mortality rate attributed to these devastating fractures. Sokolowski et al. found that the overall acute mortality rate for all patients with cervical spine injury was 5.92%.16 On subgroup analysis, the elderly population age 65 years or older had an astonishingly high acute mortality rate of 18%.34 Overall, 86% of elderly patients age 65 years and older survived, compared with 96.1% of their younger counterparts. When Lenoir et al. exclusively evaluated patients with unstable fracture of the cervicothoracic junction, they found an even higher mortality rate of 23%. This observed variability in overall survival rate across the subaxial cervical spine was reflected in our international study, which demonstrated that statistically significant variations in management do indeed exist according to the subaxial cervical region affected.35

A criticism that may be leveled against any spine fracture treatment algorithm is its applicability and generalizability. Management preferences may vary according to region and surgeon experience, as well as between surgical specialties. We investigated all of these factors in our global survey. Generally, there were no significant discrepancies in management preferences across the three stratified regions of the Americas, Europe, and finally the combined region of Africa, Asia, and the Middle East. The only noteworthy finding was that European spinal specialists were less inclined to offer surgical management for A3 fractures than their American and Asian colleagues (p = 0.019). Misalignment acceptance rates were also similar across geographic regions. This is a testament to the universality of the AO Spine Subaxial Injury Classification System.

From an experiential standpoint, surgeons with more than 10 years of experience were more likely to operatively manage incomplete (p < 0.001) and complete (p < 0.001) burst fractures than their younger colleagues. It could be argued that there is evidence in the overall surgical population that experienced surgeons may have lower postoperative complication and mortality rates than younger surgeons and therefore we should defer to their experience.36 Alternatively, these better outcomes could be attributed to other factors, such as the experienced surgeon’s skillset rather than their decision-making. This is an intriguing finding with potential for further investigations to evaluate postoperative outcomes in this particular population according to surgeon experience.

Finally, neurosurgeons preferred operative intervention for the management of traumatic A3 (p < 0.001) and A4 (p < 0.001) fractures in comparison with their orthopedic colleagues on pooled analysis. However, it is telling that both groups agreed regarding the management of both A3 (p = 0.866) and A4 (p = 0.368) junctional fractures in the lower subaxial cervical region, despite offering different treatment strategies for fractures in the upper and middle regions. It has been suggested that neurosurgeons perform a higher overall volume of spinal procedures during their training than orthopedic surgeons, but they do have a reduced focus on spinal deformity surgery.37 The purpose of highlighting potential intrinsic specialty bias regarding management preferences is to raise self-awareness among spinal surgeons and encourage multidisciplinary discussion.

Another consideration for our survey was the potential for nuances in radiological interpretation and classification of fracture types to act as confounders of variations in treatment strategy. Fortunately, Schroeder et al. already demonstrated that the interpretation of A3 and A4 fractures, as incomplete and complete burst fractures in the thoracolumbar spine, is not affected by region or experience.38 However, this has yet to be definitively shown for the subaxial cervical spine. Our didactic survey circumvented this potential for radiological bias by evaluating preferences for surgical or nonoperative management with predefined incomplete and complete subaxial fractures.

A major strength of our study was the global nature of our survey, spanning six distinct geographic regions. Participants had varying levels of experience, backgrounds, and specialties. We also assessed clinician surgical strategy directly with questions as well as indirectly with several clinical vignettes. The fact that our study eliminated radiological interpretation of fracture subtype as a potential confounder of management preference was also an advantage. However, our study was not without limitations. Rather than being based on prospective randomized clinical data, our conclusions were drawn from international clinician opinions. Although we achieved statistical significance for our primary and secondary outcomes, only 57% of addressed participants responded and the majority of our participants were from academic spine centers. This may lend a degree of confidence that we gathered data from involved experts working in leading tertiary institutions, but this may also mean that the results carry less external validity given the potential for volunteer bias. As with any survey, there is also a potential for nonresponder bias. However, we attempted to counteract this by using a simple random sampling scheme. Our subgroup analysis was also limited by the fact that some geographic areas were underrepresented, such as Asia and North America, and therefore had to be combined with their nearest neighboring geographic region. It is evident that there is still a need for large high-quality prospective trials to elucidate the optimal management strategy for fractures across the subaxial cervical spine.

