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Intraoperative Neurophysiologic Monitoring for Sacroiliac Fusion. Hallie Loy bs CNIM. Anatomy of the Pelvis. Typical SI Fusion Patient…. Symptoms:. Low back pain Buttock and hip pain Ipsilateral LE weakness LE numbness and tingling Trouble sleeping Leg instability Problems sitting.
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Intraoperative Neurophysiologic Monitoring for Sacroiliac Fusion HallieLoy bs CNIM
Typical SI Fusion Patient… Symptoms: • Low back pain • Buttock and hip pain • Ipsilateral LE weakness • LE numbness and tingling • Trouble sleeping • Leg instability • Problems sitting
SI joint as a cause of pain: • 25% of all low back pain is caused by Sacroiliac joint disease. • The incidence of SI joint degeneration in post-lumbar fusion surgery is 75% at 5 years post-op. • SI joint is a pain generator in low back pain of 43% post- lumbar and lumbar-sacral fusion patients.
Diagnosis… • Clinical tests • Imaging studies (x-ray. CT scan, MRI) • SI joint injections of a local anesthetic
Other treatment options • Physical therapy • Chiropractic manipulations • Pain medication • Injection therapy
Iatrogenic nerve injury rates have been reported to be as low as 1% and as high as 18%.
Lower Limb Dermatomes Lower Limbs Myotomes
How do we monitor si fusions? • SSEP • EMG • SE-EMG
ssep • Stimulation: • Uppers: Ulnar Nerve • Lowers: Posterior Tibila Nerve
ssep • Alarm Criteria: • Amplitude decrease of 50% • Latency increase of 10%
Patient had LUE amplitude decrease of greater than 50% due to a positional issue.
emg • Needle electrodes used in the following muscles: • L5- Tibialis Anterior • S1- Gastrocnemius • S2- Anal Sphincter
Free run EMG • Alarm Criteria: • Any burst/firing from nerves on the side the surgeon is working.
SE-emg • Stimulation probe used to stimulate either the guide wire/pin or the drill bit to insure a safe distance between the drill bit and the neural structures.
Se-emg • Alarm Criteria: • Response <8 mA with an absolute minimum of 6 mA
In the case of nerve injury • LE numbness • LE weakness • Incontinence • Foot drop
References • "Minimally Invasive Sacroiliac Joint Surgery." MIS Sacroiliac Joint Fusion Surgery. SI-BONE, n.d. Web. 08 Apr. 2013. • Moed, B.R. (2008). Monitoring neural function during pelvic surgery. In M.R. Nuwer (Ed.), Intraoperative Monitoring of Neural Function Handbook of Clinical Neurophysiology (vol. 8, pp. 752-763). Elsevier B. V. • Moore MD, M.R. (2012, January ). The Sacroiliac Joint: A Forgotten Pain Generator. The SI-BONE Sentinel, 1-2.