Transverse Atlantal Ligament Injury Research Articles

Interrelationship Between Craniocervical Dissociation Spectrum Injuries and Atlantoaxial Instability on Trauma Cervical MRI Examinations.

Background and purpose Craniocervical dissociation injuries encompass a spectrum of osteoligamentous injuries between the skull base and C1-C2 that may be treated via prolonged external immobilization versus occipital cervical fusion depending on the risk of persistent craniocervical instability. However, the presence of atlantoaxial instability (AAI) at C1-C2, as determined by transverse atlantal ligament (TAL) integrity with or without a C1 fracture, may guide the neurosurgical management of craniocervical dissociation spectrum injuries (CDSI) since it implies an overall greater degree of instability at the craniocervical junction (CCJ). Materials and methods Adult trauma patients who suffered a transverse atlantal ligament injury on cervical magnetic resonance imaging (MRI) were identified retrospectively. The cervical computed tomography (CT) and magnetic resonance imaging examinations for these patients were reviewed for additional traumatic findings. Demographic information, treatment, and outcome information were recorded. Results Twenty-nine trauma patients presented to the emergency department (ED) with an acute, midsubstancetransverse atlantal ligament tear on cervical magnetic resonance imaging. Thirty-one percent of patients demonstrated a tear in at least one major craniocervical ligament (atlanto-occipital capsular ligaments, alar ligaments, and tectorial membrane {TM}) with 14% demonstrating a tear in two major craniocervical ligamentsand no patients demonstrating a tear in all three major craniocervical ligaments. Minor craniocervical ligament injuries (anterioratlanto-occipital membrane complex {AAOMc} and posterior atlanto-occipital membrane complex {PAOMc}) were common and observed in 76% of patients. Conclusions Our study suggests that multiple major craniocervical junction ligamentous injuries on cervical magnetic resonance imaging are relatively uncommon in the setting of transverse atlantal ligament injury.

Risk Factors for Fracture Nonunion and Transverse Atlantal Ligament Injury After Isolated Atlas Fractures: A Case Series of 97 Patients.

The management of atlas fractures is controversial and hinges on the integrity of transverse atlantal ligament (TAL). To identify risk factors for atlas fracture nonunion, with and without TAL injury. All isolated, traumatic atlas fractures treated at our institution between 1999 and 2016 were analyzed. Multivariable logistic regression was used to identify variables associated with TAL injury confirmed on MRI, occult TAL injury seen on MRI but not suspected on computed tomography (CT), and with fracture nonunion on follow-up CT at 12 weeks. Lateral mass displacement (LMD) ≥ 7 mm had a 48.2% sensitivity, 98.3% specificity, and 82.6% accuracy for identifying TAL injury. MRI-confirmed TAL injury was independently associated with LMD > 7 mm ( P = .004) and atlanto-dental interval ( P = .039), and occult TAL injury was associated with atlanto-dental interval ( P = .019). Halo immobilization was associated with having a Gehweiler type 3 fracture ( P = .020), a high-risk injury mechanism ( P = .023), and an 18.1% complication rate. Thirteen patients with TAL injury on MRI and/or LMD ≥ 7 mm were treated with a cervical collar only, and 11 patients (84.6%) healed at 12 weeks. Nonunion rates at 12 weeks were equivalent between halo (11.1%) and cervical collar (12.5%). Only age independently predicted nonunion at 12 weeks ( P = .026). LMD > 7 mm on CT is not sensitive for TAL injury. Some atlas fractures with TAL injury can be managed with a cervical collar. Nonunion rates are not different between halo immobilization and cervical collar, but a strong selection bias precludes directly comparing the efficacy of these modalities. Age independently predicts nonunion.

Appropriateness of Cervical Magnetic Resonance Imaging in the Evaluation and Management of C1 Jefferson Fractures

Traditionally, C1 fractures have been designated as stable or unstable based on the inherent integrity of the transverse altantal ligament. The purpose of our study was to identify adult trauma patients with C1 fractures on cervical computed tomography and evaluate whether C1-C2 alignment differed in patients with and without an associated transverse atlantal ligament injury on follow-up cervical magnetic resonance imaging. Adult trauma patients who suffered a C1 fracture were identified retrospectively. The cervical computed tomography examinations for these patients were reviewed for the following: C1 fracture classification, anterior atlantodens interval (ADI) widening, asymmetry in the lateral atlantodens interval, C1 lateral mass offset, and atlantoaxial rotation. Acute C1 fractures were grouped into those with an unequivocal transverse atlantal ligament injury (n= 12), and patients with an unequivocally intact transverse atlantal ligament (n= 20). Three patients were classified as indeterminate for transverse atlantal ligament injury. Statistically significant increases in lateral ADI asymmetry and combined C1 lateral mass offset were identified in patients with transverse atlantal ligament tears. Lateral ADI asymmetry (using a cutoff of >3 mm), combined C1 lateral mass offset, and anterior ADI demonstrate robust specificity to "rule in" transverse atlantal ligament injury. Atlantoaxial alignment was overall relatively insensitive as a screening test although sensitivity can be improved using a cutoff of >2 mm for lateral ADI asymmetry. Our findings reinforce the role of cervical magnetic resonance imaging in the diagnostic workup and clinical management of trauma patients with an acute burst fracture of the C1 vertebra.

