INTR

AOPERAT

IVE

NEUROPHYS

IOLO

GIC

MONITORIN

G FOR

SACROILIAC F

USION

HA

L L I E L

OY

BS

CN

I M

ANATOMY OF THE PELVIS

TYPICAL SI FUSION PATIENT…

S Y M P T O M S :

• 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.

• Clinical tests• Imaging studies

(x-ray. CT scan, MRI)

• SI joint injections of a local anesthetic

DIAGNOSIS…

• Physical therapy

• Chiropractic manipulations

• Pain medication

• Injection therapy

OTHER TREATMENT OPTIONS

SI FUSION SURGERY

                                                                                     

SI FUSIO

N VID

EO

WHY DO WE MONITOR SI FUSIONS?

IATROGENIC NERVE INJURY RATES HAVE BEEN REPORTED TO BE AS LOW AS 1% AND AS HIGH AS 18%.

Movement Nerve Root Segments

Hip flexion L2/3

Hip extension L4/5

Hip adduction L2/3

Hip abduction L4/5

Knee extension L3/4

Knee flexion L5/S1

Ankle Dorsiflexion L4/5

Great toe extension L5

Ankle plantarflexion S1/2

Lower Limbs Myotomes

Lower Limb Dermatomes

HOW D

O WE M

ONITOR S

I

FUSIO

NS? SSEP EMG SE-EMG

SSEPStimulation:

Uppers: Ulnar Nerve

Lowers: Posterior Tibila Nerve

  Low FreqFilter (Hz)

High FreqFilter (Hz)

Amp

(μV)

Typical latencies

(ms)

Stim.Intensity

(mA)

StimDuration

(ms)

Stim.Rate (Hz)

SEP mediannerve cortical

30 250-10000.5-

517-23 20-35 0.2-0.5

1.3-4.7

SEP mediannerve subcortical

30 500-10000.5-

311-16 20-35 0.2-0.5

1.3-4.7

SEP tibialnerve cortical

30 250-10000.5-

535-45 25-50 0.2-1

1.3-4.7

SEP tibialnerve subcortical

30500-1000

0-3 27-35 25-50 0.2-11.3-4.7

Alarm Criteria:- Amplitude

decrease of 50%

- Latency increase of 10%

SSEP

EXAMPLES OF CHANGES

Patient had LUE amplitude decrease of greater than 50% due to a positional issue.

Needle electrodes used in the following muscles:

• L5- Tibialis Anterior

• S1- Gastrocnemius

• S2- Anal Sphincter

EMG

Alarm Criteria:• Any

burst/firing from nerves on the side the surgeon is working.

FREE RUN 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

SE-EMG

• LE numbness

• LE weakness• Incontinenc

e• Foot drop

IN THE CASE OF NERVE INJURY

QUESTIONS?

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.