As Joaquim et al. and Cruz et al. previously posited, accurate decision-making guided by an algorithm may not only lead to patients undergoing operative intervention in a timely fashion, but also decrease the number of patients who undergo an operation, and are therefore exposed to its associated risks, that may not necessarily be indicated.18,39,40 Our international survey is the first to encapsulate the current management preferences for incomplete and complete burst fractures of the subaxial cervical spine. This is especially important given the current dearth of clinical patient data relating to patient outcomes after these potentially devastating neurological injuries.

Conclusions

The subaxial cervical spine should not be considered a single unified entity. Fractures of both the A3 and A4 subtypes were more likely to be surgically managed if they occurred at the cervicothoracic junction compared with those at the upper or middle subaxial regions. There was significant management variation between A3 and A4 injuries across the subaxial cervical spine, with surgeons displaying a greater preponderance to operatively manage the latter fracture morphology subtype. These findings warrant further investigation in multicenter randomized trials prior to incorporation into future algorithms for the treatment of subaxial cervical spine trauma.

Acknowledgments

The authors would like to thank Christian Knoll (AO Innovation Translation Center, Clinical Science) for his support with statistical analysis.

Appendix

AO Spine Subaxial Injury Classification System Validation Group Members

Andrey Grin, MD,1 Ahmed Shawky Abdelgawaad, MD,2 Akbar Jaleel Zubairi, FCOS Ortho,3 Alejandro Castillo, MD,4 Alejo Vernengo Lezica, MD,5 Alessandro Ramieri, MD, PhD,6 Alfredo Guiroy, MD,7 Alon Grundshtein, MD,8 Amauri Godinho Jr., MD,9 Amin Henine, MD,10 Andrei A. Pershin, MD, PhD,11 Alkinoos Athanasiou, MD, PhD,12 Baron Zarate-Kalfopulos, MD,13 Sofien Benzarti, MD,14 Claudio Bernucci, MD,15 Brandon J. Rebholz, MD, FAAOS,16 Bruno Direito-Santos, MS, MSc, FEBOT,17 Bruno Lourenço Costa, MD, MSc,18 Bruno Saciloto, MD,19 Catalin Majer, MD, PhD,20 Chadi Tannoury, MD, FAOA, FAAOS,21 Christina Cheng, MD,22 Jason Pui Yin Cheung, MD,23 Christian Konrads, MD,24 Chumpon Jetjumnong, MD,25 Chun Kee Chung, MD, PhD,26 Eugen Cezar Popescu, MD, PhD,27 Cumhur Kilinçer, MD, PhD,28 Colin B. Harrism, MD, FAAOS,29 Craig D. Steiner, MD,30 Cristina Igualada, MD,31 Darko Perovic, MD, PhD,32 David Ruiz Picazo, MD,33 Luis David Orosco Falcone, MD,34 Dilip Gopalakrishnan, MS,35 Desai Ankit, MBBS, D.Ortho, DNB (Ortho),36 Devi Prakash Tokala, FRCS (T&O),37 Balgopal Karmacharya, FCPS,38 Raphael Lotan, MD, MHA,39 Mahmoud Shoaib, MSc,40 Salvatore Russo, FRCS (NS),41 Arun Kumar Viswanadha, MS, FACS,42 Bhavuk Garg, MS (Ortho),43 Noe Dimas Uribe, CMOT,44 Fabricio Medina, MD,45 Jayakumar Subbiah, DNB (Ortho),46 Wael Alsammak, MD,47 Valentine Mandizvidza, FCS-ECSA (Ortho),48 