INTRAOPERATIVE

NEUROPHYSIOLO

GIC

MONITORING FO

R

SACROILIAC FU

SION

H A L L I E L

O Y BS C

N 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 FUSION VIDEO

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 L2/3Hip extension L4/5Hip adduction L2/3Hip abduction L4/5Knee extension L3/4Knee flexion L5/S1Ankle Dorsiflexion L4/5Great toe extension L5Ankle plantarflexion S1/2

Lower Limbs MyotomesLower Limb

Dermatomes

HOW DO WE MONITO

R SI

FUSIONS? SSEP

EMG SE-EMG

SSEPStimulation:Uppers: Ulnar

NerveLowers:

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

30 250-1000 0.5-5 17-23 20-35 0.2-0.5 1.3-

4.7

SEP mediannerve subcortical

30 500-1000 0.5-3 11-16 20-35 0.2-0.5 1.3-

4.7

SEP tibialnerve cortical

30 250-1000 0.5-5 35-45 25-50 0.2-1 1.3-

4.7

SEP tibialnerve subcortical

30 500-1000 0-3 27-35 25-50 0.2-1 1.3-

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.