Fifty years later: the "rule of Spence" is finally ready for retirement.

Determination of the optimal approach to traumatic atlas fractures with or without transverse atlantal ligament (TAL) injury requires a nuanced understanding of the biomechanics of the atlantoaxial complex. The "rule of Spence" (ROS) was created in 1970 in a landmark effort to streamline management of burst-type atlas fractures. The ROS states that radiographic evidence of lateral mass displacement (LMD) (i.e., the distance that the C1 lateral masses extend beyond the C2 superior articular processes) greater than 6.9 mm may indicate both a torn TAL and need for surgical management. Since then, the ROS has become ubiquitous in the spine literature about atlas injuries. However, in the decades since the original paper by Spence et al., modern research efforts and imaging advancements have revealed that the ROS is inaccurate on both fronts: it neither accurately predicts a TAL injury nor does it inform surgical decision-making. The purpose of this review was to delineate the history of the ROS, demonstrate its limitations, present findings in the existing literature on ROS and LMD thresholds, and discuss the current landscape of management techniques for TAL injuries, including parameters such as the atlantodental interval and type of injury according to the Dickman classification system and AO Spine upper cervical injury classification system. The ROS was revolutionary for initially investigating and later propelling the biomechanical and clinical understanding of atlas fractures and TAL injuries; however, it is time to retire its legacy as a rule.

Utility of Anterior Atlantodens Interval Widening on Cervical Spine CT for Assessing Transverse Atlantal Ligament Injury.

Retrospective, cross-sectional. To identify trauma patients with confirmed tears of the transverse atlantal ligament on cervical MRI and measure several parameters of atlanto-axial alignment on cervical CT, including the anterior atlantodens interval, to determine which method is most sensitive in predicting transverse atlantal ligament injury. Adult trauma patients who suffered a transverse atlantal ligament tear on cervical MRI were identified retrospectively. The cervical CT and MRI exams for these patients were reviewed for the following: anterior and lateral atlantodens interval widening, lateral C1 mass offset, C1-C2 rotatory subluxation, and transverse atlantal ligament injuries on cervical MRI. Twenty-six patients were identified with a tear of the transverse atlantal ligament on cervical MRI. Twelve percent of these patients demonstrated an anterior dens interval measuring greater than 2mm, 26% of patients demonstrated lateral mass offset of C1 on C2 (average offset of 2.4mm), 18% of patients demonstrated an asymmetry greater than 1mm between the left and right lateral atlantodens interval, and one patient demonstrated atlanto-axial rotation measuring greater than 20%. Ten patients had an accompanying C1 burst fracture and eight patients had a C2 fracture. One patient demonstrated widening of the atlanto-occipital joint space greater than 2mm indicative of craniocervical dissociation injury. An anterior atlantodens interval measuring greater than 2mm is an unreliable methodology to screen trauma patients for transverse altantal ligament injuries and atlanto-axial instability. Moreover, C1 lateral mass offset, lateral atlantodens asymmetry, and atlanto-axial rotation were all poor predictors of transverse atlantal ligament tears.

Radiologic utility of the Gehweiler and AO spine classification systems for C1 Trauma: A retrospective review from a Level I trauma center.