Ahmad Arieff Atan, MD,49 Rathinavelu Barani, MS (Ortho), MRCS (Ed),50 Hugo Vilchis Sámano, MD,51 Emilija Stojkovska Pemovska, MD,52 Fabian Catarino Lopez Hinojosa, MD,53 Taolin Fang, MD, PhD,54 Federico Landriel, MD,55 Federico Daniel Sartor, PhD,56 Marcus Vinicius De Oliveira Ferreira, MD,57 Vito Fiorenza, MD,58 Francisco Alberto Mannara, MD,59 Seibert Franz, Prof. Dr. Mag.,60 Brett A. Freedman, MD,61 Samuel Arsenio M. Grozman, MD, FPOA, FPCS,62 Guillermo Espinosa, MD,63 Guillermo Alejandro Ricciardi, MD,64 Gunaseelan Ponnusamy, MS (Ortho) UKM,65 Hassane Ali Amadou, MD,66 Itati Romero, MD,67 Joost Rutges, MD, PhD,68 James Harrop, MD, MSHQS,69 Jose-Carlos Sauri-Barraza, MD,70 Jeevan Kumar Sharma, MBBS, MS (Ortho), FASSI,71 Jose Joefrey F. Arbatin Jr., FPOA,72 Jeronimo B. Milano, MD, PhD,73 Jibin Joseph Francis, (SA) FRCS (SN),74 John Chen Li Tat, MB BCh (NUI), BAO, LRCSI, FRCS (Ed),75 Joachim Vahl, MD,76 Jose Alfredo Corredor, MD,77 João Moreno Morais, MD,78 Joana Guasque, MD,79 John Koerner, MD,80 Duerinck Johnny, MD, PhD,81 Jose Rafael Perozo Ron, MD,82 Juan Delgado-Fernandez, MD,83 Juan Esteban Muñoz Montoya,84 Juan Lourido, MD,85 Ariel Kaen, PhD,86 Kubilay Murat Özdener, MD,87 Konstantinos Margetis, MD, PhD,88 Konstantinos Paterakis, MD,89 Lady Lozano Cari, MD,90 Lingjie Fu, MD, PhD,91 Ahmed Dawoud, MD,92 Luis Muñiz Luna, MD,93 Mahmoud Alkharsawi, PhD,94 Maximo-Alberto Diez-Ulloa, MD,95 Maria A. García-Pallero, MD,96 Mauro Pluderi, MD, PhD,97 Marcelo Gruenberg, MD,98 Marcelo Valacco, MD,99 Mario Ganau, MD, PhD, MBA, FEBNS,100 Martin M. Estefan, MD,101 Luis Miguel Duchén Rodríguez, MD,102 Naohisa Miyakoshi, MD, PhD,103 Mahmoud Elshamly, MD, PhD,104 Mohamed Fawzy Khattab, MD, PhD,105 Sean R. Smith, MD,106 Mbarak Abeid, MD,107 Ignacio Garfinkel, MD,108 Nicola Nicassio, MD,109 Nuno Neves, PhD,110 Olga Carolina Morillo Acosta, MD,111 Pedro Luis Bazán, MD,112 Paulo Pereira, MD, PhD,113 Phedy Lim, MD,114 Patrick R. Pritchard, MD,115 Pragnesh Bhatt, MS, MCh, FRCS, FEBNS,116 Raghuraj Kundangar, MS (Ortho),117 Rian Souza Vieira, MD,118 Ricardo Rodrigues-Pinto, MD, PhD,119 Ripul R. Panchal, DO, FACOS, FACS,120 Rafael Llombart-Blanco, MD, PhD,121 Ronald Alberto Rioja Rosas, MD,122 Rui Manilha, MD,123 Ratko Yurac, MD,124 Sara Diniz, MD,125 Scott C. Wagner, MD,126 Segundo Fuego, MD,127 Selvaraj Ramakrishnan, MD,128 Serdar Demiröz, MD,129 Shafiq Hackla, MBBS, MS (Ortho), DNB (Ortho),130 Babak Shariati, FRCS,131 Mohammad El-Sharkawi, MD, PhD,132 Yasunori Sorimachi, MD, DMSc, PhD,133 Stipe Corluka, MD,134 Sung-Joo Yuh, MD,135 Thami Benzakour, MD,136 Tarek ElHewala, MD, PhD,137 Tarun Suri, MS, FNB (Spine surgery),138 Derek T. Cawley, MMSc, MCh, FRCS,139 Adetunji Toluse, MD, FWACS, FMCOrtho,140 Cristian Valdez, MD,141 Waheed Abdul, MD,142 Waqar Hassan, MD,143 Yohan Robinson, MD, PhD, MBA,144 Zachary L. Hickman, MD, FAANS,145 Mohamad Zaki Haji Mohd Amin, MS Ortho,146 Oscar González Guerra, MD,147 and Zdenek Klezl, MD, PhD.148

