intraoperative neurophysiologic monitoring for sacroiliac fusion hallie loy bs cnim
TRANSCRIPT
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
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.