The purpose of our study was to identify adult trauma patients with an acute C1 burst fracture, evaluate for concomitant transverse atlantal ligament (TAL) injury, and apply the modified Gehweiler and AO spine classification systems to determine the utility of these classification systems in accurately defining C1 trauma. Adult trauma patients with an acute C1 fracture were identified retrospectively using Nuance mPower software. The C1 fracture was described based on whether the fracture involved the anterior arch, posterior arch, lateral mass, medial tubercle, and/or transverse process. If follow-up cervical magnetic resonance imaging (MRI) was performed, the presence and location of an associated TAL injury was recorded. The anatomic location of the C1 burst fracture and TAL injury, if present, were compared with the descriptive classification systems outlined by Gehweiler/Dickman (modified) and the AO Spine society. Any additional osseous trauma of the skull base and C1-C2 was also recorded along with relevant clinical history and management. Thirty-nine patients were identified with an acute C1 burst fracture on cervical computed tomography (CT) with seventy-seven percent of patients undergoing follow-up cervical MRI. Observed fracture patterns were divided into five distinct types based on CT findings and further subdivided based on the integrity of the transverse altantal ligament on MRI. TAL tears were observed exclusively in type 3 fractures (anterior and posterior arch fractures) and type 4 fractures (anterior arch, posterior arch, and lateral mass fractures). The modified Gehweiler classification system failed to accurately describe the anatomic location of the C1 fracture in forty-four percent of patients, whereas the AO spine was too broad and failed to accurately describe fracture location in our cohort. The Gehweiler and AO spine classifications demonstrated significant shortcomings in the accurate description of patients with C1 trauma. Whereas the Gehweiler system did not accurately describe the anatomic location of the various C1 fractures, the AO spine system was too broad and failed to radiologically classify fracture location. Moreover, there was a high number of patients with AO spine type B injuries without atlantoaxial translation that nevertheless required C1-C2 fusion for atlantoaxial instability. We suggest the need for an updated classification system that takes into account both the CT (fracture location) and MRI (TAL integrity) appearance of C1 trauma. An updated classification strategy will offer a radiologic standardization of C1 trauma that will aid in future research studies and help optimize patient management.

Diagnosis and management of isolated C1 fractures: A systematic review.

ObjectiveAtlas fractures are a common craniocervical injury, often resulting from trauma. However, diagnosis and management of atlas fractures continues to be the subject of controversy. We aimed to characterize the factors related to diagnosis of atlas fractures, delineate important considerations in selecting the optimal management for a patient with an atlas fracture, and compare outcomes of surgical and conservative management.Methods:We performed a systematic review using PubMed, Embase, and Scopus to identify articles that analyzed diagnosis and management of isolated atlas fractures published between 2013 and 2020. Titles and abstracts were screened. Studies meeting prespecified inclusion criteria were reviewed in full.Results:Of 305 resultant articles, 13 were included. C1:C2 ratio and lateral mass displacement (LMD) were used to predict transverse atlantal ligament (TAL) injury. Surgery promoted high fusion rates overall. Stable atlas fractures achieved high fusion rates with conservative management, while spinal fusion promoted greater fusion rates than halo vest immobilization management for unstable fractures. Visual Analog Scale scores, range of motion, and/or LMD improved after surgery. LMD increased for unilateral sagittal split fractures with TAL injury after conservative treatment.Conclusion:Stable atlas fractures can be sufficiently treated conservatively. Unstable atlas fractures can be managed both conservatively and surgically, while surgery is associated with favorable outcomes for unstable isolated atlas fractures. Future studies are necessary to further guide risk stratification and treatment approaches in management of the patients with isolated atlas fractures.

Direct Internal Fixation for Unstable Atlas Fractures.

PurposeTo investigate the radiologic and clinical outcomes of direct internal fixation for unstable atlas fractures.Materials and MethodsThis retrospective study included 12 patients with unstable atlas fractures surgically treated using C1 lateral mass screws, rods, and transverse connector constructs. Nine lateral mass fractures with transverse atlantal ligament (TAL) avulsion injury and three 4-part fractures with TAL injury (two avulsion injuries, one TAL substance tear) were treated. Radiologic outcomes included the anterior atlantodental interval (AADI) in flexion and extension cervical spine lateral radiographs at 6 months and 1 year after treatment. CT was also performed to visualize bony healing of the atlas at 6 months and 1 year. Visual Analog Scale (VAS) scores for neck pain, Neck Disability Index (NDI) values, and cervical range of motion (flexion, extension, and rotation) were recorded at 6 months after surgery.ResultsThe mean postoperative extension and flexion AADIs were 3.79±1.56 (mean±SD) and 3.13±1.01 mm, respectively. Then mean AADI was 3.42±1.34 and 3.33±1.24 mm at 6 months and 1 year after surgery, respectively. At 1 year after surgery, 11 patients showed bony healing of the atlas on CT images. Only one patient underwent revision surgery 8 months after primary surgery due to nonunion and instability findings. The mean VAS score for neck pain was 0.92±0.99, and the mean NDI value was 8.08±5.70.ConclusionC1 motion-preserving direct internal fixation technique results in good reduction and stabilization of unstable atlas fractures. This technique allows for the preservation of craniocervical and atlantoaxial motion.

The relationship between radiologic parameters and transverse atlantal ligament injury obtained from MRI scans in patients with an isolated atlas burst fracture: A retrospective observational study.