1The Division of Emergency Neurosurgery in Sklifosovskiy Research Institute of Emergency Medicine, Moscow, Russia. 2Helios Klinikum Erfurt, Erfurt, Germany. 3The Aga Khan University, Karachi City, Sindh, Pakistan. 4Hospital Nacional Alberto Sabogal, Lima, Peru. 5San Isidro Hospital, Buenos Aires, Argentina. 6SAIMLAL Department, La Sapienza University, Rome, Italy. 7Spine Surgery, Orthopedic Department, Spanish Hospital, Mendoza, Argentina. 8The Spinal Surgery Unit, Oxford University Hospital NHS Foundation Trust, Oxford, United Kingdom. 9State Health Secretary–Federal District, Brasilia, Brazil. 10C.O.A. Department University Hospital Center of Douera, Algiers, Algeria. 11Albrecht Federal Scientific Centre of Rehabilitation of the Disabled, St. Petersburg, Russian Federation. 12Aristotle University of Thessaloniki, School of Medicine, Serres, Greece. 13Instituto Nacional de Rehabilitación, Mexico City, Mexico. 14Orthopedic Department, Sahloul University Hospital, Sousse, Tunisia. 15Neurosurgery Department, ASST Papa Giovanni XXIII Hospital, Bergamo, Italy. 16Medical College of Wisconsin, Milwaukee, WI. 17Hospital de Braga, Braga, Portugal. 18Centro Hospitalar Universitário da Cova da Beira, Covilhã, Portugal. 19Hospital São Vicente de Paulo, Guarapuava, Brazil. 20Neuro Spinal Hospital, Dubai, United Arab Emirates. 21Boston University Medical Center, Boston, MA. 22University Hospitals Cleveland Medical Center, Cleveland, OH. 23Department of Orthopedics and Traumatology, The University of Hong Kong, Hong Kong SAR, China. 24Department for Trauma and Reconstructive Surgery, BG Klinik, University of Tübingen, Tübingen, Germany. 25Department of Neurosurgery, Faculty of Medicine, Chiangmai University, Thailand. 26Department of Neurosurgery, Seoul National University, Seoul, South Korea.27 “Prof. Dr. N. Oblu” Emergency Hospital, Iasi, Romania. 28Trakya University Faculty of Medicine, Edirne, Turkey. 29Centers for Neurosurgery, Spine and Orthopedics, Rutgers–New Jersey Medical School, Wayne, NJ. 30Orthopedic Center of South Florida, Plantation, FL. 31Hospital General Universitario Gregorio Marañon, Madrid, Spain. 32Department for Traumatology and Orthopedic, Clinical Hospital Dubrava, Zagreb, Croatia. 33Orthopedics Department, Complejo Hospitalario Universitario de Albacete, Albacete, Spain. 34Sanatorio Allende, Córdoba, Argentina. 35Apollo Hospitals Bangalore, Karnataka, India. 36Hraia L.G. Rotary Hospital Vapi, Gujarat, India. 37Grange University Hospital, Newport, United Kingdom. 38Manipal Teaching Hospital, Pokhara, Nepal.39Tel Aviv University, Orthopedic Surgery Department, Wolfson Medical Center, Holon, Israel. 40Neurosurgery, Tanta University, Egypt. 41Imperial College London, London, United Kingdom. 42Department of Spine Surgery, Mallika Spine Centre, Guntur, AP, India. 43Department of Orthopedics, All India Institute of Medical Sciences, New Delhi, India. 44Estado de México University, Toluca de Lerdo, Mexico State, Mexico. 45Hospital General Roca, Río Negro, Argentina. 46Devadoss Multispeciality Hospital, Surveyor Colony, Madurai, Tamilnadu, India. 47Rashid Hospital, Dubai, United Arab Emirates. 48ZimSpine, Harare, Zimbabwe. 49Department of Orthopedic, Hospital Tuanku Ja’afar Seremban, Negeri Sembilan, Malaysia. 50Apollo Hospitals, Chennai, India. 51Hospital de Trauma y Ortopedia Lomas Verdes, Hospital Médica Sur, Mexico. 52University Clinical Center, Department of Traumatology, Skopje, Macedonia. 