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.