The treatment of an atlas burst fracture depends on whether transverse atlantal ligament (TAL) injury is present. We compared the radiologic parameters associated with the presence of a TAL injury as detected using magnetic resonance imaging (MRI), and verified whether the lateral mass displacement (LMD) criteria currently used to diagnose TAL injuries in atlas burst fractures are reliable or need revision.Thirty patients who presented with isolated atlas burst fractures were included in this retrospective observational study. We measured radiologic parameters, including LMD, atlanto-dental interval, basion-dens interval, internal lateral mass displacement, and external lateral mass displacement, in each patient at the time of initial presentation. The presence of TAL injury was evaluated using MRI. We compared the radiologic parameters and characteristics of patients who presented with TAL injury. We also determined the sensitivity and specificity of an LMD test to accurately diagnose TAL injury based on MRI. Finally, we compared the radiologic parameters according to the presence of surgical treatment and patient union status.Twenty patients presented with an intact TAL, while 10 patients had a TAL injury on MRI. LMD was significantly higher in patients with TAL injury (9.61 vs 3.73 mm, P < .001). In multivariable logistic regression analysis, LMD was also significantly higher in patients with TAL injury. The sensitivity and specificity of LMD for diagnosing TAL injury based on MRI in patients with isolated C1 fractures were 90% and 100%, respectively. The incidence of an LMD greater than 8.1 mm was statistically higher in patients than in those without TAL injury (90% vs 0%, P < .001).Nine patients underwent surgery for isolated atlas burst fractures, and 21 did not. LMD (9.56 vs 4.03 mm, P < .001) and fracture gap (7.96 vs 4.01 mm, P < .001) were significantly higher in patients who underwent surgery.Among the various radiologic parameters, LMD closely correlated with the presence of TAL injury, as patients with an LMD greater than 8.1 mm were more likely to have a TAL injury in the case of atlas burst fractures. LMD is a good method for predicting the presence of TAL injury if MRI is not available.

Anterior reduction and C1-ring osteosynthesis with Jefferson-fracture reduction plate (JeRP) via transoral approach for unstable atlas fractures

BackgroundTo introduce a novel transoral instrumentation in the treatment of unstable fractures of the atlas.MethodsFrom January 2008 to May 2018, 22 patients with unstable C1 fractures who received Jefferson-fracture reduction plate (JeRP) via transoral approach were retrospectively analyzed. The case history and the radiographs before and after surgery were noted. The type of fracture, the reduction of the fracture, and position of the internal fixation were assessed through preoperative and postoperative CT scans.ResultsAll 22 patients successfully underwent anterior C1-ring osteosynthesis using the JeRP system, with a follow-up of 26.84 ± 9.23 months. Among them, 9 patients had transverse atlantal ligament (TAL) injury, including 3 in Dickman type I and 6 in type II. The preoperative lateral mass displacement (LMD) decreased from 7.13 ± 1.46 mm to 1.02 ± 0.65 mm after the operation. Bone union was achieved in all patients without implant failure or loss of reduction. There were no surgery-related complications, such as wound infection, neurological deficit, or vertebral artery injury. However, atlantoaxial dislocation occurred in 3 patients with Dickman type I TAL injury 3 months postoperatively without any neurological symptoms or neck pain.ConclusionsTransoral C1-ring osteosynthesis with JeRP is an effective surgical strategy to treat unstable atlas fractures with a safe, direct, and satisfactory reduction. The primary indication for the JeRP system is an unstable fracture (Gehweiler type I/III) or/ and TAL injury (Dickman type II).

Evaluation of Different Techniques in the Management of Craniocervical Instability

Objectives: Evaluation of clinical picture and results of occipitocervical and atlanto-axial fusion with craniocervical instabilities Patients and Method: The investigation included 22 patients, 14 males (63.6%) and 8 females (36.4%). Ages ranged (10 to 70) years. Instability resulted fromfracture of the odontoid process in 8 cases(36.4%), transverse atlantal ligament injury with C1 C2 sub laxation in 6 cases(27.3%), osodontodium in 4 cases(18.2%), Morquio’s syndrome in 2 cases(9%) , C2 Hangman’s fracture type III one case(4.5%), and transverse atlantal ligament injury associated with sub axial sublaxation in one case(4.5%). Trauma was the most common cause of instability (73%).Single hollow titanium anterior odontoid screw was done in 4 cases (18,2%), posterior atlanto-axial fixation in 12 patients(54.5%) three of them (25%) needed trans oral odontoidectomy prior to fixation, fixation was performed from C1to C4 in one patient(4.5%) , and occipitocervical fixation in 5 patients(22.7%). Postoperative Philadelphia neck collar was applied for 8-12 weeks. Results: Postoperative clinical evaluation revealed good outcome of neurological ASIA grading. 10 patients improved (45.5%), while 11 patients (50%) remained at the same ASIA score as pre-operative, and only one patient (4.5%) deteriorated from ASIA score D to A. Pain and neck disability scores reduced postoperatively compared to preoperative. Fusion was achieved in 18 cases (81.8%) at last follow-up. Instrumentation failure occurred in only 2 cases (9%). Three mortality cases due to respiratory problems (2cases died in the first week after surgery and the third case died one month after the surgery).