53Hospital Universitario Cajuru, Monterrey, Mexico. 54Department of Neurology, NYU Grossman School of Medicine, New York, NY. 55Hospital Italiano de Buenos Aires, Buenos Aires, Argentina.56 Hospital General de Agudos: “Cosme Argerich” CABA, Buenos Aires, Argentina. 57Orthopedics and Traumatology, Federal University of Juiz de Fora, Juiz de Fora, Brazil. 58Neurosurgery Department, ARNAS Civico Di Cristina Benfratelli Hospital, Palermo, Italy. 59Neurosurgery Department Fernández Hospital, School of Medicine, Universidad de Buenos Aires, Buenos Aires, Argentina. 60Department for Orthopedics and Traumatology, Medical University Graz, Graz, Austria. 61Division of Spine Surgery, Mayo Clinic, Rochester, MN. 62College of Medicine, University of the Philippines, Manila, Philippines. 63Instituto Mexicano del Seguro Socia, Cuauhtémoc, Mexico. 64Centro Médico Integral Fitz Roy, Buenos Aires, Argentina. 65Columbia Asia Hospital Tebrau Johor Bharu Malaysia, Hospital Sultanah Aminah, Johor Bharu, Malaysia. 66Fez Teaching University Hospital, Fez, Morocco. 67Hospital Zonal General de Agudos Dr. Ricardo Gutiérrez de La Plata, Buenos Aires, Argentina. 68Erasmus MC/University Medical Center Rotterdam, Department of Orthopedic Surgery and Sport Medicine, Rotterdam, The Netherlands. 69Departments of Neurological and Orthopedic Surgery, Thomas Jefferson University, Philadelphia, PA. 70ABC Medical Center, Mexico City, Mexico. 71Indian Spinal Injuries Center, Vasantkunj, New Delhi, India. 72Spine and Orthopedics Cebu, Cebu City, Philippines. 73Neurological Institute of Curitiba, Parana, Curitiba, Brazil. 74Addenbrooke’s Hospital, Cambridge University Hospitals Foundation Trust, Cambridge, United Kingdom. 75Department of Orthopedic Surgery, Singapore General Hospital, Singapore. 76Klinikum Wels-Grieskirchen, Department of Trauma Surgery, Wels, Austria. 77Clinica Palermo, Bogoty D.C., Colombia. 78Centro Hospitalar Tondela, Viseu, Portugal. 79Hospital Universitário Cajuru, Curitiba, Brazil. 80Rothman Orthopedic Institute, Paramus, NJ, and Hackensack Meridian School of Medicine, Hackensack, NJ. 81Neurosurgery Department, UZ Brussel, Brussels, Belgium. 82Hospital Las Higueras, Talcahuano, Chile. 8312 de Octubre University Hospital, Madrid, Spain. 84Clínica Alta Complejidad, Cesar, Colombia. 85Hospital Parque, Santa Cruz de Tenerife, Spain. 86Hospital Virgen del Roció, Neurosurgery Department, Sevilla, Spain. 87Özel Ankara Umut Hastanesi, Ankara, Turkey. 88Icahn School of Medicine at Mount Sinai, NY. 89Faculty of Medicine, School of Health Sciences, University of Thessaly, Larissa, Greece. 90Edgardo Rebagliati Martins National Hospital, Lima, Perú. 91Department of Orthopedic Surgery, Ninth People’s Hospital of Shanghai Jiao Tong University School of Medicine, Shanghai, China. 92Westbay Medicare Hospital, Doha, Qatar.93“Lomas Verdes” Traumatology and Orthopedic Hospital, Nacozari de García, Mexico. 94Faculty of Medicine, Tanta University, Tanta, Egypt. 95Universitary Hospitalary Complex Santiago de Compostela, University of Santiago de Compostela, Galicia, Spain. 96Department of Neurosurgery, University Central Hospital of Asturias, Asturias, Spain. 97Neurosurgery Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico Milano, Milan, Italy. 98Hospital Italiano, Caba, Argentina. 99Orthopedic Department, Hospital Churruca Visca, Buenos Aires, Argentina. 