LAUSR

OBJECTIVE The recently described C1-C2 fixation without foramen magnum decompression (FMD) for the management of Chiari malformations (CM) has sparked a controversy. This has been claimed to be more effective than the traditionally practised FMD. However, the results after such a procedure have been less validated. Here, we assessed the efficacy of C1-C2 distraction-fusion without FMD in patients with CM without demonstrable atlantoaxial instability. METHODS Forty patients with CM underwent C1-C2 distraction and fusion (without FMD). Pre-operative and follow-up clinico-radiological data were prospectively compared using Klekamp's neurologic scale, visual analog scale (VAS), pBC2 index (ventral brainstem compression) and Vaquero index (syringomyelia). RESULTS Twenty eight patients (70%) improved in their neurological score and VAS while 8 remained in the same status, 3 deteriorated and 1 expired at follow-up. The clinical improvement did not correlate with the severity of ventral cervicomedullary compression or presence of osseous deformities (assimilated C1 arch, platybasia and basilar invagination) despite the reduction in mean pBC2 index (7.9 vs 5.9). Syringomyelia reduced in 51.7% with Vaquero Index reducing at the follow-up (0.48 vs 0.38). CONCLUSIONS The overall results after C1-C2 distraction-fusion for CM without instability are not exceptionally better, and appear to be similar to reported outcomes following FMD. The neurological improvement seen in some patients is possibly due to indirect ventral decompression (due to distraction of C1-2) rather than the stabilization itself. The presence of bony anomalies such as assimilated C1 arch, platybasia, BI and ventral brainstem compression did not significantly influence the outcome.