Orthopedic Surgical Procedures

Somatosensory Evoked potenial 

Transcranial Evoked Potential 

Free running EMG 

Triggered EMG 

Train of four

Somatosensory Evoked potenial 

Transcranial Evoked Potential 

Free running EMG

Triggered EMG 

Train of four

Free running EMG 

Triggered EMG 

Train of four

Somatosensory Evoked potenial 

Transcranial Evoked Potential

Free running EMG 

Triggered EMG 

Train of four

Somatosensory Evoked potenial 

Free running EMG- Useful for identification of nerve and nerve irritation

Triggered EMG- Useful for identification of nerve 

SSEP- Provide real time assessment of the ascending pathway of the spinal cord

TcMEP- Provides real time assessment of the descending pathway of the spinal cord

Train of four- Provides proof of adequate or lack of proof of neuromuscular blockade

Orthopedic Surgical Procedures and Neuromonitoring

Total Knees Replacement

Total Hips Replacement

Total Shoulder Arthroplasty

Elbow

To aid in Nerve preservation

Protect motor and sensory pathway

Why Utilize IONM During Total Knee Replacement?

Continuous EMG: Detects nerve irritation. 

SSEPs/TcMEPs: Monitors nerve function.

SSEPs/TcMEPs: Blood clots can lead to peripheral ischemia that is 

easily detectable

SSEPs/TcMEPs: Peripheral ischemia is detectable because it directly leads to the loss of nerve function

EMG monitoring of Tibialis Anterior, Extensor , Hallucis Longus and Medial Gastrocnemius 

EMG monitoring of Dorsiflexor muscle, Tibialis anterior and Extensor hallucis longus SSEP and TcMEP is also utilized to verify the integrity of the sensory and motor pathway respectively

EMG monitoring of Vastus Lateralis and Medialis 

Any incision can result in damage to the sensory nerves in the area of the incision. Significant nerve damage, which may  cause loss of muscle function, can occur after hip replacement. This type of injury is rare and is most common when the leg  is lengthened more than one inch (such as in surgery for congenital hip deformity or revision total hip replacement). Nerve injuries of this type can lead to a ‘foot drop’ or the inability to raise the ankle or toe, in case of damage  to the Ischial Nerve. In case of palsy of the Femoral Nerve, there will be inability to keep the leg extended during gait. Most  palsies recover spontaneously. In case of an sciatic nerve problem, recovery is less common. It can take 2 years to be able to  see any recovery...”

http://www.hip-clinic.com/en/hip-info/treatment/total-hip-replacement?start=5 

Complications of Total Knee Replacement:

Patient position or retraction

Blood Clot

Arterial Injury

Sciatic Nerve

Femoral Nerve

Ischail Nerve

To aid in Nerve preservation

Protect motor and sensory pathway 

SSEPs are utilized to target the median nerve primarily. However, the ulnar and Radial nerve can also  be monitored

TcMEPs are utilized in conjunction to SSEPs to detect mechanical damage resulting from traction to  any given part of the motor pathway. 

Atif A Malick, Nick Aresti, Karen Plumb, Joseph Cowan, Deborah Higgs, Simon Lambar, Mark Falwort

Nerve injury is an acknowledged complication of total shoulder arthroplasty (TSA). Although the incidence of postoperative  neurological deficit has been reported to be between 1% and 16%, the true incidence of nerve damage is considered to be  higher. The present study aimed to identify the rate of intra-operative nerve injury during total shoulder arthroplasty and to  determine potential risk factors.

Seven (33%) patients had a SEP signal change. The only significant risk factor identified for signal change was male sex  (odds ratio 15.00, 95% confidence interval). The median nerve was the most affected nerve in the operated arm. All but one  signal change returned to normal before completion of the operation and no patient had a persisting postoperative clinical  neurological deficit. 

The incidence of intra-operative nerve damage may be more common than previously reported. However, the loss of SEP 

signal is reversible and does not correlate with persisting clinical neurological deficits. 

The median nerve appears to be most at risk. Monitoring SEPs in the operated limb during TSA may be a valuable tool  during TSA. 

http://sel.sagepub.com/content/6/2/90.abstract 

A prospective study of nerve conduction in 21 patients who underwent primary or revision TSA was carried out over a 12- month period. Nerve conduction was monitored by measuring intra-operative sensory evoked potentials (SEP). A significant  neurophysiological signal change was defined as either a unilateral or bilateral decrease in SEP signal of ≥50%, a latency  increase of ≥10% or a change in waveform morphology, not caused by operative or anaesthetic technique.

Why Utilize IONM During Total Shoulder Arthroplasty?

Intraoperative nerve monitoring during total shoulder arthroplasty surgery

Background

Methods

Results

Conclusion

To aid in Nerve preservation

Protect motor and sensory pathway 

EMG to detect nerve irritation and for nerve identification. 

SSEP to detect changes in sensory via the ulnar, radial and median nerves.

Ljung P, Ahlmann S, Knutson K, Rosén I, Rydholm U.

Neurography of the ulnar nerve was performed pre-, intra-and postoperatively in 8 arms of 7 patients with rheumatoid  arthritis operated on with total elbow replacement via the lateral approach. Ulnar nerve decompression was performed in 4  elbows before implantation. A reduction in the amplitude of compound muscle action potential (CMAP) recorded from the  abductor digiti minimi on stimulation of the ulnar nerve in the axilla, was observed during elbow dislocation at surgery in all patients,  in 5 cases transiently and in 3 cases until the end of surgery. The ulnar nerve had been decompressed in all patients with  lasting amplitude reduction. One of them had a mild sensory ulnar nerve palsy, while the other 2 had normal nerve function  at the 

postoperative clinical examination. All 3 had a reduction in the amplitude of compound sensory nerve action potential  (SNAP) and 2 of them also in CMAP amplitude at the postoperative neurographic examination. In patients with transient  reduction during surgery, the CMAP amplitude quickly normalized on relocation of the elbow and both the SNAP and the  CMAP were preserved at the postoperative neurographic examination. 

The authors conclude that dislocation of the laterally approached elbow carries a risk of ulnar nerve injury, which is not  prevented by decompression of the ulnar nerve, but frequent relocation of the elbow during surgery seems important. It is suggested that the ulnar nerve should not be decompressed routinely, and that the 

dislocated elbow should be frequently relocated. 

http://www.ncbi.nlm.nih.gov/pubmed/7740942

Why Utilize IONM During Elbow Surgery?

Intraoperative monitoring of ulnar nerve function during replacement of the  rheumatoid elbow via the lateral approach.