Clinical and radiological outcomes of conservative treatment for unilateral sagittal split fractures of C1 lateral mass

ObjectiveThe aim of this study was to assess the effect of transverse atlantal ligament (TAL) integrity on clinical and radiological outcomes in patients with unilateral sagittal split fracture (USSF) of the C1 lateral mass (LM). MethodsTwenty-six consecutive patients (16 men and 10 women; mean age: 52 years (range: 32–69)) with C1 LM USSF were included in this study. Sixteen were TAL injury group (nine of type I injuries and seven of type II injuries according to Dickman's classification) and ten were TAL intact group. All cases were conservatively treated with a rigid brace for TAL intact or by halo-vest stabilization for TAL injury for three months. The mean follow-up was 16 months (range, 12–47 months). The results were compared with radiological assessment of fracture healing, LM displacement and Neck visual analog scale. ResultsAt the last follow-up, for TAL intact group, total LM displacement (LMD), unilateral LMD of fracture side, atlanto-dental interval, basion-dental interval, clivus canal angle, and atlanto-occipital joint axis angle were maintained compared to initial presentation. However, for TAL injury group, all radiological parameters were worsened. The worsening of radiological parameters was more severe in type I injury than type II injury except for total LMD and unilateral LMD. Neck visual analog scale significantly decreased and patient's satisfaction was higher in TAL intact group compared to TAL injury group. ConclusionConservative treatment for USSF of C1 LM with TAL injury failed to achieve healing of the fracture, which resulted in lateral displacement of C1 LM. This caused coronal and sagittal malalignment of occipitocervical junction, resulting in unsatisfactory clinical outcomes. Our results suggest that early surgical stabilization should be considered in USSF of C1 LM with TAL injury, especially type I injury. However, conservative treatment may be sufficient for a USSF of the C1 LM with TAL intact. Level of EvidenceLevel III, Therapeutic Study.

Radiologic criteria to predict injury of the transverse atlantal ligament in unilateral sagittal split fractures of the C1 lateral mass.

Unilateral sagittal split fracture (USSF) of the C1 lateral mass (LM) has been recently recognized as a rare variant of C1 atlas fracture. To date, there has been no study to investigate whether radiologic criteria can be applied to determine the presence or absence of transverse atlantal ligament (TAL) injury in USSF of the C1 LM.Twenty six consecutive cases of USSF of the C1 LM were included in this study. According to Dickman classification, 16 cases were TAL injury, and 10 cases were TAL intact. Radiologic parameters were measured and compared between the 2 groups.Total LM displacement (LMD) of the 2 sides (5.9 ± 2.0 mm vs 1.2 ± 2.0 mm), unilateral LMD of the fracture side (4.3 ± 1.2 mm vs 1.0 ± 1.1 mm), atlanto-dental interval (ADI) (2.0 ± 0.9 mm vs 1.5 ± 0.4 mm), and fracture gap (6.9 ± 2.7 mm vs 2.1 ± 1.1 mm) were statistically higher in the TAL injury group than the TAL intact group. However, basion-dental interval, clivus canal angle, and atlanto-occipital joint axis angle were not different between the 2 groups. Total LMD and unilateral LMD positively correlated with ADI and fracture gap. The incidence of fracture gap larger than 7 mm was statistically higher in the TAL injury group than the TAL intact group (81% vs 30%).In conclusion, total LMD > 5.9 mm or unilateral LMD > 4.3 mm suggests the presence of TAL injury in USSF of the C1 LM. The possibility of diagnostic error for TAL injury can be further reduced in USSF of the C1 LM by considering the fracture gap larger than 7 mm.

