Orthopedic Surgical Procedures
The peroneal nerve — particularly the common peroneal nerve at the fibular head — is the most frequently injured nerve in total knee replacement, and injury often presents postoperatively as foot drop. Free-run EMG monitoring of the tibialis anterior, extensor hallucis longus, and medial gastrocnemius provides continuous, sensitive detection of peroneal and tibial nerve irritation throughout the procedure. SSEPs and tcMEPs supplement EMG by monitoring for peripheral ischemia — including blood clot formation or arterial compromise — which produces rapid, detectable waveform changes. EMG monitoring of the vastus lateralis and medialis is also included to guard against femoral nerve injury during approach.
The sciatic nerve — and the peroneal division in particular — is the nerve most commonly injured in total hip arthroplasty, with risk elevated significantly in revision procedures and cases requiring limb lengthening of more than one inch. Foot drop from peroneal nerve injury and the inability to maintain knee extension from femoral nerve palsy are the most clinically significant potential deficits. Free-run EMG monitoring of tibialis anterior, extensor hallucis longus, and dorsiflexor muscle groups provides real-time detection of sciatic and peroneal nerve irritation, while SSEPs and tcMEPs monitor for both ischemic and mechanical compromise of the femoral and sciatic nerve distributions.
Nerve injury is a recognized complication of total shoulder arthroplasty (TSA), with published rates of intraoperative signal change ranging from 1–33% depending on monitoring sensitivity. The median nerve in the operative arm is the most frequently affected structure, followed by the ulnar and radial nerves, with traction during joint preparation and exposure being the primary mechanism of injury.
Upper extremity SSEPs — targeting median nerve primarily, with ulnar and radial nerve monitoring available — provide continuous sensory pathway assessment throughout the procedure. tcMEPs are used in conjunction to detect mechanical motor pathway compromise from traction or retraction. Published evidence supports that intraoperative SEP signal changes, while common, are largely reversible when detected promptly and do not reliably predict postoperative neurological deficit — supporting the value of continuous monitoring as an early warning system.
The ulnar nerve is the primary structure at risk during total elbow replacement and related procedures, particularly during joint dislocation required for implant preparation via the lateral approach. Evidence demonstrates that CMAP amplitude reduction in the abductor digiti minimi is detectable during elbow dislocation and correlates with ulnar nerve stress — changes that resolve promptly when the elbow is relocated.
Free-run EMG monitoring detects ulnar nerve irritation in real time throughout the procedure. SSEPs from ulnar, radial, and median nerve stimulation provide complementary sensory pathway assessment. Frequent relocation of the dislocated elbow is supported by the evidence as an important protective measure — and IONM provides the objective feedback needed to guide that timing decision intraoperatively.
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
Neuromonitoring for Orthopedic Procedures
Orthopedic procedures involving major joint replacement and extremity surgery carry meaningful risk of peripheral nerve injury from a variety of mechanisms: traction during positioning or retraction, compression from retractors or implants, thermal injury, or ischemia from vascular compromise. IONM allows continuous assessment of peripheral nerve integrity throughout the procedure, providing immediate feedback when neural stress is detected so the surgical team can intervene before deficits become permanent.
Total Knees Replacement
Total Hips Replacement
Total Shoulder Arthroplasty
Elbow Surgery
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.
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.
Why Utilize IONM During Elbow Surgery?
Intraoperative monitoring of ulnar nerve function during replacement of the rheumatoid elbow via the lateral approach.