100Department of Neurosurgery, Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom. 101Nottingham University Hospitals NHS, Nottingham, United Kingdom. 102Neurological Diseases Center, Public University of El Alto, La Paz, Bolivia. 103Department of Orthopedic Surgery, Akita University Graduate School of Medicine, Akita, Japan. 104Austrian Spine and Orthopedics Center, Vienna, Austria. 105Ain Shams University, Cario, Egypt. 106The Queen Elizabeth Hospital, St. Michael, Barbados. 107Moi County Hospital, Mombasa, Kenya. 108Hospital Alvarez Teodoro, Buenos Aires, Argentina. 109Ospedale Bufalini–Cesena, Cesena, Italy. 110Orthopedic Department, Centro Hospitalar e Universitário de São João, Porto, Portugal. 111Department of Orthopedic Surgery, Postgrado de Cirugía de Columna, Hospital Universitario Maturin, Monagas, Venezuela. 112Hospital Italiano La Plata, Buenos Aires, Argentina. 113Centro Hospitalar Universitário São João, Faculty of Medicine of the University of Porto, Porto, Portugal. 114Rumah Sakit Umum Pusat Fatmawati, South Jakarta, Indonesia. 115Department of Neurosurgery, University of Alabama at Birmingham, Birmingham, AL. 116Department of Neurosurgery, University of Aberdeen, Aberdeen, Scotland, United Kingdom. 117Department of Orthopedics, Kasturba Medical College and Hospital, Manipal, India. 118Ortopedia e Traumatologia, Cururgia da Coluna Vertebral, Centro, Ribeirão Preto, SP, Brazil. 119Spinal Unit/Unidade Vertebro-Medular, Department of Orthopedics, Centro Hospitalar Universitario do Porto, Porto, Portugal. 120American Neurospine Institute, Plano, TX. 121Clínica Universidad de Navarra, Pamplona, Spain. 122Santa Casa de Itapeva, São Paulo, Brazil. 123Hospital Gracia de Orta, Almada, Portugal. 124University del Desarrollo (UDD), Clinica Alemana de Santiago, Vitacura, Región Metropolitana, Chile. 125Department of Orthopedics, Centro Hospitalar Universitário do Porto, Porto, Portugal. 126Department of Orthopedics, Walter Reed National Military Medical Center, Bethesda, MD. 127Hospital Santa Isabel de Hungría de Mendoza, Medoza, Argentina. 128Apollo Specialty Hospital, Chennai, India. 129Department of Orthopedic and Traumatology, Medical Park Hospital, Gebze, Kocaeli, Turkey. 130Artemis Hospital Gurgaon, Haryana, India. 131Buckinghamshire Healthcare NHS Trust, Amersham, United Kingdom. 132Orthopedic and Trauma Surgery Department, Faculty of Medicine, Assiut University, Assiut, Egypt. 133Division of Spine Surgery, Department of Orthopedic Surgery, Japanese Red Cross Maebashi Hospital, Tokyo, Japan. 134University Hospital Centre Sestre milosrdnice, Zagreb, Croatia. 135Division of Neurosurgery, The Centre hospitalier de l’Université de Montréal, Montreal, QC, Canada. 136Zerktouni Ortho Clinic, Casablanca, Morocco. 137Faculty of Medicine, Zagazig University, Zagazig, Egypt. 138Maulana Azad Medical College, New Delhi, India. 139Mater Private Hospital, Dublin, Ireland. 140National Orthopedic Hospital, Lagos, Nigeria. 141Neurosurgery, Santiago de Chile, Chile. 142Rehman Medical Institute, Hayatabad Peshawar, KP, Pakistan. 143Lady Reading Hospital Peshawar, Khyber Pakhthoon Khwa, Pakistan. 144Gothenburg University, Institute of Clinical Sciences, Gothenburg, Sweden. 145NYC Health + Hospitals/Elmhurst, Icahn School of Medicine, Mount Sinai, NY. 146Universiti Malaysia, Sarawak, Malaysia. 147Hospital Dr. Víctor Ríos Ruiz, Los Ángeles, Bío Bío, Chile. 148Spine Surgery Department, University Hospital Motol, Praha, Czech Republic.