163. Is conservative treatment effective for unilateral sagitally split fractures of C1 lateral mass?

BACKGROUND CONTEXT A unilateral sagittal split fracture (USSF) of the C1 lateral mass (LM) is a rare variant of C1 atlas fracture. To date, definite treatment guideline of USSF of C1 LM has not been established. The integrity of transverse atlantal ligament (TAL) is a key factor to determine the stability in C1 atlas fracture. However, the effect of TAL injury on treatment outcomes is controversial in USSF of C1 LM. Previous study of small case series reported that despite the TAL competency, conservatively-treated USSF of C1 LM causes late deformity of occipitocervical junction requiring major reconstructive surgery. PURPOSE Therefore, we performed the current study to investigate these two issues in USSF of C1 LM and suggest appropriate treatment guideline. STUDY DESIGN/SETTING Retrospective case analyses. PATIENT SAMPLE Twenty-six consecutive cases of USSF of C1 LM were included from 5 trauma centers of tertiary university hospitals. The fractures associated with other cervical spines, such as C2 and occiput, were excluded from the study. The mean age was 52 years old; 16 were male and 10 were female. OUTCOME MEASURES The radiologic outcomes were evaluated by comparing initial presentation and last follow-up in two groups. Clinical outcomes were evaluated by visual analog scale (VAS) and Odom's criteria. METHODS Of the total cases,16 were TAL injury group (9 type I and 7 type II according to Dickman's classification) and 10 were TAL intact group. All cases were treated by conservative measures including rigid brace or halovest for 12 weeks. The mean follow-up was 16 months (range, 12-47 months). Three spine surgeons measured radiologic parameters on lateral radiograph and open mouth view of cervical spine, 2-dimensional reconstructed CT scans and MRI of initial and last follow-up: total LM displacement (LMD), unilateral LMD of fracture side, atlanto-dental interval (ADI), clivus canal angle (CCA), atlanto-occipital joint axis angle (AOJAA), and basion-dens interval (BDI). The averages of three measurements were used as final results. RESULTS At the last follow-up, for TAL intact group, total LM displacement (LMD), unilateral LMD of fracture side, atlanto-dental interval, basion-dental interval, clivus canal angle, and atlanto-occipital joint axis angle were maintained compared to initial presentation. However, for TAL injury group, all radiological parameters were worsened. The worsening of radiological parameters was more severe in type I injury than type II injury except for total LMD and unilateral LMD. Neck VAS significantly decreased and patient's satisfaction was higher in TAL intact group compared to TAL injury group. CONCLUSIONS Conservative treatment for USSF of C1 LM with TAL injury failed to achieve healing of fracture site, which caused deterioration of lateral displacement of C1 LM. This caused coronal and sagittal malalignment of occipitocervical junction, resulting in unsatisfactory clinical outcomes. Our results suggest that early surgical treatment should be considered as the first choice treatment for USSF of the C1 LM, especially type I TAL injury. However, conservative treatment may be sufficient for USSF of the C1 LM with TAL intact. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

202. Radiologic criteria to predict injury of transverse atlantal ligament in unilateral sagittally split fracture of C1 lateral mass

BACKGROUND CONTEXT If lateral mass displacement (LMD) exceeds 6.9 mm, burst fracture of the C1 atlas is considered an unstable fracture due to transverse atlantal ligament (TAL) injury. Recently, unilateral sagittal split fracture (USSF) of C1 lateral mass (LM) was recognized as a rare variant of C1 atlas fracture. Conservatively-treated USSF of C1 LM is reported to cause late deformity of occipitocervical junction requiring major reconstructive surgery. Therefore, it is necessary to verify whether such LMD criteria can be applied to determine TAL injury in USSF of C1 LM. PURPOSE We performed the current study to investigate radiologic criteria to predict the presence of injury of TAL in USSF of C1 LM. STUDY DESIGN/SETTING Retrospective case analyses. PATIENT SAMPLE Twenty-six consecutive cases of USSF of C1 LM were included in this study. The fractures associated with other cervical spines, such as C2 and occiput, were excluded from the study. The mean age was 52 years-old; 16 were male and 10 were female. OUTCOME MEASURES Two radiologists determined presence of TAL injury in MRI using Dickman's classification and divided the cases into two groups: TAL injury and TAL intact. If the results of two judgements were not identical, the third radiologist re-evaluated. The radiologic results were measured and compared between TAL intact and TAL injury. METHODS Three spine surgeons measured radiologic parameters and the averages were used as final results: total LMD of both sides, unilateral LMD of the fracture side, atlanto-dental interval (ADI), and fracture gap. Radiologic parameters were measured and compared between TAL injury and TAL intact. RESULTS Sixteen were TAL injury group (9 type I and 7 type II) and 10 were TAL intact group. Total LMD (5.9 mm vs 1.2 mm, p CONCLUSIONS Compared to the rule of Spence (LMD > 6.9 mm) in C1 burst fracture, total LMD > 5.9 mm (or unilateral LMD > 4.3 mm) are the radiological criteria to predict the presence of TAL injury in USSF of C1 LM, which is considered as an unstable fracture. In addition, if fracture gap more than 7 mm is considered together, the possibility of diagnostic error for TAL injury can be further reduced in USSF of C1 LM. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

“Rule of Spence” and Dickman's Classification of Transverse Atlantal Ligament Injury Revisited

