Posterior Exposure of C1-C2 for Instrumentation and Fusion.

Abstract

Posterior C1-C2 instrumentation and fusion is a well-established technique for the treatment of atlantoaxial instability. Safe posterior exposure is critically important because of the proximity of the vertebral artery, venous plexus, and C2 dorsal root ganglion. However, practical exposure nuances and safety pearls are often underemphasized. The present video article demonstrates a stepwise approach for posterior exposure for C1-C2 instrumentation and fusion. Preoperative assessment includes dynamic flexion-extension radiographs to evaluate instability and reducibility, and computed tomography (CT) angiography to identify a high-riding vertebral artery or vascular anomalies. The patient is positioned prone with the head secured in a Mayfield clamp (or a horseshoe headrest). A midline posterior incision and subperiosteal dissection are performed to expose the posterior elements of C1 and C2. Key technical steps include careful management of the venous plexus, identification and preservation of the C2 dorsal root ganglion, exposure of the C1 lateral mass and C2 pars interarticularis, and controlled atlantoaxial joint mobilization to achieve reduction. Screws are placed in the C1 lateral mass and C2 pars interarticularis under fluoroscopic guidance, followed by rod placement, decortication, and bone grafting to achieve fusion. Nonoperative treatment options include cervical immobilization and pharmacologic intervention. Surgical alternatives include other posterior fixation techniques, wiring constructs, or anterior approaches in select cases. Meticulous posterior exposure with attention to venous plexus control and ganglion preservation allows safe and reproducible C1-C2 instrumentation while minimizing the risk of neurovascular complications. Patients are counseled that posterior C1-C2 instrumentation and fusion is intended to provide stable fixation of the atlantoaxial complex, relieve pain related to instability, prevent progressive neurological compromise, and achieve a high rate of solid fusion. Previous studies have demonstrated reliable fusion, significant improvement in neck pain, and durable radiographic stability following posterior C1-C2 fixation with use of screw-rod constructs. Harms and Melcher² reported high rates of fusion with maintained alignment and low rates of hardware failure with use of posterior C1 lateral mass and C2 screw fixation. Goel and Laheri³ similarly demonstrated effective stabilization and neurological improvement following posterior atlantoaxial fixation. Contemporary reviews have confirmed that modern posterior fixation techniques provide predictable clinical and radiographic outcomes with acceptable complication rates when meticulous surgical technique and appropriate preoperative planning are employed. Obtain dynamic flexion-extension radiographs preoperatively to assess atlantoaxial instability and reducibility; reduction seen on extension helps guide intraoperative positioning.Perform routine CT angiography to identify a high-riding vertebral artery or aberrant vascular anatomy that may alter screw trajectory.Secure the head in a Mayfield clamp and maintain neutral or slight extension; avoid excessive rotation during positioning.Use a strict midline, subperiosteal dissection to minimize muscle trauma and reduce venous bleeding.Anticipate and carefully control the venous plexus around C1-C2 with use of gentle bipolar coagulation and hemostatic agents; avoid blind cauterization.Identify and preserve the C2 dorsal root ganglion; minimize prolonged or forceful retraction to reduce postoperative occipital neuralgia.Clearly define osseous landmarks before instrumentation, particularly the C1 lateral mass and C2 pars interarticularis.Perform gentle atlantoaxial joint mobilization to achieve reduction prior to definitive screw placement.Confirm screw trajectories with fluoroscopy before drilling and final screw insertion to avoid vertebral artery injury.Thoroughly decorticate posterior elements and apply adequate bone graft to optimize fusion. C1 = first cervical vertebra (atlas)C2 = second cervical vertebra (axis)CTA = computed tomography angiographyDRG = dorsal root ganglion.