Disclosures

This study was organized and funded by AO Spine through AO Spine Knowledge Forum Trauma, a focused group of international trauma experts. AO Spine is a clinical division of the AO Foundation, which is an independent, medically guided, not-for-profit organization. Study support was provided directly through the AO Spine Research Department. Dr. Schnake receives honoraria from AO Spine International. Dr. Schroeder is a consultant for Medtronic, Stryker, Zimmer, Bioventus, AO Spine, ISD, WK, and Teledoc. Dr. Vaccaro owns stock in Advanced Spinal Intellectual Properties, Atlas Spine, Avaz Surgical, Bonovo Orthopaedics, Cytonics, Deep Health, Dimension Orthotics LLC, Electrocore, Flagship Surgical, FlowPharma, Globus, Innovative Surgical Design, Insight Therapeutics, Jushi, NuVasive, Orthobullets, Paradigm Spine, Parvizi Surgical Innovation, Progressive Spinal Technologies, Replication Medica, Spine Medica, Spinology, Stout Medical, Vertiflex, and ViewFi Health; receives royalties from Aesculap, Atlas Spine, Globus, Medtronic, SpineWave, and Stryker Spine; and works as an independent contractor for AO Spine.

Author Contributions

Conception and design: Tee, Kweh, Muijs, Schroeder, Vaccaro. Acquisition of data: Tee, Kweh, Schroeder, Vaccaro. Analysis and interpretation of data: Tee, Kweh. Drafting the article: Tee, Kweh. Critically revising the article: all authors. Reviewed submitted version of manuscript: Tee, Kweh. Approved the final version of the manuscript on behalf of all authors: Tee. Statistical analysis: Tee, Kweh. Administrative/technical/material support: Tee, Kweh.

Supplemental Information

Online-Only Content

Supplemental material is available with the online version of the article.

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    • Search Google Scholar
    • Export Citation
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Supplementary Materials

Illustrations from Hubbe et al. (pp 160–163). Copyright Ioannis Vasilikos and Roberto Ferrarese. Published with permission.

  • View in gallery

    A3 incomplete burst fracture involves a single endplate, whereas A4 complete burst fracture involves both endplates.11 Copyright AO Spine, AO Foundation. Published with permission. Figure is available in color online only.

  • 1

    Goldberg W, Mueller C, Panacek E, et al. Distribution and patterns of blunt traumatic cervical spine injury. Ann Emerg Med. 2001;38(1):1721.

  • 2

    Aebi M. Surgical treatment of upper, middle and lower cervical injuries and non-unions by anterior procedures. Eur Spine J. 2010;19(1)(suppl 1):S33S39.

  • 3

    Torretti JA, Sengupta DK. Cervical spine trauma. Indian J Orthop. 2007;41(4):255267.

  • 4

    Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine (Phila Pa 1976).2007;32(21):23652374.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5

    Harris JH Jr, Edeiken-Monroe B, Kopaniky DR. A practical classification of acute cervical spine injuries. Orthop Clin North Am. 1986;17(1):1530.

  • 6

    Allen BL Jr, Ferguson RL, Lehmann TR, O’Brien RP. A mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine. Spine (Phila Pa 1976).1982;7(1):127.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7

    Glaser JA, Jaworski BA, Cuddy BG, et al. Variation in surgical opinion regarding management of selected cervical spine injuries. A preliminary study. Spine (Phila Pa 1976).1998;23(9):975983.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8

    Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J. 2016;25(7):21732184.