A retrospective study. To evaluate the prediction accuracy of "Rule of Spence" and Dickman's classification of the transverse atlantal ligament (TAL) injury on clinical outcomes (mainly focused on atlantoaxial stability) of atlas fractures treated nonoperatively. TAL is regarded as primary stabilizer of the atlantoaxial complex. Atlas fractures are categorized as unstable and stable according to TAL injury or not. "Rule of Spence" and Dickman's classification have been widely used to evaluate the integrity of TAL indirectly or directly. However, there is controversy about how to interpret and apply these image measures appropriately in treatment decision making, and comparing the two measures in same cohort has been lack. From January 2013 to December 2015, 13 adult patients with atlas fractures, treated nonoperatively at acute posttraumatic phase and followed up for at least 2 years, were enrolled in the study. Lateral mass offset (LMO) and TAL injury were measured by radiography. Atlantoaxial stability, pain in occipital region, limitation of cervical motion, neurological dysfunction, and quality of daily life were evaluated as clinical outcomes. LMO less than 6.9 mm was inaccurate either to exclud TAL injury (4/8, 50% failed) or to predict clinical outcomes (2/8, 25% failed), whereas LMO greater than 6.9 mm was accurate to determine TAL injury (5/5, 100% succeeded) but not to predict atlantoaxial stability (4/5, 80% failed). Two cases with Dickman's classification type I injury (100%) failed to restore C1-2 stability and six of seven type II (85.7%) succeeded. Three patients were indicated for fusion surgery due to instability, and one due to traumatic arthritis. Overall clinical outcomes were satisfactory as pain and quality of life were considered. Dickman's classification of TAL injury is of higher superiority to "Rule of Spence" in term of the accuracy of predicting atlantoaxial stability of nonoperatively treated atlas fractures. 4.

Traumatic injury of the transverse atlantal ligament

Introduction. In some cases C2 may suffer only rotational dislocation around its own axis (dens), causing no increase in the atlantodental interval (ADI), making it difficult to diagnose the instability in static radiographies. Objective. To report a case of atlanto-axial traumatic subluxation, without bony injury or displacement, in which the diagnosis cannot be achieved through conventional radiology and computed tomography, and discuss the types of transverse ligament injuries, its diagnosis, the instability and their treatment. Methods.A 61-year-old man, victim of head (occipital), complaining neck. Static radiographies and CT scan of cervical spine were performed, demonstrating no abnormalities. Flexion and extension cervical radiography revealed an increase of ADI in flexion, indicating instability and damage to the transverse atlantal ligament (TAL). The MRI of the cervical spine demonstrated the discontinuity of the TAL, configuring an injury to the structure of the ligament. The patient underwent to early surgery with C1-C2 fixation using the Goel-Harms’technique. Results. The diagnosis could be revealed only in dynamic radiographs or MRI study. The patient presented complete improvement of symptoms. Conclusions. The use of cervical dynamic radiography and / or magnetic resonance imaging allowed the diagnosis of instability and visualization of the TAL injury, avoiding the lack of diagnosis with its consequences. The MRI allows a direct view of the ligament injury, their classification and the prognostic evaluation of the injury, guiding the therapy, surgical or conservative.

C1 Lateral Mass Displacement and Transverse Atlantal Ligament Failure in Jefferson's Fracture: A Biomechanical Study of the "Rule of Spence".

Jefferson's fracture, first described in 1927, represents a bursting fracture of the C1 ring with lateral displacement of the lateral masses. It has been determined that if the total lateral mass displacement (LMD) exceeds 6.9 mm, there is high likelihood of transverse atlantal ligament (TAL) rupture, and if LMD is less than 5.7 mm TAL injury is unlikely. Several recent radiographic studies have questioned the accuracy and validity of the "rule of Spence" and it lacks biomechanical support. To determine the amount of LMD necessary for TAL failure using modern biomechanical techniques. Using a universal material testing machine, cadaveric TALs were stretched laterally until failure. A high-resolution, high-speed camera was utilized to measure the displacement of the lateral masses upon TAL failure. Eleven cadaveric specimens were tested (n = 11). The average LMD upon TAL failure was 3.2 mm (±1.2 mm). The average force required to cause failure of the TAL was 242 N (±82 N). From our data analysis, if LMD exceeds 3.8 mm, there is high probability of TAL failure. Our findings suggest that although the rule of Spence is a conceptually valid measure of TAL integrity, TAL failure occurs at a significantly lower value than previously reported (P < .001). Based on our literature review and findings, LMD is not a reliable independent indicator for TAL failure and should be used as an adjunctive tool to magnetic resonance imaging rather an absolute rule.

Assessing Transverse Ligament Integrity Throught a New CT Based Alternative

Objectives The Rule of Spence for assessing integrity of the transverse atlantal ligament (TAL) suffers from poor specificity and sensitivity, frequently incorrectly reflecting the condition of the TAL. Since CT scans are quickly and easily obtained in trauma centers, we propose using a special sequence of two CT scans for more accurate diagnosis of injury to the TAL. We sought to assess the sensitivity of the CT method for TAL injury diagnosis in a laboratory setting. Materials and Methods Ten human cadaveric specimens were mounted horizontally in a supine posture with wooden inserts attached to the back of the skull to maintain neutral or slightly flexed (10°) postures. Specimens were scanned in neutral and flexed postures in four conditions: intact ( N = 10), after simulated Jefferson fracture with TAL intact ( N = 5), after TAL disruption without fracture ( N = 5), and after TAL disruption with simulated fracture ( N = 10). Atlanto-dens interval (ADI) from sagittal slices of the CT image was measured to assess anteroposterior instability of C1-C2; cross-sectional canal area was measured to assess canal encroachment caused by the flexed posture. Results In going from neutral to slight flexion, ADI increased by 0.02 mm (2.5%) in intact spines, 0.08 mm (6.25%) after Jefferson fracture without TAL disruption, 0.4 mm (34%) after TAL disruption without fracture, and 0.42mm (25%) after TAL disruption with fracture (Fig. 1). ADI increases from neutral to flexed were not significant (p &gt; 0.33, paired Student's t-test) in normal condition or with fracture.without TAL disruption. However, ADI increases were significant with TAL disruption or TAL disruption+fracture ( p &lt; 0.035). Increases in canal area were &lt; 0.8% and were not significant (p &gt; 0.74). Conclusions This study explores the possibility of utilizing two CT scans to evaluate TAL integrity. The change in ADI between these two postures was very sensitive in distinguishing TAL injury from atlas fracture. The results of this study indicate that this method should be more sensitive than the Rule of Spence for evaluating TAL integrity. By the conclusion of this session, participants should be able to identify tranverse ligament injury with a new proposed CT based method.

A retrospective review of fixation of C1 ring fractures—does the transverse atlantal ligament (TAL) really matter?

Background ContextIn contrast to the majority of outcome data, many consider C1 fractures to be benign injuries and so have advocated for conservative management, except in the case of concomitant transverse atlantal ligament (TAL) injury where C1–C2 or occiput–C2 fusions are recommended. PurposeOur goal was to evaluate a series of unstable C1 fractures treated with C1 open reduction and internal fixation (ORIF) to assess clinical and radiographic outcomes by determining the success of reduction and pain relief. Study Design/SettingThis is a retrospective cohort review. Patient SampleThe sample includes adult patients with unstable C1 fractures treated with open reduction and primary internal fixation. Outcome MeasuresPrimary outcome measures included visual analog pain scale (VAS), radiographic reduction (lateral mass displacement), maintenance of reduction, C1–C2 instability, and complications. MethodsA retrospective review of all patients with C1 fractures between September 2002 and September 2013 identified 12 consecutive patients from a level I trauma center who were treated with primary internal fixation without fusion. Electronic medical records and preoperative and postoperative radiographs were reviewed. The surgical technique consisted of a posterior cervical approach to the C1 arch and open reduction using bilateral C1 lateral mass screws connected transversely with a rod. Pre- and postoperative computed tomography scans were used to assess reduction. Long-term follow-up flexion and extension radiographs were used to assess C1–C2 stability. The authors did not receive relevant funding in relation to this research. ResultsTwelve patients underwent C1 ORIF, with a mean age of 43 (9 males and 3 females) and a mean follow-up of 17 months. Transverse atlantal ligament was found to be disrupted with type I or type II injury in 11 of the 12 patients: 5 type I and 6 type II. Preoperative lateral mass displacement averaged 7.1 mm, with postoperative displacement after reduction averaging 2.4 mm (p-value <.001). The VAS score averaged 0.7 at latest follow-up. No patients went on to develop C1–C2 instability on final flexion-extension films. No patients had a complication that resulted in neurologic deficit or vascular injury associated with the procedure. No patients were found to have late sequelae of malunion or loss of reduction. Two surgically related complications occurred, namely one patient with errant screw requiring return to the operating room (OR) and one with arthrosis of the occipital–C1 joint. ConclusionsAlthough a small series, early evidence suggests that patients with unstable C1 ring fractures can be successfully managed with primary ORIF. Open reduction and internal fixation results in a stable construct that maintains reduction, results in excellent pain control, and does not lead to C1–C2 instability. In our series, we have not observed the presence of TAL injury to adversely affect outcomes, and thus do not believe it is a contraindication to ORIF. Comparative studies comparing internal fixation with non-operative, C1–C2, or occiput–C2 fusions would yield more insight into optimal treatment options for these fractures.