  • 9

    Dvorak MF, Fisher CG, Fehlings MG, et al. The surgical approach to subaxial cervical spine injuries: an evidence-based algorithm based on the SLIC classification system. Spine (Phila Pa 1976).2007;32(23):26202629.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10

    Whang PG, Patel AA, Vaccaro AR. The development and evaluation of the subaxial injury classification scoring system for cervical spine trauma. Clin Orthop Relat Res. 2011;469(3):723731.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    AO Spine. AO Spine Injury Classification Systems. Accessed April 26, 2021. www.aospine.org/classification

  • 12

    Mayhew D, Mendonca V, Murthy BVS. A review of ASA physical status—historical perspectives and modern developments. Anaesthesia. 2019;74(3):373379.

  • 13

    Leucht P, Fischer K, Muhr G, Mueller EJ. Epidemiology of traumatic spine fractures. Injury. 2009;40(2):166172.

  • 14

    Feuchtbaum E, Buchowski J, Zebala L. Subaxial cervical spine trauma. Curr Rev Musculoskelet Med. 2016;9(4):496504.

  • 15

    Miller CP, Golinvaux NS, Brubacher JW, et al. Mortality rates associated with odontoid and subaxial cervical spine fractures. Am J Orthop. 2015;44(6):E173E179.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Sokolowski MJ, Jackson AP, Haak MH, et al. Acute mortality and complications of cervical spine injuries in the elderly at a single tertiary care center. J Spinal Disord Tech. 2007;20(5):352356.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17

    Urrutia J, Zamora T, Campos M, et al. A comparative agreement evaluation of two subaxial cervical spine injury classification systems: the AOSpine and the Allen and Ferguson schemes. Eur Spine J. 2016;25(7):21852192.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Silva OT, Sabba MF, Lira HIG, et al. Evaluation of the reliability and validity of the newer AOSpine subaxial cervical injury classification (C-3 to C-7). J Neurosurg Spine. 2016;25(3):303308.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Hitti FL, McShane BJ, Yang AI, et al. Predictors of failure of nonoperative management following subaxial spine trauma and creation of modified subaxial injury classification system. World Neurosurg. 2019;122:e1359e1364.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    van Middendorp JJ, Audigé L, Hanson B, et al. What should an ideal spinal injury classification system consist of? A methodological review and conceptual proposal for future classifications. Eur Spine J. 2010;19(8):12381249.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 21

    Koivikko MP, Myllynen P, Karjalainen M, et al. Conservative and operative treatment in cervical burst fractures. Arch Orthop Trauma Surg. 2000;120(7-8):448451.

  • 22

    Steinmetz MP, Miller J, Warbel A, et al. Regional instability following cervicothoracic junction surgery. J Neurosurg Spine. 2006;4(4):278284.

  • 23

    Yu Y, Li JS, Guo T, et al. Normal intervertebral segment rotation of the subaxial cervical spine: an in vivo study of dynamic neck motions. J Orthop Translat. 2019;18:3239.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24

    Fredø HL, Rizvi SAM, Lied B, et al. The epidemiology of traumatic cervical spine fractures: a prospective population study from Norway. Scand J Trauma Resusc Emerg Med. 2012;20(1):85.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 25

    Kwon BK, Vaccaro AR, Grauer JN, et al. Subaxial cervical spine trauma. J Am Acad Orthop Surg. 2006;14(2):7889.

  • 26

    Quarrington RD, Jones CF, Tcherveniakov P, et al. Traumatic subaxial cervical facet subluxation and dislocation: epidemiology, radiographic analyses, and risk factors for spinal cord injury. Spine J. 2018;18(3):387398.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27

    Schleicher P, Kobbe P, Kandziora F, et al. Treatment of injuries to the subaxial cervical spine: recommendations of the spine section of the German Society for Orthopaedics and Trauma (DGOU). Global Spine J. 2018;8(2)(suppl):25S33S.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 28

    Toh E, Nomura T, Watanabe M, Mochida J. Surgical treatment for injuries of the middle and lower cervical spine. Int Orthop. 2006;30(1):5458.

  • 29

    Fisher CG, Dvorak MF, Leith J, Wing PC. Comparison of outcomes for unstable lower cervical flexion teardrop fractures managed with halo thoracic vest versus anterior corpectomy and plating. Spine (Phila Pa 1976).2002;27(2):160166.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 30

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